SW Paleoclimate

About - SW Paleoclimate

Paleoclimatology is the study of past climates, prior to the time when instrumental records from thermometer and rains gages are available.  In the Southwest, the longest instrumental records date back about 100 years.  Understanding the climate of the past is important for understanding the current climate, including extreme events such as drought, in a long-term context.  For example, are the drought conditions that much of the Southwest has been experiencing over the past couple of decades unusual, and due to anthropogenic climate change? Or are these conditions part of the natural variability of the climate system?  The instrumental record of climate is only 100 years and not long enough to document rare events, such as multi-decadal droughts, that many happen only every couple of centuries. 

Paleoclimate data come from a variety of environmental recorders that reflect climate. In the Southwest, these including historical documents, tree rings, layers of organic and mineral materials that accumulate in the bottoms of lakes, packrat middens, and cave formations called speleothems.  The climate proxy records that come from these environmental recorders reveal different aspects of climate, at different space and time scales. Using tree rings as an example, tree-ring widths can record annual variations in seasonal rainfall.  Southwestern conifers, the most useful trees for recording past moisture variability, are found throughout the region mostly above 4000 feet and can grow to be 300-500 years old, or older.  In the Southwest, tree-ring records have been particularly useful for shed light on the length and severity of past droughts.


Tree Ring Cross Section, Sediment Core being sampled from a lakebed, Close up of mineral deposits in a cave

Growth layers in tree rings, mineral deposits in caves (speleothems), and layers of mud, sand, and organic material in cores taken from the bottom of a lake all provide evident of past environmental conditions.

Photo Credits: Past Global Changes - PAGES (https://pastglobalchanges.org/news/129255), Carleton College (https://cdn.serc.carleton.edu/images/microbelife/topics/proxies/sedimen…), and C. Woodhouse

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