As world leaders prepare to meet in New York to reinvigorate global efforts to tackle climate change, a new study shows carbon dioxide emissions are set to hit record levels. Again.

The Global Carbon Project’s (GCP) annual report warns that if emissions continue to climb, the world will soon pass the point at which it’s likely global warming can be limited to two degrees above pre-industrial levels.

The report’s author Professor Corinne Le Quéré says in a press release that the research shows politicians “need to think very carefully” about how to avert the worst impacts of climate change.

Record emissions

GCP estimates that the world will have emitted 40.3 billion tonnes of carbon dioxide in 2014, a 2.2 per cent rise on last year’s record breaking level.

That’s worrying, as there’s a finite amount of carbon dioxide the world can emit if it’s to curb warming to two degrees above pre-industrial levels – the internationally agreed goal.

The Intergovernmental Panel on Climate Change (IPCC) calls this amount a carbon budget. The budget is an upper limit on total human emissions, from the beginning of the industrial revolution until the day we stop burning carbon.

It says the world must limit emissions to 3,200 billion tonnes of carbon dioxide for it to remain “likely” that warming won’t top two degrees above pre-industrial levels. “Likely” means a 66 per cent chance.

So far, the world has emitted around 2,000 billion tonnes. Unless governments act rapidly to cut emissions, GCP’s research suggests the world will have exhausted the remaining budget of 1,200 billion tonnes by 2045.

Why emissions are rising

Over 90 per cent of global emissions come from burning fossil fuels and cement production. GCP estimates that by the end of 2014, emissions from those processes will have risen by 2.5 per cent compared to 2013.

Annual fossil fuel emissions have only dropped once since 2000 when the global economy crashed, as the chart below shows:

The bulk of emissions from burning fossil fuels come from coal, the most polluting fossil fuel of all:

That’s partly because the US’s shale gas boom pushed lots of cheap coal onto the European market. It’s also because coal demand continues to grow in many developing countries, including India and China.

Who is responsible

GCP hasn’t yet analysed who is responsible for this year’s rise in emissions, as there’s still three months to go. But we can get a fairly good idea by looking at last year’s data.

Given the rate of China’s economic growth and its large population, it’s perhaps unsurprising that the country is responsible for an ever increasing share of global emissions.

In 2013, 28 per cent of global greenhouse gas emissions came from China, and the country was responsible for 58 per cent of the emissions increase compared to a year before.

By way of comparison, the US’s share of global emissions in 2013 was 14 per cent, the EU’s was 10 per cent, and India’s was seven per cent.

The EU was the only major contributor to reduce its emissions in 2013, as the chart below shows. China’s emissions are in red, the USA’s in purple, the EU’s in blue, and India’s in green.

Even when China’s large population is taken into account, it emerges as a major emitter.

China emitted 7.2 tonnes of carbon dioxide per person in 2013, edging past the EU for the first time. The US remains way ahead, however, emitting an 16.4 tonnes per person, as this chart shows:

Note: The numbers on the left axis are lower than those in the text above as they are expressed in tonnes of carbon, not carbon dioxide. To convert to tonnes of carbon dioxide, multiply by 3.67.

India’s large and relatively poor population meant the country only emitted 1.7 tonnes per person in 2013. The global average was five tonnes per person.

Such figures pose a problem for policymakers. China is reluctant to cut its emissions at the same rate as more developed countries because, historically, it has emitted much less. But if China’s emissions continue to grow, the country will quickly eat away at the global carbon budget.

One of the items on this week’s summit agenda will be how to encourage China to slow its emissions growth, with the prospect of reversing the trend in the long run.

After 20 years of negotiating, policymakers are yet to find a way to curb global emissions. Next week’s meeting is meant to enliven the stalled process. The GCP’s carefully timed report shows just how urgent that task has become.