NCPA - National Center for Policy Analysis

Medieval Warm Period Was Global Event

March 29, 2012

Current theories of the causes and impact of global warming have been thrown into question by a new study that shows that during medieval times the entire planet heated up.  It then cooled down naturally, says the Daily Mail (U.K.).

  • A team of scientists led by geochemist Zunli Lu from Syracuse University has found that contrary to the "consensus," the Medieval Warm Period approximately 500 to 1,000 years ago wasn't just confined to Europe.
  • In fact, it extended all the way down to Antarctica -- which means that Earth has already experience global warming without the aid of human carbon dioxide emissions.

At present the Intergovernmental Panel on Climate Change argues that the Medieval Warm Period was confined to Europe -- therefore that the warming we're experiencing now is a man-made phenomenon.

  • However, Professor Lu has shown that this isn't true -- and the evidence lies with a rare mineral called ikaite, which forms in cold waters.
  • "Ikaite is an icy version of limestone," says Lu. "The crystals are only stable under cold conditions and actually melt at room temperature."
  • It turns out the water that holds the crystal structure together -- called the hydration water -- traps information about temperatures present when the crystals formed.
  • This finding by Lu's research team establishes, for the first time, ikaite as a reliable way to study past climate conditions.

The scientists studied ikaite crystals from sediment cores drilled off the coast of Antarctica.  The sediment layers were deposited over 2,000 years.

The scientists were particularly interested in crystals found in layers deposited during the "Little Ice Age," approximately 300 to 500 years ago, and during the Medieval Warm Period before it.  Both climate events have been documented in Northern Europe, but studies have been inconclusive as to whether the conditions in Northern Europe extended to Antarctica.

Lu's team found that in fact, they did.  They were able to deduce this by studying the amount of heavy oxygen isotopes found in the crystals.  During cool periods there are lots, during warm periods there are not.

Source: Ted Thornhill, "Is This Finally Proof We're NOT Causing Global Warming? The Whole of the Earth Heated up in Medieval Times without Human CO2 Emissions, Says New Study," Daily Mail (U.K.), March 26, 2012.


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