The BBVA Foundation Frontiers of Knowledge Award in the Climate Change category goes, in this ninth edition, to climatologists Syukuro Manabe and James Hansen, separately responsible for constructing the first computational models with the power to simulate climate behavior. Decades ago, both men correctly predicted how much Earth’s temperature would rise due to increasing atmospheric CO2. The scores of models currently in use to chart climate evolution are “heirs” to those first developed by Manabe and Hansen.
Syukuro Manabe (Japan, 1931) was working on weather prediction in the 1960s, when he set out to build a numerical model to simulate atmospheric behavior. Scientists then had no inkling that CO2 concentrations were augmenting due to fossil fuel combustion, and none could suspect that a process of this type might end up altering the Earth’s climate.
He began using computers in his work to create the first ever model of global atmospheric circulation, including elements like water vapor, winds and atmospheric heat transport. To get a firm grasp on this last variable, greenhouse gases had to be factored into the program. At the end of the 1960s, Manabe completed his model which projected that if CO2 concentrations doubled, global temperature would rise by two degrees. This was a theoretical prediction based on sparse data, which moreover could not be tested because there was at that time no reliable record of planet-wide temperatures.
From Venus to Earth
In the late 1960s, James Hansen (United States, 1941) worked at NASA’s Goddard Institute for Space Studies, researching into planetary atmospheres with a particular focus on Venus. His work there helped establish that the extremely hot temperatures prevailing on Venus were due to an exacerbated greenhouse effect.
As the 1970s advanced, it became increasingly clear that atmospheric CO2 concentrations were on the rise. There was still no evidence, however, as to what the effect might be on the world’s climate. To Hansen, it seemed far more important to study the climate of our own planet as it confronted this change, with unfathomable consequences for many millions of people. He decided to switch to studying the Earth climate, and developed his own model independently of Manabe’s. The conclusion he drew was that world temperatures would rise by four degrees centigrade.
The paper setting out Hansen’s conclusions, published in Science in 1981, is important for two more reasons: it was the first to incorporate global data for Earth’s temperatures, thanks to Hansen’s invention of a new method for processing the information gathered from available meteorological stations; and it also predicted how warming would affect other processes, like oceanic circulation, the loss of Arctic ice cover or droughts and flooding.
Manabe, since 2005 Senior Meteorologist on the Program in Atmospheric and Oceanic Sciences at Princeton University (United States), stresses the importance of his colleague’s contribution: “I started working with models earlier, but Hansen was the first to use these models to make predictions.”
For Hansen, Director of the Goddard Institute for Space Studies from 1981 to 2013, and currently an Adjunct Professor at Columbia University’s Earth Institute, Manabe “has led the world in global climate models since I started my career.”
“The first, crucial conclusion of our work was to show that global climate is very sensitive to humans,” affirms Hansen, who also celebrates the fact that “climate models are much more reliable than they were years ago, with a far smaller margin of uncertainty.”