One of the best things about Forensic Science is not just that it works with tiny samples, but that the conclusions drawn are very large. One small speck of DNA can solve a whole case. What’s more, it is tested twice: firstly by other scientists in all the usual ways like conferences, learned journals and many a coffee break chat. Then it goes to court and gets tested again by barristers who, despite whatever their personal defects, have razor sharp minds and can detect any error or illogicality. It’s the ultimate test of the scientific method. Which is actually very easy method to learn. Look very hard at something. Is it real? How does it differ from what you know? What does it let you predict?

Oddly enough, it was this method which provided the clinching proof that humans are causing global warming. As every schoolchild knows, carbon mainly comes in two isotopes: 12C and 13C. And these are being constantly recycled through living things and the atmosphere. Because plants generally like to work with 12C they absorb more of it from the atmosphere. So if you measure the ratio of 13C/12C it’s higher in plants than it is in the atmosphere as a whole. But because of the recycling, the atmospheric level should be stable. Which it was for many thousands of years. But if you start burning lots and lots of plant material, especially in the form of coal, that ratio will change. Which it has since about 1850, as the Industrial Revolution bedded down. Since when the atmospheric 13C/12C ratio has been falling steadily as more and more 12C goes up the chimney. You’re breathing it in too, but that’s another story. We have a link below to the Wiley dummies website, which is always a marvellous source of clear explanation on many topics.

So here’s some questions for those Dog and Duck types who spend too much time swallowing the output of certain TV channels whole.
How much has the 13C/12C ratio changed since 1850? Why has it changed? If it is not caused by burning fossil fuels, what is the alternative explanation? If the effect is cyclic, how long are the cycles? How have they changed in relation to other natural cycles? What other evidence can you offer to make me believe what you say?

We don’t know what answers they will give. But we have noticed that people who start shouting, change the subject or say it’s all conspiracies show that they don’t know what they’re talking about- on any subject.

Isotopes: How Do Scientists Know that Humans Cause Global Warming? By Alecia M. Spooner

By Keir Hartley

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