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There is a useful equation to measure a given environmental impact. Let’s look at greenhouse gas (GHG) emissions. These are usually measured in units of CO2e which stands for carbon dioxide equivalent. This allows us to convert gases like methane with 28 times the warming impact of carbon dioxide to a common unit that has been tracked for some time. In words, the equation is:

Impact   =    Population    *    Affluence     *     Technology                               (CO2e)          (people)        ($GDP/person)      (CO2e/$GDP)

So there are three factors that we can simply multiply together to get total emissions for a region. Let’s look at each factor separately.


The top eight countries by population are:

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Just these eight account for more than 50% of the world population. Note also that every one of these countries is expected to keep growing. The UN projects that the world will increase from 7,200,000,000 people in 2014 to around 10,000,000,000 within the next 80 years or so. Projections are notoriously uncertain, but most estimates expect population to grow.


Affluence is measured by taking a region’s total GDP and dividing it by population. The World Bank has done this for each country. Below is a summary of our high population players:

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The eight most populous countries vary dramatically. The average US person corresponds to 65 times the GDP of someone in Bangladesh. While GDP is not an indicator of well-being, it is a convenient way to estimate resource use. Affluence is trending upwards in all eight countries. Our current economic system is based on perpetual growth, which might be a fatal flaw.


The last factor is a measure of how much useful work ($ GDP) we can get in exchange for something detrimental (kg of CO2e).

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China has a notably high emissions per dollar rate, and that’s partly because they use so much coal. But think about it another way and they produce many of the wealthy countries’ products. This means that countries like the US that are actually demanding the products are responsible for at least some portion of the Chinese rate.

Europeans seem to be more efficient than Americans, so there is room for the highest emitters to reduce their impact without impacting lifestyle. Furthermore, new technologies promise a gradual improvement in some sectors like electricity (from wind, solar, and nuclear).


So now we put it all together. Just multiply each factor and convert the units to a manageable result:

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The units here are megatons of carbon dioxide equivalent, but don’t worry about that. We’re concerned more with which countries to watch in the future. Of course, to make better guesses, we should look at historical growth rates in each factor and we will in a later post. But these estimates show that the US and China are nearly neck-and-neck responsible for the lion’s share of emissions between them. Other countries (eg. India) might soon grow to match the top two, and a meta-region like the European Union certainly would rank if we combined the impacts of its member countries.

This explains why some politicians in the US claim it’s useless to pass carbon legislation. Either China or the US (or the EU) acting alone to reduce emissions means failure. In the mean time, we can work on improving our energy use (reducing the technology factor) and by promoting family planning (reducing the population factor) especially in already wealthy countries.