Climate change reminds me of human actions, high temperatures, extreme weather events, 7.9 billion people, mitigation, and adaptation processes. This picture taken from the top of the Tokyo Skytree on the 5^th of August 2015 visualizes all of this. The colour is grey: very few trees and green areas can be found in Tokyo. Human actions re-designed the area, with buildings of any shape everywhere. The picture is not clear because the air is hazy, due to manmade pollution. The temperature was very high, since we were in the middle of an intense and long-lasting heat wave with temperatures around 40°C. A heatwave that caused 55 deaths.

I was in Tokyo to give some lectures at the Japanese Meteorological Agency (JMA), and the heatwave was one of the meal conversation subjects. Since Japan had stopped all its nuclear power stations following the Fukushima disaster, the country had enough electricity to cool buildings only down to ~ 30°C, but not enough to air condition the tube. Moving around was a health challenge, but it was still possible since once you reached a building you could cool down. We were talking about the weather conditions, whether they had been predicted and how they would change in the following days. We were also talking about the hundreds million people who do not have the resources to adapt and survive these weather extremes. Weather extremes that we, humans, with our activities, have made more and more frequent and intense.

This picture illustrates not only the conditions we were and are experiencing, but also the challenges we have to face. About 56% of the world population lives in cities. Cities consume about 78% of the world energy and produce about 60% of the greenhouse gas emissions. If we manage to completely transform and redesign cities like Tokyo into “post-cities” that need less energy, where people need to move less to live, eat, study and work, places where food comes from quasi-to-zero-km agriculture is possible, where pollution is very-close-to-zero, then we would have found a way to control climate change.

Roberto Buizza worked at the European Centre for Medium-Range Weather Forecasts from 1991 to 2018, where he had been a key developer of its prediction systems, and served as Head of the Predictability Division and Lead Scientist. In November 2018 he joined ‘Scuola Superiore Sant’Anna’ of Pisa, as Full Professor in Physics, where he has established a new initiative on climate with the support also of Scuola Normale Superiore of Pisa and Istituto Studi Superiori IUSS of Pavia. Expert in numerical weather prediction, Earth-system modelling, ensemble methods and predictability, he has more than 230 publications, of which 110 in the peer-reviewed literature (SCOPUS H-index 47; Google Scholar H-index 61).