The Rio+20 conference on the global environment will be held in Rio de Janeiro on 20-22 June 2012. A large preparatory gathering - Planet Under Pressure - was held in London on 25-29 March to discuss and explore the issues in focus. A particular concern among the 2,800 attendees was that some climate-change “tipping-points” may already be close, or even have passed. 

The latter include the loss of major glacier systems, Arctic sea ice and possibly even the Amazonian rainforest. In all cases, climate change is likely to accelerate as positive-feedback mechanisms kick in, especially methane release from melting permafrost (see “Climate Change Close to Tipping Point, Soon Irreversible”, International Business Times, 28 March 2012).

Both conferences are timely. A 592-page United Nations report published on 28 March - Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation - finds that a "changing climate leads to changes in the frequency, intensity, spatial extent, duration and timing of extreme weather and climate events, and can result in unprecedented extreme weather and climate events" (see "Weather Runs Hot and Cold, So Scientists Look to the Ice", New York Times, 28 March 2012).

An issue in retreat

Earth Summit 2012 will get plenty of publicity; the London meeting is evidence of great concern and engagement among experts, activists and scholars; and the UN report is a valuable reminder of what is at stake. But the overall context is one of receding interest in climate change and (on balance) increased “scepticism”. These trends are developing even as the overwhelming view of climate scientists is that climate change is a peril which requires immediate action (see "An extreme climate: dangers and needs", 4 August 2011).

The disinterest can broadly be attributed to four factors:

* the unwillingness of most politicians to take unpopular short-term measures to prevent long-term problems

* the legitimate concern in many poorer countries that they must attend to more immediate problems

* the successful anti-climate-change arguments put forward by a range of interest-groups: well-funded think-tanks with abundant support from fossil-fuel companies and oil-exporting countries, and convinced ideological free-marketers conscious that government-sponsored actions to limit climate change strike at the heart of free-market thinking (see "Climate science: a peace-studies lesson", 11 March 2010)

* the proving of major oil and gas deposits in several regions, which has (at least for now) muted the arguments about peak oil; in addition, some of the new findings - in Mozambique, Tanzania, Colombia and elsewhere - are in countries desperate for foreign currency.

The net effect of the sidelining of climate change as an issue is that interest has declined in precisely the decade when it is vital to move quickly towards radically low-carbon economies. The first decade of this century was largely lost because of the ideological stance of the George W Bush administration (although many other countries found this a convenient pretext to do nothing); the early years of the second raise the prospect of further loss at the very time when serious economic and social change really must begin.

An early warning

There is, though, a further element in all this which is becoming ever more significant. A pivotal (and well recognised) aspect of climate change is that the process of increasing atmospheric carbon takes many years to have its full effect - and this “lag” means that it may soon become too late for even radical alteration of economic behaviour to suffice to meet the problems created.

It is now also likely that climate change is producing some very potent early warnings of its long-term effects, and it is just possible that these may provide a global “wake-up call”. These markers coalesce around mounting evidence of an increasing number of extreme weather events - known in some circles as “global weirding”. Some of the work being done at the Potsdam Institute for Climate Impact Research points very much in this direction (see "Climate change linked to extreme weather surge", The Register [27 March 2012]; this reports on a paper, "A decade of weather extremes", in the journal Nature Climate Change [25 March 2012] by two Potsdam researchers, Dim Coumou and Stefan Rahmstorf).

The Potsdam work cites the remarkable number of extreme weather events across the world in the first decade of the 21st century. There is not yet sufficient direct proof that climate change is the sole cause, although the clustering of exceptional events is difficult to explain other than in relation to the development of a more disrupted atmosphere stemming from carbon emissions.

The actual number of unusual weather incidents may not be increasing much, but these are becoming more radical. The likelihood is that the trend will continue, and soon become far too costly to dismiss. Such events will in effect become the “canaries” of climate-change disaster; but will the response be sufficient to ensure that essential change comes in time?

There are many precedents where traumatic signals have led to rapid improvement. London's “great stink” in the sweltering summer of 1858 stemmed from untreated sewage in the Thames that made the city unbearable for the elite, let alone everyone else. This was enough finally to spur action; in its wake, the chief engineer of the metropolitan board of works, Joseph Bazalgette, was able to oversee the construction of an enormous sewer system that also brought cholera under control.

Nearly a century later, the “great smog” of London in December 1952 hastened the clean-air acts. In the early 1980s, work by atmospheric chemists and others meant that when, in 1983, British Antarctic Survey staff determined the sheer extent of the “ozone hole” affecting the region each spring, global agreement to ban the pollutants responsible was organised within four years.

The cost in each case was great: cholera had killed tens of thousands in the early 1850s, the great smog killed at least 4,000 people, and the full recovery of the ozone layer will take decades.

This is the contemporary dilemma. For if catastrophic weather events of a “global-weirding” type clearly indicate what has to be done, they may also inflict huge human costs before counter-measures can be effective. The floods in Pakistan in 2010 affected 20 million people and killed 3,000; the European summer heatwaves of 2003 led to tens of thousands of deaths.

These consequences, and the likelihood of much greater disasters, make urgent a recognition of the inescapable need for action. Such a process will require persistence and dedication by researchers, activists, civil-society groups - and perhaps even the occasional wise politician.

The sense of immediacy was expressed at the end of the Planet Under Pressure conference on 29 March, in a statement by its co-chairs Lidia Brito (the director of science policy and capacity-building at Unesco) and Mark Stafford Smith (science director of the Climate Adaptation Flagship). "We really are urging the world to grasp this moment to make history", the "state of the planet declaration" said; for "without urgent action, we could face threats to water, food, biodiversity and other critical resources that create the potential for a humanitarian emergency on a global scale."

The obstacles are huge. The forces ranged against action are powerful and determined. Rio+20 may provide a focus; but however successful and prominent it proves to be, it will do little more than help to catch up on the time wasted over the past decade. This itself indicates both the scale and the speed of the change that is required.