How climate change affects the wind

Interview: Manuel Vogel

surf: Meeno, your company WetterWelt offers wind forecasts for sale. Why spend money on things that are available for free on the internet? Every windsurfer can choose between various wind forecast services there...

Meeno Schrader: I founded the company 15 years ago because I realised that the quality was not at the level it could be. That still applies today. Of course, we don't just make forecasts for water sports enthusiasts, but have a complete portfolio: Commercial shipping, regatta sailors or even water sports enthusiasts. Every windsurfer or sailor knows the problem: you're looking forward to the wind, take time off work, go to the spot, but the forecast isn't right. In the end, the question arises: "Was this forecast really free? Or did I perhaps spend more on petrol and time than on a top forecast that I can rely on?"

How do you think the differences in forecast quality come about? What do you do differently?

Almost all wind forecasts that are available free of charge on the internet are based on the American GFS model. This model sometimes fits perfectly, but often not at all. It simply lacks consistency. The main difference with us is that we calculate seven different weather models. Some of them are our own developments that we run in our computer centre, but we also buy in raw data and refine it. This involves data sets that are quite expensive, which is why you can't give them away for free, especially as we only employ trained meteorologists who are able to interpret this data and read between the lines. It's obvious that a forecast based on seven models is more accurate than one...

...because every model has certain strengths and weaknesses?

Exactly, our regional model, for example, has a resolution of one to two nautical miles, depending on the settings, and we even calculate the local model for racing down to 500 metres. This is extremely high resolution, which means that very small-scale effects such as thermals, sea winds or jet effects can also be modelled. This is of course very special and important for racing, for example. It's not about statements such as: "On Sunday there will be a westerly wind of 15 knots", but the skipper wants to know whether he can take advantage of a short wind shift of two or three degrees after the start at 13:00. Maximum precision is required. Ultimately, it's like Formula 1, the technical developments of which will also arrive in mid-range cars at some point. Precise forecasts therefore also benefit the amateur surfer.

Hobby surfers probably don't care whether the wind shifts a few degrees or not, but for spots that work due to local effects, the usual forecasts are sometimes fundamentally wrong. Is the common GFS model simply too rough for many spots?

Often already. I was in Rio de Janeiro in 2014 to prepare for the Olympic Games. There is also a very complex and small-scale wind system there, which we first have to measure and record in order to be able to provide good forecasts for the sailing teams. Lake Garda is another good example that many windsurfers are familiar with. Standard models such as GFS, in which the grid points are sometimes 30 nautical miles apart, don't get any further because all the measuring points are located on the surrounding mountains and the narrow lake in between is not even recognised by the model. And even with thermal effects on the Baltic Sea, the local effects have to be taken into account in order to make precise forecasts.

The weather services always score points with a long forecast period, often seven days. Does that make sense?

This is actually misleading. Of course, the models also spit out some decimal place for a 14-day forecast, but this has little to do with a real forecast. From five days onwards, we are talking more about a trend.

Let's move away from the small-scale to the big picture - you are also very involved in climate change and give many lectures on this topic. To put it bluntly, is climate change to blame for the hot, windless summer?

First of all, we are not talking about the future when it comes to climate change, we are already in the middle of it and as a meteorologist you simply have to deal with it. The train is rolling! I've been working on this for over 30 years and even back then we had findings that were very close to what we have today, I would say an 80 per cent accuracy rate. Nevertheless, little has happened since then to counteract this.

What exactly can we expect?

I don't believe in terms like "climate catastrophe" and other scaremongering. Nevertheless, we cannot close our eyes to this, but should recognise the connections and not be lulled into a false sense of security by trade associations and lobbyists. Before I go into the specific changes for water sports enthusiasts, I would like to look at the big picture: climate changes are measured over large periods of at least 30 years and represent the background noise, so to speak, on the basis of which our daily weather then develops. To date, the global average temperature has risen by 0.6 degrees compared to the pre-industrial age. That sounds ridiculously low. But this increase in the average is accompanied by extreme changes in daily weather patterns, for example the sharp increase in extreme events such as storms, droughts and floods. Many of the conflicts we see today - for example when thousands of people flee from Africa across the Mediterranean to Europe or join movements such as IS because it promises them greener pastures - are in part already the footprints of climate change, simply because the basis of life there is collapsing and people are clutching at straws. In politics, this is called "economic refugee", but actually "climate refugee" would be more appropriate. You can just imagine the effects of the predicted warming of two or three degrees by the end of the century. Also for all water sports enthusiasts.

Let's ask a heretical question: golden times could be ahead for surfers, right? More storms, warmer winters and in summer the Baltic Sea is 25 degrees...

Of all the parameters, the forecast of wind speeds in the future is the most uncertain factor and many models reach their limits here. We can only speak of a trend here. Nevertheless, there are indicators that predict a slight increase in wind speeds on a global scale. Globally, an increase of 0.1 knots is expected, i.e. around one per cent.

That sounds disappointing!

Here, too, it is the same as with the temperatures: small changes in the average, major effects in the extreme events. For example, the models predict an increase in storm days in northern regions such as Denmark by two to five days per year. We have been observing increased storm activity in the North Atlantic since 2006, but this period is of course still too short to derive a general trend from it. Surfers can probably look forward to more storms for the time being. However, more storms on the one hand also mean a swing in the other direction - so there could also be increasingly longer periods with little wind, as is currently the case.

What about the water temperatures? Will we soon be surfing the Baltic Sea in shorts in summer?

The fact that summers will become drier and warmer overall in the future and that water temperatures in the North Sea and Baltic Sea will reach well over 20 degrees also seems positive for the time being. The North Sea is already 1.7 degrees warmer on average today than it was in the 1960s, and a further two degrees are expected by the end of the century. This is a massive signal, but it brings with it major problems: plagues of fire jellyfish and box jellyfish, algal blooms and so on are likely to dampen the joy of warm water...

Many of the last few years on the coast have been characterised by a mild, stormy winter into January and a hot summer - algae and jellyfish plagues included. That fits the picture, doesn't it?

Yes, years like 2014 or 2018 do indeed fit perfectly into the picture of a general trend and show what we can regularly expect in the future. Pronounced westerly winds in winter with lots of storms, but also 20 to 30 per cent more precipitation than before, mostly as rain. On the other hand, longer, dry periods with very little wind in the summer months. But in other years of the last decade, too, there have always been long phases that fit well into the picture of climate change. Overall, the following applies: on average, very little changes, which makes us believe that everything is not so bad. The extreme values will be decisive and these will continue to increase in the future.

So surfing through the German winter and bridging the windless summer on the Canary Islands?

I would be cautious about that. The Canary Islands are supplied by the north-east trade wind, which is created by the stable Azores High, which normally forms over the Atlantic in summer. In recent years, we have observed that the system is no longer as stable as we know it from earlier periods. Here, too, the observation period is still too short to be able to say with certainty, but many observations indicate that this system is becoming increasingly unstable and that weather conditions are occurring that are completely abstruse - westerly winds instead of strong north-easterly trade winds and this in the middle of midsummer, which we must also expect more often in future.

Are the Canary Islands losing their reputation as a wind bank in summer?

As I said, for a well-founded scientific statement we need to look at this for 30 years. But there are pieces of the puzzle that fit into a certain picture and scenario. On the Canary Islands, too, there will probably be little change on average, but the extremes will increase. In concrete terms, this could mean that you could spend two weeks in the doldrums in Pozo in August, but also that the trade winds could be extremely strong. The uncertainties are increasing and every surfer will have to live with this in the future.