Check this out. An international team of climate experts has been looking into the impact of climate on ecosystems, food production, and other aspects of the natural and human-controlled world. They've just come out with the executive summary of their contribution to the Intergovernmental Panel on Climate Change's fourth assessment report. Heavy rains likely in some places, heat waves in others. Some parts of the world may enjoy a better climate for producing food, but for how long is unclear. Other places face serious threats to food. They consider the threat of extinction (which I've written about here, here, and here) particularly dire. "Approximately 20-30% of plant and animal species assessed so far are likely to be at increased risk of extinction if increases in global average temperature exceed 1.5-2.5 degrees C." It's a bit frustrating to read a stark statement like that and not be able to jump directly to the sources on which it is based. I assume it's based on studies like this one, but it's worth bearing in mind that these extinction estimates are a subject of pretty stiff debate. See for example, this recent review. We'll have to wait for the full report, I guess. But even if extinctions turn to to be just half of what's projected here, it would still represent a major event, particularly when you bear in mind that species face many other pressures, from biological invasions to seawater acidification.