Monday, May 27, 2019
Despite all the scare stories about global warming, we are actually in an Ice Age. We are in a relatively warm period within a much larger incredibly cold period says geologist Dan Britt. In his lecture Orbits and Ice Ages: The History of Climate, he says “reading the rocks” gives us a really good record of climate for the past 500,000 years. And the climate for the latitude of Pensacola, for example, is about the same now as it was in the Mid-Cretaceous period a half billion years ago.
Since then, the average temperature of the earth has been much warmer than today. There were only four periods that were as cold as the present. In short, we are in one of those rare periods in which the earth is about has cold as it ever gets, at least in a half billion years--so why are we worried about global warming? During those four warm periods, each lasting 3,000 to 4,000 years, nowhere on earth, including the poles, was the average temperature below freezing. Temperate climate extended all the way to the Arctic Circle. Today in the Arctic Circle, fossils can be found of crocodiles, turtles, and breadfruit trees. The temperature must have been quite warm for those species to survive there. The climate where New York city would someday rise was comparable to that of Key West today. But during the extreme cold of the Ice Ages, the ice was a mile thick at the New York city location, and also at the sites of London, Berlin, and Minneapolis.
Carbon dioxide is a natural part of the atmosphere, and it can increase or decrease from natural processes having nothing to do with burning fossil fuels. We have been warned that 400 parts per million (ppm) CO2 is a “tipping point” for an unavoidable worldwide environmental disaster from global warming due to burning fossil fuels. But pre-industrial CO2 reached 1,700 ppm—six times the pre-industrial level—when there were no factories or automobiles; and the high CO2 couldn't even melt the glaciers, much less overheat the earth.
What is the “normal” level for CO2? The earth has seen both higher and lower levels of CO2. Can anyone say today's level is the optimum or that a higher or lower level would be better? Glaciers are rising. What is the “normal” level for glaciers. Sea level is rising. During the last glacial maximum, sea level was 150 to 200 meters higher than today. Would the average sea level of the past half billion years be the standard for which we should strive? That standard would eliminate Florida; Miami would be under 80 meters of water. There is no “normal” level for CO2 or for sea level.
What about Antarctica? Is it threatened? Should we be worried? There is no such thing as a “normal” level of glaciation for Antarctica. There was no Antarctic ice until 35 million years ago. Glaciers are triggered by changes in the earth's orbit. Antarctica glaciated, but that did not last. Then 12 million years ago Antarctica re-glaciated, which brought a sharp drop in the earth's temperature, which increased rock weathering. More important, when India collided with China creating the Himalayan plateau, it greatly increased rock weathering, which sucked out 80 percent of the carbon that was in the Cretaceous atmosphere.
Carbon is essential to all animals and plants. If the CO2 level in the atmosphere is too low, they will be will be unable to reproduce, and the earth will become a barren planet. That fate was avoided by the invention of agriculture, variously estimated at 8,000 to 10,000 years ago. To expand farmland for food, people were cutting and burning bushes and trees—thus putting carbon dioxide back into the atmosphere. About 5,000 years ago they also began cultivating rice, and rice paddies also put carbon dioxide (and methane, another greenhouse gas) into the atmosphere.
Volcanoes represent the largest natural input of carbon dioxide into the atmosphere. Other natural sources include sunspots, ENSO (the southern oscillation of the El Nino ocean current) and CO2 already in the atmosphere. Britt thinks all of these may have some limited effect but too minor to be more than just “noise” in the background.