As temperatures rise, thawing permafrost may release large amounts of carbon dioxide and methane into the atmosphere, causing even more warming. At the same time, the disappearance of snow and ice cover—bright, reflective surfaces that help to beam sunlight away from the planet—will cause the Earth to absorb even more heat.
The result is to worsen the progression of climate change even further.
The problem is that these processes haven’t been adequately accounted for, if at all, in many of the models scientists use to make projections about the future. That means previous calculations may be underestimating the damages associated with long-term warming.
The new study, published yesterday in the journal Nature Communications, suggests that the extra costs could amount to nearly $67 trillion over the next few hundred years under a trajectory consistent with the climate action that nations have promised so far under the Paris Agreement—that’s on top of the hundreds of trillions of dollars already predicted in baseline costs from climate change. Researchers estimate that the world would likely experience about 3 degrees Celsius of total warming under such a scenario.
Limiting warming to 1.5 or 2 C, the ultimate goals of the Paris Agreement, would still carry significant extra costs. But the savings could be substantial compared with more severe scenarios. The extra costs in a 2 C world would amount to nearly $34 trillion by 2300 and would come to nearly $25 trillion under 1.5 C of warming.
It’s a much longer-term vision than some other estimates present—many climate change projections tend to focus on 2100 as a benchmark. But the “true impact” of certain climate consequences, like the slow thawing of permafrost, can take centuries to manifest, according to study co-author Kevin Schaefer of the National Snow and Ice Data Center.
“True, we don’t know exactly what society and the economy will look like 300 years in the future,” he told E&E News. “But this is still a useful tool to get an idea of what that will look like in today’s dollars.”
According to environmental economist Amir Jina of the University of Chicago, who wasn’t involved with the research, the exact dollar amounts presented in the study may be less important than the overall indication that tipping elements are an important, and underrepresented, consideration when it comes to climate damage.
The type of model used to conduct the new research is very useful when “thinking about how much certain parameters matter when you’re thinking about climate change and the costs of climate change,” he said.
“I would probably caution something about taking those numbers too literally, but take the implication a little bit more as this is something that got added to the model, and actually it seems to matter a lot within that model.”
Future work may focus more on homing in on the exact economic implications of certain types of tipping elements, he noted. But the research does suggest that, in general, leaving them out of climate impact studies may mean that current estimates of climate damages are still too low.
Accounting for sudden events
Thawing permafrost and melting snow and ice are “two of the biggest feedbacks or tipping points” in the Arctic, according to Schaefer. But they’re not the only ones that interest scientists.
Other factors also have the potential to affect the pace of future climate change. The uptake of carbon by forests and other vegetation is one major uncertainty. Some research suggests that future warming or other human disturbances could cause these sinks to soak up carbon at slower rates or to start releasing carbon back into the atmosphere in some cases, exacerbating the progression of future warming.
Researchers are also becoming increasingly interested in the flow of a major ocean current known as the Atlantic Meridional Overturning Circulation, which ferries water to and from the equator, distributes heat around the world, and helps regulate global weather patterns.
Some scientists have warned that the growing influx of cold, fresh water from the melting Greenland ice sheet may disrupt the current’s flow and cause it to slow down. Some research has begun to address the question of whether the current may eventually, over very long time scales, reach a tipping point that could cause it to collapse.
The ice sheets themselves also pose a major uncertainty about the long-term impacts of climate change. If Greenland or Antarctica were to eventually reach a point of complete collapse, their effects on global sea levels would be catastrophic.
These kinds of processes are likely to unfold over the course of centuries, if they happen at all. On that kind of time scale, their impact could be formidable.
Still, in the meantime, there are other kinds of “tipping points” that may be of much more immediate concern, according to climate scientist Robert Kopp of Rutgers University, who commented on the new study for E&E News. Kopp pointed to the risk of socio-economic tipping points—changes in a society’s ability to respond to or recover from repeated exposure to increasingly extreme weather or other severe climate-related events, such as hurricanes, wildfires or floods.
“Positive tipping points could be you rebuild in the aftermath of these disasters in a way that’s more sustainable and resilient,” he noted. “But a negative tipping point would be a city or region that gets hit by a couple of environmental shocks and never recovers.”
Jina added that not all socio-economic tipping points may necessarily be triggered by sudden events like extreme weather.
“It could be a regular, linear increase in temperature without any dramatic threshold change, and suddenly it triggers this kind of social response which is very disproportionately large,” he said.
The trouble with climate tipping points—both physical and socio-economic—is that they’re still poorly understood and by nature difficult to make projections about. And without knowing exactly when and why they’re likely to occur, it’s also difficult to determine the size of the impact they may have on societies.
But as the new research demonstrates, accounting for the possibility that they may occur is an important step in making sure that policymakers are prepared for all the potential outcomes.
“It’s important to keep it in people’s minds that not all these changes might be these gradual linear changes,” Jina said.
Reprinted from Climatewire with permission from E&E News. E&E provides daily coverage of essential energy and environmental news at www.eenews.net.