Without "more ambitious policies", greenhouse gas emissions will increase to almost 685 parts per million (ppm) by 2050, says a report by the Organisation for Economic Cooperation and Development (OECD).
This is well above the 450 ppm required to maintain the global temperature rise at two degrees Celsius, widely considered to be a cut-off point to avoid catastrophic knock-on effects.
OECD Environmental Outlook to 2050 — whose climate change chapter is published ahead of next week's UN climate change conference (COP 17) in Durban, South Africa (28 November–9 December) — says that mitigation pledges made so far are "not enough", and that time to tackle rising emissions is running out.
This rise in emissions will vary around the world. Regarding forestry and land use, net carbon dioxide emissions are projected to be negative by 2045, while emerging economies will also show a decreasing trend in emissions thanks to an expected slowing of deforestation. But in Africa, land use emissions are projected to increase driven by the expansion of agricultural areas on the continent.
"Technological innovation is key for the transition to a low-carbon economy," the report says.
The availability of technology options, such as nuclear and renewables, as well as emerging technologies (e.g. carbon capture and storage), is crucial for implementing efficient mitigation strategies.
The cost of mitigation could be halved to just two per cent of GDP (gross domestic product) by 2050 if investment in R&D produces breakthrough technologies, it claims.
"[The] costs of inaction are very significant," said Simon Upton, director of the OECD's environment directorate. "Without policies that promote [the development of] technologies, the cost of mitigation will be higher."
The report highlights technology support as one of the main policy tools for climate change mitigation.
It recommends a robust intellectual property rights system and help for the public to buy low-carbon products and services, public and private R&D funding, feed-in tariffs for electricity from renewable sources, and the removal of financial barriers to put green technology in place.
But countries should also establish strategies to deal with a warmer world, which is inevitable given the existing stock of greenhouse gases in the atmosphere.
The full version of the report will be released in March 2012.