Guest column: Global warming is real

The recent booing of the U.S. delegation at the Bali climate talks highlighted the continuing refusal of the Bush administration to accept mandatory limits on carbon emissions. Voluntary limits and more study has been the Bush policy on the issue of climate change and the possible causes.

Several recent columns by climate change skeptics in Twin Cities papers supported the Bush position. The most recent by Cal Thomas (Global warming debate isn't over, Pioneer Press, Oct. 27) contends that 400 scientists, some being IPCC members, doubt any danger to the planet from human caused warming. But Thomas cites just two doubting scientist names, Bob Carter and Hendrik Tennekes. Neither is listed among the 1,300 IPCC contributors.

Actually, "Warming of the climate system is unequivocal" per the 1,300 scientist members of the Intergovernmental Panel on Climate Change(IPCC) in their new report, Climate Change 2007. That report also states that the primary cause of the warming is green house gases(GHGs) generated by human activity.

A detailed review of the 940-page Climate Change 2007 discloses many reasons why the evidence of warming is unequivocal. Some of them are as follows:

Twelve of the last 13 years are among the warmest on the globe since records began in 1850 per the National Oceanic and Atmospheric Administration. NOAA also reports that "global surface temperatures have increased at a rate near 0.11 degrees F per decade since 1950, but the rate of increase has been three times larger since 1976, or 0.32 degrees F per decade." NOAA also stated that "the global December 2006-February 2007 land-surface temperature was the warmest on record."

The Arctic ice cap has been reduced by half during the past 30 years.

The USDA planting hardiness zones have been steadily moving north. Central Minnesota is now Zone 4 for the first time.

Glaciers are shrinking everywhere in the northern hemisphere, including in the massive Greenland ice shield.

The Alaska ice roads used by oil field service vehicles now stay frozen for 100 days versus 200 days in the early 1970s.

Many skeptics acknowledge some global warming. But they attribute the effect to natural causes, primarily changes in the intensity of solar radiation and the three variations in the earth's orbital cycles, tilt, wobble, and eccentricity.

The intensity of solar radiation striking the earth has been accurately measured by satellite for 40 years. There is a slight variation consistent with the 11-year sun spot cycle, but the overall trend is unchanged.

There are three varying cycles in the earth's orbit which do impact our climate - the earth's tilt from 22 to 24.5 degrees; precession or wobble, and the eccentricity of the orbit from ellipse to nearly circular. These long term cycles vary from 20,000 to 100,000 years, and they will not affect our weather in the 21st Century. They are the cause of the glacial epochs. If there is no other influence from human activity, it is projected that the interplay of those cycles could initiate a new glacial period in approximately thirty thousand years.

The earth radiates outward some of the sun's energy as non-visible infrared (IR) radiation. Green house gases (GHGs) with three or more atoms vibrate in sync with segments of this IR radiation, absorb some of it, and reradiate this energy to the atmosphere, warming us. Human activity is producing more and more of these long lasting GHGs, including carbon dioxide, nitrous oxide, and methane. This is the single new factor which is gradually raising the earth's temperature. Water vapor is also an important green house gas. Sprinkling lawns adds to water vapor, but any excess quickly rains out, so the water vapor content of the atmosphere is relatively stable. It's the growing level of those other GHGs that is the problem.

Rich countries, with a fifth of the world's population, consume about 75 percent of the world's resource production and produce most of the GHGs. The world's poor aspire to live as the rich do. We can already observe the scramble for resources and their rising prices. Global warming and resource scarcity loom in the coming decades. Let's hope our leaders are up to meeting the challenge this poses.

ROLF E. WESTGARD of Deerwood is a professional member of the Geological Society of America and Associate Chair of the Crow Wing County DFL.