In the late 20th century, the northern hemisphere experienced its most widespread warmth for 1,200 years, according to the journal Science. The findings support evidence pointing to unprecedented recent warming of the climate linked to greenhouse emissions. University of East Anglia(UEA) researchers measured changes in fossil shells, tree rings, ice cores and other past temperature records. They also looked at people's diaries from the last 750 years. Timothy Osborn and Keith Briffa of UEA analysed instrument measurements of temperatures from 1856 onwards to establish the geographic extent of recent warming. Then, they compared this data with evidence dating back as far as AD 800. The analysis confirmed periods of significant warmth in the northern hemisphere from AD 890 to 1170 (the so-called "Medieval Warm Period") and for much colder periods from AD 1580 to 1850 (the "Little Ice Age").
- ①Researchers at UEA examined a variety of materials to check temperature changes.
- ②The Medieval Warm Period was shorter than the Little Ice Age.
- ③The late 20th century is not the first in history that witnessed a temperature change.
- ④Greenhouse emissions are considered to be the cause of the recent warming.
정답 ②
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