This article is based on a 10 Nov 07 article in the Northwest Arkansas Times, where the author has a regular column that you can check out at http://physics.uark.edu/hobson/.
Winning the climate race
There’s a disconnect between our business policies and physical reality. We’re in a race with the reality of rising carbon dioxide (CO2) levels, but our policies don’t begin to reflect that fact.
From 12,000 years ago until 200 years ago, CO2 levels remained near 280 parts per million (ppm). This period is a warm period in the ice age cycles. The period from 130,000 to 12,000 years ago was a typical ice age, with average temperatures 5 Celsius degrees colder than the past 12,000 years. There have been many such cold-to-warm ice age cycles. Scientists drilling ice cores two miles deep into Antarctic ice have deduced that, during the past 650,000 years, CO2 levels were about 180 ppm during cold periods and 280 ppm during warm periods.
Beginning 200 years ago, CO2 levels have gone through the roof. Today’s level is 380 ppm, which is unprecedented not only in the past 650,000 years but probably in the past 20 million years. Driven mainly by fossil fuels, it’s increasing by nearly 2 ppm every year. Because CO2 traps the infrared energy that Earth radiates toward space, this is driving temperatures upward. Most people know by now that this is beginning to cause havoc, but our habits don’t yet recognize that fact.
James Hansen, NASA’s chief climate scientist, basing his reasoning on past ice core records, estimates that the climate system can tolerate a CO2 level of no more than 450 ppm (and perhaps less) before passing a tipping point beyond which the Greenland and West Antarctic ice caps, driven by the same kinds of feedback mechanisms (primarily albedo feedback and greenhouse gas feedback) that drove temperature rises at the ends of past ice ages, will begin to irreversibly melt. This could raise sea levels by several meters by 2100 and by several meters per century for many centuries thereafter.1 According to Hansen, if global warming reaches 2 or 3 degrees Celsius, as is predicted by the end of the century under business-as-usual, “we will likely see changes that make Earth a different planet than the one that existed for the past 10 millennia.”2
Quite literally, saving the planet has become the central moral problem of our time.
We are nearing that tipping point. The Arctic ocean is nearly half melted. Greenland, heated by a warmer Arctic ocean, is melting at its edges.
What would a viable global solution look like? To stay below the 450 ppm tipping point, we must radically and quickly reduce global CO2 emissions, by some 60 percent by about 2030. The only fair pathway toward this goal is one that converges toward equal per-capita emissions worldwide. Taking into account both the world population and the high current emissions in the industrialized world, this means that the rich countries must cut their emissions by some 90 percent by 2030.3
This is difficult but not impossible, as Britain’s George Monbiot shows in his fine book “Heat: How to stop the planet from burning.” He finds that the task is technologically doable and economically feasible–certainly more feasible than the failed economy resulting from continued warming. Here’s how.
First, we must plug our leaky homes and businesses. For example, with tight insulation and south-facing glass, “passive” homes–having no heating or cooling systems–in Germany achieve average indoor temperatures of 70 degrees during the cold German winter. All new homes must meet similar standards.
Second, the utility industry must reduce emissions by promoting energy efficiency, switching to renewables, and burying the remaining CO2. Efficiency is the “low-hanging fruit” of the energy business; for example, it’s far cheaper to warm a house with insulation than with gas or electricity. Monbiot’s careful study of energy from wind turbines, photovoltaics, “solar thermal” (sunlight focused onto a fluid that then generates power plant steam), and energy storage shows that half of utility-supplied energy could come from renewable sources. The remaining half could come from coal- or gas-burning plants whose CO2 would be compressed and pumped safely and permanently underground.
Third, we must reform our pathological transportation system. Monbiot notes that transportation “should be easier to solve than the other problems…. Far from costing more money, a rational, efficient system, producing 10 percent of current emissions or less, would save us billions. But the real problem is neither technological nor economic. It is political or, more precisely, psychological.”
Monbiot recommends a mix of transportation strategies. Eighty percent of car travel should be replaced by walking, bicycling, and buses. Driving should be discouraged by capping and rationing highway space, taxing automobiles and fuel, and removing our enormous driving subsidies. He condemns widespread use of biofuels because they consume too much agricultural land, argues that fuel cells won’t be widespread for 25 years and are therefore irrelevant to reductions by 2030, and finds that hydrogen has severe drawbacks. The car of the future is an ultra-efficient, lightweight, hybrid or plug-in hybrid. Up to 500 miles, air travel should be replaced by high speed trains that will get us there faster. Long air trips must be greatly curtailed.4
Social inertia will probably prevent the industrialized nations, and the United States in particular, from achieving a 90 percent reduction in emissions by 2030, although there is some realistic hope that we might achieve it by 2050. Thus, the planet is likely to be skating on very thin ice after about 2030.
References:
- James Hansen with 5 co-authors, “Climate change and trace gases,” Philosophical Transactions of the Royal Society A, Vol. 365, pp. 1925-1954 (18 May 2007).
- James Hansen with 46 co-authors, “Dangerous human-made interference with climate:a GISS modelE study,” Atmospheric Chemistry and Physics, Vol 7, pp. 2287-2312 (2007).
- George Monbiot, Heat: How to stop the Planet from Burning (South End Press, Cambridge MA, 2007), p. 16.
- Concerning travel to APS and other meetings, see Benjamin Lester, “Greening the meeting,” Science, 5 Oct 2007, pp. 36-38.