Despite a slowdown in recent years in the rate of global warming, the world remains on a path to substantial and potentially disruptive climate change.
Global carbon dioxide emissions from the burning of fossil fuels and the production of cement reached a record high of 36.1 billion tonnes in 2013, and are now more than 60% above the level of 1990, when the Intergovernmental Panel on Climate Change (IPCC) released its first report. Compared to 2012, emissions grew by 2.3% last year and are likely to increase by a further 2.5% in 2014.
The new figures were released on 21 September by the Global Carbon Budget, a group that regularly analyses changes in carbon sources and sinks.
CO2 emissions continue to track the high-end scenarios used by the IPCC in its latest report to project the magnitude of global warming. Without sustained mitigation measures — including capturing and storing the carbon produced by power stations — the world is likely to warm by 3.2–5.4 °C above pre-industrial levels by the end of the century.
“It is getting increasingly unlikely that global warming can be kept below 2 °C,” says Glen Peters, a climate scientists at the Center for International Climate and Environmental Research in Oslo. “In any case, the challenge is getting bigger every year and might be unachievable without our betting on negative emissions.”
The dire outlook — detailed in a package of research articles and commentaries in Nature Geoscience and Nature Climate Change — comes on the eve of a climate summit convened by the United Nations on 23 September in New York. At the meeting, world leaders aim to prepare the ground for an international greenhouse-gas reduction agreement to be signed next year.
“Governments say they agree with the 2 °C target but the urgency of action hasn’t really sunk in,” says Corinne Le Quéré, a climate scientist at the University of East Anglia in Norwich, UK, and a co-author of the studies. “We have already used up two-thirds of the fossil fuels we can afford to burn if we want to have a reasonable chance to stay below 2 °C warming. At the rate at which CO2 currently accumulates in the atmosphere, the remaining emissions budget will be exhausted in 30 years.”
When the latest set of IPCC emissions scenarios were developed about ten years ago, many experts had expected the ‘carbon intensity’ of the world economy’s to decrease by 2% to 4.5% per year. But that has not happened — mainly owing to China’s continued reliance on coal as the main energy source for its growing economy, the actual decline in the amount of fossil fuel used to produce 1% of global gross domestic product was merely about 1%. Given current projections of global economic growth, emissions are unlikely to peak and reverse any time soon in the absence of more stringent energy policies.
Despite its increased efforts to reduce pollution, China surpassed the United States as the world’s largest emitter of CO2 in 2007 and is now emitting more than the US and the European Union combined. China’s pro capita emissions are still not as high as those in the US, but in 2013 they were higher than the EU’s. Together, the three regions account for more than half of worldwide emissions.