14.1: Background
- Page ID
- 28611
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The past 800,000 years includes our current time period, the Holocene, and the last third of a much longer period called the Pleistocene. The Pleistocene is a geologic epoch that lasted from 2.6 million years ago (mya) to about 11,700 ya. Sometimes referred to as the Ice Age, the Pleistocene is actually a period of repeated glaciations separated by warm periods. The Holocene, on the other hand, is a twelve-millennium time span during which human civilization emerged and developed. In other words, it is the part of the geologic calendar we now live in.
In this set of activities, you will be looking at five key variables that are involved in the questions above.
- Global temperature – The graph for this in Dashboard is actually for temperature anomaly. This anomaly is the difference between the Mean Global Temperature (MGT) for a given year and the average of MGTs over an extended period of time.
- Sea level – The graph for this shows mean global sea level in relation to present sea levels. Present levels being zero.
- Carbon dioxide levels – The graph for this show atmospheric concentration of \(CO_{2}\) in parts per million.
- Eccentricity and tilt – Characteristics of the earth’s orbit and rotation that influence the amount, distribution, and timing of energy received from the sun – a key driver of climate.