World carbon emissions inch upward in 2017, ending hiatus

Following three years of no growth, global greenhouse gas (GHG) emissions from human activities are projected to increase by 2% by the end of 2017, according to the nongovernmental organization Global Carbon Project (GCP). The increase, to a record 37 billion tons of carbon dioxide equivalent, dashed hopes in the environmental community that CO₂ emissions from human activity might have plateaued and begun turning downward.

In a set of three reports published 13 November, GCP said the biggest cause of the increase is the 3.5% growth in China, the world’s largest emitter of greenhouse gases. The country experienced higher energy demand, particularly from industry, and a decline in hydroelectric power due to sparse rainfall.

In addition, the decade-long trend in emissions reductions by the US and the European Union, the second- and third-largest emitters respectively, appears to have slowed this year. The EU’s output hasn’t declined appreciably since 2015. US output declined by 0.4%, compared with a 1.2% average annual reduction during the previous 10 years. Coal consumption in the US inched up 0.5%, its first increase in five years.

India, the fourth-largest greenhouse gas emitter, limited its growth to 2% this year, compared with a 6% jump in 2016. Emissions from all other countries increased 2.3% from 2016, to 15.1 gigatons (see graph below).

Despite the 2014–16 hiatus in global emissions growth, CO₂ has continued to accumulate in the atmosphere at a faster pace than at any time during the 50 years that measurements have been kept. The elevated global temperatures resulting from the 2015–16 El Niño diminished the capacity of terrestrial ecosystems to take up CO₂ from the atmosphere, the GCP reports said.

Corinne Le Quéré of the University of East Anglia, lead author of the principal report that was published in Earth System Science Data, said in an email that she expects emissions to plateau or grow slightly in the coming years. But they are unlikely to return to the 3% growth levels that were seen regularly in the decade that ended in 2010.

Kelly Levin of the nonprofit World Resources Institute (WRI) cautions against reading too much into a single year’s data but also warns about the perilous big picture. “To have a chance of transforming the economy in time to stay below 2 °C, global GHG emissions must peak by 2020,” she says. WRI’s analysis , and another by the United Nations Environment Programme (UNEP), predict on the basis of current trends and treaty commitments that the peak in global emissions won’t occur until after 2030. At that point, the probability of limiting global warming to 2 °C could be as low as 50%, even with accelerated national reduction commitments, rapid abandonment of fossil fuel use, and deployment of carbon-removal technologies whose feasibility hasn’t yet been demonstrated.

The 2 °C mark is thought by most climate scientists to be the threshold below which the worst impacts of climate change can be avoided. The 2015 Paris climate agreement set an “aspirational” goal of limiting temperature increase to 1.5 °C.

The WRI analysis says the number of countries whose emissions have peaked or are committed to peak will increase from 49 in 2010 to 53 by 2020 and to 57 by 2030. Those countries accounted for 36% of world greenhouse gas emissions in 2010 and will represent 60% of the total in 2030, when China has committed to peak its output.

Despite last year’s emissions increase, China’s coal consumption this year is still about 8% below its record 2013 high. The Chinese government has projected a near-doubling of the nation’s solar energy production over the next two years, to 213 GW. China’s nonfossil energy sources make up 14.3% of overall energy production, up by one percentage point in less than a year.