Continental heat gain in the global climate system

Abstract

Recent estimates have shown the heat gained by the ocean, atmosphere, and cryosphere as 18.2 · 1022 J, 6.6 · 1021 J, and 8.1 · 1021 J, respectively over the past half-century. However, the heat gain of the lithosphere via a heat flux across the solid surface of the continents (29% of the Earth's surface) has not been addressed. Here we calculate that component of Earth's changing energy budget, using ground-surface temperature reconstructions for the continents. In the last half-century there was an average flux of 39.1 mW m-2 across the land surface into the subsurface, leading to 9.1 · 1021 J absorbed by the ground. The heat inputs during the last half-century into all the major components of the climate system - atmosphere, ocean, cryosphere, lithosphere-reinforce the conclusion that the warming during the interval has been global.