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The World-Changing Power of Efficiency

This article was written by Jamais Cascio in June of 2005. We're republishing it here as part of our month-long editorial retrospective.


Not a spy thriller, the Kaya Identity is the formula which projects the amount of atmospheric CO2 as a function of population, GDP per capita, watts per dollar, and CO2 per watt. It's pretty straightforward: our carbon output depends on how much power we use, how efficiently we use it, and how "dirty" the production is. Recall that current atmospheric carbon dioxide levels are just under 380 parts per million, and that the general consensus among climatologists is that (looking just at CO2), the climate is up for some serious problems once we hit the 440ppm level. With the Kaya Identity, we can calculate just what combination of factors would keep us below that level.

The math isn't hard -- it's just multiplication -- but charting it out over course of the next century can get a bit tedious. Fortunately, for a class in the Geosciences department at the University of Chicago, Professor David Archer put together a Kaya Calculator allowing you to plug in preferred figures for each element and see what results. For most factors, you don't have to give absolute numbers, just the amount of change every year. The calculator is set to show the results over the course of the 21st century, and displays a number of graphs detailing the figures. The most important of the resulting graphs is "Carbon-Free Energy Required for CO2 Stabilization" -- that is, how much of our overall energy production will have to be carbon-free in order to stabilize CO2 at a given portion by 2100.

With the default figures -- taken from the global trends of the last century -- we'd need over 17 terawatts of carbon-free power (out of the total produced) to stabilize at 450ppm in 2100. I've reproduced the graph showing these results above. Unfortunately, the chart doesn't indicate just what the total energy production would be; the Intergovernmental Panel on Climate Change (IPCC) can help here -- their average scenario for energy use in 2100 is roughly four times the present, or about 40-50 terawatts.

But that assumes we don't try to change things.

As this Real Climate article (from which I found the Kaya Identity calculator) suggests, getting to 17 terawatts of carbon-free power is staggeringly difficult. But that's with the default value of an 1% annual average improvement in efficiency; this improvement is largely a side-effect of overall changes to technology. If we give greater attention to increasing efficiency, we can have enormous payoffs down the road.

Efficiency is a funny thing; over time, small improvements can have dramatic effects. Globally, our overall rate of annual improvement in efficiency is about 1% for the last century; that is, each year we can produce about 1% more GDP per Watt consumed than the previous year. But (as we've noted before), that 1% figure doesn't tell the whole story. Improvements in efficiency have been much greater than that for some regions and for some periods of time. For example, between 1981 and 1986 (the early 80s oil shock), the United States managed annual efficiency improvements averaging 3.4%; over that same time period, California improved by 4.5% every year. Average annual improvements for both fell back to around 1% between 1986 and 1996, but jumped again in the late 1990s (2.7% for the US and 3.9% for California) -- probably reflecting the economic shift away from heavier industries and towards less energy-intensive businesses.

twopercent.jpgSo -- without changing any other values -- if we alter the Watt/$ reduction box in the Kaya Calculator from -1% to -2%, something very interesting happens. Instead of needing 17 terawatts of carbon-free power to stabilize at 450ppm in 2100, we'd need 4 TW. That's not 4 terawatts out of ~50, either; that's 4 TW out of about 18 TW, because the boosted efficiency has reduced the overall consumption.

And let's look at what happens when we go to -3% annual change, a figure still below what the US managed in the early 1980s, and well below California at that time. Stabilizing at 450ppm would require... no carbon-free energy. How's that possible? Because global energy consumption would have dropped to about 7 terawatts, or around half of current consumption.

threepercent.jpgOf course, peak oil and the need to move swiftly to reduce CO2 output won't let us forget carbon-free power. But look again at the 3% result: we could possibly stabilize at 350ppm -- a far safer CO2 load than 450ppm -- by adopting 4-6 terawatts of carbon-free energy along with the more aggressive efficiency (the 6 TW peak in 2050 reflects the more limited effect of efficiency at that point). Actually being able to reduce atmospheric carbon would undoubtedly mean increasing carbon sinks and relying on some forms of sequestration, but a dramatic reduction in the amount of CO2 put into the atmosphere helps enormously.

Art Rosenfeld and John Wilson of the California Energy Commission refer to this as the "Conservation Bomb;" the chart below comes from a presentation John Wilson provided to me. It's a graphic representation of what I've been talking about above: the difference in energy consumption under different efficiency improvement scenarios. Two elements stand out: the first, that a 4% improvement would bring us down to about 3 terawatts -- again, a rate of improvement not without precedent; the second, that the total energy demand is predicated not on the status quo of rich nations/poor nations, but on a global population of 10 billion all with EU-equivalent lifestyles.


An aggressive focus on improvements to efficiency amounting to an average of 3-4% annually over the century could mean a world where everyone can live well without risk to the climate. To say that the effect of improving the efficiency of use is dramatic is perhaps an understatement. Without it, avoiding disastrous greenhouse effects will be nearly impossible; with it, avoiding the worst-case scenarios is almost over-determined.

Efficiency is quite literally world-changing.

This piece is a part of our month long retrospective leading up to our anniversary on Oct. 1. For the next four weeks, we'll celebrate five years of solutions-based, forward-thinking and innovative journalism by publishing the best of the Worldchanging archives.

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