Non-CO2 emissions cuts crucial to keep below 2°C warming

Researchers from Duke University in the USA said that by focusing on reducing emissions of other atmospheric gases, as well as CO2, the rate of global warming could be cut in half by 2050.

“Decarbonisation is crucial to meeting our long-term climate goals, but it’s not enough,” said study co-author Drew Shindell.

“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.”

The research shows that focusing efforts almost entirely on cutting CO2 emissions, as most governments currently do, can no longer prevent global temperatures from rising 1.5°C above pre-industrial times – a key aim of the Paris climate accord.

Such a rise would substantially increase the risks of tipping points at which irreversible impacts will occur. Cutting carbon alone may not be enough to prevent temperatures from rising by 2°C, the study concludes. 

“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,” Shindell said. “Since most of them last only a short time in the atmosphere, cutting them will slow warming faster than any other mitigation strategy.”

It would also help us avoid a short-term warming “backlash” that the Intergovernmental Panel on Climate Change (IPCC) has warned could occur by cutting fossil fuel emissions alone.

Recent IPCC reports have predicted 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 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°C level by 2035 and the 2°C threshold by 2050.

In contrast, reducing both CO2 and other climate pollutants simultaneously would significantly improve our chance of remaining below the 1.5°C mark.

A report from the World Meteorological Organisation last week found that the world’s oceans are at their most acidic level for at least 26,000 years as oceans absorb increasing amounts of carbon dioxide from the atmosphere.