The prognosis sounded frightening. A total of 372 out of 400 German regions will suffer from heat stress, some of which will be massive, in 2050, warned a joint study the Institute of German Economy (IW) and the Cologne insurance company of Ergo Versicherung in December. For comparison: today, in 2026, there are still zero.

What’s more: the risk of devastating floods, for example on the North Sea coast, as well as severe storms will also increase sharply, the study found. “The analysis shows that all regions of Germany are severely affected by the effects of climate change in a scenario of continued high greenhouse gas emissions,” said a statement accompanying the study.

The authors of the study transparently point out the answer themselves. The so-called SSP5-8.5 model was used for the calculations, it says in several places in the analysis. And it is precisely this model, which is also used in hundreds of other climate studies, that scientists are increasingly having a problem with.

Cars that run on coal

To explain: In order to adequately forecast the future, climate researchers use a series of so-called scenarios that make various assumptions about factors such as economic development, population growth and technical progress. These scenarios vary in their optimism – and SSP5-8.5 is the most pessimistic scenario of all.

Because at 8.5 everything comes together:

• There the population and prosperity are increasing sharply,
• Energy consumption is increasing even further than it already is.
• At the same time, however, the energy transition is failing – and humanity is almost entirely satisfying its enormous energy hunger with coal, oil and gas.

The even more pessimistic previous model, RCP 8.5, even assumed that cars would run on coal in the future because global oil reserves were running out. Global warming of five degrees Celsius or more compared to pre-industrial times would be possible under this scenario.

There are already a few successes

However, this worst-case scenario has little to do with reality. Solar and wind energy are rapidly displacing fossil fuel competition from the electricity system. According to the energy organization Irena, 93 percent of the energy sources added worldwide in 2024 were of a renewable nature. Heat pumps are replacing gas heaters, electric cars are replacing combustion engines – although not as quickly as expected, but the change is unmistakable.

The result: According to estimates by the Intergovernmental Panel on Climate Change (IPCC), the world is currently heading towards warming of 2.6 to 2.7 degrees by 2100. Still too much, the researchers warn – the result would be millions of deaths from heat, disease and nutritional deficiencies. But 2.7 degrees of warming is much better than five degrees. Humanity has already achieved a few successes in the fight against climate change.

The decade-long mistake

But why do many climate studies exaggerate by using a now unrealistic scenario as a reference? Isn’t it enough to point out the actual, realistic consequences, which are still huge? “The climate science community has been wrong for a decade,” US climate scientist Zeke Hausfather said in December in a podcast from the British BBC. “And that mistake was that they confused the worst possible scenario with the most likely outcome.”

Hausfather is one of the lead authors of the upcoming Intergovernmental Panel on Climate Change report and is considered one of the best-known climate scientists in the world. The waves he and his colleague Glen Peters made in 2020 were correspondingly big with a short essay in the renowned scientific journal PNAS had beaten. There the two argued that the 8.5 scenario was unrealistic and should no longer be used. More optimistic scenarios fit reality much better.

“This information somehow got lost”

Climate modelers have always transparently pointed out that SSP5-8.5 is an absolute worst-case scenario, says Hausfather. “But this information somehow got lost in the communication between modelers and the larger climate science community.” SSP5-8.5 and its predecessor RCP 8.5 have increasingly been used as a “business as usual” scenario, intended to describe a world in which humanity continues as before. “But it was never designed for that.”

In a sense, climate science has been overtaken by reality here, says Hausfather, fortunately for humanity. The 8.5 scenario was designed between 2008 and 2010 – when no one had any idea of ​​the triumph of renewable energies.

“Today it seems stupid, of course, with solar being the cheapest form of energy production in the world,” says Hausfather. “But this is a relatively new phenomenon. Even green energy advocates didn’t think 15 years ago that things would get so cheap so quickly.”

When the horror scenario was realistic

The climate researcher explains that the 8.5 scenario was still realistic until around 2015. In some cases, emissions even rose faster than in the model. “Global emissions rose by a third between 2000 and 2010. China was building two coal-fired power plants per day. The idea that the 21st century could be dominated by coal did not seem unrealistic at the time.”

Some climate researchers also point out that the 8.5 scenario could be more realistic in a few decades than we would like. Many consequences of climate change on Earth systems such as the polar ice caps, the rainforests or the oceans are still unexplored – possible feedbacks between these systems could trigger warming that is more rapid than modeled.

But even so, explains Hausfather, the discrepancy between the models and reality will soon resolve itself. The 8.5 scenario is being used less and less, the research just needs to be given some time. “The natural wave in which research advances is a pretty chaotic process,” says Hausfather. “It’s often slower than we would like. But it always corrects itself.”