Paleoclimate of the last 2k years

Sean Bryan, Colorado State University

Initial Publication Date: May 23, 2022

Summary

Paleoclimate data provide essential information about Earth's temperature prior to the instrumental record. These data give us context for recent anthropogenic (human-caused) warming; they provide insight into the impacts of climate change, and they provide targets for the assessment of climate models. This activity explores trends in global and local temperature during the last 2,000 years, and considers the uncertainties in interpreting individual records. Through this activity, students will gain experience downloading data from an online repository, managing data in Excel, plotting data in scatter plots, and calculating trends using regressions. Students also gain exposure to some of the challenges of working with paleoclimate data, which may include discontinuous time-series, low resolution, and influences other than temperature on proxy variables.

Strengths of Module

This module explores paleoclimate data and their sources, which provide context for recent anthropogenic warming and information about how the climate system operates. In this module, students engage with sometimes messy data, explore the sources and limitations of individual paleoclimate records, and compare individual records to a global composite record for the past 2,000 years. Students build skills plotting time-series data and trendlines in Excel. Students also present a dataset of their choosing to the class in a gallery walk.

What does success look like

The overall goal for this module is for students to be able to think critically about paleoclimate reconstructions, recognizing the value and limitations of individual records. Students will be able to graph time-series data using Excel and analyze the data to find out: the length of the data set, the average resolution of the data set, and if there any trends in the data. Students will be able to describe how global temperatures have changed over the past 2,000 years. Students will be able to compare individual time series to the global composite, consider the uncertainties in proxy data, and explain some potential reasons why they may differ.

Context for Use

This module was developed for a lower division level Historical Geology course. It may also fit well into an Introductory Geoscience, Global Change, or Paleoclimatology course. It is designed to be completed over one 50-minute class session used for discussion of the video and presentation of the powerpoint and one 3 hour lab period used for Activities A, B, &C. However, it could be adapted to be completed in 2-3 class sessions. Students will need access to computers with Microsoft Excel and a connection to the internet. The module could be used in either an in-person or online environment. This module could be used on its own or as an extension to the Project EDDIE Climate Change Module.

How Instructors Have Used This Module

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Using Project EDDIE modules in Historical and Analytical Geology
Sean Bryan, Colorado State University
The Paleoclimate of the Last 2k Years Module examines the very recent geologic record of climate change and sets the stage for Anthropogenic climate change. It gives students practice graphing data in MS Excel, determining trends, and interpreting real proxy records. The module may be useful in a range of courses including Introductory Geoscience, Historical Geology, Global Change, Paleoclimatology, etc.

Description and Teaching Materials

Why this Matters:

Paleo-records of climate provide us with valuable context for modern anthropogenic warming. They inform us about natural mechanisms of climate change, variability on various timescales, and rates of change. They help us understand how anomalous the current warming is. Paleoclimate information comes from a variety of different archives (trees, corals, ice cores, lake and ocean sediments, etc.) and a variety of different types of proxies (physical, biological, geochemical). Any individual record contains uncertainties related to the proxy and archive type, location, age and resolution, and may or reflect broader regional or global trends. Proxy records can be compiled and averaged to uncover broader patterns. This module explores the concept of how individual records fit into the global pattern.

Quick outline/overview of the activities in this module

  • Pre-module work: Watch Taking Earth's Temperature (length: 57 minutes)
  • Activity A: Examine the global composite temperature record of the past 2,000 years.
  • Activity B: Examine an individual paleoclimate record.
  • Activity C: Compare and contrast the individual record with the global composite.

Pre-module work

The ~60-minute pre-module video introduces the use of paleoclimate proxies in reconstructing Earth's temperature and the PAGES 2k Network. There are optional "pre-lab" questions based on the video which could be used. The Instructor's Powerpoint linked below provides further background information on different paleoclimate proxies. If a shorter introductory video is desired , NSF's Reconstructing Climate History, How Do We Know?, provides a brief introduction to paleoclimate proxies.

Activity A

  1. Download and graph the global composite temperature record.
  2. Qualitatively describe the time-series.
  3. Add a trendline to estimate the long-term trend in temperature.
  4. Sub-sample the most recent part of the record and calculate warming trend.

Activity B

  1. Select, download and graph an individual proxy data set.
  2. Describe time-series and calculate trends.

Activity C

  1. Compare and contrast individual records to the global composite temperature record.
  2. Conduct a gallery walk of individual records.

Teaching Materials:

  • Potential Pre-lab questions (Microsoft Word 2007 (.docx) 16kB May20 22), based on PBS Video
  • Student Handout (Microsoft Word 2007 (.docx) 29kB May20 22)
  • Datasets are linked within the References and Resources section below
  • Offline version of the global composite data set (Text File 113kB Oct29 19)
  • Offline version of 32 individual records EDDIE_2KPaleolimate_Offline-files.xlsx (Excel 2007 (.xlsx) 476kB May20 22)

Teaching Notes and Tips

See the Instructor's Manual

References and Resources

Background information about the PAGES 2k Project: http://www.pastglobalchanges.org/science/wg/2k-network/intro

Article reference for the global composite temperature reconstruction: https://www.nature.com/articles/s41561-019-0400-0

PAGES 2k Consortium. Consistent multidecadal variability in global temperature reconstructions and simulations over the Common Era. Nat. Geosci. 12, 643–649 (2019). https://doi.org/10.1038/s41561-019-0400-0

Data source for the global composite temperature reconstruction: https://www.ncdc.noaa.gov/paleo-search/study/26850

Article reference for the PAGES 2k Database: https://www.nature.com/articles/sdata201788

PAGES2k Consortium. A global multiproxy database for temperature reconstructions of the Common Era. Sci Data 4,170088 (2017). https://doi.org/10.1038/sdata.2017.88

Data source for the PAGES 2k Database: https://www.ncdc.noaa.gov/paleo-search/study/21171

More potential background information: https://www.nap.edu/read/11676/chapter/3#11