First Compilation of Tropical Ice Cores Shows Abrupt Global Climate Shift
Space and Earth science : June 27, 2006
physorg.com
For the first time, glaciologists have combined and compared sets of ancient climate records trapped in ice cores from the South American Andes and the Asian Himalayas to paint a picture of how climate has changed – and is still changing – in the tropics.
Their conclusions mark a massive climate shift to a cooler regime that occurred just over 5,000 years ago, and a more recent reversal to a much warmer world within the last 50 years.
The evidence also suggests that most of the high-altitude glaciers in the planet’s tropical regions will disappear in the near future. The paper was included in the current issue of the journal Proceedings of the National Academy of Science.
Lastly, the research shows that in most of the world, glaciers and ice caps are rapidly retreating, even in areas where precipitation increases are documented. This implicates increasing temperatures and not decreasing precipitation as the most likely culprit....
...“We have a record going back 2,000 years and when you plot it out, you can see the Medieval Warm Period (MWP) and the Little Ice Age (LIA),” Thompson said. During the MWP, 70O to 1000 years ago, the climate warmed in some parts of the world. The MWP was followed by the LIA, a sudden onset of colder temperatures marked by advancing glaciers in Europe and North America.
“And in that same record, you can clearly see the 20th Century and the thing that stands out – whether you look at individual cores or the composite of all seven – is how unusually warm the last 50 years have been.
“There hasn’t been anything in the record like it – not even the MWP,” Thompson said....
...the more dramatic evidence is the emergence of unfossilized wetland plants around the margin of the Quelccaya ice cap, uncovered as the ice retreated in recent years.
First discovered in 2002, the researchers have since identified 28 separate sites near the margin of the ice cap where these ancient plants have been exposed. Carbon-dating revealed that the plants range in age from 5,000 to 6,500 years old.
“This means that the climate at the ice cap hasn’t been warmer than it is today in the last 5,000 years or more,” Thompson said. “If it had been, then the plants would have decayed.”
The researchers say a major climate shift around 5,000 years ago in the tropics had to have cooled the region since the ice cap quickly expanded and covered the plants. The fact that they are now being exposed indicates that the opposite has occurred – the region has warmed dramatically, causing the ice cap to quickly melt.... |
