While the relationship may sound far-fetched, McClellan provides an illuminating explanation.
"Warmer temperatures generally mean greater crop yields, which means lower food prices, and eventually lower inflation, so interest rates come down. Similarly, crop failures and famines tend to arise more from cooling period for global average temperatures," McClellan wrote in a Thursday note.
"Whether or not that explanation satisfies everyone, the correlation between interest rates and the offset temperature data is hard to ignore," he adds, if a bit defensively.
McClellan uses the data to suggest that yields could see a short-term bottom, as temperatures temporarily bottomed around five years ago. But by 2017, they will head lower again.
No surprise, that, given that 2014 was the Earth's warmest year on record, according to NASA.
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But some market professionals are skeptical.
"It's a classic, just, two massive trends happening at the same time," said Larry McDonald, head of U.S. strategy at Societe Generale. He said bond yields have been in a nearly straight path lower due to aging in developed countries. As more and more people get older, they turn to purchases of bonds, leading to higher bond prices and lower yields.
Meanwhile, temperatures are rising due to human activities that emit greenhouse gasses like carbon dioxide.