The deepening climate crisis

Hurricane Katrina hit South Miami hard, not long after Hurricane Dennis had also wreaked destruction there. Picture / Reuters

The category four storm threatening to cause havoc around the Gulf of Mexico is another example of the way global warming is altering the world's weather systems, environmental campaigners say.

As Hurricane Katrina bore down for a second time on Florida - with New Orleans in Louisiana also in its sights - parts of central Europe were battling to overcome floods that have killed dozens.

Portugal, on the other hand, was in the grip of a new wave of fires caused by high temperatures.

Alarmed residents in Florida have barely had time to clear up damage inflicted by Hurricane Dennis last month, or Hurricane Ivan last September.

Ending a week of extreme weather worldwide, the storm was expected to swing northwards on a course heading somewhere between the southern Florida panhandle and the Louisiana coast.

Florida has been pummelled by six powerful hurricanes since last August, in what forecasters describe as an "unusually active season".

Environmental campaigners say the turbulence is a product of global warming disrupting world weather patterns.

Katrina is the 11th storm of the Atlantic hurricane season, which began on June 1. That is seven more than are usually whipped up by this stage of the season in the Atlantic, Caribbean and Gulf of Mexico, the United States' National Hurricane Centre said. The season ends on November 30.

Katrina's advance is being watched closely in Europe, where many people have felt subjected to comparable celestial punishment this week. From deluged south-eastern Europe, where 43 died in tumultuous rainstorms, to tinder-dry Portugal, where 11 new fires flared in the weekend despite weeks of desperate firefighting, Europeans have been assaulted by weather extremes unknown for generations.

Hardest hit was Romania, where 31 died, many of whom drowned when water engulfed their homes. Austria, Germany, Bulgaria and Switzerland reported 12 dead, with vast areas under water.

Fears remain that floodwaters could cause the Danube to burst its banks. In the small Swiss town of Thun, the local soccer stadium was destroyed, a loss given international prominence by the club's qualification last week for Europe's Champions League tournament.

Experts seeking an explanation for the chaos point to the irregularity of the jet stream, the wriggling ribbon of fast-moving wind that drives Europe's weather from the Atlantic.

A convulsive kink last week whipped turbulence into Eastern Europe, and locked Iberia in its pocket of hot tranquillity.

"But the jet stream is a permanent feature, it always wanders around, that's nothing new," said Wayne Elliott, a weather forecaster from the Meteorological Office in Exeter.

"The jet stream moves north in summer, south in winter, and the important thing is that it didn't come as far south as was expected last autumn. That's why the rains failed in Iberia, and why northern Europe is unsettled.

"Such behaviour is consistent with predictions by scientists who argue the climate is changing. Global warming could be the key."

The World Wildlife Fund said last week: "Global warming has started to exacerbate the frequency and intensity of meteorological catastrophes".

- INDEPENDENT