A new, deeply flawed study on the climate’s sensitivity to greenhouse gas emissions reveals just how poorly the media understand key climate science issues. It also reveals how eager some in the media are to push the mistaken message that failure to act quickly and aggressively on GHG emissions would not be catastrophic.
Here’s what you need to know about the study by Schmittner et al in Science (subs. req’d):
- Its key finding is that the so-called “fast-feedbacks sensitivity” of the climate (to a doubling of CO2 levels) is on the low side. This finding is likely wrong, according to many leading climatologists (see below).
- Even if the study’s findings hold up, we are headed toward high warming on our current GHG emissions path. That’s because we are headed toward a tripling or higher of CO2 levels and because the slower feedbacks ain’t so slow (see “NSIDC bombshell: Thawing permafrost feedback will turn Arctic from carbon sink to source in the 2020s, releasing 100 billion tons of carbon by 2100“).
- The study finds that small changes in Earth’s temperature can have huge impacts on the land — that’s why it finds a low sensitivity!
This last, crucial point seems to have escaped the attention of many U.S. reporters on the study — even though it is quite clearly stated in the study’s news release:
“It shows that even very small changes in the ocean’s surface temperature can have an enormous impact elsewhere, particularly over land areas at mid- to high-latitudes,” [Schmittner] added.
Note to media: Most Americans live on “land areas at mid- to high-latitudes.”
“Hence, drastic changes over land can be expected,” he said. “However, our study implies that we still have time to prevent that from happening, if we make a concerted effort to change course soon.”
In short, act quickly and aggressively or suffer drastic impacts.
Now contrast that to Eric Berger, science reporter for the Houston Chronicle, who writes in his mis-summary of the paper:
To me, the real effect of this paper will be to really impair the credibility of the more extreme environmentalists who have been saying the planet faces certain doom from climate change.
I am thinking about such efforts as Bill McKibben’s 350 campaign…. Such environmentalists assert that the planet will warm as much as 6 Celsius degrees with a doubling of atmospheric carbon dioxide levels.
That’s a big number and doubtless would have catastrophic consequences for the planet. This is not in dispute. But scientists are now telling us this is not going to happen.
Actually, it is Berger’s credibility that has taken a hit, and he owes McKibben an apology. For the record, McKibben doesn’t say we are facing “certain doom” from climate change. He — and NASA’s James Hansen, the scientist whose work inspired McKibben — typically say we are headed for multiple catastrophes if we stay anywhere near our current emissions path.
This new study does not contradict that view. Indeed, it supports it. As Skeptical Science (SkS) concluded its summary:
In fact if Schmittner et al. are totally correct, we may be in for some rapid climate changes in the relatively near future.
Moreover, many major, independent studies suggest that, yes, we are risking 6°C (11°F) warming on our current emissions path (see Hadley Center: “Catastrophic” 5-7°C warming by 2100 on current emissions path and M.I.T. doubles its 2095 warming projection to 10°F — with 866 ppm and Arctic warming of 20°F.
And don’t forget those darn extreme environmentalists at the International Energy Agency this month — see IEA’s Bombshell Warning: We’re Headed Toward 11°F Global Warming and “Delaying Action Is a False Economy”.
Berger actually cites Hansen’s main finding but then trashes it because he doesn’t appear to understand what Hansen (and many others) have found. As Skeptical Science explained (see this post):
A 2008 study led by James Hansen found that climate sensitivity to “fast feedback processes” is 3°C, but when accounting for longer-term feedbacks (such as ice sheet disintegration, vegetation migration, and greenhouse gas release from soils, tundra or ocean), if atmospheric CO2 remains at the doubled level, the sensitivity increases to 6°C based on paleoclimatic (historical climate) data.
The fact is we’re already seeing the acceleration of the “slower” amplifying feedbacks (see Stunning Peatlands Amplifying Feedback: Drying Wetlands and Intensifying Wildfires Boost Carbon Release Ninefold).
To be crystal clear, since it isn’t just Berger but also the New York Times and others who seem confused about this, the amount of warming we are going to subject our children and countless future generations to depends primarily on three factors:
- The sensitivity of the climate to fast feedbacks like sea ice and water vapor (how much warming you get if we only double CO2 emissions to 560 ppm and there are no major “slow” feedbacks). We know the fast feedbacks are strong by themselves (see Study: Water-vapor feedback is “strong and positive,” so we face “warming of several degrees Celsius”). Indeed, the results of a major recent Journal of Climate study on cloud feedback “provide support for the high end of current estimates of global climate sensitivity.”
- The real-world slower (decadal) feedbacks, such as tundra melt and peatlands and drought-driven emissions (see Science: Second ’100-year’ Amazon drought in 5 years caused huge CO2 emissions. If this pattern continues, the forest would become a warming source).
- The actual CO2 concentration level we are likely to hit, which is far beyond 550 ppm (see Biggest Jump Ever in Global Warming Pollution in 2010).
Indeed, it was the IPCC itself that warned we are headed toward 1000 ppm, particularly if the decadal carbon-cycle feedbacks do kick in — see “Hidden Bombshell in the IPCC Fourth Assessment” and my discussion in Nature online.
Schmittner et al only deals with #1. Sadly, #2 and #3 are more than enough to ensure humanity’s destruction even if Schmittner et al is right, indeed, especially if it is right. But it probably isn’t.
– Matt Bush in a 
