Mankind is destroying the planet; human life, if it carries on the way it is, is unsustainable. That is what the media, our national governments and our thermometers all tell us on a regular basis – and they are most probably correct, if you believe many of the world’s scientists. We need to be greener, they all say. We should all start fitting solar panels to our houses and recycling used goods, and we should certainly be cutting down on our use of fossil fuels, our CO2 outputs and our use of cars. Oh, and air travel. Planes are also terrible pollutants, they say.