In an interview to UN radio, Jarraud said many socio- economic sectors are highly dependent on climate conditions to make decisions on the long-term nature of projects.
Noting that it is important these decisions be made on the basis of the best possible scientific information, he said that the goal of WMO's World Climate Conference, next week in Geneva, is to link scientists and decision-makers.
In the past, forecasts were made by taking statistics of past decades into account, but "now with climate change, these statistics are changing," Jarraud told UN Radio.
In some areas, global warming will make rainfall less frequent, making the past an unreliable predictor for future precipitation levels, Jarraud said, while heat waves, on the scale of the massive and deadly one which engulfed Western Europe in 2003, "might occur more frequently."
At the same time, he stressed that "there are many lessons to be learned from the past," highlighting the value of climate statistics, UN Radio said.
