Earth's energy imbalance rising faster than expected, and we must keep a close watch

Earth's energy balance is fundamental to the climate sciences as it regulates the flow of energy in and out of the climate system. Currently, it is positive due to anthropogenic greenhouse gas emissions, leading to increasing temperatures in the atmosphere and oceans, melting of the cryosphere, rising sea levels and more extreme weather around the globe. In recent decades the imbalance has risen dramatically, and in 2023 it reached 1.8 Wm-2, or twice as much as expected. 

Monitoring the energy imbalance and the radiation budget components is vital, not only to scientists, but also to guide policy and potentially warn in time in case our projections are wrong. At the same time, NASA's satellites carrying CERES instruments are being decommissioned, and plans are to only launch one Libera instrument to replace them. 

I will provide an overview of a new European initiative to directly measure Earth's energy imbalance from space, the Earth Climate Observatory (ECO), which is being developed by ESA within the 12th Earth Explorer program. The mission uses a constellation of satellites each equipped with an innovative combination of multiple wide field of view radiometers and multispectral cameras to increase the accuracy of the delicate balance between incoming and outgoing fluxes.