Dark Moon Cooling

Categories: Climate

Based on a AAS news release

Scientist Traces Dark Eclipsed Moon and Cold Weather in 1761 to a Mysterious Volcanic Eruption

An early summer and late autumn lunar eclipse on tap
Credit: Noel Munford (Palmerston North Astronomical Society, New Zealand)

"A dark moon rising" once portended bad weather and disasters. The correlation may sometimes have a factual basis, Dr. Kevin D. Pang, an independent research scientist, reported at the American Astronomical Society meeting in Long Beach, California. Pang cites strange celestial events in 1761 as an example.

"The reason is quite simple," Pang explains, "a high altitude volcanic dust cloud that cuts off the sunlight illuminating an eclipsed moon would also reduce the solar energy reaching the Earth’s surface, thus causing a cold spell."

Pang mentions "the year without a summer" in 1816 as another example. The powerful Tambora eruption in Indonesia in the previous year had so overloaded the atmosphere with volcanic dust that the June 16, 1816 totally eclipsed moon could not be seen. The sun’s rays, refracted by the Earth’s atmosphere, were apparently blocked by volcanic dust before they could reach the moon, deep in the Earth’s shadow.

Pang recently learned that the May 18, 1761 totally eclipsed moon appeared very dark or invisible to many observers worldwide. Suspecting that this was also due to a very powerful volcanic eruption, he searched for evidence of a "volcanic winter" in Chinese weather chronicles, tree rings and polar ice cores.

After poring over volumes of Chinese history texts and databases, Pang discovered that indeed heavy sustained snowfall and bitter cold prevailed over wide areas in China in 1761-1762.

Chinese historians report that "rivers and wells froze, and ships could not sail on the great lake Taihu near Shanghai, because of the floating ice." Heavy snow fell as far south as the Tropic of Cancer; and innumerable trees, birds and livestock died of cold, the chronicles state.

Dust clouds from large volcanic eruptions may have cut off sunlight illuminating lunar eclipses in the past…and reduced the amount of solar energy warming the Earth’s surface.
Credit: SOHO

Pang points out such extremely cold events are very rare in subtropical and temperate China. So much so that homes south of the Yangzi River are not heated. Pang found further evidence of the unseasonable cold half a world away in Western USA. Tree ring experts have previously noted that the growth of bristlecone pine trees high in the Sierra Nevada Mountains was stunted in 1761. Frost damage appears in that year’s growth rings.

To ascertain that the anomalous celestial events were volcanically forced, Pang sought confirmation in polar ice cores. Glaciologists have previously reported abnormally high concentrations of sulfuric acid in the 1761 and 1762 strata of the Greenland and Antarctic ice sheets. Sulfur dioxide gas emitted by volcanoes reacts with water vapor to form acidic droplets, which eventually settled and are still preserved in polar ice.

Pang says that "the early 1761 volcanic eruption was very powerful, as it was felt in ‘all corners of the world.’ The bipolar extent of the acidic deposits suggests that the volcano was at a low-or mid-latitude. However its exact location is still unknown. So the mystery continues."

Finally, Pang credits Benjamin Franklin with discovering the volcano climate connection in 1784. Franklin’s criteria for a climate-altering eruption are still universally used, Pang concludes.

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