Climate scientist René van Westen: ‘We didn’t expect such a media storm’

Disastrous. That’s how physicist René van Westen describes the possible consequences for the climate if the Atlantic Gulf Stream collapses. Van Westen is a postdoc at the Faculty of Science, where he and several colleagues use physics models and climate data from the past to predict future scenarios. Their latest study, published on February 9 by the prominent journal Science Advances, is about Amoc, the Atlantic Meridional Overturning Circulation. This current carries warm water from the south to the north of the Atlantic Ocean. Evaporation makes the water saltier along the way, and therefore heavier. As a result, it sinks to a deeper part of the ocean, where it moves southwards again as a cold undertow. Because of Amoc, the climate in Western Europe is relatively mild. 

Global warming is increasing the amount of fresh meltwater (water that melts from glaciers or snow) entering the stream up north, which weakens Amoc. The climate models published by Van Westen and his colleagues show a steady deterioration of the stream, which can cause a tipping point that will lead the current to collapse completely and quickly. If that happens, sea levels could rise by a metre, temperatures in Europe could drop by 15 degrees, and the dry and wet seasons in the Amazon could be reversed.

Once the tipping point is reached, Amoc’s collapse would take a hundred years, bringing about the consequences above. A century is far too short a time to adapt to the new climate, explains Van Westen, who was not surprised by the discovery of the tipping point. “There were already many indirect observations, reconstructions and simple models that showed a consistent picture. But we still had to show it. We were very excited when we discovered the tipping point. It’s a breakthrough.” 

The researchers weren’t expecting Amoc to change this quickly. “For all we knew, the deterioration could take place over five hundred years instead of a hundred. A century is a relatively short period for typical climate timescales. With these results, it is not possible to say when the tipping point will occur, but we are moving towards the tipping point.” Suppose the tipping point happened today, most of us would face the consequences in our lifetimes. “It can disrupt our society tremendously.” 

Criticism
Van Westen’s article was well received, for the most part. “We were thrilled that most comments from experts in our field were positive,” he says. But there has been some criticism as well. For example, the Dutch newspaper Trouw invited Professor Sybren Drijfhout, from the Royal Netherlands Meteorological Institute (KNMI), to explain Van Westen’s study as an independent expert. Drijfhout called the model used by Van Westen “too simple.” But the UU researcher was not put off by the critique, on the contrary: “I enjoy reading things like that and I agree with him: our model is a simplification. It is based on thermodynamics and we have been able to calculate the tipping point. We are now addressing their feedback in our follow-up research. It only made us more curious.”

Media storm
The last time Van Westen published an article on Science Advances, he was approached by five journalists. But the Monday after the publication of the latest piece, which he penned alongside physics professor Henk Dijkstra and climate researcher Michael Kliphuis, nobody had called him yet. “I supposed the media would not pay that much attention to it this time.” Later that day, an article about the research, co-written by Van Westen and his colleagues and aimed at a broad audience, was published on the American website The Conversation. Soon, other media began to approach him too. “I believe that article started it all. I opened my laptop on Tuesday and the e-mails just kept on pouring. Each time I walked away to get coffee, there would be four new messages when I got back.’" 

Van Westen ended up giving 35 interviews and appearing 15 times on live television, radio and YouTube channels. He enjoyed it. “In general, everyone was very friendly. I’ve only received two angry e-mails.” Van Westen was approached by major international media such as CNN and The Guardian, but also by regional media and individuals with scientific shows or podcasts. “I said ‘yes’ to everything.”

The media storm went on for three weeks. Van Westen would wake up early in the morning and speak to journalists until late at night. “I’ve been working non-stop. When I gave my first lecture on February 14, I just didn’t know what to do with myself.” The attention has now waned somewhat, but Van Westen still speaks to a few journalists every week. He looks forward to the end of the lecture block so that he can recover a bit, but satisfaction prevails. “Normally, when you publish something, you just have a drink with your colleagues. You’re mostly happy that it’s finally out. I am well aware that this situation is exceptional.”

Influence
“The scenario we might be facing in the future turned out to be a wake-up call. We thought our work was noteworthy, but we didn’t foresee such a media storm. I’ve noticed that people were significantly triggered by it.” X users suggested that the study should be on the Parliament’s agenda, for instance. 

Even though the results were the talk of the town for a while, Van Westen does not expect the study to lead to more political action. “I’m pretty down-to-earth about it. Climate scientists have been saying for a long long time that the climate is changing and that this change has harmful consequences, so we need to do something. I see our study as an extra page on top of this pile of scientific articles. The evidence is already overwhelming. But it would be great if it would nudge politicians in the right direction because there needs to be more and more urgent climate policy.”

Preparation
Before the interviews, Van Westen spoke with his colleague Henk Dijkstra to define the message they wanted to convey in the media. “I did almost all the interviews, so we were able to be pretty consistent in what we put out. Some journalists were very much angling for a statement about when the tipping point would occur exactly, but I just kept on saying: ‘We don’t know.’” 

Van Westen also asked Peter Kuipers Munneke, a meteorologist and weatherman at NOS who is affiliated with the faculty, for advice. One of the things Kuipers Munneke warned Van Westen about is that journalists sometimes use silence to get the interviewee to make a bold statement. “Peter’s advice was to give journalists something catchy, something that’s a bit edgy. We decided to focus on the unexpectedness of the speed of the collapse. We were genuinely surprised by it and I was able to substantiate that well.” Van Westen looks back on the media attention with satisfaction. If it ever happens again, he will do almost everything the same way. The only thing he would do differently is delegate. “I would forward the questions that come in by e-mail to my co-authors because they took an inordinate amount of time.”

In the end, the study was more popular abroad than in the Netherlands. Van Westen has a theory to explain it: “I was approached by a Dutch show but, in the end, they decided not to make a story about it. I saw angry questions about that on LinkedIn, like: ‘Why not?’ I’m not sure why, but I think climate communication can be a bit difficult for them. The message of our study is that Amoc’s collapse would cause the weather to get colder in some regions, not warmer. That could be fodder for climate sceptics.”