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Lennart van der Linde

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Re: Conservative Scientists & its Consequences
« Reply #2100 on: January 22, 2018, 08:09:05 PM »
We will see. That is one opinion against many.

Is it? According to the Oslo Principles of the Expert Group on Global Climate Obligations the precautionary principle should be (legally) leading in deciding on climate policy (see extracted text below):
https://climateprinciplesforenterprises.files.wordpress.com/2017/12/osloprincipleswebpdf.pdf

So the very real possibility of a relatively high ECS should lead to a relatively (very) strong climate and GHG emissions reduction policy, as far as I can tell.

Sleepy

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Re: Conservative Scientists & its Consequences
« Reply #2101 on: January 22, 2018, 08:26:17 PM »
Nice video with Dessler above. Thanks.
Here's my humble and naive opinion, we only have one planet. We don't need one single model output to take care of it. It's out there, just take a look at it, act accordingly. Try to be wise while doing it.

Attaching a few other (less naive) opinions that I'm aware of:
Brown and Caldeira
https://www.nature.com/articles/nature24672
Xu and Ramanathan
http://www.pnas.org/content/114/39/10315.full
Fasullo and Trenberth
http://science.sciencemag.org/content/338/6108/792
Zhai et al
http://onlinelibrary.wiley.com/doi/10.1002/2015GL065911/full
Friedrich et al
http://advances.sciencemag.org/content/2/11/e1501923.full
Lauer et al
http://journals.ametsoc.org/doi/abs/10.1175/2010JCLI3666.1
Omnia mirari, etiam tritissima.
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Science is a jealous mistress and takes little account of a man's feelings.

AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #2102 on: January 22, 2018, 10:06:19 PM »
RealClimate finds that the claim (based on the Cox et al 2018 reference) of reduced uncertainty for ECS is premature:

Title: "The claim of reduced uncertainty for equilibrium climate sensitivity is premature"

http://www.realclimate.org/index.php/archives/2018/01/the-claim-of-reduced-uncertainty-for-equilibrium-climate-sensitivity-is-premature/

Extract: "The calculations in question involved both an over-simplification and a set of assumptions which limit their precision, if applied to Earth’s real climate system.

They provide a nice idealised and theoretical description, but they should not be interpreted as an accurate reflection of the real world.

Cox et al. assumed that the same feedback mechanisms are involved in both natural variations and a climate change due to increased CO2. This means that we should expect a high climate sensitivity if there are pronounced natural variations.

But it is not that simple, as different feedback mechanisms are associated with different time scales. Some are expected to react rapidly, but others associated with the oceans and the carbon cycle may be more sluggish. There could also be tipping points, which would imply a high climate sensitivity."
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Daniel B.

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Re: Conservative Scientists & its Consequences
« Reply #2103 on: January 22, 2018, 10:19:21 PM »
Reading further, the real climate poster had an issue with the precision, not the accuracy.  The conclusion states, “I nevertheless think that the study is interesting and it is impressive that the results are so similar to previously published results.” 

wili

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Re: Conservative Scientists & its Consequences
« Reply #2104 on: January 22, 2018, 10:52:34 PM »
Thanks for linking this RC piece, ASRL.

That was exactly my impression of this study. Nice to hear my general feeling about it confirmed in much clearer terms than I could muster by professionals in the field!
"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."

AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #2105 on: January 22, 2018, 11:15:58 PM »
Increasing Arctic Amplification is closely related to the increase in low-elevation cloud cover, and the linked reference finds: "… that the response of low-level clouds in the Arctic to anthropogenic aerosols lies close to a theoretical maximum and is between 2 and 8 times higher than has been observed elsewhere."

Q. Coopman, T. J. Garrett, D. P. Finch & J. Riedi (3 January 2018), "High Sensitivity of Arctic Liquid Clouds to Long-Range Anthropogenic Aerosol Transport", Geophysical Research Letters, DOI: 10.1002/2017GL075795 

http://onlinelibrary.wiley.com/doi/10.1002/2017GL075795/full

Abstract: "The rate of warming in the Arctic depends upon the response of low-level microphysical and radiative cloud properties to aerosols advected from distant anthropogenic and biomass-burning sources. Cloud droplet cross-section density increases with higher concentrations of cloud condensation nuclei, leading to an increase of cloud droplet absorption and scattering radiative cross sections. The challenge of assessing the magnitude of the effect has been decoupling the aerosol impacts on clouds from how clouds change solely due to natural meteorological variability. Here we address this issue with large, multi-year satellite, meteorological, and tracer transport model data sets to show that the response of low-level clouds in the Arctic to anthropogenic aerosols lies close to a theoretical maximum and is between 2 and 8 times higher than has been observed elsewhere. However, a previously described response of arctic clouds to biomass-burning plumes appears to be overstated because the interactions are rare and modification of cloud radiative properties appears better explained by coincident changes in temperature, humidity, and atmospheric stability."
“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 #2106 on: January 23, 2018, 06:51:07 PM »
...
There's a real reason equable climate regimes show up repeatedly in the fossil records. They're also almost all universally considerably warmer than even the current generation of modeling can reproduce (although some recent improvement has been made). Land (continent) placement has something to do with it, but repeated episodes of equable climates with vastly different land configuration is a sign that ocean/atmosphere configuration is immensely important as well.

The linked reference confirms that most climate simulations do not capture the greater polar amplification during the Eocene.  As CO2e approaches 560ppm this type of information could become highly relevant to modern times:

David Evans, et al (January 22, 2018), "Eocene greenhouse climate revealed by coupled clumped isotope-Mg/Ca thermometry", PNAS, doi: 10.1073/pnas.1714744115

http://www.pnas.org/content/early/2018/01/12/1714744115.abstract

Significance: "Reconstructing the degree of warming during geological periods of elevated CO2 provides a way of testing our understanding of the Earth system and the accuracy of climate models. We present accurate estimates of tropical sea-surface temperatures (SST) and seawater chemistry during the Eocene (56–34 Ma before present, CO2 >560 ppm). This latter dataset enables us to reinterpret a large amount of existing proxy data. We find that tropical SST are characterized by a modest warming in response to CO2. Coupling these data to a conservative estimate of high-latitude warming demonstrates that most climate simulations do not capture the degree of Eocene polar amplification."

Abstract: "Past greenhouse periods with elevated atmospheric CO2 were characterized by globally warmer sea-surface temperatures (SST). However, the extent to which the high latitudes warmed to a greater degree than the tropics (polar amplification) remains poorly constrained, in particular because there are only a few temperature reconstructions from the tropics. Consequently, the relationship between increased CO2, the degree of tropical warming, and the resulting latitudinal SST gradient is not well known. Here, we present coupled clumped isotope (Δ47)-Mg/Ca measurements of foraminifera from a set of globally distributed sites in the tropics and midlatitudes. Δ47 is insensitive to seawater chemistry and therefore provides a robust constraint on tropical SST. Crucially, coupling these data with Mg/Ca measurements allows the precise reconstruction of Mg/Casw throughout the Eocene, enabling the reinterpretation of all planktonic foraminifera Mg/Ca data. The combined dataset constrains the range in Eocene tropical SST to 30–36 °C (from sites in all basins). We compare these accurate tropical SST to deep-ocean temperatures, serving as a minimum constraint on high-latitude SST. This results in a robust conservative reconstruction of the early Eocene latitudinal gradient, which was reduced by at least 32 ± 10% compared with present day, demonstrating greater polar amplification than captured by most climate models."
« Last Edit: January 23, 2018, 08:50:52 PM by AbruptSLR »
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AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #2107 on: January 23, 2018, 09:15:39 PM »
Just a remainder that methods using Earth's historical energy budget have typically resulted in relatively low estimates of climate sensitivity as demonstrated by Richardson et al (2016), while Armour (2016) shows that even Richardson et al (2016) presented relative low values of ECS when considering time-dependence (see the first attached image):

Mark Richardson, Kevin Cowtan, Ed Hawkins & Martin B. Stolpe (2016), "Reconciled climate response estimates from climate models and the energy budget of Earth, Nature Climate Change 6, doi:1038/nclimate3066

https://www.nature.com/articles/nclimate3066

Edit, to better understand the importance of slow climate modes on ECS also see (& the second attached image):

Cristian Proistosescu and Peter J. Huybers (05 Jul 2017), "Slow climate mode reconciles historical and model-based estimates of climate sensitivity", Science Advances, Vol. 3, no. 7, e1602821, DOI: 10.1126/sciadv.1602821

http://advances.sciencemag.org/content/3/7/e1602821
« Last Edit: January 23, 2018, 09:23:16 PM by AbruptSLR »
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AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #2108 on: January 24, 2018, 04:42:13 PM »
It looks like future methane emissions from shallow lakes in agricultural areas have likely been underestimated due to the synergy between nutrients (from the agriculture) and future warming:

Title: "Combined nutrients and warming massively increase methane emissions from lakes"

https://phys.org/news/2018-01-combined-nutrients-massively-methane-emissions.html

Extract: "Shallow lakes in agricultural landscapes will emit significantly greater amounts of methane, mostly in the form of bubbles (ebullition) in a warmer world, which is a potential positive feedback mechanism to climate warming.

The present study used the longest-running freshwater mesocosm climate change experiment in the world to investigate how warming and eutrophication might interact to change methane ebullition in the future.
The results here were striking as they showed that the combination of increased nutrient loading and warming had a synergistic effect on the ebullition of methane. In the absence of nutrient enrichment, warming alone increased annual methane ebullition by around 50 percent and its relative contribution to total methane emission rose from about 50 percent to 75 percent.
In stark contrast, when nutrient levels were high, warming increased total methane emission by at least six-fold, and in some cases, 17-fold, and the proportion of ebullition increased to 95 percent of total annual methane flux."

See also:

Thomas A. Davidson et al, Synergy between nutrients and warming enhances methane ebullition from experimental lakes, Nature Climate Change (2018). DOI: 10.1038/s41558-017-0063-z
“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 #2109 on: January 24, 2018, 05:30:03 PM »
I provide links to the following 2015 article (& associated 2016 reference) to remind us all that while most consensus discussion of climate sensitivity focuses on feedbacks due to increases in global temperatures, that feedbacks based on increases in Arctic precipitation can create a positive feedback comparable to a doubling of global carbon dioxide:

Title: "Melting sea ice increases Arctic precipitation, complicates climate predictions"

https://phys.org/news/2015-12-sea-ice-arctic-precipitation-complicates.html

Extract: "The melting of sea ice will significantly increase Arctic precipitation, creating a climate feedback comparable to doubling global carbon dioxide, a Dartmouth College-led study finds."

See also:
Kopec et al (2016), "Influence of sea ice on Arctic precipitation", PNAS, vol. 113 no. 1 46-51, doi: 10.1073/pnas.1504633113

http://www.pnas.org/content/113/1/46

Abstract: "Global climate is influenced by the Arctic hydrologic cycle, which is, in part, regulated by sea ice through its control on evaporation and precipitation. However, the quantitative link between precipitation and sea ice extent is poorly constrained. Here we present observational evidence for the response of precipitation to sea ice reduction and assess the sensitivity of the response. Changes in the proportion of moisture sourced from the Arctic with sea ice change in the Canadian Arctic and Greenland Sea regions over the past two decades are inferred from annually averaged deuterium excess (d-excess) measurements from six sites. Other influences on the Arctic hydrologic cycle, such as the strength of meridional transport, are assessed using the North Atlantic Oscillation index. We find that the independent, direct effect of sea ice on the increase of the percentage of Arctic sourced moisture (or Arctic moisture proportion, AMP) is 18.2 ± 4.6% and 10.8 ± 3.6%/100,000 km2 sea ice lost for each region, respectively, corresponding to increases of 10.9 ± 2.8% and 2.7 ± 1.1%/1 °C of warming in the vapor source regions. The moisture source changes likely result in increases of precipitation and changes in energy balance, creating significant uncertainty for climate predictions."
“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 #2110 on: January 24, 2018, 10:54:57 PM »
It looks like at least BP and Shell Oil understand this it better to be safe than sorry:

Title: "BP and Shell planning for catastrophic 5°C global warming despite publicly backing Paris climate agreement"

http://www.independent.co.uk/news/business/news/bp-shell-oil-global-warming-5-degree-paris-climate-agreement-fossil-fuels-temperature-rise-a8022511.html

Extract: "Oil giants Shell and BP are planning for global temperatures to rise as much as 5°C by the middle of the century.
“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 #2111 on: January 25, 2018, 04:33:24 PM »
It is important to state the obvious, that in addition to consensus science's reticent behavior, denialists are well financed/organized and they actively manipulate the scientific publishing process in order to bias the pool of references considered by AR5 and soon by AR6.  Science should not be about a biased democracy of published literature, but rather about identification of the climate models that are most likely to project future climate change:

Title: "Murky world of 'science' journals a new frontier for climate deniers"

https://www.theguardian.com/environment/planet-oz/2018/jan/24/murky-world-of-science-journals-a-new-frontier-for-climate-deniers

Extract: "Deniers have found a platform in emerging publications that publish without rigorous review"
“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 #2112 on: January 25, 2018, 05:43:38 PM »
The linked reference explains that:

"The subduction and export of Subantarctic Mode Water (SAMW) supplies the upper limb of the overturning circulation and makes an important contribution to global heat, freshwater, carbon and nutrient budgets.  Upper ocean heat content has increased since 2006, helping to explain the so-called global warming hiatus between 1998 and 2014, with much of the ocean warming concentrated in extratropical latitudes of the Southern Hemisphere in close association with SAMW and Antarctic Intermediate Water (AAIW)."

This information helps readers to better understand the slow mode contribution to ECS that was clearly identified in the CMIP5 model projections by PH17 [Cristian Proistosescu and Peter J. Huybers (05 Jul 2017), "Slow climate mode reconciles historical and model-based estimates of climate sensitivity", Science Advances, Vol. 3, no. 7, e1602821, DOI: 10.1126/sciadv.1602821]

Gao et al (2018), "Recent wind-driven change in Subantarctic Mode Water and its impact on ocean heat storage", Nature Climate Change 8, 58-63, doi:10.1038/s41558-017-0022-8

http://www.nature.com/articles/s41558-017-0022-8

« Last Edit: January 25, 2018, 06:17:19 PM by AbruptSLR »
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AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #2113 on: January 25, 2018, 06:18:05 PM »
For reasons including decision maker's poor handling of climate change, the Bulletin of the Atomic Scientists has move the Doomsday clock 30 seconds closer to midnight:

Title: "IT IS 2 MINUTES TO MIDNIGHT"

https://thebulletin.org/clock/2018
&
https://thebulletin.org/sites/default/files/2018%20Doomsday%20Clock%20Statement.pdf

Extract: "In 2017, we saw reckless language in the nuclear realm heat up already dangerous situations and re-learned that minimizing evidence-based assessments regarding climate and other global challenges does not lead to better public policies."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

CDN_dude

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Re: Conservative Scientists & its Consequences
« Reply #2114 on: January 25, 2018, 11:57:14 PM »
It seems to me that we are pretty much screwed, if the conclusions of even some of these studies prove correct. For instance, at 1.5 C it has been theorized the permafrost reaches a threshold beyond which it will begin to release carbon equivalent to a doubling of pre-industrial CO2, all on its own (study here http://science.sciencemag.org/content/early/2013/02/20/science.1228729 as discussed in this thread https://forum.arctic-sea-ice.net/index.php/topic,36.0.html.) So an additional 280ppm, over maybe a few centuries (not sure of the timeline). That gives us a bare minimum of 680ppm. (~400 today plus the 280. And of course we have more than 400 baked in already for the near future). Now, if it also proves true that the increase in Arctic precipitation falls mostly as rain rather than snow, (post #2109) we get another increase equivalent to a doubling of carbon, so another 280. That puts us at 960ppm. So then take that absolutely conservative (assuming these two studies I have cited prove correct) baseline and add all of the other positive feedbacks you believe are likely.

Hoping someone can show where I have erred. The sheer number of additional positive feedbacks I'm not including here is frightening. Consider for instance that the conditions for survival of the plankton who produce 50% of our oxygen are also jeopardized by ocean acidification and hypoxia. So the question is, are we now too late?

AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #2115 on: January 26, 2018, 05:21:33 PM »
Hoping someone can show where I have erred. The sheer number of additional positive feedbacks I'm not including here is frightening. Consider for instance that the conditions for survival of the plankton who produce 50% of our oxygen are also jeopardized by ocean acidification and hypoxia. So the question is, are we now too late?

CDN_dude,

In general, terms like "we are pretty much screwed", are thought-stoppers that inhibit clear analyses of our situation. 

Certainly we are already committed to substantial damage from climate change, but many of the feedback mechanisms (such as Arctic Sea Ice loss, see reference below) that you cite might be avoided if policymakers take strong action now (such as SSP1, see the first image, indicating the use of negative emissions technology); however unlikely that might be.  Certainly, including emissions from permafrost degradation would take us into the Earth System Sensitivity, ESS, range (see the last two images), which many current policymakers choose to leave to future generations to address.

Best,
ASLR

Anne Laura Niederdrenk & Dirk Notz (25 January 2018), "Arctic sea ice in a 1.5 ° C warmer world", Geophysical Research Letters, DOI: 10.1002/2017GL076159 

http://onlinelibrary.wiley.com/doi/10.1002/2017GL076159/abstract?utm_content=bufferc4c17&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Extract: "We examine the seasonal cycle of Arctic sea ice in scenarios with limited future global warming. To do so, we analyse two sets of observational records that cover the observational uncertainty of Arctic sea-ice loss per degree of global warming. The observations are combined with 100 simulations of historical and future climate evolution from the MPI-ESM Grand Ensemble. Based on the high-sensitivity observations, we find that Arctic September sea ice is lost with low probability (P≈10%) for global warming of +1.5 ° C above pre-industrial levels and with very high probability (P>99%) for global warming of +2 ° C above pre-industrial levels. For the low-sensitivity observations, September sea ice is extremely unlikely to disappear for +1.5 ° C warming (P<<1%) and has low likelihood (P≈10%) to disappear even for +2 ° C global warming. For March, both observational records suggest a loss of 15% to 20% of Arctic sea-ice area for 1.5 ° C to 2 ° C global warming."
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CDN_dude

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Re: Conservative Scientists & its Consequences
« Reply #2116 on: January 26, 2018, 10:41:54 PM »
ASLR, thanks for your response. I agree I probably could have chosen my words more wisely there.

Also, an article from Michael Mann expressing some of his reservations about the methodology of the Cox study, as well as the way it was covered by the media: http://michaelmann.net/content/sensitive-topic
« Last Edit: January 26, 2018, 10:52:21 PM by CDN_dude »

AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #2117 on: January 27, 2018, 08:13:30 PM »
ASLR, thanks for your response. I agree I probably could have chosen my words more wisely there.

Also, an article from Michael Mann expressing some of his reservations about the methodology of the Cox study, as well as the way it was covered by the media: http://michaelmann.net/content/sensitive-topic

James Annan analyzed Cox et al (2018) and found that they underestimated the strength of the correlation between climate sensitivity and climate variability.  In the attached image (from the linked article) Annan correlates ECS vs the standard deviation of climate variability.  As climate is undeniably becoming rapidly more variable this implies that ECS is also becoming rapidly higher:

Title: "Cox et al part 3"

https://bskiesresearch.wordpress.com/2018/01/26/cox-et-al-part-3/

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AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #2118 on: January 27, 2018, 08:26:03 PM »
As Annan and Dessler have demonstrated that based on correlating model findings with several hundred years of observations, that ECS can increase relatively quickly with continued global warming; I repost the following linked reference that uses paleo data to remind us all how much ECS can change with climate state:

von der Heydt, A.S., Dijkstra, H.A., van de Wal, R.S.W. et al. (2016), "Lessons on Climate Sensitivity From Past Climate Changes", Curr Clim Change Rep 2: 148. https://doi.org/10.1007/s40641-016-0049-3

https://link.springer.com/article/10.1007/s40641-016-0049-3

Abstract: "Over the last decade, our understanding of climate sensitivity has improved considerably. The climate system shows variability on many timescales, is subject to non-stationary forcing and it is most likely out of equilibrium with the changes in the radiative forcing. Slow and fast feedbacks complicate the interpretation of geological records as feedback strengths vary over time. In the geological past, the forcing timescales were different than at present, suggesting that the response may have behaved differently. Do these insights constrain the climate sensitivity relevant for the present day? In this paper, we review the progress made in theoretical understanding of climate sensitivity and on the estimation of climate sensitivity from proxy records. Particular focus lies on the background state dependence of feedback processes and on the impact of tipping points on the climate system. We suggest how to further use palaeo data to advance our understanding of the currently ongoing climate change."

Caption for first image: "Published paleo-based values of S [CO 2 ,LI]  S[CO2,LI] (specific equilibrium climate sensitivity parameter caused by CO2 radiative forcing and corrected by variations in land-ice (LI) feedbacks) indicating its state dependence. Only studies published after the PALAEOSENS review paper [21] are considered. For comparison, the state-independent values from PALAEOSENS, and from the IPCC report [3], and the CMIP5 multi-model mean for present day [41] are also shown. All values of S [CO 2 ,LI]  S[CO2,LI] were given as mean (or most likely) ±1σ, apart from IPCC, which is the 90 % confidence (CF) range. Climate background states are given by ΔT from pre-industrial and are marked as estimated ranges (or ±2σ). In [42], further corrections for other slow feedbacks have been calculated, which has been ignored here, leading to different values of ΔT than published. To increase the clarity of the figure, the data-based results are visualised by colour-coded circles (mean values), while their uncertainties are combined in a cumulative probability density distribution (grey shading) assuming normal distributed values. Results based on climate models are shown by colour-coded squares (mean) including their uncertainties (bars). G glacial, IG interglacial, LE late Eocene, EE early Eocene, LP pre-PETM/late Paleocene, PETM Paleocene-Eocene thermal maximum. Reference numbers of the given citations: IPCC 2013 [3], PALAEOSENS 2012 [21], Andrews 2012 [41], Caballero 2013 [43] vdHeydt 2014 [20], Martinez-Boti 2015 [44] Köhler 2015 [32], Anagnoustou 2016 [42], Köhler 2016 [45], and Shaffer 2016 [46]"

Caption for the second image: "Schematic of the phase diagram of a climate model with two stable coexisting climate states. The shape of the S curve follows closely that discussed in [62, 63, 64]; see also [65]. The climate sensitivity parameter S is defined on each of the stable branches as the local slope of the global mean surface temperature T versus the (logarithm of) atmospheric pCO2 (cf. Eq. 8 ). Type I state dependence: When starting at point A (e.g. the pre-industrial climate), the temperature increase after a doubling of pCO2 (point B) is smaller than when starting from a colder climate (point C) on the same branch. Type II state dependence: When the initial pCO2 is the same as in point A, but the climate is initially on the cold branch (point D), a doubling of pCO2 results in a smaller temperature increase (point E) than if starting from point A and ending in point B. S becomes undefined at the transition points (open squares) between the two branches. The conditional climate sensitivity is equal to S for small perturbations (going from points D to E), but largely increases if the perturbation in CO2 is large enough to move the system from point D beyond the bifurcation point (blue open square) and jumps to the warm branch. Note that S is generally defined as a local gradient, while the 2xCO2 definition in the ECS may involve a perturbation too large for the linear assumption along the branch to be applicable"

See also:

Title: "Future relevant climate sensitivity (part deux)"
November 12, 2016/ gavin foster

http://www.thefosterlab.org/blog/2016/11/12/future-relevant-climate-sensitivity-part-deux

Extract: "The Friedrich et al (2016) study used a new empirical estimate of Surface Air Temperature (SAT) based on a compilation of Sea Surface Temperatures (as did Snyder recently) and a complete assessment of the processes “forcing” climate change over the last ~800 thousand years (e.g. CO2, land-ice albedo, and dust) to identify that climate sensitivity changed as a function of climate state: they found it was ~1.8 K per CO2 doubling when the Earth was substantially colder than today and ~5K per doubling when the Earth was only a little bit colder than the pre-industrial."
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AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #2119 on: January 27, 2018, 10:20:38 PM »
I am too cheap to buy the linked 10th Anniversary retrospective reference, but it is clearly worth investigating:

Yu Kosaka (2018), "Slow warming and the ocean see-saw", Nature Geoscience 11, 12–13 doi:10.1038/s41561-017-0038-8

https://www.nature.com/articles/s41561-017-0038-8

Abstract: "The slowdown in surface warming in the early twenty-first century has been traced to strengthening of the Pacific trade winds. The search for the causes identifies a planetary-scale see-saw of atmosphere and ocean between the Atlantic and Pacific basins."
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Re: Conservative Scientists & its Consequences
« Reply #2120 on: January 30, 2018, 05:54:18 PM »
The linked reference by Marvel et al (2018) indicates that estimates of ECS based on "… recent observations and energy balance models are biased low …".  Thus we can expect ECS to be hotter in the future than what we have experienced in modern times:

Kate Marvel, Robert Pincus, Gavin A. Schmidt & Ron L. Miller (29 January 2018), "Internal variability and disequilibrium confound estimates of climate sensitivity from observations", Geophysical Research Letters, DOI: 10.1002/2017GL076468 

http://onlinelibrary.wiley.com/doi/10.1002/2017GL076468/full

Abstract: "An emerging literature suggests that estimates of equilibrium climate sensitivity (ECS) derived from recent observations and energy balance models are biased low because models project more positive climate feedbacks in the far future. Here, we use simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5) to show that across models, ECS inferred from the recent historical period (1979-2005) is indeed almost uniformly lower than that inferred from simulations subject to abrupt increases in CO2 radiative forcing. However, ECS inferred from simulations in which sea surface temperatures are prescribed according to observations is lower still. ECS inferred from simulations with prescribed sea surface temperatures is strongly linked to changes to tropical marine low clouds. However, feedbacks from these clouds are a weak constraint on long-term model ECS. One interpretation is that observations of recent climate changes constitute a poor direct proxy for long term sensitivity."

Furthermore, Marvel's January 30, 2018, twitter feed indicates:

https://twitter.com/DrKateMarvel

Extract: "So the future is not the past. We're heading toward conditions we've never experienced. There may be no historical analog for what lies ahead.

We have reason to believe that this far future may be hotter, as the Southern Ocean starts to warm up and (perhaps) shed some of its reflective cloud cover.

And we seem to have gotten lucky on this front. We've experienced weird cool conditions in the tropical oceans that seem to have resulted in more low cloud cover, which reflected sun & cooled the planet.

This might have just been due to chance (and, at any rate, these weird cool waters have warmed up now). But it led us to an especially low estimate of eventual climate warming.

In summary: the past is not the future. Models don't "run hot". We got lucky. But our luck's run out. Happy Tuesday!"
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Re: Conservative Scientists & its Consequences
« Reply #2121 on: January 30, 2018, 06:33:17 PM »
Climate scientists report a dizzying number of climate sensitivity indices; which serves to confuse the general public (making denialist work that much easier).  Nevertheless, AR5 climate scientists do understand the differences between these indices and they still chose to use Transient climate response (TCR) at 140 years (T140) for projecting things like carbon budgets, because they incorrectly assumed that they were entitled to take climate sensitivity over a 140-year period to be linear.  However, the linked reference confirms that policymakers would be better served to use the true ECS for such decisions, as ECS includes nonlinear behavior and thus should increase with increasing global warming:

Michael R. Grose, Jonathan Gregory, Robert Colman & Timothy Andrews (29 January 2018), "What climate sensitivity index is most useful for projections?", Geophysical Research Letters, DOI: 10.1002/2017GL075742 

http://onlinelibrary.wiley.com/doi/10.1002/2017GL075742/abstract?utm_content=buffereda5c&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "Transient climate response (TCR), transient response at 140 years (T140) and equilibrium climate sensitivity (ECS) indices are intended as benchmarks for comparing the magnitude of climate response projected by climate models. It is generally assumed that TCR or T140 would explain more variability between models than ECS for temperature change over the 21st Century, since this timescale is the realm of transient climate change. Here we find that TCR explains more variability across CMIP5 than ECS for global temperature change since pre-industrial, for 50- or 100-year global trends up to the present, and for projected change under representative concentration pathways in regions of delayed warming such as the Southern Ocean. However, unexpectedly we find that ECS correlates higher than TCR for projected change from the present in the global mean and in most regions. This higher correlation doesn’t relate to aerosol forcing, and the physical cause requires further investigation."
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Re: Conservative Scientists & its Consequences
« Reply #2122 on: January 31, 2018, 10:39:20 PM »
The linked "… and Then There's Physics" article discusses some of the Marvel et al 2018 (see Reply #2120) findings about inferred ECS (see the first image).  However, I remind readers that Mark Richardson (2018) has pointed out the true ECS is about 43% higher than inferred ECS (see the second image, and Reply #2077):

Title: "Confounding ECS estimates"

https://andthentheresphysics.wordpress.com/2018/01/30/confounding-ecs-estimates/

Extract: "The abrupt 4xCO2 simulations produce a broad ECS distribution with the highest ECS best estimate. The historical produce a lower estimate which suggests that feedbacks might become stronger in the future. The simulations with prescribed sea surface temperatures and sea ice concentrations produce even lower ECS estimates.

This suggests that

recent decades appear to have experienced a pattern of sea surface temperatures that excited unusually negative feedbacks in tropical marine low clouds, leading to an even lower estimate of climate sensitivity than would have been expected under more usual historical conditions. "
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Re: Conservative Scientists & its Consequences
« Reply #2123 on: February 01, 2018, 04:40:33 PM »
In my opinion climate scientists should only make realistic assumptions for the SSP (or RCP) scenarios that they are analyzing; and should not apply 'magic thinking' to assume that negative emissions technologies will be a 'silver bullet':

Title: "Negative emissions have ‘limited potential’ to help meet climate goals"

https://www.carbonbrief.org/negative-emissions-have-limited-potential-to-help-meet-climate-goals

Extract: "The potential for using negative emissions technologies to help meet the goals of the Paris Agreement could be more “limited” than previously thought, concludes a new report by European science advisors.

Some of these techniques are already included by scientists in modelled “pathways” showing how global warming can be limited to between 1.5C and 2C above pre-industrial levels, which is the goal of the Paris Agreement.

However, the new report says there is no “silver bullet technology” that can be used to solve the problem of climate change, scientists said at a press briefing held in London.

Instead, “the primary focus must be on mitigation, on reducing emissions of greenhouse gases,” they added."
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Re: Conservative Scientists & its Consequences
« Reply #2124 on: February 01, 2018, 09:14:15 PM »
The linked article discusses some of the reasons that different recent studies [such as Brown & Caldeira (2017) vs Cox et al. (2018)] using similar methodologies can come out with such different 'emergent constraints' on the likely range for ECS.  These reasons range from: assumptions of liner response vs non-linear response; to parameter selection bias; statistical methodologies used, etc.

Per the orange posterior PDF shown in Fig. 1b of the attached image, the author finds a most likely value for ECS of 4.0C with a 66% probability range of from 2.9 to 4.5C, for the 29 models reviewed.  However (as the author notes) this analysis does not account for uncertainties in ECS associate with factors not considered by the models such as freshwater hosing (including a potential collapse of the WAIS this century) or a spike in methane emissions from thermokarst lakes of permafrost regions:

Title: "Statistical Inference with Emergent Constraints" by Tapio Schneider

http://climate-dynamics.org/statistical-inference-with-emergent-constraints/

Extract: "However, recent studies have arrived at different conclusions about likely ECS ranges. The different conclusions arise at least in part because the studies have systematically underestimated statistical uncertainties.

For example, Brown and Caldeira (2017) use fluctuations in Earth’s top-of-the-atmosphere (TOA) energy budget and their correlation with the response of climate models to increases in GHG concentrations to infer that ECS lies between 3 and 4.2 K with 50% probability, and most likely is 3.7 K. Assuming t statistics, this roughly corresponds to an ECS range that in IPCC parlance is considered likely (66% probability) between 2.8 and 4.5 K. By contrast, Cox et al. (2018) use fluctuations of the global-mean temperature and their correlation with the response of climate models to increases in GHG concentrations to infer that ECS likely lies between 2.2 and 3.4 K, and most likely is 2.8 K. These estimates are quite different from another, albeit not statistically significantly different. Why?

One reason is that the statistical inference procedure, which is similar in both studies, systematically underestimates uncertainties. One way to illustrate this is to look at the data Florent Brient and I analyzed in another emergent-constraint paper, which used fluctuations in TOA energy fluxes in marine tropical low-cloud (TLC) regions and their correlation with ECS (Brient and Schneider 2016, see blog post). [The data used in our paper are similar to those in Brown and Caldeira (2017).]

We in fact first tried to estimate ECS from the data in Figure 1a in the way described above, based on regression lines estimated by a robust regression method. But the uncertainties looked too small. So we developed an alternative inference procedure that does not suffer from some of the problems above. The idea is to arrive at a posterior PDF for ECS by weighting each model’s ECS by the likelihood of the model given the observations of the natural fluctuations. We used a measure from information theory, the Kullback–Leibler divergence or relative entropy, to estimate the logarithm of this model likelihood (Burnham and Anderson 2010). In this analysis, models such as numbers 2 and 3, which are inconsistent with observations, receive essentially zero weight—unlike in the regression-based analysis, they do not influence the final result. No linear relationship is assumed or implied, so models such as 7 receive a large weight because they are consistent with the data, although they lie far from any regression line. The resulting posterior PDF for ECS is shown by the orange line in Figure 1b. The most likely ECS value according to this analysis is 4.0 K—shifted upward relative to the regression estimate, toward the values in the cluster of models (around numbers 25 and 26) with relatively high ECS that are consistent with the observations. The likely ECS range stretches from 2.9 to 4.5 K. This is perhaps a disappointingly wide range. It is 50% wider than what the analysis based on linear regressions suggests, and it is not much narrower than what simple-minded equal weighting of raw climate models gives (gray line in Figure 1b). But it is a much more statistically defensible range.

Even such a more justifiable inference still suffers from several shortcomings. For example, it suffers from selection bias, and it treats the model ensemble as a random sample (which it is not). It also only weights models (see our previous discussion of this issue). ECS far outside the range of what current models produce will always come out as being very unlikely. Yet what is the probability that Earth may in fact have an ECS outside the range of the current models? It is quite possible that there are processes and feedbacks that all models miss, and the probability of that being the case may not be all that small, given, for example, the rudimentary state of modeling clouds and their climate feedback."
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Re: Conservative Scientists & its Consequences
« Reply #2125 on: February 02, 2018, 04:19:42 AM »

Instead, “the primary focus must be on mitigation, on reducing emissions of greenhouse gases,” they added."

Do you need to be a scientist to know this?  :o

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Re: Conservative Scientists & its Consequences
« Reply #2126 on: February 02, 2018, 05:27:05 PM »
The linked reference indicates that there is widespread negative freeboard on the thin sea ice, with thick snow cover, North of Svalbard.  This makes me wonder whether some of our current Arctic Sea Ice Extent numbers are less indicative of sea ice stability than consensus scientists are assuming as snow-ice does not sound very stable to me at all:

Anja Rösel, Polona Itkin, Jennifer King, Dmitry Divine, Caixin Wang, Mats A. Granskog, Thomas Krumpen & Sebastian Gerland (1 February 2018), "Thin Sea Ice, Thick Snow and Widespread Negative Freeboard Observed During N-ICE2015 North of Svalbard", JGR Oceans, DOI: 10.1002/2017JC012865 

http://onlinelibrary.wiley.com/doi/10.1002/2017JC012865/abstract?utm_content=bufferec27f&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "In recent years sea-ice conditions in the Arctic Ocean changed substantially towards a younger and thinner sea-ice cover. To capture the scope of these changes and identify the differences between individual regions, in situ observations from expeditions are a valuable data source. We present a continuous time series of in situ measurements from the N-ICE2015 expedition from January to June 2015 in the Arctic Basin north of Svalbard, comprising snow buoy and ice mass balance buoy data and local and regional data gained from electromagnetic induction (EM) surveys and snow probe measurements from four distinct drifts. The observed mean snow depth of 0.53 m for April to early June is 73% above the average value of 0.30 m from historical and recent observations in this region, covering the years 1955-2017. The modal total ice and snow thicknesses, of 1.6 m and 1.7 m measured with ground-based EM and airborne EM measurements in April, May and June 2015, respectively, lie below the values ranging from 1.8 m to 2.7 m, reported in historical observations from the same region and time of year.

The thick snow cover slows thermodynamic growth of the underlying sea ice. In combination with a thin sea-ice cover this leads to an imbalance between snow and ice thickness, which causes widespread negative freeboard with subsequent flooding and a potential for snow-ice formation. With certainty, 29% of randomly located drill holes on level ice had negative freeboard."
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Re: Conservative Scientists & its Consequences
« Reply #2127 on: February 03, 2018, 12:06:00 AM »
The linked article discusses some of the reasons that different recent studies [such as Brown & Caldeira (2017) vs Cox et al. (2018)] using similar methodologies can come out with such different 'emergent constraints' on the likely range for ECS.  These reasons range from: assumptions of liner response vs non-linear response; to parameter selection bias; statistical methodologies used, etc.

Per the orange posterior PDF shown in Fig. 1b of the attached image, the author finds a most likely value for ECS of 4.0C with a 66% probability range of from 2.9 to 4.5C, for the 29 models reviewed.  However (as the author notes) this analysis does not account for uncertainties in ECS associate with factors not considered by the models such as freshwater hosing (including a potential collapse of the WAIS this century) or a spike in methane emissions from thermokarst lakes of permafrost regions:
...

Here is a pdf of the 2016 reference that backs-up Schneider's comments:

Brient, F. and T. Schneider, 2016: Constraints on climate sensitivity from space-based measurements of low-cloud reflection. Journal of Climate, 29, 5821-5835.

http://climate-dynamics.org/wp-content/uploads/2015/08/Brient-Schneider-2016b.pdf

Abtract: "Physical uncertainties in global-warming projections are dominated by uncertainties about how the fraction of incoming shortwave radiation that clouds reflect will change as greenhouse gas concentrations rise. Differences in the shortwave reflection by low clouds over tropical oceans alone account for more than half of the variance of the equilibrium climate sensitivity (ECS) among climate models, which ranges from 2.1 to 4.7 K.  Space-based measurements now provide an opportunity to assess how well models reproduce temporal variations of this shortwave reflection on seasonal to interannual time scales. Here such space-based measurements are used to show that shortwave reflection by low clouds over tropical oceans decreases robustly when the underlying surface warms, for example, by 2(0.96 6 0.22)%K21 (90% confidence level) for deseasonalized variations. Additionally, the temporal covariance of low-cloud reflection with temperature in historical simulations with current climate models correlates strongly (r 5 20.67) with the models’ ECS. Therefore, measurements of temporal low-cloud variations can be used to constrain ECS estimates based on climate models. An information-theoretic weighting of climate models by how well they reproduce the measured deseasonalized covariance of shortwave cloud reflection with temperature yields a most likely ECS estimate around 4.0 K; an ECS below 2.3K becomes very unlikely (90% confidence)."
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Re: Conservative Scientists & its Consequences
« Reply #2128 on: February 05, 2018, 04:41:52 PM »
The linked reference finds that the actual ECS range is currently between 3.3C and 4.8C, and draws attention to the importance of correctly account for the influence of changed/changing SST patterns in addition to cloud feedback:

D. Paynter, T. L. Frölicher, L. W. Horowitz & L. G. Silvers (26 January 2018), "Equilibrium Climate Sensitivity Obtained from Multi-Millennial Runs of Two GFDL Climate Models", JGR Atmospheres, DOI: 10.1002/2017JD027885 

http://onlinelibrary.wiley.com/doi/10.1002/2017JD027885/abstract

Abstract: "Equilibrium climate sensitivity (ECS), defined as the long-term change in global mean surface air temperature in response to doubling atmospheric CO2, is usually computed from short atmospheric simulations over a mixed layer ocean, or inferred using a linear regression over a short-time period of adjustment. We report the actual ECS from multi-millenial simulations of two GFDL general circulation models (GCMs), ESM2M and CM3 of 3.3 K and 4.8 K, respectively. Both values are ~1 K higher than estimates for the same models reported in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change obtained by regressing the Earth's energy imbalance against temperature. This underestimate is mainly due to changes in the climate feedback parameter (−α) within the first century after atmospheric CO2 has stabilized. For both GCMs it is possible to estimate ECS with linear regression to within 0.3 K by increasing CO2 at 1% per year to doubling and using years 51-350 after CO2 is constant. We show that changes in −α differ between the two GCMs and are strongly tied to the changes in both vertical velocity at 500 hPa (ω500) and estimated inversion strength (EIS) that the GCMs experience during the progression towards the equilibrium. This suggests that while cloud physics parametrizations are important for determining the strength of −α, the substantially different atmospheric state resulting from a changed SST pattern may be of equal importance."
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Re: Conservative Scientists & its Consequences
« Reply #2129 on: February 05, 2018, 05:19:09 PM »
The linked reference finds "…no support for low values of ECS (below 2K) …":

Andrew Dessler & Piers Forster (2018), "An estimate of equilibrium climate sensitivity from interannual variability", doi:10.17605/OSF.IO/4ET67

https://eartharxiv.org/4et67/

Title: "Estimating the equilibrium climate sensitivity (ECS; the equilibrium warming in response to a doubling of CO2) from observations is one of the big problems in climate science. Using observations of interannual climate variations covering the period 2000 to 2017, we estimate ECS is likely 2.4-4.5 K (17-83% confidence interval), with a mode and median value of 2.9 and 3.3 K, respectively. Our analysis provides no support for low values of ECS (below 2 K) suggested by other analyses. The main uncertainty in our estimate is not observational uncertainty, but rather uncertainty in converting observations of short-term, mainly unforced climate variability to an estimate of the response of the climate system to long-term forced warming."

See also:

Title: "ECS from a modified energy balance approach"

https://andthentheresphysics.wordpress.com/2018/02/04/ecs-from-a-modified-energy-balance-approach/
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Re: Conservative Scientists & its Consequences
« Reply #2130 on: February 05, 2018, 05:38:07 PM »
Was just going to post that one. That's the paper that Dessler was referring to a few weeks ago.

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Re: Conservative Scientists & its Consequences
« Reply #2131 on: February 05, 2018, 05:46:56 PM »
Was just going to post that one. That's the paper that Dessler was referring to a few weeks ago.

I hope that Dessler works with Annan to update his ECS estimates based on the findings discussed in Reply #2117 (but I imagine that that would take 6 to 12 months).
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Re: Conservative Scientists & its Consequences
« Reply #2132 on: February 06, 2018, 06:52:47 PM »
While I do not believe that climate scientists mean to put the public at risk, over-selling the accuracy of their models is doing that anyway as illustrated by the linked article that indicts that ozone is declining in the lower stratosphere faster than the models predicted which is offsetting the projected ozone recovery following the Montreal Protocol.  I believe that climate scientist should emphasize 95% confidence level projections rather than mode values (which are frequently less than mean values due to skewed PDFs)

William T. Ball et al. (2018), "Continuous decline in lower stratospheric ozone offsets ozone layer recovery", Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2017-862

https://www.atmos-chem-phys.net/18/1379/2018/
&
https://www.atmos-chem-phys-discuss.net/acp-2017-862/acp-2017-862.pdf

Abstract" "Ozone forms in the Earth’s atmosphere from the photodissociation of molecular oxygen, primarily in the tropical stratosphere. It is then transported to the extratropics by the Brewer- Dobson circulation (BDC), forming a protective ‘ozone layer’ around the globe. Human emissions of halogen-containing ozone-depleting substances (hODSs) led to a decline in stratospheric ozone until they were banned by the Montreal Protocol (MP), and since 1998 ozone in the upper stratosphere shows a likely recovery. Total column ozone (TCO) measurements of ozone between the Earth’s surface and the top of the atmosphere, indicate that the ozone layer has stopped declining across the globe, but no clear increase has been observed at latitudes outside the polar regions (60o–90o). Here we report evidence from multiple satellite measurements that ozone in the lower stratosphere between 60oS and 60oN has declined continuously since 1985. We find that, even though upper stratospheric ozone is recovering in response to the MP, the lower stratospheric changes more than compensate for this, resulting in the conclusion that, globally (60oS–60oN), stratospheric column ozone (StCO) continues to deplete. We find that globally, TCO appears to not have decreased because tropospheric column ozone (TrCO) increases, likely the result of human activity and harmful to respiratory health, are compensating for the stratospheric decreases. The reason for the continued reduction of lower stratospheric ozone is not clear, models do not reproduce these trends, and so the causes now urgently need to be established. Reductions in lower stratospheric ozone trends may partly lead to a small reduction in the warming of the climate, but a reduced ozone layer may also permit an increase in harmful ultra-violet (UV) radiation at the surface and would impact human and ecosystem health."

See also:

Title: "Ozone at lower latitudes is not recovering, despite Antarctic ozone hole healing"

https://phys.org/news/2018-02-ozone-latitudes-recovering-antarctic-hole.html
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Re: Conservative Scientists & its Consequences
« Reply #2133 on: February 06, 2018, 07:14:49 PM »
Current estimates of mercury "… greatly underestimate Hg in permafrost soils …".  This is yet another reason to stop coming permafrost degradation:

Paul F. Schuster et al. (5 February 2018), "Permafrost Stores a Globally Significant Amount of Mercury", Geophysical Research Letters, DOI: 10.1002/2017GL075571 

http://onlinelibrary.wiley.com/doi/10.1002/2017GL075571/full

Abstract: "Changing climate in northern regions is causing permafrost to thaw with major implications for the global mercury (Hg) cycle. We estimated Hg in permafrost regions based on in situ measurements of sediment total mercury (STHg), soil organic carbon (SOC), and the Hg to carbon ratio (RHgC) combined with maps of soil carbon. We measured a median STHg of 43 ± 30 ng Hg g soil−1 and a median RHgC of 1.6 ± 0.9 μg Hg g C−1, consistent with published results of STHg for tundra soils and 11,000 measurements from 4,926 temperate, nonpermafrost sites in North America and Eurasia. We estimate that the Northern Hemisphere permafrost regions contain 1,656 ± 962 Gg Hg, of which 793 ± 461 Gg Hg is frozen in permafrost. Permafrost soils store nearly twice as much Hg as all other soils, the ocean, and the atmosphere combined, and this Hg is vulnerable to release as permafrost thaws over the next century. Existing estimates greatly underestimate Hg in permafrost soils, indicating a need to reevaluate the role of the Arctic regions in the global Hg cycle."
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Re: Conservative Scientists & its Consequences
« Reply #2134 on: February 07, 2018, 11:08:50 PM »
Science is not a democracy, so while it may be interesting that the IPCC cites ECS ranges from numerous climate models, in reality some model projections will prove more accurate than others, so if the HadGEM2-ES projection of a true ECS value of 4.55C is accurate (see the attached image & caption from the linked article) then we will all be in deep trouble within a few decades:

Title: "Guest post: A ‘new’ measurement of climate sensitivity?"

https://andthentheresphysics.wordpress.com/2018/01/17/guest-post-a-new-measurement-of-climate-sensitivity/

Caption: "Figure 1: Temperature change over 150 years in abrupt 4xCO2 simulations of four climate models. Black lines are a one-box fit with ECS and response time (τ) allowed to vary. Legend lists model name, true ECS and fit parameters"
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Re: Conservative Scientists & its Consequences
« Reply #2135 on: February 08, 2018, 11:37:39 PM »
The attached image from the linked 2008 reference provides a convenient means for estimating impacts if AR5 has underestimated ECS, for the indicate values of CO2e:

Reto Knutti & Gabriele C. Hegerl (2008), "The equilibrium sensitivity of the Earth's temperature to radiation changes", Nature Geoscience volume 1, pages 735–743, doi:10.1038/ngeo337

https://www.nature.com/articles/ngeo337
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Re: Conservative Scientists & its Consequences
« Reply #2136 on: February 10, 2018, 08:42:08 PM »
A bit more info on Mercury release that AbrubtSLR poster on the 6th... and thanks for all you do...

Researchers have discovered that thawing permafrost in the Northern Hemisphere stores twice as much mercury as the rest of the planet’s soils, atmosphere, and oceans. The finding has significant implications for human health and ecosystems worldwide.
In a new study, scientists measured mercury concentrations in cores of frozen ground—or permafrost—from Alaska and used the data to estimate how much mercury has been trapped in Northern Hemisphere permafrost since the last Ice Age.

They found that Northern Hemisphere permafrost regions contain 1,656 gigagrams of mercury (32 million gallons, or enough to fill 50 Olympic-sized swimming pools), making them the largest known reservoir of mercury on the planet. This amount is nearly twice as much mercury as all soils outside of the northern permafrost region, the ocean, and the atmosphere combined.

The researchers also found that of the 1,656 gigagrams of mercury, 863 gigagrams lie in the surface layer of soil that freezes and thaws each year (27 Olympic-sized swimming pools), and 793 gigagrams are frozen in permafrost (23 Olympic-sized swimming pools).

“This implies permafrost regions contain roughly 10 times the total human mercury emissions over the last 30 years,” said NSIDC scientist Kevin Schaefer, a co-author of the study published today in Geophysical Research Letters, a journal of the American Geophysical Union.

“Previous studies assumed little or no mercury in permafrost regions, but we find the opposite is true,” Schaefer said. “This completely changes our view of how mercury moves through the land and ocean.”

“This discovery is a game-changer,” said Paul Schuster, a hydrologist at the U.S. Geological Survey in Boulder, Colorado and lead author of the study. “We’ve quantified a pool of mercury that had not been done previously with confidence, and the results have profound implications for better understanding the global mercury cycle.”Permafrost is permanently frozen ground and occurs in approximately 22.79 million square kilometers, or about 24 percent of the Northern Hemisphere land surface surrounding the Arctic ocean.

Mercury naturally occurs in the Earth’s crust and typically enters the atmosphere through volcanic eruptions. The element cycles between the atmosphere and ocean quickly. However, mercury deposited on land from the atmosphere binds with organic matter in plants. After the plants die, soil microbes eat the dead organic matter, releasing the mercury back into the atmosphere or water.

In permafrost regions, however, the organic matter gets buried by sediment before it decays and becomes frozen into permafrost. Once frozen, the decay of organic matter stops, and the mercury remains trapped for thousands of years unless liberated by permafrost thaw.

“As long as the permafrost remains frozen, the mercury will stay trapped in the soil,” Schaefer said. Higher air temperatures due to climate change could thaw much of the existing permafrost, allowing the decay of organic matter to resume and releasing mercury that could affect Earth’s ecosystems. The released mercury can accumulate in aquatic and terrestrial food chains and cause harmful neurological and reproductive effects on animals.

“Although measurement of the rate of permafrost thaw was not part of this study, the thawing permafrost provides a potential for mercury to be released—that’s just physics.” Schuster said.

Climate models predict a 30 to 90 percent reduction in permafrost by 2100, depending on actual fuel emissions.

The researchers determined the total amount of mercury locked up in permafrost using field measurements. Between 2004 and 2012, the study authors drilled 13 permafrost soil cores at various sites in Alaska and measured the total amounts of mercury and carbon in each core. They selected sites with a diverse array of soil characteristics to best represent permafrost found around the entire Northern Hemisphere.Schuster, Schaefer, and their colleagues found their measurements were consistent with published data on mercury in non-permafrost and permafrost soils from thousands of other sites worldwide. They used their observed values to calculate the total amount of mercury stored in permafrost in the Northern Hemisphere and to create a map of soil mercury concentrations in the region.

The researchers believe their study gives policymakers and scientists new numbers to work with and calibrate their models as they begin to study this new phenomenon in more detail. The researchers intend to release another study modeling the release of mercury from permafrost due to climate change.

“Permafrost contains a huge amount of mercury,” Schaefer said. “We need to know how much mercury will get released from thawing permafrost, when it will get released

Bruce Steele

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Re: Conservative Scientists & its Consequences
« Reply #2137 on: February 10, 2018, 09:36:31 PM »
If the ECS is in the 4.5c range it should be rather sobering to compare the 6 C that at least partially contributed to the end Permian extinctions. Acidification and hypoxia also played their part.

Assessing ocean acidification and carbon cycle perturbations during the end-Permian extinction using boron isotopes
Published 7 February 2018   Science Leave a Comment
Tags: methods, paleo
The Permian-Triassic mass extinction represents the most severe environmental crisis in Earth’s history, which dictated the course for evolution of life until today. Volcanism from Siberian traps played a significant role involving a substantial input of relatively light carbon into the atmosphere leading to a combination of global warming by ~6°C, sporadic anoxia or euxinia, and ocean acidification. However, its detailed manifestation and environmental impact is yet to be fully understood. This lack of knowledge also extends to a better quantification of emitted and sequestered carbon budgets (cf. Gutjahr et al., 2017).



AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #2138 on: February 12, 2018, 02:27:01 AM »
If the scientists and the policymakers don't know how to address climate change, maybe the digital sector can make faster progress (at least to reduce the losses resulting from climate change):

Title: "The Fourth Industrial Revolution can lead us to a zero-carbon future - if we act now"

https://www.weforum.org/agenda/2018/01/how-we-can-direct-the-fourth-industrial-revolution-towards-a-zero-carbon-future/

Extract: "Earth is now 1.1℃ warmer owing to our emissions of greenhouse gases, and the latest scientific assessment, presented in Geophysical Research Letters, suggests that if we would get rid of all life-threatening air pollution, like black carbon, sulphates and nitrates, some of which lower temperatures, we would very likely bump up global temperatures another 0.5–1.1°C. The message is dire. One global bad - global warming – is camouflaged by another global bad – air pollution. This is a reminder that we are really, very late arrivals to the solution space.
...
How fast do we need to act? As a general rule of thumb, staying below 2°C above pre-industrial levels means halving emissions of greenhouse gases every decade if we want a high probability of success. We call this exponential pathway the Global Carbon Law, inspired by Moore’s Law in the IT industry – the observation that computers double in speed about every two years.
...
We now need Carbon Law thinking to go exponential. The solution is on the horizon. Later this year, San Francisco will host the most important event since the Paris Climate Agreement in 2015: the Global Climate Action Summit. Our aim for the summit is to move from incremental action to exponential and harness the power of the most innovative, disruptive part of the global economy – the digital sector."

Edit, see also:

B. H. Samset, M. Sand, C. J. Smith, S. E. Bauer, P. M. Forster, J. S. Fuglestvedt, S. Osprey & C.-F. Schleussner (24 January 2018), "Climate Impacts From a Removal of Anthropogenic Aerosol Emissions", Geophysical Research Letters, DOI: 10.1002/2017GL076079

http://onlinelibrary.wiley.com/doi/10.1002/2017GL076079/full

Abstract: "Limiting global warming to 1.5 or 2.0°C requires strong mitigation of anthropogenic greenhouse gas (GHG) emissions. Concurrently, emissions of anthropogenic aerosols will decline, due to coemission with GHG, and measures to improve air quality. However, the combined climate effect of GHG and aerosol emissions over the industrial era is poorly constrained. Here we show the climate impacts from removing present-day anthropogenic aerosol emissions and compare them to the impacts from moderate GHG-dominated global warming. Removing aerosols induces a global mean surface heating of 0.5–1.1°C, and precipitation increase of 2.0–4.6%. Extreme weather indices also increase. We find a higher sensitivity of extreme events to aerosol reductions, per degree of surface warming, in particular over the major aerosol emission regions. Under near-term warming, we find that regional climate change will depend strongly on the balance between aerosol and GHG forcing."
« Last Edit: February 12, 2018, 02:37:35 AM by AbruptSLR »
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Sigmetnow

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Re: Conservative Scientists & its Consequences
« Reply #2139 on: February 13, 2018, 09:38:00 PM »
...
How fast do we need to act?
...

“That we don't spend a significant part of every public discussion, every day, debating what to do about our planetary crisis is a moral failure for which future generations are unlikely to forgive us. ”
- Alex Steffen

https://twitter.com/AlexSteffen/status/963135964213256192
(Photo at the link.)
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AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #2140 on: February 14, 2018, 04:37:39 PM »
Emissions from future Amazon wildfires represents a larger concern than previously appreciated:

Luiz E. O. C. Aragão et al. (2018), "21st Century drought-related fires counteract the decline of Amazon deforestation carbon emissions", Nature Communications, volume 9, Article number: 536, doi:10.1038/s41467-017-02771-y

http://www.nature.com/articles/s41467-017-02771-y

Abstract: "Tropical carbon emissions are largely derived from direct forest clearing processes. Yet, emissions from drought-induced forest fires are, usually, not included in national-level carbon emission inventories. Here we examine Brazilian Amazon drought impacts on fire incidence and associated forest fire carbon emissions over the period 2003–2015. We show that despite a 76% decline in deforestation rates over the past 13 years, fire incidence increased by 36% during the 2015 drought compared to the preceding 12 years. The 2015 drought had the largest ever ratio of active fire counts to deforestation, with active fires occurring over an area of 799,293 km2. Gross emissions from forest fires (989 ± 504 Tg CO2 year−1) alone are more than half as great as those from old-growth forest deforestation during drought years. We conclude that carbon emission inventories intended for accounting and developing policies need to take account of substantial forest fire emissions not associated to the deforestation process."
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AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #2141 on: February 26, 2018, 11:41:12 PM »
The linked reference indicates that tropical forest fragmentation has reached a tipping point, where further deforestation could lead to an abrupt increase in more forest fragmentation, which would act as a positive feedback for climate change:

Franziska Taubert et al. (2018), "Global patterns of tropical forest fragmentation", Nature, Vol. 554, doi:10.1038/nature25508

http://www.nature.com/articles/nature25508.epdf?referrer_access_token=0xze7sJoMmrvS4aEJkuNUNRgN0jAjWel9jnR3ZoTv0NsgaTJJtpIei2QYhbSoi5uSLEV2dfbIf3yOW9QL0i4HJVijbcj1xqlzs4MRgFjpM1VnJFSWwc6fBchuixMui9azJEIRIRqwt2qP0izxof7Z_g2io8DcBGKFJvIwgrd9FaqGS4Usvhj1bofPLKV-plvDp9lx1nf637CxuWj0kLap4jfjIpjwJg8nD6cbx3RLc_igkdFroiyE-v9VgF_oNITNKHTiQGQmNT4ApxWc1pvlQ%3D%3D&tracking_referrer=news.mongabay.com
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AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #2142 on: February 26, 2018, 11:46:59 PM »
The linked article discusses evidence that the Arctic may be near to reaching a tipping point:

Title: "Has the Arctic Finally Reached a Tipping Point?"
https://earther.com/has-the-arctic-finally-reached-a-tipping-point-1823276247

Extract: "“The Holocene climate system is unraveling,” Jason Box, an ice researcher at the Danish Meteorological Institute, told Earther in an email. “We should not be surprised if/when ongoing de-glaciation of the Arctic combined with global (and Arctic) atmospheric heating and humidification causes climate shifts that appear to be step changes.”"
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AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #2143 on: February 27, 2018, 07:07:14 PM »
The linked article indicates that human-induced land use change has a more positive feedback than currently recognized by consensus science:

Gries, T., Redlin, M. & Ugarte, J.E. (2018), "Human-induced climate change: the impact of land-use change", Theor Appl Climatol, https://doi.org/10.1007/s00704-018-2422-8

https://rd.springer.com/article/10.1007%2Fs00704-018-2422-8?utm_content=bufferb6d5d&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "For hundreds of years, human activity has modified the planet’s surface through land-use practices. Policies and decisions on how land is managed and land-use changes due to replacement of forests by agricultural cropping and grazing lands affect greenhouse gas emissions. Agricultural management and agroforestry and the resulting changes to the land surface alter the global carbon cycle as well as the Earth’s surface albedo, both of which in turn change the Earth’s radiation balance. This makes land-use change the second anthropogenic source of climate change after fossil fuel burning. However, the scientific research community has so far not been able to identify the direction and magnitude of the global impact of land-use change. This paper examines the effects of net carbon flux from land-use change on temperature by applying Granger causality and error correction models. The results reveal a significant positive long-run equilibrium relationship between land-use change and the temperature series as well as an opposing short-term effect such that land-use change tends to lead to global warming; however, a rise in temperature causes a decline in land-use change."
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AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #2144 on: March 01, 2018, 12:19:59 AM »
The linked reference provide evidence that the 'permafrost carbon feedback' may becoming increasingly positive, with continuing climate change:

J F Dean et al. (2018), "Abundant pre-industrial carbon detected in Canadian Arctic headwaters: implications for the permafrost carbon feedback", Environmental Research Letters, Volume 13, Number 3, https://doi.org/10.1088/1748-9326/aaa1fe

http://iopscience.iop.org/article/10.1088/1748-9326/aaa1fe/meta

Abstract: "Mobilization of soil/sediment organic carbon into inland waters constitutes a substantial, but poorly-constrained, component of the global carbon cycle. Radiocarbon (14C) analysis has proven a valuable tool in tracing the sources and fate of mobilized carbon, but aquatic 14C studies in permafrost regions rarely detect 'old' carbon (assimilated from the atmosphere into plants and soil prior to AD1950). The emission of greenhouse gases derived from old carbon by aquatic systems may indicate that carbon sequestered prior to AD1950 is being destabilized, thus contributing to the 'permafrost carbon feedback' (PCF). Here, we measure directly the 14C content of aquatic CO2, alongside dissolved organic carbon, in headwater systems of the western Canadian Arctic—the first such concurrent measurements in the Arctic. Age distribution analysis indicates that the age of mobilized aquatic carbon increased significantly during the 2014 snow-free season as the active layer deepened. This increase in age was more pronounced in DOC, rising from 101–228 years before sampling date (a 120%–125% increase) compared to CO2, which rose from 92–151 years before sampling date (a 59%–63% increase). 'Pre-industrial' aged carbon (assimilated prior to ~AD1750) comprised 15%–40% of the total aquatic carbon fluxes, demonstrating the prevalence of old carbon to Arctic headwaters. Although the presence of this old carbon is not necessarily indicative of a net positive PCF, we provide an approach and baseline data which can be used for future assessment of the PCF."
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AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #2145 on: March 01, 2018, 12:31:28 AM »
The linked reference indicates that the continuing deforestation of mangrove forests is contributing to net CO₂ emissions:

Stuart E. Hamilton & Daniel A. Friess, (2018), "Global carbon stocks and potential emissions due to mangrove deforestation from 2000 to 2012", Nature Climate Change, volume 8, pages240–244, doi:10.1038/s41558-018-0090-4

http://www.nature.com/articles/s41558-018-0090-4

Abstract: "Mangrove forests store high densitie of organic carbon, which, when coupled with high rates of deforestation, means that mangroves have the potential to contribute substantially to carbon emissions. Consequently, mangroves are strong candidates for inclusion in nationally determined contributions (NDCs) to the United Nations Framework Convention on Climate Change (UNFCCC), and payments for ecosystem services (PES) programmes that financially incentivize the conservation of forested carbon stocks. This study quantifies annual mangrove carbon stocks from 2000 to 2012 at the global, national and sub-national levels, and global carbon emissions resulting from deforestation over the same time period. Globally, mangroves stored 4.19 Pg of carbon in 2012, with Indonesia, Brazil, Malaysia and Papua New Guinea accounting for more than 50% of the global stock. 2.96 Pg of the global carbon stock is contained within the soil and 1.23 Pg in the living biomass. Two percent of global mangrove carbon was lost between 2000 and 2012, equivalent to a maximum potential of 316,996,250 t of CO2 emissions."
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AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #2146 on: March 01, 2018, 06:27:43 PM »
Recent findings cited in prior posts have clearly indicated that high climate variability is closely correlated with high climate sensitivity.  The attached map from Climate Central gives an idea of just how widespread extreme temperature events are around the world:
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gerontocrat

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Re: Conservative Scientists & its Consequences
« Reply #2147 on: March 01, 2018, 06:35:22 PM »
Recent findings cited in prior posts have clearly indicated that high climate variability is closely correlated with high climate sensitivity.  The attached map from Climate Central gives an idea of just how widespread extreme temperature events are around the world:

I wonder if a similar image exists for low temperature extremes, given that the decay of the polar vortex allows greater frequency of very cold Arctic air to escape into the power latitudes.
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AbruptSLR

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Re: Conservative Scientists & its Consequences
« Reply #2148 on: March 01, 2018, 06:57:13 PM »
Recent findings cited in prior posts have clearly indicated that high climate variability is closely correlated with high climate sensitivity.  The attached map from Climate Central gives an idea of just how widespread extreme temperature events are around the world:

I wonder if a similar image exists for low temperature extremes, given that the decay of the polar vortex allows greater frequency of very cold Arctic air to escape into the power latitudes.

This image includes both high and low temperature extreme events.
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Re: Conservative Scientists & its Consequences
« Reply #2149 on: March 01, 2018, 07:22:04 PM »
Recent findings cited in prior posts have clearly indicated that high climate variability is closely correlated with high climate sensitivity.  The attached map from Climate Central gives an idea of just how widespread extreme temperature events are around the world:

I wonder if a similar image exists for low temperature extremes, given that the decay of the polar vortex allows greater frequency of very cold Arctic air to escape into the power latitudes.

This image includes both high and low temperature extreme events.

A lot of them in NA.