London’s climate ‘will resemble Barcelona’s by 2050,’ study reveals

The first study of its kind aims to bring the reality of climate change away from data and compares the futures that await iconic cities around the world

By Simon Ingram
Published 12 Jul 2019, 15:52 BST
London, July 5th 2018: Londoners watch the sunset from Greenwich park during a summer heatwave in ...
London, July 5th 2018: Londoners watch the sunset from Greenwich park during a summer heatwave in the capital. Records released by the Met Office showed 2018 to be the joint hottest year on record for the UK, with a year-round average of 15.8 degrees centigrade. The summer high was 35.3 degrees centigrade.
Photograph by Guy Corbishley, Alamy Live News

In a little over 30 years, Londoners will swelter in the summer much like Barcelona does today. Edinburgh’s climate will resemble Paris’s, while Cardiff’s will align with conditions currently commonplace in Uraguay’s capital, Montevideo. Barcelona, meanwhile will experience the aridity of Adeleide, Madrid will feel like Marrakesh, and Milan like Dallas, Texas.   

This is the near-future world of a study authored by Zurich's Crowther Lab, and published this week in science journal PLOS One. The work seeks to illuminate the reality of global climate shifts by aligning the projected future conditions of a city with the current climate of another elsewhere in the world. The study authors hope the result is a scenario easier to visualise than ‘data and facts alone’.

“By focussing the outputs of this research on ‘major’ (highly populated) cities, we hope that it enables people to visualise their own climate future," says Thomas Elliott, one of the study's authors, in an email. "Our aim is to make this research more tangible, and by doing so, inspire people to act.”

And however much the residents of London or Cardiff might initially welcome the prospect of a Mediterranean or South American climate, the implications make for a grim reality – with drought, the discomfort of frequent heatwaves such as those experienced across Europe already this summer, turbulent weather systems and the ecological impact of rising temperatures. At the extremes, the predicted conditions bring with them issues as yet unseen by the cities in question, such as acute water shortages. 

Reactions in London during the hottest heatwave on record (38.1 deg C, 2003) – and a sign in Barcelona explaining why the fountain is dry in a similar local heatwave. Scenes like the left could resemble the latter if predictions of the new study are realised.
Photograph by Percy Ryall, Alamy left Kim Karpeles, Alamy right

Major Populations, Major Change

The data pool comprised 520 international cities – each either an administrative capital or home to a population over a million – selected from a database compiled by the Oakridge National Laboratory. These were appended to climate records for each in the form of 19 bioclimatic variables, which according to the study captured various conditions at various times.

"Broadly we split them into three types; ’temperature’, 'precipitation’, and ‘drought’," continues Elliott. "Then we identified for each city in each year, the warmest month, the driest month, the wettest month, and so on."  

To understand how this data would change over the next few decades, this data was then run through a series of future models used in ecological studies and weather prediction – including one used by the Met Office's Hadley Centre. The final critical ingredient: determining the evolution of the global climate with human influences considered. With carbon reduction targets such as the UK’s zero-by-2050 policy now law, how will that effect any future change? There’s a model for that, too.

Map from the study authors showing the distribution of the cities sampled, coloured to correspond with the projected rise in seasonal temperature.
Photograph by Crowther Lab, Bastin et al, Plos One 2019

Representative Concentration Pathway 4.5 (RCP 4.5) is acknowledged as a ‘stabilisation scenario’ for the changing of the earth’s climate – and a best case one, as it factors in the proactive measures taken to improve the environment as well as our negative effect on it. Created by the World Climate Research Programme’s Coupled Model Intercompassion Project, RCP 4.5 allows for a levelling of radiative forcing (human-catalysed warming) before 2100 and the deployment of technology and plans for reducing emissions. 

"In general RCP 4.5 is an optimistic scenario," says Elliott. "As shown in the latest IPCC report it is unlikely that we will achieve it given our countinued fossil fuel emissions per year and our failure to effectively address biodiversity loss on a large scale."

Even using this conservative model, 77% of the cities sampled consistently shifted to that resembling another – London to Barcelona, Edinburgh to Paris, as well as other notable shifts as Madrid to Marrakesh, Seattle to San Francisco, and Stockholm to Budapest.

For each city the study revealed an 'equivalent' climate city, along with figures for an average temperature rise, and for temperature rise in both the warmest month and the coldest month. 

British cities sampled were Leeds, Edinburgh, Belfast, Cardiff, Manchester, Birmingham and London. Manchester displayed the most dramatic increase, with an average annual temperature uplift of 2.9 degrees centigrade by 2050. This figure incorporates a rise of 6.2 degrees centigrade in the hottest month, and 3 degrees centigrade in the coldest. Its 2050 climate was aligned with that of present day Montevideo, the sub-tropical capital of Uruguay, which has an average annual temperature of 16.3 deg C.    

The general trend observed by the authors was that the climate of most cities in the northern hemisphere would resemble that of cities roughly 1000 miles south, representing a shift towards sub-tropical conditions. As for the fate of the cities currently in the sub tropics and tropics: the city analogues revealed that these would in turn evolve into drier, more arid conditions.

However, 22% of the cities sampled delivered a negative match on a future equivalent, meaning they would enter a ‘novel’ climate – that is to say, one not experienced by any other city in the study. In effect, any major city in the world. 

Surely a concerning result for what is essentially a best-case scenario study.  

Portuguese students chant and hoist placards in front of the Portuguese Parliament building. Cities around the world were the scene of unprecedented climate change activism during 2019.
Photograph by Photograph Horacio Villalobos, Corbis/Getty Images

“22% of the cities sampled delivered a negative match on a future equivalent, meaning they would enter a ‘novel’ climate. That is to say, one not experienced by any other city in the study. In effect, any major city in the world.”

Relatability of Result

Chief amongst the study’s motives is the idea of a relatable scenario. It states that hard data does ‘not inspire humans to change their beliefs or acts’ – and that there is a discord, or ‘consensus gap’ between scientific findings and public opinion. Hence the cities model, and the deployment of a simple website allowing users to see how their own city will fare.

Align statistically similar conditions separated by location and time and you are using ‘analogues’ – an idea that isn't new, but is proving to be effective in communicating with a wider public on issues typically drenched in technical vocabulary. 

Stephen Blenkisop is a Senior Researcher at Newcastle University, and the Tyndall Centre for Climate Change Research. He was not involved in the study but says is he is familiar with analogues and their use. “I’d say that as cities will face significant impacts associated with global warming - from heat waves to flash flooding – the use of city analogues presents a relatable way for the public and decision-makers to understand the broad ways in which their local climate is likely to respond," he told National Geographic UK in an email. "This knowledge can provide a first step in thinking about how cities will need to adapt to these challenges in the future."

"We hope this gives people a better grasp of how climate change will effect them in their lifetime," continues Thomas Elliott, “and encourages them to engage with their governments, with business and within their communities to address climate change and biodiversity loss.” 


Photo Gallery: See Pictures of Extreme Weather Around the World


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