Global warming requires more frequent rethink of 'normal' weather: U.N.

The baseline for "normal" weather used by everyone from farmers to governments to plan ahead needs to be updated more frequently to account for the big shifts caused by global warming, the U.N.'s World Meteorological Organization said on Wednesday.
The WMO's Commission for Climatology believes rising temperatures and more heatwaves and heavy rains mean the existing baseline, based on the climate averages of 1961-90, is out of date as a guide, the WMO said in a statement.A government trying to decide where to build river flood defenses or a hydroelectric dam based on average rainfall could be misled by the 1961-90 data, for example, while a farmer studying average temperatures might plant crops that wilt in warmer conditions, he said.
Last year, the U.N.'s panel of climate scientists raised the probability that human activities, led by the use of fossil fuels, are the main cause of global warming to at least 95 percent from 90 in a previous assessment in 2007.

http://articles.chicagotribune.com/2014-07-09/business/sns-rt-us-climatechange-normal-20140709_1_warming-wmo-climatology