IPAT and the End of Growth

In the early 1970s Ehrlich and Holdren devised a simple equation in dialogue with Commoner identifying three factors that created environmental impact. Thus, impact (I) was expressed as the product of (1) population, (P); (2) affluence (A); and (3) technology, (T):

I = P * A * T

Population is the number of people on the planet, affluence is measured in GDP per capita, and technology is environmental impact per GDP. When looking at the growth rates of each I, P, A, and T the formula changes towards this form:

dI = dP + dA + dT

In order to see how the impact changes from one year to the next one, you just have to sum up the changes in population increase, affluence, and technological progress. Technological progress can best be understood here as a change in intensity. So if the environmental impact of choice is CO2 emissions, the T you are looking for is carbon intensity: “Carbon intensity is a measure of how much carbon economies emit for every dollar of GDP they produce.” Improvement here means lower carbon intensity and the change rate is the decrease in carbon intensity dT.

When we average the population increase to the median level of 9 billion people at 2050, we can assume dP to be around 0.5% each year until the middle of this century. The desired dA, the growth in GDP per capita, is 3% each year. The average improvement (decrease) in carbon intesity globally was around 1.9% each year. If we ignore any possible changes to all these numbers in the future we can calculate the annual change in carbon emissions (dI) as

dI = 0.5 + 3 – 1.9 = 1.6% more carbon emissions each year

So in order to not increase carbon emissions, we would have to decrease carbon intensity – via new engine technologies, new forms of energy creation, maybe carbon capture and storage – at least by 3.5% each year. That implies almost an instant doubling of our technological efficiency as regards CO2 emissions. There is no immediate technological solution that could produce this result. The later we do it, the higher the reductions in carbon intensity would need to be. And we are not talking about reducing emissions in total, just to keep the emissions at the same level as today. In order to reduce emissions we need more than 3.5% decrease in carbon intensity. If we want to stick to the 2C-guardrail in temperature increase until 2100, the global economy would need to be emission-free from 2050 onwards. The math is simple: it requires a six-times increase in carbon efficiency each year to reach zero by the middle of the 21st century. Tomorrow. Not in 10, not in 20 years.

From the very simple IPAT equation it is clear, that with a fixed increase in affluence, no environmental goal can be met. Of course there is no consensus up until this day to reduce affluence increase i.e. reduce global growth of GDP per capita. If dA would be below 1% each year, the task would however look much more doable. Of course 1% as a global aggregate would imply degrowth in the global North with, say -0.5 to -1.0%, a steady state development in countries like China and Brazil, and a positive growth rate in the rest of the global South between 4 and 5% maybe. Such a policy would alleviate poverty by 2050 largely and allow the World economy to stay within planetary ecological boundaries.

This policy will not be enforced now. But it will be enforced in a couple of years. The reasons for this are pretty easy regarding the maths of a finite planet. We are overshooting planetary limits by about 50% today, meaning that we would need half of another Earth to satisfy our present consumption levels. So the numbers in the IPAT equation above will not unfold in reality, the development will hit the walls. Paul Gilding calls this the “Great Disruption“. Decrease in crop yields and fishery, increase in food and resource prices will send shockwaves through the global economy, producing even greater financial collapses as we seen in 2008 and 2009. And this will also have geopolitical consequences. There is no “away”. There is no second Earth. We will have to deal with this here and now. At one moment in time, the IPAT equation has to and will change its numbers. The sooner we do it voluntarily with political and economic measures, the easier the transition will be. And with less misery, tears, and blodshed. But regardless, the era of economic growth as we knew it is over. It is simple as math and the numbers add up quite badly.

4 Replies to “IPAT and the End of Growth”

  1. Odd formula. GDP is GDP. Affluence is affluence. GDP is no great indicator of affluence. It goes up in Britain for example simply by feeding new money into corporations and transferring wealth to the wealthy. At best an illusion of affluence.

    Having GDP in both numerator and denominator of the same side of the equation just cancels it out. So the equation is really saying total impact=impact x population, which is no great leap?

    You seem to argue against the possibility of a 3.5% increase in carbon intensity. This means no politician can be expected to believe this is possible. Surely the point of us eco-researchers is to firstly demonstrate possibilities that match the scope of the problems and secondly to show policy options to do it?

    Overshooting planetary limits is not news. World leaders have known this since 1972. Massive ecological impacts are not news. Why would we think that this information will bring a change of political mind “in a couple of years”? With BAU, more likely we’ll get global economic collapse and game-over for politics.

    2C is no guardrail, it’s a political dodge to avoid action. See http://www.apollo-gaia.org/CoR%20Keynote.pdf David Wasdell shows that the science tells us we need as close as possible to immediate 100% reduction in carbon intensity. As a starting point!

    Dialogue about how to make this possible is needed but first we might need to turn up our imaginations and see that economic growth involves choices beside just choosing to end it.

    1. The formula says Impact = Impact. P is Population, A (Affluence) is GDP/Population, T (Technology) is Impact/GDP. It is a very simple equilibrium equation to make sense of the most common economic policy impacts. The links I provided will give a fairly good overview of IPAT, its creation and its history.

      What I am arguing against is the naive belief that growth will save us. It won’t. You can very easily show with the IPAT equation that the race cannot be won unless you stick to growing affluence by growing GDP.

      I totally agree that GDP does not measure affluence beyond the mere monetized, materialist side of it. And I also do not doubt that we would have to substract parts of it that are used to clean up social and ecological collateral damages. However as you know, I don’t argue over GDP as any new indicator will most likely be as distractive from what matters and fails to acknowledge the logical fallacies of growth, be it GDP, happiness or otherwise.

      Policy suggestions are, I believe, not our disagreement. I am arguing, similar like you, for a truly circular economy (equally not new news by the way), with a dedicated focus on collaboration and peer production. We might even invent the term collaborative peer re-production if Michel Bauwens hasn’t thought of that yet. The more circular the flow of material and whole products/components will be, the less will be needed to be produced and sold anew. The more a collaborative mode of production will be supported (which is great for things like urban renewal or strengthening economically weak regions in a country), the less need for growth, the more we get an interesting mix between industrial supply chains of today and subsistency networks on a local or translocal scale. This exciting for policy makers as they can get results on the ground were people, it is excited for activists because things are getting implemented, and it is exciting from a theoretical perspective as we can witness societal change firsthand.

      But with growth and its entire mental infrastructure, the trajectories and deadlocks it brings, I am done 🙂

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