Definition of Climate Proxy
In climate studies, a climate proxy refers to data sourced from natural records that document climate changes. These proxies offer indirect measurement of historic climate conditions, hence the term "proxy" suggests a substitute for direct measurement. With these records, it is possible to glean information about the Earth's climatic patterns going back hundreds to millions of years, far exceeding the timeline of human-recorded history.
Types of Climate Proxies
Climate proxies can originate from a range of physical, chemical, or biological phenomena. Natural substances including tree rings, ice cores, corals, marine and lake sediments, and stalagmites from caves are among the common sources.
Tree rings, under the study of dendrochronology, capture information on temperature, precipitation, and the occurrence of wildfires. Each ring typically represents one year of growth, enabling the exploration of climate variations across extended timeframes.
Ice cores harvested from glaciers and ice sheets preserve evidence of past temperatures and quantities of gases, carbon dioxide included, in the atmosphere. Analogous to tree rings, ice core layers correspond to years or sometimes seasons, with trapped tiny air bubbles serving as samples of the past atmosphere.
The composition of layers in corals and shells can reflect changes in sea surface temperatures and sea levels. Examination of the chemical makeup of layers in corals and certain types of shell-bearing plankton can provide indicators of shifts in sea surface temperatures and other marine conditions.
Layers of debris deposited over time form sediment cores in oceans and lakes. The nature of the sediment, along with remnants of organisms within each layer, can provide researchers with understanding about past climate conditions.
Use of Climate Proxies in Climate Science
In the field of climate science, proxy data are utilized to reconstruct previous climates and to understand natural variability within the Earth's climate. This long-term perspective helps scientists differentiate between climate variability of natural origin and those changes prompted by human activities.
Investigation of climate proxies and their implications forms a major part of paleoclimatology, the scientific study of past climates. By comparing historical climate proxy data with contemporary data, scientists can create models of climate change and make predictions about future climate trends.