The greenhouse effect that may be cooling the climate - earth - 10 October 2008 - New Scientist Environment

Have a look at this: The greenhouse effect that may be cooling the climate - earth - 10 October 2008 - New Scientist Environment it's interesting because it seems to show that there could be other man-made actions which could help mitigate climate-warming trends. Based on metereological research in Spain relating to the effects of greenhouse agriculture: "In the greenhouse region, air temperature has cooled by an average of 0.3 �C per decade since 1983. In the rest of Spain it has risen by around 0.5 �C. The satellite data revealed that the white greenhouses were much more reflective than farmland."
Of course, the effect of this agriculture on the water table is another story.