Scary Math

The impact the humans are having on Earth’s resources depends essentially on three factors; population size, the affluence of this population, and our technological efficiency. This simple equation, laid out by the Stanford professor Paul Ehrlich nearly 40 years ago, makes for pretty scary math in 2010.

In a sobering, post-global-financial-crisis book, Prosperity Without Growth; Economics for a Finite Planet, Tim Jackson uses Ehrlich’s equation to succinctly illustrate the challenges ahead if we are going to live sustainably and equitably on this planet.

Carbon dioxide emissions make a good proxy for the rate at which we are using our planet’s resources. If, as the IPCC is calling for, we aim to stabilize atmospheric carbon dioxide at 450 parts per million by 2050, this means reducing our total carbon dioxide emissions by at least 4.9% per year between now and 2050.

However, affluence and global population are both growing, and appear very unlikely to do anything else between now and 2050 – what government could deliberately limit the affluence of its citizens? This means that the burden of reducing carbon dioxide emissions must fall on the efficiency with which we use the planet’s resources. Jackson let’s numbers tell the story of what this means:

  • In 2006 our technological efficiency was such that globally, for every US dollar spent we emitted on average 770 grams of carbon dioxide.
  • According to the UN’s mid-range estimate, the world’s population is expected to increase to 9 billion people by 2050.
  • To achieve the necessary emissions reductions, this would mean that by 2050 the efficiency with which we use resources would need to drop from 770 grams to only 40 grams of carbon dioxide per US dollar by 2050.

But this calculation assumes the world remains a very unequal place – developed countries getting steadily richer, China and India getting rapidly richer, and most of the rest of the world remaining crushingly poor. If we are serious about equality and wanted all of those 9 billion people to enjoy prosperity similar to US citizens today, then our efficiency would need to improve to 14 grams of carbon dioxide per US dollar – 55 times more efficient than today.

And this still assumes no income growth in developed nations. If we want an equal world where on average US citizens still get a little richer by 2050, then we must improve efficiency to the point where only a measly 6 grams of carbon dioxide are needed for each US dollar – this is 130 times more efficient than today.

If we dare contemplate population and affluence continuing to grow beyond 2050, well then every dollar of economic activity must actually take carbon out of the atmosphere!

These simple numbers – no more than primary school arithmetic – speak a stark reminder of how we must use our planet’s finite resources a great deal more carefully than we currently are. A sustainable and equitable world means a very different one from that in which we currently live.

(Image: View of the crowded, polluted Sao Paulo cityscape. Sao Paulo is the capital of the state of Sao Paulo in Southeastern Brazil and comprises an area of 588 square miles with a population over 11 million people. Image Credit: ©Scott Warren)

If you believe in the work we’re doing, please lend a hand.


  1. Good post! Crunching the numbers is, indeed, pretty scary, but also pretty informative.
    The most amazing thing the numbers say is about population. Worldwide, carbon emissions have more than doubled since 1970, from about 15 to 30 billion kilotons (as of 2006). Averaged out per person, carbon emissions didn’t change nearly as much — they first went over 4 tons in 1970, and they’ve fluctuated between 4 and 4 1/2 since. But at the same time, the world’s population nearly doubled, from about 3 1/2 billion to about 6 1/2 billion. The lion’s share of the increase was caused by population growth.
    Obviously, we need to reduce individual impact, especially in the U.S., with our outsized ‘footprint’. But we can’t overlook population’s role. Fertility rates in many countries have declined fairly rapidly when modern family planning is made readily available. We ought to do everything we can to support efforts to make it available everywhere.

  2. In 1985/86 I was in college and I did several research papers on this very thing. Even that far back I saw that we were in trouble with polluting the environment. A lot of promises were made by our government to reduce emissions in cars, factories and products that we use. Not many of those promises were ever kept. So now….25 years later we find ourselves in deep trouble and face the possibility that we cannot reverse what we have done and the consequences are dire. We need to do this as a nation. Cutting back on everything and paying attention to what we are using up. It will have to start with the common citizen if we wish to leave a decent world for our grandchildren.

  3. Definitely. Today, this statement, “A sustainable and equitable world means a very different one from that in which we currently live.” is truly a loud sound that almost everyone of us is trying to stifle and silence, as if we have no other better option. Why? Because we refuse to leave and live-out of our worldly monetary economic system. If we try to live-out of this, then all materials here in this world, including human beings, will lose their monetary value/cost, yet, retain their moral value, by virtue of the fact that we are all created by God and all other creations made by human beings are simply extensions of God’s attributes in each of us. If this is upheld, then money is no longer the bloodline of our economy. Instead, economic trading of goods & services based on “faith, hope, love or charity”, becomes the bloodline and should prevail, allowing goodness & Godness to prevail as well….

  4. ‎… and if we allow Godness to prevail, we stop abusing, over-using and endlessly producing, just to earn that money that makes our lives run & go…Today, without money makes us seemed helpless in dealing with our needs, concerns & problems. What if we really take out money from our lives? Doing this will make us not helpless anymore because this is no longer a necessity in order for us to live & solve our problems… We can do what’s necessarily good without wasting our resources…and have a world that’s better than what we have right now….
    a few seconds ago · Like

  5. Dear Eddie,

    Good work indeed! I read that write-up and thought that the scary math should be promoted among our communities as they become aware can realize that how can we change the world. Therefore, I shared it on my blog with the courtesy of The Nature Conservancy. I would be happy if you write some comments on my blog. Plz open the link below:

Add a Comment