Key-figure: 77%

77% of  large cities will be subject to a very different climate by 2050

Imagine London with a climate similar to that of Madrid today, Paris with the temperatures of Canberra and San Diego with those of Tripoli. This will become reality in the near future according to a scientific study by the University ETH Zurich published in July. Through these projections and comparisons with the current climate of cities, this study clearly reveals the impact of climate change to a wide audience. Its authors hope it can also help urban planners to foresee these new challenges.

The researchers studied the climate of 520 large cities around the world, according to 19 variables including temperature, rainfall and different averages. Their projections were established using an voluntarily optimistic model that assumes that carbon dioxide emissions will stabilise from now to the middle of this century, in such a way as to limit the rise of the global mean temperature to 1.4°C in comparison to the pre-industrial era.

The resulting general trend is that there will be less seasonal difference in temperatures, while extreme events will be more recurrent and more acute (wetter rainy seasons and drier dry seasons).

In 2050, in climatic terms the cities of the northern hemisphere will resemble those located some 1,000 km to the south, with temperatures that will increase by 3.5°C in summer and 4.7°C in winter. Tropical regions will be subject to an increasing number of extreme meteorological events.

Although 77% of the cities studied will be subject to a considerable change in their climates, the others will be faced with new conditions that they will have to deal with.