Hurricane Alex ripped off roofs, flooded streets and forced thousands of people to flee coastal fishing villages today as it pushed into northern Mexico after making landfall as a powerful Category 2 storm.

Global warming may have made Hurricane Gustav slightly stronger and wetter, some scientists said today, but few were rushing to make a specific connection between climate change and stronger storms.

A top US government scientist has performed a U-turn on climate change, saying global warming is not responsible for the recent increase in Atlantic hurricanes.