Geert Jan van Oldenborgh, 59, Dies; Linked Weather Disasters to Climate Change

With a colleague, he founded a group that quickly analyzes heat waves and other extreme events for signs of global warming’s influence.,

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Geert Jan van Oldenborgh, a Dutch climate scientist who pioneered ways to help the public see the influence of climate change in heat waves, floods and other extreme weather disasters, died on Oct. 12 in Gouda, the Netherlands. He was 59.

His death, in a hospital, was caused by pneumonia, a complication of multiple myeloma, for which Dr. van Oldenborgh had been treated for years, the Royal Netherlands Meteorological Institute said. He was a senior researcher at the institute and had worked there for 25 years.

With Friederike Otto, a climate scientist at the University of Oxford, Dr. van Oldenborgh in 2014 founded World Weather Attribution, a loose-knit group of scientists who undertake rapid analyses of extreme weather events, usually just days after they occur. One of the group’s most recent studies found that this summer’s brutal heat wave in the Pacific Northwest would have been “virtually impossible” without climate change, as Dr. van Oldenborgh told The New York Times when the report was released.

World Weather Attribution has undertaken more than 40 analyses to date, cobbling together different groups of scientists. That work has played an increasingly important role in demonstrating not only that climate change is real but also that it is already having effects around the world.

The latest assessment of climate science by the Intergovernmental Panel on Climate Change, a United Nations body, cited the growing field of attribution science in stating unequivocally that global warming had led to an increase in the frequency and intensity of extreme weather events.

Heidi Cullen, who as director of communications at Climate Central, a research group in Princeton, N.J., was involved in the formation of World Weather Attribution, said that before such analyses became prevalent, “there was this whole mantra among scientists that you cannot attribute an individual event to climate change.”

The group’s work changed that, said Dr. Cullen, who is now director of communications and strategic initiatives at the Monterey Bay Aquarium Research Institute in California. Their studies showed, among other things, the influence of climate change in the extreme rainfall of Hurricane Harvey in Texas in 2017; in flooding in France and Louisiana in 2016; and in the severe Australian wildfires of 2019 and 2020.

So-called attribution analyses had been done before. But because they involved running computer models and were subject to extensive peer review by independent experts, they took time and were usually published a year or two after the weather event in question. The goal of Dr. van Oldenborgh and his colleagues was to find a link to climate change — or not, as was occasionally the case — when the disaster was still fresh in the public’s mind.

To do that, they used models that had already been run, a process Dr. van Oldenborgh described in 2016 as “precooking everything that we can.” They also released their studies before they were peer reviewed and published in scientific journals, arguing that the basic techniques that were used had previously been found valid by experts.

The lack of peer review made some in the scientific community uncomfortable, Dr. Cullen said. “We were still trying to convince other scientists that this could be done,” she said, adding that Dr. van Oldenborgh’s expertise and leadership were critical to gaining acceptance.

Dr. van Oldenborgh was born on Oct. 22, 1961, in Rotterdam. His father, Jan, was a lawyer; his mother, Wil Lijbrink, was a psychoanalyst. He studied in British Columbia before receiving a master’s degree at Leiden University in the Netherlands and a doctorate at the University of Amsterdam, both in theoretical physics.

He is survived by his wife, Mandy, and three sons, Elwin, Leon and Ingo.

Dr. van Oldenborgh came to the meteorological institute in 1996 as a postdoctoral researcher. Up to that point his focus had been on particle physics, but at the institute he began to study El Nino, the recurring climate phenomenon that affects weather worldwide.

“Climate research turned out to be much more suited to my personality and offer more possibilities, as it was a newer field and hence it was simpler to make significant contributions,” he said in an interview last year. “It was also much easier to explain to the public, and the answers were more relevant for society.”

His early work at the institute included developing Climate Explorer, an online platform through which anyone can analyze climate data. “It has been used by probably every meteorology or climate science student in the world,” said Dr. Otto, who is now a senior lecturer at Imperial College London.

Dr. van Oldenborgh soon became interested in climate extremes, said Maarten van Aalst, the director of the Red Cross Red Crescent Climate Center, because it was extreme events, rather than gradual impacts like rising sea level, that affected most people, particularly in poorer areas.

“It was changing extremes we were interested in,” said Dr. van Aalst, who first worked with Dr. van Oldenborgh in the mid-2000s. “There was basically nothing on that in the literature.”

One of the first World Weather Attribution studies was of a European heat wave in July 2015. Then, Dr. Otto said, as with more recent analyses, Dr. van Oldenborgh’s focus was more on the numbers, while hers was more on the words. “He would make sure the numbers were all correct and that no one from the many people we worked with made any errors,” she said.

The desire to analyze an event as soon as possible was stressful, Dr. Otto said, because of the need to find scientists willing to drop everything for a week or two and then to coordinate the research at all hours of the day or night.

“There was always a very positive energy,” she said. “Everyone who we worked with, we did so because they felt what we do is really important.”

And Dr. van Oldenborgh shared more than just his thoughts about the scientific analysis. “We’d be exchanging emails about the work at 4 a.m.,” Dr. Otto said, “but we also talked about other stuff, like what’s the right age to read Harry Potter to your kids.”

In his attribution work, Dr. van Oldenborgh believed that “everything has to be open, everything has to be transparent, so other people can trust you,” Dr. Otto said. “That was also his attitude toward life.”

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