"Global warming will hit 1.5C by 2040, warns IPCC report", 9 August 2021

The world is likely to temporarily reach 1.5C of warming within 20 years even in a best-case scenario of deep cuts in greenhouse gas emissions, a landmark report on climate change signed off by 234 scientists from more than 60 countries has concluded.

Even with rapid emissions cuts, temperatures would continue to rise until “at least” 2050, the scientists said, and lead to further extreme weather events.

Without “immediate, rapid and large-scale reductions” in emissions, curbing global warming to either 1.5C or even 2C above pre-industrial levels by 2100 would be “beyond reach”, they said.

[...]

The 1.5C threshold has become a rallying point, as the planet warmed by an estimated 1.2C in 2020 and 1.1C on a ten-year average basis. The G7 group of nations pledged in May to limit warming to 1.5C, in a shift from the 2015 Paris accord headline goal of keeping temperatures at “well below 2C”.

“If the world can substantially reduce emissions in the 2020s and get to net zero carbon emissions by 2050, temperature rise can still be limited to 1.5C,” said Piers Forster, one of the report’s lead authors.

[...]

In the best-case scenario modelled by the scientists — in which more carbon is removed from the atmosphere than is added to it, soon after 2050 — warming is likely to reach 1.5C by 2040 and could rise to 1.6C by 2060. However, temperatures could then cool to 1.4C by 2100.

[...]

For a high 83 per cent chance of limiting warming to 1.5C, the world could only add another 300 gigatonnes of carbon to the atmosphere in total, it estimated. Global energy-related carbon emissions in 2020 were 32 gigatonnes, according to the International Energy Agency.

Even in a 1.5C warmer world there will be an increase in the number of “unprecedented” weather events, the researchers said. Disasters such as floods and heatwaves are expected to become more frequent and intense.

Although warming could still be capped, some changes that have been set in motion are “irreversible” over centuries or millennia, such as sea level rise, said the report.