Climate change is moving up the global political agenda. Two current developments are helping to build the issue's momentum: the Stern report on the economics of climate change (published on 30 October 2006), and the United Nations Framework Convention on Climate Change conference in Nairobi (6-17 November 2006). A third, the mid-term election results in the United States, may also prove significant in creating space for fresh thinking and policy initiatives in the world's largest producer of greenhouse-gas emissions.

But the momentum can only be sustained if there is clear understanding of what is happening and what needs to be done. That objective informs research commissioned by the London-based Institute for Public Policy Research (ippr) to examine what is required to meet the long-term goal of preventing dangerous climate change. 

The scheduled ending of the first phase of the Kyoto Protocol in 2012 makes the need to advance this goal even more pressing. It is critically important that a shared understanding in the international policy arena is reached rapidly on what level of action is needed in order to avoid dangerous climate change and to shape the next phase of international commitments to be negotiated and long-term investment decisions to be taken by business.

Simon Retallack is head of the climate-change team at the Institute for Public Policy Research (ippr) in London. He is the author of the ippr's report, Setting a long-term climate objective (2005), a contributor to Alternatives to Economic Globalisation: A Better World is Possible (Berrett-Koehler, 2002) and co-author (with Laurent de Bartillat) of a compendium on the world's climate-change challenges, STOP (Seuil, 2003)

The Institute for Public Policy Research (ippr) report, High Stakes: Designing emissions pathways to reduce the risk of dangerous climate change, was published on 8 November 2006

Also by Simon Retallack in openDemocracy:

"Tony Blair and climate change: a change of heart?"
(8 November 2005)

"Ankelohe and beyond: communicating climate change" (17 May 2006)

A model verdict

A key part of this new research work (conducted by Paul Baer and Michael Mastrandrea) has been to develop estimates of emissions pathways that have a high likelihood of keeping the rise in the world's average surface temperature above pre-industrial levels to below 2°C.

The 2°C target, long advocated by European governments, businesses and civil-society groups alike, is far from perfect. Severe impacts and feedback mechanisms that amplify the problem are already occurring at relatively low temperature increases. Nonetheless, the importance of the 2°C objective cannot be overstated. Beyond that threshold, the extent and magnitude of impacts are likely to increase in a way that may widely be considered as being dangerous, and in some cases irreversible.

The likely impacts for a rise of 2°C-3°C include:

• an increase in the number of people affected by water scarcity to 2 billion
• agricultural losses extending to the world's largest exporters of food
• the loss of the world's most biodiverse ecosystems - including most of the coral reefs, and irreversible damage to the Amazon rainforest (which could result in its collapse)
• the transformation of the planet's soils and forests into a net source of carbon, causing an additional 2°C-3°C rise in temperature; and an increase in the likelihood of other abrupt changes in climate, such as the slowing-down of the Gulf stream and the loss of the Greenland and west Antarctic ice sheets, which together would raise sea levels by twelve metres.

The stakes are clearly extremely high - high enough to merit seeking strategies that would have a realistic chance of avoiding such impacts. In identifying pathways to achieve that, the latest ippr research incorporates a rigorous quantitative treatment, using a standard method of risk analysis, of each of the key uncertainties in the chain of "cause and effect" between emissions and average temperature increase. These include:

• climate sensitivity (the long-term effect of doubling atmospheric carbon dioxide [CO2])
• ocean-heat uptake
• land-use emissions (from deforestation and other activities)
• the carbon sink (the carbon absorbed by oceans, plants and soils)
• aerosols (small solid or liquid particles from burning fossil fuels and biomass thought to have a cooling effect).

The results of this modelling are explosive, blowing away the dominant view about the scale and speed of action necessary.

A daunting prospect

The research concludes, based on a reasonable set of assumptions, that to have a "very low to low risk" (calculated as a 9%-32% chance of exceeding the 2°C threshold), global emissions of carbon dioxide (CO2) would need to peak by 2010-2013, achieve a maximum annual rate of decline of 4%-5% by 2015-2020, and fall to about 70%-80% below 1990 levels by 2050. This would need to be matched by similarly stringent reductions in the other greenhouse gases.

These calculations are based on scenarios in which atmospheric concentrations of CO2, which stand at 380 parts per million (ppm) today, peak at between 410-421 ppm by around 2050, before falling to between 355-366 ppm by 2100. This in turn is based on the understanding that CO2 concentrations can be reduced by lowering annual emissions below the level of CO2 which is absorbed by global carbon sinks, which currently take up approximately half of the CO2 emitted annually by human activity.

These conclusions go further than the Stern Review's report, which proposes a long-term goal of stabilising greenhouse gases at 450-550 ppm CO2. That range has a medium-to-high risk of exceeding a 2°C rise in temperature.

ippr's research model calculates that scenarios in which CO2 stabilised at 450 ppm had a 46%-86% chance of exceeding 2°C; 500 ppm had a 70%-95% chance; and 550 ppm had a 78%-99% chance. Even more troublingly, these scenarios had an 11%-24%, 18%-47% and 28%-71% chance respectively of exceeding a 3°C rise in global average temperature.

These are not freak, isolated results. This may be the most explicit examination yet of emissions trajectories oriented towards the precautionary 2ºC threshold; but very similar results are beginning to appear from other researchers.

The conclusions will be daunting and deeply unpalatable for policymakers. The fact that global-emissions trajectories are currently heading in the opposite direction makes the level of effort required to bend the global-emissions curve in time an epic one. This is particularly so when it might reasonably be assumed that developed countries will need to make deeper reductions in emissions than developing ones, to allow for a greater degree of equity in levels of per-capita emissions over time. For the rich countries of northern Europe (for example), that could essentially mean preparing to build a zero-carbon economy by 2050.

Also in openDemocracy on the politics of global climate change:

Tom Burke, "Climate change: time to get real" (29 September 2006)

A time for honesty

In the end, policymakers must decide what level of risk is tolerable. But given what is at stake for billions of people, precaution would surely dictate aiming for as low a level of risk as possible. An opposite stance - accepting a high risk today of exceeding 2°C, and being prepared (for example) to take a correspondingly greater chance of seeing the polar ice sheets melting as a result - would be a betrayal of future generations. 

An acceptance of this precautionary stance places us in a new mitigation paradigm, requiring a crash programme to reduce emissions on a far deeper and more rapid scale than envisaged. It will also necessitate a step-change in adaptation to global warming.

This is not a counsel of despair. The technology exists to meet this challenge: we know how to achieve substantial increases in energy efficiency, generate energy without fossil fuels, and reduce emissions from the destruction of forests and soils. The challenge for governments is to adopt the policies and direct the level of resources necessary to do this in time.

It is the timetable for action, above all, that our research shows we urgently need to rethink. We do not have decades in which to bend the global CO2 curve: we have less than ten years. What we do now at the global level will be of critical importance.

The United States can no longer sit on the fence: it needs to adopt a national cap on its greenhouse-gas emissions without further delay. The developed world will need to continue to do the most, but the highest-emitting developing countries such as China will also need to be engaged far more substantially and far sooner than previously thought, with developed countries almost certainly needing to prepare to pay for the bulk of climate-mitigation efforts there.

All of this will be enormously difficult. The current political environment - even allowing for the signs of progress in awareness noted at the outset of this article - means that much of it will be portrayed as unrealistic, even utopian. The gap between what is necessary and what seems feasible clearly looms large. But to avoid significant risks of appalling global harm, we simply must reimagine what is feasible.

And if, at the end of the day, we conclude that the challenge is simply too great, we should at the very least be honest about the risks we are incurring and imposing on others.