Wally Broecker says a cosmic impact caused the Younger Dryas

I realize that this subject is distasteful to many because of the early false claims. But the
new evidence suggests that there was some kind of extraterrestrial impact. Hence it should be given further study.

I remember pleading with Science’s Richard Kerr to do a piece on this discovery. He thought about it and decided that, as he had written a very negative piece about the original idea, he didn’t want to revisit the subject.

Although I don’t for a minute believe that this impact did in the mammoths and the Clovis people, I do think that it triggered the YD.

What a significant and pleasing development. Wally Broecker has endorsed a cosmic impact as the cause of the Younger Dryas cold period.  Broecker is a father of modern climate science (and pictured above with the Tusk at my heaviest in 2009).

This is more than just another log on the intellectual fire of the Younger Dryas Impact Hypothesis. In 1989 Broecker first proposed that the Gulf Stream was slowed by a dramatic fresh water pulse into the North Atlantic a mere ~12,980 years in the past, which plunged our hemisphere into 1200 years of frigid cold, a period known as the Younger Dryas.

The cold period and Broecker became inseparable and the idea became a movie.

I am not entirely surprised by Wally’s support for the YDIH. He was cited and thanked in the 2013 Paetav paper which identified a Platinum spike in the geochemistry of the Greenland ice core and concluded an impact was at work. His positive disposition with regard to the theory was also quoted around the same time in National Geographic:

“Most people were trying to disprove this,” said Wallace Broecker, a geochemist and climate scientist at Columbia University’s Lamont-Doherty Earth Observatory. “Now they’re going to have to realize there’s some truth to it”  –  though maybe only a spherule or two.

Put aside the gratuitous author shot following the quote, and you can see that by 2013 Broecker had sweetened on our favorite wild theory.

But alas, it was not always thus. In 2010, David Morrison, a grandfatherly figure at NASA, gave his narrative concerning a 2009 AGO session attended by the Tusk, and headlined by Broecker. Here is an excerpt:

The star of the event was Wally Broecker of the Department of Earth and Environmental Sciences at Columbia University. Broecker is one of the most respected environmental scientists in the world. Credited with first describing the ocean current conveyer belt and inventing the term “global warming,” his honors include membership in the National Academy of Sciences and award of the Presidential Medal of Science. His presentation was sober and low key, but he made it clear that he was unconvinced by the evidence for an impact or any catastrophic change at the YD boundary. But rather than condemning the hypothesis, he stated simply that the decline in the North American megafauna could be understood as a result of climate change and overhunting—the conventional explanation. Broecker said, “We do not need the impact hypothesis.”

So. What are we to make of the progression of Wallace Broecker, from public skeptic, to private encouragement, to highly personal endorsement of a cosmic cause for his iconic example of abrupt climate change?

Well, Wally himself tells the story best in his ‘brief’ below, and it seems to be an old one: The scientific method worked and a preeminent expert was slowly but surely convinced by overwhelming evidence for the impossible.