Climate change has made history an inaccurate guide for farmers as well as energy investors who must rely on probabilities and scenarios to make decisions, the head of a United Nations agency said on Wednesday.

Michel Jarraud, director-general of the World Meteorological Organization, said that water and temperature projections have become more valuable than the historical weather data that long governed strategy in agriculture, hydro-electric power, solar technology and other fields.

The past is no longer a good indicator of the future, the WMO chief told a press briefing, describing climate modeling and prediction as key to fisheries, forestry, transport and tourism, as well as efforts to fight diseases such as malaria.

People looking to build energy infrastructure are especially hungry for specific environmental information that can affect the long-term profitability of their projects, he argued.

If in 100 years there is not going to be water going into the dam, it's not a brilliant investment, Jarraud said.

In the farming sector, the Frenchman suggested that guidance passed down through generations about how to prepare and manage crops was becoming less relevant because of changing patterns of heat, humidity and water access around the world.

TRADITIONAL WISDOM

This traditional knowledge is no longer adapted. It's exactly because your grandfather did this that you shouldn't do it, because the context has changed, he said.

This is something completely new -- to make decisions not on facts or statistics about the past, but on the probabilities for the future, he said.

About 1,500 policy-makers, researchers and corporate leaders will meet next week in Geneva to seek to improve the way climate information is collected and shared, among governments and also with the private sector.

That August 31 to September 4 meeting, which will take the pulse of countries who will seek in December to clinch a new global climate pact, is due to include top U.N. officials including Secretary-General Ban Ki-moon and 80 ministers and 20 heads of state or government, mainly from the developing world.

Guide