Social Studies

Social Studies

Lesson 1.3

Word Cloud

What is one word that you think of when you hear, climate change?

SOURCES FOR RECONSTRUCTING
THE HISTORY OF CLIMATE

Even if a scientist or a scholar is equipped with an understanding of how climate operates and how

climate change can occur, more information is needed to reconstruct the actual history of climate. Like

any other historical investigation, scholars need to have sources that provide evidence of past events. In

standard historical practice, historians examine written sources that are collected and stored in an
archive—typically a physical collection of documents. Scholars who study climate history have adopted
the concept of an archive to describe where they find the sources they use. Sometimes, scholars who
study climate also examine written documents for clues about past climatic conditions. Scholars have
called the places that hold these types of sources “archives of society.” But climate scholars also search
nature itself for clues about climate’s history. Scholars call these figurative storehouses of sources the
“archives of nature.”

Open Ended

What are some ways you'd construct (make) a history of climate change?

The Archives of Nature

As discussed earlier, climate influences the four subsystems—earth, water, air,
and living organisms—in many different ways. Certain climatic conditions might
correspond with specific gases in the atmosphere, or the growth of certain plants,
or certain water levels,and so forth. Traces of those impacts are sometimes found
in the natural world. In fact, nature is an archive,or a repository, of clues about
how climate and the different parts of our world interacted in the past. Scientists
and scholars have creatively developed methods for observing and measuring
evidence of past climatic conditions that have been preserved in different parts of
the world.

Open Ended

What are some items you'd use to from nature as evidence of past climate change?

Something observable in nature that gives an indication

of past climate conditions is called a proxy. Proxies are

natural features that show evidence of being impacted

by specific climate conditions. If scholars can isolate

and date these proxies, they will have an idea of what

the climate was like at a certain time in the past. Three

of the most revealing sources of climate history are ice,

trees, and soil.

Ice Cores

Ice core sampling is a technique of drilling long

cylinders of ice out of deep glaciers. The ice cores are

then analyzed in layers. As the ice was formed, the

snowfall from each year that became the new top layer

of the glacier would trap particles from the atmosphere

and freeze them in the ice. Therefore, an ice core

from an old glacier can reveal what the atmospheric

conditions were dating as far back as hundreds of

thousands of years.

Source: National Science Foundation, About Ice Cores | NSF Ice Core Facility

Open Ended

Why would an ice core be a good source of information on climate change for scientists?

Trees

Trees can also be analyzed for information about past climatic conditions. One can identify the age of a tree by
counting the rings of a tree that has been cut through. Scientists know how to analyze each of those rings for
information about the weather during that year of the tree’s life. The tree can reveal if the year was dry or rainy and can
even show the weather conditions of individual seasons in a year. The practice of gathering this information from trees
is called dendrochronology—a combination of words that refer to trees and time.

Sedimentation and Other Sources

Scholars also study other parts of the natural world

for data that has been collected about past conditions.

The layers of sediment or mud on the bottom of lakes

and the ocean contain information about the historical

composition and content of water such as the amount
of

pollen. Coral sampling in the ocean reveals similar data

as well as past temperatures of the ocean in the
location of the coral. Scientists creatively harvest data
about the impact of past climate conditions on various
parts of the Earth System and its subsystems. Through
such discoveries, scholars learn about the climate of
the past.

Multiple Choice

According to our text (the slides), a proxy is

• the most revealing sources of climate history are ice,

  trees, and soil.

• natural features that show evidence of being impacted

  by specific climate conditions.

•  layers of sediment or mud on the bottom of lakes

• where scientists save their work