The impact that emissions have on the climate partly depends on the land carbon cycle, i.e. how carbon dioxide is absorbed by the biosphere. However, there are other feedback mechanisms within ecosystems that are not included in today’s climate models and that could add to climate change in the future. It is important to take into account these biogeochemical feedbacks in research on climate change, according to an international research group led by ecosystems researcher Almut Arneth from Lund University.

The research group has assembled an overview of the current knowledge on this subject, which has been published in Nature Geoscience on 25 July 2010. In it they describe a range of mechanisms that are linked to a warmer climate: increased carbon dioxide and methane emissions from wetlands, emissions of nitrogen oxides from the ground, emissions of volatile organic compounds from forests, and emissions of gases and soot from fires.

These mechanisms affect the amount of greenhouse gases in the lower atmosphere, including ozone, which not only has an impact on the climate but which also impacts negatively on vegetation and people. These mechanisms become stronger as the temperature rises, while they also contribute to warming the climate.

“A number of these mechanisms have not been well researched. In some cases, we know all too little about how they influence one another, for example how changes in the nitrogen cycle affect the uptake of carbon dioxide by vegetation. Together these could be very significant for the climate”, says Almut Arneth.

Vegetation absorbs carbon dioxide and this currently slows down the rise in temperature caused by the emissions. However, in a warmer climate this ‘damper’ does not work as well and this could mean a significant reduction in the absorption of carbon dioxide by vegetation in the future, in addition to increased release of other climate-active gases.

In a warming climate, the help currently provided by vegetation to slow climate change could become smaller and smaller, say the researchers behind the article in Nature Geoscience. Therefore, their view is that these feedback mechanisms must be taken into account in the calculations in future climate models.

The work has formed part of iLEAPS/IGBP, the Integrated Land Ecosystem-Atmosphere Processes Study from the International Geosphere-Biosphere Programme. The article can be found at http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo905.html.

For more information, please contact Almut Arneth, almut.arneth@nateko.lu.se.