Global greenhouse gas emissions have risen to unprecedented levels despite the increasing number of policies to reduce climate change.

According to an Intergovernmental Panel on Climate Change (IPCC) report, emissions increased more rapidly between 2000 and 2010 than in each other the previous three decades.

The Working Group III contribution to the IPCC’s Fifth Assessment Report found that it would be possibleto limit the increase in global mean temperature to two degrees Celsius above pre-industrial levels using a wide array of technological measures and changes in behaviour. However, only major institutional and technological change will give a better than even chance that global warming will not exceed this threshold.

Global greenhouse gas emissions need to be lowered by 40% to 70%compared with 2010 by mid-century, and to near-zero by the end of this centuryto have a likely chance of limiting the increase in global mean temperature to two degrees Celsius.

“Climate policies in line with the two degrees Celsius goal need to aim for substantial emission reductions,” says Ottmar Edenhofe, co-chair of the Climate Change 2014: Mitigation of Climate Change report. “There is a clear message from science: To avoid dangerous interference with the climate system, we need to move away from business as usual.”

The reportanalysed approximately 1200 scenarios from scientific literature. These scenarios were generated by 31 modelling teams around the world to explore the economic, technological and institutional prerequisites and implications of mitigation pathways with different degrees of ambition.

“Many different pathways lead to a future within the boundaries set by the two degrees Celsius 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,” says Edenhofer.

Estimates of the economic costs of mitigation vary widely. In business-as-usual scenarios, consumption grows by 1.6% to 3% per year. Ambitious mitigation would reduce this growth by around 0.06 percentage points a year. However, the underlying estimates do not take into account economic benefits of reduced climate change.