About four years ago I remember watching a documentary (an episode of Horizon I think) which talked about climate change and how mass air travel actually played a role in global warming, or as it turns out, global cooling.
If you go outside and look up then (normally) you’ll see the unmistakable trails that airplanes leave behind (contrails or condensation trails – I had to look that up). In case you’re wondering what it is, the hot exhaust gases of the engine cool the surrounding air and create tiny water droplets, forming artificial clouds.
The point of the programme though was that while these artificial clouds don’t have much of an effect on their own, in big enough numbers, they do. After 9/11, all air traffic in the USA was grounded for three days which meant that there were no contrails. What scientists then measured was that temperatures during those days rose by 1.8ºC.
The effect that the scientists found was that the contrails, in their massive numbers, had been reflecting sunlight and heat away from the earth, helping to cool the earth. Their absence made temperatures rise and given the massive amounts of CO2 that planes pump into the atmosphere, the irony certainly isn’t lost on me. [see Wikipedia's article on contrails]
The relevancy of this of course is that for nearly a week, we’ve experienced something rather similar here in Europe. So it’ll be interesting to see if something similar happened for us. I for one know that I had a brilliantly sunny weekend in Maastricht, I wonder how many other people enjoyed the weather?
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