Slashing CO2 alone 'won't be enough to avert catastrophic climate change'

Slashing carbon dioxide emissions alone won’t be enough to avert catastrophic climate change, warns a new report..

Rising emissions of less well known toxic pollutants must also be tackled if global temperatures are to remain at safe levels, say scientists.

The pollutants include methane, hydrofluorocarbon refrigerants, black carbon soot, ground-level ozone smog and nitrous oxide.

Researchers believe quickly cutting carbon emissions alone will not hold global temperatures at 1.5 degrees above pre-industrial levels, a threshold which is deemed safe for humanity.

If temperatures rise above that level, hazardous and irreversible “tipping points” could be crossed, causing huge damage to the environment.

In fact, cutting carbon dioxide emissions alone is unlikely to stop global temperatures rising higher than two degrees above pre-industrial levels.

The study found other gases contribute almost as much to global warming as carbon dioxide.

Most of them last only a short time in the atmosphere, which means cutting them slows warming faster than any other mitigation strategy.

Until now, the importance of these non-carbon dioxide pollutants has been underappreciated by scientists and policymakers alike and largely neglected in efforts to combat climate change.

Recent reports by the Intergovernmental Panel on Climate Change say cutting fossil fuel emissions-the main source of carbon dioxide-by decarbonising the energy system and shifting to clean energy, in isolation, makes global warming worse in the short term.

This is because burning fossil fuels also emit sulphate aerosols, which act to cool the climate – and these are reduced along with the carbon dioxide when switching to clean energy.

These cooling sulphates fall out of the atmosphere within days to weeks, which leads to overall warming for the first decade or two.

The new study, published in the journal Proceedings of the National Academy of Sciences (PNAS), states that focusing exclusively on reducing fossil fuel emissions could result in ‘weak, near term warming’ which could cause temperatures to exceed the 1.5 degrees threshold by 2035 and the two degrees threshold by 2050.

In contrast, a strategy to slash emissions of both carbon dioxide and other pollutants would help the world limit temperatures to ‘well below’ two degrees above pre-industrial levels and would boost our chances of staying below 1.5 degrees of warming.

The researchers say their plan to tackle both types of pollutant offers humanity ‘the only hope’ of making it to 2050 without triggering irreversible and catastrophic climate change.

Slashing carbon dioxide emissions remains vital because it will determine the planet’s future beyond 2050 and because fossil fuels kill more than eight million people through air pollution and damage crops, the researchers add.

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