In historical sciences, observable phenomena are often used as indicators of past phenomena.  Some recent examples show how these can mislead researchers.

Ice cores:  A press release from University of Wisconsin-Madison, echoed on NASA’s Astrobiology Magazine, has climate scientists scrambling.  For decades, they have used Greenland ice cores as proxies for historical climate change, particularly the ratios of oxygen isotopes in bubbles in the ice.  Now, research has shown that these ratios are misleading and can exaggerate temperatures.  The press release is concerned with one particular period scientists have labeled the Younger Dryas, alleged to be 13,000 years ago, when the temperature supposedly plummeted, according to the old interpretation of oxygen ratios in Greenland ice.  Trouble is, that indicator is at odds with other indicators.

“We don’t believe the ice cores can be interpreted purely as a signal of temperature,” says Anders Carlson, a University of Wisconsin–Madison geosciences professor. “You have to consider where the precipitation that formed the ice came from.”

So, will a simple correction bring the data into conformance with theory?  “It’s a fresh reminder from an ancient ice core that climate science is full of nuance,” Carlson said.  “Abrupt climate changes have happened, but they come with complex shifts in the way climate inputs like moisture moved around.  You can’t take one difference and interpret it solely as changes in temperature, and that’s what we’re seeing here in the Greenland ice cores.”

Gravitational lenses:  A press release from JPL today has cosmologists worried.  They found an arc of light where it shouldn’t be.  According to theory, arcs are the light of distant galaxies distorted by intervening matter.  “The giant arc is the stretched shape of a more distant galaxy whose light is distorted by the monster cluster’s powerful gravity, an effect called gravitational lensing,” the article explained.  “The trouble is, the arc shouldn’t exist.”  This sent one observer of the Hubble image into a psychological crisis:

“When I first saw it, I kept staring at it, thinking it would go away,”said study leader Anthony Gonzalez of the University of Florida in Gainesville, whose team includes researchers from NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “According to a statistical analysis, arcs should be extremely rare at that distance. At that early epoch, the expectation is that there are not enough galaxies behind the cluster bright enough to be seen, even if they were ‘lensed,’ or distorted by the cluster….

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