The third installment of the IPCC’s fourth assessment report, published in May, presents an action plan to head off climate change. It sets out a range of scenarios to stabilise atmospheric concentrations of greenhouse gases at between 445ppm and 710ppm of carbon dioxide equivalent.
Stabilising concentrations at the higher end of this range would commit the world to around 6ºC of warming. Conversely, keeping temperatures below 2ºC - the EU target to avoid "dangerous" climate change - would require limiting concentrations to 445ppm.
According to the report, limiting atmospheric concentrations to 445-490ppm, and global temperature rises to 2.0-2.4ºC, will require emissions to peak in 2015 then fall steeply. By 2050, emissions would need to be between 50% and 85% lower than in 2000.
In a second scenario, where action is delayed by five years and concentrations stabilise at 490-535ppm, temperatures would rise by a further 0.4ºC.
The first scenario is rapidly moving out of reach. Current atmospheric levels are about 430ppm and increasing by 1-2ppm per year.
Annual greenhouse gas emissions increased by 70% between 1990 and 2004 to 49GtCO2e and some forecasts predict emissions will rise by another 37GtCO2e (90%) by 2030. Halting and reversing this trajectory in under eight years is a tall order.
But the IPCC says it is possible to rein in emissions with technologies that are either in use at the moment, or will be commercialised in the next few years.
What is more, it is affordable. Keeping atmospheric concentrations between 445ppm and 535ppm, the IPCC says, will cost less than 0.12% of global GDP per year. Although it admits this will not be spread evenly, with some regions and sectors paying more.
Overall, it says that GDP would be less than 3% lower than projected levels in 2030, and 5.5% lower in 2050. To put this into context, the global economy is expected to grow four-fold by 2050.
The report also points out that knock-on benefits in other policy areas like health, energy security and agriculture could "offset a substantial fraction" of these costs.
The panel’s cost estimates are even lower than those in the Stern review published last year. This calculated it would cost about 1% of annual global GDP to keep atmospheric concentrations below 550ppm (ENDS Report 382, pp 34-36 ).
The report is unequivocal that delaying action will make it more difficult to bring concentrations down to a level which would avoid the worst effects of climate change.
It calls for an increase in research and development into low carbon technologies and points out that government funding for energy research is now about half that in 1980.
It also sees a central role for economic instruments like carbon taxes and emissions trading to generate a price for carbon. It says that keeping concentrations below 550ppm equates to a price of carbon of $20-80/tCO2e in 2030, rising to $30-155/tCO2e by 2050.
The IPCC identifies a range of technologies with the largest economic potential for reductions.
On energy, it points out that around $20 trillion will be spent on energy infrastructure over the next two decades and choices made now will impact on greenhouse emissions for years to come.
It estimates that, based on a carbon price of $50/tCO2e, renewable energy could supply around 30-35% of electricity in 2030, and nuclear power could account for 18% - just 2% more than today. It also says carbon capture and storage can make "an important contribution" by 2030.
The report says that these measures could deliver up to 4.7GtCO2e of savings in 2030 if the price of carbon were $100/tCO2e.
Buildings offer the greatest economic potential for reductions. Improvements such as better insulation and microgeneration could deliver cuts of just over 5GtCO2e per year in 2030 based on a carbon price of $20 says the IPCC. This rises to 6.7GtCO2e if carbon reaches $100/tCO2e.
On transport, the report identifies biofuels, improved fuel efficiency and encouraging a switch to public transport as key opportunities, but thinks that the projected increase in transport will offset these savings. It also cautions that simply increasing fuel costs will not lead to significant reductions and a more integrated approach will be needed.
The report sees major potential for emissions cuts from agriculture and forestry. It says that reduced deforestation, and changes in farming practices could deliver more than 7GtCO2e per year at $50/tCO2e, and 10.6GtCO2e per year at $100/tCO2e.
The panel expects cement, steel and ammonia manufacturers to use carbon capture and storage, and foresees the closure or upgrade of older, inefficient plant. Savings from industry could amount to under 5GtCO2e at $50/tCO2e, rising to 5.5Gt/CO2e at $100/tCO2e.
The cost estimates and emissions potential outlined in the report are based on concerted international action. The panel warns that the costs would increase if some regions, gases or sectors are not included. "Greater cooperative efforts to reduce emissions will help to reduce global costs for achieving a given level of mitigation, or will improve environmental effectiveness," it concludes.
The report is aimed squarely at negotiations for a post-2012 international climate agreement. Support for its findings from large emitters like China and the US has raised hopes of moving talks forward.
But a joint EU-US summit on energy and climate change at the end of April suggests that obstacles remain.2
In spite of positive rhetoric emphasising the need for "urgent, sustained global action", the summit failed to come up with concrete actions, only promising to "promote a constructive agenda" in international talks.
"You’ve got to recognise that in order to make progress on greenhouse gases we’ve got to make sure that the developing nations, which are significant emitters, are part of the process," President Bush told reporters after the summit.
The US could shut down its economy and emit no greenhouse gases, but it would only take China 18 months to make up the difference, he argued.
The UK and EU also expressed frustration at the failure to get an agreement on climate change at the UN Commission for Sustainable Development in May.
"The UK and our EU partners came to the table keen to negotiate a progressive outcome," said Environment Minister Ian Pearson. "Regrettably, rather than build consensus on the further steps needed to address these common challenges, many attempted only to reiterate commitments made almost five years ago. This is not progress and does not reflect the increasing urgency with which we need to take action."
All eyes are now on the G8 summit in Germany in June, where moves to establish and link up a series of regional emissions trading schemes will be discussed. But major decisions on a successor to the Kyoto agreement will have to wait until the UN Framework Convention on Climate Change’s climate summit in Bali in December.