The vast majority of planet-warming emissions come from just 178 oil, gas, and cement companies known as the “carbon majors.” Even if these companies stopped emitting tomorrow, the carbon they’ve already spewed into the atmosphere will continue heating the planet for centuries to come.
That’s according to a study published today in the journal PLOS Climate. As Earth’s average temperature careens toward 2.7 degrees Fahrenheit (1.5 degrees Celsius) of warming above pre-industrial levels, the findings underscore the urgent need to cut emissions from the carbon majors as quickly as possible.
A whopping 50% of these emissions were produced after 1986, when the relationship between greenhouse gases and global warming was already well established. That is “unbelievable,” lead author Dargan Frierson, an associate professor of atmospheric and climate science at the University of Washington, told Gizmodo.
“That, to me, just shows that we didn’t have to go down this route,” Frierson said.
Carbon majors cast a long shadow
Unlike many other gases, carbon dioxide doesn’t simply break down once it enters the atmosphere. CO2 molecules tend to linger until they are absorbed by the ocean, plants, or soil. This explains why fossil fuel emissions are rapidly accumulating in the atmosphere; humans are releasing CO2 much faster than Earth’s natural systems can absorb it.
Numerous studies have estimated how much warming could result from future emissions scenarios, but it’s also important to consider the lasting warming effect of past emissions. To that end, Frierson and his colleagues modeled the global climate through 2500 under various emissions scenarios, then ran simulations with and without emissions from the carbon majors through 2024.
That data came from the Carbon Majors database, which tracks emissions from all 178 companies—including oil and gas giants such as Shell, ExxonMobil, and Chevron—dating back to 1854. Since then, the carbon majors have emitted more than 1.5 trillion tons of carbon dioxide equivalent.
The results showed that their past emissions will continue to raise global temperatures and exacerbate extreme weather well into the future. In scenarios with lower future emissions, carbon majors account for a larger share of total global warming. In higher-emissions scenarios, future emissions account for a much larger share of warming than past emissions from carbon majors. However, the total amount of warming attributable to those companies’ past emissions remains about the same.
The researchers therefore conclude that, in addition to the climate damages those emissions have already caused, they may be responsible for calculable damages “many centuries into the future.”
The path to a stable climate is clear
To stabilize Earth’s temperature, humanity’s emissions need to fall to near zero, but stabilization won’t happen as soon as we hit that target. Studies suggest it could take decades to reverse the current warming trend and centuries for global temperatures to return to pre-industrial levels.
The higher Earth’s temperature rises, the longer this reversal will take. That’s why it’s essential that humanity reduces its emissions as quickly as possible, and the carbon majors are the best place to start.
“I don’t think a lot of people realize that we essentially have to stop burning fossil fuels in order to get the warming to stop,” Frierson said. “We really have to take [emissions] very close to zero, and we’re very far from that right now. Emissions have been setting records, they’re not going on a downward track.”
With that in mind, Frierson stresses the importance of policies designed to protect people from climate impacts we won’t be able to avoid, even if the world begins to make better progress toward phasing out fossil fuels.
