The summer of 2021 went down in history as a rainy summer; record high water and flooding was widespread. The opposite scenario presented itself to us a year later, when one heat record followed another and many rivers literally dried up.
Extremes such as those that have followed each other in the past two years are becoming more common due to climate change. They also make us wonder even more what awaits us leading up to the summer or winter season. That is also why we dare to take a look at the trends of the most important research and weather institutes and what they can mean for the summer in Switzerland, but also in Europe and worldwide.
Weather forecasts are only really accurate for the next few days. Yet there are models that try to make forecasts over months. They are based less on current weather conditions than on major climate changes.
Such long-term weather forecasts are getting better and better, for example, they predicted last year’s hot summer quite accurately. However, their inaccuracy and the many uncertainties associated with such long time intervals should not be underestimated.
As a basis for long-term predictions, the models use numerous variables within an extremely complex system, including the position and motion of the jet stream and various air pressure systems. The so-called ENSO, the «El Niño-Southern Oscillation», is also decisive – although hardly for Switzerland and Europe. It describes the complex system in the South Pacific, which is reflected in the irregular characteristics of ocean temperatures and wind systems.
2023 will very likely be a transition year, in which the past – longer than average – La Niña phase will give way to an El Niño event that is already looming.
Institutes such as the National Centers for Environmental Prediction (NCEP) in the US make medium to long-term forecasts for precipitation, pressure distribution and temperatures. In Europe, the European Center for Medium-Range Weather Forecasts (ECMWF) is considered the best place for forecasts slightly further into the future. But the German weather service or the French counterpart Méteo France also determine trends in the longer term.
The focus is on the forecast period between June and August, the period of the meteorological summer and the highest temperatures of the year.
Due to global warming due to climate change, it is not surprising that the models for both Europe and Switzerland assume higher temperatures than the norm – the years 1993 to 2016 are considered the norm here. For Central and Southern Europe in particular, there is a good chance that the average temperature in summer will be in the upper third of previous years.
The following map shows the deviation of the predicted temperatures in degrees Celsius. For most regions, the models assume that it will be between 0.5 and 1 degrees warmer than the norm. However, both the average of the deviations and the probabilities are lower in most regions than in the May 2022 forecast for last year’s European summer.
Looking at global forecast temperatures, the upcoming El Niño event is already clearly visible: according to all models, both sea and air temperatures will be higher than normal in the southeastern Pacific Ocean off the coast of South America, while the temperatures for that on the west coast of the US or in and around Australia hardly rise.
One thing is clear: such long-term trends are accompanied by great uncertainties for both temperature and precipitation. This circumstance is also communicated accordingly by the institutes and it is important that such possible trends are not compared with precise short term weather forecasts. Rather, they indicate the probability with which the models assume certain events. These can sometimes rise to 50 or 60 percent, so that no real trends can be seen (yet).
That said, there seems to be slightly more agreement between the models for temperatures than for precipitation amounts. The latter, unlike temperatures, for example, are not subject to a long-term trend, which could explain the larger differences between the models.
The model, which combines the calculated probabilities of all models, shows few deviations with regard to the amount of precipitation. However, they tend to assume that the amounts are slightly above average rather than too small. In all eight models given, the chance that Europe is too dry over a large area is classified as small.
Most models assume the opposite: six out of eight predict more rain than average, especially for Western and Southern Europe. This is especially true at the beginning of summer i.e. the month of June. However, the ECMWF writes: “The predicted anomalies are – in the analysis of the average value – small; in reality, such amounts of rainfall would not make a significant difference to possible pre-existing drought conditions in these regions.
The trends of the models at the global level are clearer again. All models predict an El Niño event, which is also reflected in patterns in terms of precipitation: the west coast of South America will receive heavier rain as a result, while Australia and Indonesia will experience drier months than average.
The (provisional) conclusion is: If the predictions of the institutes are correct, the weather will be significantly warmer than normal. And slowly but surely it becomes clear that the new standard is significantly warmer than the standard. But: it will probably not be as hot and especially not as dry as last year.
Source: Blick
I am Ross William, a passionate and experienced news writer with more than four years of experience in the writing industry. I have been working as an author for 24 Instant News Reporters covering the Trending section. With a keen eye for detail, I am able to find stories that capture people’s interest and help them stay informed.
