We’ve all heard of global warming (or rather, global climate change). But what hadn’t really been factored into the equation before (or at least I had never heard it mentioned) is an opposite effect, also caused by – guess who – us. That effect is called “Global Dimming,” and it pulled the rug out from under my already tenuous sense of safety (what was left after digesting the reality of global warming).
What is “Global Dimming?” Well, I’d highly recommend the NOVA program that I watched, as it gives an excellent summary of the discoveries leading up to, controversies surrounding, and implications of this thing called global dimming. You can watch the episode in its entirety through Google Video (well worth the 48 minutes):
But for those of you who don’t have time or interest (here’s a second chance: go back and watch the video!), here’s the basics. Man-made air pollution (the kind made of tiny particles, not just CO2) has the effect of reflecting the Sun’s light back into space before it gets a chance to be absorbed by the Earth. Previous to recent studies featured in the NOVA program, it was thought that man-made particulate air pollution reflected .5% to 1% of the Sun’s light back into space. As such, it would have been a relatively minor effect.
Recent studies, however, painted a very different picture. It turns out that man-made particulate air pollution reflected 10% of the Sun’s light hitting the Earth. Folks, that is a huge amount. Smaller variations in albedo (the scientific term used to describe how much light a planet reflects), have produced climate variations as extreme as Mars (cold) and Venus (extremely hot). So why haven’t we heated up like a pot on a stove, or iced over?
Walking the Climate Tightrope
It turns out that Global Dimming and Global Warming are fighting each other (metaphorically) for the fate of Earth’s climate. Global Dimming is reflecting a tremendous amount of the Sun’s light, which has a strong cooling effect. Global Warming (more specifically, the accumulation of CO2 in the Earth’s atmosphere) is absorbing a great deal of the energy from the Sun and trapping it in Earth’s atmosphere, which has a strong warming effect. That means that our current climate is the result of a precarious balance between two destabilizing climate forces.
So, here’s where it really hits home. We’ve all heard about Global Warming for years, and how it’s supposed to be this terrible thing that raises sea levels 100 feet above their current levels. Yet we’ve seen very little change (even less than what climate models would predict even over a short period of time). This has, of course, led to global warming deniers to shout “Aha! See, there’s nothing to worry about!” and place the very real scientific question of global climate change in the hands of politicians. But this lack of extreme climate changes might be deceptive.
Global Dimming is masking the true magnitude of Global Warming. As the NOVA program illustrates, the day that all U.S. air traffic was grounded on September 11, 2001 saw a tremendous increase in the magnitude of change in temperature that very day. And when air traffic resumed three days later, it dropped back to its previous level. And this was just one country’s air traffic. As environmental standards call for cleaner air standards to improve health and lessen environmental impact, the real severity of Global Warming is beginning to show.
What will happen when air quality conditions improve even further? We’ll probably get a taste of the real immediate threat of global warming that we have yet to encounter. And I’m betting it’s going to be drastic enough to silence all but the most fringe Global Warming deniers . . . unfortunately, it might be at the cost of humanity’s future long-term survival.
Until next time, bonnes pensées.