European officials say ‘climate change has arrived’

Berlin (CNN) - European officials have said climate change contributed to this week's extreme flooding, which has left entire towns submerged and more than 120 people dead.

Scientists have for decades warned that climate change will make extreme weather events, including heavy rain and deadly flooding, more likely.

Around 100 of those killed after torrential rainfall since Wednesday were in Germany's western states of Rhineland-Palatinate and North Rhine-Westphalia, where local leaders are urging the world for swifter action on climate change as villages under their watch become a new and unexpected epicenter of global warming.

European Commission President Ursula von der Leyen said Friday that flooding in northwestern Europe was evidence of the need for urgency in acting on climate change.

"Science tells us that with climate change, we see more and more extreme weather phenomenons that last longer," said von der Leyen, two days after unveiling an ambitious package of climate change proposals for the EU. "It is the intensity and the length of these events when science tells us this is a clear indication of climate change and that this is something that really, really shows the urgency to act."

What’s causing this heavy rainfall?

As the Earth’s atmosphere warms, it can hold more moisture, which in some cases leads to unprecedented rainfall. It may be that the total average rainfall in an area doesn’t change, but extremes are amplified, which can mean longer dry periods or more intense storms.

Flash flooding occurs when rain falls faster than the ground can absorb it. It is “flash” because its onset is rapid -- water levels can rise metres in minutes. When there is more water vapour in a warmer atmosphere, rainfall rates can increase and flash flooding is more likely to occur. And drought can actually compound this effect. Very dry soil can’t absorb water efficiently -- think of trying to wet a very dry sponge. While the rain is ultimately beneficial, if a region that has been experiencing intense drought gets hit with heavy rain, flash flooding is more likely to occur.

The projections for how much the Earth would warm have largely been correct, said Myles Allen, a climate scientist at the University of Oxford. But there have been outliers -- namely, the warming in Europe has been faster than predicted.

Allen said scientists expected more extreme weather events, but records are being blown away at a concerning clip -- the unprecedented heat wave in the Northwest US in late June is another recent example.

With more action, he said, climate change could be addressed in a generation. “A problem is that every climate documentary starts with an image of a polar bear, which send the message that climate change happens in the Arctic, on the other side of the world,” Allen said. “But these events show that’s not true.”