Meteorologist tiersch: “the weather is a chaotic system”

Now it's official: It's summer. But the weather is not sticking to the calendar; for weeks now, it has felt like the perfect summer in many parts of Germany. It's nice for days at the swimming lake, "it's not normal," says Gunther Tiersch.

The meteorologist and head of the ZDF weather editorial department is certain that records for temperature and precipitation will be set more frequently in the future. A conversation about the typical German summer, the accuracy of weather forecasts and the question: Was everything better in the past??

Mr. Tiersch, how will the summer of 2018?

Gunther Tiersch: So far, the weather models have shown typical summer weather until the beginning of July: changeable, with westerly winds, areas of rain every now and then, then sun again. In the north it will always be a little cooler and wetter than in the south.

But since yesterday we suddenly see mad summer days, as we wish them: hot and sunny. Whether that will last through July and into mid-August can only be seen between the 8th and the beginning of August. and 15. July say.

It feels like we've had summer for a few weeks now – is that normal??

Tiersch: No, that's not normal and is due to the specific weather situation. Such a drought throughout May in the north and also in June, we last experienced that in 2003. These are extremes that rarely occur. This year we also had the warmest April and warmest May since weather records began in 1881.

"We used to have real summers" – a phrase you often hear. Were the summers better in the past?

Tiersch: No way. There were fluctuations there as well. Of course there were great summers. 1959 was one, 1975 and 1976, also in northern Germany. I remember that the moor burned in Lower Saxony. But this is not the typical German summer either.


What does the typical German summer look like?

Tiersch: It was varied. It is always wet and then a little nicer in between for five or ten days. And then it hits again from the west and an area of rain passes over us.

They say it was the warmest April, the warmest May. Is that coincidence? Or climate change?

Tiersch: I do think that we are feeling the effects of climate change here. Always just a little bit. But the records are piling up, especially in the last 30 years.

The German heat record comes from July 2015: 40.3 degrees were measured in Bavaria. Do we have to get used to such temperatures?

Tiersch: We will certainly have to prepare for hot spells when temperatures rise to between 30 and 40 degrees. But it will not be like this every summer for the time being. But there are forecasts that say by 2050 or 2060, almost all summers will be like 2003: dry and hot.

What do these changes mean for us??

Tiersch: Heat spells claim lives. The circulatory system of older people no longer cooperates. And insects, which are not native to our region, will spread more and more – and theoretically can also transmit diseases.

You can already see it now: We have the tiger mosquito on the Rhine, in Wurzburg, in Jena, and it is still on its way north. The tiger mosquito, for example, can transmit dengue fever.

Also the storms seem to become more extreme in Germany.

Tiersch: And the extreme storms will increase. The steady warming of the atmosphere is creating more and more energy, and that in turn is causing stronger weather systems, such as thunderstorms. There are more heavy rain events, more floods.

When up to 50 liters of rain per square meter fall in half an hour – which sewer system in the cities should absorb these amounts of water? Cities like Berlin, Hamburg or Frankfurt are already trying to use open spaces where rainwater can run off the roofs and seep away – instead of running into the sewage system. Playgrounds, for example, are used for this.

Meteorologist tiersch: 'the weather is a chaotic system'

Rain, heavy rain, continuous rain? That's the name of what's coming down

Can weather be predicted at all? Or do we have to speak of estimation?

Tiersch: We make predictions. We now have an accuracy of 90 percent for the next 36 hours. Nine out of ten predictions are correct. Even the farmers can't do that.

Will you be right at some point in ten out of ten predictions?

With the forecast for the next day I can imagine that. Even for the second, maybe even the third day. After that no more. The weather is a chaotic system. But theoretically, we could predict the weather for years to come.

If?

Tiersch: … we would know exactly what the state of the atmosphere is at the moment and how the peripheral areas – i.e. the development of people, the concreting of the landscape, the traffic, the energy consumption – will develop in the next few years.

But we would then have to have a measuring instrument on every centimeter of the earth to really be able to say: This is the state of the atmosphere right now. Then we could feed the computer models with it.

Mr. Tiersch, now to the weather forecast for tomorrow, Friday the 22nd. June.

Tiersch: I think Friday – just like the beginning of summer today – will be relatively cool with rain in northern Germany. Then it will also be cooler in the south. Only at the weekend, on Sunday, it will slowly get warmer again. You can check that out now.

If you're wrong, we'll send you the letters to the editor.

Tiersch: Rather not.

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