Wetenschap - 8 maart 2016

Forecasting extreme weather

Roelof Kleis

What is extreme weather actually? What does climate change mean in that regard and how can we best inform the general public about this? Albert Klein Tank of the Royal Netherlands Meteorological Institute (KNMI) will be researching these issues as Wageningen’s new professor of Climate Services.

Professor of Climate Services doesn’t sound very extreme.

‘It’s true that the name is rather cryptic. We are used to weather forecasts and warnings. Those are services and to provide those services, you need a huge flow of data. The crux is to develop that data and make it work for climate change as well. This is a young discipline and there is still plenty of research to do.’

 Such as?

‘What is the interrelationship between the trends we see in the weather and climate extremes? Can we create climate scenarios that say something about extreme weather in the future? Will we get more coastal storms or flooding in a certain area? What are good indicators for agriculture to take into account? If you say rainfall will increase by four percent, what does that mean for the sector? What are the implications of an increase in heavy showers for sewer pipe dimensions? Which crops would be suited to the climate of the future?’

What is normal weather actually?

‘Meteorologists around the world all adopt the same standard: normal means a 30-year average. At the moment, the normal period is 1981-2010. That period will change again in 2020. So normal is an agreed standard, no more and no less.’

Students are highly inventive and innovative. And that gives me good ideas in turn.

And how do you know when weather is extreme?

‘That’s a difficult question to answer scientifically. You can make models of the weather without climate change and use those to estimate the probability of extreme weather. You can compare that probability with the extremes we are seeing now. Based on that, you can make statements about weather extremes. But of course you can never say whether an individual extreme is because of climate change or not. What is more, an extreme is not always down to the climate. Sometimes it can just be a combination of circumstances. A north wind, water coming in from Germany and rain can, in combination, cause our rivers to flood.’

Looking forward to your new job?

‘Yes, working with students re-energizes you. Students are highly inventive and innovative. And that gives me good ideas in turn. Working at a university will let me explore the subject in great depth, which I never get around to at KNMI.’