Earth's Energy Imbalance and Implications

TL;DR

This paper confirms Earth's energy imbalance due to human-made greenhouse gases, highlights the role of aerosols and ocean heat uptake, and discusses implications for future sea level rise and climate modeling accuracy.

Contribution

It provides improved estimates of planetary energy imbalance, aerosol forcing, and critiques climate models' heat mixing assumptions, emphasizing the importance of aerosol effects.

Findings

Earth's energy imbalance during 2005-2010 is 0.59 ± 0.15 W/m2.

Aerosol climate forcing is approximately 1.6 ± 0.3 W/m2.

Ocean heat uptake slowdown was linked to Mount Pinatubo aerosols and solar minimum.

Abstract

Improving observations of ocean heat content show that Earth is absorbing more energy from the sun than it is radiating to space as heat, even during the recent solar minimum. The inferred planetary energy imbalance, 0.59 \pm 0.15 W/m2 during the 6-year period 2005-2010, confirms the dominant role of the human-made greenhouse effect in driving global climate change. Observed surface temperature change and ocean heat gain together constrain the net climate forcing and ocean mixing rates. We conclude that most climate models mix heat too efficiently into the deep ocean and as a result underestimate the negative forcing by human-made aerosols. Aerosol climate forcing today is inferred to be 1.6 \pm 0.3 W/m2, implying substantial aerosol indirect climate forcing via cloud changes. Continued failure to quantify the specific origins of this large forcing is untenable, as knowledge of changing aerosol effects is needed to understand future climate change. We conclude that recent slowdown of ocean heat uptake was caused by a delayed rebound effect from Mount Pinatubo aerosols and a deep prolonged solar minimum. Observed sea level rise during the Argo float era is readily accounted for by ice melt and ocean thermal expansion, but the ascendency of ice melt leads us to anticipate acceleration of the rate of sea level rise this decade.