Just what is global warming anyway?


Given the amount of news and media coverage about global warming you may have suspected that asking ‘what is global warming?’ was a bit of a stupid question. In the first instance it’s worth remembering that there are no stupid questions only stupid answers. But even ignoring that, ‘what is global warming?’ isn’t a stupid question. In fact it’s a very good one. Why?

Because listening to someone give an answer to the question ‘what is global warming?’ can tell you something interesting about that person. And perhaps people in general. Continue reading

Exponential energy

Here’s a remarkable fact.

In the years since 1990, our global civilisation used more energy than had been used in the previous several hundred thousand years, possibly since modern humans first evolved.

No, really. All the energy extracted by burning wood, coal, gas, oil and obtained from wind, solar, hydro and nuclear fission up to 1990. That same amount of energy used again plus a bit more in a little over 20 years.

How on Earth is that possible? To begin to answer that, we need to acknowledge that we are living in a period of quite incredible change. Yet this rate of change is something that we have gotten used to. Indeed, it was something that we were born into: a period of exponential growth. What does this exponential growth in energy look like? Something like this:

Continue reading


I had a slinky as a child and loved it. Initially because if you stretched it out a little bit and peered inside, it looked similar to this (alas no Tom Baker would appear at the other end). And then because it walked down stairs. All by itself. How did it do that? In that respect, a slinky is a fantastic tool for understanding physics. What is going on in a slinky that makes it able to walk down stairs or in the above instance a treadmill? Or perhaps a simpler question: what happens if you hold a slinky up so that its coils stretch down to just above the ground and then drop it? Continue reading

The intergenerational ponzi scheme

A ponzi scheme is a classic scam that despite being guaranteed to collapse continues to work and leave people penniless. It goes something like this. John tells Jane that he has a fantastic money making opportunity. If Jane invests she will get an annual return on that investment of 20%. Wow! Jane invests and sure enough next year she gets a payment of 20% of her original investment. Other people hear about her success and sign up. Soon John has many investors and a large amount of money in circulation. But none of that money was ever invested.

The second person that signed up to John’s scheme was Jack. John simply took 20% of Jack’s money and gave it to Jane. The rest he pocketed (and most probably promptly spent). Just like he pocketed Jane’s money. Of the third person’s money, John took 20% for Jane and 20% for Jack. The fourth person’s money paid the 20% of the first three. And so on, until John is unable to recruit enough new people to pay the returns of the current list of ‘clients’. There’s a short delay during which John avoids calls, perhaps changes address and if he’s sensible hires a good lawyer (with whatever money is left). Then the whole system collapses in on itself. Well, that’s the basics. Real life ponzi schemes can be much more complicated than that. But they all work on the same principles. Why they work, why people get sucked in and lose perhaps everything they have, are very interesting questions. Questions that get asked quite a lot since Bernie Madoff. If you rip people off to the tune of $18 billion dollars I guess that will make the news for some time. Continue reading

What is a complex system?

It’s a reasonable question. If I tell you that I work at the Institute for Complex Systems Simulation, then you may ask what is a complex system. I don’t think there is a definitive answer (so it’s pretty mean of us to ask PhD candidates this in their interview). I would say it’s a perspective or an approach to systems that traditionally have been hard to understand. Here, let me show you what I mean (this really works well full screen and with the sound up):

That is a complex system in which the interaction of individuals (birds) that follow three simple rules (try not to get too far away from your neighbours, but don’t get too close and try to go in the same general direction) can produce emergent behaviour that would not be predicted by analysing those simple rules alone. It also happens to be incredibly beautiful and captures a central element of what we can find so awe inspiring about nature. Much like biological evolution, a complex system seems to be able to continually generate complicated, interacting, dynamical patterns. In fact, the evolution of life on Earth, the process that produced hummingbirds and whales, worms and giant redwoods may be understood as a planetary scale complex system. Continue reading

Peak Phosphorus

You’ve heard of peak oil. You haven’t? Peak oil is just another way of saying that the rate at which we are extracting fossil fuels such as oil, coal and gas is much, much faster that the rate at which they are replaced. It took many millions of years to produce the large deposits that we have in just a couple of centuries significantly depleted. They will run out. The only question is when. Peak oil is the moment when the global production of oil starts to decrease. Year on year reductions until there is none left. Time for solar power. Or nuclear. Or wind. Or something else.

Just like oil, we are currently consuming mineral phosphorus at a much greater rate than its natural replenishment. In fact, given that we get most of our phosphourus from rocks which take geological timescales to renew, we can assume that it doesn’t get renewed at all. And so at some point we will reach peak phosphorus. This is actually something of a big deal. Potentialy much more so than peak oil. Why? Continue reading


I spend most of my time doubting what it is that I’m doing. Most? Pretty much all of my time. Much is made of doubt in science. The deep mystery of the universe. Peering into the unkown.

I’m not talking about that sort of doubt. No, I’m talking about the fact that nearly every day I have the continual feeling that I have absolutely no idea what I’m doing. Feyman talks very eloquently about doubt and ignorance¬† in science. The forever frustration in trying to understand the rules of the game that nature is playing. I don’t even know what game I’m looking at most of the time. Every now and again the crowd cheer and some people move about or swap places. Something significant has happened I conclude. Then it’s back to white noise.

The reasons for this are (mainly) twofold. First and foremost I’m not very smart. I wish I was. But there it is and that’s how it goes. I’ve just got to get on with it. Second, I do ‘multidisciplinary’ research. I spend a lot of my time talking to people who really do know things. And who are also smart. There’s a wonderful passage in an E. O. Wilson book (title escapes me) in which he describes crouching down at the edge of a tropical rain forest, looking at a small wolf spider. Staring into its tiny, unblinking eyes he considers how little we know about this particular species and how he could happily imagine spending many years or decades discovering how it moves, hunts, breeds and makes its living among the giant trees.

I appreciate this sort of scientific obsession. To continually learn more about something and so fill in more of the blanks. The ability to write a richer story about some little facet of nature. But try as I might (and OK, I haven’t tried that hard) I always seem to get distracted by something else. Sometimes it’s not the something else per se, but that way that this new thing may interact with some other things.

I used to play a game as a child. I’m sure many others played/play this sort of game too. You name two different things. Then you connect them by telling a story. Telephone and conkers. Blanket and abseil. Points awarded to the best fabulist. If you’re not careful, you can see connections everywhere. That’s a common feature of conspiracy theories. But doubt should limit the sort of epistemological damage that unconstrainted connections can do.

If I want to study connections and their system properties then I’m doomed to a life of doubt. But I always hold out for those moments when I make out the cheers and shouts, a pattern emerges and I feel I’ve learnt something.

New paper in press

I’m a co-author on a paper that will soon be published in the Journal of Biogeography. You can download a PDF version of it here. It’s about how we can make better predictions of the response of plants, trees and other vegetation to things like climate change. This is something that a lot of people are spending a lot of time and money trying to do.

Why such interest? Take the change in forest cover for example. Climate models predict potentially profound changes in temperature and rainfall in the Amazon region. If significant numbers of trees in rain forests were to die in response to such changes, they would release many millions of tons of carbon dioxide into the atmosphere which, along with other effects, would have large impacts on the local and global climate.

In this paper we have suggested how vegetation models (in particular, models called Dynamic Global Vegetation Models – DGVMs) could be improved by using the ever-increasing amounts of new data being produced by field studies, aircraft and satellites. We outline how this data can improve model performance via Bayesian statistics. Currently, data is used to determine the best values for model parameters. For example, people conduct experiements to try to determine how photosynthesis is affected by changing temperature. But this leaves a lot of data unused. By¬†inverting DGVMs it should be possible to produce better model predictions because more of the data can be employed to refine model output. Depending on how you feel about statistical methods and inference this may be a great idea or something really rather unsettling. To those experience the latter emotion I would say: relax, it doesn’t matter what colour the cat is, only that it catches mice! Actually that may make it worse. Let’s talk about it over coffee.