Increased atmospheric CO2 levels may be causing increased river flows by allowing plants to photosynthesise more efficiently.

I've written before about the North Atlantic conveyor theory (1, 2) and the belief that the decrease in salinity in is caused in part by increased runoff from Siberian rivers. It had been assumed that this was a result of higher average temperatures reducing the amount of water held as ice. This belief seems pretty unassailable for the Greenland ice sheet (it's thinning measurably), but one scientist has observed that this increased runoff is occuring in many places, presumably in some cases where reduction in ice mass is inadequate to explain the change, and is now looking to the operation of photosynthesis in the presence of increased CO2 concentrations. Apparently one result of CO2 being more readily available is that plants evaporate less water in the process, and therefore absorb less water from the soil to begin with.

I wonder what other side effects are awaiting discovery.

(New Scientist article)