The increase in the concentration of greenhouse gases in the atmosphere and the associated climate change today make the carbon cycle a core part of climate research. In addition to the atmosphere, the oceans and the biosphere are the main carbon stores, which are in an active interchange with the atmosphere. The rise in the atmospheric CO2 concentration can only be partially compensated by the absorption of CO2 in the biosphere and the oceans.
Forests store approximately half of the terrestrially bound carbon. As forests grow they are enriched with biomass and thereby act as CO2 sinks. The importance of tropical forests is manifested in the fact that tropical forests can store about 50% more carbon than forests outside the tropics. The clearing and destruction of forests causes the bound carbon to be released into the atmosphere. The emissions due to global loss of forest are today the second largest source of CO2. The uncertainties in the carbon flows between the land and the atmosphere are very large in comparison with the other components of the carbon cycle. The main reasons for this are the incomplete monitoring and the lack of knowledge about the biomass in the disturbed and deforested regions.
For the first time, Tandem-L will measure biomass and its seasonal and yearly variation with unprecedented accuracy of 20% on a global scale. This will be a key contribution to drastically reducing the uncertainties in the terrestrial components of the carbon cycle.