Earth Warmer Now Than In Previous 1,400 Years, Global Study Reports

Apr 22, 2013

A man rides a scooter near giant globes displayed outside the walls of Jerusalem's Old City April 17, 2013. The globes exhibit, an initiative of the non-profit organization Cool Globes which aims to raise awareness of climate change, will be on display through the summer. (Photo : Reuters)

According to a report by The Earth Institute at Colombia University, the world's climate warmed more between 1971 and 2000 than during any other three-decade interval in the past 1,400 years.

The Institute cites a comprehensive climate reconstruction study that analyzed worldwide climate data from tree rings, pollen, cave formations, ice cores, lake and ocean sediments, and historical records from around the world that was authored by scores of scientists from 24 nations.

The study was recently published in the journal Natural Geoscience.

"This paper tells us what we already knew, except in a better, more comprehensive fashion," said study co-author Edward Cook, a tree-ring scientist at Lamont-Doherty Earth Observatory who led the Asia reconstruction.

The study also concluded that the summer 2003 heat wave which killed tens of thousands  in Europe happened during the hottest summer of the last 2,000 years.

According to the study's abstract, "There were no globally synchronous multi-decadal warm or cold intervals that define a worldwide Medieval Warm Period or Little Ice Age, but all reconstructions show generally cold conditions between AD 1580 and 1880, punctuated in some regions by warm decades during the eighteenth century. ... Recent warming reversed the long-term cooling; during the period AD 1971-2000, the area-weighted average reconstructed temperature was higher than any other time in nearly 1,400 years."

The report says scientists are nearly unanimous in their disagreement with those who believe the natural warming that occurred in the medieval ages is also what is happening today.

"If we went into another Medieval Warm Period again that extra warmth would be added on top of warming from greenhouse gases," said Cook. 

The environmental news website Mongabay, also writing about the global study, reports that temperatures have risen about 0.8 degrees Celsius (1.4 degrees Fahrenheit) in the last hundred years over land and sea due to burning fossil fuels, deforestation and other land-use changes, and industrial agriculture. The most recent decade was the hottest yet, according to the report.