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.
