Research Confirms Timing of Tropical Glacier Melt at the End of the Last Ice Age
Phys.org / December 11, 2019

Tropical glaciers in Africa and South America began their retreat simultaneously at the end of the last ice age about 20,000 years ago, according to a Dartmouth study.

The finding of synchrony in ice retreat across the global tropics clarifies how the low latitudes transformed during one of Earth’s most extreme climate change events and can help current-day predictions of our own climate future.

The study, published in Science Advances, supports the overwhelming scientific consensus on the role of carbon dioxide in causing global climate change, but adds additional levels of complexity to the understanding of Earth’s climate system and how ice ages rapidly end. The result also adds to the understanding of the sequencing of glacial retreat between the tropics and the polar regions at the time

“Carbon dioxide is what caused the Earth to come out of the last ice age,” said Meredith Kelly, an associate professor in the Department of Earth Sciences at Dartmouth, and senior researcher on the study.

… just before contradicting herself:

“But there are also processes that began before carbon dioxide increased that are important to the overall story of how the period ended, and that’s what we wanted to understand.”

According to the Dartmouth study, glaciers in tropical Africa and South America reached their maximum extents about 29,000-21,000 years ago and then began to melt. This retreat is earlier than the significant rise in atmospheric carbon dioxide recorded at about 18,200 years ago.

So the coming-out-of-the-ice-age preceded, by many thousands of years, the rise in carbon dioxide that is said to have “caused” it. Got it.

The findings demonstrate a trend of increasing tropical temperatures across the planet and suggest that the warming may have been caused by a reduction in the temperature differences between the Earth’s polar regions and the tropics.

At the end of the last ice age in the Arctic, small changes in Earth’s orbit resulted in more solar radiation and warmer temperatures, and caused a retreat of the northern ice sheets. In Antarctica, the change of the planet’s angle to the sun created longer summers. The reduction in the temperature gradient between the poles and the tropics slowed the movement of heat out of the low latitudes to the extreme north and south, making the tropics warmer and resulting in faster loss of glaciers in the region.

… And, having described the astronomical causes of warmer temperatures, they return to the obligatory “but it was the later increase in carbon that really did it.”

But if carbon did not exist at all, what would the glaciers have done under the effects of the planet’s changed orbit and angle to the sun, which resulted in more radiation and warmer tempertatures?

Once changes in ocean and atmospheric circulation patterns and the upsurge in carbon dioxide took over, the planet was left in an overwhelming warming spiral

. . . which self-corrected at some point?

Or does it continue today?

In either scenario, SUVs seem to be exonerated.

that melted ice sheets near the poles and all but eliminated glaciers in the tropics.

“Just a couple of thousand years could make all the difference in our understanding of past and present climate change events,” said Margaret Jackson, who served as the lead author of the study while a Ph.D. student at Dartmouth. “This study shows that glaciers were responding to warming even before the deglacial rise in carbon dioxide pushed the planet over the edge to end the last ice age.”

Something tells me they’re going to tell Margaret to couch her statements, in the future, with wording that better disguises this plain truth.