According to the latest report from the world’s leading climate science body efforts to reduce carbon emissions have not been able to stop greenhouse gases reaching unprecedented levels.
Releasing its Working Group III report in the German capital, Berlin, the United Nations Intergovernmental Panel on Climate Change (IPCC) said the situation required drastic action.
The report warned that energy efficiency improvements had not kept up with economic growth and said delaying action until 2030 could force reliance on technologies to extract greenhouse gases from the air.
“We have a window of opportunity for the next decade, and maximum the next two decades” to act at moderate costs, Professor Ottmar Edenhofer, co-chair of a Berlin meeting of the IPCC, said.
“I’m not saying it’s costless. I’m not saying climate policy is a free lunch, but it’s a lunch worthwhile to buy.”
The UN’s climate chief, Christiana Figueres, said the world should step up action to cut emissions.
“We cannot play a waiting game where we bet on future technological miracles to emerge and save the day,” she said in a statement.
United States secretary of state John Kerry said that every year the world deferred action, the costs only grew.
“These technologies can cut carbon pollution while growing economic opportunity at the same time,” he said in a statement.
“This report makes very clear we face an issue of global willpower, not capacity.”
The report is meant as the main scientific guide for nations working on a UN deal to be agreed in late 2015 to rein in world greenhouse gas emissions that have hit repeated highs, led by China’s industrial growth.
Governments have promised to limit temperature rises to a maximum of two degrees Celsius above pre-industrial times to avert ever more heatwaves, floods, droughts and rising sea levels that the IPCC said were linked to man-made global warming.
IPCC scenarios showed that world emissions of greenhouse gases would need to peak soon and tumble by between 40 and 70 per cent from 2010 levels by 2050, and then close to zero by 2100, to keep temperatures below 2.0°C.
Such cuts are far deeper than most governments are planning.
“Ambitious mitigation may even require removing carbon dioxide from the atmosphere,” the IPCC said.
If countries delay, the world will have to deploy little-tested options, Professor Edenhofer said.
One method mentioned by the IPCC is to burn wood, crops or other biomass to generate electricity and capture the greenhouse gases from the exhaust fumes and bury them underground.
The experimental technology would reduce the amount of carbon in a natural cycle of plant growth and decay.
However there are risks, for instance vast areas of land would be needed to grow biomass, displacing crops and pushing up food prices.
Simpler methods to extract greenhouse gases from the air are to plant trees, which soak up greenhouse gases as they grow.
The IPCC report is the third and final part of a massive UN series, updating science for the first time since 2007.
A summary of the findings will be issued in October.
The IPCC said it was at least 95 per cent probable that man-made emissions, rather than natural variations, were the main cause of warming.
However, many people are doubtful and few governments have policies consistent with a 2.0°C target.
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.
That technology, however, is mostly experimental.
Environmentalists said the focus should be on shifting to renewable energy rather than nuclear power or CCS.
“We need to put our money into the future with a focus on renewables and energy efficiency,” said Samantha Smith of the WWF conservation g