| Justin Gillis, The New York Times. Relevant to GSS Life and Climate
chapter 10. Excerpt: ...Previous research suggested that as the world
began to emerge from the depths of the ice age about 20,000 years ago,
warming in Antarctica preceded changes in the global carbon dioxide
level by something like 800 years. That ...led some climate-change
contrarians to assert that rising carbon dioxide levels were essentially
irrelevant to the earth’s temperature.... ...A wave of new research in
the last few years has raised the likelihood that there was actually a
small gap, if any. ...Scientists have long known that ice ages are
caused by variations in the earth’s orbit around the sun. When an
intensification of sunlight initiates the end of an ice age, they
believe, carbon dioxide is somehow flushed out of the ocean, causing a
big amplification of the initial warming. Since the 1980s, scientists
have been collecting a climate record by extracting long cylinders of
ice from the ice sheets in Greenland and Antarctica, and from
glaciers.... Air bubbles trapped in the ice give direct evidence of the
past composition of the atmosphere. And subtle chemical variations in
the ice itself give an indication of the local temperature at the time
it was formed. The trouble is that air does not get sealed in the ice
until hundreds or even thousands of years after the snow has fallen, as
it slowly gets buried and compressed. ...Instead of the 800-year lag
between temperature and carbon dioxide increases found in some previous
research, [Dr. Parrenin’s] work suggests that the lag as the ice age
started to end was less than 200 years, and possibly there was no lag at
all. ...“What this does, again and more clearly than ever, is to show
that the large temperature changes are tightly coupled to the large CO2
changes,” ...said Richard B. Alley, a climate scientist at Pennsylvania
State University. ...The tight relationship in past climate between
temperature and carbon dioxide is a major reason scientists have warned
that modern society is running a big risk by burning CO2-producing
fossil fuels. The level of carbon dioxide in the atmosphere has jumped
41 percent since the Industrial Revolution began in the 18th century,
and scientists fear it could double or triple.... Even at the current
concentration of the gas, ...increases in sea level of 25 feet or more
may have already become inevitable…. Read the full article: http://www.nytimes.com/2013/03/01/science/earth/at-ice-age-end-a-smaller-gap-in-warming-and-carbon-dioxide.html |
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