This video is part two of a seven-part National Academies series, Climate Change: Lines of Evidence. The video outlines, with the use of recent research and historical data, how we know that the Earth is warming.

In this activity, students examine images of alpine glaciers to develop an understanding of how glaciers respond to climate change. They record, discuss, and interpret their observations. They consider explanations for changes in the size and position of glaciers from around the world. They develop an understanding that the melting (retreat) of glaciers is occurring simultaneously on different continents around the world, and, thus, they represent evidence of global climate change.

In this video clip, Climate Central's Dr. Heidi Cullen explains that what we've known as "normals" for our climate, during the past decade, will very likely change soon. The new climate normal will provide key information for decisions we make in the future, ranging from what we plant, to what we pay for energy, and even to where we take a vacation.

This short video clip summarizes NOAA's annual State of the Climate Report for 2009. It presents a comprehensive summary of Earth's climate in 2009 and establishes the last decade as the warmest on record. Reduced extent of Arctic sea ice, glacier volume, and snow cover reflect the effects of rising global temperature.

In this video, students learn that scientific evidence strongly suggests that different regions on Earth do not respond equally to increased temperatures. Ice-covered regions appear to be particularly sensitive to even small changes in global temperature. This video segment adapted from NASA's Goddard Space Flight Center details how global warming may already be responsible for a significant reduction in glacial ice, which may in turn have significant consequences for the planet.

In this video from the Polaris Project Website, American and Siberian university students participating in the project describe their research on permafrost.

This interactive displays how climate variables are changing over time (temperature, CO2, Arctic sea ice, solar flux, etc.) in graphical form. Students can examine data over the last 20 years or archived data.

The activity takes a hands-on approach to understanding El NiÃo by physically showing and feeling the process. It consists of an El NiÃo demo to be performed by the teacher and observed by the class as well as an experiment to be conducted by the students themselves individually or in pairs to illustrate the connection between water temperature and atmospheric temperature. Students are asked to make conclusions based on their findings and then examine the chain of events stemming from El NiÃo.

This short video discusses where carbon dioxide, the gas that is mainly responsible for warming up our planet and changing the climate, comes from. It discusses how the rise in atmospheric carbon dioxide comes directly from the burning of fossil fuels and indirectly from the human need for energy.

This short cartoon video uses a simple baseball analogy (steroid use increases probability of hitting home runs) to explain how small increases in greenhouse gases can cause global temperature changes and increase the probability of extreme weather events.