1.   But he said that eventually, in the interior of the continent, drought could win out over increasing precipitation if the atmosphere warmed enough.

2.   But, slowly, the atmosphere warmed.

3.   Moreover, experts do not fully understand how water vapor behaves when the atmosphere warms.

4.   The atmosphere warms.

5.   There is much less certainty about the rate at which the atmosphere will warm, and when that will stop.

6.   Some ecologists fear this will cause a catastrophic greehouse-like effect, in which the atmosphere warms and the polar ice caps are melted.