d. Gradual changes in Earth's rotation and orbit around the sun change the intensity of sunlight received in our planet's polar and equatorial regions. For at least the last 1 million years, these changes occurred in 100,000-year cycles that produced ice ages and the shorter warm periods between them.

This unit allows students to investigate past changes in Earth's climate. Students first explore relationships in climate data such as temperature, solar radiation, carbon dioxide, and biodiversity. They then investigate solar radiation in more depth to learn about changes over time such as seasonal shifts. Students then learn about mechanisms for exploring past changes in Earth's climate such as ice cores, tree rings, fossil records, etc.

This 10 minute video builds connections between topics that are important in climate science such as: the impact of variations in Earth's orbit and wobble on it's axis on climate; how the cores being sampled fit into the bigger climate picture; connecting greenhouse gases to melting ice and sea level changes; the sensitivity of the ice melt / sea level rise relationship; and computer model simulations showing connections between ice sheets and sea level.
The companion website provides resources, an extensive list of activities, teacher guides, posters, and more.

Climate has varied in the past, but today's climate change rate is much more drastic due to human activity. Students explore past climate cycle graphs and compare the cycles with the current rate of change.

An applet about the Milankovitch cycle that relates temperature over the last 400,000 years to changes in the eccentricity, precession, and orbital tilt of Earth's orbit.

In this 6-part activity, students learn about climate change during the Cenozoic and the abrupt changes at the Cretaceous/Paleogene boundary (65.5 million years ago), the Eocene/Oligocene boundary (33.9 million years ago), and the Paleocene/Eocene boundary (55.8 million years ago).

This figure shows the various astronomic cycles that influence long-term global climate cycles (Milankovitch cycles), plotted on the same time scale for easy comparison.

This video segment, from the 'Earth: The Operators' Manual' featuring climate expert Richard Alley, shows how ice cores stored at the National Ice Core Lab provide evidence that ancient ice contains records of Earth's past climate - specifically carbon dioxide and temperature.

This short video, adapted from NOVA, explains how Earth's position relative to the Sun might be responsible for the dramatic shift in the climate of what is now the Saharan nation of Djibouti.

This is a video overview of the history of climate science, with the goal of debunking the idea that in the 1970s, climate scientists were predicting global cooling.

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