I love reading science digested and regurgitated by 'media personalities'. Almost as much fun as undergoing a colonoscopy. This know-nothing seems not to be aware of the basic stoichiometry of photosynthesis: for each molecule of CO2 consumed by the process, a molecule of H2O is also consumed. And -- here's the key point -- in the real world, water is almost always the rate-limiting input in photosynthesis. Put another way, a plant can only use as much CO2 as it's water supply allows, regardless of the atmospheric level of the gas. As for the nonsense about crop yields tracking the rise in atmospheric CO2 -- as any middle-schooler knows, correlation does not imply causation. Hundreds of thousands of studies have shown that the 20th century increases in yields are due entirely to improvements in crop management and genetics.There are many factual reasons to doubt the relationship between rising CO2 levels and global warming, and even the existence of global warming, but claiming that rising CO2 is good for plants is not one of them. As they say about a little bit of knowledge...
It's worth adding that nitrogen, phosphorus, and potassium compounds, as well as close to a dozen different minerals, are more often yield-limiting in the real world than is the availability of CO2. Even the availability of light is a bigger problem in some environments.Consider an automobile assembly line. If you've got ten pre-assembled engines, ten chassis, ten bodies, ten wiring harnesses, and ten transmissions, it doesn't matter how many brake assemblies you accumulate: you can still make only ten cars.
I wondered about that myself, but there's also this piece from the BBC: Rise in CO2 has 'greened Planet Earth' (http://www.bbc.com/news/science-environment-36130346).
Thanks for the link, Frank. I gave the scientific paper referenced by the BBC a quick read: it's a substantive piece of work in a very reputable journal. I'll need to read it more carefully to fully understand the rationale for using satellite measurements of LAI (leaf area index) as a proxy for plant biomass. It seems to me that approach suffers from the same problem as measurements of polar ice caps from space: it can't tell you what's happening below the surface of the imaged area -- in this paper, below the forest canopy. In the case of the Antarctic ice sheet, this problem led to a serious underestimation of ice loss since the sheet is thinning from the underside, driven by increasingly warmer ocean currents sweeping beneath it. Measuring the surface area of ice completely missed the thinning phenomenon.