MODERN TIMES
Art Hobson
ahobson@uark.edu
NWA Times 12 Sep 2008
A smoking gun looms in the Arctic
The evidence that global warming is real and human-caused is as plain as the nose on your face. For one thing, it's hard to see how the temperature could do anything but rise, given that humans have increased the carbon dioxide (CO2) content of the atmosphere by nearly 40 percent since 1900, that CO2 is a major greenhouse gas, and that natural greenhouse gases cause a temperature rise of 60 Fahrenheit degrees. For several other things, global temperatures have risen by 1.4 degrees, snowpack is declining globally, biological zones are migrating north, the number of intense hurricanes is increasing, coral reefs are vanishing, forest fires are increasing, ocean acidity is increasing, ocean levels are rising, and so forth.
Now
there's a new wake-up call from the Arctic. An article titled "Recent warming reverses long-term
Arctic cooling," by Darrell Kaufman and 29 other climate scientists,
appeared a week ago in Science. You can find it on the web by searching
for the title. A news release
featuring a key graph from the article is available at ucar.edu/news/releases/2009/arctic2k.jsp.
The
graph is quite a scientific achievement.
It shows 2000 years of Arctic temperature history, from year 1 to
2000. Climate scientists have many
"proxy," or indirect, ways of determining historical temperatures
before there were thermometers.
The temperature changes shown in the graph were determined from tree
ring widths (wider rings mean warmer summers), from ice cores drilled in Arctic
glaciers (the relative prevalence of two types of oxygen atoms depends on the
temperature), and from annually deposited lake sediments (the thickness of the
layers increases during warmer summers, and algae remnants are sensitive to the
growing season's length).
From
year 1 to 1900, the graph shows a steady cooling trend, with temperatures
declining by 0.4 degrees per thousand years. But beginning in 1900 the graph zooms upward by a full 2.5
degrees in just 100 years!
The
1900-year cooling trend is a natural consequence of the so-called "solar
cycles" that cause the alternating ice ages and warm periods. One obvious solar cycle is the annual
change of the seasons, caused by the tilt of Earth's axis relative to the plane
of Earth's orbit. But this tilted
axis "precesses" or rotates, like a tilted top whose axis rotates as
the top spins, so as to map out a complete cone once every 26,000 years. Also, Earth's orbit is slightly elliptical
rather than circular, causing a very slight warming and cooling each year that
adds to the warming and cooling of the seasons. These two effects (precession and ellipticity) combine to
cause a slight warming and cooling of the northern hemispheric summers once
every 26,000 years.
The
northern hemisphere is currently halfway through one of the natural cooling
phases. The graph nicely records
this effect during year 1 to 1900.
But the data changes radically beginning around 1900, when the graph
zooms upward. This is shown not
only by the three proxy measurements but also by thermometers beginning in
1850. This upward lurch cannot be
due to orbital cycles because they, acting alone, would cause the cooling trend
to continue for another 7000 years. There's little doubt that the upward lurch
is global warming, which stopped the long-term cooling trend and has completely
overwhelmed the natural climate trends since 1900.
The
20th century warming is quite dramatic.
During the 1980s climate scientists predicted that the day would soon
come when we would detect the signal of global warming arising out of the noise
of Earth's natural temperature fluctuations. Now that day is here.
The
new evidence shows, once again, that global warming is real and human-caused. It also brings the bad news that
warming is amplified in the Arctic. The Arctic is the most dangerous place on
Earth right now because it, along with the Antarctic, holds the key to ocean
levels. The Arctic ocean will soon
be entirely melted in the summertime.
"Feedbacks," or vicious circles, having to do with the
reflectivity of Arctic ice and with melting permafrost are likely to gang up to
melt much of Greenland's ice, raising ocean levels by many feet by the end of
this century. Because of natural
feedbacks, this process could, like Dr. Frankenstein's monster, lurch out of
human control. Studies show that
the current rate of summer ice loss in the Arctic could boost the rate of
warming across permafrost areas by up to 3.5 times, an increase that could turn
frozen ground into muck and release billions of metric tons of CO2 and methane
that's been locked up in the soil for millennia.
Humans
have barely begun to combat global warming. The Waxman-Markey cap and trade bill that recently passed
the US House is part of that beginning.
The fossil fuel industry is running large ads and sending out their CEOs
to speak against this bill. Their
ads and the reports of their talks say nothing about the devastation to come if
we don't combat global warming.
This is morally irresponsible.
According to the authoritative Stern Review on the Economics of Climate
Change, global warming will have an annual economic effect similar to that of
World War II, absorbing 20 percent of global GDP, while the cost of stopping
global warming might amount to 1 percent of global GDP.
We're on a fossil-fueled joyride to oblivion. Those who oppose cap and trade have a moral obligation to tell us what they would do to reverse the disastrous trend of the past century.