Friday, 8 August 2008

Weather, Smog and the Beijing Olympics

Since Henry Des Voeux allegedly invented the term Smog (an amalgamation of smoke and fog) in 1905, it hasn’t been in the news as much in the UK since the 1950s. Perhaps the most infamous being the Great Smog of London in 1952, which is said to have resulted in over 12,000 deaths, and led of course to the introduction of the Clean Air Act in 1956. Those kinds of smogs were the result of heavy coal burning in factories and homes, but modern day smogs are a little different.

These days smogs are more often a result of industry and transport emissions, and have two parts to them. The first are emissions of the Oxides of Nitrogen, Volatile Organic Compounds and Carbon Monoxide; the sort of thing Councils measure in those road side cabins that you might have seen. These are the primary pollutants, but there are also secondary pollutants caused as a result of sunlight reacting with the primary pollutants to create Ozone at ground level. Ozone is good for us up in the atmosphere because it protects us from harmful sunlight, but down at ground level it’s bad for us to breath. All of these primary and secondary pollutants combine to give us what we call photochemical smogs.

The big cities of the world do suffer from these kinds of smogs, like Mexico City, LA, and of course as we’ve seen on the news recently Beijing. And it’s not good news for those with breathing difficulty or those athletes who have to compete in those conditions.

It’s not the only challenges that athletes will face. August is one of the warmest and most humid months in Beijing with temperatures rising to 30oC and humidity as high as 75%. This can have two effects. Sweating cools us down because when the sweat evaporates from the skin it uses heat to turn the liquid into a gas and leaves the skins surface much cooler – we’ve all experienced that when we’ve got out of water before we’ve had the time to dry off. The high humidity reduces or can even prevent the sweat from evaporating. We sweat more and then end up very dehydrated. The second problem is that as our body temperature rises we push more of our blood towards the skin surface where it has a chance to cool, and away from muscles and body organs and we start to feel tired – and in extreme cases can lead to heatstroke.

We can’t do much about the temperature and humidity, but what about the smog. Well unfortunately that’s affected by the weather as well. Taking cars off the road and closing factories to reduce the emissions will certainly help, but if they don’t have the right kind of weather, then it will take a while for the smog that’s there to disperse. At this time of year when the upper parts of the atmosphere are warm then this can stop air rising and taking pollution away – it acts like a kind of lid to trap in the pollution. On a positive note though, because of the high temperatures and humidity there is a chance of thunderstorms which will help to wash out the pollutants.

Good luck to China for a great games and best of luck to Team GB – bring back lots of medals guys. By the way when are they going to make weather forecasting an Olympic sport!

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