The Annual Energy Forum recently hosted by MSU outlined the challenges of keeping carbon out of the atmosphere while supplying the energy people demand at prices they’re willing to pay. I came away convinced that geoengineering, i.e., the deliberate modification of the Earth's environment, will receive ever more attention as the steep and unavoidable costs of mitigating carbon emissions become more obvious. Here’s why.

Coal accounts for 37 percent of global emissions of CO2, a potent greenhouse gas. World reserves of coal are enormous, and are widely distributed around the globe; almost half of the proved reserves are in OECD countries. (The U.S. has a 25 percent share.) The world has enough economically recoverable coal that, at current rates of consumption, it will last 200 years—far beyond the thinking of most policymakers.

Demand for electricity is growing, with most coming from developing countries. Coal will be their fuel of choice. Why? Because it’s both abundant and cheap. China uses it to fuel the rapid economic growth that is lifting millions from poverty. (China recently surpassed the U.S. as the world’s largest CO2 emitter and is exempt from the requirements to reduce emissions under the Kyoto treaty.)

The Chinese, however, are discovering the heavy environmental and economic toll of fueling their economy with coal. Coal is a dirty fuel and China suffers massive environmental and health related problems. Of course, air pollution does not respect international boundaries. The Journal of Geophysical Research documents how Asian air pollution may make it hard for western states to meet the goals set by the Clean Air Act.

Unfortunately, there aren’t good, easy alternatives for replacing coal anytime soon. The fastest-growing non-fossil fuels—wind and solar power—are expected to climb an average of 10.5 percent annually. But by 2030 this will represent only about 1 percent of global energy demand. Renewables such as hydropower, wind, and biofuels face similar challenges. They just aren’t capable of providing the energy, in a dependable manner and on a large enough scale, to meet base load generation demands. Nuclear is the one option that can make a difference. But just to hold its current 20 percent share of the U.S. energy market, dozens of new plants will have to be built in the next two decades.

Technologies for capturing and storing (sequestering) CO2 underground are in the works. But they face hurdles, both technical and political. The basic technology is at least a decade away. While scientists and engineers work this problem, policymakers face another. They must create the institutions that will provide incentives to sequester huge amounts of CO2 for a very long time.

For example, who is liable if sequestered CO2 leaks into the environment? (In high concentrations CO2 can be lethal.) Who is responsible for assuring the CO2 stays underground? What happens if it acidifies groundwater flowing into trout streams? In short, a host of legal and regulatory policies must be addressed. Some can be modeled on existing regulations that have been successfully used for decades by the oil and gas industries. Others must be created from scratch.

There is some non-zero probability of abrupt (i.e., over a decade or two) and catastrophic damage (e.g., a disruption to the Gulf Stream) from climate change, but no consensus on the odds. This is too short a time period to mitigate the damages through reduction of CO2 emissions alone. In this case, geoengineering is an alternative that may be useful, even essential.

Adding limestone to the pH-sensitive lakes in the Adirondack Mountains of New York to buffer the affects of acid rain is an example of geoengineering. This is a stopgap measure that ameliorates, but does not address the underlying cause of the problem.

Regarding climate change, a geoengineering fix, e.g., pumping sunlight reflecting sulfur particles into the atmosphere, might prevent abrupt and catastrophic climate change. (We’ve had several experiences with the cooling effect of atmospheric sulfur. In 1815, the eruption of Mount Tambora caused 1816 to be labeled the “year without summer.”)

Stabilizing current atmospheric concentrations of CO2 requires a 60 to 80 percent cut in global emissions. Absent a global economic collapse, this will not happen.