World at its Warmest for Past 1200 Years

By Freddie Mooche

Washington - Since modern record-keeping began around the 1850s, the world is at its warmest for the 20th century, but scientists say there is even more astounding news regarding the weather.

Since the middle of the 20th century, the northern hemisphere is at its warmest its ever been for the past 1200 years, which researchers reported on in the latest Scientific Journal.

The researchers findings were based on comparisons of the current warm period to other hot and cold intervals since the year 800. The research was conducted at the University of East Anglia in Norwich, UK by two climate scientists. The scientists were attempting to find out whether the current warm period was a natural phenomenon, brought about by the fluctuations of temperatures that occured over time in different parts of the world, or abnormal changes in warmth that could be attributed to man-made intervention.

The researchers looked at long periods of alternating temperatures were the Little Ice Age sent Northern Europe into a deep freeze and the Medieval Warm Period around 1000 to see if the warmer temperatures the Northern Hemisphere is experiencing is abnormal.

Their findings appear to point to global warming being man-made, not a natural fluctuation. In the context of natural changes in the last 1,200 years the evidence uncovered by the researchers shows that warmer temperatures are probably related to greenhouse gas emissions from human activity.

Researchers looked at the signs that temperatures left in tree rings, ice cores and seashells from 14 sites across North America, Europe and Asia to compare temperature changes as record have only been kept for the last 150 years, so they had to find alternative sources to examine changes in the atmosphere earlier than that. Two of the temperature estimates were from Canada -- one from tree-ring measurements taken in the Rockies near the Columbia Ice Field, the other from tree rings in a Northern Quebec boreal forest.

Other records were based on tree samples from the United States, Austria, Sweden, Russia and Mongolia, among others, along with Greenland ice cores and seashells from Chesapeake Bay in the United States. Tree rings are an excellent gauge of past climate conditions, particularly if the trees are from cold-weather locations near the tree line, where growth is highly dependent on temperature conditions.

Dr. Timothy Osborn, one of the researchers, said that in such places, the amount of growth is limited by how warm the summer is. Dr. Osborn said the 20th century was remarkable for the geographical extent of the warming because "all records indicate warm conditions at the same time." Reliable records from trees and other sources go back only about 1,200 years, but this allowed the researchers to measure the magnitude of the current bout of warming against two of the best known long-term weather conditions, the Little Ice Age from about 1580 to 1850, and the Medieval Warm Period from 890 to 1170.