It's the economic growth, stupid

The fiery physics of forever growth

A few years ago I came across a blog post that blew my mind and recast how I saw not just climate and energy, but our civilisational future.

The post by Tom Murphy, professor of physics at the University of California, San Diego, written in 2011, described how continual energy growth, would, under any energy source pathway, generate enough waste heat to raise the temperature of Earth’s surface to the boiling point of water in just a few hundred years.

I’ll let you digest that for a second.

(Waste heat is the unused heat expelled into the surrounding environment by any device that uses energy to work).

Essentially, the mechanics of energy and heat are such that we simply have to stop growing our energy use, whatever the source, or risk boiling ourselves and everything else alive.

Literally.

I hope you can see this is not climate denial. Far from it. We need to get off fossil fuels asap or our continual burning of them for energy will boil us all alive long before the waste heat of renewable energy will do the same thing.

But the bottom line is that there’s a limit to energy growth in the most absolute, physical terms possible. Recognising this is to recognise that we can never decouple humanity from the biophysical processes of nature, as some eco-modernists would have us believe.

2.3% growth assumption

Murphy’s calculations rest on the primary assumption that energy growth in the future will be from solar, not fossil fuels, and will proceed at 2.3% globally per year, like it has almost every year (2-3%) since about 1850 (and since about 1650 in the US). So this assumption is by no means far fetched. (He chose 2.3% because it gives a tidy expansion factor of 10 every 100 years).

So under these growth conditions, if we put a solar panel operating at 20% efficiency (i.e 80% waste heat, about what they are now) on every square inch of the Earth’s land surface we’d hit the limit for how much energy humanity could ever harvest from the sun in just 275 years. Or about the same distance in the future as the opening of the British Museum in London was in the past. Note that in this future, every piece of Earth must have a solar panel on it.

Expanding this thought experiment to 100% efficient panels (no waste heat, which the laws of thermodynamics make impossible) and also covering every inch of the oceans as well as the land would give us another 125 years, maxxing us out at 400 years of energy growth. But remember, at 400 years we really hit the waste heat issue and the surface-of-Earth-as-hot-as-boiling-water problem. So in reality we’d never get close to 400 years.

But what if we weren’t constrained by putting panels on Earth and could surround the sun with a solar panel array? Under conditions where we could harvest the output of the sun in all directions we’d hit the limit of what it could provide us energetically in 1,300 years. 1,300 years ago the Roman Empire, which looms large in our cultural memory, was long gone. In human historical timescales these are not long periods. On geological timescales they aren’t even the blink of an eye.

And what if we weren’t constrained by solar technology? Murphy shows that even with fusion energy, a sustained 2.3% energy growth rate would require us to produce as much energy as the entire sun within 1,400 years.

We have very little time to play with.

Murphy has a similar calculation for all physical resource use to demonstrate how it is not just energy use, but economic growth itself that physics puts tight bounds on. Because economic growth has to be a claim on some resource or another and can’t be on nothing, and because things like food and water have to be exchanged for something, Murphy says 2.3% economic growth means we’d hit a saturation point that makes more growth impossible within 200 years.

As he sums it up: “growth as we have known it will no longer be able to drive the way civilization operates. The entire financial, economic, political and social system will be forced to undergo radical change, leaving something bearing little resemblance to today’s world.”

Still political not physical

All this makes those thinking about and demanding a world beyond growth the only adults in the room – namely the degrowthers and postgrowthers. The shrinking of the human enterprise in energy, economic and resource terms is not just desirable but totally inevitable.

Now, this isn’t to say that what we are facing right now is primarily a physical rather than political/structural problem, as it pertains to energy expansion itself. Today, and on any reasonable timeframe, the problem is one of politics and systems. We need to move from a growth system to stop mass extinctions, the collapse of ecosystems, the breakdown of the climate and the pillaging of the Earth for everything it can provide. Unhindered capitalist growth also tends to further entrench rich/poor inequities that push societies to misery and fascism. The physical limits to green energy growth are a long way down the list of why we need to move away from growth. But on a not very long timescale, you just can’t escape the raw physics.

Incidentally, commentator-economists like Noah Smith have tried to argue against this by saying of course we won’t grow energy use forever so the argument is silly (although without ever suggesting exactly when we should stop growing or under what conditions), and also by suggesting that we can escape limits by ‘uploading’ everyone. He seemed very earnest in making this argument.

It should go without saying that this is not to argue against a switch from fossil fuels to renewables - we definitely do need to have a renewable energy base, not a fossil fuel one for our civilisation. We’ll meet this fiery end a lot sooner if we just keep using fossil fuels. But what Murphy shows us is that even if we switch the fuel source we cannot continue to grow at historical rates without burning up.

Of course there are many caveats to this, including a global population whose rate of growth is slowing, making 2.3% growth in perpetuity unlikely. But it’s a valuable thought experiment that challenges the central assumption underlying global economic policy, which is that growth can go on forever. Murphy is saying ok then, let’s talk about forever. Let’s see what that looks like. Which makes his main point worth repeating: we can’t grow energy use (even with incredibly efficient new technology) or the economy forever, regardless of the energy source.

Limits as existential threat

Of course in a global economic system geared to growth and only growth, physical limits are studiously ignored because they represent an existential threat to the system and the people that profit from it. This is one of the reasons why the first conference of its kind in Brussels a couple a weeks ago focused on degrowth ideas was roundly ignored by the mass media, despite the attendance of many journalists. It’s heretical to suggest moving beyond growth. But that is what we need to do to ease the pressure on our planet, slow ecological disaster and ensure equity between the global north and south. And if we don’t, the physics will force it eventually.

Anyway, I hope you found this as fascinating as I did when I first came across it, and do keep it in your back pocket if you ever bump into an economist who tells you we can grow everything forever.