Summer of 2023 was the hottest in 2,000 YEARS - and scientists say climate change is to blame
The summer of 2023 was the hottest for 2,000 years in the northern hemisphere, according to new analysis. Humanity has not known hotter weather since the early days of the Roman Empire and the birth of Jesus Christ, the latest study shows. Overall, last summer was 2.2C hotter on land than the average temperatures for the years between 1AD and 1890AD, when the industrial revolution was in full swing, pumping huge amounts of climate warming greenhouse gas into the atmosphere. It was also almost 4C hotter than the coldest summer in 536AD when an ash cloud from a volcanic eruption is thought to have caused temperatures to plunge. 'When you look at the long sweep of history, you can see just how dramatic recent is,' said co-author Professor Ulf Buntgen, from Cambridge's Department of Geography. While the temperatures are an average for Earth's northern hemisphere, summer in the UK last year was considered average by the Met Office and only the eighth warmest on record. The years 2022 and 2018 were the joint warmest UK summers. Reliable weather records produced by scientific instruments only date back to 1850 when the industrial revolution was getting under way. But by analysing tree rings, scientists were able to calculate how hot summers have been by the growth of the tree ring and chemical composition of the wood. Trees have narrower growth periods creating narrower rings - during cold periods and wider rings during hot periods. The authors write that even allowing for natural climate variations of around 0.5C, 2023 was still the hottest summer since the height of the Roman Empire. The heat was the result of a combination of record levels of greenhouse gases and the El Nino weather event, Professor Buntgen said. '2023 was an exceptionally hot year, and this trend will continue unless we reduce greenhouse gas emissions dramatically,' he said. But the results, reported in the journal Nature, also show that the attempts to limit the 2015 Paris Agreement to limit warming to 1.5C above pre-industrial levels may already have been exceeded. The researchers calculate the 19th century temperature baseline used as the benchmark to measure global warming could be as much as several tenths of a degree Celsius colder than previously thought. On that basis, the researchers calculated that summer 2023 conditions in the Northern Hemisphere were 2.07C warmer than average summer temperatures between 1850 and 1900, as opposed to the current accepted view that global warming is running at 1.4C higher than the 19th century baseline. The researchers say that while their results are valid for the Northern Hemisphere, excluding the tropics, it is difficult to obtain global averages for the same period since data is sparse for the Southern Hemisphere. The Southern Hemisphere also responds differently to climate change, since it is far more covered by sea than the Northern Hemisphere.