So far this year, the world has been about 1.5 degrees warmer than the 20th-century average.

In San Antonio, it’s not just summer temperatures that are rising. Winter temperatures and the number of hot days and warm nights are also increasing, according to a statistical overview in the City of San Antonio’s Sustainability Plan, prepared by climate scientist Katharine Hayhoe.

While actions today can reduce tomorrow’s temperatures, projections show that even if greenhouse gas emissions were completely eliminated today, global temperatures would continue to increase for more than 1,000 years.

San Antonio will kick off its first Climate Action and Adaptation Plan on Dec. 7 – not a moment too soon.

If no effort is made to reduce global greenhouse gas emissions, the Natural Resources Defense Council estimates that the number of deaths in San Antonio related to extremely hot summer days will increase from the current average of two per summer to 50 per summer by the middle of the century.

A groundbreaking study recently published in Science examined the county-level economic impacts of climate change in the United States. The increases in electricity expenditures for cooling, heat-related deaths, and other impacts are expected to result in an annual income reduction of almost 10 percent in Bexar County by the end of the 21st century. Income decreases are expected to be more severe in Atascosa, Medina, and Wilson counties. One of the study’s authors noted that “Texas is the perfect storm” for climate change impacts.

Some northern parts of the U.S., on the other hand, may benefit from climate change. This prompted the headline on the Popular Science magazine website “If you live in the South, climate change could kill your economy.”

Cities are hotter than the surrounding countryside due, in part, to the relative lack of trees and green space. Increasing heat and drought, urban sprawl, and challenges to tree ordinances all work against more trees and green space. In the five years ending in 2006, San Antonio lost 3.4 percent of its tree canopy.

Some cities have increased the amount of green space by installing vegetative roofs –  Toronto, for example, now requires new commercial buildings to have green roofs.

White roof coatings can reduce internal building temperatures by up to 30 percent. The City’s Under 1 Roof program is on the right track, but it needs to be scaled up to make a difference in the city’s environment. New York City’s Cool Roof program estimates that every 2,500 square feet of roof coated with the reflective paint can reduce the city’s carbon footprint by one ton of carbon dioxide.

In the Los Angeles area, a lighter-colored coating on streets has reduced road temperatures by 10-40 degrees, and local residents noticed.

A downtown surface parking lot in Dallas is being converted to the Pacific Plaza Park (with an underground garage) that will help cool the area, absorb rainwater, and increase adjacent property values by an estimated 15 percent.

The “Depave” movement, which started in Portland, Oregon and aims to convert excess pavement into green spaces, now has projects in both U.S. and Canadian cities.

Beyond hot surfaces, vehicles and air conditioners generate measurable levels of heat in cities. One study found that traffic produced between 47 and 62 percent of the heat generated by city residents during the summer in the U.S. cities studied.

In order to keep this from becoming a self-fulfilling prophecy, it is paramount that San Antonio join the efforts of cities and organizations to reduce global greenhouse gas emissions.

City Council’s recent action to support the Paris Climate Accord is the right first step. Following through with a Climate Action Plan is the next.

Bill Barker

Bill Barker, FAICP, is the only professional in San Antonio that is recognized as a Fellow by both the Institute of Transportation Engineers and the American Institute of Certified Planners.