Urban nights are warming

The purpose of my putting my thoughts to paper, regarding the ever changing weather patterns is to provoke thought. I am not a scientist nor a climatologist but simply a concerned layman. What I am posting here are my observations over a lifetime of some 66 years.

Yesterday I talked about asphalt and its ability to absorb and retain heat. As a roofing and restoration consultant I have performed a variety of infrared scans on industrial and commercial roofs. To do a scan one must be prepared to work long into the night. Why? Because it is imperative to have differential temperatures between the affected area and the unaffected area. In order to do this the roof surface must be allowed to cool since the wet areas will retain heat longer than the dry areas.

Typical IR scan showing thermal variances

Up until the mid to late nineties 4 ply felt and asphalt roofing was the primary waterproofing application. Eventually hybrids gained popularity and today we see many single ply and two ply roof membranes. Surprisingly the 4 ply system remains the number one choice of roofers and owners.

A typical 4 ply roof being installed

At the left in this photo we see pea gravel surfacing that is used as a protective cover for the membrane. This gravel also will absorb and retain heat long into the night. As we expand and develop industrial parks, plaza's, malls and institutional buildings we increase heat absorption in the materials. While not a major problem during daylight hours it does have a negative effect at nighttime.

The latest trend in roofing is to apply a hybrid membrane with a reflective surface or colour. This has two essential benefits to the environment, during the day the roof surface is cooler with less heat being transmitted to the interior of the structure and less heat emission after sunset. Both of which reduce energy costs as well.

This phenomena would be more prevalent in urban areas and while not necessarily directly related to global warming it would influence weather patterns to some extent.

There is no scientific basis to my comments however, as I sit here typing away I can't help but wonder why the naysayers do not realize that the shear number of people in the World and their constant abuse of the environment does affect the climate.