The other night, July 10, I watched a segment of the “News Hour” on the public television station, Channel 13 in New York City, which I highly recommend, https://www.pbs.org/newshour/bb/weather/july-dec12/weather_07-10.html. It was about the extreme weather we appear to be experiencing in recent years. After a set up piece, “Extreme Weather Records like a Baseball Player on Steroids,” an overview of extreme weather appearing around the world, Judy Woodruff interviewed Thomas R. Karl the director of the National Oceanic and Atmospheric Administration’s National Climatic Data Center. The credibility of his remarks on the show raised an avalanche of claims of nonsense, junk science and other protests against the assertion that global warming is a reality. According to Greenpeace, a great deal of this protest and denial originated in a campaign by a major oil company started some years ago. An overview of the denial situation can be found on the web: https://www.wikipedia.org/wiki/Climate_change_denial. I don’t want to enter into that argument but I thought it might be valuable to republish parts of a column appearing in this series six years ago, which tries to advance understanding of the scientific basis and potential consequences of global warming.
Here it is:
A popular documentary film is now making the rounds in the United States, “An Inconvenient Truth,” made by Al Gore, the man defeated by George Bush for the presidency of the United States in 2000. The film shows that the increasing amount of carbon dioxide in the atmosphere is far too much to be ascribed to natural sources and is caused by our activities in taking carbon in its various forms, coal, gasoline, heating oil, natural gas, wood, among others and converting the carbon in these fuels to carbon dioxide (CO2).
CO2 is a molecule that “loves” the infra-red radiation given off by the sun. The minute CO2 molecules, each one not much larger than 10-8 of a centimeter, absorb this radiation. Imagine the two oxygen atoms in the molecule, O=C=O, are connected to the central carbon atom by the molecular equivalent of springs, the = in the molecular picture of carbon dioxide. Like springs, the bond between the three atoms, =, is not fixed but allows the distances between the three atoms to constantly change. As infra-red light is absorbed by the CO2, this movement between the three atoms takes place faster and faster at unimaginable frequencies over the minute distances of chemical bonds – believe it or not, close to 300 trillion cycles in a single second. While this is going on, the CO2 molecules collide with each other and with other molecules in the air, the nitrogen and oxygen, and these movements of the atoms within each CO2 molecule push the colliding molecules to speed about faster and faster. The faster the molecules in the air move, the higher the temperature. This is global warming.
Although scientists, an exceptionally skeptical lot, are not convinced of the connection between global warming and the number and intensity of storms variously called hurricanes, typhoons or cyclones, storms that take their energy from the sea in the form of heat, the connection between global warming and the melting of ice is a different story. Here, all those skeptical scientists are in agreement that there can be no doubt that global warming is mightily contributing to the loss of ice both on mountain tops, most well known being that the famous snows of Kilimanjaro are now almost gone, and much more important that the enormous reservoirs of ice in both the north and south poles and in Greenland are growing smaller. There is no doubt that these reservoirs of ice are linked to the level of the seas. In an editorial entitled, “Ice and History,” (Science, March 24, 2006) this connection is made between carbon dioxide and sea level with the conclusion that glacial melting and changes in sea level are probable in our future. There are, however, so many unknowns in the precise way this could play out that no one can say what precisely will happen and over what period of time. However, scientists predict that change will occur.
We cannot assume that the climate and the sea level we live with now are permanent fixtures of the earth. The history of the earth is full of cycles and to show how extreme changes can be, it is a fact that when carbon dioxide levels were far higher than today, Cape Breton had a tropical climate and the sea level was about 50 meters higher than it is today! Although this state of the earth was more than fifty million years ago, some scientists fear rapid changes could occur based on what they are seeing today, on both the rate of increase of carbon dioxide in the atmosphere and the rapid changes observed in the ice covering the far north and south of our planet.
In the same March 24 issue of Science, there is a New Focus entitled “A Worrying Trend of Less Ice, Higher Seas,” which outlines the scientific evidence justifying the article’s title. Here we learn that the worry does not arise simply from melting ice because that is a very slow process. What is more worrisome is the slipping of huge volumes of ice from the land to the sea causing changes anyone can understand by simply dropping an ice cube in a full glass of water. You had better get a sponge to clean up the mess in the kitchen, but if your home is not far enough above sea level you could look forward to an even bigger mess if enough ice slips into the sea from the ice shelves at and near the poles. The reason for startling amounts of ice slipping into the sea, which scientists are measuring in various ways, is familiar to all of us. Ice is less dense than water so that lakes freeze over at the surface and leave water below for the fish to swim in. For the same reason, meltwater that forms on the surface of a glacier at one of the poles or in Greenland finds it way through cracks, flowing downward to finally reside where the glacier comes in contact with the earth below it. This water is a lubricant that allows the glacier to slip over the earth, allowing the glacier to make its way downward into the sea with all the consequences you saw in that glass of water but on an imaginably larger scale.
Is there any evidence that these changes can occur so rapidly as to even have an effect in our own lifetime or that of our children or grandchildren? Geological history may offer a clue to what could happen. About 18,000 to 13,000 years ago, a major ice sheet, the Cordilleran, that once covered large parts of present day Canada including all of British Columbia, advanced into an area now occupied by the northwestern United States. It blocked the flow of a river causing a lake to form, Lake Missoula, which at its largest was over 2,000 ft. deep and held over 500 mi³ of water – reported on a website to hold as much water as Lake Erie and Lake Ontario combined! Just as meltwater is now undermining the glaciers at the poles and lubricates the slippage of glaciers into the sea, meltwater undermined these huge ice dams formed by the Cordilleran glacier. The evidence shows that this led to sudden failure of the ice dam and released of all that water behind it in a period of days. This towering mass of water swept to the Pacific Ocean over large parts of western Washington State causing geological scars on the land testifying to the incredible force of the flood, which carried some of the land and even boulders and bedrock hundreds of miles out into the ocean and left an area appropriately named the Channel Scablands. It turns out that water undermining the connection of ice to the land is not a rare occurrence at all. In fact, geologists have evidence that the Cordilleran ice sheet caused this sequence of dam and failure and flood many times. Icelandic people have, in fact, seen this kind of thing in their lifetime and have a name for it, JÖkulhlaups, so that modern geologists have been able to directly observe variations on the great floods leading to the Channel Scablands.
The JÖkulhlaups and the history of the Channel Scablands show us that failure of large volumes of ice to stay in one place and melt slowly has been seen. How global warming and the future of the polar ice caps and sea level will play out in the future is greatly uncertain but change seems to be in the wings – what kind of change and how quickly it will occur is a large question mark among the experts but there is no question that increasing carbon dioxide in the atmosphere is mightily contributing to what is going to happen to our earth.