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 is a figure from the 2007 IPCC Assessment Report 4 on atmospheric concentrations of carbon dioxide, methane and nitrous oxide over the last 10,000 years (large panels) and since 1750 (inset panels).

This short video from NASA discusses the role that salinity plays in Earth's climate and ocean circulation, focusing on the observations of the Aquarius satellite.

This short video shows an example of melting alpine glaciers in the Austrian Alps (Goldberg Glacier). Disappearing alpine glaciers have social and environmental impacts, including the decline of fresh water supplies and contributing to sea level rise.

This video discusses the social and economic impacts (worldwide and in the US) of sea level rise caused by global warming (aired April 1, 2011).

This visualization graphically displays temperature and CO2 concentration in the atmosphere as derived from ice core data from 400,000 years ago to 1950. The data originates from UNEP GRID Arendal's graphic library of CO2 levels from Vostok ice core.

This animation describes how citizen observations can document the impact of climate change on plants and animals. It introduces the topic of phenology and data collection, the impact of climate change on phenology, and how individuals can become citizen scientists.

Coral Reefs in Hot Water is a short video displaying computerized data collected on the number of reefs impacted by coral bleaching around the world.

This video examines the thawing of permafrost due to changes in climate and shows examples of the impacts that warming temperatures have on permafrost in the Arctic, including the release of the greenhouse gas methane. Dramatic results are shown, including sink holes forming on the landscape and beneath buildings, roads, and other infrastructure, causing some communities to relocate.

This video introduces phytoplankton - the base of the marine food web, the source of half of the oxygen on Earth, and an important remover of CO2 from the atmosphere. The video also explains how satellites are used to monitor phytoplankton and how warming waters and acidification negatively affect phytoplankton.

This audio slideshow examines the changes in the ecosystem that will occur to the Arctic due to increasing temperatures and disappearing sea ice.