Extreme temperature changes, high rainfalls and excessive heat are not only a result of humans’ impact on the environment, but can also occur in a natural way and in a short time.
A University study found that these dramatic climate changes can naturally take place over a period as short as 50 years. The study, published yesterday in Nature magazine, was led by University of Illinois ecologist Feng Sheng Hu, and seven other University researchers.
Professor Kerry Kelt, director of the University’s Limnological Research Center and one of the study’s researchers, said the group was trying to find out how sensitive climate is to any changes over time.
Kelts said minor changes in temperature over a large period of time can eventually lead to a sudden shift in the climactic trend.
The idea that climate can change in a short time has been around for about 10 years, said Emi Ito, associate professor in the Department of Geology and Geophysics at the University.
“One thing is that without human intervention, climate can change quickly,” Ito said.
In searching for records to document changes in climate, geologists dug out core samples during the winter from the bottom of Deep Lake in northern Minnesota. The research project took about three and a half years.
Core samples are sediments at the bottom of lakes that can record changes over a long period of time.
Kelts said the samples are “like tree rings” showing the annual changes as stripes.
From the sediment in the stripes, researchers can find traces of what the lake looked like thousands of years ago.
Calcium carbonate, crystallized within core samples, was studied in these sediments.
In the crystals researchers were able to find remains of carbon dioxide taken from the atmosphere and pushed into the lake over a long period of time.
Changes in the oxygen forms found in carbonate reflect shifts in the weather, allowing researchers to determine whether the lake was wet or dry.
Ito said core samples were then split, with a part used for research and another stored in archives.
From this core sample, they were able to determine that between 8,900 and 8,400 years ago there were extremely cold temperatures in the area for about 400 years.
Ito also said another part of this research involved comparing the results with other published research from a different time period.
In 1997, Richard Alley, a researcher at Pennsylvania State University, published a study about ice core samples from Greenland. According to Kelts, the ice samples measured the atmosphere, instead of vegetation.
This study, Ito said, is an average record of conditions of the Northern Hemisphere about 8,200 years ago and often used as comparison for studies such as the one performed at the University.