From John Mattocks
Fred Pearce’s excellent article “Keep the planet’s heart pumping” (4 April, p 6), which described how coastal rainforests could cause rainfall to travel inland, stirred a memory from my youth in eastern England.
After the second world war, huge coniferous forests were planted in the Breckland area of Norfolk and Suffolk, replacing what had been sparse bracken, heather and gorse. Local folklore claimed that this forestation resulted in a measurable increase in rainfall downwind of the area, affecting prime agricultural land which previously had typically only 30 centimetres of rain per year. I have never seen scientific substantiation of this, although historical and meteorological records verifying it would support Victor Gorshkov and Anastassia Makarieva’s theory. How good it is to hear a theory that, for once, could enable us to change our habitat for the better.
From Kris Ericksen
While the theory described by Fred Pearce may be a “major driver of atmospheric circulation on Earth”, the pressure drop caused when water vapour turns to water may also be a significant factor in the “billowing shower curtain” problem that has in the past exercised Feedback.
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David Schmidt’s “vortex model” (28 July 2001) does not account for the person in the shower breaking up the vortex, nor does it explain why a low-volume hot shower creates more billowing than a high-volume cold shower. Putting warm water into a plastic bottle, shaking it with the lid partially on and then promptly tightening it demonstrates the pressure drop of water vapour condensing. Hotter water gives a greater effect.
Highbury, Wellington, New Zealand
Alcester, Warwickshire, UK
