Increased global temperatures are “unequivocal,” human influence is 95-100% likely to be dominant driver of those changes, and the best-case scenario implies fundamental changes to political institutions and energy production. Welcome to Climate Change 2013 – the Physical Science Basis Summary for Policymakers.
Climate Science for Everyone: How scientists measure the carbon dioxide in 800,000 year old air
Scientists can directly measure air that has been sealed in an icy time capsule for 800,000 years. Climate Science for Everyone describes how this works.