There are cogent arguments on both sides

Gary WitzenburgIf you read my first ABG column a few weeks ago, you know that I'm no believer in human-caused global warming. My logical, data-driven engineering mind can't wrap around the idea that the 4% of CO2 created by all of the planet's human activity (96% is naturally generated), which goes into the less than 4% of greenhouse gases (95% is water vapor) and the 380 parts per million of the atmosphere that is CO2, can really be making much difference.

But wait! Before you begin writing the usual angry, insulting comments questioning my intelligence and ancestry, be aware that I recently wrote a pretty good argument supporting anthropogenic global warming (AGW). Why? It was an assignment for a major web site that wanted a balanced presentation of both sides so its readers could decide which to believe.

So I pried open my mind as far as it would go and went looking for expert evidence that we humans are, indeed, endangering the planet by burning carbon-based fuels, and breathing.

What follows is essentially what I wrote:

Yes, it's happening. But why, and what are the long-term consequences?

A lot has been said and written about the critically important issue of AGW. To understand what is really happening and why, and what might happen in the future, let's begin by separating truth from hype.
First, everyone should understand that the issue of global warming (or "climate change") has nothing to do with air pollution, because CO2 is neither "dirt" nor a pollutant.

Take a deep breath. Exhale. Much of what comes out of your mouth is carbon dioxide (CO2). All air-breathing creatures take in air, and their lungs separate oxygen from it. What emerges from the other end of this process is CO2, which is exhaled with every breath. The other side of this brilliantly designed system is plants, which absorb CO2 and "exhale" oxygen.

The Supreme Court confused the issue in 2007 by ruling that CO2 is a "pollutant" so they could compel the EPA to regulate it. But carbon dioxide -- not to be confused with potentially poisonous carbon monoxide (CO) -- is colorless, odorless and absolutely harmless. It is the bubbly gas in our beer and carbonated soft drinks.
But it is also emitted when carbon fuels are burned.

Atmospheric greenhouses gases effectively trap heat by absorbing some of what is reflected by the Earth's surface and re-radiating some of that back downward. Without them, scientists say, the surface temperature would average about zero degrees F. Water vapor is most of the other 96 percent, but the CO2 component has been increasing (due mostly to combustion of carbon-based fuels and fast-growing human and animal populations) since the industrial revolution. From a pre-industrial concentration of 280 parts per million (ppm), atmospheric CO2 has grown to 380 ppm today, and the current 1.9 ppm-per-year rate of increase predicts nearly 400 ppm in 10 years and 550 by the end of this century.

That is still a tiny amount – 380 ppm is just 0.038 percent, or 38 molecules of CO2 per 100,000 of everything – but many scientists contend that even that concentration is so far above the estimated range of 180 to 300 ppm over the past 650,000 years that the resulting increase in greenhouse gases has caused a warming trend over the last century. According to data accumulated by the National Oceanic and Atmospheric Administration's National Climatic Data Center (NCDC), global surface temperatures have increased about 0.74 degrees C (roughly 1.3 degrees F) since the late 19th century, and the linear trend of 0.13 degrees C per decade over the past 50 years is nearly twice that for the past 100 years.

Where the debate begins and scientists split into warring camps is the issue of cause and effect. The separate facts that both atmospheric CO2 and global temperatures have increased may or may not mean that one is causing the other. Scientists believing that the two are linked have built that theory into complex computer "climate models" that attempt to understand global climate behavior and interaction of its components, then predict its future.
And projecting the undeniable temperature trend of the relatively recent past into the distant future shows some fairly scary long-term scenarios. Among them are melting ice caps and glaciers, rising sea levels and potentially catastrophic heat waves and droughts, especially in warm tropical regions. NCDC says global mean sea levels have risen an average 1.7 mm (0.07 in.) per year over the past century and could rise another 0.18-0.59 meters (0.6-1.9 ft.) over the next 100 years, "depending on which greenhouse gas increase scenario is used."

A Special Report on Emission Scenarios issued by The U.N.'s Intergovernmental Panel on Climate Change (IPCC), which is made up of scientists and environmentalists from around the world, predicts a range of possible future greenhouse gas concentrations based on population and economic growth and energy efficiency. "This leads to a wide range of possible forcing scenarios," says NCDC, "and consequently a wide range of possible future climates."

IPCC predicts a global temperature increase in the range of 1.1 - 6.4 degrees C by 2100, depending on which emissions scenario is used. But IPCC's mission of forcing CO2 reductions on nations, however, is that population and economic growth, by definition, consume ever more energy and produce increasing amounts of CO2. What nation will voluntarily cut its economic activity, let alone try to reduce its population?

It appears that the only realistic way to significantly decrease man-made CO2 will be to develop safe and affordable non-carbon energy sources that will, over time, enable the world's populations to consume the massive and fast-increasing amounts of energy they will need to survive and thrive without emitting proportionally growing volumes of greenhouses gases.

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