Curbing CO2 alone not enough to prevent global warming: Study

Focusing efforts almost exclusively on cutting carbon dioxide (CO2) emissions, as most governments currently are doing, can no longer prevent global temperatures from rising above the UN-mandated pre-industrial levels of 1.5 degree Celsius, warns a new study.

But if we simultaneously also reduce emissions of methane and other often overlooked climate pollutants, we could cut the rate of global warming in half by 2050 and give the world a fighting chance, revealed the study, appearing in the Proceedings of the National Academy of Sciences.

Cutting carbon alone may not be enough to prevent temperatures from rising by 2 degree Celsius. To slow down warming in the near-term and reduce suffering from the ever-increasing heatwaves, droughts, superstorms and fires, short-lived climate pollutants also must be reduced.

"Decarbonisation is crucial to meeting our long-term climate goals, but it's not enough," said Drew Shindell, Professor of Earth Science at Duke University.

"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," Shindell said.

Recent Intergovernmental Panel on Climate Change (IPCC) reports have projected that decarbonising the energy system and shifting to clean energy in isolation could perversely cause temperatures to rise for a while because, in addition to CO2, fossil fuel emissions contain sulphate aerosols, which act to cool the climate for a very short time -- from days to weeks -- before they dissipate.

The new study accounts for this effect and concludes that focusing exclusively on reducing fossil fuel emissions could result in "weak, near-term warming", which could potentially cause temperatures to exceed the 1.5 degrees Celsius level by 2035 and the 2 degrees Celsius threshold by 2050.

In contrast, reducing both CO2 and other climate pollutants simultaneously would significantly improve our chance of remaining below the 1.5 degree Celsius mark, the researchers said.