The best evidence is that the climate is now being driven by amplifying feedbacks (see Study: Water-vapor feedback is “strong and positive,” so we face “warming of several degrees Celsius”), most notably:
- The defrosting of the permafrost
- The drying of the Northern peatlands (bogs, moors, and mires).
- The destruction of the tropical wetlands
- Decelerating growth in tropical forest trees “” thanks to accelerating carbon dioxide
- Wildfires and Climate-Driven forest destruction by pests
- The desertification-global warming feedback
- The saturation of the ocean carbon sink
In spite of all evidence to the contrary, the deniers/delayers/inactivists, led by MIT’s Richard Lindzen, have argued that negative feedbacks dominate the climate system. In particular, they have asserted that clouds are a negative feedback. A major new study in Science from “Observational and Model Evidence for Positive Low-Level Cloud Feedback” (subs. req’d) is thus a potentially huge — and worrisome — piece of research.
I’m in an all-day meeting, so I’m mainly going to reprint the study abstract, the accompanying Science news story, “Clouds Appear to Be Big, Bad Player in Global Warming” (subs. req’d), and the press release from the University of Miami’s Rosenstiel School of Marine and Atmospheric Sciences, who led the study (with the Scripps Institution of Oceanography, my old stomping ground snorkeling reef).
It is worth noting that the one climate model the researchers found was “particularly realistic” in modeling the cloud feedback, the Hadley Center’s HadGEM1, finds, “When carbon dioxide is doubled, the model warms the world by 4.4°C; the median of the models for a doubling is 3.1°C.” Considering that we are headed toward more than a tripling of CO2 concentrations this century, that is very, very worrisome.
FIGURE: “Leaky clouds. Decades-long records show that when sea surface temperature (SST) warms, cloud cover””especially from low clouds (bottom)””decreases (blues, top), letting in more sunlight.”
Let’s start with the PR: