Researchers at the Southern Cross University have proposed that global weather patterns are determined by condensation and evaporation of atmospheric water vapour, and not so much by temperature differences. At the heart of this process is the role played by forests in regulating water vapour content. This provides a new push to the conservation and rehabilitation of forests as a way to mitigate the effects of climate change. Read more

31 January 2013:

New study claims forests cause winds and rain

A new theory of what determines global wind is being taken seriously enough by climate scientists to warrant publication in a top atmospheric sciences journal, says a Southern Cross University researcher.

The radical hypothesis, developed by the University’s Dr Douglas Sheil with a group of international scientists, claims that land cover, particularly the presence or absence of forests, directs weather patterns.

‘Radically novel theories concerning what determines global weather patterns are rare, and fewer still are taken seriously,’ said Dr Sheil, a professor of Forest Ecology and Conservation, in the School of Environment, Science and Engineering.

The peer-reviewed theory is outlined in the paper ‘Where do winds come from? A new theory on how water vapour condensation influences atmospheric pressure and dynamics’, published in the Atmospheric Chemistry and Physics journal.

Dr Sheil said he and his colleagues had advanced a theory that implied that the atmospheric pressure gradients determined by moisture condensation are orders of magnitude greater than previously recognised.

‘Our study concluded that condensation and evaporation – and not temperature differences as traditionally believed – are the major drivers of atmospheric dynamics.

‘Climate scientists generally believe that they already understand the main principles determining how the world’s climate works. However, if our hypothesis is true then the way winds are driven and the way rain falls has been misunderstood.

‘What our theory suggests is that forests are the heart of the Earth, driving atmospheric pressure, pumping wind and moving rain.’

Dr Sheil said the theory was likely to generate fresh calls to action for forest conservation.

‘We need to acknowledge the role of forests in determining wind and rainfall is much greater than previously understood.’

He said he expected opposition to the new ideas.

‘Our theory seems incredible on first impressions. But so far no-one has shown why this theory is wrong, and we are already seeing a few converts who acknowledge that the physics is correct.

‘The important thing now is that these ideas get the full scientific scrutiny and evaluation that they require. Getting this theory into a top journal like Atmospheric Chemistry and Physics is key.’

The researchers argue that the simplifications used in dealing with the complexities of atmospheric motion have ‘thrown out the baby with the bathwater’.

‘The behaviour of the world’s atmosphere is immensely complicated and simplifications and approximations are needed. In textbook climate sciences the pressure differences caused by condensation are stated to be small so they can be ignored. This assumption is true in some cases, but also, as we argue, not in others,’ said Dr Sheil.

He said one remarkable aspect of the theory was the idea that continents could be switched from wet to dry by loss of forests, and that wet climates could, in theory, be rebuilt in regions like the Australian interior through forest restoration.

‘Our theory also explains how declines in both rainfall and rainfall reliability can result from forest loss elsewhere. Such patterns have been observed in various parts of the world and are clearly of major importance for many people – for example those who are suffering from the increasingly irregular monsoon rains in West Africa.

‘We believe the physics is correct. Unless someone can show where we have made an error I believe that these ideas have profound importance for the future of our planet,’ Dr Sheil said.

Atmospheric Chemistry and Physics has pre-empted the revolutionary nature of the scientists’ theory by adding an editor comment at the end of the paper which said, ‘The authors have presented a completely new view of what may be driving dynamics in the atmosphere’.

Further, the handling editor and the journal’s executive committee acknowledge that while the work is ‘highly controversial’ they ‘are not convinced that the new view presented in the controversial paper is wrong’.

‘The editors realise their decision to publish our work reflects an acknowledgment of the need for scrutiny,’ Dr Sheil said.

‘On that basis we hope our ideas will be taken seriously.’

Dr Douglas Sheil is a researcher focusing on tropical forest ecology, management and conservation. He worked in East Africa before completing his doctorate on rainforest dynamics in 1996. He worked at the Centre for International Forestry Research (CIFOR) in Indonesia from 1998 to 2008. From 2008 to 2012 he was the director of the Institute of Tropical Forest Conservation (ITFC) based in the Bwindi Impenetrable National Park in Uganda. Dr Sheil joined Southern Cross University in 2012.

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