Average Temperatures in Cities Forecast to Spike as Climate Change Worsens

Climate scientists predict temperatures in Earth’s cities — which will be home to 70% of the planet’s residents by 2050 — could spike by nearly 8 degrees.

People cool down in the fountains of the Trocadero gardens in Paris, Thursday July 25, 2019, when a new all-time high temperature of 42.6 degrees Celsius (108.7 F) hit the French capital. (AP Photo/Rafael Yaghobzadeh)

(CN) — Urban climate modeling developed by U.S.-based researchers found the planet’s cities — home to more than half of the global population — could see dramatic temperature spikes by the century’s end if carbon emissions aren’t sufficiently curbed, according to a study released Monday.

Climate change has altered ecosystems worldwide, pushed regions into deeper drought spells and wreaked havoc in communities. 

Multiple species and their natural environments have been disrupted by climate change, and cities — which are projected to hold 70% of Earth’s population by 2050 — have experienced one element of it most acutely: dramatic spikes in average surface temperatures.

Urban environments, with their massive concentrations of heat-trapping concrete and asphalt, tend to be warmer than rural or suburban areas. The statistical forecasting model predicts the problem will only get worse for urban areas if climate change goes unmitigated.

Researcher Lei Zhao of the University of Illinois and colleagues considered the unique features of urban areas when developing their climate change predictions. The team built a statistical model that uses global climate data to forecast urban temperatures based on scenarios where carbon emissions are high or at intermediate levels, according to the study published in the journal Nature Climate Change

The model produced projections of temperature and relative humidity for individual cities around the world, which currently occupy less than 3% of Earth’s total surface area.

Under high emission scenarios, cities in the U.S., Middle East, northern Central Asia, inland South America and Africa would see temperature increases of more than 7 degrees Fahrenheit, or 4 degrees Celsius by 2100, according to the study titled “Global multi-model projections of local urban climates.”

“This confirms the crucial role of mitigating non-local greenhouse gas emissions for local-scale urban temperature benefits,” the study said. “Despite a substantially mitigated urban warming globally and fewer ‘stippled’ areas, the models still agree that a large number of cities (especially at nighttime) will experience warming of more than 1.5 [degrees Celsius], the target set by the Paris Agreement.”

The authors found that average temperatures in urban regions across the globe would spike by “1.9 degree Celsius with intermediate emissions and 4.4 degrees Celsius with high emissions,” according to a statement released with the study, or between about 3.4 and 7.9 degrees Fahrenheit.

But not all cities will experience the negative effects of climate change at the same scale or point in time.

“For example, observational evidence suggests that the city of Anchorage in Alaska is experiencing climate change at twice the rate of cities at mid-latitudes,” the study authors wrote.

According to the forecast model, the world’s urban environments could also experience a near universal decrease in overall humidity by 2100.

The finding, which researchers hope will be useful to urban planners and city officials worldwide, suggests that expanding cities’ tree canopies and other vegetation could be useful adaptations to climate change, according to the study. 

The study also advises global leaders to invest in “green infrastructure” to reduce or eliminate the impact of urban heat island effect, which occurs when city infrastructure absorbs and traps heat that would normally escape in less crowded areas. 

“Despite being less effective in wetter cities, green infrastructure would still provide cooling and, in addition, more shading (by trees). Under climate change, the potential evaporative cooling efficiency from green infrastructure is projected to increase in most of the urban areas globally except some coastal cities, with a global average increase of 16.6% by the end of the century,” the study said. 

“Our results suggest that efforts to increase urban green infrastructure would potentially produce more effective cooling on a large scale in future warmer climates.”

Researchers did not immediately respond to a request for comment on the study.

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