– How sensitive are wetland methane emissions to changes in temperature and precipitation? This is an important question we need answer to get the model right, says Rona L. Thompson, senior scientist at the NILU, Norwegian Institute for Air Research.
Methane is a greenhouse gas and is the second most important one after CO2. In global climate models, it is important to have the concentrations of greenhouse gases right, as these are important in determining the forcing of temperature. This necessitates having accurate estimates of the emissions of methane, as well as of other greenhouse gases.
In her work for the EVA-project, Rona Thompson is working on inverse modelling for methane emissions in the high latitudes over approximately the past decade.
Observered versus modelled
To estimate methane fluxes from inverse modelling, one needs many measurements of methane concentrations in the atmosphere , from different locations and over long periods of time. In addition, one also needs to account for atmospheric mixing, and we use models for this, which are not too different from weather forecasting models.
– So far we have only examined one year (2009) but what we see so far is that the methane emissions currently used in climate models is less than that which we find from the inversion, which are based on observations, Thompson says.
There are many sources of methane emissions. Methane is released naturally to the atmosphere from wetlands, but human activities are also affecting the emissions, which are also from fossil fuels, agriculture, waste in landfills and, specific to the high north, from melting permafrost.
A future warmer and wetter Arctic means more methane emissions, especially from wetlands. When the permafrost melts, it behaves as a wetland where bacteria, called methanogens, produce methane. Methane, as a greenhouse gas, also has a warming effect, which may lead to more permafrost melting – this is what researchers call a ”positive feedback”:
Methane warms the Arctic, the permafrost melts, more methane is released, and the Arctic becomes even warmer.