Climate change sparks events ‘that have not happened in 650,000 years’

By Fiona Harvey in Paris

Climate scientists warned yesterday of a future characterized by extreme weather events — long and intense droughts, fierce hurricanes, heatwaves, and rising Sea levels — as a result of rising temperatures.

 

Scientists now understand much more about how weather systems work, so are able to predict how temperature changes affect rain fall patterns and storms. “You get a range of impacts that will affect people’s daily lives,” said Richard Wood of the UK’s Hadley Centre for Climate Prediction, a lead author of the Intergovernmental Panel on Climate Change report. “Heatwaves will hurt more people, there will be more extreme precipitation causing flooding in some areas while other regions are suffering a lack of rainfall.”

 

Some of these effects will interact. Jonathan Overpeck, professor of atmospheric sciences at the University of Arizona and another lead author of the IPCC report, said: “You get a real one-two punch in coastal areas, because you get rising sea levels and more intense hurricanes [ may cause the sea to surge over coastal land That will make cities like New Orleans much harder to protect.”

The world has warmed by about 0.74°C in the last 100 years, and will warm a further 0.2°C per decade for the next two decades. Rajendra Pacbauri, chairman of the IPCC, said the signals were unmistakable: “We are see ing things that have not happened in 650,000 years.”

    

The IPCC said its “best estimate” was that temperatures would increase by 3°C by the end of the century, if carbon dioxide levels continue to rise as predicted. Such a rise would cause devastating effects in many countries.

Yesterday’s report was confined to the scientific evidence and projections for global warming, leaving considerations of its likely impacts on economics and health for a further report to be published in April How ever, Other studies have found that such a temperature rise would result in serious water shortages for billions of people, lower crop yields, the spread of tropical diseases and the mass migration of people, mainly in developing countries, away from the worst affected areas.

“With hotter temperatures, demand for water for agriculture and natural vegetation will increase,” said Prof Overpeck. “But some places, like the

western US where I come from, rely on snowpack for their water. As the glaciers retreat the water flow will be less.”

Temperatures could rise even higher, by 4°C, if “feed back” effects take place. One such effect would be if thawing Siberian permafrost releases large quantities of methane, a greenhouse gas more potent than carbon dioxide.

 

Another possibility feared by many scientists is that rising temperatures and drought could cause the Amazon rainforest to die. If that were to happen, the vast forest would turn from absorbing carbon from the atmosphere as it does at present to producing carbon dioxide.

The report noted that “the last time the polar regions were significantly warmer than present for an extended period (about 125,000 years ago), reductions in polar ice volume led to four to six metres of sea level rise.”

However, Peter Stott of the UK’s Met Office said although Arctic ice was disappearing, the melting of the massive Greenland ice sheet could take “thousands of years”. Accordingly, the IPCC estimates a sea level rise of between 18 centienetres and 59 centimetres by 2100, compared with the average between 1980 and 1999. But these estimates do not take account of possible feedback effects.