Take a look at this video "What's REALLY Warming the Earth" which is put out by PBS Digital Studios. It provides an explanation of the influence of different factors (Earth's orbit, solar intensity, etc) on Earth's temperature. The final conclusion is that increasing global temperatures in the last 100+ years are caused by human actions. (6:00 min.)

Remember that the Keeling Curve PICS video we watched in the first section.  This video provided different evidence of a human role: chemical fingerprinting of carbon dioxide in our atmosphere identifies the source as burning fossil fuels.

These videos and others from this section referred to information about instrumental measurements to help us understand Earth's climate.

You may be wondering, or at least your students/program participants may wonder how do we know about Earth's climate prior to the creation of thermometers and satellites? Well...take a look at NOAA's introduction to how we know what we know about the climate in the past. And this NOAA page that defines proxy data and provides information about several different sources of proxy data.

One type of physical sample that is often collected in order to learn more about Earth's past climate is the ice core. Ice cores can be collected from large ice sheets, such as those on Greenland and Antarctica, and from mountain glaciers.

Watch "At the Core of Climate Change" (19:29) As you watch, take some notes on different types of information that researchers learn from the cores and what tools and techniques they use to gather data. How could you model these efforts in your classroom or center?