The 200-page report by the National Academy of Sciences looked at warming problems that can occur in years instead of centuries. The report repeatedly warns of potential "tipping points" where the climate passes thresholds, beyond which "major and rapid changes occur." And some of these quick changes are happening now, said study chairman James White of the University of Colorado.
The report says abrupt changes like melting ice in the Arctic Ocean and mass species extinctions have already started and are worse than predicted. It says thousands of species are changing their ranges, seasonal patterns or in some cases are going extinct because of human-caused climate change. Species in danger include some coral; pika, a rabbitlike creature; the Hawaiian silversword plant and polar bears.
Comment: Although the authors harp on "human-caused climate change" when the causes may lie elsewhere, the conclusions that changes are non-linear and can reach a tipping point and happen quickly seem correct and show that projections of climate states decades in the future are probably nonsense.
But what's most ridiculous about their conclusions, which contradict the points made in their research, is that they discount the possibility of a radical swing towards cooling. See this for more information on the rapid cooling hypothesis.