The so-called greenhouse effect is essentially the trapping of reflected solar energy (infra-red radiation) by ‘greenhouse gases’. We actually need greenhouse gases in our atmosphere, otherwise the average temperature on earth would be about -18°C and so too cold for life. Unfortunately, in the last 200 years or so, human activities like the burning of fossil fuels have pumped huge amounts of extra greenhouse gas into the atmosphere, enhancing the greenhouse effect and so warming up the planet. Continue reading →

Q: Is there any truth that temperature rose during the three day no fly policy after 9/11 and that vapour trails cause cooling?

A: Yes, in the day time at least. Because the skies were almost entirely free of contrails more energy from the sun was able to reach the earth’s surface, rather than being reflected back towards space by the contrails. This was used by some to argue that air travel actually helped to cool the planet through the reflection of sunlight by contrails. However, this overlooks what happened at night. With no contrails the infrared (heat) energy emitted from the earth’s surface is able to escape much more easily and so the surface is able to cool to a much greater degree. When there are contrails these act like strips of blanket – trapping the radiated heat and keeping the surface temperatures higher. So, when both day and night time temperatures are considered, contrails have a net warming effect on our planet, even before we consider the greenhouse gas emissions that they represent. An interesting recommendation made recently was to restrict night time air travel, and so confine the formation of contrails to the day time – where they have less of a positive climate-forcing effect. For more detailed information see this paper from the European Geophysical Union.

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Given the scale of the problem that we face, it is all too easy to feel powerless. How, without running for political office, can we as individuals make any difference? Surely, cutting greenhouse emissions to the extent required is the job of our governments, industry and big business. The truth though, is that the real power to tackle climate change lies not with Prime Ministers, Presidents or Chief Executives. It is in the hands of the homeowners and the car drivers, the holidaymakers and the shoppers of the world, that the destiny of our planet’s climate truly rests. Continue reading →

Transport

For many of us, our transport emissions are dominated by car-use. Your average 1.3 litre run-around will, in the space of a year, clock up somewhere between 4 and 6 tonnes of greenhouse gas. Drive a gas-guzzling 4-wheel drive though and your emissions can be more than double this. For decades, any advances made in engine efficiency have been undermined by demand for bigger, more powerful cars. Add to this the growth in the number of cars on the road – there are now more cars in the US than people to drive them – and it’s little wonder that cars have come to play such a leading role in human-induced climate change. Continue reading →

Sea-level rise

A warming planet causes sea-levels to rise for two main reasons. First of all there is increased melting of glaciers and ice sheets, whose melt waters continually add to the total volume of the oceans. Secondly, there is thermal expansion of the oceans: as the water warms up it takes up more space. Continue reading →

In 1997, with ever-stronger evidence for an enhanced greenhouse effect driven by human activities, and deepening concern over the impacts the resulting changes in climate might have, over 150 nations came together in Kyoto in Japan to agree the first binding agreement aimed at cutting global greenhouse gas emissions: The Kyoto Protocol. But in 2009 the United Nations Climate Change conference in Copenhagen failed to agree on a binding agreement for all nations on reducing emissions. Continue reading →