Can North America Offset Its Greenhouse Gas Emissions?

Climate delegates at the COP24 conference in Poland are working to respond to the growing threat from climate change, but recently, a pair of studies came out with alarming news: Greenhouse gas emissions worldwide are accelerating like a “speeding freight train.”  

The new research, published by the Global Carbon Project last week, made clear that rather than being on track to draw down net carbon emissions to zero—a crucial step to mitigating the worse impacts of global warming—the opposite is happening. Unless the most polluting nations—the United States and China among them—make radical changes, including phasing out fossil fuel by 2050, the world will fail to meet its commitment in the 2015 Paris Agreement to keep warming below 3.6°F.  

Another report released last month by U.S. federal scientists, the fourth National Climate Assessment, makes clear that if that happens, we will witness catastrophic consequences never before seen in modern times. 

“We have about a decade to a dozen years to move towards a net-zero carbon-based economy in the United States by the middle of the century,” Brenda Ekwurzel, director of climate science with the Union of Concerned Scientists and a contributor to Chapter 29 of the fourth National Climate Assessment, said in an interview. “Investments in infrastructure would have to happen now, in this decade, for that to happen.” 

But a little-noticed companion report released along with the Climate Assessment, The Second State of the Carbon Cycle report, provided hope that we can still avoid the worst-case climate scenario—what scientists refer to as the “high emissions pathway”—to the worst effects of global warming. In North America, carbon emissions have actually decreased by 23 million metric tons of carbon per year, with the region’s contribution to total global fossil fuel emissions falling from 24 percent in 2004 to less than 17 percent in 2013.  

A picture emerges in the report of how the world can change its course from a high-emissions pathway to a low- or even zero-emissions course. The gradual reduction of fossil fuel use, combined with conservation efforts to protect natural “carbon sinks,” where land and ocean ecosystems remove and sequester carbon dioxide from the atmosphere, could have a major impact on drawing down greenhouse gas emissions. (North American ecosystems alone are responsible for about 11 to 13 percent of carbon removal by plants and soils worldwide, according to the report.) 

Anna Michalak is a researcher at the Carnegie Department of Global Ecology, a major contributor to the carbon cycle report, and lead author to its predecessor, the 2011 U.S. Carbon Cycle Science Plan. “What North America is beginning to show is that you can have a very high standard of living, and you can sustain economic growth, while at the same time reducing net carbon emissions,” she said in an interview. “I think that’s a very powerful message, because it speaks to the false dichotomy some paint between protecting the environment and other things we care about, such as economic growth. There are absolutely win-win solutions.” 

Achieving those solutions requires political will, and the United States has a climate denier in the White House. The Trump administration is seeking to reverse Obama administration policies intended to reduce the nation’s carbon emissions, such as the Clean Power Plan; weaken or eliminate protections for the nation’s “carbon sinks”; and realign the nation’s economy back toward fossil fuels. Should they succeed, North America could quickly see its gains in drawing down greenhouse gas emissions reversed. 

Michalak is part of a community of researchers that, for two decades, has been working to understand how the carbon cycle works within North America in general, and the United States in particular. During that time, a variety of reports have been issued examining how the three top greenhouse gases—carbon dioxide (CO2), methane (CH4), and nitrous oxide (N20)—are emitted into the atmosphere.  

Of all the carbon we emit, whether by burning fossil fuels or land use change like deforestation, roughly half is pulled back out of the air either by the world’s oceans or by the biosphere: plants, trees, soils. “That means we’re only actually seeing about half of the climate change that would be taking place if plants and oceans were not providing this free service to us,” Michalak said.  

The problem is that global warming will have increasingly devastating consequences on that biosphere, potentially turning it from a carbon sink to a carbon source. When forests burn in massive wildfires, that releases additional carbon, and the soil where the trees were will emit still more. But unlike much of the rest of the world, according to The Second State of the Carbon Cycle report, North America shows a net increase in forestation and thus a net uptick in sequestered carbon—more good news.

Even so, in terms of total emissions on a per-capita basis, the United States and Canada are still among the leading countries worldwide. While the Global Carbon Project cited emissions from China as part of the reason greenhouse gas emissions are accelerating globally, on a per-capita basis, China also has three times as many people as the United States. If you divide emissions by the number of people, the U.S. actually emits more.  

If the gains North America has achieved in drawing down its carbon emissions are lost due to Trump’s policies, what will happen in 50 or 100 years? Will plants and oceans continue to suck out half of the carbon we emit, or more, or less? Or might they stop doing it altogether? 

“It becomes this delicate balance,” Michalak said, “of how we are impacting climate and how climate is impacting the earth’s ability to pull some of the carbon back out of the atmosphere and sequester it.” The carbon cycle is all about feedback loops: We emit carbon that changes climate, and by doing so we impact plants and oceans, which in turn affects their ability to pull carbon out of the air, which affects climate right back again, and the whole cycle continues.  

“In terms of solutions,” she continued, “we need a much broader view than just looking at net emissions for each individual country. On a global scale, how do we really turn the corner and start making a dent on how much of our energy comes from carbon-rich sources. For example, a lot of the increase in China comes from the continued development of coal, which is one of the most carbon-intensive ways to get energy. We need to enable a wholesale shift toward renewable forms of energy so we can tackle this on a global level.” 

Michalak, who lives with her family in Northern California, recalls how her kids, ages four and eight, were unable to play outside recently because of the toxic smoke from the Camp Fire, the largest wildfire in state history. The experience had a big impact on her, not just as a scientist but as a mother. She has since been talking to them, she said, about little things that individuals can do that, in isolation, may not save the world but in the aggregate can make a big difference. 

“The feeling I most want to avoid, both for myself and for my kids, is a sense of helplessness or hopelessness,” she says. “Part of what we do, subconsciously in part but also deliberately, is incorporate things in our day-to-day lives that demonstrate that we have choices we can make, and that on a particular level, we as individuals can have an impact.”