How do we know about the climate 150,000 years ago?. Are scientists making stuff up?. Are they using time machines?. Climate data of the past Actual Measurements. Humans have been recording climate using instruments for only the past ~100-200 years.
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How do we know about the climate 150,000 years ago?
Are scientists making stuff up?
Are they using time machines?
Instruments to record temperature, wind, precipitation, etc
Bradley, R.S., 1991. Pre-instrumental climate: how has climate varied during the past 500 years?
Garcia et al. ManilaGalleons Voyage Records
Paleoclimatologists use paleoclimate proxies.
proxy: An indicator of past climate. A proxy (meaning “substitute”) is an indirect measure of climate, as opposed to direct measures such as reading temperature from a thermometer.
Introduction to proxy data video
Span = how far into the past the proxy information goes
Resolution = how specific the climate information is in terms of years
A higher resolution ca n give you information about a specific year.
A lower resolution will show long-term changes that occur over many years.
Time Limits of Various Proxy Data
location of proxy data
Combining all of the proxy data
Read the background information on tree rings. (see printed text)
Then click on the link below, You be the Dendochronologist and practice making different width rings and matching exising data. Follow the instructions on the page.
Complete your chart.
You be the dendochronologist
Read the text and watch the video. Click on coral video to link to the page.
2. Watch a short video (no sound) to see how the coral cores are collected.
3. Complete your chart
coral core collection (no sound)
How we measure past sea level from corals
Acroporapalmatais a coral that only grows in water that is less than 5 meters deep.
Therefore if it is found in a location, you can infer that that location was once under 5 meters or less of water.
Scientist drilling for coral
Packrats, as their name implies, constantly collect all kinds of materials from their surroundings. Their collections, called "middens", provide clues to the past climates of the region. Packrat middens are clumps of vegetation, insects, remains of vertebrates, and other materials cemented together by crystallized packrat urine (referred to as amberat). These rock-hard deposits can be more than 20,000 years old.
A sample of packrat midden from Red Creek (RC2) that dates to 3320 B.P. Needles of lodgepole pine were recovered from this midden found in the lower basin.
Packrat making a midden
Source: San Diego Natural History Museum
1. Watch the video and read the text. Click on the lake sediment proxy link to view the video.
Lake Sediment proxy data video and text
more information and pictures on lake sediments
2. Complete your chart.
Collecting a lake sediment core
Which proxy data would be appropriate for determining climate 1.5 million years ago?
Which proxy data would be appropriate for determining the climate around Hawaii?
If you were wondering if there was an ocean in Colorado, which type of proxy data would be appropriate?
Looking at your graphs, which type of proxies might have been used and why?
In your journal, explain to a skeptic: “How scientists know about the climate of the past.”
Jim White short version video of ice cores
Earth’s climate changes. Although there is debate over what causes this change, scientists agree that Earth’s climate has changed and continues to change over time. One way to learn about these changes is through the study of glacial ice cores. Ice cores create a layered historical record of the climate over time. Scientists drill deeper into older layers of ice; sometimes to a depth of over 3,500 meters (2.2 miles).
By performing physical and chemical tests on ice cores, scientists can create a snapshot of the Earth at single points in time. Atmospheric gases, from hundreds to thousands of years ago, are trapped as small bubbles within the ice.
Measurements of gases, including carbon dioxide, paint a picture of the atmosphere at the time the gases were trapped.
Figure 1. Ice Core Sampling. Image credit: RetoStöckii, NASA GSFC
map of drilling sites