This episode was made possible by the generous support of Science Alert.

• 400 ppm official reference – http://dft.ba/-400ppm
• NOAA – http://www.climate.gov” href=”http://www.climate.gov
• UK Met Office – http://metoffice.gov.uk/climate-change
• Climate Central – http://climatecentral.org
• Real Climate – http://realclimate.org
• IPCC FAQs – http://dft.ba/-IPCC
• US Global Change Research Program – http://globalchange.gov