Download 17 Feb 2007

MODERN TIMES
Art Hobson
[email protected]
NWA Times 17 Feb 2007
Global Warming: A Dose of Reality
One reason I elected to become a scientist is that it seemed to me that
scientists are in the reality business. Richard Alley, a lead author of the 2007
Fourth Assessment Report of the U.N.’s Intergovernmental Panel on Climate
Change (IPCC), Professor of Geosciences at Penn State University, and author of a
wonderful read titled “The Two-Mile Time Machine: Ice Cores, Abrupt Climate
Change, and Our Future,” is one such scientist. His comment to public servants
and citizens about the IPCC’s work is, “Policy makers paid us to do good science,
and now we have high very scientific confidence in this work—this is real, this is
real, this is real. So now act, the ball’s back in your court.”
Unlike those who believe for religious, ideological, or other reasons that
they possess the absolute truth revealed directly to them by some higher authority,
scientists are never absolutely certain of their conclusions. And yet, there is no
longer a reasonable doubt that human activities are warming the planet at a
dangerous rate. This proposition is sufficiently certain--“very likely” according to
the report--that it would be decidedly foolish not to act on it.
The Fourth Assessment might be the most comprehensive scientific report
ever issued on any topic. Written over a six-year period, it’s the most recent of
four IPCC reports. It’s an assessment of the work of many thousands of scientists
appearing in hundreds of scientific journals worldwide. Over 1200 scientists and
2500 expert scientific reviewers summarized this work in the IPCC report. The
full report will be published during 2007 in four sections dealing with (1) the
scientific basis, (2) its consequences, (3) options for slowing the trend, and (4) a
final synthesis report. The report’s conclusions are conservative, for at least four
reasons: science is always conservative because scientists hate to be wrong and
they love to spot the errors of other scientists; every word of the report had to be
agreed to by the IPCC’s 130 participating governments; the IPCC is prohibited by
its charter from entering into speculation; and only scientific results through 2005
were accepted.
This document represents, for sure, the scientific consensus. The 21-page
“Summary For Policymakers” of the scientific basis, drafted by 51 scientists
including people like Alley and Susan Solomon, co-discoverer of the Antarctic
ozone hole and co-originator of the chemical theory that correctly explains the
hole, is available at http://www.ipcc.ch/. It’s written in English that everyone can
read.
For convincing confirmation that humans have significantly changed the
atmosphere, consider Figure 1 in the Summary. It shows atmospheric
concentrations of carbon dioxide and two other global warming pollutants, during
the past 10,000 years. All three graphs remain at relatively unchanging levels right
up until 150 years ago, when they zoom upward to radically higher levels that are
unprecedented in at least 650,000 years.
Other conclusions: Global average temperatures rose 1 degree Fahrenheit
during the past century and will rise another 2 to 11 degrees this century, with
Arctic temperatures rising by twice these amounts, if we don’t severely reduce our
emissions of global warming pollution. Temperatures during the past 50 years
were the highest they’ve been in at least 1300 years. Eleven of the past 12 years
have been among the 12 warmest since instruments began recording temperatures
in 1850. Extreme weather (hot days and nights, heat waves, hurricanes, heavy
precipitation, drying, droughts) has increased and will continue increasing.
Permafrost and seasonally frozen ground has significantly decreased and will
continue decreasing. Mountain glaciers, snow pack, and snow cover have declined
and will continue declining. Summertime Arctic sea ice extent has decreased by
over 20 percent and will decline until the Arctic ice cap disappears almost entirely
later in this century. Fresh meltwater pouring into the Atlantic will cause the gulf
stream to slow, affecting global ocean flows, but this will not cause the feared
sudden cooling of Europe because global warming will dominate over any cooling
effects.
Oceans rose 7 inches during the past century because of melting mountain
glaciers, thermal expansion of seawater due to warming, and ice losses from the
Greenland and Antarctic ice sheets. Due only to mountain glaciers and thermal
expansion, oceans will rise an additional foot during this century. But one foot
could be a big underestimate, because although the Greenland and West Antarctic
ice sheets are showing signs of instability and rapid sliding toward the sea, these
phenomena were deemed too recent and too uncertain to be included in the report.
Going somewhat beyond the conservative IPCC conclusions, many
scientists believe that we have as little as ten years left before setting the great ice
sheets of Greenland and West Antarctica on an irreversible path toward complete
melting or sliding into the sea, a long-term process that would eventually raise sea
levels by 23 feet if the Greenland ice sheet alone vanishes (this happened during
the previous “interglacial period” 125,000 years ago when global temperatures
were only about 4 degrees above present levels). “Irreversible” means that
feedbacks inherent within the climate system will inexorably melt these ice sheets,
regardless of how humans may manage to limit or reverse the increasing
concentration of global warming gases in the atmosphere.
Present and future global warming pollution will continue contributing to
warming and sea level rise for more than 1000 years, due to the time required for
removal of these gases from the atmosphere. Where will this leave our
grandchildren?
As the planet warms, let’s hope America’s political will rises faster than
the temperature readings.