Pro: Inconvenient, anthropogenic and true
Following record-breaking snowfall in Washington and Virginia, many water-cooler conversations began with “What global warming?” The East Anglia debacle did not help. But global warming is real, and this is a retelling of an “inconvenient truth.”
Global warming refers to the increase in average temperature of Earth’s near-surface air and oceans during the 20th century and, more ominously, its projected continuation. What has happened up to now is irrefutable. Measurements coupled with sophisticated analysis to glean trends from random daily and seasonal variations indicate that the global temperature increased 0.74 degree Celsius (1.3 Fahrenheit) between the start and end of the 20th century; the last decade was the warmest on record.
But is the trend continuing for the next 100 years? And, is it human-caused or part of the natural cycle that has existed since the Earth formed 4.5 billion years ago? The answers are: yes and yes.
Less than 1 degree temperature rise per century seems innocuous enough. But a couple of more degrees and ice in the Arctic and Antarctica melts, sea level rises, coastal cities disappear, and desertification spreads. Even if the looming catastrophe were not human-caused, the only species capable of slowing the trend should aggressively tackle the problem, whatever the sacrifice.
Scientists employ the laws of nature as they understand them; by solving resulting dynamical equations, the future can be predicted. For the case of planet orbits around the sun, the equations can be solved to a high degree of precision, and humans have been able to predict eclipses of the sun and moon, ocean tides, and other phenomena dependent upon those orbits. Predictions were tested through the years: We have a high degree of confidence in calling the next eclipse.
Unfortunately, the equations needed to predict average temperatures are much more complicated, and even the fastest computer cannot deliver precise answers in a reasonable time. So scientists simplify the laws of nature using heuristic models, to the point at which supercomputers can provide answers. The reliability diminishes as the degree of simplification increases. Climate change over a decade is less reliable than the weather forecast for the next three days. Predictions are made statistically; for example, if current trends continue, there is a 25 percent probability that warming over the next 25 years will exceed 2 degrees C. Certainty is replaced by likelihood.
Nevertheless, both short-term weather forecasts and long-term climate prediction are good. The accelerated Earth warming predicted in 1990 was right on the mark when 2000 and 2010 rolled along. In fact, summertime melting of Arctic sea ice has accelerated far beyond the expectation of climate models. Furthermore, existing models predict increased severity and frequency of both hot and cold weather events.
This puts to rest the sneering every time a cold wave or a snowstorm hits. Broadcasters Rush Limbaugh and Matt Drudge, and Sen. Jim Inhofe, R-Okla., are no more right about a single snow event (or two or three) proving global cooling than lack of snow in Vancouver confirms global warming.
Dismissing the science because of its inability to provide certainty but rather likelihood is playing Russian roulette with the health and prosperity of future generations. The issue cannot be treated like a murder trial, which must be proven beyond a reasonable doubt. Cigarette smoking is accepted as hazardous on a preponderance of evidence.
Confidence in existing models to make predictions settles the question of whether warming trends will continue at a given rate. But what is causing global warming is a more challenging question. There is evidence that the current warming is part of a natural cycle, but is this trend exacerbated by human activities?
Ice or glacial ages occur on Earth quasi-periodically on time scales of millions of years. Within a long-term ice age, short-term pulses of extremely cold climate (glacial periods) and warm climate (interglacial periods) occur, also quasi-periodically, but on time scales of tens of thousand of years. Earth has been experiencing an ice age for the past 2.588 million years, with the peak of the last glacial taking place 20,000 years ago.
Earth has been in an interglacial period for the last 10,000 years. In other words, our world is in the midst of a natural warming period, and for most of those years humans have had insignificant influence on the rate of warming.
Among the hypothesized causes for the natural cycles of warming and cooling are atmospheric composition, cyclical changes in Earth’s orbit, and motion of tectonic plates. Greenhouse gases, such as water vapor, carbon dioxide, methane and ozone, contribute to global warming when released into the atmosphere in quantities beyond a delicate balance: Less than that balance and cooling ensues; more results in warming.
Almost all greenhouse gases are released and absorbed naturally. For example, carbon dioxide is released as a result of animal metabolism, volcanic eruptions and forest fires. The same gas is absorbed in the oceans and by rain forests.
But the natural global warming that started 10,000 years ago has accelerated quite a bit since the start of the industrial revolution when increased amounts of fossil fuel begun to supply our energy needs. The sudden change in the rate of global warming correlates strongly with the increased release into the atmosphere of human-caused carbon dioxide and, to a lesser extent, other greenhouse gases such as nitrous oxide and chlorofluorocarbons.
Climate models that take into account fossil-fuel usage and production of carbon dioxide have consistently and correctly predicted an increase in surface temperature beyond that predicted from the one interglacial Earth is currently experiencing.
Science works via a tight system of checks and balances. Peer review, empirical validation, and independent reproducibility are examples. Some scientists fabricate, cherry-pick, or embellish data; are biased by certain preconceived ideas; or simply make mistakes. But those are few and far between, and the system is designed to expose the charlatans, the misguided, and the foolish. Cold fusion announced at the University of Utah in 1989 is an example of misinterpretation of data, and this was rapidly exposed.
Relative to global warming is “Climategate”: More than 1,000 e-mails were hacked and released from the servers of the University of East Anglia in the United Kingdom. The messages hint at manipulation and selective destruction of data to bolster the case for human-accelerated global warming. An inquiry is being conducted there and another was just completed at Penn State University (at the other end of many of these e-mails).
There is damage to the case of anthropogenic global warming, but it appears that this episode does not rise to a level of dishonesty or misconduct, but rather sloppiness and overzealousness with unofficial, nonjournal writings. Archival evidence from many other researchers for human-caused global warming still stands high.
In Woody Allen’s film “Sleeper,” Miles Monroe is a health-food store operator who is revived from a deep freeze 200 years in the future. There, he finds a world where fatty food and smoking are good for your health. When the next glacial period arrives thousands of years from now, perhaps humans will be encouraged to waste energy, buy house-size SUVs, and burn whatever fossil fuel is left.
But for the foreseeable future, Homo sapiens need to conserve energy, seek alternatives to fossil fuel, control population growth, and provide sustainable balance to the delicate ecosystem we call home.
Mohamed GadelHak is the Inez Caudill eminent professor of mechanical engineering at Virginia Commonwealth University. Readers may write to him at VCU, School of Engineering East Hall, Room E3221, 401 W. Main Street, P. O. Box 843015, Richmond, VA 23284-3015; e-mail: firstname.lastname@example.org. He wrote this for The Free Lance-Star in Fredericksburg, Va.
Last updated: 1:39 pm Thursday, December 13, 2012