Empirical evidence of human-induced climate change? Here you go

Senator Malcolm Roberts
Senator Malcolm Roberts

One Nation Senator Malcolm Roberts is at it again, banging on about climate change denial.

Last week, Dr Karl Kruszelnicki wrote on Twitter that he’d met with Senator Roberts and … “Unfortunately, I felt that we could not find common ground –  our proposed debate would be pointless.” In response, Roberts immediately posted a YouTube video claiming he “absolutely won it” – the debate on climate change that didn’t happen.

Several of the best scientific minds in the world have tried to explain climate change to Senator Roberts, including Nobel Prize winner Professor Peter Doherty, Australia’s chief scientist Dr Alan Finkel, celebrity science communicator Professor Brian Cox and Gavin Schmidt, head of NASA’s Goddard Institute of Space Studies.

But, somehow, the message still hasn’t gotten through. Last month, Roberts accused Labor Senator McAllister of not having any empirical evidence of him not having empirical evidence (I think that’s what he meant. You figure it out).

I’m not sure if anyone else is still listening to this guy, but it got me thinking: How is it possible for a literate person to still believe there’s no “empirical evidence” for human-induced climate change? And why can’t we just settle this once and for all?

First of all, let’s be clear: the question is kinda dumb. Say for a second it isn’t us – the warming. Let’s pretend it is volcanoes, solar flares, aliens (someone help me out … since there is nothing else that is credibly causing it, but anyway).

It doesn’t change the fact that we know greenhouse gases cause warming. Empirically. There are a bunch of experiments you can do at home to test it for yourself, going all the way back to Tyndall’s original 1859 proof, yes, 158 years ago.

If you couldn’t be bothered with classroomy type things and sticking thermometers in jars, the easiest “empirical” proof is to go on Amazon, buy a $15 infrared thermometer, take out the thermometer, and wave it in the air like you just don’t care.

You will notice that when an infrared thermometer is pointing straight up at blue sky, it shows the air as being cooler than when you point it sideways at the horizon. That’s because sideways the thermometer is seeing more greenhouse gas. Oh, and watch out for clouds. Infrared bouncing off clouds is also hotter than the blue bits of sky, because water vapour is a greenhouse gas. So. There. Proven. Empirically.

We know greenhouse gas causes warming, and the world is getting warmer – setting aside who is to blame, for now – and we know more greenhouse gases make it worse. So why on earth would we keep adding more gas? If your boat is leaking, you don’t refuse to bail water because you didn’t make the hole.

Ultimately, whether or not human beings cause global warming shouldn’t matter, as much as whether we can stop it. Or slow it down. Which requires producing less greenhouse gas.

Anyway, let’s set aside logic for a minute more, and consider again our friend Roberts. What exactly is he looking for when he says “empirical evidence” that humans are causing climate change? In an interview on Lateline last year, Roberts defined “empirical evidence” as “observations in the real world, it’s measured real world data”.

He said it again in his YouTube video yesterday:

“Science is decided by measured data, physical observation.”

There are a bunch of problems with this definition of science, in particular whether a computer model exists in the real world. More importantly, scientists often measure the effects of a thing as evidence of the thing itself. For example, the busted remnants of a decayed Higgs Boson prove the Higgs Boson was there a second ago – even if we never saw the Higgs Boson. There’s also corroboration. I’ve never jabbed myself in the eye with a pen, but I’m 100 per cent sure it would hurt based on what happens when I jab myself elsewhere. Still, for Roberts’ benefit, let’s go with the simplest definition possible: If you can’t see it, it ain’t real.

So how do you see whether humans cause climate change? How do we know that it is us, humans, punching a hole in the boat?

Two plastics bags and a rock

The answer is simple and fairly cheap. All you need is $50, two plastic bags and a rock.

In your first plastic bag, you need some old air – the older, the better. By “old air” I mean air out of an old scuba tank, BB gun, air compressor – anything where the container is inert, airtight and old, you’re all good. The older the old air is, the more clearly you’ll see the results.

Twenty years old would be good; 40 years would be amazing. You also want your plastic bag to be airtight and clean. The pros use Teldar bags. You could also rig yourself a “lung box” to pump the sample air into the bag. Oh, but don’t Google “lung box”. It’s gross. Try “vacuum air sampling box”. Better still, if you’re flush with coin, jump online and grab a second-hand “summa canister” for about $300.

Now, repeat this whole deal with some today air. By “today air” I mean air from today. Preferably, your today-air sample comes from the same spot as your old-air. If your old scuba tank was filled up near a highway, your newer air should come from a similar place. That way the comparison between the two is fairer. Less contamination.

The results should still be similar, but we’re doing science. Best case scenario, your old air and your new air were collected out in the country where the air is cleaner, or while skydiving – both using identical methods at the same time of year (winter and summer also effect what’s going on with trees and stuff). And you’d do it a few hundred times to make sure, like these guys.

Now grab a rock. Not, any old rock. Some rocks react with carbon – like basalt – and some have no carbon at all. So grab a chunk of limestone or marble.

Now, find an isotope ratio mass spectrometer. Luckily, most large universities have one in their biology, geology or agriculture departments, and will let you put samples through for about 15 bucks each. Some schools have dedicated analysis labs you can take samples to.

Just don’t tell them where your “old air”and “today air” came from, or when – in case they’re part of a global plot with China or the United Nations to establish a New World Order (Ask Roberts about that). If you really don’t want to trust a lab, the whole deal gets really expensive.

For a high-end IRMS all of your own, you’re looking at about $300,000 for the kit and a few years of study to operate it properly, since you’ll be firing ions through a big curved magnet, which is tricky. Or, you can get a smaller “wavelength-scanned cavity ring-down spectroscopy” unit for about $80,000. It’s almost as good and has lasers. But it’s just easier to pay $15 per sample to get a uni to do your testing.

Now take your two plastic bags full of air, scribble this down on a piece of paper and hand it to them:

Dear Sir/Madam, please tell me the ratios of the types of carbon and the ratios of oxygen to nitrogen in these air samples and rock sample. Here’s my $45. PS: Yes, I know there’s probably no nitrogen in the rock.

Okay, now bear with me.

There are three types of carbon naturally occurring around you – and in you: 12C, 13C and 14C, and each behave differently. 14C decays over a long time because it is radioactive. About 90 per cent of the 14C in any given sample will decay over a period of about 20,000 years. Meanwhile, new 14C is formed when rays from the sun mess up nitrogen atoms in the atmosphere. So very old carbon – like coal, oil and gas – contains no 14C. The 14C decayed long ago. If you burn really old carbon, the 14C levels in coal smoke are almost zero. But if you burn a tree that absorbed carbon recently, the 14C is still there. There is 14C in your body right now, unless you stopped breathing a very long time ago. The same goes for carbon circulated by the ocean, soil, and so on – 14C pretty much everywhere except coal, oil and gas.

Oh, okay, so here’s our slip of paper back from the lab with three rows of numbers in five columns. Yours should look something like (put your data in the blank spaces):


Air 1
Air 2

Don’t worry about the ‘±’ and ‘‰’ symbols at the top. That’s the margin of error in thousandths of a percent – which is tiny. Now look at the last two columns, comparing your two air samples – Air 1 and Air 2. You’ll see the amount of oxygen in the air is falling over time compared to the amount of nitrogen. Why? Because natural sources like trees or the ocean release carbon without burning it. Burning involves oxygen. So, empirically, the rising carbon levels in the atmosphere can only be coming from burning something.

“What about forest fires?” you say. Good point. There have always been forest fires, but they’re getting worse. Humans start six times as many fires as is natural. But we also know forest fires add somewhere between 1/8th and half of the emissions we create from burning fossil fuels.

“What about volcanoes?” Yep, they’ve checked that too. Human activity causes about 100 times more greenhouse gas than volcanoes. Plus, there aren’t suddenly an ever increasing number of volcanoes going off throughout the last century.

There is another main difference between your two air samples, in the third column. There’s a drop in the amount of 14C relative to the other two types of carbon, between the old air and today air – also known as “radiocarbon dilution”. You should see about a three per cent drop per year.

So why is the 14C level dropping? And what are we burning that has no 14C in it?

For there to be no 14C in something, it has to be really old carbon. More than 20,000 years old. See where this is going? This increase in greenhouse gas in the atmosphere must be caused by burning fossil-aged carbon.

That’s basically it. There really is no way around it. The main rise in greenhouse gas levels in the air is coming from burning coal, oil and gas.

There is a bunch of other evidence – the vertical structure of temperature changes (warming in the lower atmosphere and cooling in the upper atmosphere) and the greater warming at night than in the daytime, both of which are expected from more CO2 and are outside the range of natural variability, and can’t be explained by warming due to the sun.

So there it is, based on “measured real world data” that anyone can get their hands on without the conspiracy people messing with their empiricalness.

We put the hole in the boat.

As for the more important question, “Can we stop it?” the answer is also very simple: not without stopping burning coal, oil and gas.

Oh, I almost forgot about the rock. That was just for fun. You can also see how the rock has plenty of 12C but no 14C, and no nitrogen (*unless… you didn’t clean it.) If you’re interested, you can take another $15 back to the lab, and measure a bunch of other cool stuff like the ratio of potassium (40K) to argon (40Ar) and tell how old the rock is. But that would take more classroom type stuff to get into.

Marcus Gibson is a sustainability professional in the infrastructure sector, former novelist, member of Mensa, and has been a climate change presenter in former US Vice President Al Gore’s “Climate Reality Project” since 2006.

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7 Responses to “Empirical evidence of human-induced climate change? Here you go”

  • Lucy Jr says:

    There are some who will never ever accept evidence, however complete the evidence is, if it does not match what they want to believe.

    It is a tragedy when such types are capable of influencing matters of critical importance such as climate policy.

  • My recently published book (A Climate for Denial) sheds some light on why some people still find it difficult to accept climate change science:


  • The funniest sentence: “If your boat is leaking, you don’t refuse to bail water because you didn’t make the hole.” True. But put it the other way around: If someone did make the hole, chances are this someone will refuse to bail water, because he is better off taking his time to pretend that he didn’t make the hole, along with pretending (second row of defence) that the water in the boat is not a problem, and (third row): that we better adapt to it. That is a good strategy! It plays out as long as the boat doesn’t sink. And, worse: If saved eventually, it remains a good strategy for the culprit, even beyond that, unless the culprit is actively punished for his misbehavior. Throw those out who keep sabotaging the boat! Let them get back in only if they agree to help with plugging the leak. The problem with our societies is that those who sabotage need not not fear to be punished. The climate crisis is a crisis in many ways: It is also a crisis of the ill-fated christian principle of forgiveness. A great many things must be changed. It wouldn’t be so bad to start with the ill-belief in forgiveness. Anyway, it is time we realize we must neither understand, nor convince the deniers. We must defeat them, plain and simple. And for sure: Scientific explanations won’t do the job!

    • Marcus Gibson says:

      Thanks Peter, I admit I do struggle with this one, alternating between two positions depending on the context: (1) anyone still in denial is evil or willfully ignorant at the expense of human lives, and should be dealt with harshly, and (2) those of us on the side of humanity, factual correctness, and a mature response to the threat should rise above the ruthlessness of deniers and always seek to illuminate the issue rather than devolve into threats and insults. Sometimes my anger is difficult to contain. But the main differentiator for me is when young people are listening. The youth of today need hope, and the opportunity for faith that not all of our institutions are broken. On one hand, if we cannot preserve basic decency while winning this battle, then we have not won. On the other, you are right – there must be consequences for breaching the basic moral tenets of human society.

  • Marcus Gibson says:

    Thanks TFE.

    Gary, the idea was that (a) folks like Sen. Roberts don’t trust published data anyway – so there’s wasn’t much point publishing more, (b) the article explains how to get your own data, and (c) you can see some of it (declining O2, Cape Grim) in the ‘these guys’ link in the article.

    Here’s a selection of additional sources:

    For declining C14 ratio see Levin and Hesshaimer (2006) here:

    For C12/13 (which I didn’t really go into, but it’s another proof using the same evidence) see Bohm at al (2002): http://onlinelibrary.wiley.com/doi/10.1029/2001GC000264/full

    There are numerous articles on the subject if you look up carbon isotopes and climate change, e.g.: http://www.cupblog.org/?p=6043

  • Gary Dean says:

    I think some data is omitted from the slip of paper. All question marks everywhere. Also there’re two x Air 1 rows. Any chance of getting the correct slip of paper?

    • TFE Journos says:

      Hi Gary, the question marks were supposed to represent where your own gathered data would go. We’ve updated the story to reflect this, and fixed the error. Thanks!

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