Global Warming Cannot be Prevented by Just Cutting CO2, Study Says

A new study has shown that cutting down emissions of carbon dioxide by itself is not sufficient to avoid catastrophic global warming.

However, if society concurrently decreases emissions of methane and other frequently neglected climate pollutants, it is possible to cut the rate of global warming by half by 2050 and give the world a fighting chance.

The study that has been reported recently is the first to evaluate the comparative impacts, through 2050, of cutting emissions of an extensive range of climate pollutants versus targeting just carbon dioxide.

The study has been published in the Proceedings of the National Academy of Sciences journal on May 23^rd, 2022.

Decarbonization is crucial to meeting our long-term climate goals, but it’s not enough. To slow warming in the near-term and reduce suffering from the ever-increasing heatwaves, droughts, superstorms and fires, we need to also reduce short-lived climate pollutants this decade.

Drew Shindell, Study Co-Author and Nicholas Distinguished Professor, Earth Science, Duke University

The new study suggests that concentrating the efforts almost exclusively on cutting carbon dioxide emissions, as the majority of the governments do at present, can no longer stop global temperatures from rising above pre-industrial levels by 1.5 °C.

Such an increase would considerably level the threats of tipping points at which irreversible impacts will take place. Reducing carbon alone might not be sufficient to even avoid temperatures from rising by 2 °C, concludes the study.

Our analysis shows that climate pollutants such as methane, nitrous oxide, black carbon soot, low-level ozone and hydrofluorocarbons contribute almost as much to global warming as longer-lived CO₂. Since most of them last only a short time in the atmosphere, cutting them will slow warming faster than any other mitigation strategy.

Drew Shindell, Study Co-Author and Nicholas Distinguished Professor, Earth Science, Duke University

Furthermore, it would help prevent a short-term warming “backlash” that the Intergovernmental Panel on Climate Change (IPCC) has warned could happen by just cutting fossil fuel emissions.

The IPCC reports collected recently have projected that decarbonizing the energy system and moving to clean energy in isolation could cause temperatures to rise for a while because, besides CO₂, fossil fuel emissions consist of sulfate aerosols. This serves to cool the climate for a short period—from days to weeks—before they tend to disperse.

The new study contributes to this effect and comes to a conclusion that concentrating exclusively on decreasing fossil fuel emissions could lead to a so-called “weak, near-term warming” which could possibly make temperatures surpass the 1.5 °C level by 2035 and the 2 °C thresholds by 2050.

On the other hand, decreasing both CO₂ and other climate pollutants concurrently would considerably enhance our chance of staying below the 1.5 °C mark.

Researchers at Georgetown University, the University of California Santa Barbara, Texas A&M University, and the University of California San Diego carried out the new study with Shindell.

The study was financially supported by the Sequoia Climate Foundation, the Edward Frieman Foundation Chair Funds, and the Clean Air Task Force.

Journal Reference:

Dreyus, G. B., et al. (2022) Mitigating climate disruption in time: A self-consistent approach for avoiding both near-term and long-term global warming. Proceedings of the National Academy of Sciences. doi.org/10.1073/pnas.2123536119.

Source: https://duke.edu/