Reality of Global Warming
the world, abundant paleoclimatic evidence suggests that the
earth has warmed over the past century to levels not reached
for thousands of years. This evidence includes ground temperature
profiles, permafrost thawing, range shifts of animals and
plants, and changes in the spring flowering dates of plants.
Trees found near the margin of the tundra are particularly
sensitive to temperature changes. Tree-ring chronologies from
these cold region trees indicate a robust growth surge, spurred
by climate warming that is unprecedented over the past millennium.
day glacier and ice coverage of the northern hemisphere
( right), and the same region 18,000 ago.
is easy to claim, as many skeptics of global warming often
do, that computer models of the global climate and paleoclimatic
indicators are incomplete and involve uncertainties. This
is true and will always be true, of course. We will never
know the infinitely complex climate system of earth without
uncertainty. And we will never have the equivalent of an evenly
distributed network of thermometer and rain gauges covering
the globe for the past millennia. But the overwhelming majority
of the paleoclimatic records we do have show unprecedented
warming of the world since the dawn of the industrial period
during the 19th century. This is the simple message of the
Ice Man, discovered at 10,500 feet in the Italian Alps after
his glacial ice tomb recently melted to reveal his body preserved
for over 5000 years.
majestic baldcypress has witnessed a thousand years
of history, but its numbers are dwindling.
anthropogenic climate and environmental change imperil the
very records used to reconstruct past climate. The Ice Man's
tomb and many glaciers have melted, coral reefs are bleaching
and dying from high sea surface temperatures, and ancient
forests continue to fall. The large old-growth baldcypress
trees at Blackwater River, Virginia, that recorded the catastrophic
drought at Jamestown are a remnant of a once widespread clan
of millennium-old trees. Centuries of overexploitation have
made these trees exceedingly rare. As we celebrate the 400th
anniversary of Jamestown Colony and the first English in the
New World, we might also remember those ancient trees at Blackwater
River that witnessed that history and now stand nearly alone.
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Mark McCaffrey, NGDC/NOAA; University of Arkansas