Enter a term in the search box to find its definition. Use the controls in the far right panel to increase or decrease the number of terms automatically displayed (or to completely turn that feature off). Whether global warming has accelerated (and how much it has accelerated) is one of the livelier debates in climate science at the moment. The physical case for it is fairly strong: cooling aerosol pollution has fallen substantially over the past two decades while greenhouse gas emissions remain near record highs. The observed rate of warming over the past decade is roughly double what it was over the prior four decades. But showing that this speed-up is statistically distinguishable from the normal year-to-year wiggles of the climate has proven surprisingly hard. A new paper by Jin and Pu in the journal npj Climate and Atmospheric Science argues that the data through 2025 now show a statistically significant doubling of the warming rate. I broadly agree with them that warming has sped up. But the method they use is problematic, and would find a significant acceleration in many simulated worlds where none exists. To start with, let’s look at the data. The figure below fits a single continuous trend line to annual global temperatures since 1970, allowing the slope to change at whichever year fits the data best (2012, in this case). The rate of warming between 1970 and 2012 was 0. 18C per decade (with an uncertainty range of 0. 15C to 0. 20C), while warming between 2012 and 2025 was 0. 35C per decade (0. 26C to 0. 45C). 1
Whether that change is “statistically significant” depends on how you test it. Beaulieu et al.