PNNL BEST-CASE Modeling: Arctic Gains .45F Per Decade Starting In 2020 W. Stabilization @ 525 ppm
New research from a major national lab projects that the rate of climate change, which has risen sharply in recent decades, will soar by the 2020s. This worrisome projection — which has implications for extreme weather, sea level rise, and permafrost melt — is consistent with several recent studies.
The Pacific Northwest National Laboratory (PNNL) study, “Near-term acceleration in the rate of temperature change,” finds that by 2020, human-caused warming will move the Earth’s climate system “into a regime in terms of multi-decadal rates of change that are unprecedented for at least the past 1,000 years.”
In the best-case scenario PNNL modeled, with atmospheric carbon dioxide concentrations stabilizing at about 525 parts per million (the RCP4.5 scenario), the four-decade warming trend hits 0.45°F (0.25°C) per decade. That means over a 4-decade period, the Earth would warm 1.8°F (4 x 0.45) or 1°C (4 x 0.25). This is a faster multi-decadal rate than the Earth has seen in at least a millennium. Because of Arctic amplification, the most northern latitudes warm two times faster (or more) than the globe as a whole does. As this figure from the study shows, the rate of warming for the Arctic is projected to quickly exceed 1.0°F (0.55°C) per decade.
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This chart shows that the observed decadal warming rate (temperature rise per decade) has been constant for the past decade in the Met/Hadley record. While this is within the range of model uncertainty, the study suggests it should have kept increasing. Many recent studies project that will happen very soon — and indeed it may already have started. In the do-little RCP8.5 scenario, the rate of warming post-2050 becomes so fast that it is likely to be beyond adaptation for most species — and for humans in many parts of the world. The warming rate in the central case hits a stunning 1°F per decade — Arctic warming would presumably be at least 2°F per decade. And this goes on for decades.
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http://thinkprogress.org/climate/2015/03/10/3631632/climate-change-rate/