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Author Topic: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)  (Read 45715 times)

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #500 on: January 22, 2019, 12:15:44 AM »
The linked article cites new PNAS findings that ice mass loss from the GIS is accelerating faster than consensus climate science previously assumed:

Title: "Greenland's ice melting faster than scientists previously thought – study"

https://www.theguardian.com/world/2019/jan/21/greenland-ice-melting-faster-than-scientists-previously-thought-study

Extract: "Greenland is melting faster than scientists previously thought, with the pace of ice loss increasing four-fold since 2003, new research has found."
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Klondike Kat

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #501 on: January 22, 2019, 12:49:43 AM »
Yes, the mass loss accelerated from 2003 up until 2012.  However, since then it has decelerated dramatically, to the point where it may actually be gained mass.

http://sciencenordic.com/how-greenland-ice-sheet-fared-2018

https://nsidc.org/greenland-today/

"Exceptional winter snow accumulation and heavy, summer snowfall, drove the net snow input mass to 130 billion tons above the 1981 to 2010 average. This was followed by a near-average melt and runoff period, resulting in a large net mass gain for the ice sheet in 2018 of 150 billion tons. This is the largest net gain from snowfall since 1996, and the highest snowfall since 1972. However, several major glaciers now flow significantly faster than in these earlier years. The net change in mass of the ice sheet overall, including this higher discharge of ice directly into the ocean, is not clear at this point but may be a smaller loss or even a small gain. This is similar to our assessment for 2017, and in sharp contrast to the conditions for the preceding decade."

sidd

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #502 on: January 22, 2019, 05:53:32 AM »
Anyone got the doi for the Bevis paper on GIS ? i searched the PNAS site but it didnt appear for 2019

Re: Wolf: I think i agree with Wolf's results on CO2 at high concentrations increasing sensitivity. What I don't trust is the cloud albedo feedback bit.

sidd

Wherestheice

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #503 on: January 22, 2019, 08:13:56 AM »
Anyone got the doi for the Bevis paper on GIS ? i searched the PNAS site but it didnt appear for 2019

Re: Wolf: I think i agree with Wolf's results on CO2 at high concentrations increasing sensitivity. What I don't trust is the cloud albedo feedback bit.

sidd

Wouldn't a warmer planet cause the cloud albedo to lessen, due to there being more water vapor in the atmosphere, causing clouds to have more rain droplets, therefore making them darker. This isn't my field of study, but that makes sense to me
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Phil42

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #504 on: January 22, 2019, 12:50:23 PM »
I always understood the total Greenland (or generally any) ice sheet mass change in a year to mainly be a result of the amount snowfall, melt and calving:
mass change = gain from snowfall - loss from melt - loss through calving
Is this correct?

https://climate.nasa.gov/vital-signs/ice-sheets/

The linked page contains a graph that has data until June 2017 and shows an ongoing downward trend in the Greenland total ice sheet mass.

Yes, the mass loss accelerated from 2003 up until 2012.  However, since then it has decelerated dramatically, to the point where it may actually be gained mass.

http://sciencenordic.com/how-greenland-ice-sheet-fared-2018

https://nsidc.org/greenland-today/

"Exceptional winter snow accumulation and heavy, summer snowfall, drove the net snow input mass to 130 billion tons above the 1981 to 2010 average. This was followed by a near-average melt and runoff period, resulting in a large net mass gain for the ice sheet in 2018 of 150 billion tons. This is the largest net gain from snowfall since 1996, and the highest snowfall since 1972. However, several major glaciers now flow significantly faster than in these earlier years. The net change in mass of the ice sheet overall, including this higher discharge of ice directly into the ocean, is not clear at this point but may be a smaller loss or even a small gain. This is similar to our assessment for 2017, and in sharp contrast to the conditions for the preceding decade."

Do I understand this analysis correctly that this downward trend could have been broken in 2017 and 2018? That would be great news.

Klondike Kat

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #505 on: January 22, 2019, 04:35:34 PM »
I always understood the total Greenland (or generally any) ice sheet mass change in a year to mainly be a result of the amount snowfall, melt and calving:
mass change = gain from snowfall - loss from melt - loss through calving
Is this correct?

https://climate.nasa.gov/vital-signs/ice-sheets/

The linked page contains a graph that has data until June 2017 and shows an ongoing downward trend in the Greenland total ice sheet mass.

Yes, the mass loss accelerated from 2003 up until 2012.  However, since then it has decelerated dramatically, to the point where it may actually be gained mass.

http://sciencenordic.com/how-greenland-ice-sheet-fared-2018

https://nsidc.org/greenland-today/

"Exceptional winter snow accumulation and heavy, summer snowfall, drove the net snow input mass to 130 billion tons above the 1981 to 2010 average. This was followed by a near-average melt and runoff period, resulting in a large net mass gain for the ice sheet in 2018 of 150 billion tons. This is the largest net gain from snowfall since 1996, and the highest snowfall since 1972. However, several major glaciers now flow significantly faster than in these earlier years. The net change in mass of the ice sheet overall, including this higher discharge of ice directly into the ocean, is not clear at this point but may be a smaller loss or even a small gain. This is similar to our assessment for 2017, and in sharp contrast to the conditions for the preceding decade."

Do I understand this analysis correctly that this downward trend could have been broken in 2017 and 2018? That would be great news.

Yes, you are understanding correctly.  Whether this is the start of a new trend or just a temporary reprieve remains to be seen.  So, I would not start celebrating soon.

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #506 on: January 22, 2019, 04:41:15 PM »
Anyone got the doi for the Bevis paper on GIS ? i searched the PNAS site but it didnt appear for 2019

Re: Wolf: I think i agree with Wolf's results on CO2 at high concentrations increasing sensitivity. What I don't trust is the cloud albedo feedback bit.

sidd

Michael Bevis el al., "Accelerating changes in ice mass within Greenland, and the ice sheet's sensitivity to atmospheric forcing," PNAS (2019). www.pnas.org/cgi/doi/10.1073/pnas.1806562116
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #507 on: January 22, 2019, 04:47:39 PM »
...
Scanning several papers on the PETM again I see estimates on the rate of emissions and warming vary significantly, so it's hard to have much confidence in any particular estimate, whether it was 10x slower than currently, 100x slower, or maybe even as fast as currently.

...

The linked reference discusses how lessons learned from studying paleo 'hyperthermal' events from the past 300 million years can be used to help calibrate models of our current 'Anthropocene hyperthermal' event.  One such lesson learned is that many key negative feedback mechanisms occur over periods longer than one thousand years, while many key positive forcing mechanisms occur over shorter time frames; thus the observed effective climate sensitivity from paleo-hyperthermal events likely underestimate the effective climate sensitivity for our current 'Anthropogenic hyperthermal' event:

Gavin L. Foster, Pincelli Hull, Daniel J. Lunt, James C. Zachos (3 September 2018), "Placing our current ‘hyperthermal’ in the context of rapid climate change in our geological past", Philosophical Transactions of the Royal Society A, DOI: 10.1098/rsta.2017.0086

http://rsta.royalsocietypublishing.org/content/376/2130/20170086

Extract: "These modern rates of carbon emission likely dwarf the rate seen during the onset of the PETM by a factor of 10 or so. If humanity's fossil fuel use is not tackled rapidly through the development of a low-carbon economy, we face the possibility of emitting as much carbon as was released during the PETM but in a fraction of the time (0.5 versus 50–100 thousand years). The magnitude of atmospheric CO2 change (and hence the magnitude of warming, anoxia and ocean acidification) that occurs following any carbon addition to the Earth system is a function of rate, due to the time scales of a number of key negative feedbacks. Why the Palaeozoic hyperthermals are associated with significantly greater extinction rate is currently not known. However, a consensus is emerging that it is the extreme heat and anoxia that are the likely ‘kill mechanisms’ [50]. Given that the rate of carbon addition during our ‘anthropogenic hyperthermal’ eclipses that of the PETM, at the very least we are likely looking at a potential future with a more severe impact of life on Earth than any climate change event in the last 56 Myr. Exactly how severe, however, remains perhaps one of the most pressing of the ‘unknown unknowns’."
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #508 on: January 22, 2019, 04:58:15 PM »


Next, I provide links to Jagniecki et al. (2015) (and an associated article); indicating that early Eocene climatic optimum (EECO) conditions (with an equable climate) may have occurred with atmospheric CO₂ concentrations between 680ppm and 1260ppm (see the attached image); and that under such conditions the effective climate sensitivity (ESS) may have been twice that previously assumed by Royer et al (2012) …

Jagniecki,Elliot A. et al. (2015), "Eocene atmospheric CO2from the nahcolite proxy", Geology, http://dx.doi.org/10.1130/G36886.1

...

There is a reason that equable conditions occurred repeatedly in Earth's past, and the current generation of ESMs have failed to identify those reasons.  For instance, 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."
“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: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #509 on: January 22, 2019, 05:25:38 PM »
The attached image, per sidd, comes from Kidder et al (2004), and shows how (for paleo conditions) equable atmospheric patterns occur and how in an equable atmosphere (hothouse conditions) heat from the tropics is more easily carried through the atmosphere directly to the poles.  Furthermore, it is easier for global warming to flip the NH atmosphere into an equable pattern than the SH; thus if/when the WAIS collapses (say beginning in 2040), this event might conceivable put the NH atmosphere into an equable pattern by say 2100, while leaving the SH atmosphere in its current pattern.

See also:

Kidder, D. L., & Worsley, T. R. (2010). Phanerozoic Large Igneous Provinces (LIPs), HEATT (Haline Euxinic Acidic Thermal Transgression) episodes, and mass extinctions. Palaeogeography, Palaeoclimatology, Palaeoecology, 295(1-2), 162–191. doi:10.1016/j.palaeo.2010.05.036

“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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b_lumenkraft

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #510 on: January 22, 2019, 05:48:31 PM »
Local drivers of amplified Arctic warming

Quote
A new international research study on the cause of Arctic amplification published this week in the journal Nature Climate Change shows that local greenhouse gas concentrations, and Arctic climate feedbacks outweigh other processes. Using complex computer simulations, the scientists were able to disprove previously suggested hypotheses, that emphasized the role of transport of heat from the tropics to the poles as one of the key contributors to the amplified warming in the Arctic.
"Our study clearly shows that local carbon dioxide forcing and polar feedbacks are most effective in Arctic amplification compared to other processes," said corresponding author Malte Stuecker, project leader at the IBS Center for Climate Physics (ICCP) in Busan, South Korea.

Link to Article >> https://phys.org/news/2018-11-local-drivers-amplified-arctic.html

Abstract:


Quote
The surface temperature response to greenhouse gas forcing displays a characteristic pattern of polar-amplified warming1,2,3,4,5, particularly in the Northern Hemisphere. However, the causes of this polar amplification are still debated. Some studies highlight the importance of surface-albedo feedback6,7,8, while others find larger contributions from longwave feedbacks4,9,10, with changes in atmospheric and oceanic heat transport also thought to play a role11,12,13,14,15,16. Here, we determine the causes of polar amplification using climate model simulations in which CO2 forcing is prescribed in distinct geographical regions, with the linear sum of climate responses to regional forcings replicating the response to global forcing. The degree of polar amplification depends strongly on the location of CO2 forcing. In particular, polar amplification is found to be dominated by forcing in the polar regions, specifically through positive local lapse-rate feedback, with ice-albedo and Planck feedbacks playing subsidiary roles. Extra-polar forcing is further shown to be conducive to polar warming, but given that it induces a largely uniform warming pattern through enhanced poleward heat transport, it contributes little to polar amplification. Therefore, understanding polar amplification requires primarily a better insight into local forcing and feedbacks rather than extra-polar processes.

Link to Study >> https://www.nature.com/articles/s41558-018-0339-y

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #511 on: January 22, 2019, 06:40:12 PM »
Local drivers of amplified Arctic warming

Quote
A new international research study on the cause of Arctic amplification published this week in the journal Nature Climate Change shows that local greenhouse gas concentrations, and Arctic climate feedbacks outweigh other processes. Using complex computer simulations, the scientists were able to disprove previously suggested hypotheses, that emphasized the role of transport of heat from the tropics to the poles as one of the key contributors to the amplified warming in the Arctic.
"Our study clearly shows that local carbon dioxide forcing and polar feedbacks are most effective in Arctic amplification compared to other processes," said corresponding author Malte Stuecker, project leader at the IBS Center for Climate Physics (ICCP) in Busan, South Korea.

...

Reposted from Reply #419:

"…

Regarding the future, you need to bear in mind that Stuecker et al (2018) are talking about observed Arctic Amplification, and you need to bear in mind that global warming is only now beginning to have a significant impact on the ENSO cycle (and in a few decades on summer Arctic Sea Ice extent and the associated flip in the ice-albedo feedback), and as cited in Reply #397:

"The linked reference indicates that the warming of the North Pacific subpolar waters is likely the most important feedback for driving enhanced Arctic Amplification with continued global warming, and the attached image demonstrates how the North Pacific subpolar water can be warmed directly by atmospheric telecommunication of energy from the Tropical Pacific.  If show this indicates that the CMIP5 projections likely underestimate ECS, and as ice-climate feedback would likely accelerate warming the Tropical Pacific, it is likely that CMIP6 projections will also underestimate ECS as these models do not consider ice-cliff failures or hydrofracturing:"

Summer Praetorius, Maria Rugenstein, Geeta Persad, Ken Caldeira. Global and Arctic climate sensitivity enhanced by changes in North Pacific heat flux. Nature Communications, 2018; 9 (1) DOI: 10.1038/s41467-018-05337-8

https://www.nature.com/articles/s41467-018-05337-8

Thus by 2040 Arctic Amplification will likely be significantly higher that today due to increased water vapor migration from the North Pacific (associated with the increased telecommunication of Tropical Pacific energy due to increased El Nino frequencies), and decreased ice-albedo, as well as the lapse rate feedback cited by Stuecker et al (2018)."
« Last Edit: January 22, 2019, 07:29:37 PM by AbruptSLR »
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sidd

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #512 on: January 22, 2019, 09:16:27 PM »
The Bevis paper is interesting. They use GIA as well as a bunch of other observations to estimate GIS mass waste. One  takeaway is that in the twentieth century, atmosphere had not warmed enuf for NAO variation to induce mass waste events thru increased SMB. But this century it is.

"Since 2000, the NAO has worked in concert with global warming to trigger major increases in summertime runoff. Before 2000, the air was too cool for the NAO to do the same. In a decade or two, global warming will be able to drive 2012 levels of runoff with little or no assistance from the NAO. In the shorter term, we can infer that the next time NAO turns strongly negative, SMB will trend strongly negative over west and especially southwest Greenland ..."


They also point out several interesting things. The pause after 2012 was due to NAO :

"Van Angelen et al. (13) concluded that if the sNAO switched back to positive values after 2012, then surface mass balance (SMB) might partially recover. Indeed, not only did the June to August (JJA) and June to September (JJAS) NAO indices turn positive in 2013, but the change in each of these sNAO indices from 2012 to 2013 was the single biggest interannual change recorded since 1950 (Fig. 1 F and G and SI Appendix, Fig. S7). Furthermore, when the sNAO index again turned strongly negative in 2015, significant ice loss was reestablished (Fig. 1 B and E), and the Pause had ended."

Another point they make is that glacier discharge is governed by shallow marine warmth:

"future warming of the shallow ocean is expected to have its largest impact, via DMB (33, 34), in southeast and northwest Greenland"

But the last is not the focus of the paper.

Open access, read all about it:

doi: 10.1073/pnas.1806562116

sidd

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #513 on: January 22, 2019, 09:48:34 PM »
Per the attached image & linked sources, fossil CO₂ emissions in 2018 reached about 37 Billion tons:

Title: "Global Carbon Budget 2018"

http://www.globalcarbonproject.org/global/images/carbonbudget/Infographic_Emissions2018.png

See also:

Le Quéré, C., Andrew, R. M., Friedlingstein, P., Sitch, S., Hauck, J., Pongratz, J., Pickers, P. A., Korsbakken, J. I., Peters, G. P., Canadell, J. G., Arneth, A., Arora, V. K., Barbero, L., Bastos, A., Bopp, L., Chevallier, F., Chini, L. P., Ciais, P., Doney, S. C., Gkritzalis, T., Goll, D. S., Harris, I., Haverd, V., Hoffman, F. M., Hoppema, M., Houghton, R. A., Hurtt, G., Ilyina, T., Jain, A. K., Johannessen, T., Jones, C. D., Kato, E., Keeling, R. F., Goldewijk, K. K., Landschützer, P., Lefèvre, N., Lienert, S., Liu, Z., Lombardozzi, D., Metzl, N., Munro, D. R., Nabel, J. E. M. S., Nakaoka, S.-I., Neill, C., Olsen, A., Ono, T., Patra, P., Peregon, A., Peters, W., Peylin, P., Pfeil, B., Pierrot, D., Poulter, B., Rehder, G., Resplandy, L., Robertson, E., Rocher, M., Rödenbeck, C., Schuster, U., Schwinger, J., Séférian, R., Skjelvan, I., Steinhoff, T., Sutton, A., Tans, P. P., Tian, H., Tilbrook, B., Tubiello, F. N., van der Laan-Luijkx, I. T., van der Werf, G. R., Viovy, N., Walker, A. P., Wiltshire, A. J., Wright, R., Zaehle, S., and Zheng, B.: Global Carbon Budget 2018, Earth Syst. Sci. Data, 10, 2141-2194, https://doi.org/10.5194/essd-10-2141-2018, 2018.

https://www.earth-syst-sci-data.net/10/2141/2018/
&
https://www.earth-syst-sci-data.net/10/2141/2018/essd-10-2141-2018.pdf

Abstract
Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere – the “global carbon budget” – is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe data sets and methodology to quantify the five major components of the global carbon budget and their uncertainties. Fossil CO2 emissions (EFF) are based on energy statistics and cement production data, while emissions from land use and land-use change (ELUC), mainly deforestation, are based on land use and land-use change data and bookkeeping models. Atmospheric CO2 concentration is measured directly and its growth rate (GATM) is computed from the annual changes in concentration. The ocean CO2 sink (SOCEAN) and terrestrial CO2 sink (SLAND) are estimated with global process models constrained by observations. The resulting carbon budget imbalance (BIM), the difference between the estimated total emissions and the estimated changes in the atmosphere, ocean, and terrestrial biosphere, is a measure of imperfect data and understanding of the contemporary carbon cycle. All uncertainties are reported as ±1σ. For the last decade available (2008–2017), EFF was 9.4±0.5 GtC yr−1, ELUC 1.5±0.7 GtC yr−1, GATM 4.7±0.02 GtC yr−1, SOCEAN 2.4±0.5 GtC yr−1, and SLAND 3.2±0.8 GtC yr−1, with a budget imbalance BIM of 0.5 GtC yr−1 indicating overestimated emissions and/or underestimated sinks. For the year 2017 alone, the growth in EFF was about 1.6 % and emissions increased to 9.9±0.5 GtC yr−1. Also for 2017, ELUC was 1.4±0.7 GtC yr−1, GATM was 4.6±0.2 GtC yr−1, SOCEAN was 2.5±0.5 GtC yr−1, and SLAND was 3.8±0.8 GtC yr−1, with a BIM of 0.3 GtC. The global atmospheric CO2 concentration reached 405.0±0.1 ppm averaged over 2017. For 2018, preliminary data for the first 6–9 months indicate a renewed growth in EFF of +2.7 % (range of 1.8 % to 3.7 %) based on national emission projections for China, the US, the EU, and India and projections of gross domestic product corrected for recent changes in the carbon intensity of the economy for the rest of the world. The analysis presented here shows that the mean and trend in the five components of the global carbon budget are consistently estimated over the period of 1959–2017, but discrepancies of up to 1 GtC yr−1 persist for the representation of semi-decadal variability in CO2 fluxes. A detailed comparison among individual estimates and the introduction of a broad range of observations show (1) no consensus in the mean and trend in land-use change emissions, (2) a persistent low agreement among the different methods on the magnitude of the land CO2 flux in the northern extra-tropics, and (3) an apparent underestimation of the CO2 variability by ocean models, originating outside the tropics. This living data update documents changes in the methods and data sets used in this new global carbon budget and the progress in understanding the global carbon cycle compared with previous publications of this data set (Le Quéré et al., 2018, 2016, 2015a, b, 2014, 2013). All results presented here can be downloaded from https://doi.org/10.18160/GCP-2018.
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sidd

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #514 on: January 22, 2019, 10:28:30 PM »
Re: Wolf, cloud albedo

My point is that fig 6 b (which i posted in my original comment on Wolf et al.)  showing a minimum in cloud albedo around temperatures of 320-330 K is based on a coarse atmospheric model that must parametrize cloud processes at finer scale. I am no convinced the parametrizations are reliable.

sidd

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #515 on: January 22, 2019, 11:37:04 PM »
Re: Wolf, cloud albedo

My point is that fig 6 b (which i posted in my original comment on Wolf et al.)  showing a minimum in cloud albedo around temperatures of 320-330 K is based on a coarse atmospheric model that must parametrize cloud processes at finer scale. I am no convinced the parametrizations are reliable.

sidd


While your observation seems reasonable, is your point that because Wolf et al (2018) is not perfect:

a. … we can safely ignore their warning?
b. … we should apply the Precautionary Principle and take their warning seriously?
c. … we should redouble our efforts to make better models while also taking precautionary measures?
d. … we should redouble our efforts to make better models while ignoring their warning?

See also:

Title: "Perfect is the enemy of good"

https://en.wikipedia.org/wiki/Perfect_is_the_enemy_of_good

Extract: "Aristotle, Confucius, and other classical philosophers propounded the principle of the golden mean which counsels against extremism in general. The Pareto principle or 80–20 rule explains this numerically. For example, it commonly takes 20% of the full time to complete 80% of a task while to complete the last 20% of a task takes 80% of the effort. Achieving absolute perfection may be impossible and so, as increasing effort results in diminishing returns, further activity becomes increasingly inefficient.

Robert Watson-Watt, who developed early warning radar in Britain to counter the rapid growth of the Luftwaffe, propounded a "cult of the imperfect", which he stated as "Give them the third best to go on with; the second best comes too late, the best never comes.""

Edit:

Also, do you think that Team Schmidt is more correct because there are no sharp tipping points in climate science; or do think Team AOC is more correct because the ocean likely already has enough heat content to assure a MISI collapse of the WAIS in the coming centuries and that following a BAU pathway will likely result in sufficient Earth energy imbalance by 2030 to assure a MICI collapse of the WAIS this century?

Title: "Climate scientists refute 12-year deadline to curb global warming"

https://www.axios.com/climate-change-scientists-comment-ocasio-cortez-12-year-deadline-c4ba1f99-bc76-42ac-8b93-e4eaa926938d.html

Extract: "Reality check: "All the time-limited frames are bullshit," Gavin Schmidt, who leads NASA's Goddard Institute for Space Studies in New York, told Axios in an email. "Nothing special happens when the 'carbon budget' runs out or we pass whatever temperature target you care about, instead the costs of emissions steadily rise," he said. The IPCC report, for example, found the impacts worsen considerably beyond 1.5°C of warming.

•   "The thing to push back against is the implicit framing that there is some magic global mean temperature or total emissions that separate 'fine' from 'catastrophic'. There just isn't," Schmidt said.

The bottom line: Even if hard deadlines are scientifically flawed, they can be effective when it comes to activism. The 12-year timeframe, in particular, has been widely adopted by proponents of climate action.

•   "We can quibble about the phraseology, whether it's existential or cataclysmic" impacts that we'll face without taking action in the next 12 years, Ocasio-Cortez spokesman Corbin Trent told Axios. But, he says, the reality is: "We're seeing lots of [climate change-related] problems that are already impacting lives.""
« Last Edit: January 23, 2019, 12:00:46 AM by AbruptSLR »
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b_lumenkraft

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #516 on: January 23, 2019, 04:42:46 AM »
The linked reference and associated image, indicate that observed Ocean Heat Content, OHC, has increased more rapidly than indicated by AR5.  Hopefully, AR6 will recognize that this trend is not good for mankind's future:

Lijing Cheng, John Abraham, Zeke Hausfather & Kevin E. Trenberth (11 Jan 2019), "How fast are the oceans warming?", Science, Vol. 363, Issue 6423, pp. 128-129, DOI: 10.1126/science.aav7619

They had Zeke Hausfather on The Real News!

Link >>

sidd

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #517 on: January 23, 2019, 05:40:49 AM »
Re: Wolf

c) of course

That does not mean i accept Wolf uncritically on cloud albedo minima. Or that i do not look to other sources for variation in sensitivity with CO2 content.

And as far as Schmidt goes i agree with him also when he says that "All time limited frames are bullshit" The world does not end in 12 years or in 2100 or wherever to care to name. And when he says "The thing to push back against is the implicit framing that there is some magic global mean temperature or total emissions that separate 'fine' from 'catastrophic'. There just isn't,"  i agree there also.We see catastrophes today. We will see many, many more in future. How many is within our control.

Lets say we dont meet 12 yr target. The world will not end. Our costs will, of course, skyrocket in terms of blood and treasure and toil and death.

We know too little, but we know enuf to tell us that what we need to do is minimize fossil burn now. Like, immediately.

As for ice sheet collapse, for me that's a given. Now I'm just trying to nail down a timescale, how much time is left to retreat from the coasts. My gut says we should be doing so now. Maritime civil engineering works on more massive scale than ever before will be required merely to maintain ports. Not to speak of huge civil engineering works rehousing the hapless coastal refugees. Or rising storm drainage. Or ...

sidd
« Last Edit: January 23, 2019, 08:03:07 AM by sidd »

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #518 on: January 23, 2019, 04:44:04 PM »
Re: Wolf

c) of course

That does not mean i accept Wolf uncritically on cloud albedo minima. Or that i do not look to other sources for variation in sensitivity with CO2 content.

And as far as Schmidt goes i agree with him also when he says that "All time limited frames are bullshit" The world does not end in 12 years or in 2100 or wherever to care to name. And when he says "The thing to push back against is the implicit framing that there is some magic global mean temperature or total emissions that separate 'fine' from 'catastrophic'. There just isn't,"  i agree there also.We see catastrophes today. We will see many, many more in future. How many is within our control.

Lets say we dont meet 12 yr target. The world will not end. Our costs will, of course, skyrocket in terms of blood and treasure and toil and death.

We know too little, but we know enuf to tell us that what we need to do is minimize fossil burn now. Like, immediately.

As for ice sheet collapse, for me that's a given. Now I'm just trying to nail down a timescale, how much time is left to retreat from the coasts. My gut says we should be doing so now. Maritime civil engineering works on more massive scale than ever before will be required merely to maintain ports. Not to speak of huge civil engineering works rehousing the hapless coastal refugees. Or rising storm drainage. Or ...

sidd

sidd,

Thank you for your usual thoughtful reply, and I also agree with your prior comment that each individual's 'mileage may vary'; nevertheless, I make the following points about Team Schmidt's position:
1. Team Schmidt appears to recognized MISI (as apparently you do also) but not MICI (& you appear to be uncertain about the initiation date and the rate of ice sheet collapse).  In my opinion, David Pollard (with help from DeConto & Alley) has shown that MICI correlates best with the paleo-record than any other correlation used by Team Schmidt in their models.  So it appears to me that consensus science refuses to put their best foot forward and instead put forward confidence levels based only on MISI (which would be much different if they accepted MICI); which means that decision makers will likely make poor decisions about adaptive measures (like your major civil engineering measures) which will likely mean that the world will be worse off due to these poorly advised decisions.  Furthermore, MICI could be both abrupt (on the scale of decades beginning circa 2040+/- 10-years) and irreversible; so to me this gives the 12-year time frame better context than Team Schmidt's characterization of 'bullshit'.

2. If Hansen et al. are correct that the positive ice-climate feedback is composed of numerous sub-feedback mechanisms (including: bipolar seesaw, polar amplification, ENSO-interactions, telecommunications, etc.) each which may contribute individual tipping points to a combined global response.  Indeed, E3SM uses dynamical climate sensitivity to provide the world's most skillful climate projections (in my opinion much more skillful than those by Team Schmidt) to estimate a mean value of 5.3C for ECS (through 2100), which only considered MISI (and not MICI) in its ice-climate feedback.

Thus, I think that consensus climate scientists (like Team Schmidt and the IPCC) would do well to write annual reports addressing all of the strong climate science reported since AR5, that clarifies the 'long-tail' risks facing society; so that both the public and decision makers can better appreciate the consequences of accepting the incomplete confidence levels associated with consensus science climate projections.

ASLR
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #519 on: January 23, 2019, 07:22:50 PM »
With a hat-tip to jai (for the linked reference and image), Persad & Caldeira (2018) show that if (in the coming decades) anthropogenic aerosol emissions shift from such regions as: Western Europe), the USA and China to such areas as: India and its neighbors; then the negative feedback associated for those coming emissions will be less than assumed by 'many scientific and policy discussions'; which will would mean that the associated global warming would likely be higher than assumed by consensus climate science:

Persad & Caldeira (2018), "Divergent global-scale temperature effects from identical aerosols emitted in different regions", Nature Communications, https://doi.org/10.1038/s41467-018-05838-6

https://www.nature.com/articles/s41467-018-05838-6

With another hat-tip to jai Mitchell, the linked reference (& associate linked article) indicate that consensus climate science is underestimating the cooling effect of anthropogenic aerosols, which means that the climate sensitivity values assumed by consensus climate scientists are too low:

Daniel Rosenfeld, Yannian Zhu, Minghuai Wang, Youtong Zheng, Tom Goren, Shaocai Yu. Aerosol-driven droplet concentrations dominate coverage and water of oceanic low level clouds. Science, 2019; eaav0566 DOI: 10.1126/science.aav0566

http://science.sciencemag.org/content/early/2019/01/16/science.aav0566

Abstract: "Lack of reliable estimates of cloud condensation nuclei (CCN) aerosols over oceans has severely limited our ability to quantify their effects on cloud properties and extent of cooling by reflecting solar radiation – a key uncertainty in anthropogenic climate forcing. Here we introduce a methodology for ascribing cloud properties to CCN and isolating the aerosol effects from meteorological effects. Its application showed that, for a given meteorology, CCN explains 3/4 of the variability in clouds radiative cooling effect, mainly through affecting shallow cloud cover and water path. This reveals a much greater sensitivity of cloud radiative forcing to CCN than previously reported, which means too much cooling if incorporated in present climate models. This hints to yet unknown compensating aerosol warming effects, possibly through deep clouds."

See also:

Title: "We need to rethink everything we know about global warming"

https://www.sciencedaily.com/releases/2019/01/190122104611.htm

Extract: "New research shows that the degree to which aerosols cool the earth has been grossly underestimated, necessitating a recalculation of climate change models to more accurately predict the pace of global warming."

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #520 on: January 23, 2019, 09:52:34 PM »
"...the degree to which aerosols cool the earth has been grossly underestimated..."

That sounds...rather bad!
"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."

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #521 on: January 23, 2019, 09:57:54 PM »
"...the degree to which aerosols cool the earth has been grossly underestimated..."

That sounds...rather bad!

Anthropogenic aerosol radiative forcing consists of both first indirect effect, FIE, and second indirect effect, SIE.  The linked reference indicates that FIE results in significantly more cooling than previously assumed by consensus climate science:

McCoy, D. T., F. A.-M. Bender, J. K. C. Mohrmann, D. L. Hartmann, R. Wood, and D. P. Grosvenor (2017), The global aerosol-cloud first indirect effect estimated using MODIS, MERRA, and AeroCom, J. Geophys. Res. Atmos., 122, doi:10.1002/2016JD026141.

https://agupubs.onlinelibrary.wiley.com/doi/10.1002/2016JD026141

Abstract: "Aerosol-cloud interactions (ACI) represent a significant source of forcing uncertainty in global climate models (GCMs). Estimates of radiative forcing due to ACI in Fifth Assessment Report range from -0.5 to-2.5Wm-2. A portion of this uncertainty is related to the first indirect, or Twomey, effect whereby aerosols act as nuclei for cloud droplets to condense upon. At constant liquid water content this increases the number of cloud droplets (Nd) and thus increases the cloud albedo. In this study we use remote-sensing estimates of Nd within stratocumulus regions in combination with state-of-the-art aerosol reanalysis from Modern-Era Retrospective Analysis for Research and Applications version 2 (MERRA2) to diagnose how aerosols affect Nd. As in previous studies, Nd is related to sulfate mass through a power law relationship. The slope of the log-log relationship between Nd and SO4 in maritime stratocumulus is found to be 0.31, which is similar to the range of 0.2–0.8 from previous in situ studies and remote-sensing studies in the pristine Southern Ocean. Using preindustrial emissions models, the change in Nd between preindustrial and present day is estimated. Nd is inferred to have more than tripled in some regions. Cloud properties from Moderate Resolution Imaging Spectroradiometer (MODIS) are used to estimate the radiative forcing due to this change in Nd. The Twomey effect operating in isolation is estimated to create a radiative forcing of -0.97±0.23Wm-2 relative to the preindustrial era."
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sidd

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #522 on: January 23, 2019, 10:18:53 PM »
A citation for "Team Schmidt" stating anything about ice sheet collapse sans MICI would be nice ...? I find nothing in Dr. Schmidt's statements about this. IN fact, Bassis, Deconto and Pollard published after the deadline for the last IPCC report, so blaming IPCC for not including those results violates causality. If the next IPCC report ignores them, you might have a point. As for your suggestion that IPCC produce yearly reports, have you any idea what it takes to produce one of the AR reports ? Much longer than a year. If all scientists did was lit revieww and reports they would do nothing else.

Further, who is on "Team Schmidt" in the first place ?

I find characterizing people as members of "Teams" is unproductive.

As for my feeling about MICI : ofcourse it is happening, look at Jacobshawn. And I cannot say for sure, but Mercer's famous warning about the midsummer 0C isotherm applies not just to ice shelves, but to grounded ice also. But for now in Antarctica CDW incursion and bottom melt is far more important.

sidd


 

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #523 on: January 23, 2019, 11:19:01 PM »
A citation for "Team Schmidt" stating anything about ice sheet collapse sans MICI would be nice ...? I find nothing in Dr. Schmidt's statements about this. IN fact, Bassis, Deconto and Pollard published after the deadline for the last IPCC report, so blaming IPCC for not including those results violates causality. If the next IPCC report ignores them, you might have a point. As for your suggestion that IPCC produce yearly reports, have you any idea what it takes to produce one of the AR reports ? Much longer than a year. If all scientists did was lit revieww and reports they would do nothing else.

Further, who is on "Team Schmidt" in the first place ?

I find characterizing people as members of "Teams" is unproductive.

As for my feeling about MICI : ofcourse it is happening, look at Jacobshawn. And I cannot say for sure, but Mercer's famous warning about the midsummer 0C isotherm applies not just to ice shelves, but to grounded ice also. But for now in Antarctica CDW incursion and bottom melt is far more important.

sidd

sidd,

First, I used the term 'Team Schmidt' to connect to Schmidt's quotes in the article, but generally I meant contributors to CMIP5.  But as you seem to imply that it violates causality to discuss the limitations (shortcomings) of CMIP5 or AR5, I provide the following link to open access information on ISMIP6 which provides input into CMIP6 (which will figure prominently in AR6), and I note that the first attached image showing ice sheet models used in AR6, does not include any models that account for MICI:

Nowicki et al (2016), "Ice Sheet Model Intercomparison Project (ISMIP6) contribution to CMIP6", Geosci. Model Dev., 9, 4521-4545, https://doi.org/10.5194/gmd-9-4521-2016

https://www.geosci-model-dev.net/9/4521/2016/
&
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5911933/

Abstract: "Reducing the uncertainty in the past, present and future contribution of ice sheets to sea-level change requires a coordinated effort between the climate and glaciology communities. The Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6) is the primary activity within the Coupled Model Intercomparison Project – phase 6 (CMIP6) focusing on the Greenland and Antarctic Ice Sheets. In this paper, we describe the framework for ISMIP6 and its relationship to other activities within CMIP6. The ISMIP6 experimental design relies on CMIP6 climate models and includes, for the first time within CMIP, coupled ice sheet – climate models as well as standalone ice sheet models. To facilitate analysis of the multi-model ensemble and to generate a set of standard climate inputs for standalone ice sheet models, ISMIP6 defines a protocol for all variables related to ice sheets. ISMIP6 will provide a basis for investigating the feedbacks, impacts, and sea-level changes associated with dynamic ice sheets and for quantifying the uncertainty in ice-sheet-sourced global sea-level change."
 
Second, my suggestion was that consensus climate scientist not issue annual Assessment Reports, but rather only to annually discuss the more current estimates of the 'long-tail' risks (e.g. the impact of the greater cooling effects of aerosols on the most likely values of ECS) facing society (such as illustrated by the second and third images for AR5, but updated annually).

ASLR
« Last Edit: January 23, 2019, 11:28:02 PM by AbruptSLR »
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AbruptSLR

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As in my last post I pointed to aerosols as one example of long-tailed risk within the guidance provided by such consensus science documents.  To get a better grip on what this might mean, given that research such as McCoy et al (2017) and Rosenfeld et al (2018), indicate that Fareo (Current aerosol radiative forcing) is likely much more negative than -1.0 Wm-2, I provide Figures 1 & 3 from Mauritsen & Pincus (2017).  Where Figure 1 shows observed values of TCR and ECS used in AR5 (also I provide the third image that shows how observed values of ECS relates to true values of ECS); and Figure 3 shows that for Fareo more negative than -1.0 Wm-2, that observed TCR is higher than assumed by AR5 (see note below), indicating that the Centennial committed warming will be higher than previously estimated:

Thorsten Mauritsen, Robert Pincus. Committed warming inferred from observations. Nature Climate Change, 2017; DOI: 10.1038/NCLIMATE3357

https://www.nature.com/articles/nclimate3357

Also, I note that for:
i) Equilibrium Climate Sensitivity (ECS)
The AR5 assesses ECS as likely to be 1.5°C to 4.5°C. ECS is extremely unlikely to be less than 1°C and very unlikely to be greater than 6°C.

This compares with the Fourth Assessment Report, which assessed ECS as likely to be 2 to 4.5°C.

ii) Transient Climate Response (TCR)
The AR5 assesses TCR as likely to be 1°C to 2.5°C and extremely unlikely to be greater than 3°C. In the Fourth Assessment Report, the assessed range of TCR was very unlikely to be less than 1.0°C and very unlikely to be greater than 3.0°C. The assessed ranges are therefore quoted differently, making direct comparison difficult, but compared with the previous report there has been a decrease in the assessed likelihood that the TCR is over 3.0°C from <10% to <5%.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson