b. Environmental observations are the foundation for understanding the climate system. From the bottom of the ocean to the surface of the Sun, instruments on weather stations, buoys, satellites, and other platforms collect climate data. To learn about past climates, scientists use natural records, such as tree rings, ice cores, and sedimentary layers. Historical observations, such as native knowledge and personal journals, also document past climate change.

This series of visualizations show the annual Arctic sea ice minimum from 1979 to 2015. The decrease in Arctic sea ice over time is shown in an animation and a graph plotted simultaneously, but can be parsed so that the change in sea ice area can be shown without the graph.

This video contains a visualization and explanation of the Arctic sea ice and how it has changed over the 25 years. In September 2012, the National Snow and Ice Data Center recorded the lowest extent of Arctic sea ice. The video discusses the climate importance of ice thickness and reflective properties.

This NASA video provides a nice overview of Earth's water cycle from the perspective of looking at Earth from space.

This module contains five activities, in increasing complexity, that focus on understanding how to interpret and manipulate sea level data, using real data from NOAA.

This is a real-time map of current drought conditions in the US, which can be zoomed to the state level, with access to many more resources at that level. Some of these include the National Drought Regional Summaries and animations of historical data.

This NBC Learn video features climate scientists doing their research on Mt. Kilimanjaro to study the climate of the past. The scientists put the recently observed changes on the glacier into perspective by comparing past climate fluctuations, stressing that the current observed rate of change is unprecedented.
Note: you will need to scroll down the Changing Planet video page to get to this video.

This animation shows the Arctic sea ice September (minimum) extents from 1979-2012.

This flow chart shows the sources and activities across the U.S. economy that produce greenhouse gas emissions.

This applet is an ocean acidification grapher that allows user to plot changes in atmospheric C02 against ocean pH, from 1988 to 2009, in the central North Pacific.

This interactive lets students determine the extent of average temperature change both in their community and anywhere else in the world, relative to average temperatures for the three decades between 1951 and 1980.