Previous research had extended back roughly 1,500 years, and suggested
that the rapid temperature spike of the past century, believed to be a
consequence of human activity, exceeded any warming episode during those
years. The new work confirms that result while suggesting the modern
warming is unique over a longer period.
In the new research, scheduled for publication on Friday in the journal Science, Shaun Marcott, an earth scientist at Oregon State University,
and his colleagues compiled the most meticulous reconstruction yet of
global temperatures over the past 11,300 years, virtually the entire
Holocene. They used indicators like the distribution of microscopic, temperature-sensitive ocean creatures to determine past climate.
Scientists say
that if natural factors were still governing the climate, the Northern
Hemisphere would probably be destined to freeze over again in several
thousand years. “We were on this downward slope, presumably going back
toward another ice age,” Dr. Marcott said.
Instead, scientists believe the enormous increase in greenhouse gases
caused by industrialization will almost certainly prevent that.
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