RE post #2751 about albedo in the 2019 Melt Season thread
Radiative Heating of an Ice‐free Arctic Ocean
Kristina Pistone Ian Eisenman V. Ramanathan
First published: 20 June 2019
https://doi.org/10.1029/2019GL082914"During recent decades, there has been dramatic Arctic sea ice retreat. This has reduced the top‐of‐atmosphere albedo, adding more solar energy to the climate system. There is substantial uncertainty regarding how much ice retreat and associated solar heating will occur in the future. This is relevant to future climate projections, including the timescale for reaching global warming stabilization targets. Here we use satellite observations to estimate the amount of solar energy that would be added in the worst‐case scenario of a complete disappearance of Arctic sea ice throughout the sunlit part of the year. Assuming constant cloudiness, we calculate a global radiative heating of 0.71 W/m2 relative to the 1979 baseline state. This is equivalent to the effect of one trillion tons of CO2 emissions. These results suggest that the additional heating due to complete Arctic sea ice loss would hasten global warming by an estimated 25 years."
Trillion tons CO2, i.e. about 25 years of current annual global emissions. That's just a theoretical benchmark number of course, we are a long way from Arctic being ice free all summer. But every portion thereof adds another slice of warming energy.
Same authors did an earlier, more practical study:
Observational determination of albedo decrease caused by vanishing Arctic sea ice
Kristina Pistone, Ian Eisenman1, and V. Ramanathan
322–3326 | PNAS | March 4, 2014 | vol. 111 | no. 9
www.pnas.org/cgi/doi/10.1073/pnas.1318201111"The decline of Arctic sea ice has been documented in over 30 y of
satellite passive microwave observations. The resulting darkening
of the Arctic and its amplification of global warming was hypothesized
almost 50 y ago but has yet to be verified with direct
observations. This study uses satellite radiation budget measurements
along with satellite microwave sea ice data to document
the Arctic-wide decrease in planetary albedo and its amplifying
effect on the warming. The analysis reveals a striking relationship
between planetary albedo and sea ice cover, quantities inferred
from two independent satellite instruments. We find that the Arctic
planetary albedo has decreased from 0.52 to 0.48 between 1979
and 2011, corresponding to an additional 6.4 ± 0.9 W/m2 of solar
energy input into the Arctic Ocean region since 1979. Averaged
over the globe, this albedo decrease corresponds to a forcing that
is 25% as large as that due to the change in CO2 during this period,
considerably larger than expectations from models and other less
direct recent estimates. Changes in cloudiness appear to play
a negligible role in observed Arctic darkening, thus reducing
the possibility of Arctic cloud albedo feedbacks mitigating future
Arctic warming."
Note that study period ended in 2011. After 2019 easy to think that 25% could be up to 30%.