IT'S CALLED WEATHER:

Global warming is real. It is partly man-made. It will make some things worse and some things better. Overall, the long-run impact will be negative. But some of the most prominent examples of extreme weather are misleading, and some weather events are becoming less extreme.

The U.N. Intergovernmental Panel on Climate Change (IPCC) delivered a 600-page reporton extreme weather in 2011. It got little attention -- because it is nuanced.

Global warming, in general, will mean higher temperatures. This causes more heat waves -- more extreme weather. But it also causes fewer cold waves -- less extreme weather. Many more people die from excessive cold than excessive heat, so fewer people will die from cold and heat in the future. By mid-century, researchers estimated in 2006, that means about 1.4 million fewer deaths per year. In the continental United States, heat waves in the past decade exceeded the norm by 10 percent, but the number of cold waves fell 75 percent.

Moreover, global warming will mostly increase temperatures during winter, at night and in cold places, making temperature differences less extreme.

Global warming will also cause more heavy rain; this is clearly more extreme. But warming will also help alleviate water scarcity -- less extreme. About 1.2 billion fewer people are expected to live with water scarcity by the end of the century because of increased precipitation.

Drought is expected to increase in some regions while decreasing in others. Overall, the impact will probably be slightly more extreme. Likewise, sea levels will rise, which will mean more flooding of coastal structures -- more extreme weather. The total impact is likely to be less than 0.1 percent of global economic output.

Hurricane wind speeds are likely to increase (more extreme), but the number of hurricanes is likely to decrease or hold steady (less extreme). The number of extra-tropical cyclones is likely to decline (less extreme).

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