Climate change in the 21st century is the response of the world’s weather patterns to rising (average) global temperatures. The vast majority of scientists agree that the current rate of warming is due to human activities. The 2007 Intergovernmental Panel on Climate Change (IPCC) assessment states that "most of the observed increase in globally averaged temperatures since the mid-20th century is very likely (>90%) due to the observed increase in anthropogenic greenhouse gas concentrations. The lessons in this unit will elaborate on the relationship between human activities and climate change.