(Updates with IPCC head comments)

By David Fogarty

BANGKOK, May 4 (Reuters) - Humans need to make sweeping cuts in greenhouse gas emissions over the next 50 years to keep global warming in check, but it need cost only a tiny fraction of world output, a major U.N. climate report said on Friday.

The Intergovernmental Panel on Climate Change (IPCC), in the third of a series of reports, said keeping the rise in temperatures to within 2 degrees Celsius would cost only 0.12 percent of annual gross domestic product.

"It's a low premium to pay to reduce the risk of major climate damage," Bill Hare, a Greenpeace adviser who co-authored the report, told Reuters after the culmination of the marathon talks which ran over their four-day schedule.

"It's a great report and it's very strong and it shows that it's economically and technically feasible to make deep emission reductions sufficient to limit warming to 2 degrees," he said.

"It shows that the costs of doing this are quite modest."

To keep within the 2-degree threshold scientists say is needed to stave off disastrous changes to the world's climate, emissions of carbon dioxide need to drop between 50 and 85 percent by 2050, the report said.

However, technological advances -- particularly in producing and using energy more efficiently -- meant such targets were within reach, the report said.

It highlighted the use of nuclear, solar and wind power, more energy-efficient buildings and lighting, as well as capturing and storing carbon dioxide spewed from coal-fired power stations and oil and gas rigs.

The panel also said for the first time that lifestyle changes could help fight global warming.

It gave no examples, but IPCC chairman Rajendra Pachauri said his personal suggestions included turning down the thermostat and eating less red meat, which could reduce animal methane emissions.

"These are lifestyle measures but you are not going to give up anything and you might gain," he told a news conference.

"ACT NOW"

The report, agreed by scientists and officials from more than 100 countries, reviews the latest science on the costs and ways to curb emissions growth. It is designed as a blueprint for governments to act, without telling them exactly what to do.

However, the message was clear -- the ball was now in the governments' courts, and that delays were no longer acceptable.

"There is no excuse for waiting," European Environment Commissioner Stavros Dimas said.

Pachauri said high public interest would spur governments to act.

"In a democracy, ultimately it is the people who are going to create pressure for change and initiatives," he told Reuters.

In some cases, the panel said, technology could bring substantial benefits, such as cutting health costs by tackling pollution.

Even changing planting times for rice or managing cattle and sheep flocks better could cut emissions of methane, another powerful greenhouse gas, said the report by the U.N. panel which draws on the work of 2,500 scientists.

Its previous two reports painted a grim future of human-induced global warming causing more hunger, droughts, heatwaves and rising sea levels which would drown low-lying islands.

In Bangkok, China and Europe sparred about the costs and levels of greenhouse gas emissions which ought to be allowed.

China, the world's number two emitter of greenhouse gases after the United States, wanted the IPCC report to exclude language which would promote stabilising emissions near current levels, in part because of the limited economic studies available.

The steeper the emissions cuts, the more costly to the global economy, the report says.

In 2030 the cost of limiting greenhouse gases at "stabilisation" levels of between 445 and 710 ppm (parts per million) CO2-equivalent range from a 3 percent decrease of global GDP to a small increase, it said.

However, regional costs might differ significantly from global averages, it added.

Greenhouse gas concentrations are now at about 430 ppm CO2-equivalent. (Additional reporting by Darren Schuettler)

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