Climate Change and what trees are made from

I noticed this week that the New Scientist has a one page advert from the Spectator magazine, announcing an upcoming debate on Climate Change. It is introduced as follows:

“The number of people in the UK who do not believe in global warming has doubled in the last two years, according to a poll from the office of national statistics. Does this represent the common sense of a British public who can see the claims of the climate alarmists dissolve before their eyes?”



It’s an interesting choice of phrase, common sense. Common sense is a very important skill to have. It’s very useful when considering what a door-to-door salesman is telling you, or what is being loudly trumpeted on a web page advert. Common sense tells you that the news that you have been randomly picked (again!) for an amazing special offer is unlikely to be luck. It’s far more likely to be a scam. Common sense can also help steer us through tasks without getting lost in unnecessary complications and ludicrous plans. But can it help us with science?

When you think about it, science has a completely different approach to common sense. When we use common sense, we look at something and make a reasonable guess based on what we know about the world. Science by comparison begins with no common sense. It simply measures something in controlled conditions, gathers the readings and develops a theory to explain those results. If the theory is completely against common sense, that’s irrelevant. The only important thing is to understand what is actually happening, not what should reasonably be happening.

For example, what if we wandered out to our local park and looked at a fully grown tree and asked ourselves the question ‘where did all that wood come from?’, our common sense view would probably be that the tree must have sucked up all that matter out of the ground. The ground is full of matter and the air has very little matter so the tree must have got it out of the ground. Common sense gives us a very sensible answer.

About 400 years ago a Flemish guy named Jan Baptista Van Helmont also asked himself that very same question. Instead of sticking with the common sense answer, he decided to use a scientific approach.He planted a small tree in 200 pounds of soil and left it to grow. A while later, he weighed the tree and its soil again. The tree had gained 164 pounds but the soil had only lost two ounces! Clearly, the tree hadn’t got its matter from the soil.

We now know that most of a tree’s mass is carbon, oxygen, and hydrogen. It gets the carbon from the carbon dioxide in the atmosphere and the oxygen and hydrogen from water. Only a tiny percentage of its weight comes from the dry soil that it stands on.

What Van Helmont found out goes completely against common sense. Trees grow from air and water? That’s ridiculous! But it’s true. In fact, studies over the years have shown that the common sense view - that trees get their mass from the soil - is so alluring that a significant percentage of students still choose that answer after being taught the actual process. Teachers are often very frustrated that many of their students will not shift from their common sense ideas, even if those ideas are completely wrong.

Climate Change does also run against common sense. How on earth could we actually change the climate of the whole planet? It's ridiculous! But, just like Van Helmont, hundreds of skilled people have made extensive measurements over decades and those are the results they've found. The answer may not fit with common sense but that is irrelevant, just as irrelevant as some people finding the results alarmist or negative or pessimistic or judgemental.

I don't like the idea that we're changing the Earth's climate. I don't like it at all. Based on the evidence, the next few centuries will be terrible for us and there's a good chance we'll end up a fraction of our current numbers, living mostly underground to avoid the hostile environment around us. It's an awful scenario, but that doesn't change the evidence. People can go to the Spectator debate if they want to and discuss the issue heatedly but they may as well be debating what trees are made from.