Slashing emissions of carbon dioxide emissions alone will not be enough to prevent global temperatures reaching an “irreversible tipping point”, new research has this week warned.
In contrast, a “dual strategy” that simultaneously reduces emissions carbon dioxide and other climate pollutants such as methane could cut the rate of warming in half by 2050, making it much more likely temperature rises could be limited to below 1.5C, scientists believe.
A new study published in the latest issue of Proceedings of the National Academy of Sciences This week by scientists at Georgetown University, Texas A&M University, Scripps Institution of Oceanography at University of California (UC) San Diego, and others is the first to analyze the importance of cutting greenhouse gases other than carbon dioxide in both the near-term and mid-term through to 2050.
“The Intergovernmental Panel on Climate Change (IPCC) says we must make deep cuts to GHG immediately,” said Gabrielle Dreyfus, chief scientist at the Institute for Governance & Sustainable Development (IGSD) and professor at Georgetown University. “Our study shows that phasing out fossil fuels is essential but must be paired with targeted action now on methane, black carbon soot, HFCs, and smog. This dual strategy is the only way to slow warming over the next two decades and give ourselves a fighting chance for a livable climate.”
Methane is known to be more than 25 times as potent as carbon dioxide at trapping heat in the atmosphere and as such campaigners and scientists have long argued there should be more focus on tackling emissions from agriculture and the fossil fuel industry.
Recent IPCC reports conclude that cutting fossil fuel emissions – the main source of carbon dioxide – by decarbonising the energy system and shifting to clean energy, in isolation, would make global warming worse in the short term due to a related reduction in the release of sulphate aerosols, which act to cool the climate. These cooling sulphates fall out of the atmosphere fast – within days to weeks, while much of carbon dioxide lasts hundreds of years, thus leading to overall warming in the coming decades.
The new study accounts for this effect and concludes that focusing exclusively on reducing fossil fuel emissions could result in “weak, near-term warming” that could cause temperatures to exceed 1.5C by 2035 and 2C by 2050.
Until now, the importance of non-carbon dioxide pollutants has been underappreciated by scientists and policymakers alike and largely neglected in efforts to combat climate change, the authors note.
“Methane is a blow torch that’s cooking the planet today,” said Durwood Zaelke, president of the Institute for Governance & Sustainable Development (IGSD), and adjunct professor at Bren School of Environmental Science & Management, part of the UC Santa Barbara. “If we stop methane leaks, we shut off the blow torch and avoid more warming in the next couple of decades than any other strategy – nearly 0.3C – which can slow the rate of warming almost immediately.”
There has been growing momentum behind initiatives designed to tackle methane emissions over the past six months. More than 110 countries aroud the world have now signed the Global Methane Pledge, which was launched at the COP26 Climate Summit last autumn and calls for a 30 per cent reduction in worldwide emissions of methane by 2030, relative to 2020 levels. However, critics have noted the pledge falls short of the 45 per cent reduction the UN estimates is needed to limit global heating to 1.5C, and have warned that signatory governments are yet set out comprehensive plans to cut emissions across all the three key sectors that drive methane emissions: agriculture, energy, and waste.
And in March, the world’s leading oil and gas companies pledged to bring their methane emissions to “near zero” by 2030, as part of a new cross-industry initiative targeted rapidly reducing emissions of the potent greenhouse gas.