The study, published in the journal Climate Dynamics, finds doubling the amount of carbon dioxide (from pre-industrial levels) in the atmosphere is likely to warm the climate by about 2.4 F (1.3 C)* by the time doubling occurs. The Intergovernmental Panel on Climate Change (IPCC), in its latest assessment report, had estimated the value of this quantity known as the “transient climate response (TCR)” to be 33 percent higher, or 3.2 F (1.8 C)*.

The authors, British scientist Nicholas Lewis and Georgia Tech’s Judith Curry, developed a model using historical measurements of temperature and ocean heat content as well as estimates of the levels of particulate matter in the atmosphere to estimate the warming effect of carbon dioxide.

In a blog post explaining the study, Lewis stressed their results “are less dependent on global climate models” than other analyses.