Peruvian stalagmites hold clues to climate change

Science Daily: How will the Netherlands, dominated by water, be affected by future climate change? Dutch researcher Martin van Breukelen hopes to answer that question by analyzing stalagmites from the South American Amazon tributaries in Peru as a way to reconstruct climate changes in the past.

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 analyzed 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 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. ….

Leçons élémentaires de chimie (B.Bussard, H.Dubois) 1906 page 49.