A new ice age (1)

The environmental panic of the 1970s was the coming Ice Age. It was based on apparent evidence of just two decades of worldwide cooling together with a 1971 article in Science that suggested that an increase in atmospheric aerosols – such as sulfur dioxide and particulate matter emitted by diesel engines and coal fired power plants – would provide enough cooling to trigger a new ice age.

The two decades of global cooling was overestimated, and the trend was soon reversed, while the science was just plain wrong. At that time, no one understood the extent that other atmospheric constituents, such as methane, contribute as much to planetary warming as does carbon dioxide. Meanwhile the industrialized West has successfully cleaned up much of the sulphur and particulate emissions so their cooling effect is largely lost.

The Earth appears to be in a cycle of ice ages followed by warm periods. It is also true that, all other things being equal, we could expect another ice age sometime in the near – at least by geological standards – future. It is true, as well, that Earth's orbit lies outside the "habitable zone" around the sun where, absent other influences, liquid water can exist.

But all other things are not equal and human impact on our planet has certainly postponed the onset of the next ice age - perhaps for ever.

First, the invention of agriculture led to more and better food. The result was an increase in population followed by deforestation to provide additional arable land. As a result, more CO2 was released. Then, the domestication and spread of cattle, sheep, and goats for labor, milk, and meat increased the amount of methane released into the atmosphere. Finally, in the three hundred years since the beginning of the Industrial Revolution, the ever increasing consumption of fossil fuels – coal, oil, natural gas – has increased the load of heat retaining gases in the atmosphere to levels not found in the last 650,000 years.

Studies of Antarctic ice cores show a remarkable correlation between temperature and atmospheric CO2 levels so, unless we do something - but not too much, it looks like we are in for a hot one!

More tomorrow.