- 20 July 2009 by Fred Pearce
- New Scientist Magazine issue 2717. Subscribe and get 4 free issues.
- For similar stories, visit the Climate Change Topic Guide
IT'S like a giant game of Jenga. One by one, pieces of our green future are stacking up, some more precariously than others.
At last week's summit in L'Aquila, Italy, leaders of the G8 declared formally for the first time that the world should not allow global temperatures to rise by more than 2 °C above pre-industrial levels. The group also backed Mexico's plan for a green fund to help the poorest countries develop clean-technology economies.
Meanwhile, in London this week, the shipping industry is meeting to see if it can agree on a way of cutting emissions. Come December, it will be down to UN negotiators to decide which pieces are solid and which are not.
Take the 2 °C target, for instance. The truth is that few climate scientists believe this is possible, even with the G8's proposed target of cutting global emissions of greenhouse gases by 50 per cent by 2050. "An overshoot is inevitable," concluded a recent climate science summit in Copenhagen, Denmark (New Scientist, 21 March, p 6). "Atmospheric CO2 concentrations are already at levels predicted to lead to global warming of between 2.0 °C and 2.4 °C."
Global average temperatures so far have risen by only about 0.8 °C but there are two reasons why warming three times as great seems inevitable. First, there is a time lag of several decades between when greenhouse gas levels rise and when temperatures follow. The lag means there is another 0.6 °C of inevitable warming in the pipeline.
Second, the planet is currently being cooled by about 0.5 °C by aerosols of other man-made air pollutants, such as fine soot and sulphates, which shield the planet from solar energy. This effect should decline in coming decades as countries, particularly in Asia, clean up their air to improve health. Add it all up and we're close to 2 °C above pre-industrial times.
Taking this into account, the World Economic Forum's Global Agenda Council on Climate Change told the WEF meeting in Davos in January that we should aim for a global 80 per cent emissions cut by 2050, which it estimated would give a 4 in 5 chance of staying below 2 °C.
Yet even meeting the G8's lower target of cutting emissions by 50 per cent will require urgent and rapid action on a scale that some have compared to a war effort. "If we want to limit temperature increase to no more than 2 °C to 2.4 °C, we have to peak global emissions no later than 2015. We have six years to bring about a major change in the way we have been doing business all over the world," says Rajendra Pachauri, chair of the UN Intergovernmental Panel on Climate Change. The UK Hadley Centre calculates that to cut emissions by 50 per cent by 2050, emissions everywhere need to stop rising by 2015, then drop by 3 per cent each year (see graph).
"Every decade of delay will raise global temperatures by another half a degree," says Vicky Pope of the Hadley Centre. It also increases the risk that the land and oceans will stop absorbing half our emissions, which could swiftly trigger runaway warming.
Despite the need for early action, the G8 stopped short of explaining how its 50 per cent by 2050 target might be achieved. And even the 50 per cent cut was shaky: the G8 did not give a baseline date from which to measure the cut. Climate scientists make their calculations from a 1990 baseline, but the G8 declaration talks about industrialised countries making cuts "compared to 1990 or more recent years". That matters: emissions today are 38 per cent higher than in 1990.
The G8 declaration is also silent on setting a date after which global emissions must decline, and offers no emission-reduction targets for industrialised nations to reach by 2020. This latter omission, according to German chancellor Angela Merkel, resulted in China and India last week refusing to endorse the 2050 target. It also exasperated UN secretary general Ban Ki-Moon, who said: "The policies that [the G8] have stated so far are not enough. We must work according to the science. This is a political and moral imperative and a historic responsibility."
The G8 did make a nod towards their responsibility to take on the lion's share of fixing the climate problem. Industrialised nations have contributed 70 per cent of CO2 emissions since 1800 even though they have only a fifth of the world's population. Recognising this, the G8 countries agreed that while the world as a whole should cut emissions by 50 per cent by 2050, they should aim for 80 per cent cuts. Still, Martin Khor of the South Centre, a think tank based in Geneva, Switzerland, estimates that this plan will leave the industrialised countries having emitted 200 billion tonnes of carbon more than their "fair share", based on population.
One way of getting around the fairness issue is for the rich nations to help poorer ones develop their industries more cleanly than they did. The potential to curtail rising emissions in developing economies is huge. Many are extremely carbon inefficient, in part because they are at an early stage of development. China, for instance, produces only a fifth as much GDP as the US or Australia for every tonne of carbon emitted.
This opens up the prospect of a global deal in which rich nations stump up cash so that developing nations can "leapfrog" to cleaner energy technologies. This, alongside early cuts in emissions from industrialised countries, will be at the heart of negotiations at the UN Climate Change Conference in Copenhagen in December.
At a little-noticed speech at London Zoo last month, British prime minister Gordon Brown became the first world leader to put a figure on how much all this might cost. He said the developed world needed to contribute $100 billion a year by 2020 to a "green fund" first proposed by Mexican president Felipe Calderón, in return for developing countries agreeing to deviate from "business as usual" economic growth.
Where will this money come from? Brown suggested four options, including a tariff on the airline and shipping industries - two of the fastest-growing polluters. The Kyoto protocol does not cover aircraft and shipping because negotiators could not agree on who should bear responsibility for journeys between countries. Few think that exclusion should continue in the Copenhagen agreement. Brown proposes that, rather than bringing those emissions under the umbrella of national targets, they could become a cash cow for the green fund.
In February, Air France/KLM, British Airways, Cathay Pacific and Virgin Atlantic backed the idea. They want a limited number of emissions permits that they can auction among themselves, setting aside some of the proceeds for the green fund. The four airlines say the arrangement is fair because airlines in the developing world would have to pay up, too, whether or not their national governments faced emissions targets.
Developing-world airlines may object, but an insider at one of the four companies told New Scientist he believed the proceeds could deliver $30 billion a year into the green fund. The shipping industry is meeting at the UN International Maritime Organization in London this week to discuss whether to adopt something similar.
Optimists believe that we are starting to see the bones of a new "green economy" that puts a price on carbon and uses the proceeds to drive down emissions. Many scientists are wary about whether it will achieve the goal of keeping global warming below 2 °C, but whatever their fears, they are prepared to live with some scientific fudge if it delivers political action.
Time is short. Seventeen years ago, 192 governments signed up to a climate change convention that promised to prevent "dangerous" climate change. Arguably, almost two decades of prevarication, including the fearfully weak Kyoto protocol, have made that promise impossible to keep.
Even so, the less warming we allow, the lower the risk that we trigger runaway warming, or sudden sea level rise as ice sheets disintegrate. Such tipping points almost certainly exist above 2 °C of warming. The trouble is, nobody knows quite where.