Science Daily:

Earth's clouds got a little lower — about one percent on average — during the first decade of this century, finds a new NASA-funded university study based on NASA satellite data.

One theory for this decline...

A consistent reduction in cloud height would allow Earth to cool to space more efficiently, reducing the surface temperature of the planet and potentially slowing the effects of global warming. This may represent a "negative feedback" mechanism — a change caused by global warming that works to counteract it. "We don't know exactly what causes the cloud heights to lower," says Davies. "But it must be due to a change in the circulation patterns that give rise to cloud formation at high altitude."

I usually try to stay clear of the Gaia hypothesis, and mostly agree with Peter Ward's criticism of the hypothesis, and much prefer to call this layer and behavior of matter a biosphere, but a part of me is stuck in agreement with the Soviet biochemist Alexander Oparin: There really isn't an exact line between living and nonliving matter. As a consequence, the old argument about whether or not the earth is a living thing isn't strictly meaningful to me.

  • NASA