Climate action on CO2 emissions alone won’t prevent extreme warming

Decades of global climate discussions have focused on CO2 emissions, which are most abundant in the atmosphere. The common goal of reaching "net-zero" emissions refers most often to CO2 emissions alone.

Over the last year, more than 100 countries have pledged a 30 per cent cut by 2030 to emissions from methane, another carbon-based greenhouse gas that is far more powerful at trapping heat than CO2. Most of those countries have yet to say how they will meet that deadline.

Meanwhile, scant attention has been paid to other warming pollutants, including black carbon, also called soot, which absorbs radiative heat, as well as hydrofluorocarbons found in refrigerants, and nitrous oxides. But together with methane, these pollutants are responsible for about half of the warming seen today, according to the study published on Monday (May 23) in the journal Proceedings of the National Academy of Sciences.

"When we're worried about the near-term … we need to look at the other non-CO2 climate forcers," said study co-author Durwood Zaelke, president of the Institute for Governance & Sustainable Development in Washington DC.

This is especially important as countries pursue CO2 reductions through cutting back on their use of fossil fuels, still considered the main contributor to global warming. Using fewer fossil fuels will result in less air pollution, including airborne sulphates that actually counteract some climate change by reflecting solar radiation away from Earth.

Scientists say these sulphates are masking about 0.5 degree Celsius of warming that would be seen without them, meaning aggressive climate action could see temperatures temporarily jump higher - unless the lesser pollutants are tackled as well.

A path of decarbonisation alone would see the planet breach 2 degrees Celsius of warming beyond pre-industrial temperatures by 2045, the study finds.

Conversely, reining in all climate pollutants together could see the world begin to avoid some warming as early as 2030 and halve the rate of warming between 2030 and 2050, the findings suggest.

"This landmark paper should bring about a major rethink" of global targets, said Euan Nisbet, a climate scientist at Royal Holloway, University of London, not involved in the study. "If we don't also bring down non-CO2 warming, we cook."

World’s oceans at most acidic level in 26,000 years

The world's oceans grew to their warmest and most acidic levels on record last year, the World Meteorological Organization (WMO) said on Wednesday (May 18), as United Nations officials warned that war in Ukraine threatened global climate commitments.

Oceans saw the most striking extremes as the WMO detailed a range of turmoil wrought by climate change in its annual "State of the Global Climate" report. It said melting ice sheets had helped push sea levels to new heights in 2021.

"Our climate is changing before our eyes. The heat trapped by human-induced greenhouse gases will warm the planet for many generations to come," said WMO Secretary-General Petteri Taalas in a statement.

The report follows the latest UN climate assessment, which warned that humanity must drastically cut its greenhouse gas emissions or face increasingly catastrophic changes to the world's climate.

Taalas told reporters there was scant airtime for climate challenges as other crises, such as the COVID-19 pandemic and war in Ukraine, grabbed headlines.

Selwin Hart, UN Secretary-General Antonio Guterres's special adviser on climate action, criticised countries reneging on climate commitments due to the conflict, which has pushed up energy prices and prompted European nations to seek to replace Russia as an energy supplier.