A rapid shift to clean technology is needed to counter global warming a new United Nations report has said.
And the study from the UN's Intergovernmental Panel on Climate Change (IPCC), drawing on work by more than 1,000 experts, said a radical shift from fossil fuels to low-carbon energy such as wind, solar or nuclear power would shave only about 0.06 of a percentage point a year off world economic growth contrary to the fears of some.
The report, endorsed by governments, is designed to assess the options for mitigating climate change and is meant to be the main scientific guide for nations working on a UN deal to be agreed in late 2015 to rein in greenhouse gas emissions that have hit repeated highs this century, led by China's industrial growth.
"It does not cost the world to save the planet," Ottmar Edenhofer, a German scientist, co-chair of a meeting of the IPCC, told a news conference in Berlin yesterday.
Governments have promised to limit temperature rises to a maximum 2°C above pre-industrial times to avert ever more heatwaves, floods, droughts and rising sea levels that the IPCC says are linked to man-made warming.
Such levels were still attainable, it said, but policies in place so far put the world on target for a temperature rise of up to 4.8°C by 2100. Temperatures have already risen by about 0.8°C since the Industrial Revolution of the 18th and 19th centuries.
IPCC scenarios showed world emissions of greenhouse gases, mainly from burning fossil fuels, would need to peak soon and tumble by between 40 and 70 per cent from 2010 levels by 2050, and then to almost zero by 2100, to keep rises below 2°C.
"There is a clear message from science: To avoid dangerous interference with the climate system, we need to move away from business as usual," said Edenhofer.
He added that the review had found many pathways that led to a future which kept the world within the 2C goal.
"All of these require substantial investments. Avoiding further delays in mitigation and making use of a broad variety of technologies can limit the associated costs," he said.
Low-carbon energies, which accounted for 17 per cent of world energy supplies in 2010, would have to triple or quadruple their share by 2050, displacing conventional fossil fuels as the top source of energy, IPCC scenarios showed.
Low-carbon energy can include coal, natural gas or oil-fired power plants if they use carbon capture and storage (CCS) to bury emissions underground, but that technology is mostly experimental, and costly.
The IPCC said that natural gas, which emits fewer greenhouse gases than coal, could get a boost until about 2050 and add “ambitious mitigation may even require removing carbon dioxide from the atmosphere". Delay in acting to cut emissions until 2030 would force far greater use of such technologies, a 33-page summary for policymakers said.
One method would be to burn wood, crops or other biomass to generate electricity, capture the greenhouse gases from the exhaust fumes and bury them underground, it said.
The experimental technology would reduce the amount of carbon in a natural cycle of plant growth and decay, but there are risks, such as the need for vast land areas to grow biomass, which would displace crops and push up food prices. A simpler method to remove these gases from the air is to plant trees that soak them up as they grow, the IPCC says.
Prof Stuart Haszeldine, Professor of Carbon Capture and Storage at the University of Edinburgh, said: “Extraction and combustion of fossil carbon can only continue if that easy energy is matched, tonne for tonne, by the recapture and storage of carbon. It doesn't matter if that is by CCS, by Bio Energy Capture and Storage, by direct air capture, or by enhanced mineral weathering – all of these will be needed.
“The important things are to make a start – and sooner than 2030 – embedding carbon budgeting into every business and every behaviour, and make these actions sustainable without destroying natural ecosystems or diversity with biomass farms.”
The report did not mention ‘geo-engineering’ options, such as placing giant mirrors in space to bounce sunlight away from the Earth. "At this point in time, it's not a policy option, Pachauri said.
Many world leaders welcomed the IPCC report, even as it underscored they were not doing enough. "This report makes very clear we face an issue of global willpower, not capacity," US Secretary of State John Kerry said.
The IPCC report is the third and final part of a massive United Nations series, updating science for the first time since 2007. A summary of findings will be issued in October. The IPCC says it is at least 95 per cent probable that man-made emissions are the main cause of warming.