When it comes to creating wind, anyone will tell you that temperature differences play a key role. If you remember anything from your geography lessons at school, you’ll know that hot air rises and is replaced by cooler air surging in beneath, causing wind to occur, but is that explanation found in every textbook too simple?
Consider this instead: what if the winds that drive atmospheric circulation are mainly created by the condensation of moisture? This happens mostly in the rainforests, where water evaporates or is transpired by trees, and this is why the environmental wellness experts behind this notion are saying that if we chop down the forests, the winds – and the rains they bring with them – will also be lost.
No one is disputing the physical process itself, as the volume of water vapour is reduced whenever it condenses to form droplets. This lowers the pressure, and allows air to move in, creating wind. However, climate scientists have always regarded the rain forest’s effect on wind as trivial, having no impact on the planet’s wellbeing. The theory was first aired four years ago, and, according to Isaac Held of the US National Oceanic and Atmospheric Administration in Princeton, New Jersey, it has been attacked by critics ever since. ‘This is not a mysterious effect. It is small and included in some atmospheric models,’ he said.
Yet Anastassia Makarieva, a physicist of St Petersburg University in Russia, argues that the pressure gradients cutting down the rain forests would create ‘have never received a theoretical investigation’. According to her calculations, the condensation of billions of litres of water above giant forests is not trivial, but rather produces a giant effect.
Douglas Sheil at Southern Cross University in Lismore, Australia, who co-authored Makarieva’s research, says until critics actually explain why they think Makarieva is wrong, ‘this looks like a powerful mechanism that governs weather patterns round the world..In standard theories, if we lose forests the rainfall in the continental interiors generally declines by 10 to 30%. In our theory, it is likely to decline by 90% or more.’ Yet their theory also suggests that replanting the lost forests could generate enough wind to return rain to even the driest lands on the planet.
Not everyone opposes the theory. Judith Curry of the Georgia Institute of Technology, an author of the standard textbook Thermodynamics of Atmospheres and Oceans, encourages, ‘The process they describe is physically correct. The main question is its relative magnitude compared with other processes.’ She adds that Makarieva and Sheil may have found a way to explain why climate models do not get monsoons and hurricanes right.
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Rainforest Dubbed a ‘Powerful Mechanism’ in Weather Patterns
