What’s up with this heatwave?

Photo Credit: Digging for Fire

Something completely out of the ordinary happened this week in London. It was hot. And sunny. For a week straight. Next up: hell will freeze over and donkeys will fly.

In fact, it was too hot. While houses in usually much hotter countries are built to handle this kind of heat, British houses are designed to keep heat in during the winter. Also, air conditioning is very rare in the UK (unlike in places like the US where it is practically ubiquitous), leaving most people ill-equipped to deal with the heat. As the temperature rose to historical highs, my productivity reached historical lows (as you might have noticed by the distinct lack of articles this week).

Of course, the unusual heat was big news, with some papers claiming that up to 750 people died. But is this true? And what’s a heatwave anyway?

The Times reported that the estimates “death toll for the first nine days of the heatwave [is] between 540 and 760 people in England alone”. An excellent Guardian article (from the column “Reality Check”, which I highly recommend reading regularly), debunks these claims quite thoroughly. It points out that “heatwave” and “sun” are not listed as causes of death in national statistics. And that death statistics are usually delayed (for example 2012 statistics were just released a week ago).

There does not appear to be a correlation between deaths and spikes in sunshine and, in fact, people tend to die in much higher numbers during the winter months. (Read the full article here).

That said, sunstroke and skin cancer are real, and precautions should always be taken. Wear sun cream, a hat and protective clothing. Skin cancer rates are higher in countries like Australia, which get a lot of sunshine. And, even though it is one of the most survivable forms of cancer, it would really suck to get it. So be careful.

What’s a heatwave anyway?

A heat wave is defined as:

A period of abnormally and uncomfortably hot and usually humid weather.

To be a heat wave such a period should last at least one day, but conventionally it lasts from several days to several weeks. In 1900, A. T. Burrows more rigidly defined a “hot wave” as a spell of three or more days on each of which the maximum shade temperature reaches or exceeds 90°F [32°C]. More realistically, the comfort criteria for any one region are dependent upon the normal conditions of that region.

-Meteorology Glossary, American Meteorological Society

Heat waves occur when high pressure at altitude sinks hot air towards the surface. During the summer, weather patterns change more slowly, so this high pressure area tends to stay on the same spot for longer than in the winter.

High pressure traps hot air underneath, creating a heat wave – Picture by the US National Weather Service

Because of the pressure, the hot air is trapped. This air cannot rise from the surface and form convection currents. Without convection currents you have no cumulus clouds (which are convective clouds) and therefore, little chance of rain.

As this high pressure cap stays put, the temperatures get higher and higher.

-Francesco (follow me on twitter)

References and further reading

Feature image by Minghong

  • Santeri Lohi

    I’m sick of the term ”heatwave” as if it’s some national crisis. Everything has to be a crisis. WARNING! HEATWAVE! NATURAL DISASTER!

    How about just: “it’s relatively hot, drink water.”

    • http://piecubed.wordpress.com piecubed

      The media is always ready to scare people to get more audience.