Climate forcing for IPCC
The Intergovernmental Panel on Climate Change (IPCC) is an international institution created by the World Meteorological Organization and the United Nations Environment Programme in 1988 to support climate policy making by assessing scientific findings from climate research groups. The IPCC regularly publishes Assessment Reports: the latest report was published in 2013 and the next is due in 2022. The publication of a new IPCC Assessment Report makes headlines around the world, because the IPCC report provides importance guidance to countries in their efforts to mitigate climate change.
Estimates of climate forcing are an important part of those reports. Climate forcing measures the imbalance in the energy budget of the Earth caused by human activities. It is a crucial quantity to understand historical changes in the energy budget, attribute observed temperature changes to specific human activities, calculate trajectories towards temperature targets like the 1.5°C target enshrined in the Paris agreement, and estimate the committed warming associated with past changes in atmospheric composition.
In its latest Assessment Report, published in 2013, the IPCC used climate forcing estimates provided by the predecessor of CAMS, the Monitoring Atmospheric Composition and Climate (MACC) project. Climate forcing measures how a gas affects the energy balance in the atmosphere, contributing to climate change.
MACC quantified the climate forcing exerted when aerosols of human origin interact with sunlight. Aerosols are the tiny particles emitted into the atmosphere by power plants, transport, and domestic cooking and heating. MACC included a careful analysis of uncertainties affecting its aerosol climate forcing estimates. Based on MACC numbers, IPCC experts revised their estimate of aerosol climate forcing to a smaller magnitude than the previous IPCC assessment of 2007.
The climate forcing estimates of CAMS are covering more than just aerosols: the climate forcings exerted by changes in atmospheric carbon dioxide, methane, and ozone, and their uncertainties, are also quantified.
How CAMS helps
CAMS quantifies climate forcing exerted by carbon dioxide, methane, tropospheric and stratospheric ozone, by the interactions of aerosols with solar and terrestrial radiation, and the interactions between aerosols and clouds. The new estimates that are being produced using the CAMS global reanalysis, a reprocessed data set containing extensive information about the composition of the atmosphere for the period 2003–2017, will bring an important input to the scientific analyses for the next IPCC report.