An article in this month’s Scientific American titled "Impact from the Deep" has prompted me to write my first article on global warming. I avoid the topic because it is already covered practically every day by other commentaries. The article posits a theory that chronic and heavy volcanic activity caused some of the mass extinctions of the past, explaining how it happened along with some supporting evidence.

Today, we don’t have thousands of volcanoes spewing forth massive amounts of CO2, but what we do have are billions of point sources of CO2 emissions. To give you a feel for the magnitude of our oil, coal, and gas burning, think back to the Gulf War and the thousands of oil wells that were set on fire. Look at that picture for a moment and ponder that cars in the U.S. alone emit five times more CO2 per day than those fires did at their peak — and our coal- and gas-fired power plants emit twice as much as our cars.

The author, Peter Ward, is a professor at the University of Washington, which is about a mile from my house. I first encountered his writing in a book with the sensationalist title Gorgon: Paleontology, Obsession, and the Greatest Catastrophe in Earth’s History. I wrote a less-than-glowing review of it here on Amazon.

The article tells us that, although meteor impacts have probably caused some of the major extinction events, global warming may have caused the others. The sequence of events being as follows:

CO2 concentrations were increased by chronic volcanic activity. The CO2 caused global warming. The extinction of most life, including plants, was the result of poisoning from sulfur gases combined with destruction of the ozone layer. The source of the sulfur was anaerobic microbes in seas too warm to absorb enough oxygen to keep them at bay. Essentially, the oceans, the engines for all life on Earth, had become giant dead zones for all oxygen-dependent life forms.

The Black Sea is an example of a large body of water where sulfur producing anaerobic microbes dominate the lower half of the water column. Ancient wooden ships that sink to the bottom of the Black Sea remain preserved after thousands of years. Unlike the oceans, there are no currents to stir oxygen into the lower depths, which is toxic to anaerobic microbes.

Now, this is just a theory, although one supported by varying degrees of evidence discussed in the article. But what bothers me is the fact that dead zones, areas in large bodies of water that are oxygen-starved and therefore devoid of oxygen-dependent life, are showing up all over the world and are growing in size:

The U.N. report estimates there will be a 14 percent rise in the amount of nitrogen that rivers are pumping into seas and oceans globally [via agricultural run-off]over a period from when the levels were measured in the mid-1990s to 2030

Could we be seeding a future anaerobic domination of the oceans? Global warming isn’t the only human activity unraveling the fabric of life on this planet; we need to keep that in mind. Lesson to be learned: don’t support every idea that comes along to decrease CO2 emissions, especially if that idea degrades the biosphere in other ways.