"Measures to reduce emissions can, in the main, be achieved at starkly low costs especially when compared with the costs of inaction," said Achim Steiner, executive director of the UN Environment Programme (UNEP). "Indeed some, such as reducing emissions by 30% from buildings by 2020, actually contribute positively to GDP [gross domestic product]. It is now up to governments to introduce the mechanisms and incentives to unleash the ingenuity of the financial and technological markets in order to realize these economic, social and environmental gains."

Working Group III looked at scientific, technological, environmental, economic and social aspects to report on mitigation of climate change.

The body found that, without additional action, emissions of the greenhouse gases covered by the Kyoto Protocol - namely carbon dioxide, methane, nitrous oxide, sulphur hexafluoride, PFCs and HFCs - are likely to rise by 25-90% by 2030 over their levels in 2000.

But, according to the IPCC, governments could stabilize greenhouse gas levels by adopting stronger climate change policies. If global carbon dioxide emissions peaked by 2015 and fell to 50-85% of 2000 levels by 2050, greenhouse gas levels would stabilize at 445-490 parts per million (ppm). That would potentially limit global mean temperature increases to 2-2.4 °C above pre-industrial levels. If emissions peaked later, the associated temperature increase would probably be larger. For comparison, in 2005 greenhouse gas levels were around 379 ppm.

The report examines ways of reducing emissions from seven key sectors: energy supply, buildings, transport, industry, agriculture, forests and waste. The IPCC says that the best approach is a diversified portfolio of policies addressing all major sectors, since no one sector or technology can address the entire mitigation challenge.

Working Group III also believes that there are gaps in currently available knowledge on some aspects of climate change mitigation, particularly in developing countries. "Additional research addressing those gaps would further reduce uncertainties and thus facilitate decision-making related to mitigation of climate change," says the group's summary for policymakers.

The IPCC will release a Synthesis Report for its fourth assessments in November.

• The full Fourth Assessment Report on the physical basis of climate change conducted by IPCC working group I is now available online.