Peruvian stalagmites a new basis for 'Inconvenient truth'?

Information that can be used to test climate models is stored in various forms; in ice formations, plant remnants, oceans and caves. Limestone formations in caves, so-called speleothemes, provide insights into the land climate. The best-known speleothemes are stalagmites, standing formations and stalactites, hanging formations. Van Breukelen discovered stalagmites in South America that provide information about the climate over the past 13,000 years.

In order to study climate change, Van Breukelen analysed the accumulation of oxygen isotopes in both the cave water and the stalagmite. A small quantity of fossil cave water is enclosed in the core of the stalagmite, so-called fluid inclusions. The entrapped water is just as old as the carbonate of the stalagmite in which it is trapped. The isotope ratio of this fossil water can be measured using an extraction technique. As this water has been entrapped for thousands of years it provides unique information about the climatic history.

Much climate research on the land and sea is based on the measurement of subtle changes in the ratio between stable oxygen isotopes in, for example, ice or stone formations. Isotopes of an element can have different numbers of neutrons but always contain the same number of protons. Light isotopes (¹⁶O) respond differently to climate change than heavier isotopes (¹⁸O). Climate changes result in an altered ratio of the ¹⁶O and ¹⁸O isotopes. The ratio of the different isotopic elements oxygen, carbon and hydrogen provides a lot of useful information about the climatic history. Van Breukelen uses this information to reconstruct the changes in temperature and precipitation.

Climate research reveals that even without human influence the Earth's climate was changeable in the past. To what extent humans have influenced climate change since the industrial revolution remains unclear. It should be remembered that studies into climatic history can provide insights into the natural behaviour of the climate in the past. Additionally current climate models can only be improved if more historical data become available so that the accuracy of these models can be tested. The research method used by Van Breukelen that examines stalagmites is vitally important for climate research. This method allows the accurate reconstruction of independent temperature changes and precipitation patterns from thousands of years ago.

Van Breukelen's research was funded by a grant from the NWO division WOTRO Science for Global Development.

Provided by NWO