Causes and effects of Global and Arctic changes in the MEthane budget

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Methane is a main atmospheric compound with abundances determined by natural and man made emissions. It is the second most important anthropogenic climate gas, affecting atmospheric oxidation and air quality and a main component in the carbon cycle. Proce sses determining its distribution and changes are connected with significant uncertainties. As a result of the uncertainties related to future emissions and changes in the oxidation process methane limits the accuracy of climate change predictions. The ov erall objective of this project is to explain the recent increase in atmospheric methane and quantify the effect of realistic future development of atmospheric methane levels. The project focuses on improving the understanding of historic, current and fut ure atmospheric methane budgets. Progress in the understanding will be achieved by multi method approaches: Integration of observations, chemistry transport model (CTM) simulations and radiative forcing calculations. Long-term observations and new isotopi c measurements will be combined with isotope modelling to assess source regions for a wide range of Arctic methane sources. Oslo CTM2 will be used to simulate and assess the effects of emissions changes. Radiative forcing calculations utilising the result s from the CTM simulations and observations will be performed to predict and quantify the effects of changing methane levels on Earth's radiative balance. Also scenarios of extreme global warming and associated large emissions from Arctic reservoir source s will be investigated. As a result, the project will contribute to increased knowledge of the carbon cycle by assessing methane sources as permafrost, wetland, biomass burning, ocean and agricultural emissions. Furthermore the project is expected to prov ide new knowledge of methane as a potential strong biogeochemical climate feedback mechanism and by this reduce the uncertainty in future climate predictions.