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During the 1960s, when Drs. Paul Ehrlich and John Holdren were trying to anticipate the ultimate consequences of perpetual economic growth, they decided to try quantifying the process. Their intention was to give some mathematical figures to those economists who believed that a finite world could accommodate an indefinite expansion of production and consumption. The result was the Ehrlich Equation.

The equation is very simply written as I = PAT, where the impact of human economic activity on the planet (I) is equal to the size of the population (P), times its affluence (A) measured in dollars, times the technology (T), which is determined by the amount of carbon dioxide required to produce $1,000 of Gross Domestic Product. Given the efficiency of our present technology, 0.5 tonnes of carbon dioxide is required to produce each $1,000 unit of GDP. So, a global population of seven billion people with a level of affluence averaging $8,000 per person, we can compute their total impact to be 7x8x0.5 = 28 billion tonnes of carbon dioxide per year.

The equation works amazingly well because each of the components in the calculation can be adjusted to reflect changing circumstances. If the population goes up, together with its affluence, but the efficiency of the technology stays the same, then the carbon dioxide output will rise accordingly. Should the global population reach nine billion by 2050 with a doubling of average affluence because of the aspiration of developing economies, then the total impact on the planet will be 9x16x0.5 = 72 billion tonnes of carbon dioxide released annually into the atmosphere.

But we are now essentially certain that atmospheric carbon dioxide causes global warming and a host of related environmental problems. The pre-industrial level was 280 parts per million. Our current level is 389 ppm. This increase has produced a global average temperature increase in excess of 0.7 C, with at least another 0.2 C on its way as the carbon dioxide already emitted slowly overcomes the inertia of the planet’s natural ecosystems.

The global community has decided — with various degrees of hedging — that we should try to limit atmospheric carbon dioxide levels to no more than 450 ppm, in the hope that this will limit the average global temperature increase to 2.0 C. The best way we could be assured of not exceeding this 2.0 C threshold, however, would be to immediately stop all emissions and let the concentration fall to 350 ppm. But this is now physically and politically impossible. And even allowing a 2.0 C increase is risky because no one knows the temperature at which the warming will set in motion a positive feedback loop — melting permafrost releases methane that increases the warming that melts more permafrost that releases more methane. At this point, we lose control of climate change. The Dr. John Holdren mentioned above, who is now assistant to America’s President Obama for Science and Technology, describes 2.0 C as “the best we can do, while being the worst we can tolerate.”

If 450 ppm and 2.0 C is our target, then — to return to the Ehrlich Equation — by 2050 we will have to reduce the T factor in his I = PAT calculation from 0.5 to 0.1, a five-fold increase in the efficiency of our technology. Experts believe this might be “doable” given state-of-the-art design and unfailing political will. Unfortunately, this calculation does not allow for any increase in affluence, the Ehrlich Equation’s A factor.

Modern economics, however, is founded on the assumption of increasing consumption and affluence. This growth is a given in our present understanding of progress, and a “steady-state” economy is anathema to all traditional economic planning. While the five-fold increase in technological efficiency needed to stabilize the world’s temperature at 2.0 C does allow for an increase in population, it does not allow for any increase in affluence. If the present pattern of the world’s wealth were to increase at two to three per cent per year, and if China and India were to move forward at their usual rate of 5-10 per cent, then the T factor would have to become nearly 17 times more efficient than today, so that each $1,000 of wealth would have to be produced by 0.03 tonnes of carbon dioxide. If all nine billion people were to increase their affluence at 2.5 per cent per year, the T factor would have to be reduced to just two per cent of its present rate, or 0.01 tonnes per unit of wealth — 50 times more efficient than today. To accomplish this, our global economy would have to be almost completely decarbonized.

In the New Scientist article that outlines this argument (“I Shop Therefore I Am”, Oct. 18/08), Dr. Tim Jackson, professor of sustainable development at the University of Surrey and a member of the UK government’s Sustainable Development Commission, notes that “politicians will not admit that we have no idea if such a radical transformation is even possible.” But, as he says, we are not going to get there if we just “insulate our homes, turn down our thermostats, drive a little less, walk a little more.”

“Consuming less,” Dr. Jackson suggests, “may be the single biggest thing [we] can do to save carbon emissions, and yet no one dares to mention it. Because if we did, it would threaten economic growth, the very thing that is causing the problem in the first place.”

So this is our dilemma. Look at the numbers. Do the calculating. The Ehrlich Equation seems to be as valid as it was 40 years ago. The only thing that’s different is our room for manoeuvring.

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5. A New Measure of Global Warming From Carbon Emissions

Tags: Carbon Dioxide, Carbon Emissions, emissions reduction