PARIS — Levels of atmospheric carbon dioxide (CO2) are rising annually by around three percent, placing Earth on track for warming that could breach five degrees Celsius (9.0 degrees Fahrhenheit) by 2100, a new study published on Sunday said.
The figure — among the most alarming of the latest forecasts by climate scientists — is at least double the 2C (3.6F) target set by UN members struggling for a global deal on climate change.
In 2011, global carbon emissions were 54 percent above 1990 levels, according to the research, published in the journal Nature Climate Change by the Global Carbon Project consortium.
“We are on track for the highest emissions projections, which point to a rise in temperature of between 4C (7.2F) and 6C (10.8F) by the end of the century,” said Corinne le Quere, a carbon specialist at the University of East Anglia, eastern England.
“The estimate is based on growth trends that seem likely to last,” she said in a phone interview, pointing to the mounting consumption of coal by emerging giants.
Other research has warned of potentially catastrophic impacts from a temperature rise of this kind.
Chronic droughts and floods would bite into farm yields, violent storms and sea-level rise would swamp coastal cities and deltas, and many species would be wiped out, unable to cope with habitat loss.
Developed countries have largely stabilised their emissions since 1990, the benchmark year used in the UN Framework Convention on Climate Change (UNFCCC) negotiations, the study said.
But this achievement has been eclipsed by emissions by China, India, Brazil and Indonesia and other developing economies, which are turning to cheap, plentiful coal to power their rise out of poverty.
In 1990, developing countries accounted for 35 percent of worldwide output of CO2, the principal “greenhouse” gas blamed for warming Earth’s surface and inflicting damaging changes to the climate system.
In 2011, this was 58 percent.
The temperature projections by the Global Carbon Project are at the top end of forecasts published by scientists ahead of the UNFCCC talks taking place in Doha, Qatar.
The study is based on national carbon dioxide (CO2) data and on estimates for 2011 and 2012. Between 2000 and 2011, CO2 emissions globally rose by 3.1 percent annually on average; for 2012, the rise is estimated at 2.6 percent.
Last year, Chinese CO2 rose by 10 percent, or more than 800 million tonnes, equivalent to Germany’s emissions in an entire year, said the Center for International Cimate and Environmental Research – Oslo (CICERO), whose scientists took part in the paper.
“China is emitting as much as the European Union on a per-capita basis, about 36 percent higher than the global average per-capita emissions,” it said in a press release.