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Table of Contents You’ve heard of counting carbs. This book is about counting carbon. It’s not the health of your body that is the object of our interest this time, but the health of the planet. Carbon dioxide is the main gas responsible for global warming, and humans are producing 25 billion tonnes of the stuff every year, raising the temperature of the planet to dangerous levels. This book will help you bring down your personal contribution to this rather daunting problem. According to the government’s chief scientist Sir David King, global warming is the greatest problem facing humanity. It’s therefore a bit of a tall order to solve it all on your own. But if enough people begin to count and reduce their carbon, the rate of climate change can be slowed down dramatically. This could save countless species from extinction, as animals like the polar bear and Bengal tiger will have nowhere to go as the world warms. It could also save the lives of the millions of people who are at risk from rising seas in low-lying areas. But if we don’t act, vast swathes of the globe could be rendered uninhabitable because of flood, drought and searing heatwaves. So by ceasing to be part of the problem and instead becoming part of the solution, you can join a growing movement to cut back humanity’s carbon emissions before it is too late – and many scientists suggest that the atmosphere’s ‘tipping point’ will come within the next decade, giving us no time to dither before making dramatic cutbacks. The lifestyle change that this implies doesn’t necessarily mean misery and sacrifice: low-carbon living means that we should all end up fitter and healthier too. So maybe – the planet aside – counting carbs and counting carbon aren’t so different after all. THE GREENHOUSE EFFECT Contrary to what you might have heard, the greenhouse effect is not all bad. Without the heat-trapping effect of certain gases, the average temperature of the planet would be a decidedly chilly -18°C. Nor is it a new discovery. The Irish physicist John Tyndall was the first to realize, back in 1859, that without greenhouse gases in the atmosphere, things would quickly turn unpleasantly cold. As he wrote (a little melodramatically), without these heat-trapping gases, ‘the warmth of our fields and gardens would pour itself unrequited into space, and the sun would rise upon an island held fast in the iron grip of frost’. (Tyndall did well on the lecture circuit.) Tyndall correctly identified that the two most common gases in the air, nitrogen and oxygen, are transparent to heat radiation. Instead, it is gases present in much smaller quantities – water vapour, carbon dioxide, methane and others – which have the heat-trapping effect. No one disputes this ‘natural greenhouse effect’, as it can be demonstrated easily enough in the laboratory. The arguments (for climate change is nothing if not controversial) come later. Not all greenhouse gases are born equal. Carbon dioxide gets most attention because it is the most abundant, and lasts a long time in the atmosphere. Water vapour is also a greenhouse gas, but its emissions are more or less irrelevant because it condenses out as rain in a matter of hours or days. (The exception to this is water vapour emitted high in the atmosphere by aircraft, where it can have a longer-term warming effect.) The table below details the different gases and their ability to trap heat – their ‘global warming potentials’ – as well as their atmospheric lifetimes.
GREENHOUSE GASES
‘Global warming potential’ means the potential each gas has to trap heat over a given period of time, just as different ratings are applied to measure the heat-trapping strength of different duvets on a bed! The greenhouse effect can also be observed on other planets in the solar system. Venus has a hotter surface temperature than Mercury, despite being much further away from the sun. Because the Venusian atmosphere is almost entirely composed of carbon dioxide, this gives it a phenomenally strong greenhouse effect – keeping surface temperatures at 460°C, hot enough to melt lead. All of this would interest no one other than chemists and astronomers if the amounts of these gases in the earth’s atmosphere were to stay fixed. From the Industrial Revolution, humans began exploiting fossil fuels – coal, then oil and gas – for energy. These fossil fuels burn to produce carbon dioxide, which then accumulates in the atmosphere over the decades and centuries. In 1750 there were 278 parts per million (ppm) of carbon dioxide in the earth’s atmosphere. Now that figure has risen to 380ppm, and it is continuing to rise at 1.5 to 2ppm per year. Methane levels have risen from 700 to 1745 parts per billion, while nitrous oxide has jumped from 270 to 314ppb. The other gases – CFCs, HFCs and SF6 – are entirely products of the industrial age, so did not exist in 1750. But now that they do, many will be with us for a very long time, as the right-hand column of the table on page 9 shows. Put these changes in a geological context, and it all begins to sound a bit scary. Carbon dioxide levels haven’t been this high on earth for millions of years. The temperature of the planet rose and fell with the cycles of the ice ages, but during the whole time carbon dioxide levels were lower than they are now. But as the graph on page 12 shows, temperature and carbon dioxide shadow each other very closely over the long term, suggesting that our increase in CO2 will indeed be followed by a temperature increase. WHAT ARE FOSSIL FUELS? Fossil fuels are often termed ‘buried sunshine’, because, in essence, they represent energy captured from the sun by photosynthesis in ancient plants. By using fossil fuels, humans are getting an effective Tip: If you think about it, all the energy humans have ever used has come from the sun. Cavemen burned wood in fires for heat and cooking, but the trees it came from used the sun’s energy.
