In reply to Rick Monteverde's message of Wed, 21 Nov 2007 16:52:51 -1000: Hi, [snip] >Robin - > >>As the temperature rises, more water evaporates. >>This is a positive feedback loop. The effect of >>the CO2 is thus leveraged by water vapor. > >..and then it rains. Big moderator to the loop.
See Michel's reply. > >>To make matters worse, the tundra is melting too, >>and also yielding up both CO2 and CH4 (another strong >>greenhouse gas). Yet another positive feedback loop. > >...then it snows on the tundra again. Positive feedback loops can work either way. That is, they enhance existing trends. The last few decades have shown us that the current trend that is being enhanced, is a warming trend. In short, the amount of snow falling on the tundra is decreasing, and melting ever more rapidly, leading to longer ice free periods. There are too additional effects that I didn't mention in my previous post, both relevant to the polar regions. 1) As ice is replaced by open water the reflectivity drops considerably, increasing the amount of sunlight absorbed. 2) Water evaporates more readily than ice, so the average humidity also increases more readily as the amount of open water increases, which means that more heat is not only absorbed (see 1), but also retained. Regards, Robin van Spaandonk The shrub is a plant.
