Johannesburg — SA MUST begin cutting carbon emissions today in order to avoid steeper and more disruptive reductions later, says the World Wide Fund for Nature (WWF).

However, the Department of Environmental Affairs foresees carbon emissions continuing to rise until 2020, holding steady for 10 years, then beginning to decline in 2030 or 2035.

The WWF, one of the world's largest conservation organisations, on Friday released a proposal for a strict global carbon budget between now and 2050.

This budget, based on a fair distribution between rich and poor nations, has the potential to prevent dangerous climate change and keep temperature rises well below 2° C, the WWF report said.

According to the budget, SA cannot afford to wait until 2030 before cutting emissions.

"Even under the most lenient approach, SA must start reducing today," WWF trade and investment adviser Peet du Plooy said.

Developing countries as a group will need to deviate from emissions predicted under a "business as usual" scenario by between 15% and 30% by 2020.

Richard Worthington, WWF SA climate change programme manager, said this estimate was conservative and the actual cut required may be even higher.

Should these cuts be delayed, the decline in emissions would need to be much steeper in order for global warming to be kept below 2° C. This in turn would mean steeper costs associated with reduction, and the possibility of having to shut down almost- new infrastructure.

"We would be deferring the bill to our kids," Worthington said of such a situation.

"The cheapest way of cutting emissions would be to not make certain investment choices, such as building a smelter," Du Plooy said.

Governments are meeting in Bangkok in Thailand to discuss action on climate change, and will meet again in Copenhagen, Denmark, in December to try and hammer out an agreement to cut emissions.

A successor to the Kyoto Protocol, which provides a framework for the reduction of greenhouse gas emissions, is needed after that agreement expires in 2012.

The WWF report, titled Sharing the Effort Under a Global Carbon Budget, and produced by consultancy Ecofys, shows different ways to cut emissions at least 80% globally by 2050 and 30% by 2030, compared to 1990 levels.

According to the analysis, the total carbon budget -- the amount of tolerable global emissions over a period of time -- has to be set roughly at 1600 gigatons (Gt) of carbon dioxide equivalent between 1990 and 2050.

But because the world has already emitted a large part of this, the budget from today until 2050 is reduced to 970Gt of carbon dioxide equivalent, excluding land-use changes.

Worthington said the WWF wanted the Copenhagen agreement to at least recognise the need to agree to and work to a global budget, which should be incorporated into arrangements for a third commitment period from 2018.

SA is the world's 13th-largest emitter of carbon dioxide, at 10,04 tons per person per year, according to a survey released last month by UK-based risk assessment company Maplecroft. The Department of Water and Environmental Affairs put the figure in 2005 at nine tons per person per year.