Even if we stopped emitting greenhouse gas today, the Earth would continue warming for centuries. Arctic ice and permafrost are already on an irreversible path of melting.
That's the finding of new research published Thursday in the journal Scientific Reports. The model suggests that even if emissions were to drop to zero this year, global temperatures would ultimately rise to be 5.4 degrees Fahrenheit higher in 2500 than they were in 1850 (that's 3 degrees Celsius).
"The tundra will continue to melt over the next 500 years — irrespective of how quickly humanity cuts its greenhouse-gas emissions," Jørgen Randers, the lead author of the new study, told Business Insider.
That's because climate change is a vicious, self-sustaining cycle: As permafrost thaws, it releases more greenhouse gases, like methane and carbon dioxide, which sustains warming over time. To stop that cycle, Randers said, we'll need to suck carbon dioxide back out of the atmosphere.
8 feet of sea-level rise
Randers' study modeled the effect of various emissions-reductions scenarios on Earth's climate between 1850 and 2500.
The data showed that if emissions stopped for good in 2020, sea levels in 2500 would still be more than 8 feet (2.5 meters) higher than in 1850.
To prevent the projected 3-degree-Celsius temperature increase, greenhouse-gas emissions would need to have ceased entirely between 1960 and 1970, the model found. In that sense, Earth blew by a climactic point of no return 50 years ago — before much of the public understood the realities of climate change.
"Yes, that is an irony," Randers said. "But of course the scientific community knew about global warming already in the 1960s."
We need to suck carbon out of the atmosphere
The Paris climate agreement was created with the intention to cut greenhouse-gas emissions enough to keep the world's temperature from rising more than 2 degrees Celsius by 2100. But even if all emissions stopped by 2100, according to Randers' model, sea levels in 2500 would be nearly 10 feet (3 meters) higher than they were in 1850.
Earth's temperatures are already on track to blow past the Paris agreement's goals. Last year was the second warmest on record for surface temperatures and the hottest ever for oceans. Polar melting is on track to raise seas 3 feet by 2100 and threatens to displace hundreds of millions of people.
What's needed, Randers said, is for companies and governments to "start developing the technologies for large-scale removal of greenhouse gases from the atmosphere."
In technical terms, that strategy is known as carbon capture and storage (CCS). To prevent further warming after emissions have stopped, the new study found, at least 33 gigatonnes (36.5 billion tons) of carbon dioxide would need to be sucked out of the atmosphere each year. That's roughly the total amount of carbon dioxide the global fossil-fuel industry emitted in 2018 (36 gigatonnes).
Power plants in the US, Canada, and Switzerland have already started utilizing CCS to lower their emissions. In 2014, the Boundary Dam Power Station in Saskatchewan became one of the first in the world to successfully use the technology.
In total, 21 commercial-scale carbon-capture projects are operating around the world, and 22 more are in development, according to the Center for Climate and Energy Solutions. These projects typically store carbon deep underground in depleted oil and gas fields or in bioreactor containers filled with algae that eats carbon dioxide.
Two US carbon-capture completed in 2017 — one in Illinois, one in Texas— can capture 1.1 million and 1.6 million tons of carbon dioxide, respectively, per year. But the amount of CO2 that needs to be removed from the atmosphere requires far more plants than any current plans call for.
"In other words, building 33,000 big CCS plants and keep them running for ever," the study authors wrote.
The pros and cons of geoengineering
Carbon capture is becoming widely accepted as a safe and potentially effective form of geoengineering. This and other climate interventions are increasingly being floated by scientists and politicians alike; Andrew Yang, a 2020 Democratic presidential candidate, suggested budgeting $800 million for further geoengineering research in the US.
But most climate-hacking proposals would be far riskier than CCS. Take solar geoengineering, for example, which involves injecting aerosols into the sky to reflect sunlight back into space. Critics of this idea point out that most models predict the effects of solar geoengineering wouldn't stay localized. If a country decided to independently deploy such measures, varying and unpredictable effects would likely be seen in other spots around the globe.
Aerosol injections deployed in the southern hemisphere, for instance, could impact ocean temperatures and wind speeds, leading to more hurricanes in the northern hemisphere.
"Solar geoengineering has geopolitical ramifications, unlike carbon capture," Juan Moreno-Cruz, an associate professor at the University of Waterloo who studies geoengineering, previously told Business Insider.
Randers said his study advocates just for carbon capture, not other more experimental forms of geoengineering.
"I am generally against geoengineering because of its unintended side effects. But if the world continues to delay meaningful and feasible action to phase out fossil fuels, we may have to resort to geoengineering," Randers said.
As an immediate priority, he added, countries should invest equally in efforts to cut emissions and build more CCS plants.
"This would be a wonderful task for a government-financed Green New Deal," he said.
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