2023: The year that broke climate science
The Observatory
25 Jul 2025
Written By Dr David Whitehouse
The past two years have been quite abnormally warm – a lot warmer than scientists expected. They had thought that 2023 would be a warm year, though not a record breaker. What happened in 2023 to make it the warmest year by a huge margin lies far outside the expectations of the models and forecasts. The only other year that climate models erred so spectacularly was 1992, which was understandable as Mount Pinatubo erupted and put a huge amount of sulphur dioxide in the stratosphere, cooling the planet. Scientists cannot explain 2023, and to compound matters 2024 was even warmer – the first year above 1.5 degrees globally.
They have identified many possible effects. One is that El Niño is behaving abnormally, citing as evidence that we've been in an unusually extended La Niña period since the end of 2020, with a triple-dip La Niña between 2020 and the start of 2023. Because we had such a long La Niña perhaps a more extreme heat outpouring occurred in 2023?
That’s not all. There has been a big change in the sulphur content of shipping fuels following a 2020 decision by the International Maritime Organization mandating an 80% reduction, thereby decreasing its sunlight-reflecting effect. Several studies find it resulted in a moderate reduction of only about 0.05°C. Then there is the 2022 eruption of the Hunga Tonga volcano, which was unusual because it occurred underwater and deposited a lot of water vapour in the upper atmosphere in addition to sulphur dioxide. Water vapour warms the planet, but sulphur has the opposite effect, and scientists don’t know how they balance out, but think it’s about 0.02°C – another small effect.
https://www.netzerowatch.com/all-news/2023-the-year-that-broke-climate-science
