Geert Jan van Oldenborgh, who has died aged 59 of multiple myeloma, was co-founder and member of a team of scientists who identified — at speed and while politically a hot topic — the links between human-induced climate change and forest fires, heatwaves, drought, flood and other specific meteorological catastrophes.
This is trickier than it sounds. Extreme events have always happened, and for decades most climate scientists were not willing to say that this or that flood or heatwave was directly powered by ever-higher greenhouse gas emissions driven by profligate fossil fuel use. If they did, it was usually long after the event.
That began to change six years ago, when Oldenborgh co-founded World Weather Attribution, an initiative designed to examine with scrupulous care the signal of climate change within individual and seemingly random extreme weather events.
In August 2021 he and colleagues established that the murderous floods of July 2021– in which more than 200 died – in Belgium and Germany were made significantly more probable by global heating. In July, the researchers found the unprecedented temperatures that in June scorched the US Pacific northwest and Canada would have been “virtually impossible” without climate change. After an unusually warm March, sudden April frosts devastated vineyards and orchards in central France; by June, Oldenborgh and his collaborators had identified once again the fingerprint of climate change.
And in this year alone, using the traditional – and much slower – medium of the peer-reviewed scientific paper, Oldenborgh and his partners also established the role of human-triggered climate change in the forest fires that seared Sweden in 2018; the hazard of Australian bushfires; the pattern of drought and higher temperatures in East Africa; and the heatwaves that hit Europe in June and July 2019. A fifth study pronounced the prolonged heat in Siberia in 2020 “almost impossible” without human influence. All this in the last 10 months of his life.
He was also the creator and guardian of an extraordinary digital platform called Climate Explorer, home to a vast assembly of data – including systematic measurements of global temperatures; global ozone loss; sunspot counts; sea current strengths; sea ice cover; UK temperatures since 1772; Netherlands rainfall since 1906; ocean temperatures to depths of 100 metres, 700 metres and 2,000 metres; tropical cyclones and Atlantic hurricanes; Asian monsoon droughts reconstructed from 1300 to 2005; and even Netherlands beechnut harvests from 1930 to 1967 – all now exploited by thousands of researchers worldwide.
In April, his work with Climate Explorer earned him the European Meteorological Society’s technology achievement award. In the same month, he was made a knight of the Order of the Netherlands Lion for his research. In September, his work with World Weather Attribution earned Oldenborgh and his research partner Friederike Otto, of Imperial College London, a place among Time magazine’s annual list of the world’s most influential people.
He was born in Rotterdam to Jan van Oldenborgh, a lawyer, and Wil Lijbrink, a psychoanalyst. While still at school in the Netherlands he won a scholarship to Lester B Pearson College, near Victoria, British Columbia, where he studied Chinese. He graduated from Leiden University in the Netherlands in 1986 with a master’s degree in theoretical physics, which he pursued along with mathematics and Chinese, and then in 1990 completed his PhD at the University of Amsterdam, and at NIKHEF, the Netherlands Institute of Nuclear and High Energy Physics.
He taught and continued research into elementary particles at the Ludwig Maximilian University in Munich and the Paul Scherrer Institute in Switzerland, and returned to Leiden in 1994.
In 1996 he joined the Royal Netherlands Meteorological Institute, known as KNMI, to begin working on ways to improve forecasts of that recurring natural climate phenomenon in the Pacific known as El Niño, which every few years upsets global weather patterns. “Climate research turned out to be much more suited to my personality and offer more possibilities,” he told an interviewer last year, “and hence it was simpler to make significant contributions. It was also much easier to explain to the public and the answers more relevant for society.”
He put his name to more than 150 peer-reviewed research papers. His research career took him into the complex worlds of seasonal forecasting, climate modelling and – eventually – event attribution. He contributed directly to one of the global reports by the Intergovernmental Panel on Climate Change in 2013, and in 2019 was appointed visiting professor at the University of Oxford.
He would later recall two “really nice” moments in science when he felt he had discovered something new. The first had been during his career as a particle physicist. The second occurred while brainstorming with a KNMI colleague to understand why Antarctica could be melting while the extent of the sea ice around it was increasing. They reasoned that warming ocean currents would be eating away at the base of the shelf ice, while, counterintuitively, the melting land ice made it possible for the area of the shelf to increase in the southern winter. “In my maybe simplistic philosophy of science, the truth is the way the world really operates. The scientific method prescribes a way to approximate this truth,” he said. “Although it can never fully describe it, it can come closer.”
In 1982, he met his wife, Mandy, a psychotherapist and clinical psychologist; they married in 1987 and had three sons. In 2013, he was diagnosed with Kahler’s disease, an incurable form of blood cancer also known as multiple myeloma. “I had been walking around with it for at least one and a half years before that,” he said.
But he continued to work through years of treatment. On 20 September he apologised for a difficulty on the Climate Explorer website. “Unfortunately, my health only allowed me to fix it tonight,” he wrote. “Please report remaining problems.” It was his last entry.
He is survived by Mandy and their sons, Elwin, Leon and Ingo.