Scientists warn Switzerland’s worst-case climate scenario is becoming more likely

A 3.25°C world by 2100 is now the central warning from new research. Scientists at ETH Zurich and Leipzig University say current policies could put global warming at around 3.25°C above pre-industrial levels by the end of the century. That projection places Switzerland’s most severe national climate scenario closer to the likely future than officials previously assumed.

The timing matters. Switzerland has just experienced its hottest and driest summer since measurements began in 1864. Long periods of extreme heat affected communities, agriculture and water supplies, while drought spread across large parts of the country. MeteoSwiss and ETH Zurich’s Climate CH2025 report had modelled a 3°C world as the harshest scenario that national projections could describe with confidence.

The new study does not create a hotter version of that scenario. It changes the probability of reaching it. “What happens in a 3°C world isn’t changed by our results,” said Gergana Gyuleva, the study’s lead author. “Our results only change how soon or how likely this 3°C world becomes.” For Swiss planners, that distinction affects decisions on heat protection, water management, farming, infrastructure and public health.

Switzerland could warm by about 4.9°C in a world that reaches 3°C globally. The country heats faster than the global average, making international temperature targets especially consequential for Swiss residents. The projected increase would affect cities, valleys, farms and mountain regions in different ways, while placing additional pressure on ecosystems already responding to warmer conditions.

The 2026 summer offered a practical measure of what those changes can mean. Switzerland recorded its highest national summer temperatures since records began, alongside exceptional dryness. Farmers faced stress in fields and pastures. Households and businesses relied more heavily on cooling. Rivers, soils and reservoirs came under pressure during extended hot periods.

Climate CH2025 presented three reference points: 1.5°C, 2°C and 3°C of global warming. The most severe scenario was designed to help Switzerland prepare for difficult conditions, including more frequent heat extremes and shifts in precipitation. The latest projection reaches beyond that threshold. It gives cantonal authorities a stronger reason to test whether existing building rules, emergency plans, crop strategies and water allocation systems remain adequate during repeated hot and dry summers.

The study raises warming estimates by revising how researchers read the climate record. Conventional projections use historical warming to estimate how the planet responds to rising carbon dioxide concentrations. Gyuleva and her colleagues argue that natural variability made recent warming appear slower than the underlying trend.

The researchers focused on fluctuations such as La Niña, the recurring Pacific cooling pattern. Those episodes reduced observed warming during part of the period used to calibrate forecasts. “We were actually statistically unlucky for having caught a period where variability produced less warming in the real world,” Gyuleva said.

The team also used satellite observations of Earth’s energy balance. Since 2000, the difference between incoming sunlight absorbed by the planet and heat released back into space has more than doubled. That widening gap indicates that the climate system is retaining heat faster than some earlier assessments suggested.

The result raises the lower end of projected warming. Futures with relatively limited warming appear less compatible with the satellite evidence. The researchers tested the result using only outgoing heat data, which climate models simulate more reliably than incoming sunlight affected by clouds and ice. They obtained the same outcome, although the study acknowledges that the satellite record covers only 25 years, limiting certainty about longer term trends.

Forty two percent of surveyed IPCC authors expected at least 3°C of warming by 2100. The figure comes from a 2024 survey of 211 IPCC authors, and it shows how a 3°C future has moved into mainstream scientific expectations for many experts.

The ETH Zurich and Leipzig University study reaches its projection through a different method. It combines climate modelling with observations of the planet’s energy imbalance, then accounts for natural variations that can temporarily slow or accelerate measured warming. The authors say their findings apply to emission pathways without immediate and drastic cuts.

Gyuleva estimates that warming under those pathways could be 25% higher than conventional estimates suggest. She also identifies the satellite component as the weakest part of the research. The observational record is short, and models perform less consistently when estimating sunlight absorbed by clouds and ice. The study’s repeat analysis using outgoing heat alone produced the same result, adding support while leaving uncertainty in place.

That uncertainty does not remove the planning signal. Switzerland’s climate policy, infrastructure standards and adaptation measures must operate over decades. Decisions on railways, hydropower, agriculture, housing and healthcare cannot rely only on the most comfortable end of the forecast range.

Swiss authorities are being asked to plan for conditions once labelled extreme. A 3°C global warming pathway would influence every level of public decision making, from federal climate policy to cantonal heat plans and municipal building permits. The practical issues are immediate: how cities protect older people during heatwaves, how farms secure water, how rail lines withstand heat and how electricity systems respond to changing demand.

Adaptation cannot replace emissions cuts. The study’s projection concerns current policies, and Gyuleva links the higher warming estimate to pathways without rapid reductions. The findings therefore reinforce the value of reducing emissions while expanding measures that protect people from unavoidable impacts.

Swiss residents have already seen signals of the pressure. The country’s hottest and driest summer on record exposed vulnerabilities in agriculture, water management and public health. A warmer baseline can make similar episodes more frequent or more intense, while reducing the recovery time between them.

The next stage for Switzerland is evidence based preparation. Federal agencies, cantons, cities, farmers, utilities and hospitals need to compare their plans with the 3°C scenario used in Climate CH2025. The latest research suggests that scenario should be treated as a serious planning reference, not a distant edge case.