The current period of global warming is the most widespread and longest temperature anomaly of any kind for 1,200 years, scientists revealed today.
Researchers Timothy Osborn and Keith Briffa, from the University of East Anglia in Norwich, England, measured changes in tree rings, fossil shells and ice cores from 14 sites around the world.
The data, charting the world's climate history back to the Dark Ages, show that global warming in the 20th century had more impact than any previous hot or cold spell since the ninth century.
In the time investigated, there were hot spells from the years 890 to 1170 and cold snaps in 1580 and 1850. These northern hemisphere anomalies coincided with the Medieval Warm Period and the 16th century's Little Ice Age.
But neither was as significant as the era of global warming that gained momentum at the end of the 20th century.
The researchers, whose findings were published in the journal Science, wrote: "The most widespread and thus strongest evidence indicative of a significantly warm period occurs during the 20th century, when greenhouse gas concentrations were at their highest during the analysis period.
"The proxy records indicate that the most widespread warmth occurred in either the mid or late-20th century, but instrumental temperatures provide unequivocal evidence for continuing geographic expansion of anomalous warmth through to the present time."
PA