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Reader's view: Temperatures have varied naturally for millions of years

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opinion Duluth, 55802

Duluth Minnesota 424 W. First St. 55802

In July 1936 St. Paul endured three weeks of temperatures rivaling a Phoenix summer. On July 14, 1936, St. Paul hit 108. To the north, Moorhead, Minn., reached 114 a few days earlier. The dry Dustbowl raged across the Midwest. July of 1936 is the hottest U.S. month in recorded history, despite atmosphere carbon-dioxide levels being much lower than in 2014.

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If those 1930s summers were happening now, there’d be cries for even more drastic and expensive measures to limit carbon-dioxide emissions.

Carbon dioxide is a greenhouse gas, but it’s a trace gas whose contribution to global warming is small compared to water vapor, the primary greenhouse gas. Carbon dioxide also plays a beneficial role in photosynthesis, a process used by plants to convert the sun’s energy to sugars from carbon dioxide and water, releasing oxygen as a waste product for us to breathe.

Global temperatures have varied naturally for millions of years, unrelated to carbon-dioxide levels. More recently we had the warm periods during the Roman Empire and in the later Medieval Warm Period when the Vikings grew barley and wine grapes in Greenland.

In between, the Earth was colder when crops failed and life was miserable. Following the Medieval Warm Period we had the long Little Ice Age when Britain had an annual Frost Fair on the frozen Thames River. Our current warming is a recovery from the Little Ice Age.

Let’s think about all these expensive schemes to limit carbon-dioxide emissions. Coal-burning has a number of toxic emissions, but colorless, non-toxic carbon dioxide may not be one of them. Let’s focus on the mercury, sulfur and soot from coal-burning.

We inhale and exhale carbon dioxide and drink it without harm in carbonated beverages — except perhaps by gaining weight. Carbon dioxide is how plants gain weight.

Rolf Westgard

St. Paul

The writer teaches classes on energy issues for the University of Minnesota Lifelong Learning Program, including this fall’s on coal-burning and new EPA rules.

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