One Dutch car rental company adds about one percent to its prices to help plant forests to soak up the vehicles' emissions of carbon dioxide, a nontoxic gas widely blamed for raising global temperatures and wreaking havoc with the climate.

In pinprick attacks on global warming, some companies and individuals are finding that some consumers are willing to pay to try and curb global warming.

Some people are even paying to offset everything from commuting to family vacations by measuring how much carbon dioxide is released by the oil, coal and gas they burn.

"We made Helen's wedding 'carbon neutral' to make the point that climate change is a serious issue," said Helen's father, Phil Cottle.

He estimated the wedding emitted about 13 tons of carbon dioxide.

Some scientists say global warming is the biggest long-term threat to life on Earth. Rising temperatures could drive thousands of species to extinction, trigger more frequent floods or droughts and sink low-lying islands by raising sea levels.

'SMALL ACTIONS CAN ADD UP'

"Small actions among very many people can add up to significant changes," said Jonathan Shopley, the head of Future Forests, which offsets carbon dioxide by investing in renewable energy schemes or planting trees, mainly in the Third World.

Trees suck carbon dioxide from the atmosphere and store it as they grow, helping curb global warming widely blamed on carbon dioxide emissions from factories and cars that are blanketing the planet and have surged since the Industrial Revolution.

Future Forests has planted about 3,700 acres of trees since 1999, from Scotland to Mozambique, to absorb about 103,000 tons of carbon dioxide. In contrast, annual global carbon dioxide emissions are about 26 billion tons.

Groups like Future Forests, Dutch Business for Climate or Germany's 550ppm, let people calculate personal carbon dioxide emissions and determine how many trees would offset those emissions.

Increasing numbers of events, from rock concerts to conferences, have aimed at being "carbon neutral."

The 2002 Johannesburg Earth Summit was the first major U.N. meeting to try to be "carbon neutral," investing in renewable energy and planting trees. But few governments signed up, raising just $300,000 of a $5 million target.

Some environmental groups worry that schemes for planting trees could actually backfire and extend global pollution.

"The idea that people can burn fossil fuels and then plant trees to clean up is simply wrong," said Steve Sawyer, climate policy director at Greenpeace, noting car exhausts spew out pollutants other than carbon dioxide.

"This will keep people digging up oil and coal," he said. The world should instead shift to clean energy, like solar, wind or hydro power, he said.

U.S. citizens are the biggest carbon dioxide emitters with an annual average of 19.4 tons each. Japanese emit 9.1 tons, while the average Ethiopian accounts for just 100 kg.

Cottle, a forestry and insurance expert, said travel accounted for 7.7 tons at his daughter's wedding, followed by hotel stays at 4.8 tons under estimates by Future Forests.

"Luckily, no one came from Australia," he joked.

KYOTO STALLED

The Kyoto protocol, a global government plan for limiting emissions of carbon dioxide, was stalled after the United States pulled out in 2001 after President Bush said it was too costly and wrongly excluded developing nations.

The treaty will now take effect if Russia ratifies it.

Part of the problem for policy makers is that carbon dioxide does not sound like a threat. An adult's exhalations produces about one kg a day of carbon dioxide.

The United Nations launched a scheme last year to plant one million trees to help slow deforestation that claims about 23.2 million acres a year.

Dutch Business for Climate manages 123,600 acres of forest, mainly in tropical countries, and gets businesses to help fund plantings to offset carbon dioxide.

"More and more organizations are using (carbon offset) as a selling point," said Denis Slieker, head of the group. "At this stage it's a very, small percentage that's being compensated."