Of all of the problems of reconciling growth with planetary boundaries probably none is more urgent and none is more complicated than the challenge of energy. Remember that the whole world economy grew up, starting with the steam engine, then the internal combustion engine, the gas turbine as a fossil fuel built world economy. Fossil fuels, coal, oil, gas, have been our friend. They have been the basis on which the modern world has been built. And indeed until James Watt in 1776 came along with his steam engine, there was no way to even think about sustained economic progress. Where would the energy for industry come from? Every time industry would start to develop in the pre-steam engine age, so many trees would be chopped down to feed the boilers that the limits of industrialization were very quickly reached. It was fossil fuels that allowed the breakthrough to the era of modern economic growth. I emphasize this because that history reminds us of how deep the challenge is. Right now fossil fuels are not our friend because when coal, oil, or gas is burned the carbon that is the basis of those fossil fuels combines with oxygen and produces CO2, carbon dioxide, which is emitted into the air, which is the main greenhouse gas warming the planet, changing the climate, and endangering humanity and other species. And so what has been the key at the very core of the world economic growth is now at the core of our major problem. Well, you might say use less energy, but it’s not so simple.
Because as a physicist will remind us, what is energy? Quality energy is the ability to, to work. Any useful work in, in economy depends on energy. Sure, we waste a lot of energy in the form of release of heat or friction or driving cars much larger than they need to be or poorly insulated buildings. So energy efficiency is clearly part of any solution for sustainable development. But the world needs energy resources, will use energy resources, and the use of energy, even with a substantial gain of efficiency, is likely to increase in the aggregate as the world economy expands by factor three or by factor four as we have just seen. And so we have a problem. More energy is needed. The traditional forms of energy, the fossil fuels of coal, oil, and gas, can’t do it for us because that would create a massive intensification of the climate change problem. How big of an intensification?
That’s what I’d like to discuss, so that we get some parameters of where we are and where we’re going. This graph shows again on a logarithmic scale on the horizontal axis and on the vertical axis the income of different countries and the primary energy use of those countries, the energy consumption. Total energy use by country would include the fossil fuels, it might include wood burning, hydroelectric power, geothermal energy, wind and solar power, nuclear power or some other forms for instance biofuels. And what is done in this graph is for every country in the world to measure first the total output measured as the gross domestic product, and then to compare that with the total primary energy use. Which can be expressed in a number of ways, in units of kilowatts, or kilowatt hours, it can be expressed in tons of oil equivalent energy where, you take the amount of energy in one ton of oil, and then for all the other kinds of energy, whether it’s coal or gas or hydro and so forth, you look at the amounts of, of energy available from that resource and convert it as if it were tons of oil that had that much energy potential. And then express all the different energy sources with these conversion factors as a tons of energy equivalent amount of primary energy use. What you see when you graph the total output of an economy versus its energy consumption is essentially a straight line, though of course the countries don’t fall exactly on this upward sloping line. What this line signifies is that a doubling of the size of an economy tends to be associated with a doubling of primary energy use. Energy use scales alongside in proportion and in relatively constant ratio with total size of the economy. So, as the economy grows the energy use will tend to grow along side it. Save for break those in technology that allow for greater energy efficiency.
Lets look quantitatively at how much energy we use and what that implies for how much carbon dioxide we therefore emit into the atmosphere and what that implies for how much climate change we’re causing.
If you look at the amount of energy use by country you find that, roughly speaking, this is on average because countries differ, but they don’t differ all that widely. For every $1,000 of total production in the economy, the total energy use expressed in tons of oil equivalent tends to rise by about 0.19 tons of oil. What is 0.19 tons of oil? These are metric tons. So, a metric ton is 1,000 kilograms. So, 0.19 of a metric ton is 190 kilograms. So let me put it again this way. $1,000 of production, on average, expressed in, $2,005, let me add one more, parentheses, is associated with about 190 kilograms of oil use, or an equivalent amount of energy contained in coal or natural gas or one of the other non fossil fuel forms of energy. That gives us the scale of how much energy we use for each $1,000 of production. Now, if you look at the mix of, the energy sources in the world, mostly fossil fuels, but also some nuclear power, some wind, some solar, some some charcoal from trees some biofuel say from sugar cane converted to ethanol for automobile use as in Brazil. On average, every ton of oil equivalent energy is equivalent to about 2.4 tons of carbon dioxide emissions. In other words burn a ton equivalent of energy, and you put up more than two tons of CO2 into the atmosphere.
How much CO2? That depends on exactly which energy source you’re using. If it’s nuclear power, zero, because nuclear power is not a fossil fuel, and therefore nuclear power does not by itself create carbon dioxide emissions. If it’s coal, it’s higher than that average because coal, being almost all carbon with some impurities, when it burns, creates CO2 with little other energy created by the coal. And so coal creates the most carbon dioxide emissions per unit of energy of any fuel. Gas, and natural gas and oil emit less. So coal for a ton of coal burned, you get about four tons of carbon dioxide emitted into the air. For a ton of I should say not for a ton coal but for a, an amount of coal equal in energy to one ton of oil. That’s the right way to say it. You get about four tons of CO2 emission. For one ton of oil, you get about 3.1 tons of CO2 emission. For the amount of natural gas equivalent to a ton of oil in it’s energy content, you get about 2.4 tons of CO2. And for hydroelectric power, for solar power, for wind, zero.
So, you can see why those energy sources are highly desirable from the point of heading off climate change. Let’s summarize again.Each $1000 of production requires a 190 kilograms, or 0.19 tons of oil equivalent of energy. And each one ton of oil equivalent on average is associated with 2.4 tons of CO2 emissions. So let’s do the arithmetic. Expressed in $2,005 used for this illustration, the world economy at 2010 was at about $68 trillion. $68 times 0.19 tons of oil equivalent per $1,000 times 2.4 tons of carbon dioxide per ton of oil equivalent energy turns out to be 31 billion tons of CO2 emission, and viola, that’s what the world released into the atmosphere in 2010 by virtue of its fossil fuel use.
So you see we can measure the size of the economy times the energy use per unit of economy, per $1,000, times the amount of CO2 released per unit of energy. And the result is a very big number, 31 billion tons of carbon dioxide released. We also put CO2 into the atmosphere as humans in other ways. We chop down trees. And when we chop down trees, the carbon that was stored in those trees is released into the atmosphere if the trees are burned or, or decay. And so carbon that was sequestered biologically is released into the atmosphere as well. That adds a few billion tons of carbon dioxide emissions in addition to those caused by fossils fuel use. Little more arithmetic. For every ton of CO2 put into the air, just a bit less than half of that stays in the air, because some of the CO2 dissolves in the ocean, some of it gets sequestered in plants and trees back on Earth. And so, of the one ton that’s put into the air, approximately 0.46 of that or 46% of what’s admitted into the air, stays in the air. And the other 54% typically is stored in what are called natural sinks, the oceans or the land.
Now, that means that if we put 31 billion tons into the air, a little over 14 billion of those tons stayed in the air. Is that a lot, 14 billion tons, for our big atmosphere? Well we can make that calculation.
We can look at the total volume of the atmosphere, how many molecules are there. How many molecules of CO2 have been put up in those tons? You have to get out your chemistry text to do that. And what you find when you do that is that for every 7.8 billion tons of carbon dioxide put into the atmosphere, the concentration of carbon dioxide in the atmosphere rises by one part per million. So that’s the translation factor. To raise the CO2 concentration in the atmosphere, which is filled with nitrogen and oxygen, and many other mole-, types of molecules. To raise the CO2 by one molecule per each million molecules of all kinds in the atmosphere, you have to put into the atmosphere 7.8 billion tons.
So this gives us now a quantitative sense of what we’re doing. If we have put 14.2 billion tons staying in the air, and 7.8 billion tons raises the carbon dioxide concentration by one part per million. Then the amount that we emitted into the atmosphere in 2010 from fossil fuel use, raised the, carbon dioxide concentration by about 1.8 parts per million or, nearly two molecules for every million in the atmosphere were now CO2 it raised in CO2 concentrations.
Is that a lot? Yes.
Is it frightening? Yes.
Let me show you why. We look again, at a graph of the concentration of CO2 in the atmosphere on the planet Earth, over hundreds of thousands of years. And the concentration of CO2 fluctuates for normal process, even putting humanity out of the story, over geologic time these levels of CO2 rise and then fall and then rise and fall as part of the long run carbon dioxide cycle. And that cycle is driven in important part by systematic changes of the earth’s orbit. And if you look at this reconstruction of the carbon dioxide concentration of the atmosphere over the last 800,000 years starting all the way to the left-hand side of the graph, the first peak you see is the carbon dioxide rose to a little bit over 250 parts per million. Then it fell to under 200 parts per million. Then around 700,000 years ago it rose again to nearly 250 parts per million and then it fell again, then it had another peak at 600,000 years ago, and so forth. So you go up and down, up and down, driven by natural changes of the Earth’s orbital cycle, but then as you move to the right that means coming closer and closer to the present on this graph. Suddenly, something really weird happens. Instead of going up down up down up down, it suddenly goes up, up, up, up, up, up, up. Shoot straight up. Just in the last 100 years of this 800,000 year graph. That’s humanity burning fossil fuel. Thank you, James Watt. Great invention. Great idea.
You made possible the world economy, but now look at the situation. CO2 soaring. How high does it go? Far higher than anything we’ve seen on this planet for 800,000 years, indeed for 3 million years. In 2013 it reached 400 parts per million. A CO2 concentration the likes of which we have not seen on the planet Earth for millions and millions of years. What the climate scientists tell us is, that this kind of change is consistent with a significant rise of temperatures on the planet. Indeed if we reach, say 450 parts per million of CO2, we are very likely to be living on a planet that on average is two degrees centigrade warmer than before the industrial revolution. Now two degrees centigrade might not sound like much, but it implies even larger increases of temperature in the higher latitudes and it implies massive changes of the Earth’s climate, of rainfall, of droughts, of floods, of sea level increase. So we’re talking about changes in CO2 concentrations that when translated into global warming, and into climate change more generally, are extremely large and extremely dangerous and happening now.
How fast are they happening? If we’re at 400 parts per million today, and that’s rising by about two parts per million each year, you can see that to reach 450 is just 25 years from now. My word. We can’t even change it at world energy system at, at that rate. So we’re on a trajectory that is very fast, and very troubling. And, add in to the fact that that’s assuming we stay where we are. Now think about tripling the world economy and tripling the amount of energy used, and if we do it using the same energy mix that we have right now, we’d be increasing CO2 not two parts per million, but five or six parts per million within a few decades. In other words, if we don’t change course we are on a path of extraordinary peril.
Where because of our fossil fuel reliance, we would be seeing mega-droughts, we would be seeing mega-floods, more extreme storms, more species extinction, more crop failures. A massive sea level rise over time, and a massive acidification of the ocean as that CO2 dissolves into the ocean, produces carbonic acid, and reduces the pH of the ocean. We have to change course, and we have to change course quickly. More quickly than the politicians are telling us, by far.
But there’s good news, let me not leave us in despair. We have powerful technologies at sharply falling prices for solar power, for wind power, for energy efficiency, for smarter systems that can economize tremendously on energy and shift us to low carbon means. We’re going to revisit some of those methods very shortly.