An exploration of polar ice that reveals the link between greenhouse gas concentrations and the increase in atmospheric temperature across the planet over the last 800,000 years has earned five European researchers the Frontiers of the Earth Prize. Knowledge, with a financial award of 400,000 euros in each of its categories. The jury of the XVI edition has pointed out that research reveals that “the concentrations of greenhouse gases due to natural variability had never reached current atmospheric levels”, causing global warming caused by human activity.
The contributions of the Danish Dorthe Dahl-Jensen (University of Copenhagen), the French Jean Jouzel and Valérie Masson-Delmotte (Paris Laboratory of Climate and Environmental Sciences), and the Swiss Jakob Schwander and Thomas Stocker (University of Bern) over the past few decades have shown that records from the thickest and oldest ice deposits on Earth, located in Antarctica and Greenland, show that “changes in atmospheric concentrations of greenhouse gases—such as carbon dioxide and methane—are accompanied by systematic changes in air temperature across the planet.” Their research on the natural variability of the Earth's climate has made it possible to “contextualize the current concentrations of greenhouse gases and the global warming associated with them” within the framework of the history of our planet, according to the jury.
“The central message derived from the study of ice sheets is that CO2 and temperature are closely linked and that the concentrations of greenhouse gases present in the atmosphere have no precedent in the last 800,000 years. This has profound implications for the evolution of our planet in the coming decades and centuries,” highlights Bjorn Stevens, director of the Max Planck Institute for Meteorology (Hamburg, Germany) and president of the jury.
“The snow, from which the polar ice is formed, captures, as it accumulates, the air around it,” explains Miquel Canals, director of the Chair of Sustainable Blue Economy at the University of Barcelona. and member of the jury. “This air is trapped inside bubbles in the ice. And those bubbles are like a book about atmospheric conditions over time, which must be deciphered in terms of their composition and meaning,” he comments. The five awarded researchers have been able to reconstruct this valuable record of the Earth's climate preserved in the polar ice.
For Joan Grimalt Obrador, researcher at the Institute of Environmental Diagnosis and Water Studies (IDAEA) of the Higher Council for Scientific Research (CSIC) and nominator of Thomas Stocker, the main contribution of the winners is “to show that the current concentration of greenhouse gases greenhouse effect goes off scale. There are no precedents and we are living an experiment whose result is an unknown that threatens human beings, not nature, which has always adapted.”
Ice witnesses
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The analysis of ice cores—cylindrical samples obtained by drilling the substrate at different depths—entailed verification of the link between greenhouse gases and the Earth's temperature. Jean Jouzel's analysis of an Antarctic ice core from the Vostok base, published in Nature in 1987, constituted that verification.
Although by then there were already works based on ice cores, none reached a time before the last ice age, which began 110,000 years ago. Soviet scientists working at Vostok were able to drill through more than two thousand meters of ice thickness and thus obtain samples up to 160,000 years old; That is, they reached the interglacial period prior to the last ice age. Jouzel and his colleague Claude Lorius, who died in 2023, were able to access these samples thanks to the latter's contacts with the Vostok scientists, and this is how they verified that there was a very close relationship between changes in the carbon cycle, composition of the atmosphere and climate, three key factors in the dynamics of glacial-interglacial cycles.
Impact of human activity on the climate
A decade after the publication of that Nature, Valérie Masson-Delmotte delved into Jouzel's work and expanded her analysis to ice cores from Greenland. Her conclusions coincided with those Jouzel had obtained on the other side of the planet. “The ice cores are amazing, like time machines. The surprising thing is that we increasingly have more solid evidence that confirms the intuition of the late 1970s,” Masson-Delmotte highlights.
A key implication of this warming would be sea level rise, which has already risen by 20 centimeters since 1900 and whose expansion has accelerated since the 1990s. “We are headed for a rise of 50 centimeters by 2100 if warming is limited.” at low levels, or more than one meter if large greenhouse gas emissions are produced,” adds Masson-Delmotte.
Dorthe Dahl-Jansen's contributions have focused fundamentally on the reconstruction of the past climate based on the study of ice cores in Greenland, as reflected in a study published in 1998 by the journal Science. “We know that when temperatures rise, the ocean warms and releases CO2 into the atmosphere. Subsequently, the increase in CO2 causes the temperature to increase even more, which in turn causes the CO2 concentration to rise. And in this way the warming observed in the climate of the past occurs,” explains the researcher.
Technological innovation
All of these investigations would not have been possible without the technology necessary to obtain ice cores, and Jakob Schwander has been a pioneer in this field. Schwander has developed and improved devices to reach deeper layers of pristine ice.
Thomas Stocker has worked on measuring the concentrations of carbon dioxide trapped in the air bubbles of 800,000-year-old ice cores. From this research he drew three fundamental conclusions. “Firstly, carbon dioxide concentrations are 35% higher than in the last 800,000 years. Secondly, global warming is unprecedented in at least the last 2,000 years. And third, that thanks to the polar ice witnesses we have been able to know that there were instabilities in the climate system – abrupt changes – that could occur again in the future due to the important alterations that humans are inflicting on the climate,” he highlights. Stocker.
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