By Dr. John J. Hidore

“When it seems unusually warm someplace there is often a tendency to describe the weather as a heat wave, but it is very hard to define a heat wave.”

Summer Temperatures in Khartoum Sudan

August 13, 2015—Mid-summer temperatures in the northern hemisphere sometimes soar. For instance, I had the privilege of living in Khartoum, Sudan where it gets extremely hot in summer. It got hot enough on some days that the oil on the streets seemed to essentially boil. Driving along in a car, the sound of the tires bursting bubbles in the oil sounded like pouring milk on Rice Krispy’s! While in Sudan I drove a Volkswagen with an air cooled engine. At times, when arriving home and turning off the engine, it continued to run as the engine was so hot it continued to ignite fuel. This is what the locals referred to as dieseling. One day when I parked the car continued to run so I left it and went indoors. I came out a little later and it was still running. I finally put a wet cloth over the air intake to get it to stop. This was considered just summer weather and not unusual.

The Nafud Desert and Death Valley

On another occasion I was working in the Nafud Desert near Al Hafuf in Saudi Arabia. It was June–and hot! One day we went out about dusk to work. There was a thermometer in an instrument shelter that registered the maximum temperature for the day. The markings on it went to 120 degrees F (49 degrees C)! The mercury was above the highest mark but we estimated it at 124 degrees F (51 degrees C). It was not considered as part of a heat wave, just hot! I must say we did not go out during the hottest part of the day. Until recently the highest official temperature yet recorded was 132 degrees F (55.6 degrees C) in North Africa. The highest recorded in the United States was in Death Valley and it is now set at 134 degrees F (56.5 degrees C), making it the highest worldwide temperature yet recorded.

Defining Heat Waves

When it seems unusually warm someplace there is often a tendency to describe the weather as a heat wave, but it is very hard to define a heat wave. The reason is simple. Normal summer high temperatures vary greatly from place to place. So what would be defined as a heat wave in one location would not be appropriate for another location, perhaps a location very near. An adequate definition might be, “A heat wave is an unusually warm or hot period lasting for days or perhaps weeks.” We associate them with summer, but by this definition they can actually occur at any season. At least one country makes a clear definition of a heat wave and that is Pakistan. India defines heat waves and uses different temperatures in different parts of the country to establish what constitutes a heat wave. In the plains regions temperatures above 40 degrees C (104 degrees F) constitute a heat wave. They also define a severe heat wave for this region as experiencing temperatures over 46 degrees C (114.8 degrees F).

A deadly heat wave strikes Europe

Some heat waves have become deadly. Perhaps the most deadly heat wave of the 21st Century was that which occurred in Europe in August of 2003. Temperatures in France reached as much as 40°C (104 degreesF) and remained exceptionally high for two weeks, resulting in nearly 15,000 heat-related deaths in that country alone. The death toll over Europe reached 35,000 at least and there may have been as high as 50,000 heat-related deaths. A large contributing factor in the high death toll was warmer nighttime temperatures. Nighttime temperatures were much warmer than normal. As a result people without air conditioning could not cool down during the night. The heat stress accumulated over time. The extreme heat waves also can devastate agriculture. In Europe the heat wave of 2003 temperatures averaged 5.5°C (10°F) above normal. In Italy corn yields dropped 36% below average. In France fruit yields fell 25% and wine production 10%. Heat also affects the rate of pollination of plants.

Asian heat waves of 2015

This year a May heat wave in India claimed at least 2,500 lives. Heat waves are fairly frequent in India but this was the greatest loss of life from a heat wave in over 30 years. Extremely high temperatures were reached in cities scattered over the country. Power outages were wide spread as a result of high demand for air conditioning. The city of Khammam recorded the highest temperature ever recorded there at 48 degrees C(118.4 degreesF). Other high temperatures that were recorded were:

Allahabad 47.8 degrees C (118 degrees F)
Delhi 45.5 degrees C (113.9 degrees F)
Hyderabad 46 degrees C (115 degrees F)
Jharsuguda 45.4 degrees C (113.7 degrees F)

In June the deadliest heat wave known to have occurred in Pakistan took place in the southern part of the country near Karachi. The death toll is unknown for certain but may have reached more than 1000. It was followed by several weeks of the most severe heat wave ever to strike India. The heat wave struck during the month of Ramadan which made the impact of the event more severe than it might have been. Unfortunately, city services were not in condition to cope with the heat.

As the planet warms it can be predicted that: (1) new record high temperatures will be set for the planet and (2) there will be more severe heat waves. They will become hotter, more frequent, last longer, and occur in more varied places. As cities grow larger in area and population they will experience increasing heat waves.

These are the realities that are taking place as our planet warms!

The facts about climate change