May 24 2022Reviewed by Alex Smith
Cutting emissions of carbon dioxide, by itself, cannot prevent catastrophic global warming.
However, a new study concludes that a strategy that concurrently decreases emissions of other hugely neglected climate pollutants would reduce the rate of global warming by half and give the world a good chance at keeping the climate a safe place for humanity.
The current study is the first to examine the significance of reducing non-carbon dioxide climate pollutants vis a vis solely decreasing fossil fuel emissions, in both the near-term and mid-term to 2050. The study was published in the journal Proceedings of the National Academy of Sciences.
It ascertains the growing fears that the present almost exclusive focus on carbon dioxide cannot by itself stop global temperatures from surpassing 1.5 °C above pre-industrial levels, the internationally accepted guardrail over which the world’s climate is anticipated to pass irreversible tipping points.
Certainly, such decarbonization alone would be improbable to prevent temperatures from surpassing even the much more dangerous 2 °C limit.
The study, carried out by researchers from Georgetown University, Texas A&M University, Scripps Institution of Oceanography at UC San Diego and others, comes to a conclusion of adopting a so-called “dual strategy” that concurrently decreases emissions of both carbon dioxide and the other climate pollutants.
This would help reduce the rate of warming by half by 2050, thereby making it much more likely to remain within these limits.
The non-carbon dioxide pollutants consist of methane, black carbon soot, hydrofluorocarbon refrigerants, ground-level ozone smog, and also nitrous oxide.
The study assessed that these pollutants at present almost contribute as much to global warming as carbon dioxide. As the majority of them only stay in the atmosphere for a short period of time and cutting them delays warming faster compared to any other mitigation strategy.
So far, however, the significance of these non-carbon dioxide pollutants has been underappreciated by researchers and policymakers in a similar way and hugely neglected in efforts to fight climate change.
Recent reports gathered by the Intergovernmental Panel on Climate Change came to a conclusion that cutting fossil fuel emissions — considered to be the main source of carbon dioxide — by decarbonizing the energy system and shifting to clean energy, in isolation, tends to make global warming worse in a short span of time.
This is because burning fossil fuels releases sulfate aerosols, which serve to cool the climate — and these are reduced along with the carbon dioxide while shifting to clean energy.
Such cooling sulfates fall out of the atmosphere quickly — within days to weeks — while much carbon dioxide remains for hundreds of years. This results in warming for the first 10–20 years.
The new study performed explains this effect and concludes that concentrating solely on decreasing fossil fuel emissions could lead to a so-called “weak, near-term warming”. This could possibly result in temperatures surpassing the 1.5 °C level by 2035 and the 2 °C levels by 2050.
On the other hand, the dual strategy that concurrently decreases the non-carbon dioxide pollutants, particularly the short-lived pollutants, would allow the world to stay well below the 2 °C limits. Also, it considerably enhances the probability of remaining below the 1.5 °C guardrails.
A key insight from the study is the requirement for climate policies to fulfill all of the pollutants that are released from fossil fuel sources like diesel engines and coal power plants instead of taking just methane or carbon dioxide separately into account as is common.
The study stresses that continuing to slash fossil fuel carbon dioxide emissions remains crucial since that will identify the fate of the climate for a long period beyond 2050. Also, phasing out fossil fuels is crucial since they produce air pollution that kills over eight million people annually and results in billions of dollars of damage to crops.
Handling both carbon dioxide and the short-lived pollutants provides the best and the only hope for humanity, thereby making it to 2050 without activating irreversible and possibly catastrophic climate change.
Dreyfus, 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.