The world is heading towards possibly dangerous levels of global warming despite increasing efforts to promote the transition to a low-carbon economy, the Intergovernmental Panel on Climate Change (IPCC) warns in its latest report today.

As the concentration of greenhouse gases in the atmosphere continues to rise to unprecedented levels, the groups says only major institutional and technological change will give the world a better than even chance of staying below 2C warming – the widely accepted threshold to dangerous climate change. Stabilizing greenhouse gas concentrations at 450 parts per million CO2 equivalent – a level which scientists think is needed to limit warming to 2C – will require a three to four-fold increase in the share of low-carbon energies, such as renewables and nuclear, in the global power mix. Improvements in energy efficiency and, possibly, the use of carbon capture and storage technology will be needed to assist the process, the IPCC says.

The report was produced by the IPCC’s Working Group III, which has been tasked with looking into the mitigation of climate change. Its 33-page Summary for Policymakers was approved, line by line, by hundreds of IPCC authors and representatives of 195 governments over the past week in Berlin. Launching the report at a presentation in the city, Ottmar Edenhofer, the co-chair of the working group, admitted the discussions were at times nerve-rackingly tense.

To assess the options, costs and possible adverse side-effects of different pathways to stabilizing emissions at safe levels, the 235 lead authors of the report analysed close to 1,200 scenarios of socioeconomic development and cited almost 10,000 scientific papers. The resulting work, although phrased in rather technical language, is unambiguous in its message that the challenge of climate change is mounting as time proceeds.

“Global emissions have increased despite the recent economic crisis and remarkable mitigation efforts by some countries,” Edenhofer says. “Economic growth and population growth have outpaced improvements in energy efficiency – and since the turn of the century coal has become competitive again in many parts of the world.”

The report makes clear that it would be wise to act now rather than later. But, in line with the IPCC’s mandate to be policy-neutral, it includes no specific recommendations as to the energy and related policies that individual countries should follow.

“Substantial investment in clean energies is needed in all sectors of the global economy, including in some parts of the world in nuclear power,” says Edenhofer. “But it would be inappropriate for the IPCC to prescribe reduction targets or energy policies to specific countries.”

Doing nothing is not an option, he says. In a business-as-usual scenario run without meaningful mitigation policies, greenhouse gas concentrations double by the end of the century, the working group found. This would result in global warming of 4C to 5C above the pre-industrial (1750) level with possibly dramatic consequences on natural systems and human welfare.

Mitigating climate change would lead to a roughly 5% reduction in global consumption, according to the report. But, says Edenhofer, this does not mean that the world has to sacrifice economic growth. In fact, the group found that action to keep temperature rises at bay would reduce global economic growth by no more than 0.06% per year. This figure excludes the benefits of climate mitigation, such as from better air quality and health, which are thought to lower the actual costs of mitigation.

The full report outlines in great detail over 16 chapters the emission reduction potential of sectors including energy production and use, industry, transport and building and land use, and describes how mitigation efforts in one sector determine the needs in others. The IPCC has also assessed the potential of carbon capture and storage technology, which it says would be essential for achieving low-stabilization targets. More ambitious geoengineering possibilities, such as proposals to deliberately reduce the amount of sunlight reaching the Earth’s surface, have not been assessed in the report.

“There is a whole portfolio of mitigation options that can be combined in ways that meet the political priorities of individual countries,” says Edenhofer. “The means to tackle the problem exist, but we need to use them.”

Effective climate mitigation, adds Rajendra Pachauri, the chairman of the IPCC, will not be achieved if individual nations and agents advance their own interests independently. Nations hope to agree on binding emission reduction targets at a United Nations climate meeting in 2015 in Paris.

Delaying action is getting increasingly risky and will only lead to tougher requirements and higher costs at a later stage, says Pachauri.

“We haven’t done nearly enough yet,” he says. “A high-speed mitigation train needs to leave the station soon and all of global society needs to get on board.”