New research, published in the journal Nature Geoscience, has detected a sustained energy surplus in Earth’s climate and warming below the sea surface since 2000 that is consistent with the continued build up of greenhouse gases in the atmosphere.
Despite an apparent slow down in the rate of global surface warming over the last decade, the research suggests that the planet is steadily accumulating energy, at the rate of 0.5 Watts for each metre squared of the globe – equivalent to the heat of 250 billion kilowatt electric heaters distributed across the globe.
Global climate change results from an imbalance between the amount of sunlight absorbed by Earth and the thermal radiation emitted back to space.
Researchers from the US and British scientist Richard Allan, of the University of Reading, combined satellite measurements and sub-surface ocean observations to estimate the heat entering the planet since 2000.
Measurements of temperatures below the sea surface – up to 1,800m deep, more than a mile down – suggest that the oceans, which absorb nine-tenths of the additional heat caused by man-made global warming, are still getting warmer.
“Our results confirm that energy has indeed been accumulating in Earth’s climate since 2000 and that much of this ‘excess energy’ has been continuing to heat the sub-surface ocean,” says Dr Allan. “Contrary to previous reports of ‘missing energy’ unaccounted for by measurements, our results show consistency between changes in energy entering the top of the atmosphere and reaching the ocean.”
Dr Allan, whose work is funded by the Natural Environment Research Council, was working with US-based colleagues from NASA, NOAA, and the Universities of Hawaii and Miami.
The full paper, ‘Observed changes in top-of-the-atmosphere radiation and upper ocean heating consistent within uncertainty’ (Norman G. Loeb, John M. Lyman, Gregory C. Johnson, Richard P. Allan, David R. Doelling, Takmeng Wong, Brian J. Soden & Graeme L. Stephens (2012)), is published in Nature Geoscience.