Trees and Paleoclimate

Part A: Records of the Past: Predictions for the Future

Paleoclimatology is the study of ancient climates. The origin of the word is from the Greek word "paleo," which means ancient. Paleoclimatologists are scientists who study the ancient climate. Paleoclimate occurred before our modern weather instruments, such as thermometers, rain gauges, or barometers existed. Therefore, in order to gather data about the pre-instrumental era of climate, scientists use what are known as proxy records. Proxy records of climate are often stored in nature. From these preserved physical characteristics of Earth's past, scientists can reconstruct temperature records.

Proxy records are found in many forms including: ice of glaciers and ice sheets; sediments at the bottom of lakes and oceans; layers in coral; rings of trees; and even historical writings. While instrumental data can tell us about the past 150 years of climate, proxy records can take us back thousands to hundreds of thousands of years.

Watch this video about the single-celled organisms called foraminifera, found in ocean sediments, to get an idea of how scientists use them as a proxy records.

Visit the USGS Paleoclimate Archives to learn more about some sources (or archives) of proxy records. Click on Proxies, at the top of the same page when you're done, and look through the types of records in these archives that are used to reconstruct ancient climate.

Proxy records are important because they allow scientists to gather information about Earth's climate long before humans influenced the climate—or even existed! We know that Earth's climate is one of continuous and cyclical change. There have been times of great ice sheets (21,000 years ago) and tropical warmth at high latitudes (hundreds of millions of years ago).

Because paleoclimate records give us a much larger perspective of climate over time, they help us to see how the recent changes are compared to the changes that took place in the past. Not only are proxy records important for understanding the past climate, they help us to predict the future climate. Scientists and modelers often use proxy records to as a way to check their simulations of past and future climate in their models.

Examine the graphs and information in the PowerPoint file shown below. (Click on the thumbnail, below, to view the slide show online. When you are done viewing, click the words "exit presentation" to close the window.)

In the graphs of paleoclimate reconstructions, note the change in temperature as compared to the baseline or average of the past 30-50 years. While each method used to reconstruct the ancient climate is slightly different, the conclusions are similar: dramatic warming has occurred in the past 1000 years. Additionally, the most recent 20 years are the warmest on record in the past 1000—and possibly 2000—years. Think of this time frame in terms of civilizations and society, a lot has happened in those 2000 years. As you work through this section, keep in mind the role climate and weather has played in human history. 

As you view the PowerPoint file linked left, answer the Stop and Think questions listed below.

This PowerPoint file was adapted from Climate Change: Past, Present, and Future, presentation NSTA Climate Change Symposium, March 2011. Courtesy of: LuAnn Dahlman, NOAA.

Optional Extensions

 

Read about Ice Core Proxy Records

Read about Tree Core Proxy Records

Read about Coral Reef Proxy Records

Videos

National Geographic Education's video Global Warming in Greenland. introduces the work of a scientist who studies cave-based deposits of calcite in Greenland to better understand the area's climate history.

This US Ice Drilling video on YouTube looks at ice cores and the various proxy data available within them, Ice Cores as Proxies.

Beneath the Ice, Scientists in Antarctica study the ancient air composition trapped in Antarctic ice cores.

Tree Stories, The study of tree rings help scientists in Utah understand the history of stream flow in the region and plan for a future climate.

5 Clues to Earth's Climate History, Five different forms of proxy data.