This interactive visualization from the NASA Earth Observatory website compares Arctic sea ice minimum extent from 1984 to that of 2012.

This video provides a good introduction to the field of attribution science. Beginning with an introduction to weather and climate, it describes how severe weather might be linked to climate change and the science behind attribution studies. It gives a good explanation behind how scientists use climate models to study whether severe weather events were influenced by climate change. It also discusses the question, "does climate change cause extreme weather?" and provides an introduction to the concepts of probability, causation, and correlation in regards to attribution science (how much climate change influenced an event verses normal variations in weather).