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For a moment I thought that John Larkin had raised his game - a whole paragraph and not one mistake.
It might be good for plants, but it's not good for us. There aren't any direct negative effects on humans at the atmospheric levels expected over the next century or so, but the predictable negative effects of global warming on agriculture are appreciable.
Plants do grow faster if exposed to increased CO2 levels, but only if other nutrients are available in excess. In practice plants tend to be primarily limited by the amount of water available - the paleontological record shows that plants tend to react to higher levels of CO2 in the atmosphere by reducing stomata area, so they lose less water while absorbing the same amount of C02.
Global warming is going to increase rainfall, rather than decrease it, but there's every reason to believe that the increased rainfall isn't going to fall in the areas where we want it to fall.
If we keep generating more anthropogenic global warming by burning ever-increasing amounts of fossil carbon and injecting it into the atmosphere as CO2, we will eventually persuade the Greenland ice sheet to slide off into the ocean, raising global sea levels by about six metres. The sort of nitwit optimists that John Larkin listens to are persuaded that the ice sheet will stay put on top of Greenland, and melt in place, which would take thousands of years.
In fact the GRACE satellites show that it is sliding off at an ever- increasing rate
Since the Canadian ice sheet chose to slide off into the ocean at the end of the last ice age, it shouldn't be surprising that the Greenland ice sheet should to be poised to go the same way.
The Antarctic ice sheet will presumably go the same way eventually, raising sea levels by about 60 metres, but that's going to take a little longer. How much longer is hard to predict.
-- Bill Sloman, Nijmegen