One of my main interests is how much impact we as a species are having on the natural systems of the planet. Earlier this week I took a shot at quantifying the impact using the I=PAT equation. I encountered some severe objections :-) to the proxy I chose for “Technology”, so I decided to back up and take another run at it.
This time I decided to use constant dollar global GDP for the Affluence term. This has a number of advantages: it’s easy to accept as a coarse measure of affluence; the data is readily available, and it already contains the population term.
This time for the technology term I started with what’s called the “Gross Capital Formation” or GCF portion of global GDP. The definition of GCF (insofar as a non-economist can understand it) loosely amounts to the portion of GDP that is spent on goods alone, i.e. fixed assets and increases in inventory. The data is available from the
World Bank. Since most of the planetary impact is caused by the production of goods rather than services, I used this measure as a base for the technology indicator, and total GDP as the affluence component.
I used GCF along with total CO2 produced (from BP’s Statistical Review of World Energy 2010) to generate the final Technology or T factor: the amount of CO2 generated per dollar of goods produced. This takes into account both changes in energy intensity (the amount of energy used to produce a dollar's worth of goods) and the shifting technology base of the primary energy used. The rationale is that as energy intensity improves and carbon intensity declines, the T factor decreases, resulting in less environmental impact for each dollar of GDP produced.
I calculated the impact by simply multiplying GDP by T. This generates a term representing human affluence (or activity) adjusted by a factor that takes into account improvements in energy efficiency and changes in the carbon intensity of the energy we use.
I had GCF figures from 1970 to 2008, so I used that period as an initial sanity check.
From 1970 to 2008, world population increased by 210%, global GDP increased by 320% and the technology factor declined by 35% (meaning we generate 35% less carbon to make a dollar’s worth of goods than we did in 1970.
Due to the significant rise in GDP over the period, the Impact figure (GDP x T) rose by 180%. As expected this was less than the 210% growth in population. This implies that if we can stop our population from growing we could likely get our impact on the planet to level off or decline as well.
What this says about our impact relative to that of our prehistoric forebears I won't speculate (yet). One of the complicating factors will be to determine an appropriate impact proxy related to goods production when the energy source is wood rather than fossil fuel. I do have Angus Maddison's estimate for world GDP in year 1, so it will be interesting to use that for a longer time base.
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