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I is not PAT

Here’s an equation, a nice simple little equation:


The equation was developed in the 1970s during the course of a debate between Barry Commoner, Paul R. Ehrlich and John Holdren.

This little equation has had a big effect over the years on environmentalists and how they think and talk about the problems we face and how we should be trying to tackle them.

I is for impact

As in our impact on our environment. There can be a number of different kinds of impact, though the one that is most talked about, with good reason, is that of our carbon emissions and the effect they’re having on our climate.

P is for population

This is obvious. Of course if there are more of us then there is a greater impact, though the relationship is not necessarily proportional – a doubling of population won’t necessarily result in a doubling of impact nor will a halving of population necessarily bring about a halving of impact. It depends on the A and the T, and that’s really the thing with this equation. The situation is not as simple as this simple equation implies. P, A and T are not independent variables.

In most rich developed countries the birth rate has dropped such that it is now below replacement level, meaning that in most developed countries and also a number of developing countries the populations are shrinking. Japan’s population is projected to halve within a century. In 1960 Indian women were having on average 6 children each. That’s now down to 2.5 children and it’s continuing to decline. Globally, the birth rate has dropped dramatically and is now only slightly above the replacement level. On average, each woman today is having half as many children as her grandmother.

If this trend continues, which it is likely to do if we can get the poorest two billion people on the planet out of the extreme poverty in which they currently live, then world population could peak at the middle of this century at just over 9 billion, though if people are left living in poverty then their birth rate is likely to remain high and their population will continue to increase.

A is for affluence

Affluence, it seems pretty obvious too, increases impact. We know that we in the west with our carbon fuelled lifestyles have a hugely greater impact than an African villager.

Though increased affluence also has an impact on population growth. Increasing the affluence of the poorest in the world, improving infant mortality rates, access to education, particularly for girls, increasing urbanization (if you’re a subsistence farmer children can be an asset, from quite a young age they can help out on the farm, whereas for a city dweller each additional child is an additional cost), these things can all result in a reduction in the birth rate.

But that’s not all. The US and France are about as affluent as one another, per capita – the lifestyle of someone in France is just as good if not better than that of an American. Yet Americans emit twice as much carbon as their French equivalents. More than twice as much in fact. Almost three times as much. How come?

T is for technology


But perhaps before T there should be a little something, which we will call S, so the equation becomes:


You might think I’m just making up words here and you’re entitled to your views of course, but the S stands for society, that’s the little something I was talking about, which could even be quite a big something. A society can make choices that lead to a lower impact on its environment and choices that can lead to a greater impact.

Part of what makes up the choices we have available to us is T, technology. Thanks to technology we now have some very good ways of generating energy without burning fossil fuels. France made a choice back in 1973 during the oil crisis to get off fossil fuels, though because of their impact on the economy rather than their impact on the environment. But Britain, with its reserves of North Sea oil and gas coming on stream around then, and North America, the US and Canada, with fossil fuel reserves of their own, went down the fossil fuel route. You could say it was a random choice. It just happened that it suited France economically to get off fossil fuels and switch to nuclear, which it did within a couple of decades.

They chose the low carbon/low impact technology. Some people would say they chose the green technology. Others wouldn’t, but when you look at the results, compare the impacts of France and the US, or Sweden and Canada, however antinuclear you may be it’s hard to see how you could argue that France made a bad decision in going for nuclear in a big way. You might prefer it if they’d gone for renewables in an even bigger way, but they could never have gotten off fossil fuels in 15 years via renewables alone. Certainly not in the 70s and 80s and not even now.

But that is just one part of it. Societies can make other choices that are not so much about T, unless you see society itself as a form of technology, society as a well-oiled and sophisticated machine, or perhaps not so sophisticated or not so well-oiled, but whatever, a machine of some kind.

So for Americans, affluence means being able to drive to some burger joint in your gas guzzling pickup and scoff a load of beef from methane belching cattle whereas for the French it means walking leisurely around to a friends house with a nice locally produced bottle of wine and sitting around a table eating ratatouille made from the host’s home grown courgettes and aubergines and talking about philosophy.

Of course, that’s a cartoonish depiction of French and American lifestyles, but I don’t care. Cartoons are fine, though some are less fine than others.


The point is, higher affluence does not necessarily mean higher impact. A more sophisticated society, one with a good public transport infrastructure and good degree of urbanization, people living quite close to one another rather than in the midst of some endless suburban sprawl, a society with a taste for a particular kind of good life, one that is sustainable rather than one that is destructive – to transform society in a way that will reduce its impact you need to sell the sustainable good life over the gas guzzling good life. Environmentalists haven’t yet managed to do that. People get the impression that these econuts’ idea of a good time is sitting around eating bowls of lentil stew and singing folk songs at one another. Doesn’t sound that appealing to most of us.

Do we like people?

It seems like we don’t that much. David Attenborough has described humans as a plague on the earth.

People are seen as the problem rather than the solution. There are too many of them eating too much and shitting too much. Population and consumption. But we’re not just mouths and arses. Let’s not forget the T. Technology. Actually, in the equation it’s supposed to refer to the inefficiency of technology, or the impact of technology on the environment. If you’re talking about the old 20th century fossil fuel burning technology then maybe it would be fair enough to say that technology is proportional to impact, but nowadays there’s so much more to technology than simply burning carbon.

Solar technology is advancing at an exponential rate, with a Moore’s Law like the one applying to computers. Last year the consumption of solar electricity throughout the world increased by 58%, use of wind power by 18%. Fourth generation nuclear reactors can generate power from the waste left by previous generations of nuclear, smaller modular nuclear reactors are being developed, India will soon be starting up a fast breeder reactor and is planning a further 62 reactors, most of which will use thorium rather than uranium as a fuel whilst in Norway an existing reactor is being run on thorium. And then there’s nuclear fusion, which some people say is 30 years away and always will be, but the fact is they’ve already managed to run a fusion reactor. Not for very long, but they have done it, and they’ve managed to do it with minuscule amounts of funding. If the money about to be invested in HS2 were to be put into developing fusion power then it could become a reality.


Though high speed rail is one reason why Europe’s emissions are lower than those of North America. A high speed train powered by low-carbon electricity is a far more green and pleasant way to travel than flying or driving.

Then there are the developments in agriculture such as GM crops which can be made resistant to pests and thus give higher yields and require fewer pesticides, meaning more food and less impact.

In addition to mouths and arses we also have brains. Human ingenuity and creativity are the things we should be focusing on.

A reminder of Tim's brain