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AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #1750 on: July 24, 2017, 06:54:15 PM »
The linked reference indicates that increasing tropospheric ozone decreases our carbon budget:

Bin Wang, Herman H Shugart and Manuel T Lerdau (21 July 2017), "Sensitivity of global greenhouse gas budgets to tropospheric ozone pollution mediated by the biosphere:, Environmental Research Letters, Volume 12, Number 8

http://iopscience.iop.org/article/10.1088/1748-9326/aa7885/meta?utm_content=bufferbfe30&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "Tropospheric ozone (O3), a harmful secondary air pollutant, can affect the climate via direct radiative forcing and by modifying the radiative forcing of aerosols through its role as an atmospheric oxidant. Moreover, O3 exerts a strong oxidative pressure on the biosphere and indirectly influences the climate by altering the materials and energy exchange between terrestrial ecosystems and the atmosphere. However, the magnitude by which O3 affects the global budgets of greenhouse gases (GHGs: CO2, CH4, and N2O) through altering the land–atmosphere exchange is largely unknown. Here we assess the sensitivity of these budgets to tropospheric O3 pollution based on a meta-analysis of experimental studies on the effects of elevated O3 on GHG exchange between terrestrial ecosystems and the atmosphere. We show that across ecosystems, elevated O3 suppresses N2O emissions and both CH4 emissions and uptake, and has little impact on stimulation of soil CO2 emissions except at relatively high concentrations. Therefore, the soil system would be transformed from a sink into a source of GHGs with O3 levels increasing. The global atmospheric budget of GHGs is sensitive to O3 pollution largely because of the carbon dioxide accumulation resulting from suppressed vegetation carbon uptake; the negative contributions from suppressed CH4 and N2O emissions can offset only ~10% of CO2 emissions from the soil–vegetation system. Based on empirical data, this work, though with uncertainties, provides the first assessment of sensitivity of global budgets of GHGs to O3 pollution, representing a necessary step towards fully understanding and evaluating O3–climate feedbacks mediated by the biosphere."

Extract: "By fully accounting for the three gases simultaneously, we find that with the O3 level continuously increasing the whole soil system would be transformed from a sink into a source of GHGs. With an increase of O3 concentration by 10 ppb, the global annual net atmospheric budgets would on average increase by ~12% (i.e. ~5 PgC yr−1)."

 
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AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #1751 on: July 25, 2017, 02:08:41 PM »
One big problem is that climate change is complex, so scientists like Mann can appear reasonable by pointing out that our carbon budget for achieving the Paris goals are as much as 40% lower than assumed in 2015; when in reality such estimates also ignore the very real risk that ECS is significantly higher than assumed in 2015 (not to mention Hansen's ice-climate feedback).

Andrew P. Schurer, Michael E. Mann, Ed Hawkins, Simon F. B. Tett & Gabriele C. Hegerl (2017), "Importance of the pre-industrial baseline for likelihood of exceeding Paris goals", Nature Climate Change; doi:10.1038/nclimate3345

http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate3345.html?foxtrotcallback=true

Abstract: "During the Paris conference in 2015, nations of the world strengthened the United Nations Framework Convention on Climate Change by agreeing to holding ‘the increase in the global average temperature to well below 2 °C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5 °C’ (ref. 1). However, ‘pre-industrial’ was not defined. Here we investigate the implications of different choices of the pre-industrial baseline on the likelihood of exceeding these two temperature thresholds. We find that for the strongest mitigation scenario RCP2.6 and a medium scenario RCP4.5, the probability of exceeding the thresholds and timing of exceedance is highly dependent on the pre-industrial baseline; for example, the probability of crossing 1.5 °C by the end of the century under RCP2.6 varies from 61% to 88% depending on how the baseline is defined. In contrast, in the scenario with no mitigation, RCP8.5, both thresholds will almost certainly be exceeded by the middle of the century with the definition of the pre-industrial baseline of less importance. Allowable carbon emissions for threshold stabilization are similarly highly dependent on the pre-industrial baseline. For stabilization at 2 °C, allowable emissions decrease by as much as 40% when earlier than nineteenth-century climates are considered as a baseline."
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Archimid

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Re: Conservative Scientists & its Consequences
« Reply #1752 on: July 25, 2017, 02:48:25 PM »
Mann and mainstream science assume that civilization is the default state of the world. They also assume humans are inherently different and apart from the rest of nature. That's why they can hold in their minds massive extinctions for the world while humanity suffers from linear and insignificant harm.

I don't think that is scientific at all. Modern civilization  has existed for only a few generations.  This whole thing is just an experiment that could fail at anytime. That's what the science and history indicates. Civilizations fail, animals go extinct. To survive this we will have to wrestle nature into submission.

I am an energy reservoir seemingly intent on lowering entropy for self preservation.

rboyd

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Re: Conservative Scientists & its Consequences
« Reply #1753 on: July 25, 2017, 05:44:46 PM »
To survive this we will have to wrestle nature into submission.

Exactly the attitude that I worry that our elites will take, down that path is massive geo-engineering. The Earth will win any such battle, our level of understanding through Earth System Science is still far too simplistic for us to think that we can manage the Earth.

Another path is humility - to accept that we have to limit ourselves so that the Earth will continue to provide us with an amenable environment.

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Re: Conservative Scientists & its Consequences
« Reply #1754 on: July 25, 2017, 06:31:22 PM »
rboyd, at this point I believe geoengineering is inevitable. It is scary for sure, but no more so than climate change.
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Re: Conservative Scientists & its Consequences
« Reply #1755 on: July 25, 2017, 06:38:46 PM »
I just realized I posted this in the wrong thread. It was meant for the Climate porn vs alarmism. I'm going to re-post it there. If anyone reply I'll answer there. My apologies to the gods that be.
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rboyd

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Re: Conservative Scientists & its Consequences
« Reply #1756 on: July 26, 2017, 06:13:29 AM »
rboyd, at this point I believe geoengineering is inevitable. It is scary for sure, but no more so than climate change.

I have to agree, the only logical outcome given the current lack of action and inability to give up the growth paradigm.

AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #1757 on: July 26, 2017, 02:35:54 PM »
The linked Scribbler article discusses research indicating that carbon emissions from permafrost degradation will be more active than previously considered in CMIP5/AR5:

Title: "More Fire and Anthrax for the Arctic: Study Finds 21 to 25 Percent of Northern Permafrost Will Thaw at Just 1.5 C of Warming"

https://robertscribbler.com/2017/07/25/more-fire-and-anthrax-for-the-arctic-study-finds-21-to-25-percent-of-northern-permafrost-will-thaw-at-just-1-5-c-of-warming/

Extract: "A risk of serious carbon feedbacks that accelerate rates of warming this Century and over the longer term is not inconsiderable even with a 24 percent loss of Permafrost under the best case scenario identified by this study. However, the likelihood of a much more serious feedback under continued fossil fuel burning is far more apparent."
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jai mitchell

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Re: Conservative Scientists & its Consequences
« Reply #1758 on: July 26, 2017, 07:08:32 PM »

Andrew P. Schurer, Michael E. Mann, Ed Hawkins, Simon F. B. Tett & Gabriele C. Hegerl (2017), "Importance of the pre-industrial baseline for likelihood of exceeding Paris goals", Nature Climate Change; doi:10.1038/nclimate3345


To me this is the potential for further validation of the >4.5 ECS argument.  Earlier warming due to CO2 at much smaller rates of increases/production of CO2 indicates a much higher sensitivity with unknown or underappreciated negative feedbacks like Albedo.
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AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #1759 on: July 27, 2017, 05:11:22 AM »

Andrew P. Schurer, Michael E. Mann, Ed Hawkins, Simon F. B. Tett & Gabriele C. Hegerl (2017), "Importance of the pre-industrial baseline for likelihood of exceeding Paris goals", Nature Climate Change; doi:10.1038/nclimate3345



To me this is the potential for further validation of the >4.5 ECS argument.  Earlier warming due to CO2 at much smaller rates of increases/production of CO2 indicates a much higher sensitivity with unknown or underappreciated negative feedbacks like Albedo.


Further to you point (which I agree with) here is an article on the Cristian Proistosescu and Peter J. Huybers (2017) paper:

Titled: “Scientists are starting to clear up one of the biggest controversies in climate science “

https://www.washingtonpost.com/news/energy-environment/wp/2017/07/05/scientists-are-starting-to-clear-up-one-of-the-biggest-controversies-in-climate-science/?utm_term=.012567d68486


Extract: “The new study helps reconcile the models with the historical record. It suggests global warming occurs in different phases or “modes” throughout the planet, some of which happen more quickly than others. Certain slow-developing climate processes could amplify warming to a greater extent in the future, putting the models in the right after all. But these processes take time, even up to several hundred years, to really take effect — and because not enough time has passed since the Industrial Revolution for their signal to really develop, the historical record is what’s actually misleading at the moment.

This conclusion is supported by a growing body of research, which suggests that warming estimates made from the historical record alone are “potentially biased low, for reasons we are now just beginning to understand,” said Timothy Andrews, a climate scientist with the Met Office, the United Kingdom’s national weather service, in an email to The Washington Post."

Cristian Proistosescu and Peter J. Huybers (5 July 2017), "Slow climate mode reconciles historical and model-based estimates of climate sensitivity", Sci. Adv. 3, e1602821,
DOI: 10.1126/sciadv.1602821

http://advances.sciencemag.org/content/advances/suppl/2017/06/29/3.7.e1602821.DC1/1602821_SM.pdf
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Csnavywx

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Re: Conservative Scientists & its Consequences
« Reply #1760 on: July 27, 2017, 09:31:08 PM »
One big problem is that climate change is complex, so scientists like Mann can appear reasonable by pointing out that our carbon budget for achieving the Paris goals are as much as 40% lower than assumed in 2015; when in reality such estimates also ignore the very real risk that ECS is significantly higher than assumed in 2015 (not to mention Hansen's ice-climate feedback).

Andrew P. Schurer, Michael E. Mann, Ed Hawkins, Simon F. B. Tett & Gabriele C. Hegerl (2017), "Importance of the pre-industrial baseline for likelihood of exceeding Paris goals", Nature Climate Change; doi:10.1038/nclimate3345

http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate3345.html?foxtrotcallback=true

Abstract: "During the Paris conference in 2015, nations of the world strengthened the United Nations Framework Convention on Climate Change by agreeing to holding ‘the increase in the global average temperature to well below 2 °C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5 °C’ (ref. 1). However, ‘pre-industrial’ was not defined. Here we investigate the implications of different choices of the pre-industrial baseline on the likelihood of exceeding these two temperature thresholds. We find that for the strongest mitigation scenario RCP2.6 and a medium scenario RCP4.5, the probability of exceeding the thresholds and timing of exceedance is highly dependent on the pre-industrial baseline; for example, the probability of crossing 1.5 °C by the end of the century under RCP2.6 varies from 61% to 88% depending on how the baseline is defined. In contrast, in the scenario with no mitigation, RCP8.5, both thresholds will almost certainly be exceeded by the middle of the century with the definition of the pre-industrial baseline of less importance. Allowable carbon emissions for threshold stabilization are similarly highly dependent on the pre-industrial baseline. For stabilization at 2 °C, allowable emissions decrease by as much as 40% when earlier than nineteenth-century climates are considered as a baseline."


Baffling that we are still wasting ink on this. R2.6 and 1.5C aren't happening. Period. End of story. Chance = 100%. Pretending otherwise at this point is posturing and/or mathurbation.

AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #1761 on: July 27, 2017, 11:33:40 PM »
The linked reference indicates that the important feedback mechanism of GHG emissions form wetland anaerobic peat decomposition is sensitive to the rate of warming; where faster rates of warming results in an increase in effective ECS this century:

Debjani Sihi, Patrick W. Inglett, Stefan Gerber and Kanika Sharma Inglett (26 July 2017), "Rate of warming affects temperature sensitivity of anaerobic peat decomposition and greenhouse gas production", Global Change Biology, DOI: 10.1111/gcb.13839 

http://onlinelibrary.wiley.com/doi/10.1111/gcb.13839/abstract?utm_content=buffer22bfd&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Extract: "Temperature sensitivity of anaerobic carbon mineralization in wetlands remains poorly represented in most climate models and is especially unconstrained for warmer subtropical and tropical systems which account for a large proportion of global methane emissions. Several studies of experimental warming have documented thermal acclimation of soil respiration involving adjustments in microbial physiology or carbon use efficiency (CUE), with an initial decline in CUE with warming followed by a partial recovery in CUE at a later stage. The variable CUE implies that the rate of warming may impact microbial acclimation and the rate of carbon-dioxide (CO2) and methane (CH4) production. Here, we assessed the effects of warming rate on the decomposition of subtropical peats, by applying either a large single-step (10°C within a day) or a slow ramping (0.1°C day−1 for 100 days) temperature increase. The extent of thermal acclimation was tested by monitoring CO2 and CH4 production, CUE, and microbial biomass. Total gaseous C loss, CUE, and MBC were greater in the slow (ramp) warming treatment. However, greater values of CH4-C:CO2-C ratios lead to a greater global warming potential in the fast (step) warming treatment. The effect of gradual warming on decomposition was more pronounced in recalcitrant and nutrient-limited soils. Stable carbon isotopes of CH4 and CO2 further indicated the possibility of different carbon processing pathways under the contrasting warming rates. Different responses in fast versus slow warming treatment combined with different endpoints may indicate alternate pathways with long-term consequences. Incorporations of experimental results into organic matter decomposition models suggest that parameter uncertainties in CUE and CH4-C:CO2-C ratios have a larger impact on long-term soil organic carbon and global warming potential than uncertainty in model structure, and shows that particular rates of warming are central to understand the response of wetland soils to global climate change."
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AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #1762 on: July 30, 2017, 01:51:50 AM »
As a follow-on to my immediate prior post, the linked reference indicates that tropical peatlands are likely three times larger than previously recognized.  Peatlands currently represent a net carbon sink, but continuing global warming and Anthropogenic activities (like agriculture & deforesting) could change these net carbon sinks into net carbon sources, that are largely unaccounted for in CMIP5/AR5:

Thomas Gumbricht, Rosa Maria Roman-Cuesta, Louis Verchot, Martin Herold, Florian Wittmann, Ethan Householder, Nadine Herold & Daniel Murdiyarso (9 May 2017), "An expert system model for mapping tropical wetlands and peatlands reveals South America as the largest contributor", Global Change Biology, DOI: 10.1111/gcb.13689

http://onlinelibrary.wiley.com/doi/10.1111/gcb.13689/abstract

Abstract: "Wetlands are important providers of ecosystem services and key regulators of climate change. They positively contribute to global warming through their greenhouse gas emissions, and negatively through the accumulation of organic material in histosols, particularly in peatlands. Our understanding of wetlands’ services is currently constrained by limited knowledge on their distribution, extent, volume, interannual flood variability and disturbance levels. We present an expert system approach to estimate wetland and peatland areas, depths and volumes, which relies on three biophysical indices related to wetland and peat formation: (1) long-term water supply exceeding atmospheric water demand; (2) annually or seasonally water-logged soils; and (3) a geomorphological position where water is supplied and retained. Tropical and subtropical wetlands estimates reach 4.7 million km2 (Mkm2). In line with current understanding, the American continent is the major contributor (45%), and Brazil, with its Amazonian interfluvial region, contains the largest tropical wetland area (800,720 km2). Our model suggests, however, unprecedented extents and volumes of peatland in the tropics (1.7 Mkm2 and 7,268 (6,076–7,368) km3), which more than threefold current estimates. Unlike current understanding, our estimates suggest that South America and not Asia contributes the most to tropical peatland area and volume (ca. 44% for both) partly related to some yet unaccounted extended deep deposits but mainly to extended but shallow peat in the Amazon Basin. Brazil leads the peatland area and volume contribution. Asia hosts 38% of both tropical peat area and volume with Indonesia as the main regional contributor and still the holder of the deepest and most extended peat areas in the tropics. Africa hosts more peat than previously reported but climatic and topographic contexts leave it as the least peat-forming continent. Our results suggest large biases in our current understanding of the distribution, area and volumes of tropical peat and their continental contributions."

See also:

Title: “Ultimate bogs: how saving peatlands could help save the planet”

https://www.theguardian.com/environment/2017/jul/28/ultimate-bogs-how-saving-peatlands-could-help-save-the-planet

&

Title: “Peatlands, already dwindling, could face further losses”

https://phys.org/news/2017-06-peatlands-dwindling-losses.html

« Last Edit: July 30, 2017, 07:16:19 PM by AbruptSLR »
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logicmanPatrick

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Re: Conservative Scientists & its Consequences
« Reply #1763 on: July 30, 2017, 05:31:32 AM »
AbruptSLR - I am too tired at the moment to wade through 36 pages of this so you may be ahead of me.

Have you considered reading papers on biogas generation?  I am experimenting with a small digester at the moment.  The rate of methane generation in the lab, as in the wild, depends on solid/liquid ratios and temperature more than any other factor.  The type of biomass makes a difference but temperature is king.

My point: scientists should not be reticent in reporting that higher temperatures in wetlands are virtually certain to lead to higher methane emissions.  And if it gets too hot for the mesophiles, the thermophiles will take over, but by then we humans might not be around to notice.
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AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #1764 on: July 30, 2017, 05:45:09 AM »
AbruptSLR - I am too tired at the moment to wade through 36 pages of this so you may be ahead of me.

Have you considered reading papers on biogas generation?  I am experimenting with a small digester at the moment.  The rate of methane generation in the lab, as in the wild, depends on solid/liquid ratios and temperature more than any other factor.  The type of biomass makes a difference but temperature is king.

My point: scientists should not be reticent in reporting that higher temperatures in wetlands are virtually certain to lead to higher methane emissions.  And if it gets too hot for the mesophiles, the thermophiles will take over, but by then we humans might not be around to notice.


Patrick,

I am not sure which research you are referring to, but the linked reference agrees with your conclusion:

Debjani Sihi, Patrick W. Inglett, Stefan Gerber and Kanika Sharma Inglett (26 July 2017), "Rate of warming affects temperature sensitivity of anaerobic peat decomposition and greenhouse gas production", Global Change Biology, DOI: 10.1111/gcb.13839 

http://onlinelibrary.wiley.com/doi/10.1111/gcb.13839/abstract?utm_content=buffer22bfd&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Best,
ASLR
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Adam Ash

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Re: Conservative Scientists & its Consequences
« Reply #1765 on: July 30, 2017, 11:12:04 AM »
.....

Baffling that we are still wasting ink on this. R2.6 and 1.5C aren't happening. Period. End of story. Chance = 100%. Pretending otherwise at this point is posturing and/or mathurbation.

Well said sir!

The budget is already spent.  Every whiff of GHG from now just makes the unimaginable unimaginably more unimaginable.  Any may god have mercy on our stupid souls, because mother nature will not be so magnanimous.

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Re: Conservative Scientists & its Consequences
« Reply #1766 on: July 30, 2017, 03:34:10 PM »
My local forums appear surprised that I have thrown in the towel and declared them heirs of all that is to come!
1.5 is now dialed in but i fear 2c will not be far behind?
No matter how we reduce our output of GHG's Mother N. keeps filling in our savings with her own ,new, outputs.
First we were told this was due to 'northern soils' , then El Nino drying of the Amazon then permafrost melt..... from what we saw of Yamal last August/Sept there will be more where that came from!!!...... so we are past hopes of 'reducing the growth in GHG's even if we were suddenly to stop our emissions tomorrow.
We now need to look at mitigation and preparation of what we have coming!
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AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #1767 on: August 01, 2017, 12:12:27 AM »
The linked reference indicates that AR5 erred on the side of least drama w.r.t. global temperature increases this century.  However, I suspect that Raftery et. al. (2017) also errs on the side of least drama w.r.t. effective ECS:

Adrian E. Raftery, Alec Zimmer, Dargan M. W. Frierson, Richard Startz & Peiran Liu (2017), "Less Than 2ºC Warming by 2100 Unlikely", Nature Climate Change. DOI: 10.1038/nclimate3352

http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate3352.html?foxtrotcallback=true

Abstract: "The recently published Intergovernmental Panel on Climate Change (IPCC) projections to 2100 give likely ranges of global temperature increase in four scenarios for population, economic growth and carbon use. However, these projections are not based on a fully statistical approach. Here we use a country-specific version of Kaya’s identity to develop a statistically based probabilistic forecast of CO2 emissions and temperature change to 2100. Using data for 1960–2010, including the UN’s probabilistic population projections for all countries, we develop a joint Bayesian hierarchical model for Gross Domestic Product (GDP) per capita and carbon intensity. We find that the 90% interval for cumulative CO2 emissions includes the IPCC’s two middle scenarios but not the extreme ones. The likely range of global temperature increase is 2.0–4.9 °C, with median 3.2 °C and a 5% (1%) chance that it will be less than 2 °C (1.5 °C). Population growth is not a major contributing factor. Our model is not a ‘business as usual’ scenario, but rather is based on data which already show the effect of emission mitigation policies. Achieving the goal of less than 1.5 °C warming will require carbon intensity to decline much faster than in the recent past."

Title: "Earth likely to warm more than 2 degrees this century"

https://phys.org/news/2017-07-earth-degrees-century.html

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Andre

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Re: Conservative Scientists & its Consequences
« Reply #1768 on: August 01, 2017, 03:16:10 AM »
I was just going to post the same study, as mentioned above, which gives limiting warming to 2C a 5% chance.

Either case, here is the Guardian's take on the study, for those who are interested:

https://www.theguardian.com/environment/2017/jul/31/paris-climate-deal-2c-warming-study?CMP=Share_iOSApp_Other

Abstract:

"There is only a 5% chance that the Earth will avoid warming by at least 2C come the end of the century, according to new research that paints a sobering picture of the international effort to stem dangerous climate change.

Global trends in the economy, emissions and population growth make it extremely unlikely that the planet will remain below the 2C threshold set out in the Paris climate agreement in 2015, the study states.

The Paris accord, signed by 195 countries, commits to holding the average global temperature to “well below 2C” above pre-industrial levels and sets a more aspirational goal to limit warming to 1.5C. This latter target is barely plausible, the new research finds, with just a 1% chance that temperatures will rise by less than 1.5C.

“We’re closer to the margin than we think,” said Adrian Raftery, a University of Washington academic who led the research, published in Nature Climate Change. “If we want to avoid 2C, we have very little time left. The public should be very concerned.”




AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #1769 on: August 01, 2017, 03:38:31 AM »
Just a friendly reminder that w.r.t. permafrost degradation, speed kills:
 
Title: “Mysterious craters blowing out of Russia could mean trouble for the whole planet”

http://www.msn.com/en-us/news/world/mysterious-craters-blowing-out-of-russia-could-mean-trouble-for-the-whole-planet/ar-AAp8jkG?li=BBmkt5R&ocid=spartandhp

Extract: “The Russian province's long-frozen ground, called permafrost, is thawing, triggering massive changes to the region's landscape and ecology. It could even threaten human lives.
...
"But what is definitely unprecedented is the rate of warming. The warming that happened 130,000 years ago happened over thousands of years … What we see happening now is warming over decades or a century."

We are therefore seeing a much more rapid collapse of the permafrost, Henderson said.”
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AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #1770 on: August 01, 2017, 06:13:38 AM »
Maybe research like this will give AR6 confidence to give reasonable values for carbon emissions from permafrost degradation:

S. E. Chadburn, E. J. Burke, P. M. Cox, P. Friedlingstein, G. Hugelius & S. Westermann (2017), “An observation-based constraint on permafrost loss as a function of global warming”, Nature Climate Change, Volume: 7, Pages: 340–344, doi:10.1038/nclimate3262

http://www.nature.com/nclimate/journal/v7/n5/full/nclimate3262.html

Abstract: “Permafrost, which covers 15 million km2 of the land surface, is one of the components of the Earth system that is most sensitive to warming. Loss of permafrost would radically change high-latitude hydrology and biogeochemical cycling, and could therefore provide very significant feedbacks on climate change The latest climate models all predict warming of high-latitude soils and thus thawing of permafrost under future climate change, but with widely varying magnitudes of permafrost thaw. Here we show that in each of the models, their present-day spatial distribution of permafrost and air temperature can be used to infer the sensitivity of permafrost to future global warming. Using the same approach for the observed permafrost distribution and air temperature, we estimate a sensitivity of permafrost area loss to global mean warming at stabilization of ~ 4 million km2 °C−1 (1σ confidence), which is around 20% higher than previous studies. Our method facilitates an assessment for COP21 climate change targets: if the climate is stabilized at 2 °C above pre-industrial levels, we estimate that the permafrost area would eventually be reduced by over 40%. Stabilizing at 1.5 °C rather than 2 °C would save approximately 2 million km2 of permafrost.”
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AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #1771 on: August 01, 2017, 04:29:52 PM »
'Ghost forests are most obvious on the Eastern US Coastal areas due to the Gulf Streams influence on regional SLR.  However, as more & more ice sheet mass loss occurs, this problem will become more common along coasts worldwide; which will reduce the effectiveness an important carbon sink; beyond what is assumed in CMIP5/AR5:

Title: "“Ghost forests”: What they are and why they’re becoming more common"

http://www.cbsnews.com/news/ghost-forests-what-they-are-why-theyre-becoming-more-common/

Extract: "They're called "ghost forests" - dead trees along vast swaths of coastline invaded by rising seas, something scientists call one of the most visible markers of climate change.
The process has occurred naturally for thousands of years, but has accelerated in recent decades as polar ice melts and raises sea levels, scientists say, pushing salt water farther inland and killing trees in what used to be thriving freshwater plains.

Efforts are underway worldwide to determine exactly how quickly the creation of ghost forests is increasing. But scientists agree the startling sight of dead trees in once-healthy areas is an easy-to-grasp example of the consequences of climate change.

"I think ghost forests are the most obvious indicator of climate change anywhere on the Eastern coast of the U.S.," said Matthew Kirwan, a professor at Virginia Institute of Marine Science who is studying ghost forests in his state and Maryland. "It was dry, usable land 50 years ago; now it's marshes with dead stumps and dead trees.""
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Re: Conservative Scientists & its Consequences
« Reply #1772 on: August 01, 2017, 09:47:58 PM »
In 2016, C.W. Snyder projected ESS values as high as 9C, as cited in the first reference below (Also see: Replies #1532 & #1534).

C.W. Snyder, “Evolution of global temperature over the past two million years”, Nature, vol. 538, pp. 226-228, 2016. http://dx.doi.org/10.1038/nature19798

http://www.nature.com/nature/journal/v538/n7624/full/nature19798.html

Abstract: "Reconstructions of Earth’s past climate strongly influence our understanding of the dynamics and sensitivity of the climate system. Yet global temperature has been reconstructed for only a few isolated windows of time, and continuous reconstructions across glacial cycles remain elusive. Here I present a spatially weighted proxy reconstruction of global temperature over the past 2 million years estimated from a multi-proxy database of over 20,000 sea surface temperature point reconstructions. Global temperature gradually cooled until roughly 1.2 million years ago and cooling then stalled until the present. The cooling trend probably stalled before the beginning of the mid-Pleistocene transition, and pre-dated the increase in the maximum size of ice sheets around 0.9 million years ago. Thus, global cooling may have been a pre-condition for, but probably is not the sole causal mechanism of, the shift to quasi-100,000-year glacial cycles at the mid-Pleistocene transition. Over the past 800,000 years, polar amplification (the amplification of temperature change at the poles relative to global temperature change) has been stable over time, and global temperature and atmospheric greenhouse gas concentrations have been closely coupled across glacial cycles. A comparison of the new temperature reconstruction with radiative forcing from greenhouse gases estimates an Earth system sensitivity of 9 degrees Celsius (range 7 to 13 degrees Celsius, 95 per cent credible interval) change in global average surface temperature per doubling of atmospheric carbon dioxide over millennium timescales. This result suggests that stabilization at today’s greenhouse gas levels may already commit Earth to an eventual total warming of 5 degrees Celsius (range 3 to 7 degrees Celsius, 95 per cent credible interval) over the next few millennia as ice sheets, vegetation and atmospheric dust continue to respond to global warming."

Now in the second reference a group of climate scientists have critiqued Snyder (2016), but I am too cheap to purchase this paper:

G.A. Schmidt, J. Severinghaus, A. Abe-Ouchi, R.B. Alley, W. Broecker, E. Brook, D. Etheridge, K. Kawamura, R.F. Keeling, M. Leinen, K. Marvel, and T.F. Stocker, “Overestimate of committed warming”, Nature, vol. 547, pp. E16-E17, 2017. http://dx.doi.org/10.1038/nature22803

http://www.nature.com/nature/journal/v547/n7662/full/nature22803.html?foxtrotcallback=true

Finally, in the third reference, C.W. Snyder responses to this critique, but again I am too cheap to purchase this paper.

Carolyn W. Snyder (13 July 2017), "Snyder replies", Nature, Volume: 547, Pages: E17–E18, doi:10.1038/nature22804

http://palgrave.nature.com/nature/journal/v547/n7662/full/nature22804.html

Is anyone willing to provide an overview of this issue, and/or a summary of what is a reasonable range for ESS?
« Last Edit: August 01, 2017, 09:59:45 PM by AbruptSLR »
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Re: Conservative Scientists & its Consequences
« Reply #1773 on: August 01, 2017, 11:37:48 PM »

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Re: Conservative Scientists & its Consequences
« Reply #1774 on: August 01, 2017, 11:47:15 PM »
The linked reference discusses state of the art surface temperature at the West Antarctic Divide for the past ~ 40,000 years (see image bottom panel).  Findings indicate that current climate models are challenged to hind cast the observed findings and that models with low climate sensitivities can be eliminated from consideration.  Furthermore, they find that an Antarctic Amplification of 2 to 3 time GMSTA.  These findings do not bode well for the stability of the WAIS with continued global warming:

Kurt M. Cuffey, Gary D. Clow, Eric J. Steig, Christo Buizert, T. J. Fudge, Michelle Koutnik, Edwin D. Waddington, Richard B. Alley, and Jeffrey P. Severinghaus (2016), "Deglacial temperature history of West Antarctica", PNAS, vol. 113 no. 50, 14249–14254, doi: 10.1073/pnas.1609132113

http://www.pnas.org/content/113/50/14249

Abstract: "The most recent glacial to interglacial transition constitutes a remarkable natural experiment for learning how Earth’s climate responds to various forcings, including a rise in atmospheric CO2. This transition has left a direct thermal remnant in the polar ice sheets, where the exceptional purity and continual accumulation of ice permit analyses not possible in other settings. For Antarctica, the deglacial warming has previously been constrained only by the water isotopic composition in ice cores, without an absolute thermometric assessment of the isotopes’ sensitivity to temperature. To overcome this limitation, we measured temperatures in a deep borehole and analyzed them together with ice-core data to reconstruct the surface temperature history of West Antarctica. The deglacial warming was 11.3±1.8 ∘  11.3±1.8∘ C, approximately two to three times the global average, in agreement with theoretical expectations for Antarctic amplification of planetary temperature changes. Consistent with evidence from glacier retreat in Southern Hemisphere mountain ranges, the Antarctic warming was mostly completed by 15 kyBP, several millennia earlier than in the Northern Hemisphere. These results constrain the role of variable oceanic heat transport between hemispheres during deglaciation and quantitatively bound the direct influence of global climate forcings on Antarctic temperature. Although climate models perform well on average in this context, some recent syntheses of deglacial climate history have underestimated Antarctic warming and the models with lowest sensitivity can be discounted."

Extract: "Of greatest immediate interest, however, is our demonstration that the global deglacial temperature change was amplified by a factor of 2–3 in the Antarctic, that Antarctic warming was largely achieved by 15 ka in coherence with records from Southern Hemisphere mountain ranges, and that climate models of the deglaciation perform well on average, but that the ones with lowest sensitivity can be discounted. The early warming of the Southern Hemisphere, which our study helps to quantify, arose from combined effects of reduced northward oceanic heat transport, increased insolation, and increasing atmospheric CO2. Quantitative simulation of this phenomenon could provide an illuminating challenge for model studies."
« Last Edit: August 02, 2017, 12:05:13 AM by AbruptSLR »
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Re: Conservative Scientists & its Consequences
« Reply #1775 on: August 01, 2017, 11:51:33 PM »
There is discussion of attempts to obtain climate sensitivity from paleo records at

http://www.realclimate.org/index.php/archives/2016/09/why-correlations-of-co2-and-temperature-over-ice-age-cycles-dont-define-climate-sensitivity/

this is referenced in the discussion at realclimate of the Snyder paper :

http://www.realclimate.org/index.php/archives/2017/07/climate-sensitivity-estimates-and-corrections/

sidd


So nothing on Snyder's "combative response".

Carolyn W. Snyder (13 July 2017), "Snyder replies", Nature, Volume: 547, Pages: E17–E18, doi:10.1038/nature22804

http://palgrave.nature.com/nature/journal/v547/n7662/full/nature22804.html
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Re: Conservative Scientists & its Consequences
« Reply #1776 on: August 02, 2017, 12:12:30 AM »
There is a another discussion of the Snyder paper at realclimate in which Jim Hansen commented.

http://www.realclimate.org/index.php/archives/2016/09/the-snyder-sensitivity-situation/

I think the essence of the criticism is that you cannot use a regression of T and CO2 to estimate sensitivity.
van Nes has useful clarification here (DOI: 10.1038/NCLIMATE2568 ) which illustrates the probem with simple regression, but this method does not directly give you a sensitivity. The information flow approach taken by Liang may also help.

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Re: Conservative Scientists & its Consequences
« Reply #1777 on: August 02, 2017, 12:30:38 AM »
There is a another discussion of the Snyder paper at realclimate in which Jim Hansen commented.

http://www.realclimate.org/index.php/archives/2016/09/the-snyder-sensitivity-situation/

I think the essence of the criticism is that you cannot use a regression of T and CO2 to estimate sensitivity.
van Nes has useful clarification here (DOI: 10.1038/NCLIMATE2568 ) which illustrates the probem with simple regression, but this method does not directly give you a sensitivity. The information flow approach taken by Liang may also help.

sidd


Thanks.

Edit, until I know better I will assume the following findings are reasonable:

The linked reference discusses paleodata to indicate that climate sensitivity increased from 3.3 - 5.6 (mean of 4.45k) at the beginning of the PETM up to 3.7 - 6.5 K (mean of 5.1K) near the peak of the PETM; and that if we burn only the easily accessible carbon reserves then GMST could increase by about 10C.  I note these climate sensitivity values are much higher than those inherent in the CMIP5 projections:

Gary Shaffer, Matthew Huber, Roberto Rondanelli & Jens Olaf Pepke Pedersen (23 June 2016), "Deep-time evidence for climate sensitivity increase with warming", Geophysical Research Letters, DOI: 10.1002/2016GL069243

http://onlinelibrary.wiley.com/doi/10.1002/2016GL069243/full

Abstract: "Future global warming from anthropogenic greenhouse gas emissions will depend on climate feedbacks, the effect of which is expressed by climate sensitivity, the warming for a doubling of atmospheric CO2 content. It is not clear how feedbacks, sensitivity and temperature will evolve in our warming world but past warming events may provide insight. Here we employ paleo-reconstructions and new climate-carbon model simulations in a novel framework to explore a wide scenario range for the Paleocene-Eocene Thermal Maximum (PETM) carbon release and global warming event 55.8 million years ago, a possible future warming analogue. We obtain constrained estimates of CO2 and climate sensitivity before and during the PETM and of the PETM carbon input amount and nature. Sensitivity increased from 3.3 - 5.6 to 3.7 - 6.5 K (Kelvin) into the PETM. When taken together with Last Glacial Maximum and modern estimates this result indicates climate sensitivity increase with global warming."

Also see:

https://www.sciencedaily.com/releases/2016/06/160623112206.htm

Extract: ""Our results show that the amount of carbon that drove the PETM warming was about the same amount as the current 'easily accessible' fossil fuel reserves of about 4,000 billion tons. But the warming that would result from adding such large amounts of carbon to the climate system would be much greater today than during the PETM and could reach up to 10 degrees. This is partly due to the current atmosphere containing much less CO2 -- approximately 400 ppm (parts per million) -- compared to before the PETM, where the concentration was about 1,000 ppm and partly because we emit carbon into the atmosphere at a much faster rate than during the PETM. If we then also take into account the fact that climate sensitivity increases with the temperature, it means that it is all the more urgent to limit global warming as soon as possible by reducing the human-made emissions of greenhouse gases," explains Professor Gary Shaffer, who conducted the study in collaboration with researchers from Purdue University, USA, the University of Chile and the Technical University of Denmark."

Edit: Caption for attached image: "Paleo climate sensitivity study reconstructs global warming 56 million years ago and suggests future global warming could be even worse than expected. This graphic shows climate sensitivity at different global temperatures in the atmosphere. The figure shows from the right estimates for the past warm period, the PETM 56 million years ago, the period before the PETM and for the present. On the left the figure shows estimates for the Last Glacial Maximum. Courtesy: Gary Shaffer and Roberto Rondanelli"
« Last Edit: August 02, 2017, 12:49:09 AM by AbruptSLR »
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Re: Conservative Scientists & its Consequences
« Reply #1778 on: August 02, 2017, 12:38:35 AM »
Towards the end of his comment, Hansen remarks thet the Eemian may be a better analogue for the present period than the last deglaciation, and we need better Eemian paleo. I strongly agree, since the end Eemian featured ice sheets as small or smaller than today yet exhibited large sea level rise which would be catastrophic today.

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Re: Conservative Scientists & its Consequences
« Reply #1779 on: August 02, 2017, 01:20:15 AM »
The linked reference examines the case where freshwater hosing effectively shuts-down the AMOC (as in Hansen's ice-climate feedback mechanism); and finds that the ENSO mores to towards the Eastern Pacific; which I note is typically an indication of increased effective ECS:

Mark S. Williamson, Mat Collins, Sybren S. Drijfhout, Ron Kahana, Jennifer V. Mecking and Timothy M. Lenton (2017), "Effect of AMOC collapse on ENSO in a high resolution general circulation model", Climate Dynamics, DOI: 10.1007/s00382-017-3756-0

https://link.springer.com/article/10.1007/s00382-017-3756-0

Abstract: "We look at changes in the El Niño Southern Oscillation (ENSO) in a high-resolution eddy-permitting climate model experiment in which the Atlantic Meridional Circulation (AMOC) is switched off using freshwater hosing. The ENSO mode is shifted eastward and its period becomes longer and more regular when the AMOC is off. The eastward shift can be attributed to an anomalous eastern Ekman transport in the mean equatorial Pacific ocean state. Convergence of this transport deepens the thermocline in the eastern tropical Pacific and increases the temperature anomaly relaxation time, causing increased ENSO period. The anomalous Ekman transport is caused by a surface northerly wind anomaly in response to the meridional sea surface temperature dipole that results from switching the AMOC off. In contrast to a previous study with an earlier version of the model, which showed an increase in ENSO amplitude in an AMOC off experiment, here the amplitude remains the same as in the AMOC on control state. We attribute this difference to variations in the response of decreased stochastic forcing in the different models, which competes with the reduced damping of temperature anomalies. In the new high-resolution model, these effects approximately cancel resulting in no change in amplitude."
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Re: Conservative Scientists & its Consequences
« Reply #1780 on: August 03, 2017, 04:55:26 PM »
The first linked reference studies dynamical cloud response to aerosol forcing and concludes: "The dynamical cloud response is closely linked to the meridional displacement of the Hadley Cell that, in turn, is driven by changes in the cross-equatorial energy transport. In this way, the dynamical cloud changes act as a positive feedback on the meridional displacement of the Hadley Cell, roughly doubling the projected changes in cross-equatorial energy transport compared to that from the microphysical changes alone."  The dynamical cloud changes that Soden & Chung (2017) document is directly relevant findings of the second reference Robert J. Allen & Osinachi Ajoku (2016), which finds that the reduction in aerosol emissions from China is rapidly expanding the NH tropical belt (especially in the Pacific); which contributes directly to higher values of ECS (than assumed by CMIP5/AR5):

Brian Soden and Eui-Seok Chung (2017), "The Large Scale Dynamical Response of Clouds to Aerosol Forcing" Journal of Climate", https://doi.org/10.1175/JCLI-D-17-0050.1

http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-17-0050.1?utm_content=bufferaa6b0&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "We use radiative kernels to quantify the instantaneous radiative forcing of aerosols and the aerosol-mediated cloud response in coupled ocean-atmosphere model simulations under both historical and future emission scenarios. The method is evaluated using matching pairs of historical climate change experiments with and without aerosol forcing and accurately captures the spatial pattern and global mean effects of aerosol forcing. We show that aerosol-driven changes in the atmospheric circulation induce additional cloud changes. Thus, the total aerosol-mediated cloud response consists of both local microphysical changes and non-local dynamical changes that are driven by hemispheric asymmetries in aerosol forcing. By comparing coupled and fixed-SST (sea surface temperature) simulations with identical aerosol forcing we isolate the relative contributions of these two components, exploiting the ability of prescribed SSTs to also suppress changes in the atmospheric circulation. The radiative impact of the dynamical cloud changes are found to be comparable in magnitude to that of the microphysical cloud changes, and act to further amplify the inter-hemispheric asymmetry of the aerosol radiative forcing. The dynamical cloud response is closely linked to the meridional displacement of the Hadley Cell that, in turn, is driven by changes in the cross-equatorial energy transport. In this way, the dynamical cloud changes act as a positive feedback on the meridional displacement of the Hadley Cell, roughly doubling the projected changes in cross-equatorial energy transport compared to that from the microphysical changes alone."

&

Robert J. Allen & Osinachi Ajoku (2016), "Future aerosol reductions and widening of the northern tropical belt", Journal of Geophysical Research Atmospheres, DOI: 10.1002/2016JD024803

http://onlinelibrary.wiley.com/doi/10.1002/2016JD024803/abstract;jsessionid=F22142969E1033CAF1DFF0C651FCFEC5.f02t01

Abstract: "Observations show that the tropical belt has widened over the past few decades, a phenomenon associated with poleward migration of subtropical dry zones and large-scale atmospheric circulation. Although part of this signal is related to natural climate variability, studies have identified an externally forced contribution primarily associated with greenhouse gases (GHGs) and stratospheric ozone loss. Here we show that the increase in aerosols over the twentieth century has led to contraction of the northern tropical belt, thereby offsetting part of the widening associated with the increase in GHGs. Over the 21st century, however, when aerosol emissions are projected to decrease, the effects of aerosols and GHGs reinforce one another, both contributing to widening of the northern tropical belt. Models that have larger aerosol forcing, by including aerosol indirect effects on cloud albedo and lifetime, yield significantly larger Northern Hemisphere (NH) tropical widening than models with direct aerosol effects only. More targeted simulations show that future reductions in aerosols can drive NH tropical widening as large as greenhouse gases, and idealized simulations show the importance of NH midlatitude aerosol forcing. Mechanistically, the 21st century reduction in aerosols peaks near 40°N, which results in a corresponding maximum increase in surface solar radiation, NH midlatitude tropospheric warming amplification, and a poleward shift in the latitude of maximum baroclinicity, implying a corresponding shift in atmospheric circulation. If models with aerosol indirect effects better represent the real world, then future aerosol changes are likely to be an important—if not dominant—driver of NH tropical belt widening."
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Re: Conservative Scientists & its Consequences
« Reply #1781 on: August 03, 2017, 05:56:35 PM »
The linked reference supports the fact that CMIP6 should include freshwater hosing as Hansen has recommended with regards to his ice-climate feedback mechanism:

Florian Sévellec, Alexey V. Fedorov & Wei Liu  (2017), "Arctic sea-ice decline weakens the Atlantic Meridional Overturning Circulation", Nature Climate Change, Volume: 7, Pages: 604–610, doi:10.1038/nclimate3353

http://www.nature.com/nclimate/journal/v7/n8/full/nclimate3353.html?foxtrotcallback=true

Abstract: "The ongoing decline of Arctic sea ice exposes the ocean to anomalous surface heat and freshwater fluxes, resulting in positive buoyancy anomalies that can affect ocean circulation. In this study, we use an optimal flux perturbation framework and comprehensive climate model simulations to estimate the sensitivity of the Atlantic Meridional Overturning Circulation (AMOC) to such buoyancy forcing over the Arctic and globally, and more generally to sea-ice decline. It is found that on decadal timescales, flux anomalies over the subpolar North Atlantic have the largest impact on the AMOC, while on multi-decadal timescales (longer than 20 years), flux anomalies in the Arctic become more important. These positive buoyancy anomalies spread to the North Atlantic, weakening the AMOC and its poleward heat transport. Therefore, the Arctic sea-ice decline may explain the suggested slow-down of the AMOC and the ‘Warming Hole’ persisting in the subpolar North Atlantic."

See also the associated Washington Post article:

Title: "This strange spot in the Atlantic is resisting global warming. Scientists think they know why."

https://www.washingtonpost.com/news/energy-environment/wp/2017/08/02/this-strange-spot-over-the-atlantic-isnt-getting-warmer-scientists-think-they-may-know-why/?utm_term=.32cf9b1011d6

Extract: "A new study, just out in the journal Nature Climate Change, has joined a growing body of literature suggesting the cold patch is evidence that a major ocean current system — which transports heat and influences climate and weather patterns around the world — may be slowing down. What’s more, the melting of Arctic sea ice could be to blame."
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Re: Conservative Scientists & its Consequences
« Reply #1782 on: August 03, 2017, 06:13:36 PM »
The linked reference indicates that reduced plant nitrogen (N) and phosphorous (P) concentrations observed in plants subjected to accelerated growth associated with climate warming of a permafrost region in Tibet, means that those who were hoping that carbon emissions associated with permafrost degradation would be mitigated by increased carbon absorption due to accelerated plant growth are out of luck:

Fei Li, Yunfeng Peng, Susan M. Natali, Kelong Chen, Tianfeng Han, Guibiao Yang, Jinzhi Ding, Dianye Zhang, Guanqin Wang, Jun Wang, Jianchun Yu, Futing Liu & Yuanhe Yang (2 August 2017), "Warming effects on permafrost ecosystem carbon fluxes associated with plant nutrients", Ecology Ecological Society of America, DOI: 10.1002/ecy.1975

http://onlinelibrary.wiley.com/doi/10.1002/ecy.1975/abstract?utm_content=buffer9ccd4&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "Large uncertainties exist in carbon (C)-climate feedback in permafrost regions, partly due to an insufficient understanding of warming effects on nutrient availabilities and their subsequent impacts on vegetation C sequestration. Although a warming climate may promote a substantial release of soil C to the atmosphere, a warming-induced increase in soil nutrient availability may enhance plant productivity, thus offsetting C loss from microbial respiration. Here, we present evidence that the positive temperature effect on carbon dioxide (CO2) fluxes may be weakened by reduced plant nitrogen (N) and phosphorous (P) concentrations in a Tibetan permafrost ecosystem. Although experimental warming initially enhanced ecosystem CO2 uptake, the increased rate disappeared after the period of peak plant growth during the early growing season, even though soil moisture was not a limiting factor in this swamp meadow ecosystem. We observed that warming did not significantly affect soil extractable N or P during the period of peak growth, but decreased both N and P concentrations in the leaves of dominant plant species, likely caused by accelerated plant senescence in the warmed plots. The attenuated warming effect on CO2 assimilation during the late growing season was associated with lowered leaf N and P concentrations. These findings suggest that warming-mediated nutrient changes may not always benefit ecosystem C uptake in permafrost regions, making our ability to predict the C balance in these warming-sensitive ecosystems more challenging than previously thought."
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Re: Conservative Scientists & its Consequences
« Reply #1783 on: August 03, 2017, 06:28:17 PM »
Those scientists who were hoping that the Amazon (as well as other tropical rainforests) would continue to serve as a major carbon sink for decades to come, had better think again based on the findings of the linked reference:

Amir Erfanian, Guiling Wang, and Lori Fomenko (2017), "Unprecedented drought over tropical South America in 2016: significantly under-predicted by tropical SST", Sci Rep.; 7: 5811, doi:  10.1038/s41598-017-05373-2

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5517600/

Abstract: "Tropical and sub-tropical South America are highly susceptible to extreme droughts. Recent events include two droughts (2005 and 2010) exceeding the 100-year return value in the Amazon and recurrent extreme droughts in the Nordeste region, with profound eco-hydrological and socioeconomic impacts. In 2015–2016, both regions were hit by another drought. Here, we show that the severity of the 2015–2016 drought ("2016 drought" hereafter) is unprecedented based on multiple precipitation products (since 1900), satellite-derived data on terrestrial water storage (since 2002) and two vegetation indices (since 2004). The ecohydrological consequences from the 2016 drought are more severe and extensive than the 2005 and 2010 droughts. Empirical relationships between rainfall and sea surface temperatures (SSTs) over the tropical Pacific and Atlantic are used to assess the role of tropical oceanic variability in the observed precipitation anomalies. Our results indicate that warmer-than-usual SSTs in the Tropical Pacific (including El Niño events) and Atlantic were the main drivers of extreme droughts in South America, but are unable to explain the severity of the 2016 observed rainfall deficits for a substantial portion of the Amazonia and Nordeste regions. This strongly suggests potential contribution of non-oceanic factors (e.g., land cover change and CO2-induced warming) to the 2016 drought."

See also:

Title: "Study finds human influence in the Amazon's third 1-in-100 year drought since 2005"

https://www.skepticalscience.com/human-influence-amazon-droughts.html

Extract: "The authors also found that the water temperatures alone could not adequately explain the size and severity of the 2015-2016 drought. This suggests that there are other factors involved as well. To be clear, the authors found that the relationship between water temperatures and drought worked well for prior droughts (the 2005 and 2010 droughts as well as 1983 and 1998 droughts, also El Niño years) but fell apart in 2015-2016. That is, using the relationship, the predicted 2015-2016 drought should not have been nearly as severe or as large as it was. The paper also reports that the 2015-2016 drought clearly exceeded that of the 100-year events in 2005 and 2010. So, in approximately one decade, this zone has had three 100-year events. Quite astonishing.

So why was SST unable to explain the 2015-2016 drought, like it had for past events? Part of it has to do with land-use changes. That is, human changes to the land surface such as deforestation. Another part is related to warming from greenhouse gases. It is clear that land-use changes can affect drought. As farmers deforest, for instance, they convert woodlands and forests into agricultural land. This changes not only the darkness (reflectivity) of the land, but it also impacts the transfer of water to and from the atmosphere (evapotranspiration).

One might ask how warming affects droughts. As air temperatures increase, air is able to evaporate water more rapidly and dry out surfaces. At the same time, air can contain more water vapor so that when rain does occur, it is more often in heavy downpours. These two changes underlie what is referred to as an accelerated hydrological cycle. Simply put, man-made warming is accelerating the movement of water through the ecosystem, which can cause drought even if precipitation does not decrease. Warming also causes changes in the large-scale patterns of air motion (atmospheric circulation) that reduces rainfall in this region."
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Re: Conservative Scientists & its Consequences
« Reply #1784 on: August 04, 2017, 06:32:03 PM »
The linked reference indicates that Sudden Stratospheric Warming, SSW, events will likely become much more frequent in the Arctic with continued global warming.  If so, this would constitute another positive feedback mechanism for Arctic Amplification not adequately characterized by CMIP5/AR5:

Wanying Kang & Eli Tziperman (2017), "More frequent Sudden Stratospheric Warming events due to enhanced MJO forcing expected in a warmer climate", Journal of Climate, https://doi.org/10.1175/JCLI-D-17-0044.1

http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-17-0044.1?utm_content=buffer81f8c&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "Sudden Stratospheric Warming (SSW) events influence the Arctic Oscillation and mid-latitude extreme weather. Observations show SSW events to be correlated with certain phases of Madden-Julian Oscillation (MJO), but the effect of the MJO on SSW frequency is unknown, and the teleconnection mechanism, its planetary wave propagation path and time scale are still not completely understood. We study the Arctic stratosphere response to increased MJO forcing expected in a warmer climate using two models: the comprehensive Whole Atmosphere Community Climate Model and an idealized dry dynamical core with and without MJO-like forcing. We show that the frequency of SSW events increases significantly in response to stronger MJO forcing, also affecting the averaged polar cap temperature. Two teleconnection mechanisms are identified: a direct propagation of MJO-forced transient waves to the Arctic stratosphere, and a nonlinear enhancement of stationary waves by the MJO-forced transient waves. The MJO-forced waves propagate poleward in the lower stratosphere and upper troposphere, and then upward. The cleaner results of the idealized model allow identifying the propagating signal and suggest a horizontal propagation time scale of 10-20 days, followed by additional time for upward propagation within the Arctic stratosphere, although there are significant uncertainties involved. Given that the MJO is predicted to be stronger in a warmer climate, these results suggest that SSW events may become more frequent, with possible implications on tropospheric high latitude weather. However, the effect of an actual warming scenario on SSW frequency involves additional effects besides a strengthening of the MJO, requiring further investigation."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #1785 on: August 05, 2017, 04:25:19 PM »
The linked reference finds that the pH dependence of DMS results in a positive feedback for global warming and that the associated warming of Antarctica occurs at twice the rate of the global mean.  This is not good news for WAIS stability:

Schwinger, J., Tjiputra, J., Goris, N., Six, K. D., Kirkevåg, A., Seland, Ø., Heinze, C., and Ilyina, T.: Amplification of global warming through pH dependence of DMS production simulated with a fully coupled Earth system model, Biogeosciences, 14, 3633-3648, https://doi.org/10.5194/bg-14-3633-2017, 2017.

https://www.biogeosciences.net/14/3633/2017/?utm_content=bufferbbbbb&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract. We estimate the additional transient surface warming ΔTs caused by a potential reduction of marine dimethyl sulfide (DMS) production due to ocean acidification under the high-emission scenario RCP8.5 until the year 2200. Since we use a fully coupled Earth system model, our results include a range of feedbacks, such as the response of marine DMS production to the additional changes in temperature and sea ice cover. Our results are broadly consistent with the findings of a previous study that employed an offline model set-up. Assuming a medium (strong) sensitivity of DMS production to pH, we find an additional transient global warming of 0.30 K (0.47 K) towards the end of the 22nd century when DMS emissions are reduced by 7.3 Tg S yr−1 or 31 % (11.5 Tg S yr−1 or 48 %). The main mechanism behind the additional warming is a reduction of cloud albedo, but a change in shortwave radiative fluxes under clear-sky conditions due to reduced sulfate aerosol load also contributes significantly. We find an approximately linear relationship between reduction of DMS emissions and changes in top of the atmosphere radiative fluxes as well as changes in surface temperature for the range of DMS emissions considered here. For example, global average Ts changes by −0. 041 K per 1 Tg S yr−1 change in sea–air DMS fluxes. The additional warming in our model has a pronounced asymmetry between northern and southern high latitudes. It is largest over the Antarctic continent, where the additional temperature increase of 0.56 K (0.89 K) is almost twice the global average. We find that feedbacks are small on the global scale due to opposing regional contributions. The most pronounced feedback is found for the Southern Ocean, where we estimate that the additional climate change enhances sea–air DMS fluxes by about 9 % (15 %), which counteracts the reduction due to ocean acidification.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #1786 on: August 06, 2017, 04:36:37 PM »
Field observations indicate that the impact of light absorbing particles (LAPs) on snow albedo in the Arctic, North America and China is contributing more to global warming than previously assumed:

Cheng Dang, Stephen G. Warren, Qiang Fu, Sarah J. Doherty & Matthew Sturm (5 August 2017), "Measurements of light-absorbing particles in snow across the Arctic, North America, and China: effects on surface albedo", Journal of Geophysical Research Atmospheres, DOI: 10.1002/2017JD027070 

http://onlinelibrary.wiley.com/doi/10.1002/2017JD027070/abstract?utm_content=buffer427b2&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "Using field observation, we perform radiative transfer calculations on snowpacks in the Arctic, China, and North America to quantify the impact of light-absorbing particles (LAPs) on snow albedo and its sensitivity to different factors. For new snow, the regional-averaged albedo reductions caused by all LAPs in the Arctic, North America, and China are 0.009, 0.012, and 0.077, respectively, of which the albedo reductions caused by black carbon (BC) alone are 0.005, 0.005, and 0.031, corresponding to a positive radiative forcing of 0.06, 0.3, and 3 Wm-2. The albedo reduction for old melting snow is larger than that of new snow by a factor of 2, for the same particulate concentrations; this leads to 3 – 8 times larger radiative forcing, in part due to higher solar irradiance in the melting season. These calculations used ambient snowpack properties; if all snowpacks were instead assumed to be optically thick, the albedo reduction would be 20-50% larger for new snow in the Arctic and North America and 120-300% larger for old snow. Accounting for non-BC LAPs reduces the albedo reduction by BC in the Arctic, North America, and China by 32%, 29% and 70% respectively for new snow and 11%, 7% and 51% for old snow. BC-in-snow albedo reduction computed using two-layer model agrees reasonably with that computed using multi-layer model. Biases in BC concentration or snow depth often lead to nonlinear biases in BC-induced albedo reduction."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #1787 on: August 07, 2017, 04:48:50 PM »
Currently, management models do not adequately account for probable increases eutrophication associated with run-off of excessive nutrients/nitrogen due to changes in precipitation with continued global warming.  This can act as a positive feedback mechanism for more global warming:

E. Sinha, A. M. Michalak & V. Balaji (2017), "Eutrophication will increase during the 21st century as a result of precipitation changes", Science, Vol. 357, Issue 6349, pp. 405-408, DOI: 10.1126/science.aan2409

http://science.sciencemag.org/content/357/6349/405

Abstract: "Eutrophication, or excessive nutrient enrichment, threatens water resources across the globe. We show that climate change–induced precipitation changes alone will substantially increase (19 ± 14%) riverine total nitrogen loading within the continental United States by the end of the century for the “business-as-usual” scenario. The impacts, driven by projected increases in both total and extreme precipitation, will be especially strong for the Northeast and the corn belt of the United States. Offsetting this increase would require a 33 ± 24% reduction in nitrogen inputs, representing a massive management challenge. Globally, changes in precipitation are especially likely to also exacerbate eutrophication in India, China, and Southeast Asia. It is therefore imperative that water quality management strategies account for the impact of projected future changes in precipitation on nitrogen loading."

See also: "The Nitrogen Problem: Why Global Warming Is Making It Worse"

http://e360.yale.edu/features/the-nitrogen-problem-why-global-warming-is-making-it-worse

Extract: "New research shows that increases in rainfall and extreme weather because of climate change will increase the amount of nitrogen polluting rivers and other waterways. The findings underscore the urgency of reforming agriculture to dramatically reduce the use of nitrogen fertilizers."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #1788 on: August 07, 2017, 08:50:02 PM »
The linked reference determines the paleoclimate sensitivity during the Middle Eocene at a latitude of 64 degrees 48 minutes in Canada (see the first image), and finds a regional climate sensitivity of about 13C.  The second image illustrates that these findings indicate exceptionally high values of Arctic Amplification during this period as the atmospheric carbon dioxide concentrations were found to be only about 490 ppm.  While the mean global surface temperature was warmer during the Middle Eocene than today, we are warming at a much faster rate and C02-equiv is already well about 490 ppm.  This does not bode well for our collective future:

Alexander P. Wolfe, Alberto V. Reyes, Dana L. Royer, David R. Greenwood, Gabriela Doria, Mary H. Gagen, Peter A. Siver and John A. Westgate (May 2017), "Middle Eocene CO2 and climate reconstructed from the sediment fill of a subarctic kimberlite maar", GEOLOGY, July 2017; v. 45; no. 7; p. 619–622, doi:10.1130/G39002.1


https://gsw.silverchair-cdn.com/gsw/Content_public/Journal/geology/45/7/10.1130_G39002.1/1/619.pdf?Expires=1502222555&Signature=bqBU8Y3KgwV619Rh98~HEPqPp~aWdJ3w9x893T75q0T5Bn70XB~7Xvjub8K7QrFGN5OhK1RYvai3Aw5yfCYLSjKnKMt7KIMCoZnbo8drd9wtDSqrfEqLJJYFd6X7WWR~nBW9BCmhI0t2QOV2QqS7xkvQPDLc~saDe8e9-V8rrwXRI~WR-KsTvbGe2wz~XUmEU3c-lt~TD1TLajAj4Cb5EVeLNGjtF~0pt2fdKtvHMbl8C9~r5TimyGysbu5vExwPrbZvpLvfjxzipB-l5fiD7QH9qCslsthuwWOPIGGCUquL0tI6lMHQZXugcX5ix1ge4Uj7Ed6RQVvB07liZCi7mA__&Key-Pair-Id=APKAIUCZBIA4LVPAVW3Q
&
http://www.geosociety.org/datarepository/2017/2017202.pdf

Abstract: "Eocene paleoclimate reconstructions are rarely accompanied by parallel estimates of CO2 from the same locality, complicating assessment of the equilibrium climate response to elevated CO2. We reconstruct temperature, precipitation, and CO2 from latest middle Eocene (ca. 38 Ma) terrestrial sediments in the post eruptive sediment fill of the Giraffe kimberlite in subarctic Canada. Mutual climatic range and oxygen isotope analyses of botanical fossils reveal a humid temperate forest ecosystem with mean annual temperatures (MATs) more than 17 °C warmer than present and mean annual precipitation ~4× present. Metasequoia stomatal indices and gas-exchange modeling produce median CO2 concentrations of ~630 and ~430 ppm, respectively, with a combined median estimate of ~490 ppm. Reconstructed MATs are more than 6 °C warmer than those produced by Eocene climate models forced at 560 ppm CO2. Estimates of regional climate sensitivity, expressed as ΔMAT per CO2 doubling above preindustrial levels, converge on a value of ~13 °C, underscoring the capacity for exceptional polar amplification of warming and hydrological intensification under modest CO2 concentrations once both fast and slow feedbacks become expressed."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #1789 on: August 09, 2017, 06:11:22 PM »
The linked reference uses model projections to demonstrate that relatively large and rapid obduction (re-emergence) of anthropogenic carbon into the well-mixed surface layer in the ocean will contribute to limiting of future ocean uptake of carbon from the atmosphere.  This is not good news, but hopefully this obduction mechanism will be incorporated into CMIP6 models:

Katsuya Toyama et. al. (2017), "Large Re-emergence of Anthropogenic Carbon Into the Ocean’s Surface Mixed Layer Sustained by the Ocean’s Overturning Circulation", Journal of Climate, https://doi.org/10.1175/JCLI-D-16-0725.1

http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-16-0725.1?utm_content=buffer00f0c&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "We evaluate the output from a widely used ocean carbon cycle model to identify the subduction and obduction (re-emergence) rates of anthropogenic carbon (Cant) for climatological conditions during the World Ocean Circulation Experiment (WOCE) era in 1995 using a new set of Lagrangian diagnostic tools. The principal scientific value of the Lagrangian diagnostics is in providing a new means to connect Cant re-emergence pathways to the relatively rapid renewal timescales of mode waters through the overturning circulation.

Our main finding is that for this model with 2.04 PgC/yr of uptake of Cant via gas exchange, the subduction and obduction rates across the base of the mixed layer (MLbase) are 4.96 PgC/yr and 4.50 PgC/yr, respectively, which are twice as large as the gas exchange at the surface. Given that there is net accumulation of 0.17 PgC/yr in the mixed layer itself, this implies the residual downward Cant transport of 1.40 PgC/yr across the MLbase is associated with diffusion. Importantly, the net patterns for subduction and obduction transports of Cant mirror the large-scale patterns for transport of water volume, thereby illustrating the processes controlling Cant uptake. Although the net transfer across the MLbase by compensating subduction and obduction is relatively smaller than the diffusion, localized pattern of Cant subduction and obduction implies significant regional impacts. The median timescale for re-emergence of obducting particles is short (less than 10 years), indicating that re-emergence should contribute to limiting future carbon uptake through its contribution to perturbing the Revelle factor for surface waters."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #1790 on: August 14, 2017, 05:00:40 PM »
Many (most) climate change 'experts' are subject to erring on the side of least drama; in such cases the linked 'Systematic Correlation Matrix Evaluation, SCoMaE, can help to better assess Earth System model projections.  The linked reference discusses a study whose "… results do suggest that a comprehensive assessment of future climatic states needs a re-evaluation of the ad-hoc chosen indicators, due to changes in prevailing climate responses."  While I doubt that the AR6 'experts' would be willing to replace their 'ad-hoc' indicators with more objective indicators (as this would create 'drama' with their sponsoring governments); nevertheless, the linked reference represents progress in the effort overcoming ESLD.

Mengis, N., Keller, D. P., and Oschlies, A.: Systematic Correlation Matrix Evaluation (SCoMaE) – A bottom-up, natural science-based approach to identify Indicators, Earth Syst. Dynam. Discuss., https://doi.org/10.5194/esd-2017-72, in review, 2017.

https://www.earth-syst-dynam-discuss.net/esd-2017-72/
&
https://www.earth-syst-dynam-discuss.net/esd-2017-72/esd-2017-72.pdf

Abstract. This study introduces the Systematic Correlation Matrix Evaluation (SCoMaE) method, a bottom-up approach which combines expert judgment and statistical information to systematically select transparent, non-redundant indicators for a comprehensive assessment of the state of the Earth system. The methods consists of three basic steps: 1) Calculation of a correlation matrix among variables relevant for a given research question, 2) Systematic evaluation of the matrix, to identify clusters of variables with similar behavior and respective mutually independent indicators, and 3) Interpretation of the identified clusters, enabling a learning effect from the selection of indicators. Optional further analysis steps include: 4) Testing the robustness of identified clusters with respect to changes in forcing or boundary conditions, 5) Enabling a comparative assessment of varying scenarios by constructing and evaluating a common correlation matrix, or 6) Inclusion of expert judgment such as to prescribe indicators, to allow for considerations other than statistical consistency. The exemplary application of the SCoMaE method to Earth system model output forced by different CO2 emission scenarios reveals the necessity of re-evaluating indicators identified in a historical scenario simulation for an accurate assessment of an intermediate-high, as well as a business-as-usual, climate change scenario simulation, which arises from changes in prevailing correlations in the Earth system under varying climate forcing. For a comparative assessment of the three climate change scenarios, we construct and evaluate a common correlation matrix, in which we identify robust correlations between variables across the three considered scenarios.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #1791 on: August 15, 2017, 07:49:47 PM »
The linked reference studies paleodata over the past four glacial/interglacial cycles and indicates that:

"The sensitivity of the responses to GHG concentrations rises dramatically by a factor of 2–4 at atmospheric CO2 levels of >220 ppm. Our results suggest that the equatorial Pacific acts as a nonlinear amplifier…"

That the Equatorial Pacific can act as a nonlinear amplifier for climate sensitivity does not bode well for mankind's future wellbeing with continued global warming, as the degree of reported nonlinearity for this feedback mechanism is underestimated in AR5:

Li Lo et. al. (2017), "Nonlinear climatic sensitivity to greenhouse gases over past 4 glacial/interglacial cycles", Scientific Reports 7, Article number: 4626, doi:10.1038/s41598-017-04031-x

https://www.nature.com/articles/s41598-017-04031-x.

Abstract: "The paleoclimatic sensitivity to atmospheric greenhouse gases (GHGs) has recently been suggested to be nonlinear, however a GHG threshold value associated with deglaciation remains uncertain. Here, we combine a new sea surface temperature record spanning the last 360,000 years from the southern Western Pacific Warm Pool with records from five previous studies in the equatorial Pacific to document the nonlinear relationship between climatic sensitivity and GHG levels over the past four glacial/interglacial cycles. The sensitivity of the responses to GHG concentrations rises dramatically by a factor of 2–4 at atmospheric CO2 levels of >220 ppm. Our results suggest that the equatorial Pacific acts as a nonlinear amplifier that allows global climate to transition from deglacial to full interglacial conditions once atmospheric CO2 levels reach threshold levels."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

TerryM

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Re: Conservative Scientists & its Consequences
« Reply #1792 on: August 15, 2017, 10:09:12 PM »
So all that's required for us to escape the most disastrous prognostications is for us to pull back to 219-e CO2 ppm?
Should be a walk in the park, a piece of cake, and as easy as falling off log.


First we quit using electricity.
Then we quit building "stuff".
Finally we quit eating.


If we quit eating first, the others will look after themselves.


Terry

wili

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Re: Conservative Scientists & its Consequences
« Reply #1793 on: August 15, 2017, 11:13:34 PM »
I know you're being snarky, but if you don't mind some friendly amendments...

1. Stop using fossil-death-fuel generated electricity. 1/3 of world electricity is produced by renewables, hydro and nukes. This would be difficult, but there's lots of waste that could relatively easily cut out, and if we really see that we are essentially at war, we should be willing to make some sacrifices to provide a marginally livable future.

2. There is certainly a whole lot of 'stuff' that we could stop making.

3. We can all or most of us mostly give up most meat most of the time, and cut back as well on dairy, especially cheeses that have a particularly large carbon footprint.

Such moves might give a tiny bit of breathing room as we continue to build out renewables to replace nukes and ultimately most hydro, while insuring there is enough food for humans and living area for other species.

Few scientists are willing to make such statements, though. Too many seem to be under the sway of what 'economists' think is reasonably doable. We need to start ignoring such ignorant voices of 'reason.'
"A force de chercher de bonnes raisons, on en trouve; on les dit; et après on y tient, non pas tant parce qu'elles sont bonnes que pour ne pas se démentir." Choderlos de Laclos "You struggle to come up with some valid reasons, then cling to them, not because they're good, but just to not back down."

TerryM

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Re: Conservative Scientists & its Consequences
« Reply #1794 on: August 16, 2017, 01:28:44 AM »
Well said wili.


Terry

rboyd

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Re: Conservative Scientists & its Consequences
« Reply #1795 on: August 16, 2017, 03:07:19 AM »
The linked reference studies paleodata over the past four glacial/interglacial cycles and indicates that:
"The sensitivity of the responses to GHG concentrations rises dramatically by a factor of 2–4 at atmospheric CO2 levels of >220 ppm. Our results suggest that the equatorial Pacific acts as a nonlinear amplifier…"

So there was a non-linear jump at around 220ppm CO2, which is below pre-industrial levels. This means that there may be another such non-linearity but not that there is such a one. Underlines the need for exercising the precautionary principal, if we hit such an unknown non-linearity it may be game over pretty fast.

The paper mentions that the required data is not available for the Pliocene, which had 300-500ppm. As we are already at 500+ppm CO2e we may have already run that required real-time experiment. Using a GWP20 for methane we are already testing a forcing of over 600ppm CO2e. We are trying really hard to find any such non-linearities.

A shortcoming of the discussion part of the paper is the lack of acceptance of the true level of current GHG forcing taking into the non-CO2 gases.
« Last Edit: August 16, 2017, 08:58:41 AM by rboyd »

AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #1796 on: August 16, 2017, 05:04:55 AM »
wili & rboyd,

Thank you both for your thoughtful explanations. 

Dealing with climate change would not be as dire of a problem if people (not just conservative scientists) would just realize their addiction to BAU in a timely fashion and applied similar clear thinking.  Perhaps some version of a twelve step addiction program would help people to learn that to change bad habits, they just need to take one step at a time.

Best regards,
ASLR
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #1797 on: August 16, 2017, 04:25:39 PM »
The linked reference discusses a study of predicting the response of tropical rainforests to climate change.  It was the first such study "… to rely on Bayesian model calibration and synthesis to elucidate the key physiological parameters that drive uncertainty in tropical forests responses to climatic change."  It focused on a tropical forest in Puerto Rico and found that over the coming decades the forest would be changed from a carbon sink to a carbon source.  Most CMIP5 err on the side of least drama with regard to this important positive feedback mechanism:

Xiaohui Feng et. al. (14 August 2017), "Improving predictions of tropical forest response to climate change through integration of field studies and ecosystem modeling", Global Change Biology, DOI: 10.1111/gcb.13863

http://onlinelibrary.wiley.com/doi/10.1111/gcb.13863/abstract?utm_content=buffer4875c&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "Tropical forests play a critical role in carbon and water cycles at a global scale. Rapid climate change is anticipated in tropical regions over the coming decades and, under a warmer and drier climate, tropical forests are likely to be net sources of carbon rather than sinks. However, our understanding of tropical forest response and feedback to climate change is very limited. Efforts to model climate change impacts on carbon fluxes in tropical forests have not reached a consensus. Here we use the Ecosystem Demography model (ED2) to predict carbon fluxes of a Puerto Rican tropical forest under realistic climate change scenarios. We parameterized ED2 with species-specific tree physiological data using the Predictive Ecosystem Analyzer workflow and projected the fate of this ecosystem under five future climate scenarios. The model successfully captured inter-annual variability in the dynamics of this tropical forest. Model predictions closely followed observed values across a wide range of metrics including above-ground biomass, tree diameter growth, tree size class distributions, and leaf area index. Under a future warming and drying climate scenario, the model predicted reductions in carbon storage and tree growth, together with large shifts in forest community composition and structure. Such rapid changes in climate led the forest to transition from a sink to a source of carbon. Growth respiration and root allocation parameters were responsible for the highest fraction of predictive uncertainty in modeled biomass, highlighting the need to target these processes in future data collection. Our study is the first effort to rely on Bayesian model calibration and synthesis to elucidate the key physiological parameters that drive uncertainty in tropical forests responses to climatic change. We propose a new path forward for model-data synthesis that can substantially reduce uncertainty in our ability to model tropical forest responses to future climate."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #1798 on: August 16, 2017, 06:57:52 PM »
So there was a non-linear jump at around 220ppm CO2, which is below pre-industrial levels. This means that there may be another such non-linearity but not that there is such a one. Underlines the need for exercising the precautionary principal, if we hit such an unknown non-linearity it may be game over pretty fast.

The paper mentions that the required data is not available for the Pliocene, which had 300-500ppm. As we are already at 500+ppm CO2e we may have already run that required real-time experiment. Using a GWP20 for methane we are already testing a forcing of over 600ppm CO2e. We are trying really hard to find any such non-linearities.

A shortcoming of the discussion part of the paper is the lack of acceptance of the true level of current GHG forcing taking into the non-CO2 gases.


I concatenated the following reposts related to likely increase of El Nino events with continued warming.  In particular, N. J. Burls and A. V. Fedorov, (2014) notes that if we approach Pliocene conditions, there may be an abrupt/nonlinear change in the Equatorial Pacific into near continuous El Nino-like conditions:

The first linked reference uses CMIP5 projections to estimate that at least one source of currently increasing positive feedback for increases in atmospheric CO₂ concentrations accelerate is that during El Nino events lead to reductions in terrestrial productivity.  So theoretically this natural source should decrease as our current El Nino event continues to degrade:

Jin-Soo Kim, Jong-Seong Kug, Jin-Ho Yoon and Su-Jong Jeong (2016), "Increased atmospheric CO2 growth rate during El Niño driven by reduced terrestrial productivity in the CMIP5 ESMs", Journal of Climate, doi: http://dx.doi.org/10.1175/JCLI-D-14-00672.1

http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-14-00672.1

Abstract: "Better understanding of factors that control the global carbon cycle could increase confidence in climate projections. Previous studies found good correlation between the growth rate of atmospheric CO2 concentration and the El Niño–Southern Oscillation (ENSO). Growth rate of atmospheric CO2 increases during El Niño but decreases during La Niña. In this study, long-term simulations of the Earth System Models (ESMs) in the Coupled Model Intercomparison Project Phase 5 archive were used to examine the interannual carbon flux variability associated with ENSO. The ESMs simulate the relationship reasonably well with a delay of several months between ENSO and the changes in atmospheric CO2. The increase in atmospheric CO2 associated with El Niño is mostly caused by decreasing Net Primary Production (NPP) in the ESMs. It is suggested that NPP anomalies over South Asia are at their maxima during boreal spring; therefore, the increase in CO2 concentration lags four to five months behind the peak phase of El Niño. The decrease in NPP during El Niño may be caused by decreased precipitation and increased temperature over tropical regions. Furthermore, systematic errors may exist in the ESM-simulated temperature responses to ENSO phases over tropical land areas, and these errors may lead to overestimation of ENSO-related NPP anomalies. In contrast, carbon fluxes from heterotrophic respiration and natural fires are likely underestimated in the ESMs compared with offline model results and observational estimates, respectively. These uncertainties should be considered in long-term projections that include climate–carbon feedbacks."

Also, many scientists are concerned that the Earth may be headed towards a Pliocene type of climate this century due to global warming.  The linked reference indicates that changes in cloud cover/albedo for such conditions would rapidly induce the Equatorial Pacific Ocean into a permanent El Nino-like state.  As cloud albedo is a rapid response feedback mechanism, such a change could happen in as little as a few decades from now (say 2040-2050). Permanent El Nino-like conditions would telecommunicate large amounts of heat from the Equatorial Pacific directly to West Antarctica.

N. J. Burls and A. V. Fedorov, (2014), "Simulating Pliocene warmth and a permanent El Niño-like state: the role of cloud albedo", Paleoceanography, DOI: 10.1002/2014PA00264

http://onlinelibrary.wiley.com/doi/10.1002/2014PA002644/abstract

Abstract: "Available evidence suggests that during the early Pliocene (4-5 Ma) the mean east–west sea surface temperature (SST) gradient in the equatorial Pacific Ocean was significantly smaller than today, possibly reaching only 1-2°C. The meridional SST gradients were also substantially weaker, implying an expanded ocean warm pool in low latitudes. Subsequent global cooling led to the establishment of the stronger, modern temperature gradients. Given our understanding of the physical processes that maintain the present-day cold tongue in the east, warm pool in the west and hence sharp temperature contrasts, determining the key factors that maintained early Pliocene climate still presents a challenge for climate theories and models. This study demonstrates how different cloud properties could provide a solution. We show that a reduction in the meridional gradient in cloud albedo can sustain reduced meridional and zonal SST gradients, an expanded warm pool and warmer thermal stratification in the ocean, weaker Hadley and Walker circulations in the atmosphere. Having conducted a range of hypothetical modified cloud albedo experiments, we arrive at our Pliocene simulation, which shows good agreement with proxy SST data from major equatorial and coastal upwelling regions, the tropical warm pool, mid and high latitudes, and available subsurface temperature data. As suggested by the observations, the simulated Pliocene-like climate sustains a robust ENSO despite the reduced mean east–west SST gradient. Our results demonstrate that cloud albedo changes may be a critical element of Pliocene climate and that simulating the meridional SST gradient correctly is central to replicating the geographical patterns of Pliocene warmth.""

Also, Kim et al (2014) indicates that before 2040 CMIP5 models indicate that the amplitude of the ENSO phases will increase, indicating that when the El Nino events return for the next 25-years they are likely to be stronger than previously experienced leading to more abrupt climate change [see: Seon Tae Kim, Wenju Cai, Fei-Fei Jin, Agus Santoso, Lixin Wu, Eric Guilyardi & Soon-Il An, (2014), "Response of El Niño sea surface temperature variability to greenhouse warming", Nature Climate Change, doi:10.1038/nclimate2326].

Also, Praetorius & Mix (2014) provide paleo-evidence of the importance of the synchronization of the North Pacific, and the North Atlantic, Oceans on Artic amplification: Summer K. Praetorius, Alan C. Mix, (2014), "Synchronization of North Pacific and Greenland climates preceded abrupt deglacial warming", Science 25 July 2014: Vol. 345 no. 6195 pp. 444-448 DOI: 10.1126/science.1252000

Edit: For ease of reference, I provide the attached image which indicates the timeline for the most recent epochs (including the Pliocene)
« Last Edit: August 16, 2017, 08:01:46 PM by AbruptSLR »
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rboyd

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Re: Conservative Scientists & its Consequences
« Reply #1799 on: August 16, 2017, 08:18:48 PM »
Given the inherent conservativeness of the CMIP5 models and the high level of current forcing (higher then the Pliocene and the Miocene on a CO2e basis), such things may happen a bit earlier than 2040. Also, given the rate of change, which is many times faster than during the Pliocene, such transitions may be extremely chaotic.

Temperatures fell from the Miocene to the Pliocene, so there would be glaciation, rather than deglaciation. So, no North Atlantic "cold pool" from Greenland melting to produce bigger storms with the warmer waters surrounding it. Also, no melt water lens in the Antarctic to force the warmer waters down toward the base of the ice sheet and generate stormier weather. Hansen has proposed that the melt-waters may stall atmospheric warming at some point, as greater amounts of heat are taken up by the oceans. I do wonder if this effect may be counter-balanced by such things as an ice-free Arctic and a bigger/permanent ENSO.

I am reading up on the "Mid Miocene Climate Optimum" which was produced by a "rapid" (still over tens of thousands of years, not a few decades) rise in CO2 from 400ppm to 500ppm - so perhaps a bit better analog for the present. Although the natural environment is much more degraded today (e.g. cities, roads, deforestation etc.) and the rate of CO2 increase is a thousand times faster.

A climate sensitivity of 4 degrees or higher seems to be required to get ESM's to match the MMCO with any accuracy. Arctic cloud cover in winter also seems to keep the Arctic ice-free year round. Interesting that a permanent El Nino has a name "El Padre"

https://www.skepticalscience.com/print.php?n=2845

https://www.clim-past.net/10/523/2014/cp-10-523-2014.pdf

With even NOAA saying that we are pretty much at 500ppm on a CO2e basis, there should be much more discussion about the Miocene. The Pliocene is already in the rear-view mirror on a CO2e basis.
« Last Edit: August 16, 2017, 08:28:14 PM by rboyd »