Climate protesters mass near Heathrow airport

LONDON, Aug 19 (Reuters) More than a 1,000 climate change activists massed near London's Heathrow aiport today and pledged a mix of peaceful protest and civil disobediance to draw attention to the impact of aviation on global warming.

Protest organisers say they plan to occupy the site of a proposed third runway at the world's busiest international airport with a human chain and picket the headquarters of Heathrow's operator BAA through the night.

The protesters want Heathrow's expansion plans dropped and the growth of air travel halted. Their planned action comes at the height of the holiday season at an airport that handles nearly 70 million passengers a year.

Scientists say air transport contributes to global warming, especially as the carbon dioxide gas and water vapour emitted at altitude by planes are four times more potent that at sea level.

The British government is committed to tackling climate change and aims to be the first country to introduce legally binding targets for cutting CO2 emissions.

But it also backs an expansion of air travel, which is set to double in the next 25 years.

The climate change activists have been camped out for a week at Heathrow to the west of central London and more protesters were trickling onto the site today morning. Organisers estimated there were 1,000-1,200 protesters at the camp. They huddled from rain in about 10 large marquees, eating breakfast and making last minute preparations for 24 hours of ''direct action'' which is due to kick off at midday.

''We're hoping that numbers are going to be swelling today because we've widely invited all and sundry,'' activist Peter McDonell told Reuters at the camp.

He said there would also be a variety of ''autonomous acts'', or civil disobediance, but he said he did not know the details.

At least 40 activists have been arrested over the past week after a variety of protests, from attacking an Israeli-owned food import warehouse near Heathrow to super-gluing their hands to doors at the Department for Transport in London.

Heathrow's operators BAA expressed concerns that chaos could ensue. But police said they were confident of being able to maintain control and planned to deploy up to 1,800 personnel.

Groups of police were clustered outside the camp and more were deployed at BAA's headquarters nearby at Heathrow.

''There's been so much media hysteria about baby-eating anarchists. What we're saying is that this is a peaceful protest.

The only thing we are armed with is the consensus of the scientific community,'' said McDonell.

The constant refrain of campaigners was that their quarrel was with the aviation industry, not with passengers. They rejected reports they would make hoax bomb calls or do anything to endanger passengers such as blocking runways.

But police have said they were concerned hardline elements might deviate from the mainstream group and take violent action.

A spokeswoman for Prime Minister Gordon Brown had said peaceful protest was a legitimate right but that any action to disrupt the operation of Heathrow would be ''unacceptable''.

REUTERS RKM BD1619