One thing to note, I think, is that the term “ice age” is often used to describe two different things, particularly in the media and in the vernacular. The difference is largely one of scale. You hear a lot about the “last ice age” being around 10,000 years ago, and this is technically inaccurate–the term “ice age” is generally used by scientists to describe a much longer period of time, some hundreds of millions of years.
Within these, there are shorter, episodic advances and retreats of continental ice coverage, spanning tens of thousands of years or more. These advances–often confusingly also called “ice ages”–are more properly termed glaciations. The corresponding retreats of ice are known as interglacial periods.
So while Polycarp is absolutely correct in pointing out that we’re still in an Ice Age, it should also be made clear that we are in an interglacial period within that ice age, the last glacial period being some 10,000 years ago. Since that’s an easier time frame for a human perspective, it’s the one commonly referred to. Climatologists, like geologists, think on a much longer (and larger) scale.
Nitpick: In that book, the folly of environmentalists-in-power was not that they caused either global warming or the ice age. The ice age results from a purely natural cycle. The environmentalists’ folly was that they succeeded in scuttling anthropogenic climate change just when it would have come in useful, with the result that the ice age proceeds unchecked and Canada is no more habitable than Greenland.
And, as noted, they envision it all happening way too fast – correct me if I’m wrong, but in previous ice ages in our planetary history, the progress of the glaciers was, well, glacial. (They can melt a lot faster than they can grow.)
Still, a fun book, especially Leslie Fish’s cameo appearance!
Beware what you watch on tv or read on the internet. Global warming doesn’t exist, the planet naturally goes through these shifts in temeratures. In fact, if you took all the climital conditions of the planet thorough its 4.5 billion year history into consideration, the period we have been living in for the past few thousand years has been a freak lapse in environmental conditions. This stablity that we are now in, where there are but a few natural disasters once in a while, will come to an end. This explains why our written records of life, our oldest books and documents go back to only 4000 years, while humans in our present form (homo sapien sapien) have existed for 150,000 years.
It also totally absurd of Al Gore to say that our harmful gases and enviornmental pollution could actually CAUSE an ice age. Geologists have confirmed that the planet has gone through over TEN previusly ice ages by studying layers of earth hundreds of millions of years old.
What we have here is what a good psychologist would call a correlational problem. Yes, we do make a lot of pollution. And Yes, it is inevitable that this planet will go though another ice age (according to most scientists). But to say that the polution CAUSED the ice age is ludacris.
The Arctic Ice Pack grows very slowly, because prevailing winds have already lost their moisture long before getting to the Arctic Circle. Since it doesn’t melt at all during most of the year, the balance is better than it might be, but for a long time now, it has not been growing. In historic times, it has been shrinking, and that process may well be approaching speeds that will cause a catastrophic melting. (Catastrophic meaning happening in mere centuries, rather than millennia.)
The point is that snow falling onto the open ocean is not going to form an Ice Pack under normal conditions. The current Arctic Ice Pack originated on the land surrounding the Arctic sea, and grew out as shelves from all around, during the million year period that is the current Ice Age. During the various interglacial periods, much of the ice at the margins has been melting, but the polar region has remained frozen, although becoming thinner at times.
Once it actually melts the situation changes. While more snow will form, that snow must accumulate along the frozen areas south of the pole, and then grow out onto the Arctic Sea again. That process might take another million years. It must certainly take longer than breaking up and melting the Ice Cap, because that process is greatly aided by convection, and sea currents moving blocks of Ice southward. No such mechanism exists to accumulate ice at the pole itself.
Antarctica has been more stable during the interglacial periods precisely because so much of the ice pack there is on land. If the central portion of the Antarctic Ice Pack should melt catastrophically, the refreezing could take place much more quickly, if conditions change. This scenario has recently been given strong supporting evidence by studies that show that the Last Glacial Maximum in the Northern Hemisphere did not occur at the same time as the LGM for the Southern Hemisphere. The North appears to have thawed out at a much higher rate. It also seems to have been subject to faster fluctuations over the broader scale of interglacial periods. The presence of land at the South Pole is believed by some to have contributed to the existence of the most recent Ice Age. Other Ice Ages might have coincided with the existence of large percentages of land at the poles, but that is not clearly shown, by existing evidence.
Tris
“It should be possible to explain the laws of physics to a barmaid.” ~ Albert Einstein ~
“You should see the place where Einstein used to drink!” ~ Triskadecamus ~
Forum rules won’t allow me to call you a troll, but I can and must point out that, whenever a guest shows up here and starts posting claiming anthropogenic climate change does not exist or is nothing to worry about, the mods shortly figure out that guest is a propagandist and ban him/her. You might well be an exception, of course.
I think a plausible argument can be made that the effect is overstated, but I’m hoping it can be presented by someone more articulate and who understands that writing took some time to invent.
More FAQ from ABC Science
*How can scientists tell that climate change is due to greenhouse gases, rather than part of a natural climate cycle?
Submitted by Bob Joyce
A: The Earth’s climate fluctuates naturally because of wobbles in the axis of rotation and variations in sunspot activity. For about 11,000 years we have been in a period of warming. Prior to this glaciers covered much of the Northern Hemisphere and the temperature was about 5 degrees cooler. Even in the last 2000 years there has been a variation in average temperatures if 1 to1.5 degrees.
Northern Hemisphere thermometer records, as well as climate data from tree rings and ice cores has shown that the 20th century was unusually warm compared to the last 1000 years. Other evidence includes increased heatwaves, fewer frosts, warming of the oceans and lower atmosphere, less snow and retreat of glaciers and sea ice. Sea levels have increased 10 to 20 centimetres.
Climate scientists have run computer simulations to see how the observed warming fits in with the natural climate variability and human-induced climate change. Natural climate variability from solar irradiance and volcanic eruptions explains much of the warming of the first half but not the second half of the 20th century. When simulations take into account both greenhouse gases and aerosols (small airborne particles) due to human activities, the simulated warming is consistent with that observed in the second half of the 20th century. Scientists have concluded that most of the global warming of the last 50 years is due to human activities.*
*
Kevin Hennessy, Climate Impacts Group, CSIRO Atmospheric Research*
