The Max Planck Institute in Jena, Germany has just put out a press release in English on a new study on the role of terrestrial ecosystems in the global carbon cycle: A new balance for the global carbon balance. If anything, the report shows there remains lots of uncertainty in the science that many like to call “settled”.

In climate science the only certainty is uncertainty.

Well worth reading. Some of the main points, according to the authors:

1. In most ecosystems, the photosynthesis rate at which plants fix carbon dioxide from the atmosphere changes relatively little as the temperature varies.

2. The respiration of the ecosystems, when flora and fauna release carbon dioxide again, also increases to a lesser extent than has recently often been assumed when the temperature rises.

3. Moreover, this temperature dependence is the same all over the world – even in ecosystems as different as the tropical savannah and the Finnish needleleaf forest.

4. The climate is quite temperamental: countless factors are involved and many feedback mechanisms enhance effects such as the anthropogenic greenhouse effect. This makes it difficult to make predictions, especially as many processes in the Earth system are still not completely understood.

5. Results suggest that the availability of water, in particular, plays a decisive role for the carbon cycle in ecosystems. It is often more important than temperature.

6. Particularly alarmist scenarios for the feedback between global warming and ecosystem respiration thus prove to be unrealistic.”

7. The factor which determines the acceleration of the respiration thus obviously does not depend on the local temperature conditions and the specific characteristics of an ecosystem. “We were very surprised that different ecosystems react relatively uniformly to temperature variations.”

8. “It is still not possible to predict whether this attenuates the positive feedback between carbon dioxide concentration and temperature,” says Markus Reichstein. “The study shows very clearly that we do not yet have a good understanding of the global material cycles and their importance for long-term developments.”

9. “We were surprised to find that the primary production in the tropics is not so strongly dependent on the amount of rain,” says Markus Reichstein. “Here, too, we therefore need to critically scrutinize the forecasts of some climate models which predict the Amazon will die as the world gets drier.”

UPDATE: There’s also some highly interesting background information here on Fluxnet. http://www.fluxdata.org/default.aspx

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