Following are some of the main findings of a draft report by the U.N. climate panel due for release in Bangkok on Friday.
The report by the Intergovernmental Panel on Climate Change (IPCC) looks at the costs of mitigating and adapting to climate change and the tools available to achieve reductions of greenhouse gas emissions.
Scientists and government officials are meeting from Monday to review and approve the draft, the third of four to be released this year.
"Without additional climate mitigation and/or appropriate sustainable development policies global greenhouse gas (GHG) emissions will continue to grow over the next few decades," it says.
It adds it there needs to be immediate action to curb emissions if there is to be any significant long-term impact on limiting climate change.
Yet, based on current projections, global carbon dioxide (CO2) emissions from fossil fuel combustion are predicted to rise by a minimum of more than 40 percent between 2000 to 2030.
A large portion of this increase is projected to come from developing countries, the report says.
Transport is a major worry with growing use of cars and planes pushing up greenhouse gas emissions. In 2004 transport energy use amounted to 26 percent of total world energy use.
"Unless there is a major shift away from current patterns of energy use, projections foresee a continued growth in world transportation energy use by 2 percent per year, with energy use and carbon emissions about 80 percent above 2002 levels by 2030."
Emissions from aircraft would continue to rise by 3 to 4 per cent per year despite projected improvements in aircraft fuel efficiency because these will be largely surpassed by traffic growth of around 5 percent each year.
Agriculture was another concern.
"Global food demands may double by 2050, leading to intensified production practices (e.g. increasing use of nitrogen fertilizer). In addition, forecast increases in consumption of livestock products will increase methane and nitrogen dioxide emissions if livestock numbers increase".
TOOLS AND RESEARCH
It says GHG levels can be stabilised using "a portfolio of technologies that are commercially available today and those that are expected to be commercialised in coming decades, provided appropriate incentives are in place".
These included fuel switching, more efficient power plants, nuclear power, renewable energy, more efficient buildings and building materials and lighting, more efficient appliances and improved agricultural practices to curb the release of methane and nitrogen oxide, two other major greenhouse gases.
"A positive "price of carbon' would create incentives for producers and consumers to significantly invest in lower carbon products, technologies and processes. However, additional incentives related to direct government funding and regulations are also important."
The more deep and rapid the emissions cuts, the more costly to economies, says the report, which gives a range of stabilisation levels of greenhouse gases in the future.
Greenhouse gas concentrations are now at about 430 ppmv of carbon dioxide and rising sharply. Carbon dioxide accounts is the main greenhouse gas, followed by methane and four others covered by international pacts.
"For trajectories towards stabilisation levels between 445 and 535 ppmv CO2-equivalent, costs are lower than 3 percent global GDP loss."