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Saturday, February 15, 2014

Arctic Autumns On Track To Warm A Staggering 23 °F, NOAA Warns

Credit: NOAA
by Joe Romm, Climate Progress, February 13, 2014
“Climate models show carbon emission mitigation could slow Arctic temperature increases.” That is NOAA’s glass-is-half-full-of-ice headline for a new study that finds we are on track for mind-boggling Arctic warming this century.
Since that “dog bites man” headline is essentially self-evident, the story didn’t get much pick up. NOAA buried the bombshell lede:
Climate model projections show an Arctic-wide end-of-century temperature increase of +13 °C [23 °F!] in late fall and +5 °C [9 °F] in late spring if the status quo continues and current emissions increase without a mitigation scenario.
If you think the weather has been weird, the Arctic sea ice loss astounding, and the accelerating Greenland ice sheet loss worrisome with the modest Arctic warming we’ve had to date, well, buckle up, we’re in for a bumpy century.
Arctic sea ice volume has already decreased by 75% since the 1980s. The mean Arctic temperature is 1.5 °C higher today than it was for the period from 1971-2000, double the warming that has occurred in the lower latitudes.
Obviously the Arctic will be ice free in the late summer and early fall long before century’s end. The study itself concludes, “it is very likely that the Arctic Ocean will become seasonally nearly sea ice free before 2050 and possibly within a decade or two.” How fast Greenland could melt if large parts of it were some 20 °F warmer in the fall is not known, but one would have to imagine that it would be a considerably faster pace than today — leading ultimately to an ice-free Greenland, which, by itself would raise sea levels more than 20 feet.
As NOAA explains, we have long known that the Arctic would warm much faster than Earth as a whole:
Temperature increases in response to greenhouse gases are amplified in the Arctic due to large-scale changes in the ability of the Arctic to reflect sunlight. As atmospheric temperatures increase, ice and snow decline, which opens up larger areas of water and land to the sun. Open water and snow and ice-free land absorb and store heat at a much higher rate than snow and ice, which reflects sunlight and heat. This physical process is known as Arctic amplification.
For more on our Arctic amplification, click here.
Certainly no rational society would allow the kind of warming projected by this study, enough to destroy the stable climate that has supported an agricultural system capable of feeding several billion people. And remember, current warming is already off the charts: One recent analysis concluded, “the indications are that Canadian Arctic temperatures today have not been matched or exceeded for roughly 120,000 years.”
The authors of the new study report that aggressive action to cut carbon pollution could minimize the catastrophe:
In contrast, the mean temperature projection would be +7 °C in late fall and +3 °C in late spring by the end of the century if a mitigation scenario to reduce emissions is followed, concludes the paper titled, “Future Arctic Climate Changes: Adaptation and Mitigation Timescales.”
These numbers may still seem quite alarming to you. They should. It is worth noting that the mitigation scenario the authors use is RCP4.5, which is roughly an atmospheric concentration if 538 parts per million CO2 (see here).
This study essentially writes off the possibility of humanity doing any better:
The RCP2.6 scenario requires a 70% reduction of emissions relative to present levels by 2050, a scenario that is highly unlikely in view of the current trajectory of emissions and the absence of progress toward mitigation measures. We refer to the RCP8.5 and RCP4.5 future scenarios as business-as-usual and mitigation.

But the fact is that RCP2.6 — which is about 421 ppm CO2 — is entirely feasible from both a technical and economic perspective. It is only the irrationality, myopia, and, it would seem, self-destructiveness of Homo sapiens that make it “highly unlikely.”

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