Urban Heat Island Danger

Fidelity Street is already an urban heat island:  This begins with the buildings, parking lots, and air conditioners at Town Hall, the gym, and Inara Court and ends with these structures at Hillmont, Westwood Cemetery, and 400 Davie Road.  We are surely the only residential heat island of this size and intensity in Carrboro.  This condition will be exacerbated if the cemetery is doubled in size to consume our meadow.

The 1st draft of the comprehensive plan notes that “From 2000 to 2009, extreme heat was the leading cause of weather-related deaths in the U.S. Extreme heat degrades air quality.”  On August 14 the surface temperature of a tombstone after midnight was 96˚.  The ability of our meadow to cool and clean our air will be degraded by putting cemetery structures and more tombstones into this natural space.  As the climate warms and elders upstairs in Hillmont across the street are less able to afford air conditioning, during heat waves their lives will be threatened overnight when their bodies cannot cool down.  The 1st draft plan says the Town should protect maginalized and vulnerable populations from the effects of global warming.

The awareness of the dangers to public health posed by urban heat islands is now only at the level of awareness in the 1980s of the problems posed by storm water runoff.  Atlanta, Durham, and Chapel Hill have been studying this problem with surveys. Here is the heap map for Durham featured in the 8/4/21 issue of the Indy:

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The Atlanta survey was featured in piece on NBC News with Lester Holt on September 20 and the Durham survey was featured in the feature article “Hot Zones” in the Indy on August 4.  Carrboro needs to catch up.

On the night of August 14 the surface temperature of one Westwood tombstone was still 96˚ at 12:30am, following an overall Carrboro high temperature of 96˚ that afternoon. The overall air temperature in town was 81˚ at 12:30am. So the tombstones contribute more air heating beyond the heating by the cemetery’s driveways. In fact, at 3:00pm on September 14 (when the high temperature was 90˚) the air temperature in front of that tombstone was over 2˚ warmer than the air temperature 50 yards away in the middle of the adjacent meadow.
At that time the average air temperature at three places in the UHI formed by Town Hall, the gym, and Inara Court averaged 2.5˚ hotter than Carrboro’s overall temperature. So on a sunny day the tombstones in the cemetery (and its driveways) can heat up Carrboro’s air nearly as much as the parking lots in front of the gym, next to Town Hall, and in Inara Court! Introducing more structures, pavement, and tombstones into the meadow will reduce its current cooling effect for Hillmont, 400 Davie Road, and the rest of Fidelity Street.

Increases in temperatures that sound relatively small are actually a big deal when climate change and UHIs are studied.  The anticipated global increase of 3˚F to 5˚F anticipated by 2050 is considered not only a threat to the global environment but also a dangerous escalation of the health risks of excessive heat.  But we already have differences as large as this between the privileged exclusivity-zoned neighborhoods north of Main Street and the environmentally responsible multi-family housing neighborhoods south of Main Street!

In August Professor Angel Hsu of the UNC Public Policy department conducted a study of UHIs for the town of Chapel Hill.  On the post-summer day of September 14 this author used equipment borrowed from her to take some comparative readings of temperatures in Carrboro.  The high temperature that day for Carrboro overall was only 90˚, or that of a merely-average summer day.  The lengths of day-to-night ratio on the 14th was only 52:48, whereas in early July when the temperatures can reach 102˚ (currently, before global warming) the day-to-night ratio is much higher, at 58:42.  September 14 was a breezy day, which would reduce the temperature differential between the two sides of town.  So the picture painted by the following numbers would be much worse if they had been measured on one of our hotter July days which had both still air and a shorter night.  The nighttime temperatures would become dangerous if there were several such days in a row since most heat-related deaths among the elderly are caused by a sequence of several days wherein the nighttime temperatures do not drop below 80˚.  On August 13 this year the overall Carrboro temperature was still 81˚ at 12:30am.

At 3:00pm on September 14 the overall Carrboro temperature was slightly above 90˚.  Many of the bedroom windows in multi-family housing overlook parking lots.  At that time the air temperatures in Inara Court and in parking lots in Village Square and Hillmont Apartments were 92.7˚, 94.0˚, and 92.5˚, averaging 93.0˚.  At that time the air temperatures by two curbside mailboxes on Blueridge (near the intersection of Greensboro & Hillsborough) and by two mailboxes on Carol (near James) were  89.7˚, 89.0˚, 87.9˚, and 88.6˚, averaging 88.8˚.  So the temperatures beneath the windows of some apartments on the southside are around 4˚ hotter than along the edges of the shady streets (and probably even a bit hotter when compared with what the bedroom windows on Blueridge and Elm overlook).  The biggest difference was 6˚.  There were still significant differences at 10:30pm, in spite of much breeze that day (and a relatively early sunset time of 7:24).  Then the parking lots were around 2.5˚ warmer than the edges of the shady streets, with the largest difference being 4.5˚.

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