Pacific islanders might sue to try to prevent their low-lying atolls from vanishing under the waves, African farmers could seek redress for crop failures or owners of ski resorts in the Alps might seek compensation for a lack of snow.

"If the evidence (that humans are warming the globe) hardens up, as it may well do, then it has all the ingredients of the tobacco case," said Myles Allen, of the physics department of the University of Oxford in Britain.

But convincing a judge that a country or a company is liable for a fraction of a global problem caused by greenhouse gases -- the effects of which are widely disputed -- may be difficult.

"The legal profession is only now penetrating these issues," said Roda Verhaugen, co-director of the Climate Justice group which mainly advises plaintiffs. "There have been no large awards of damages but there are an increasing numbers of cases."

About 40 people in France have died in a heatwave in Europe in the past week with sweltering July temperatures also in the United States and Canada. In 2003, about 15,000 people died in France and 20,000 in Italy in a heatwave.

This July's heat may be part of normal, unpredictable weather but many scientists say it fits a pattern of warming linked to a build-up of heat-trapping carbon dioxide emitted by burning fossil fuels in power plants, factories and cars.

WARMEST YEARS
The 10 warmest years since records began were all since 1990, and scientists who advise the United Nations project that rising temperatures could cause wrenching changes by 2100. Their next report, due in early 2007, will be pored over by legal experts.

David Karoly, professor of meteorology at the University of Oklahoma, said ever more detailed studies since 2001 indicated that human activities were warming most regions of the world.

The south-east United States and western Asia were exceptions. In parts of Asia, persistent air pollution was apparently blocking some of the sun's rays but it was unclear why southeastern America was escaping the trend, he said.

And some damage could be more easily linked to rising temperatures than others, he said.

"Sea level rise, melting of glaciers and the early flowering of plants are direct responses to higher temperatures," he said. "But other impacts, such as storm damage from hurricanes, are far more controversial."

The United States is the target of most litigation because it produces a quarter of all greenhouse gases. President George W Bush pulled out of the Kyoto Protocol in 2001, the UN pact meant to limit greenhouse gases.

Bush said Kyoto wrongly omitted poor nations from its first goals for 2012 and would cost US jobs.

Experts say companies complying with all laws in the countries where they operate may still be liable to lawsuits. Firms in the European Union, for instance, are curbing emissions under Kyoto while US firms face no mandatory caps.