Are we reaching peak emissions?

And will it matter if we are?

Rapid growth of carbon emissions slowed dramatically in 2014 and 2015 in spite of continued economic growth, according to a study published in Nature Climate Change.

The study largely credited a decrease in coal use in China with the decline in global CO2 emissions, along with a slowdown in global petroleum growth and increased use of renewable energy.

The researchers identified China as the world’s top CO2 emitter in 2014, responsible for 27 percent of global emissions, followed by the United States (15.5 percent), the European Union (9.5 percent) and India (7.2 percent).

Jackson RB et al. Reaching peak emissions. Nature Climate Change 2015: doi: 10.1038/nclimate2892

While the findings are hopeful, the study’s authors noted that it’s still not enough. I asked the study’s lead author, Rob Jackson, of Stanford’s School of Earth, Energy, and Environmental Sciences, whether we can confidently say that we’ve reached peak emissions.

“It’s very unlikely,” he said. “It will take another decade or two, at least.  We do think that the emissions trajectory has changed, that the 2.4% growth we saw for a decade is gone.”

Referring to the following graph, Dr. Jackson said, “The straight black line is the 0% growth trajectory. You’ll see that we shoot past two degrees quickly at today’s levels of emissions.”



The 2-degree mark is critical because it is the point at which climate change moves beyond the range humans have been familiar with for hundreds of thousands of years.

Pep Canadell, Executive Director of the Global Carbon Project and one of the study’s co-authors, agreed.

“Even if we had peaked emissions and maintained emissions at about 40 billion tonnes of CO2 per year, the reality is that we would still consumed the remaining carbon budget to 2° Celsius in less than 30 years,” he said.

“So, with or without peak emissions…the situation hasn’t changed much from from a few years ago,” he said. “If we want to keep under two degrees we need to peak very soon and almost immediately start declining emissions at rates above 3%.”

“Peak emissions and zero emissions are a world apart,” said Dr. Jackson.

“We need to reach zero net emissions as quickly as possible.  Only then will CO2 concentrations stabilize.”





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