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Long term growth in CO2 makes for a greener world – what planet are they on?
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Long term growth in CO2 makes for a greener world – what planet are they on?

H. Leighton Steward, described by the Washington Post as an ‘oil veteran’ is behind the launch of two new US groups, CO2 is Green and Plants Need CO2. They’re running ads to promote the idea that CO2 is not a pollutant – in fact, its of benefit to the planet and more of it means a greener world.

The debate over climate change is getting more aggressive, especially in the US, and different viewpoints are rapidly polarising even the business community. Even Duke Energy has pulled out of the American Coalition for Clean Coal Electricity, on the grounds that they didn’t agree with the Coalition’s statements. The science is complicated, which means that disagreements are easy to find.

The latest salvo in the debate is the argument that higher CO2 levels will spur plant growth – which is true. What it doesn’t talk about is the range within which increased CO2 can improve plant growth, and the point at which it becomes a problem.

Back in 2007, a series of reports* published by the Proceedings of the National Academy of Science (PNAS) in 2007 suggested that in coming years, rising temperatures and increased CO2 levels could result in slightly higher crop yields in temperate regions. So far so good. At the same time, the research suggested that adaptation measures adopted at farm level could allow crops to cope with 1–2°C (33.8–35.6°F) of local temperature increases, basically ‘buying time’ to effect changes in carbon levels.

Of course, there’s the problem that any gains in productivity in temperate regions could well be cancelled out by agricultural decline in the tropics, with temperature rises between one and two degrees expected to cut rainfall and send staple crops over their survival thresholds. There would also probably be reduced livestock productivity and loss of cultivated areas in semi-arid and arid regions.  But of course, as that’s not happening at home, why should Steward and his partner Corbin J. Robertson (chief executive of a Houston based coal owner) worry about it.

Even the best case scenario explored by the experts assumed that these crops would survive due to the absence of extreme weather conditions. Unusual weather can, over a few days, wipe out entire crops if the conditions occur during a critical development stage. In one example, citing a case in the Po Valley in northern Italy in 2003, extremely high temperatures caused a record drop of 36% in corn yields*.

Even worse, the PNAS reports suggest that the variables used in simulation models to date have been oversimplified. In general, crop and pasture responses to climate change and corresponding increases in CO2 remain largely unknown. Which means that predictions are likely to be fairly inaccurate. It is suggested though, that the overwhelming body of research indicates that any productivity gains won in the short term regarding higher CO2-related crop yields will be lost in the latter half of the century, as mean temperatures rise between 2º and 3°C (35.6 and 37.4°F) regionally and globally.

So yes, in the short term increased amounts of CO2 might make it easier for us to grow food as the temperature becomes increasingly conducive to plant growth. Then, when it gets hotter still, plants start to fail and water demand increases. That’s not really going to prove helpful in the long run.

 *Proceedings of the National Academy of Science (PNAS), Tubiello, F. N., Soussana, JF., Howden, S.M., Crop and pasture response to climate change, December 2007.
PNAS,Tubiello, F. N., Soussana, J-F., Howden, S.M. Chetri, N. Dunlop, M, Meinke, H., Adapting agriculture to climate change, December 2007.

PNAS, Schmidhuber, J., Tubiello, F. N., Global food security under climate change, December 2007

 

Posted via email from Conquering Carbon


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