Nature also contributes to global warming

A new article by University of Helsinki researchers evaluates the effect of greenhouse gases released from the biosphere on climate change.

Timo Vesala

Thus far, models predicting climate change have primarily taken into account emissions caused by people. However, even detailed knowledge of human-based emissions and their development is not enough. According to the article published in the Nature Geoscience journal, various greenhouse gases and other compounds are also released from the biosphere, the overall impact of which on the climate remains as yet fairly unknown.

The international contributors to the article included also University of Helsinki researchers Atte Korhola, Markku Kulmala, Sanna Sorvari and Timo Vesala.

Lack of nitrogen limits the growth of carbon sinks

Air rich in carbon dioxide and a prolonged growth season caused by warming have led to an increase of carbon dioxide bound in plants.

- This so-called carbon dioxide fertilisation is recognised and taken into account even in models used by IPCC. However, there is a great lack of nitrogen in, for example, the Nordic soil, which curbs the growth of plants in models from what would be otherwise expected, says Timo Vesala, Professor of Meteorology.

Due to carbon dioxide sinks, the models have assumed that the environmental effect of the biosphere curbs warming. However, introduction of nitrogen deficit in the equation may dramatically decrease the curbing impact.

Earth-atmosphere links complex

According to Vesala, other gases studied in the article contribute to global warming. However, it is impossible to directly link the effects of various substances since they are tangled together in a way that is anything but simple.

- The biosphere affects the atmosphere and the composition and temperature of the atmosphere affects the biosphere, says Vesala.

- It is very possible that overall, the biosphere contributes to global warming.

However, Vesala points out that the article focuses on compounds released directly from the biosphere due to climate change caused by people. For example, aerosols and various reactive gases have indirect effects.

The article in the Nature Geoscience journal » »

Text: Milla Karvonen
Photo: Helsingin yliopisto
30.7.2010
Translation: AAC Global
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