Nearly two centuries before humans had much effect on CO2 levels.
“It is not true that ‘most glaciers around the globe are in rapid retreat’,” says reader David Burton. “Some advance & more retreat, but few do either ‘rapidly’.”
“Nor is glacial retreat evidence of global warming. Global temperatures have plateaued at a relatively warm level, and that alone explains the continued retreat of most glaciers.
Above is a US Geological Survey map showing glacier extent at Glacier Bay, AK, in the 18th-20th centuries.
“Notice that those glaciers were retreating in the 1700’s, nearly two centuries before humans had much effect on CO2 levels,” says Burton.
“Note the large deceleration (reduction) in rate of glacial retreat during the 20th century, despite a dramatic increase in human CO2 emissions.
“Advance & retreat of glaciers is complex, and not just a function of temperatures. That’s why some glaciers advance as others retreat. For instance, at latitudes that never get below freezing, higher temperatures can increase sublimation but may also increase snowfall.”
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