Archive for December 18, 2013

By Cheryl Katz

The Daily Climate

“What’s more, Iceland’s glaciers have advanced and retreated several times in the 11 centuries that A Climate at Your Doorstep story.

humans have lived there, leading many to see the current retreat as part of a temporary, natural cycle.

“The glaciers have always been going up and down,” said Hallgrimsson, who noted that early settlers faced considerably less ice than do residents today. “It looks like we are getting a period similar to around 900 (A.D.)”

‘Of course nobody knows.’”

http://wwwp.dailyclimate.org/tdc-newsroom/2013/12/iceland-ice-climate

“It looks like we are getting a period similar to around 900 (A.D.)”

I’ve read a lot of statements similar to the one above.  I find them sad because they reveal a serious misunderstanding of how it is to be a planet like Earth and have varieties of weather and climates. For one thing, the main drivers for climate change are known as the Milankovitch Cycles.

http://www.sciencecourseware.org/eec/GlobalWarming/Tutorials/Milankovitch/

http://www.indiana.edu/~geol105/images/gaia_chapter_4/milankovitch.htm

It is the coincidence of how these three cycles affect insolation [The incident radiant energy emitted by the sun which reaches a unit area over a period of time] that has the greatest effect on climate.  Since the exact duration of these cycles is not constant, throughout the past and in the future, the coincident value of the three never repeat.  Thus the resultant climate at any particular place on the planet will never exactly repeat.  Not only that, but the last major extinction of life on earth was some 65 million years ago. For around 2.6 million years now we have had a cyclical glaciation/warming environment.  Conditions prior to each positive and negative temperature swing were similar in that two are sometimes all three of the cycles favoured a change.

Anthropogenic air, sea and land pollution, greenhouse gas emissions, and the massive destruction of forests have never preceded a cyclic swing within this period.  My meaning is that we have no precedents to help us understand just how a swing to a cooler environment and subsequent negative temperature swing might come about.  No-one other than [An Exceptionally Long Interglacial ahead? A. Berger and M. F. Loutre] appears willing to make a statement about the analysis of the present state of the cycles, greenhouse gasses and temperature as to what the chances are for a downward trend in temperature.  My unprofessional analysis comes up with a notion that the Earth shall skip a complete glacial/interglacial cycle.  How Earth will cope with the continued rise of greenhouse gasses and temperature leaves me frightened.