Earth’s Energy Imbalance: A Satellite Perspective

Climate forcing due to increases in well-mixed greenhouse gases (e.g., CO2 and methane) and the radiative response to the forcing have led to an imbalance between how much solar radiant energy is absorbed by Earth and how much thermal infrared radiation is emitted to space. Presently, Earth is absorbing »1 Wm-2 more energy from the sun than it is emitting to space as infrared radiation. A positive Earth energy imbalance (EEI) is concerning as it leads to increases in global mean temperature, sea level, heat accumulation within the ocean, and melting of snow and sea ice. Satellite and in-situ measurements indicate that EEI has more than doubled since 2000, increasing at a rate of 0.43±0.17 Wm-2 per decade. To put this into context, the cumulative planetary heating since 2000 associated with EEI is a factor of 26 larger than the global direct primary energy consumption for the same period. In this presentation, I will discuss the observations used to track changes in EEI and summarize our current understanding of the factors driving the observed changes. Of particular interest are recent EEI changes: EEI anomalies relative to the long-term average have subsided appreciably owing to an unprecedented and prolonged increase in outgoing longwave radiation. The underlying causes for this will be discussed.