Lecture 1 Humankind and Climate August 20, 2015 Earth from a million miles away NASA Deep Space Climate Observatory, July 6, 2015. The atmosphere is a thin layer of gas, about 100 km thick Weather and climate happen in the lowermost 12 km of the atmosphere 100 km 12 km 12.756 km Humans are leaving a global footprint http://visibleearth.nasa.gov/ World energy and CO emissions 2 US (2014): 2.3 billion 6 billion: Source: British Petroleum Statistical Review of World Energy 2015 1 billion metric tons oil equivalent = 12 billion MWh (energy) fossil fuel only Global warming / climate change Many opinions have been expressed … from the doom-laden … to the dismissive The scientific consensus* “Observations throughout the world make it clear that climate change is occurring, and rigorous scientific research demonstrates that the greenhouse gases emitted by human activities are the primary driver.” Statement on climate change from 18 scientific organizations, 2009: http://www.aaas.org/sites/default/files/migrate/uploads/1021climate_letter1.pdf *Consensus: 97% of climate scientists a