By mid-century some three-quarters of cities worldwide will have climates barely recognizable to their inhabitants today. Meanwhile, a fifth of cities around the planet, including Singapore, Yangon (formerly Rangoon) and Kuala Lumpur in Southeast Asia, will experience extreme climatic conditions that do not yet exist anywhere.

This is according to a team of scientists from the Crowther Lab at ETH Zurich, who have mapped projected climate shifts for 520 major cities worldwide by 2050.

“Even under an optimistic climate scenario (RCP 4.5), we found that 77% of future cities are very likely to experience a climate that is closer to that of another existing city than to its own current climate. In addition, 22% of cities will experience climate conditions that are not currently experienced by any existing major cities,” the researchers explain in a study.

In other words, we are in for a rough ride.

As a general trend, the scientists say, most cities around the planet will see their climates adopt sub-tropical features. Cities in the Northern Hemisphere will be considerably warmer than they are today while cities in the tropics will likely experience more prolonged droughts, more frequent floods and other calamities on a more regular basis.

“We notably predict that Madrid’s climate in 2050 will resemble Marrakech’s climate today, Stockholm will resemble Budapest, London to Barcelona, Moscow to Sofia, Seattle to San Francisco, Tokyo to Changsha,” they write.

Alarmism? Hardly. At least not according to the scientists themselves. They say their model is fairly conservative in its predictions, which should bear up even under an optimistic climate change scenario whereby nations around the planet enact “substantial” climate change mitigation efforts in coming years.

“[A]cross Europe, both summers and winters will get warmer, with average increases of 3.5°C and 4.7°C, respectively,” the researchers predict. “These changes would be equivalent to a city shifting ~1,000 km further south towards the subtropics.”

Record-breaking heatwaves sweeping much of Europe  this summer certainly seems to be an indicator of things to come. In the past 500 years the five hottest summers in Europe have all taken place in this new century, and that’s exempting this current summer. Climate change, experts say, is already remaking the climate of the continent.

Exacerbating the effects of climate change will be the heat island effect whereby certain urban areas are significantly warmer than their surroundings in rural areas as a result of manmade structures.

The challenges facing cities and nations as they come to terms with new climatic conditions will be enormous. “That means there will be new political challenges, new infrastructure challenges, that we have not faced before,” observes Tom Crowther, founder of the eponymous Crowther Lab at the Swiss university, which conducted the research.

“We are absolutely not prepared for this,” he stresses. “Planning for climate change needs to start yesterday. The sooner it starts, the less the impact will be.”

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