Evidence has mounted that global warming began in the last century and that humans are, at least in part, responsible. The concern is that the warming of our climate will greatly affect its habitability for many species, including humans. Both the Intergovernmental Panel on Climate Change (IPCC) and the U.S. National Academy of Sciences concur that this is the case. But some argue that this thinking is too limited. They say that too many scientists are either ignoring, or don't understand, the well-established fact that Earth's climate has changed rapidly in the past and could change rapidly in the future—in either direction.
Evidence for abrupt climate change is readily found in ice cores taken from Greenland and Antarctica. One of the best known examples of such an event is the Younger Dryas cooling of about 12,000 years ago, named after the arctic wildflower found in northern European sediments. This event began and ended rather abruptly, and for its entire 1000 year duration the North Atlantic region was about 5°C colder. Could something like this happen again? It sure could, and because the changes can happen all within one decade—we might not even see it coming.
The Younger Dryas occurred at a time when orbital forcing should have continued to drive climate to the present warm state. The unexplained phenomenon has been the topic of much intense scientific debate, as well as other millennial scale events.
The period of these shifts are related to changes in the tilt of Earth's rotational axis every 41,000 years, changes in the orientation of Earth's elliptical orbit around the sun, called the "precession of the equinoxes" (23,000 years), and to changes in the shape of the elliptical orbit, which occurs every 100,000 years.
The theory that orbital shifts caused the waxing and waning of ice ages was first pointed out by James Croll in the 19th Century and developed by Milutin Milankovitch in 1938. Milankovitch dedicated his career to developing a mathematical theory of climate based on the seasonal and latitudinal variations of solar radiation received by the Earth. Now known as the Milankovitch Theory, it states that as the Earth travels through space around the sun, cyclical variations in three elements of Earth-sun geometry combine to produce variations in the amount of solar energy that reaches Earth.
Ice age conditions generally occur when all of the above conspire to create a minimum of summer sunlight on the arctic regions of the earth, although the Ice Age cycle is global in nature and occurs in phase in both hemispheres. It profoundly affects distribution of ice over lands and ocean, atmospheric temperatures and circulation, and ocean temperatures and circulation at the surface and at great depth.
Since the end of the present interglacial and the slow march to the next Ice Age may be several millennia away, why should we care? In fact, won't the build-up of carbon dioxide (CO²) and other greenhouse gasses possibly mitigate future changes?
Much of the current thinking about global warming is flawed according to Terrence Joyce, Senior Scientist, Physical Oceanography and Lloyd Keigwin, Geology & Geophysics at the Woods Hole Oceanographic Institute: It ignores the well-established fact that Earth's climate has changed rapidly in the past and could change rapidly in the future. The issue centers around the paradox that global warming could instigate a new Little Ice Age in the northern hemisphere.
The Daily Galaxy asked climate expert Thomas Reichler, Department of Meteorology at the University of Utah, what he has to say about it. According to him, anyone claiming that the Earth isn't getting warmer, or that it's perhaps even getting colder, simply isn't looking at the actual data.
"There is absolutely no doubt that the world is in a warming phase," Reichler told the Daily Galaxy, "and that conclusion is supported by 99% of all serious scientists, so I'm certainly not alone in that certainty."
Reichler is probably right, but it wouldn't be the first time if the fringe opinion turned out to be onto something. But from a broader perspective, does it really matter who's "right" as far as preparations go? Whether the climate gets cooler or warmer, or does nothing at all, people will still need massive amounts of energy. Even if we were to take the reverse approach and intentionally increase greenhouse gases in the atmosphere in order to stave off cooling, it would likely have little effect other than to further pollute the environment with standard energy consumption's many toxic byproducts.
Are humans the major factor in the current warming trend? Maybe, maybe not. But what can't be disputed is that humans are polluting the planet. Current and future weather conditions do not change the fact that using oil and coal for energy isn't a good long-term idea. The need for cleaner energy, cleaner air and cleaner water has never been greater. The widespread call for better handling of resources, and habitat protection doesn't change with the thermometer.
Our commitment to stop polluting our water systems with pesticides and other dangerous chemicals should be as great as ever, with or without climate change considerations. Dismal air quality now poses significant health risks, especially in urban areas. Those who equate their global warming skepticism with an "anything goes" attitude regarding the environment are seriously jeopardizing the health of our planet and their own health along with it. If we prepare for global warming in ways that help protect the environment—we'll still be a lot better off—even on the off chance that we end up with a mini Ice Age instead.
Casey Kazan with Rebecca Sato.
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