FORUM

More than half of Earth’s outgoing longwave energy is in the far-infrared part of the electromagnetic spectrum but this particular part of the spectrum has never been measured before. FORUM, ESA’s nineth Earth Explorer mission, will fill this gap. These measurements are important because Earth’s outgoing radiation at these wavelengths is strongly affected by water vapour and ice clouds, which in turn, play a key role in regulating surface temperatures. FORUM will improve confidence in the accuracy of climate change assessments that form the basis for future policy decisions.