deniers commenters say I focus too much on the inordinate number of positive or amplifying feedbacks, whereby an initial warming causes changes that lead to more warming:
- Humans boosting CO2 14,000 times faster than nature, overwhelming slow negative feedbacks
- Wetlands destruction — another climate feedback
- Tundra 3: Forests and fires foster feedbacks
- Decelerating growth in tropical forest trees — thanks to accelerating carbon dioxide
- The desertification-global warming feedback.
- Are Scientists Overestimating — or Underestimating — Climate Change, Part II
But just to show how balanced this blog is, I’m happy to report that researchers have found a (temporary) negative feedback that could slow some of the impacts of global warming:
Smoke transported to the Arctic from northern forest fires may cool the surface for several weeks to months at a time, according to the most detailed analysis yet of how smoke influences the Arctic climate relative to the amount of snow and ice cover.
Here is the full study, “Radiative impact of boreal smoke in the Arctic” (subs. req’d). This qualifies as a negative feedback because global warming has been predicted to lead to more wildfires (see “Global warming and the California wildfires” and “California wildfires update“). Here is “NOAA satellite image, June 30, 2004, showing wildfire smoke blanketing Alaska”:
“Smoke in the atmosphere temporarily reduces the amount of solar radiation reaching the surface. This transitory effect could partly offset some of the warming caused by the buildup of greenhouse gases and other pollutants,” said Robert Stone, an atmospheric scientist with the university and NOAA Cooperative Institute for Research in Environmental Sciences (CIRES) and lead author of the study, which recently appeared in the Journal of Geophysical Research.
How much solar energy is prevented from reaching the surface depends on the smoke’s opacity, the elevation of the sun above the horizon, and the brightness of the surface, according to the study.
So all you delayers out there who have been saying for years that the negative feedbacks overwhelm the amplifying feedbacks … well, you’ll still find no support for that Pollyannish view in the scientific literature. Even if the entire West burns to a cinder thanks to climate-driven wildfires, the Arctic is going ice free several decades ahead of what the models had predicted. And then it appears the really scary feedbacks will kick in (see “Tundra 4: Permafrost loss linked to Arctic sea ice loss“).
The time to act is still yesterday.