Global Warming beyond a Reasonable Doubt

The science of global warming is well understood. Certain gases, principally CO2, absorb solar radiation that would otherwise be dissipated back into space. Like a down comforter on your winter bed, they then radiate that heat back to the earth. The more of these gases in the atmosphere, the more energy radiated back to earth. The higher the percentage of carbon dioxide (CO2) in the atmosphere, the greater the amount of the sun's energy that is trapped on earth. The basic principles of global warming are as scientifically accepted as gravity.

These gases are called greenhouse gases for good reason. Their presence at the right concentrations is vital to life on earth. Without them, we would be a frozen planet. But we know with a high degree of certainty that over the last two centuries, human activities have increased the concentration of these gases to levels never before seen during human existence and probably not during the last 20 million years.5 The levels of CO2, for instance, have risen from 280 parts per million (ppm) in preindustrial times to 382 ppm today. And CO2 stays in the atmosphere for a long time; the carbon we emit now will be part of our atmosphere for another fifty to two hundred years. The question is not whether we are causing global warming, but whether we can avoid almost doubling preindustrial levels of these gases in our atmosphere. Unless dramatic changes are made in our energy economy there will be between 500 and 600 ppm of CO2 in the atmosphere by 2050, and 800 ppm by 2100. These are more than just numbers.

In other words, by the middle of the century, the gases that trap heat on our planet could be nearly twice as "thick" as they were before we started cutting down our forests and burning oil and coal—if we're lucky. Does it stretch the imagination to think such a titanic global change would have a dramatic impact on our lives? Much worse, should it not alarm us to realize that these projections may understate the problem, since world economic activity based on fossil fuels is accelerating, and these projections are based only on the rate of increase we are suffering today, about 2-2.5 ppm per year?

Among all but a few scientists, it is a given that we have already irreparably altered the course of life on earth. Mean temperatures have risen by 1.4°F and sea surface temperatures by .09-1.8°F over the twentieth century.6 Sea levels have risen nearly .2 meter, and the extent of Arctic ice has decreased by 7-15 percent, depending on time of year.

According to both the National Academy of Sciences and the Intergovernmental Panel on Climate Change, the evidence that human activity is causing most of this change is unequivocal.

But this is only the beginning. It is virtually certain that continued buildup of greenhouse gases will cause increased warming, with the potential for sudden changes in major ocean currents, tundra meltoffs, and other unpredictable results presenting additional dangers.

We can expect further increases of between 3.24 and 7.2°F this century if CO2 emissions continue on their present ominous path.7 To put that in perspective, the difference between the last major ice age and our current climate is less than 10°F. Such temperature increases mean longer periods of severe storms as energy in the environment increases. As rising sea levels threaten our shorelines, increased storm surges and extreme wind events become matters of concern. Declining soil moisture will mean lost agricultural productivity and more frequent drought, pests, and forest fires.

All of these statements represent the consensus of an enormously diverse community of scientists from around the world. At a hearing of the U.S. House of Representatives Energy and Commerce Committee in July 2006, organized to challenge the science of global warming, even the witnesses called to question the science ended up agreeing to these basic findings. And of 928 peer-reviewed articles in scientific journals randomly selected from the thousands that have been published in the last decade, not one questioned these fundamental conclusions.8

Like the tobacco industry of the 1960s, which declared, "Doubt is our product," some in industry have nonetheless continued to stress uncertainty to promote inaction; but questioning the basic fact pattern is no longer acceptable in public debate, and many signs of change are emerging. As an example of how far the conversation has moved, even Shell Oil has come out in favor of managing CO2 to reduce the threat of global warming, and Exxon has dropped some of its support for groups questioning global warming science.9

But the scientific news has not gotten better as the picture has become clearer. The damage predicted is more imminent than it was considered just three years ago when the world's largest scientific panel ever assembled—the Intergovernmental Panel on Climate Change (IPCC), established by the World Meteorological Organization (WMO) and the United Nations Environment Program (UNEP)— released its Fourth Assessment Report. "All the new information makes it more ominous. Ice caps are melting faster. Greenland is melting faster. Permafrost is melting faster. Beetles are killing millions of acres of forests—since 2000, we have lost an area the size of Illinois to forest fires—and this wasn't even contemplated. Extreme weather events are accelerating in frequency. Feedback mechanisms like methane escaping melting permafrost were not even considered by the IPCC. It's worse than we thought," says Joe Romm, whose book Hell and High Water ought to make the most sanguine concerned.10

For example, hardly anyone had heard of the problem of ocean acidification three years ago. Some even proposed pumping CO2 into the ocean to store it. Now the evidence is conclusive that CO2 from the atmosphere is entering the water and turning it more acidic. Little ecosystem bombshells like this keep going off as our understanding of the climate grows.

When it comes to responsibility for global warming, not all men are created equal. We Americans are the leaders, unfortunately, in global warming. We are only 4 percent of the world's population, but we emit 23 percent of the world's CO2.11 On a per person basis, the average American is responsible for close to twenty tons of CO2 each year, nearly ten times what an average Chinese citizen emits.12 We must do better, and we must do so urgently. It is literally a matter of survival.

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