As you get more global warming, you should see an increase in the extremes of the hydrological cycle - droughts and floods and heavy precipitation.
James HansenSeveral times in Earth's history, rapid global warming occurred, apparently spurred by amplifying feedbacks. In each case, more than half of plant and animal species became extinct. New species came into being over tens and hundreds of thousands of years. But these are time scales and generations that we cannot imagine.
James Hansen