Delaying action on global warming will only increase the costs and reduce the options for dealing with the worst effects of climate change, according to a draft report by U.N. experts.

The final draft of the report by the Intergovernmental Panel on Climate Change, obtained Thursday by The Associated Press, says that global warming will continue to increase unless countries shift quickly to clean energy and cut emissions.

It said that despite national policies and international efforts aimed at mitigating climate change, emissions of carbon dioxide and other greenhouse gases that are warming the planet grew 2.2 per cent per year on average between 2000 and 2010, compared to 1.3 per cent per year from 1970 to 2000.

The two main drivers for the increasing emissions are economic growth, which has risen sharply, and population growth, which has remained roughly steady, the report said.

The largest contributor to global emissions results from the burning of oil and coal — and the draft report said its contribution is expected to rise.

Unless "explicit efforts" are made to reduce greenhouse gas emissions, the experts warned that increased conservation and efficiency will not be sufficient to counter their rise.

With increasing demand for energy and the growing use of coal to generate electricity, the experts said emissions from the sector are projected to double or triple by 2050 from the level in 2010 unless improvements in clean energy are "significantly accelerated."

International climate negotiators agreed at the 2009 U.N. climate change conference in Copenhagen that global warming this century must increase by less than 2 degrees (1.1 degree Celsius) from now to avoid the worst impacts of climate change.

Scientists say that target requires atmospheric concentration of carbon dioxide, the main greenhouse gas, to stay below 530 parts per million. The level surpassed 400 parts per million briefly in the spring, but annually it is still barely below 400.

The report said the majority of scenarios to stay below 530 parts per million throughout the 21st century would require a reduction in greenhouse gas emissions between 40 per cent and 70 per cent of 2010 levels by 2050.

The experts said this will require new patterns of investment and a transformation into a low-carbon economy.

The global total annual investment in the energy system is presently about $1.2 trillion, it said.

The experts estimated that in order to stabilize the atmospheric concentration of CO2 between 430 and 530 parts per million investments in fossil fuels would have to decline by $30 billion a year between 2010 and 2029, while investment in non-carbon producing energy sources would have to rise by $147 billion a year.

The report said many renewable energy technologies are increasingly efficient and cost effective, but many still need support if their market share is to increase.

News from © The Associated Press, 2014