Global temperatures could rise 3.25C by 2100: study

Researchers at ETH Zurich and Leipzig University warned on Tuesday that global temperatures could rise by around 3.25C (5.85F) by the end of the century under current policies, suggesting previous projections may have underestimated future warming.

Revised warming estimates

The study indicates that warming could be 25 percent higher than previously expected for any emission trajectory lacking immediate and drastic cuts, according to Swissinfo. "For any emission trajectory without immediate and drastic emission cuts, we expect warming to be 25% higher," said Gergana Gyuleva, a doctoral researcher at ETH Zurich and the paper's lead author. The researchers revised their projections by incorporating natural climate variability and satellite measurements of Earth's energy imbalance — the difference between incoming solar energy and heat radiated back into space.

"What happens in a 3C (5.4F) world isn't changed by our results. Our results only change how soon or how likely this 3C world becomes," Gyuleva said. The findings suggest that the remaining global carbon budget is approximately one-fifth smaller than earlier models indicated, leaving less room for emissions than previously calculated.

Accelerated risk for Switzerland

The projections carry particular implications for Switzerland, where temperatures are increasing faster than the global average. A planet that is 3C warmer than pre-industrial levels would translate into roughly 4.9C (8.82F) of warming within Swiss borders, according to the research.

The country's hottest summer on record offered a preview of such conditions. Basel recorded 58 days above 30C (86.5F) during the recent season, compared with 41 days in 2003, while Bern experienced 46 days versus 29 in 2003 and Zurich saw 38 days compared with 27. The scenarios published by MeteoSwiss and ETH Zurich last November project approximately 30 days with temperatures exceeding 30C for the Zurich area in a typical summer under a 3C warming scenario.

Narrowing carbon budget

Researchers stressed that the higher warming scenario is not inevitable, noting that severe emissions reductions could limit future warming. "Our results point to the need for faster mitigation for a given temperature target," Gyuleva said. The findings were published as Switzerland recorded its hottest summer on record, with Basel registering 58 days above 30C compared to 41 days during the 2003 heatwave.