2012 Visitor Guide: 50th Anniversary Edition (2,021 KB PDF)
2007 Visitor Guide (4,000 KB PDF)
Did You Know?
Climate scientists warn that the safe upper limit for atmospheric carbon dioxide (CO2) concentrations is 350 parts per million (ppm). For most of human history, atmospheric CO2 rarely exceeded 275 ppm--until the industrial revolution. As of 2014, atmospheric CO2 was ~400 ppm–-and rising 2 ppm/year. More...