[math-fun] Sea level rise 10ft in next 50 years, estimate 16 climatologists
James Hansen, M. Sato, P. Hearty, R. Ruedy, M. Kelley, V. Masson-Delmotte, G. Russell, G. Tselioudis, J. Cao, Eric Rignot, I. Velicogna, E. Kandiano, K. von Schuckmann, P. Kharecha, A. N. Legrande, M. Bauer, and K.-W. Lo: Ice melt, sea level rise and superstorms: evidence from paleoclimate data, climate modeling, and modern observations that 2C global warming is highly dangerous, Atmospheric Chemistry and Physics Discuss. 15 (2015) 20059-20179. http://www.atmos-chem-phys-discuss.net/15/20059/2015/acpd-15-20059-2015.html ABSTRACT: There is evidence of ice melt, sea level rise to +5-9meter, and extreme storms in the prior interglacial period that was less than 1C warmer than today. Human-made climate forcing is stronger and more rapid than paleo forcings, but much can be learned by combining insights from paleoclimate, climate modeling, and on-going observations. We argue that ice sheets in contact with the ocean are vulnerable to non-linear disintegration in response to ocean warming, and we posit that ice sheet mass loss can be approximated by a doubling time up to sea level rise of at least several meters. Doubling times of 10, 20 or 40 years yield sea level rise of several meters in 50, 100 or 200 years. Paleoclimate data reveal that subsurface ocean warming causes ice shelf melt and ice sheet discharge. Our climate model exposes amplifying feedbacks in the Southern Ocean that slow Antarctic bottom water formation and increase ocean temperature near ice shelf grounding lines, while cooling the surface ocean and increasing sea ice cover and water column stability. Ocean surface cooling, in the North Atlantic as well as the Southern Ocean, increases tropospheric horizontal temperature gradients, eddy kinetic energy and baroclinicity, which drive more powerful storms. We focus attention on the Southern Ocean's role in affecting atmospheric CO2 amount, which in turn is a tight control knob on global climate. The millennial (500-2000 year) time scale of deep ocean ventilation affects the time scale for natural CO2 change, thus the time scale for paleo global climate, ice sheet and sea level changes. This millennial carbon cycle time scale should not be misinterpreted as the ice sheet time scale for response to a rapid human-made climate forcing. Recent ice sheet melt rates have a doubling time near the lower end of the 10-40 year range. We conclude that 2C global warming above the preindustrial level, which would spur more ice shelf melt, is highly dangerous. Earth's energy imbalance, which must be eliminated to stabilize climate, provides a crucial metric.
http://sealevel.colorado.edu/ 1 cm every three years, so far. -----Original Message----- From: math-fun [mailto:math-fun-bounces@mailman.xmission.com] On Behalf Of Warren D Smith Sent: Thursday, July 23, 2015 10:06 AM To: math-fun@mailman.xmission.com Subject: [EXTERNAL] [math-fun] Sea level rise 10ft in next 50 years, estimate 16 climatologists James Hansen, M. Sato, P. Hearty, R. Ruedy, M. Kelley, V. Masson-Delmotte, G. Russell, G. Tselioudis, J. Cao, Eric Rignot, I. Velicogna, E. Kandiano, K. von Schuckmann, P. Kharecha, A. N. Legrande, M. Bauer, and K.-W. Lo: Ice melt, sea level rise and superstorms: evidence from paleoclimate data, climate modeling, and modern observations that 2C global warming is highly dangerous, Atmospheric Chemistry and Physics Discuss. 15 (2015) 20059-20179. http://www.atmos-chem-phys-discuss.net/15/20059/2015/acpd-15-20059-2015.html ABSTRACT: There is evidence of ice melt, sea level rise to +5-9meter, and extreme storms in the prior interglacial period that was less than 1C warmer than today. Human-made climate forcing is stronger and more rapid than paleo forcings, but much can be learned by combining insights from paleoclimate, climate modeling, and on-going observations. We argue that ice sheets in contact with the ocean are vulnerable to non-linear disintegration in response to ocean warming, and we posit that ice sheet mass loss can be approximated by a doubling time up to sea level rise of at least several meters. Doubling times of 10, 20 or 40 years yield sea level rise of several meters in 50, 100 or 200 years. Paleoclimate data reveal that subsurface ocean warming causes ice shelf melt and ice sheet discharge. Our climate model exposes amplifying feedbacks in the Southern Ocean that slow Antarctic bottom water formation and increase ocean temperature near ice shelf grounding lines, while cooling the surface ocean and increasing sea ice cover and water column stability. Ocean surface cooling, in the North Atlantic as well as the Southern Ocean, increases tropospheric horizontal temperature gradients, eddy kinetic energy and baroclinicity, which drive more powerful storms. We focus attention on the Southern Ocean's role in affecting atmospheric CO2 amount, which in turn is a tight control knob on global climate. The millennial (500-2000 year) time scale of deep ocean ventilation affects the time scale for natural CO2 change, thus the time scale for paleo global climate, ice sheet and sea level changes. This millennial carbon cycle time scale should not be misinterpreted as the ice sheet time scale for response to a rapid human-made climate forcing. Recent ice sheet melt rates have a doubling time near the lower end of the 10-40 year range. We conclude that 2C global warming above the preindustrial level, which would spur more ice shelf melt, is highly dangerous. Earth's energy imbalance, which must be eliminated to stabilize climate, provides a crucial metric. _______________________________________________ math-fun mailing list math-fun@mailman.xmission.com<mailto:math-fun@mailman.xmission.com> https://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun
Actually it seems there were 17 authors not 16. It is not easy to judge this. Their paper is very long and detailed and rests on 3 legs: 1. the "Eemian": last period when climate was warmer than now, 118 kyr ago, when they claim based on paleo/geological evidence collected in a large number of other papers all over the world, that there were large rapid sea level rises and falls, huge waves, and superstorms. 2. running computer climate models with a few new effects added that cause positive feedbacks and hence exponential "doubling time" behaviors of, e.g. ice sheet melt rates. There are some obvious positive feedbacks like more sheet melt ==> darker earth surface ==> more warming, with the rate increasing exponentially, the more ice has melted, the faster it melts. There also are some non-obvious feedbacks such as the impact if fresh meltwater on ocean currents driven by salinity differences. 3. contemporary measurements of stuff like ice sheet melt rates, sea level, and ice sheet cover from satellite photos, radar, and gravity measurements, which is used to justify the alterations in the computer models. For example, the old models (they say) had too much vertical ocean mixing. If that is reduced, then the surface waters get warmer faster than in the old models, causing more storms and more ice to melt. They think during the Eemian there was 2-3 meter sea rise, than a 2-3 meter fall, then a 6-9 meter rise. Wikipedia says the Eemian was 130 to 115 kyr ago. https://en.wikipedia.org/wiki/Eemian They believe these changes each took less than 500 years, maybe only 100. I doubt it is possible to reach their level of confidence without basically becoming a climatologist yourself, and one specializing in their topics, and maybe not even then since it took 17 authors. -- Warren D. Smith http://RangeVoting.org <-- add your endorsement (by clicking "endorse" as 1st step)
participants (2)
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Cordwell, William R -
Warren D Smith