Thursday, December 20, 2012

"Climate Change: Lines of Evidence": film offered by Koshland Museum at the National Academy of Sciences

The Marian Koshland Science Museum of the National Academy of Sciences in Washington DC offers a 25-minute short film “Climate Change: Lines of Evidence”.  The link for the museum is here.  Adult admission is $7 and the closest Metro is either Judiciary Square or Gallery Place-Chinatown. 
The film is in seven segments, and each one “ends” as if it stood alone.

The first segment explains the nature of climate (as opposed to weather).  The succeeding portions give the evidence that climate change – global warming – is largely manmade.  At one point, it says that carbon dioxide concentrations are now higher than they have been at any time in the last 800000 years. It makes an interesting comparison between carbon dioxide and methane.  In fact, methane retains much more heat with its blanket effect than does carbon dioxide, but it does not persist in the atmosphere as long. It also says that when the Earth was only nine degrees cooler Fahrenheit, we had an Ice Age.

One segment dealt with natural fluctuation in climate. The Earth’s temperature is on an unmistakable trend upward, but it does have sawtooth dips and rises, with El Nino making it a little cooler and La Nina making it warmer.  Huge volcanic eruptions like Pinnatubo can reduce the Earth’s temperature slightly for about a year.

One of the late segments examines the effect of solar output.  In fact, the Sun has emitted slightly less energy in the past fifty years than it  did during the first half of the 20th Century.  In time, however, solar output may increase.

The film would do well to include some material about solar storms, since thr NAS as issued a booklet on "Severe Space Weather Events" (Book reviews blog, Aug. 9, 2012).

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