COLUMBUS, Ohio (WCMH) — Heat islands are defined as urbanized areas that are subjected to higher temperatures compared to the outer suburbs and countryside. Buildings and roads absorb more heat than natural surfaces and re-emit energy from the sun, typically raising temperatures several degrees higher than in outlying areas.

Urban infrastructure and land-use activities influence local microclimates. The City of Columbus is one of 16 metropolitan areas participating in a heat mapping project funded by the National Oceanic and Atmospheric Administration (NOAA).

In the past decade (2011-2020), the average winter temperature (December-February) in Columbus was 3.8 degrees Fahrenheit warmer compared to the period 1961-1970. During the 60-year interval, summer (June-August) averaged 1.6 degrees higher, and similar increases were observed in the spring (1.8 degrees) and autumn (1.3 degrees) seasons in recent years in relation to the mid-20th century averages.

The reasons for the warming are complex, and part of a regional trend in the Midwest and much of the eastern United States.

Heavy rainfall events increased 42 percent since 1958, linked to a warmer atmosphere and higher water temperatures (Gulf of Mexico, Atlantic and Pacific oceans), resulting in more moisture available for storm systems. Subtle shifts in the prevailing wind patterns at the surface and aloft (jet stream) factor in the observed climate change.

NOAA records indicate that July 2022 established a record for overnight warmth nationally, edging out July 2011 in the dataset that covers the past 128 years. The average nighttime minimum temperatures (63.6 degrees) exceeded the 20th-century average by more than 3 degrees. In the past 30 years, nighttime low temperatures have risen 2.1 degrees in the U.S., slightly ahead of daytime highs (1.9 degrees).

Scientists from the Ohio State University’s Byrd Polar and Climate Research Center, Franklin County Public Health, Franklin County Soil and Water Conservation District, the Mid-Ohio Regional Planning Commission (MORPC), and local environmental groups aided in the study.

“Our 200 volunteers will be going through the city with these sensors on them,” said Columbus GreenSpot Coordinator David Celebrezze. “The sensor picks up heat and humidity.”

A series of 1-minute readings were recorded while the instruments were operating. Driving around in vehicles, the volunteers fanned out across the city along designated routes during three one-hour periods on Aug. 12.

In addition to temperature and humidity, the sensors also picked up pollution (particulate or soot) in the air. The data collected from the project will take a few months to analyze.

“The key to the Columbus heat island study — the sunny day and the type of land cover,” said Ohio State University climate scientist Geddy Davis. “Pavement, for example, absorbs more incoming solar radiation than compared to natural covers like grass or even the shade under this tree.”

Urban heat islands significantly impact the health of people and wildlife and add to the load on the electric grid. Dangerously high heat and humidity was experienced in the Columbus area on June 14, when the dew point, a measure of the amount of moisture in the air, reached 84 degrees at the end of the evening rush hour, pushing the heat index to a record high of 117 degrees.

The excess heat lingering into the night raises numerous health risks. Heat mortality exceeds all other weather-related impacts, with an average of more than 700 fatalities in the U.S. each year, according to the Centers for Disease Control and Prevention, likely an undercount due to indirect deaths from exposure to heat coupled with high humidity.

The City’s Sustainable Columbus program outline stated the data “will inform implementation of the community-wide Columbus Climate Action Plan, particularly around imparting environmental justice and building climate resiliency.” The goal is to help determine what actions are needed to create a “regional climate hazards alert system” and a “network of resiliency hubs,” coupled with tree planting to provide more shade.  

“We will then be able to focus the city’s tree initiative programs on communities that are more impacted by heat, planting trees,” said Micah Wolf with the environmental sciences department at Ohio State University.

Urban heat island studies focus on ways to keep homes and neighborhoods cooler where natural vegetation is presently minimal. Planting more trees helps filter air pollution and puts out water and oxygen while removing carbon dioxide, a greenhouse gas that absorbs heat.

Heat-related illness includes heat exhaustion and heat stroke, potentially life-threatening cardiac and pulmonary symptoms often triggered by dehydration.