Today's question: How the heck does the Greenland ice sheet survive accelerated disintegration from projected 20°F warming by the 2090s?
I previously blogged on how the Massachusetts Institute of Technology Joint Program on the Science and Policy of Climate Change has joined the climate realists — the growing group of scientists who understand that the business as usual emissions path leads to unmitigated catastrophe (see "Hadley Center: "Catastrophic" 5-7°C warming by 2100 on current emissions path" and below).
Back in January, the Program issued a remarkable report in January, by over a dozen leading experts, doubling their 2095 warming projection to 5.2°C. The media mostly ignored it, which is no surprise, since the media generally ignores the realists in general (see U.S. media largely ignores latest warning from climate scientists: "Recent observations confirm … the worst-case IPCC scenario trajectories (or even worse) are being realised" — 1000 ppm).
Now, the MIT study has been published in a peer-reviewed journal — The American Meteorological Society's Journal of Climate (subs. req'd) — which obviously it makes it much more credible and high-profile. Reuters has a good story on it, "Global warming could be twice as bad as forecast." The study concludes:
The MIT Integrated Global System Model is used to make probabilistic projections of climate change from 1861 to 2100. Since the model's first projections were published in 2003 substantial improvements have been made to the model and improved estimates of the probability distributions of uncertain input parameters have become available. The new projections are considerably warmer than the 2003 projections, e.g., the median surface warming in 2091 to 2100 is 5.2°C compared to 2.4°C in the earlier study. Many changes contribute to the stronger warming; among the more important ones are taking into account the cooling in the second half of the 20th century due to volcanic eruptions for input parameter estimation and a more sophisticated method for projecting GDP growth which eliminated many low emission scenarios.
[Note: That rise is compared to 1981-2000 temperature levels. So you can add at least 0.5 °C and 1.0 °F for comparison with pre-industrial temperatures, which I did in the headline -- see "A (Hopefully) Clarifying Note on Temperature."]
The MIT press release calls for "rapid and massive" action to avoid this.