LETTER: Global warming and timelines

In a June 12 letter, Neal Matzkin objected to Victor Joecks’ column on climate, noting the claim that changes in solar output are responsible are “discredited. Solar radiation has been decreasing for more than 50 years.” Both Mr. Joecks and Mr. Matzkin tend to look at the wrong timescale.

The 50-year decrease in solar irradiation is a strawman. The important debate is about the effect of solar minima that occur on larger timescales. We started coming out of the Little Ice Age 150 years ago, after 600 years of relative “cold.” To give perspective, the California Sierra was largely free of permanent snow 700 years ago, but then developed the glaciers that are retreating today. It takes years to build up snow and cause an albedo reduction, which feeds off itself and further cools Earth. Some say the current warming is, in part, a return to “normal” conditions that existed before the Little Ice Age. The “part” seems to be between 0 and 70 percent, according to “experts.”

The cause of the Little Ice Age is unknown. Many feel it was prolonged by the Maunder Solar Minimum — a period of reduced sunspot activity — that began about 1645. Others feel that an increase in volcanic activity was the most important contributor. I’m highly skeptical of all grand models.