August 17, 2017

The predictions of science derive from fact, not conjecture. Global warming is upon us and only the most brazen troglodytes can deny its presence. Its prognosis is grim. Put simply, a lot of the earth’s surface will drown soon and many habitats and species will be gone forever. (And when Vanuatu vanishes, creationist scoffers will chuck it down to divine justice, not to human causes!)

What is global warming and how does it happen? The earth is hotter now than in all recorded history (the dozen millennia during which human civilizations arose); it is set to get warmer, and the accelerating factor is human activity.

Ignoring minute contributions from other stars, all energy on earth comes from the sun. Earth absorbs some of this insolation and reflects the rest back to space. Unfortunately, it is the heat rays (infrared end of the electromagnetic spectrum) that are retained. This is called the greenhouse effect, for it’s the process by which a greenhouse becomes a hothouse in which vegetation flourishes abnormally. On a summer day a car parked on the street will register 20–30 degrees higher inside than on the outside if windows are wound up, but not if windows are down—a deadly peril to any children left in a parked car! The reason is that window glass (like our atmosphere) admits all the wavelengths of sunshine but then blocks the heat rays from leaving.

So, atmospheric gases that trap infrared rays and heat up the earth are called “greenhouse gases.” Some gases are more effective than others at trapping the escaping rays. Water vapor causes 35-70% of our greenhouse effect; carbon dioxide, 10-25%; methane, 4-10%; etc. Fluorinated (hydro)carbons, nitrous oxide (NOX), sulfur compounds are some other potent greenhouse gases. Nature produces greenhouse gases abundantly and they are normally beneficial—but for them, earth’s surface would be too cold for life. But human activity, mostly the energy-allied industry—especially our ubiquitous automobile—is tipping the scales out of balance, threatening to broil us all. And, of course, of all the factors contributing to global warming, human activity is the only one we can control—if the energy industry and their political surrogates let us.

Because of the humongous complexity of interactions that control our climate (Have you heard of the putative “butterfly effect” of weather change?) a rise of the earth’s mean temperature by a mere couple of degrees might be enough to melt the entire polar ice caps that are tens of miles deep, and cause global flooding. Also, increasing atmospheric carbon dioxide, NOX, and sulfur gases, makes ocean water more and more acidic, so that aquatic life begin to die off. (A recent book, “The Sixth Extinction,” by Elizabeth Kolbert provides a stunning peek at the consequences, and is eminently readable because the author is a journalist and not a scientist. All five extinctions in geologic history arose from natural causes; the sixth and current one, now in progress, is of human making!)

As we know, temperatures vary widely from place to place at any time, and from time to time at any place; so “average” temperatures are hard to define. That fluctuation provides a dodge for die-hard deniers of global warming who scoff: “What global warming? I’m freezing right now!” But when temperatures are plotted against long times, a definite rise in the mean values can be seen by anyone who doesn’t have his head in the sand. That is global warming; it portends climate change! Think of the enormous stakes we’re toying with: humans have nowhere to escape, the earth is all we have!