New paper predicts “climate departure” years for world’s cities

16 October 2013

For London it’s 2056, for New York, 2047. For Mexico City, Lagos and Mumbai, it’s much earlier.

These are the years by which extreme weather and temperatures will be the new normal, according to a new study.

If true, it would have serious implications for the liveability of buildings and cities in the developed and developing world.

Within 35 years even the coldest dips in temperature will be hotter than anything we’ve seen in the past 150 years, according to a paper published in the journal, Nature.

Based on a "new and massive analysis" of existing climate models, the study claims to show when the world’s cities will experience "climate departure", meaning the point at which their mean annual temperatures break historical records for 11 years in a row.

The paper, by researchers at the University of Hawaii, finds that under a "business-as-usual" scenario – with no reduction in greenhouse gas emissions – huge cities near the equator will experience climate departure in less than 20 years: Lagos and Jakarta in 2029 and Mexico City in 2031.

The authors say that, unless a global mitigation strategy is put in place, by 2050 more than five billion people in developing countries will experience extreme climates, with serious implications for biodiversity, nutrition, water, health, war and economic development.

In the 2040s major American cities such as New York, Washington DC and Los Angeles will face climate extremes, to be joined by European cities such as London, Moscow, Paris and Berlin in the 2050s.

The findings, if true, could have serious implications for the built environment.

Bill Gething, architect and co-author of "Design for Climate Change", published by the RIBA this year, has said that unless buildings are designed to cope with increasing temperatures life will be "unbearable".

"The good news … is that warmer winters will mean overall reductions in the amount of energy needed for heating in winter," he told The Economist. "However, increasing energy costs, the natural variability of weather and the likelihood of more extreme events increasing that variability, mean that we will still need to insulate very well, and it is unlikely that we can reduce the size of heating equipment.

He added: "The bad news is that, over the lifetime of a building, increasing summer temperatures mean that buildings that are bearable now are likely to become unbearable in due course.

People take shelter from record heatwave in a government building in Shaoxing, China in August when temperatures topped 40 degrees C for days. (STR/AFP/Getty Images)

In June New York City Mayor Michael Bloomberg announced a $20bn plan to protect the city from rising sea levels and storm surges following the destruction from Hurricane Sandy last year that cost the city an estimated $19bn in damage and lost economic activity.

The mayor’s proposal would see a network of flood walls, levees, and bulkheads built along the city’s 520-mile coastline.

Heatwaves are already deadly, even in rainy UK.

Research by the London School of Hygiene and Tropical Medicine found that between 540 and 760 deaths could be attributed to the heat during a nine-day hot stretch this past July, The Times reported.

"The results shocked us," said the paper’s lead author, Camilo Mora. "Regardless of the scenario, changes will be coming soon. Within my generation, whatever climate we were used to will be a thing of the past."

Where to avoid

Here is a selection of "climate departure" years for the world’s major cities, according to the paper.

The paper, entitled "The projected timing of climate departure from recent variability," is available here.