Climate change in the 21st century is the response of the world’s weather patterns to rising global temperatures. The 2007 Intergovernmental Panel on Climate Change (IPCC) report stated 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. In their updated 2013 assessment , the IPCC stated "Warming of the climate system is unequivocal". This lesson explores connections between human activities and global climate change.