Science

Global Warming Acceleration and Recovery

6 February 2025
James Hansen and Pushker Kharecha

Here we make available “Global Warming Has Accelerated,” including the Supplementary Material (SM), in one document and the webinar discussing the paper.



The SM shows that the rate of freshwater injection on the North Atlantic Ocean assumed in “Ice Melt, Sea Level Rise, and Superstorms” was realistic, averaged over the past two decades, but the rate of ice melt did not increase in the past decade. The present acceleration of global warming, which is especially great in the North Atlantic and North Pacific, makes it likely that the rate of ice melt will now accelerate, thus affecting the likelihood of shutdown of the Atlantic Meridional Overturning Circulation (AMOC) and, in turn, the threat of large sea level rise.

The SM, see below, also addresses reactions to our paper. One more comment may be helpful. Why do we say that global temperature will not go down much (i.e., the world is already at +1.5°C and 2025 will be warmer than the kibitzers expect) is only partly due to the ship aerosol forcing – it is due more to high climate sensitivity. We evaluated the 1.7 W/m² darkening of Earth as about 0.5 W/m² ship aerosols, 0.15 W/m² sea ice albedo, but mostly cloud feedback. The cloud feedback operates in both hemispheres and is the main reason that global SST will not fall much and will soon be rising further. The ship aerosol forcing and cloud feedback work together in the North Pacific and North Atlantic, so warming is fastest there, but warming is a global phenomenon.

We have been cooperating with David Beerling and colleagues for years on one the many things that eventually may help restore a propitious climate: actions to accelerate weathering removal of atmospheric CO₂. A new paper on that is just published; we briefly discussed this once and will try to write more soon, but further information is available from the University of Sheffield.

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