Warmist Jeremy Grantham wants to convince us that CO2 depresses crop yields

Can Jeremy Grantham Profit From Ecological Mayhem? - NYTimes.com

Grantham put his own influence and money behind the climate-change bill passed by the House in 2009. “But even $100 million wouldn’t have gotten it through the Senate,” he said. “The recession more or less ruled it out. It pushed anything having to do with the environment down 10 points, across the board. Unemployment and interest in environmental issues move inversely.”
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Having missed a once-in-a-generation legislative opportunity to address climate change, American environmentalists are looking for new strategies. Grantham believes that the best approach may be to recast global warming, which depresses crop yields and worsens soil erosion, as a factor contributing to resource depletion.
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Grantham, who says that “this time it’s different are the four most dangerous words in the English language,” has become a connoisseur of bubbles.

Carbon Dioxide In Greenhouses

The benefits of carbon dioxide supplementation on plant growth and production within the greenhouse environment have been well understood for many years.
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For the majority of greenhouse crops, net photosynthesis increases as CO2 levels increase from 340–1,000 ppm (parts per million). Most crops show that for any given level of photosynthetically active radiation (PAR), increasing the CO2 level to 1,000 ppm will increase the photosynthesis by about 50% over ambient CO2 levels.