Global warming temperatures are higher than in any period over the last 1,200 years, a study published in the journal Science shows.
A research team from the University of East Anglia in Britain measured changes in tree rings, fossil shells, ice cores and temperature records, including people’s diaries from 750 years ago. Their findings linked a warming of the climate with human activity.
Their study showed significant warmth in the Northern Hemisphere from 890-1170 A.D. and colder periods from 1580-1850.
The findings support evidence pointing to unprecedented recent warming of the climate linked with human activity.
Timothy Osborn and Keith Briffa of UEA analysed thermometer measurements of temperature from 1856 onwards to establish the geographic extent of recent warming, and then compared the data with evidence dating back as far as AD 800.
The UEA team showed that the present warm period is the most widespread and longest temperature anomaly of any kind since the ninth century.
Dr Osborn and Dr Briffa used 14 sets of temperature records from different locations across the Northern Hemisphere, including long life evergreen trees growing in Scandinavia, Siberia and the Rockies which were cored to reveal the patterns of wide and narrow tree rings over time. Wider rings related to warmer temperatures.
The chemical composition of ice from cores drilled in the Greenland ice sheets revealed which years were warmer than others.
The researchers also used proxy data developed from the diaries of people living in the Netherlands and Belgium during the past 750 years that revealed, for example, the years when the canals froze.
[Source: GameSouth]
