So it turns out global warming isn't that bad after all.
That's exactly the conclusion Justin Ritchie doesn't want the world to draw from the paper he just published.
And for a good reason. It's wrong.
Ritchie, a Ph.D. candidate in resources and the environment at the University of British Columbia, was working as a teaching assistant in 2013 and trying to come up with assignments for his students. Looking through "business as usual" and worst-case scenarios for the emission of carbon dioxide into the atmosphere, he saw that reliance on coal for energy started ramping up around 2040.
"Why is that?" he remembers asking himself.
The question evolved into his dissertation work—and to the most provocative conclusion of his study, published last month to little fanfare in the journal Energy Economics. Inflated coal estimates had become at some point "a virtually unlimited backstop supply [that] has misinformed a generation of long-term energy scenarios," Ritchie and his co-author, UBC professor Hadi Dowlatabadi, write in their paper. The estimates reflected all geologically identified coal, not the fraction it may be possible to dig out.
In other words, Ritchie and Dowlatabadi found, there may not be enough accessible coal to fuel the worst-case scenario of global warming.
"For the past quarter-century, high emission baselines have been the focus of research, explicitly or implicitly shaping national policy benchmarks, such as estimates for the social cost of carbon," the paper says, referring to the dollars-per-ton measure used by government and business to factor future climate damage into today's spending.
That sentence flies pretty close to the white-hot center of the climate policy debate in Washington. Quantifying the "social cost of carbon" is an arduous process that has become a highly politicized issue. Steep costs from capping coal emissions have been baked into policy for years, "and realistically I don't know if that can hold up anymore, if you take the 'coal backstop' out," said Ritchie, who is doing his Ph.D. work at UBC's Institute for Resources, Environment and Sustainability.
The surge in global coal production has produced a much more refined understanding of coal deposits around the world. Armed with those refinements, researchers have slashed their estimates of the amount of economically and technologically recoverable coal by two-thirds from '90s-era forecasts. When the UBC researchers analyzed the worst-case scenario for 21st century carbon dioxide emissions, using the revised coal estimates, they found that CO2 emissions fell dramatically.
"When I first found all this out, in 2015, it was somewhat of an existential crisis in a way," Ritchie recalled. "I said, 'Oh man, am I really right about this?'"
"This" could help the scenario developers rethink what they feed to climate modelers. For its most recent comprehensive review, published in 2013 and 2014, the research community created scenarios of several possible futures for greenhouse gas emissions in this century. Being scientists, they call these models "representative concentration pathways," or RCPs. Ritchie was most interested in the extreme scenario, RCP 8.5. In a 2011 summary of that pathway, the developers wrote that “coal use in particular increases almost 10 fold by 2100.”
To get to the dark future of RCP 8.5, Ritchie found, you'd have to burn more coal than anyone should expect to be dug up. This pathway for future warming, often considered a business-as-usual scenario, wasn't likely.
The discovery that there's a whole lot less coal to burn would seem a gift to skeptics of climate change and opponents of climate policy. But Ritchie's paper is a double-edged sword. The same finding that shrinks CO2 emissions may also lower the cost of dealing with global warming, making the Paris Agreement that addresses climate change easier to achieve.
The paper's findings align with real-world trends in reduced coal use, particularly in the U.S. and China, said Gary Yohe, an economics and environmental studies professor at Wesleyan University. The future of coal demand is changing at least as quickly as supply estimates. Because of a growing public outcry in China over the deadly, soot-filled air of many of the nation's cities, Yohe expects the Chinese government to “leave a lot of coal in the ground that they already know is there.”
“The quotable take on that is it doesn't matter what Donald Trump says about opening coal mines," Yohe said. "He’s not going to generate any more jobs for coal miners, because who’s going to open those mines?”
Global leadership on climate change is passing from the U.S. as President Trump unwinds his predecessor's policies. China's emissions have either been flat or have dropped by a percentage point every year since 2013. India decided recently that some planned coal plants may not be needed, as the nonprofit Climate Action Tracker said last week.
It all adds up to progress in the climate fight, Yohe said. If Trump were to withdraw the U.S. from the Paris climate accord, it wouldn't be as devastating to the accord's goals as it might appear, he said, "because it’s the cities and the states, like California, and businesses all across the country who have already decided they’re going to reduce their carbon footprints.”
To better understand how carbon-emission projections are made, Ritchie undertook the soul-destroying task of reading all five climate-change assessments published since 1990 by the Intergovernmental Panel on Climate Change (IPCC), the authoritative but not bestselling scientific body. That cost him about a month. The work was funded, in part, by the Pacific Institute for Climate Solutions and by National Science Foundation funding awarded through the Carnegie Mellon Climate and Energy Decision Making Center.
Ritchie found that RCP 8.5, created for the most recent report, relies on two-decade-old coal assessments and assumes that within the next 20 years or so, other energy sources will fall away, leaving coal to pick up the slack. Since his work suggests there isn't enough recoverable coal to bring about that grisly world, how would future energy demand be satisfied?
By natural gas, for one. If it makes up the difference, emissions projected in the RCP 8.5 scenario would fall by 15 percent. If clean energy makes up that demand, emissions would be 30 percent lower, Ritchie and Dowlatabadi write.
Which brings us back to the conclusion Ritchie fears some will draw, and makes it crucial to understand two things.
First, the findings don't change greenhouse-gas physics or even the likeliest projections of global warming. If his research proves valuable to others, Ritchie said, it might just push more attention to the next-most-severe CO2 pathway, RCP 6.0. That world isn't one anybody would want to live in, either, even though it may be the one we're setting course for.
Second, there are plenty of ways to keep the carbon burning without coal. Even if Ritchie and Dowlatabadi are right, we may get slammed by something like an RCP 8.5, said Noah Kaufman, a climate economist at the World Resources Institute. "This seems like a plausible emissions pathway to consider," he said, "and perhaps the heavy use of coal is just a proxy for advances in high-carbon technologies that will enable this pathway," such as tar sands or frozen methane sheets in the ocean called hydrates.
If there's one thing fossil-fuel companies have proved to be amazing at, it's discovering fossil fuels.
Emissions have been holding steady over the past three years. But there's a world of difference between a halt in the rate of emissions growth and the end of emissions. Coal or no coal, virtually everybody everywhere is still getting up every morning and spending what scientists call our "carbon budget." We might bust it within the next 20 years.
"Even the low-end climate scenarios (e.g. RCP 2.6) would entail significant and widespread climate impacts, so we don't need to invoke the worst case (extremely high coal) scenarios to know that the world is in serious trouble if coal burning continues unabated," Pushker Kharecha, a climate scientist at Columbia University's Earth Institute, wrote in an email. He noted that he hadn't yet reviewed the paper's methods and conclusions carefully.
Ritchie isn't saying we're about to stop burning coal, or that we're about to run out of it. He's just come up with a bullish case for coal burning that may be more realistic than the 1990s bullish case for coal burning.
Before Energy Economics published the study, Ritchie said, he had submitted multiple papers to multiple journals. "Despite getting over 30 peer reviews collected from all of these journals, no one has shot it down," he said, adding that he still has detected a reluctance among some scholars to grapple with his observations.
"Maybe I'm completely wrong about all of this, and here I've written all these papers and there's some critical flaws in them. That's great—tell me about it," Ritchie said. "Please! Someone just read it!"