e. Based on evidence from tree rings, other natural records, and scientific observations made around the world, Earth's average temperature is now warmer than it has been for at least the past 1,300 years. Average temperatures have increased markedly in the past 50 years, especially in the North Polar Region.

This activity is a research project in which students explore and synthesize key paleoceanographic evidence for the Paleocene-Eocene Thermal Maximum (PETM) as found in marine sediment cores collected and analyzed during Ocean Drilling Program Leg 208 (Walvis Ridge).

This video provides an overview of changes happening in the Arctic.

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

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 video considers the current estimates of sea level rise as possibly too conservative and discusses more recent data on ice melt rates coming from Antarctica and Greenland, showing rates of melt at up to 5 times as rapid. Scientists discuss what levels and rates of sea level rise have occurred in the past, including the Pliocene, which demonstrated 1m rise every 20 years.

This video features research conducted at University of Colorado's Institute of Arctic and Alpine Research, which studies isotopes of hydrogen trapped in ice cores to understand climate changes in the past.

In this activity, students compare carbon dioxide data from Mauna Loa Observatory, Barrow, Alaska, and the South Pole over the past 40 years. Students use the data to learn about what causes short-term and long-term changes in atmospheric carbon dioxide. This activity makes extensive use of Excel.

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.