If the evidence for global climate change is not understood or the potential impacts recognized, the challenges these present to the world cannot be addressed. There must be familiarity with the evidence of global climate change and how new technologies and policies can help address its challenges. Knowing how key Earth systems are changing in response to climate change and how they have changed in the past is crucial to understanding how they will likely change in the future.

Similar to a doctor who checks a patient's vital signs-pulse, heartbeat, temperature, and so on-scientists regularly check Earth's vital signs, which informs us about the health of our planet: global temperature, atmospheric CO2, Arctic sea ice, land ice, and sea level.

Take a view from space at the "Blue Marble" and review your understanding of the Earth as a system. Watch the "Earth as a System" video and think about some of the interactions between the air, land, water, and life that transfer energy in and around the globe and contribute to our climate.

The next video, "A Subsistence Culture Impacted by Climate Change," explains how warmer temperatures in the Arctic are transforming the ecosystem and threatening the subsistence culture of the Athabaskan people. As you watch the video, notice all the ways that the changing climate is impacting the biosphere (plants and animals).

Meanwhile, in the tropics, local communities face different climate-change related challenges. Identify one of these challenges while watching "Samoa Under Threat".

While you may have heard about sea level rise, increased extreme weather events, and melting sea ice, to date we have had less media coverage on change occurring in temperate regions. View the video, "Witnessing Environmental Changes" and consider why that might be the case.

You may wish to take notes after reading the background essays and discussion questions for these resources.

Finally, read about the eight different changes in the Earth's surface discussed in "Climate Change - How Do We Know?" which provides compelling evidence that the Earth's climate is changing. As you read, think about how you would use these resources to help your students understand the evidence for global climate change.

Variation in carbon dioxide concentration during the past 400,000 years (historical data from the Vostock ice core).

Think about what you have learned in this section about the evidence that supports the idea of global climate change. What has challenged your own thinking and knowledge on global climate change?