Go to the Globe and Mail homepage

Jump to main navigationJump to main content

Jeffrey Simpson (Bill Grimshaw)
Jeffrey Simpson (Bill Grimshaw)

Jeffrey Simpson

Climate change is not weather change Add to ...

At a reception a few weeks ago, a senior minister in the Harper government stated as fact that the atmosphere was cooler today than in 1998, the inference being that climate change was a hoax, or at least not what it's cracked up to be. It's scary to have a senior minister believe such stuff, but this is the Harper government, after all.

As the Copenhagen climate talks open, there's lots of bogus science around. So perhaps it's worth reviewing again what the overwhelming number of scientists around the world and across Canada are saying today.

A document called the Copenhagen Diagnosis spells out where we're at. (The report was compiled by 26 scientists from seven countries, including Andrew Weaver of the University of Victoria.) It makes the point - so elementary it scarcely bears repeating - that a distinction exists between weather and climate. Weather is short term - today, tomorrow, this month - whereas climate is the underlying, long-term pattern, year after year, decade after decade.

Climate change is not weather change. The weather oscillates all the time; climate changes very slowly. Within that slow change are innumerable variations, but what counts is the underlying pattern. Today, for example, might be cooler than yesterday. So what? And 2008 was cooler on average than 2007. Why? Because a La Nina occurred in 2008, causing a temporary dip in average global temperature. (Despite La Nina, 2008 was the ninth-warmest year on record.)

An El Nino occurred in 1998, the reason for the Harper minister's confusion, that warmed temperatures. They naturally fell thereafter before resuming their upward rise. What counts is that for the decade from 1999 to 2008, average temperatures rose 0.19 Celsius, within the long-term forecasts for global warming of most of the world's atmospheric scientists. NASA, for example, predicts decade-over-decade increases in the range of 0.17 and 0.34.

There may be other short-term factors at work. There can be massive volcanic eruptions that can cause temporary cooling. There is a well-known pattern of solar variability whereby less sunlight for a few years has a cooling tendency. But, as the Copenhagen Diagnosis authors write, "neither El Nino nor solar activity nor volcanic eruptions make a significant contribution to long-term climate trends." Long term for most atmospheric scientists is a minimum of 25 years.

The atmosphere is generally unfolding - that is, warming - much as a series of United Nations reports have suggested, each providing increasing levels of scientific assurance, although couched with the qualifications one would expect from projections.

In one area, however, matters have moved faster than expected. The Arctic is warming and losing its ice cover more rapidly than scientists had expected a decade ago. As the authors of the Copenhagen Diagnosis say, "perhaps the most stunning observational change … has been the shattering of the previous Arctic summer minimum sea ice extent record, something not predicted by climate models."

In Canada's northern backyard, therefore, the effects of global warming are as evident as anywhere on the planet. An ice-free Arctic summer is inevitable if warming trends continue. Whereas it was thought this ice-free situation might occur in a hundred years, new studies suggest it will happen in 30 years, or less.

An Arctic cycle will thus develop: Less ice means warmer surrounding land, which means more melting, which leads to the rapid release of carbon storied in the previously frozen land, which means more carbon, and so on. Sea levels will also rise faster, because ocean water expands as it heats and melting on land produces water that flows into the oceans.

All this, and more, is known to governments around the world. There isn't a single government represented at Copenhagen that rejects human-made global warming, although a few are eager to seize on anything that might cast doubt. Among these, as you would expect, are Saudi Arabia and a few other petroleum-producing states that will be severely threatened long term if the world reduces its dependence on fossil fuels.

Even Ottawa and Alberta, hardly paragons of climate-change policies, admit the science. Doing something about it remains another matter, at home and abroad.

Report Typo/Error

Follow us on Twitter: @GlobeDebate

Next story




Most popular videos »

More from The Globe and Mail

Most popular