Matt Ridley heeft een interessant stuk geschreven voor de Spectator getiteld Why climate change is good for the world. Het leunt sterk op het werk van Richard Tol en sluit daarom prima aan bij het vorige blogbericht van Tol zelf.

Zoals de titel al zegt geeft Ridley een opsomming van positieve effecten van de toename aan CO2 en opwarming van het klimaat:

The chief benefits of global warming include: fewer winter deaths; lower energy costs; better agricultural yields; probably fewer droughts; maybe richer biodiversity. It is a little-known fact that winter deaths exceed summer deaths — not just in countries like Britain but also those with very warm summers, including Greece. Both Britain and Greece see mortality rates rise by 18 per cent each winter. Especially cold winters cause a rise in heart failures far greater than the rise in deaths during heatwaves.

Over de effecten van CO2 schrijft hij:

The greatest benefit from climate change comes not from temperature change but from carbon dioxide itself. It is not pollution, but the raw material from which plants make carbohydrates and thence proteins and fats. As it is an extremely rare trace gas in the air — less than 0.04 per cent of the air on average — plants struggle to absorb enough of it. On a windless, sunny day, a field of corn can suck half the carbon dioxide out of the air. Commercial greenhouse operators therefore pump carbon dioxide into their greenhouses to raise plant growth rates.

The increase in average carbon dioxide levels over the past century, from 0.03 per cent to 0.04 per cent of the air, has had a measurable impact on plant growth rates. It is responsible for a startling change in the amount of greenery on the planet. As Dr Ranga Myneni of Boston University has documented, using three decades of satellite data, 31 per cent of the global vegetated area of the planet has become greener and just 3 per cent has become less green. This translates into a 14 per cent increase in productivity of ecosystems and has been observed in all vegetation types.

Dr Randall Donohue and colleagues of the CSIRO Land and Water department in Australia also analysed satellite data and found greening to be clearly attributable in part to the carbon dioxide fertilisation effect. Greening is especially pronounced in dry areas like the Sahel region of Africa, where satellites show a big increase in green vegetation since the 1970s.

Het is goed dat Ridley dit onderwerp aansnijdt. De positieve effecten van CO2 en opwarming zijn te lang vrijwel onbespreekbaar geweest en blijven zoals Ridley aangeeft onderbelicht in IPCC-rapporten. Met de lagere schattingen voor klimaatgevoeligheid op basis van waarnemingen is deze discussie alleen maar actueler aan het worden.

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