How’s the Weather in China?

High in the Qilian mountains of China, near the northern border of Tibet, German geo-scientists and their Chinese colleagues are busy boring holes deep into glacial lakes. They are collecting sediment formed at the end of the last ice age, some 18,000 years ago. This ancient sediment will help them determine what the climate was like, and how it has changed in the last few millennia.

For the past 10 years scientists from the Free University in Berlin and the Lanzhou University in northwestern China have been studying the climate history of Central Asia. The region is of special interest to the geologists because it’s located on the border between the western wind zone and the Asian summer monsoons, an area particularly sensitive to changes in wind circulation systems.

A change in wind circulation patterns in the northern hemisphere is a good indicator of long-term climactic changes. And this is what the scientists are really looking to find out.

Meteorological archive

Over thousands of years, meter-thick layers of rock and sediment build up on the bottom of undisturbed glacial lakes. These layers contain a high amount of limestone and fossilized remains of small living organisms such as shellfish and algae as well as grains of pollen from surrounding vegetation.

By analyzing these historical traces, geologists have a good idea of the environmental conditions pervading at the time of the sediment formation. They can determine the depth of the lake, the salt content and the level of carbon and oxygen in the water. Based on the type of fossilized plant and animal life found in the soft limestone rock, the scientists can also figure out the extent of ecological diversity at the time of the lake’s build up.

All these parameters provide clues to what the weather was like for each layer of sediment, and how rapidly it changed over time. In this regard, the sediment layers serve as a type of meteorological archive.

Working jointly in research laboratories in China and Germany, the scientists analyze the data collected and draw conclusions on the weather patterns for the last 14,000 years. This information is then used for establishing a climate model for predicting future climate development.