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 video describes how field research -- in this case, making water measurements in rugged mountain locations -- helps us to understand the complex relationships among changing climate, populations, and water usage.

This static visualization shows that the global carbon cycle is determined by the interactions of climate, the environment, and Earth's living systems at many levels, from molecular to global.

This video is part of the Climate Science in a Nutshell series. This short, animated video looks at evidence of a rapidly warming planet. It discusses how air bubbles in ice cores can be used to estimate Earth's average air temperature for thousands of years and how direct measurements document air temperatures from 1880.

This animated visualization represents a time history of atmospheric carbon dioxide in parts per million (ppm) from 1979 to 2016, and then back in time to 800,000 years before the present.

This video highlights a team of scientists who work on reconstructing the mass extinction that occurred 250 million years ago, the end of the Permian Period. This event wiped out the majority of life on our planet, resetting the evolution of life. Clues suggest that deadly bacteria might have set off a chemical chain reaction that poisoned the Permian seas and atmosphere.

In this video segment, two students discuss the greenhouse effect and visit with research scientists at Biosphere 2 in Arizona, who research the effects of global climate change on organisms in a controlled facility. Their current research (as of 2002) focuses on the response to increased quantities of CO2 in a number of different model ecosystems.

In this video, the mountain pine beetle problem is explained by two scientists. Their research investigates the beetle and how climate change is hastening its spread.

In this video segment, a team of scientists seeks evidence to support their hypothesis that atmospheric warming may cause water to form beneath the West Antarctic ice sheet. This water causes ice streams to flow much more quickly than the rest of the ice sheet, which has important implications for sea level rise.

This video features University of Wisconsin-Madison researcher John Magnuson, who studies the ecology of freshwater systems. He explains the difference between weather and climate using data on ice cover from Lake Mendota in Madison, WI. Analysis of the data indicates a long-term trend that can be connected to climate change.

In this video, students learn how scientific surveys of wildlife are performed at a site in Yosemite, California. These surveys, in conjunction with studies from the early 1900s, provide evidence that animal populations in Yosemite have shifted over time in response to rising temperatures.