Just Stopping Emissions May No Longer Be Enough to Stop Global Warming
Researchers argue that it’s time to invest in aggressive carbon capture
Earlier this year, the Earth saw a huge dip in carbon emissions as nations around the globe locked down to slow the spread of the coronavirus. It offered a glimpse into what the world might look like if we took drastic steps to reduce our carbon emissions to slow the spread of global warming: For a brief moment, smog-choked cities around the world had clear skies.
But according to a new modeling study published in Scientific Reports today, even if we made such drastic reductions permanent, it would still not be enough. The study suggests that if we stopped all human-made greenhouse gas emissions immediately, the Earth’s temperatures would continue to rise because of self-sustaining melting ice and permafrost. These “feedback loops” — in which melting ice causes less sunlight to be reflected back into space, which in turn raises temperatures and causes more ice melt — have already been set into motion, the researchers argue.
Humanity “is beyond the point-of-no-return when it comes to halt the melting of the permafrost using greenhouse gas cuts as the single tool,” Jørgen Randers, PhD, professor emeritus of climate strategy at BI Norwegian Business School and lead author of the study, tells Future Human in an email. That’s not to say we should give up on reducing emissions: Rather, Randers says that the world "should accelerate its effort to cut greenhouse gas emissions (in order to postpone as much as possible the temperature rise) and start developing the technologies for large scale removal of greenhouse gases from the atmosphere.”
For decades, climate scientists have tried to predict the so-called tipping point at which it would be too late to stop global warming — too late to limit the amount the temperature rises, the amount of sea level rise, and the number of lives claimed by both and other climate-induced ecological disasters — through reducing carbon emissions alone. Climate scientists point to either 2030 or 2050 as deadlines for the world to get to zero emissions before runaway climate change kicks in. But according to the new study, no matter how much we reduce emissions now, warming will continue, and the self-sustained melting of Arctic ice and permafrost that has already begun could continue for 500 years.
“It simply will not stop from cutting manmade greenhouse gasses,” says Randers. “We need to do something more in order to stop it.” He and co-author Ulrich Goluke, an associate professor at Business School Lausanne in Switzerland, make the case that it’s time to pursue more aggressive climate strategies, like carbon sequestration.
They used a reduced-complexity model the impact of greenhouse gas emission reductions on the global climate from 1850 to 2500, using data from a variety of sources, including NASA and the National Oceanic and Atmospheric Administration (NOAA). They found that even if we stop all greenhouse gas emissions this year, the Earth would still be 3 degrees Celsius warmer and the sea level would be 2.5 meters higher in 2500 than it was in 1850. And if we take even longer to take action — allowing our greenhouse gas emissions to peak during the 2030s and reach zero by 2100 — the Earth will be 3 degrees Celsius warmer and the sea level three meters higher in 2500.
“It simply will not stop from cutting manmade greenhouse gases. We need to do something more in order to stop it.”
Recent research on global temperature rise due to climate change predicts that Earth’s temperature will rise between 2.6 and 3.9 degrees Celsius over the next few hundred years. NOAA scientists projected in 2017 that the sea level will rise between 12 inches and 8.2 feet by 2100.
To stop this projected rise, we would have had to reduce our emissions to zero between 1960 and 1970, according to the model.
Randers says it’s urgent that larger organizations, like NASA and NOAA, check that their climate models address the self-sustained melting he and Goluke saw in their model. “Their models are much bigger than ours, and may reveal counteracting forces that can stop the melting we observe,” he says.
Self-sustained melting is caused by three things, according Randers and Goluke. First, there’s the ongoing melting of Arctic ice, which decreases the area of ice that can reflect the sun’s light and heat back to space. As a result, the remaining ice and permafrost absorb more heat. Second, higher temperatures increase the amount of water vapor in the atmosphere, which in turn increases the humidity and temperature. And third, changes in greenhouse gases driven by emissions from permafrost melting and absorption of carbon in biomass and oceans also contribute to increasing temperatures and lead to melting.
To stop self-sustained melting — and the expected rise in temperature and sea level after emissions cease — Randers says the world must undertake a massive effort to capture carbon out of the atmosphere and store it back underground, a technology known as carbon sequestration. And we would have to start sucking at least 33 gigatons out of the air every year, starting this year. For comparison, all animal life on Earth collectively weighs an estimated two gigatons.
There are already lots of carbon capture and storage projects of varying sizes underway all over the world — startups like Global Thermostat and CO2 Solutions and multinational corporations like Shell and Chevron have launched such projects. But none of them attempts to tackle carbon capture on the scale that Randers recommends. He says we will need tens of thousands of huge plants to capture and store the carbon for at least 100 years.
“It is a very big job,” Randers says, “but it’s equivalent to the work involved in putting all the manmade CO2 into the atmosphere, which has taken us 100–200 years of industrial activity. Getting it out again will be the same type of effort.”
Update: This story has been updated to include additional context from Randers.