Geophys. Res. Lett. http://doi.org/t3h (2014)

Credit: © ZOONAR GMBH / ALAMY

The energy balance of the Earth, and therefore the climate system, can be considered in terms of the net imbalance between absorbed shortwave radiation and outgoing longwave radiation at the top of the atmosphere. Positive values indicate that the energy is being added to the climate system, which can manifest as warming of the surface or in the oceans. Increased knowledge of the energy imbalance is needed for understanding the climate system, events such as the recent slowdown in warming and future potential warming rates.

Richard Allan of the University of Reading, UK, and co-workers study satellite data, atmospheric reanalyses and global climate model simulations to reconstruct and investigate changes in the top-of-the-atmosphere net downward radiative flux imbalance. The authors consider the changes for 2000–2012 relative to 1985–1999 and find that there is a larger imbalance in the recent period — 0.62±0.43 W m−2 compared with 0.34±0.67 W m−2. The reconstructed energy balance is able to capture interannual variability, for example, changes due to the Mount Pinatubo eruption and natural climate cycles such as El Niño/Southern Oscillation. The finding for 2000–2012 highlights that surface warming can slow down even with a positive energy imbalance as a result of changes in ocean heat uptake.