Trees and Paleoclimate
Part A: Records of the Past: Predictions for the Future
Proxy records are found in many forms including: ice of glaciers and ice sheets; sediments at the bottom of lakes; 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. Take look at some of the methods used to reconstruct ancient climate on this website: Paleoclimate.
Proxy records are important because they allow scientists to gather information about Earth's climate long before humans influenced the climateor 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).
Take a tour back in climate history with the Climate Timeline.
While exploring the timeline take notes on the following: note the timescales shown on the timeline, the climate science described above the timeline, and the climate history displayed below the line. Answer the following Checking In questions as you view the climate timeline.
- What are powers of ten?They are on the exponential scale. Each step is 10X the last one.
- What types of changes in weather take place on a daily scale?Weather can change dramatically within a day; it can rain, be sunny, or even start to snow, all with in a matter of hours.
- What climate changes occur on a decadal (10-year) scale?Events like El Niño take place on a decadal scale.
- How would you describe the climatic conditions between 104 and 103 years ago? What major events took place?Several major climatic shifts took place in the past 10,000 years. The last of the ice-age glaciers melted, causing flooding. There was drought in the American southwest that may have caused the Anasazi peoples to vanish.
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 1000and possibly 2000years. 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.
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: Download and view the complete Climate Change: Past, Present, and Future (PowerPoint 2.3MB Dec10 12) PowerPoint file.
Stop and Think
- Define paleoclimatology and name three types of proxy data.
- How is proxy data different from instrumental data?
- What trends in the temperature record (from the past 150 years) do the proxy data and instrumental data both show?