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The birthday boy could not be found for hours. When the employees of the Max Planck Institute for Meteorology in Hamburg wanted to congratulate their former director Klaus Hasselmann on the most important scientific award of his life on Tuesday, all attempts at contact initially came to nothing. The 89-year-old did not answer the phone. After all, he had received the decisive call from the Nobel Committee in Stockholm beforehand: Hasselmann is sharing half of this year's Nobel Prize in Physics with the Japanese Syukuro Manabe, the other half going to the Italian Giorgio Parisi. Both halves of the award are endowed with around 985,000 euros.
Journalists from the Reuters news agency got Hasselmann on the phone: “I'm still very surprised.
I don't want to wake up, it's a nice dream for me, ”the researcher explained.
“I'm retired now and I've been a little lazy lately.
I am delighted with the honor. "
In the spirit of Alfred Nobel, Hasselmann and Manabe contributed to the good of mankind, "by giving our knowledge of the earth's climate a solid physical basis," praised the Nobel Committee.
The honor is thus, it must be said so clearly, also a political award, a few weeks before the World Climate Conference in Glasgow, Scotland.
"We can no longer say that we didn't know - the climate models are clear," said the message from Stockholm.
Calculated effect of carbon dioxide
"Great news and well deserved," said Jochem Marotzke, as director at the Max Planck Institute in Hamburg, to a certain extent, Hasselmann's successor, commenting on the news in an interview with SPIEGEL. And then he explains how the work of Hasselmann and his co-award winner Manabe complement each other: The Japanese, who has spent a large part of his professional career in the USA, for example at the US Weather Bureau and at Princeton University, have the discipline of climate modeling factually justified. “It helps us understand how the atmosphere reacts to CO₂,” says Marotzke.
Together with colleagues in the 1960s and 1970s, Manabe created the first simulations on the question of how the physical processes in the atmosphere interact with those in the oceans - and how carbon dioxide, which is produced when organic substances such as crude oil and natural gas are burned, changes the temperature influenced. It was already known that there might be correlations, for example through the work of the Swede Svante Arrhenius from the end of the 19th century. Thanks to Manabe, however, the effect could be quantified.
Only with such knowledge can climate simulations as we know them today be carried out in a meaningful way.
If you want to know how hot our planet gets, you have to understand which processes on land, in water and in the air play a role - and how these can be described mathematically as precisely as possible.
The key questions: How far do you have to go into detail?
Which seeming trivialities have to be taken into account, which can be left out for the sake of simplicity?
After all, it is important to describe a complex physical system that behaves very differently than the sum of its individual parts.
What is weather, what is climate?
Manabes Hamburger Kollege Hasselmann, er arbeitete zwischenzeitlich unter anderem an der Scripps Institution of Oceanography im kalifornischen La Jolla und an der Woods Hole Oceanographic Institution im US-Bundesstaat Massachusetts, gelang mit statistischen Verfahren der Nachweis, dass tatsächlich wir Menschen verantwortlich sind für die in den meteorologischen Daten erkennbaren, langfristigen Veränderungen der Temperatur.
This task was complicated, among other things, because the weather can fluctuate greatly in the short term. Chaotic processes determine the procedures. That is why the weather cannot, say, be predicted a month in advance. If you are looking for long-term changes in the climate, if you want to make statements for the next few years and decades, you have to be able to see through this background noise. Hasselmann succeeded in doing just that. It provided the basis for actually being able to trust long-term climate predictions.
"Model calculations provide samples," explains Marotzke. "If we then find these patterns in the observation data, we have recognized the human fingerprint." Hasselmann succeeded in doing this theoretically as early as 1979 in a work that was then largely ignored. Marotzke calls this a "stroke of genius" that came "out of nowhere". In practice, however, the ideas could not have been implemented at first - because the computing power for the necessary simulations was lacking.
But Hasselmann was able to help here too: He was instrumental in promoting the establishment of the German Climate Computing Center (DKRZ) in Hamburg, which emerged from the joint computing center of his Max Planck Institute and the Meteorological Institute of the University of Hamburg.
From 1988 to 1999 he was the scientific director of the facility, where his own predictions could also be checked and confirmed: there is a »probability of 95 percent« that global warming over the past 20 years was caused by humans and no longer of natural origin, according to Hasselmanns Balance sheet in 1995. “A clear verdict,” said SPIEGEL at the time.
"The Paris Agreement would be unthinkable without the work of Klaus Hasselmann."
Jochem Marotzke, Director at the Max Planck Institute for Meteorology
"The award to Klaus Hasselmann is further evidence of how fundamental work in German climate research pointed to climate change at an early stage," said Lutz Schröter, President of the German Physical Society (DPG).
To this day, increasingly complex climate models are being calculated in Hamburg - also with new supercomputers such as the »Mistral«, which can perform 3.6 quadrillion arithmetic operations per second.
The simulations have long since become the most important decision-making basis for politicians in international climate negotiations: "The Paris Agreement would be unthinkable without the work of Klaus Hasselmann," says MPI Director Marotzke.
The Nobel Prize for the researcher is "fantastic recognition of how fundamentally the modeling of the Earth system has advanced our understanding of the enormous risks of climate change," also praise the directors of the Potsdam Institute for Climate Impact Research (PIK), Johan Rockström and Ottmar Edenhofer. "This is not only of the highest scientific relevance, but also the basis for working on a secure climate future for all people on our planet."
But Hasselmann not only thought about the world climate and its simulation in the computer, he also dealt with other complex systems.
So he developed economic models, but also new ideas for elementary particle physics.
His goal: nothing less than a world formula.
To date, physicists have not succeeded in developing a so-called unified field theory with which the properties and interactions of all elementary particles can be described from a single source.
In particular, gravitation does not want to be inserted into the structure of the quantum theory.
The Hamburg native devised the so-called Metron model for this - but its description alone overwhelms the author of this text intellectually.
How does clutter at the smallest level affect a complex system?
The third winner of this year's Nobel Prize in Physics, the Italian Giorgio Parisi, also worked on fundamental physical questions.
And he too dealt with complex physical systems and their mathematical description - but mainly on a very, very small level.
The Italian, who in the meantime also conducted research in the USA and France, has gained recognition in the professional world primarily for his work on so-called spin glasses.
These are certain magnetic materials that are surprisingly messy: This has to do with the fact that the intrinsic angular momentum of the particles they consist of is not uniform, as would be the case with a permanently magnetic material, a ferromagnet.
Parisi has dealt with how this disorder affects the properties of the overall system at the smallest level - with results that, as the Nobel Foundation emphasizes, also have implications on large, cosmic scales, but also in biology, neuroscience and of computer technology.
The Italian also used simulations as a crucial aid for his work.
That unites him with the other two award winners, Manabe and Hasselmann.
The findings are not only interesting in the academic ivory tower.
In an interview, the newly crowned laureate Parisi was asked about a message for the world climate conference.
His answer was clear: "It is clear that we must act very quickly now for future generations."