Forecast is slightly cooler than the record 1.55C reached in 2024, but 2026 set to be among four hottest years since 1850

Levels of carbon dioxide clogging the atmosphere soared to unprecedented levels last year, a UN report found in October. As well as the unrelenting burning of fossil fuels and the fallout from rampant wildfires, scientists fear the Earth’s natural “carbon sinks” may be beginning to fail.