July 2021 After severe rainfall, the Arr Valley in western Germany was hit by an enormous flood. Water gushed（涌出） through the villages, killing over 100 people and damaging thousands of houses. Extreme weather events are occurring more frequently all over the world, not just in Germany. Rising sea levels and heavy rainfall caused devastating floods. From now on, every day, somewhere in the world, we will have an extreme weather event, unprecedented（空前的） weather event like we never had before. There are already over 20 million climate refugees worldwide today.

  If we don't take climate change seriously, there could soon be many more. By how much will the average global temperature rise and how much more extreme will the extremes be? It's a question of life or death. The village of Altenburg in the Arr Valley, a few weeks after the devastating flood, the clear-up operation is in full swing（摇摆）. 90% of the houses were damaged. Since the river also transported toxic（有毒的） oils, almost all the buildings have to be stripped（剥） down to the masonry（石工术）.

  Sasha Meyer was also affected by the disaster. The night of the flood is something he will never forget. At that moment, all I could do was shout out to my wife, "We are flooding!" Then she came out of the room carrying Jack（千斤顶）. I grabbed John and then we made our way straight to the attic（阁楼）. The family spent the whole night there.

  Sasha removed the roof tiles from one part of the roof. We needed to find an emergency exit because the water kept on rising. I looked out of the small window and the water had risen to the second row of roof tiles. We kept in contact with our neighbors. They were also in the top part of their house. You can see how far up the water came.

  They were also worrying about how high the water would rise. It was a terrifying moment because we just didn't know when it would stop. That night the Mayans lost everything they had. Just 15 months previously they had bought their house and moved in. From the ground floor we managed to salvage（抢救） the family records and my children's savings books. We had to throw everything else away because it was covered in mud or oil or just filth（污秽）.

  At that moment it was all about surviving and we did survive. For many years scientists have been warning that extreme weather conditions would increase with climate change. Kiravinka has no doubts that the situation is deadly serious. At the moment we are roughly one degree above the pre-industrial age temperature, which means we are already in the midst（中部） of climate change. We have to realize that the effects are increasingly serious. It's not a linear（线的） change.

  It won't just get a little bit worse, it can get considerably worse with every degree of global warming, which means a very, very tough challenge for us to adapt to climate change. The Geographic Institute of the University of Bonn. Lotar Schrot heads the master's program on the prevention（预防） and management of catastrophes here. The risk researcher sees huge communication deficits（赤字） shortly before the flood in the Aar Valley. There was a storm warning, a warning of a flood, but the residents didn't know what the consequences might be. They didn't know what should I do now.

  I heard reports of some people taking amateur（业余的） precautions and driving their car right to the top of the Aar Valley. In the end it was the only car left. The others were all swept away. The disaster in the Aar Valley showed how ineffective Germany's early warning system is. But what should be done now? I think we need a mix of different methods.

  People talk a lot about these warning apps. I have two myself on my cell phone. But if the mobile network is down, then the apps are of no use. That has become clear. A simple and effective measure would be flood sirens（汽笛）, for example. They could warn all local residents of an impending disaster.

  But the siren has to go off in plenty of time. Not when we can already see the water. If they know three or four hours ahead, then they should sound the siren and train people how to react in a situation like that. It's no good everyone getting in their car and the roads all getting blocked up with traffic jams and people drowning（淹死） that way. Rudy Gefurman, the local mayor and a member of the Voluntary Fire Brigade, is still stunned（使晕倒） by the events. We had received warnings that the flood level would reach five and a half meters.

  We heard about it in the afternoon in our fire station, but we could hardly believe it because we thought, where should all that water come from? Five and a half meters. That would have been about two meters higher than in 2016. We simply couldn't believe it. In the end, the river was up to nine meters high, flooding buildings right up to the roof. The Netherlands（荷兰（西欧国家）） are much further ahead of Germany when it comes to flood protection.

  For centuries, they've been resting land back from the sea. In the past, windmills（风车） helped to lower the water level. Nowadays, powerful pumping stations work（使工作） around the clock to keep the land dry. Around a quarter of the Netherlands are below sea level. Engineers are building even higher dikes（堤防） and flood barriers, like in Nijmegen. The whole town is surrounded by a protective（保护的） wall.

  In times of flooding, the openings can be closed off by gates or with special steel profiles. This is how a seal（封） profile looks. We use them to make a so-called cupure. They are stacked on top of each other, and the rubber profile ensures that the flood wall is sealed. This is where the cupure is built up. First, we remove this cover.

  Behind it, there is the frame for a flood wall, so we have double protection. First, we put in a base, and then we lay one profile on top of another, until they reach this height. Along with the safety barriers surrounding individual towns, the Dutch（荷兰人） have built gigantic（巨大的） flood barriers along the North Sea coast. At the Marsland flood barrier, two metal gates, each 210 metres long, protect the land behind them. The Austerschelder flood barrier stretches for nine kilometres along the coast. Although the Dutch have invested huge sums in flood management, they know that it will not be enough.

  Frank Spargarum was a member of the team which developed the Austerschelder flood barrier. Most people agreed that sea levels could rise by one metre by the end of this century. That would have enormous consequences for the flood barrier, but also for the whole area behind it. If the water rises that much, I don't think the flood barrier will be able to hold back the water in 2100. It will have to be torn down. Since higher dykes alone do not offer enough protection, the Dutch are now trying a new strategy.