In a commentary published with the study, David Beerling, a paleobiologist at the University of Sheffield in England, writes: “The upshot of the study. is that forecasts of future warming could be severely underestimating the extent of the problem that lies in store for humanity as greenhouse gases accumulate in the atmosphere.”
According to Melanie Fitzpatrick, a climate scientist at the Union of Concerned Scientists (UCS), carbon dioxide-induced warming can lead to changes that exacerbate the problem. For example, increasing CO2 concentrations:
– melt tundra, which then releases methane and other heat-trapping gases into the atmosphere;
– warm the air, which then can hold more water vapor, another heat-trapping gas; and
– melt white ice, which exposes the ocean and land, which, because they are darker in color, absorb more heat from the sun and reflect less of it back into space.
Scientists are still trying to precisely quantify the effect of such “positive feedback cycles” that took place millions of years ago as well as the ones that are happening today, Fitzpatrick said. The scientific literature, including the new Nature Geoscience study, indicates that positive feedbacks greatly outweigh negative ones and that current climate models are likely underestimating potential temperature increases from overloading the atmosphere with carbon dioxide and other heat-trapping gases.
I would add that the study’s authors themselves note in the conclusion:
Possible causes of the excess warming include increased production and levels of trace greenhouse gases as a consequence of the climatic warming (such as CH4).
Given that some of the fastest warming on the planet is occurring right where the most methane is stored (see here), the methane feedback remains the biggest worry in the entire carbon cycle.