Welcome to the Anthropocene?
Stratigraphers are geologists, who focus on sediment, rock or ice layers, etc. These 'strata' form by deposition of organic or inorganic material (such as microorganisms or volcanic ash) and provide a records of the history of our planet's surface. Because gas bubbles, isotopes, etc. are captured in the strata, scientists can analyse the geochemistry of the past, date certain events, and more. That kind of data ultimately underlies xkcd's recent 'Earth Temperature Timeline'. Direct measurements of geochemical signals such as atmospheric CO2 concentration and ocean pH started only in the mid-20th century. Besides the Intergovernmental Panel on Climate Change, the AWG is possibly the most diverse scientific committee with most public attention currently. Therefore, defining the Anthropocene is a multi-disciplinary, collaborative scientific effort, as well as an inherently political statement. This talk will explain why.