A major new study published Friday in Geophysical Research Letters by leading tundra experts has found “Accelerated Arctic land warming and permafrost degradation during rapid sea ice loss.” The lead author is David Lawrence of the National Center for Atmospheric Research (NCAR), who I interviewed for my book and recently interviewed again via e-mail about his recent work. The study’s ominous conclusion:
We find that simulated western Arctic land warming trends during rapid sea ice loss are 3.5 times greater than secular 21st century climate-change trends. The accelerated warming signal penetrates up to 1500 km inland….
In other words, if it continues, the recent trend in sea ice loss may triple Arctic warming, causing large emissions in carbon dioxide and methane from the tundra this century. What is especially worrisome is that 2007 provides strong evidence on behalf of this theory:
- NOAA reported that methane levels rose in 2007 for the first time since 1998 (see here).
- The tundra can emit vast amounts of methane when it defrosts (see Part 1).
- Scientific analysis suggests the rise in 2007 methane levels came from Arctic wetlands (see here).
- And 2007 saw record Arctic ice loss [see "Ice Ice Maybe (not)"].
So I would certainly pay attention to what these scientists have to say. How much warmer did the Arctic get last summer, and how much warmer might it get with further ice loss?
From August to October last year, air temperatures over land in the western Arctic were also unusually warm, reaching more than 2 degrees Celsius (4 degrees Fahrenheit) above the 1978–2006 average….
The decade during which a rapid sea-ice loss event occurs could see autumn temperatures warm by as much as 5 degrees C (9 degrees F) along the Arctic coasts of Russia, Alaska, and Canada.
Needless to say, such warming would have a huge impact on the permafrost:
“An important unresolved question is how the delicate balance of life in the Arctic will respond to such a rapid warming,” Lawrence says. “Will we see, for example, accelerated coastal erosion, or increased methane emissions, or faster shrub encroachment into tundra regions if sea ice continues to retreat rapidly?”
Faster shrub encroachment would, of course, also accelerate warming (see “Tundra 3: Forests and fires foster feedbacks“).
And all that warming would cause massive melting of the tundra and faster emissions release. That must be avoided at all cost, since the tundra feedback, coupled with the climate-carbon-cycle feedbacks that the IPCC models, could easily take us to the unmitigated catastrophe of 1000 ppm (see Tundra, Part 2: The point of no return).
In the interest of completeness, there has been the typical academic back-and-forth on the details of Lawrence’s 2005 study (subs.req’d) on tundra loss this century. It now looks like that initial study slightly overestimated the rate at which permafrost would be lost. Lawrence revised and updated his analysis in this recent study, “Sensitivity of a model projection of near-surface permafrost degradation to soil column depth and representation of soil organic matter” (subs. req’d), which still finds: “Even at the depressed rate, however, the warming is enough to drive near-surface permafrost extent sharply down by 2100.”
I asked Lawrence if it was still reasonable to keep using this figure in my presentation, since it is so much easier to understand than the figures in his new paper.
He said, “Using the old figure is still fine as long as one mentions the caveats that permafrost is probably degrading a bit too rapidly in the original.” So I will certainly use that caveat, though, of course, I will also caveat the caveat by saying the slightly slower rate of permafrost degradation does not include Lawrence’s new analysis on the accelerated warming of the permafrost due to sea ice loss (or, for that matter, the accelerated warming of the permafrost due to faster shrub encroachment).
Needless to say, the time to act is yesterday!