For once, the climate news might be better than you thought. It’s certainly better than I’ve thought.
You may not have noticed it, amid the flood of bad news about the “Emissions Gap” and the collapse of the COP25 climate conference in Madrid, but over the last few weeks a new narrative about the climate future has emerged, on balance encouraging, at least to an alarmist like me. It is this: As best as we can understand and project the medium- and long-term trajectories of energy use and emissions, the window of possible climate futures is probably narrowing, with both the most optimistic scenarios and the most pessimistic ones seeming, now, less likely.
That narrowing contains both good and bad news — what was recently the best to hope for now seems vanishingly unlikely, and what was the worst to fear much less likely, too. But let’s start with the good news, since there is typically so little of it.
A few weeks ago, the International Energy Agency released its annual World Energy Outlook 2019. The IEA is not known to be optimistic, at least to climate advocates, who have, for years, mocked its projections for future renewable growth: Every year, the agency basically predicts a plateau for renewable use, and every year renewables keep dramatically growing. This made the most noteworthy prediction in this year’s report even more so. According to the IEA report, given only current carbon policies, which nearly everyone studying climate considers terribly weak, the world is on track for about 3 degrees Celsius of warming by 2100, which could, if existing pledges were implemented, be brought down as low as 2.7 degrees — about one and a half degrees less warming than is suggested by the U.N.’s IPCC reports in what is often referred to as the “business as usual” “RCP8.5” scenario.
Now, bear with me, because this is going to get a bit technical, but, I promise, it really does matter. That RCP8.5 scenario is one of four included by the IPCC in their last major assessment report, in 2014, to model possible paths forward — the worst one, tracing the highest arc of emissions and warming outcomes this century. It has shaped a lot of scientific research conducted in the interim; a very common approach is for a particular paper to highlight projected climate impacts in a low-end emissions scenario (either 1.5 degrees or 2 degrees Celsius) and a high-end one (somewhere in the neighborhood of 4 degrees), then describe the low-end outcome as the climate future “if we achieve the goals of the Paris accords” and the high-end one as “business as usual.”
Those deep in the weeds always knew there was something misleading about that characterization, but especially in the aftermath of that IEA report, a very public conversation began, especially on “climate Twitter,” outlining the deep — and perhaps fatal — problems with using RCP8.5 in that way. To begin with, three of the four climate scenarios in the IPCC report were originally devised as “business as usual” scenarios, because none of them reflected, at first, meaningful climate policy.
The assumptions about those factors represent a variety of different no-policy futures, each reflecting different assumptions about the way the world’s energy systems and economies will evolve over the next decades. And the assumptions about those factors which are baked into RCP8.5 seem, by the year, more and more implausible — chiefly that global coal use, which is growing slowly, would dramatically increase over the rest of the century. Given that China is still opening new coal plants, and much of the developing world has yet to reach levels of prosperity where energy use explodes, some growth in coal is probably inevitable, perhaps even dramatic growth. But by 2100, RCP8.5 would require 6.5 times as much global coal use as we have today. That may be possible, given how much we don’t know about the path developing nations in south and southeast Asia and sub-Saharan Africa will take. But given recent drops in renewable pricing, and the positive signs for coal decline in the developed world, as a prediction about energy use RCP8.5 is probably closer to a “worst case,” outlier scenario than anything it would be fair to call “business as usual.”
To be clear, the IEA report only measured emissions from energy use, which is not at all the whole picture when it comes to emissions. RCP stands for “representative concentration pathways,” and theoretically climate feedback loops and other natural processes could deliver those carbon concentrations even if coal use fails to grow at the predicted rate. And it is also the case that some climate impacts are already as bad or even worse than RCP8.5 imagined they could be — arctic ice melt, for instance, including in Greenland, where the ice sheet is melting seven times faster than it was in the 1990s. Plus, the IEA only projects out to 2040, leaving large uncertainties about what would come in the second half of the century. But in a remarkably insightful paper published by the Breakthrough Institute on Wednesday — “in a right and just world, this would be the most high-impact piece of climate writing of the month of December,” the Niskanen Center’s Joseph Majkut said on Twitter — Zeke Hausfather and Justin Ritchie modeled the remainder of the century based on some very conservative assumptions. In one scenario, they assumed emissions would peak in 2040 and hold steady rather than decline until 2100; in the other, they assumed emissions would steadily grow from 2040 until the end of the century. They ran those emissions figures through the IPCC’s own basic temperature calculator and found “that transitions in the global energy system over the past decade mean that a conservative business-as-usual projection of current trends in the energy system continuing is now likely to lead to warming of around 3C by 2100.” Further, while they acknowledge a higher-emissions world than the IEA projects is possible, they conclude that “it may be possible under an optimistic business-as-usual case to have as little as 2.5C warming by the end of the century, though anything below that is very unlikely to happen in the absence of policy given the rate of emissions reductions required.”
The first is that, for all of our earned confidence in the present state of scientific understanding of climate change, there is enormous uncertainty about human response to the challenge of warming. There is a reason the IEA sunsets its projections at 2040 — it’s because projecting things further out is, ultimately, a foolish game. Energy projections as recent as the pre-fracking 2000s are already very much out of date; even more so for those made during the 1970s and 1980s. Projecting what global energy use will be in the year 2100 is the equivalent of trusting projections made in 1940 about where we are today.
This is especially problematic because, ultimately, that range of inputs — how much carbon we put into the atmosphere over the next decades — is the major determinant of warming levels. We can know, with pretty good if not absolute confidence, that putting X amount of carbon into the atmosphere will produce Y amount of warming on a timescale of a century, say. But just how big that X turns out to be is, ultimately, a matter of very gestural guesswork. Whether China’s coal use grows slowly, plateaus and then drops slowly, or drops precipitously over the next two decades — that is not something it is even possible to know, really, though we can guess. Even less possible is knowing whether the next wave of developing nations — India, Indonesia, much of sub-Saharan Africa — will follow the patterns of energy use of the nations just ahead of them on the economic growth. If coal use grows in other parts of the world as dramatically as it did in China in the 1990s and 2000s… well, there are billions of people in those parts of the world, and a rapid energy expansion there could conceivably bring us a lot closer to RCP8.5 than the IEA (or Breakthrough) suggest.
Perhaps a sixfold increase in coal use seems implausible, globally. But even a steady trajectory of coal emissions — new use in the developing world counterbalancing the growth of renewables elsewhere — would be quite bad, if it extended for decades. The IEA predicts it will remain stable, at least for the time being. Exxon, for its part, predicts no decline in carbon emissions from the energy sector through 2040 — and no point, at all, where they reach zero. (By the way, a little-noticed 2018 methane leak at an Exxon plant in Ohio was recently found to have released more of the powerful greenhouse gas than the entire oil and gas industries of many countries.) And we do of course have enough carbon on the planet to reach RCP8.5, should we choose to burn it.
Read the Full report on the link above-
