KEY POINTS:
Moving on from the risk of global warming, scientists are now looking for ways to pinpoint the areas likely to be affected by climate change, to help countries plan everything from new crops to hydropower dams.
Billion-dollar investments, ranging from irrigation and flood defences to the site of wind farms or ski resorts, could hinge on assessments about how much drier, wetter, windier or warmer a particular area will become.
But scientists warn precision may never be possible. Climate is so chaotic and the variables so difficult to compute that even the best model will be far from perfect in predicting the future.
"We need to give indications which are at the scale countries can use to make decisions," said Michel Jarraud, head of the World Meteorological Organisation which oversees the UN's climate panel.
"We need to come to a scale which is smaller than countries like Spain or France or the UK. You really need to come to smaller scales - 100km, 200km.
"We are not yet there."
The UN climate panel is meeting in Valencia, Spain, this week to issue a final report summing up more than 3000 pages of findings this year that blamed humans for climate change and outlined solutions.
An Intergovernmental Panel on Climate Change (IPCC) report in April gave regional projections for a warmer climate such as a melting of the Himalayan glaciers or better growing conditions for Nordic forests, but the scale is often too vague to be useful.
Farmers from Africa to Australia would like to know which areas are threatened by desertification. Ski operators from the Alps to the Rocky Mountains wonder how high the snow line will be before investing in new hotels or ski lifts.
But forecasts may never be precise enough to estimate which of two neighbouring valleys in the Andes, for instance, might get wetter and be better suited to a hydroelectric dam.
"To get down to the site-level would be a huge step," said Martin Parry, a British scientist who co-chairs the IPCC section devoted to regional effects of climate change.
The effect of global warming depends largely on how many people keep burning fossil fuels, a main source of greenhouse gases, or develop wind or solar power.
Planners know enough to act in many cases. The smallest grids used for climate projections are 50x50 km.
London is looking into ways to confront risks such as more flooding from North Sea surges up the Thames, more heatwaves and a drier climate.
Painting houses white to protect against heatwaves made sense, Parry said. Homeowners in areas at greater risk of floods could raise electrical goods such as fridges or washing machines off the ground floor.
Parry said some farmers in eastern England were considering selling and moving north to Scotland because they reckoned they could soon grow the same crops on land that costs less now.
A rise in sea-levels is already factored in as a threat. The IPCC projects sea-levels will rise by 18-23cm this century.
- Reuters
