clear, and recent anthropogenic emissions of greenhouse gases are the highest in history.”42 Carbon dioxide is acting on the climate like a “performance enhancing drug.”43 According to a leading source of climate news, “[a]ll that extra energy in the atmosphere increases the probability and intensity of extreme weather events, making droughts, storms and wildfires…far more likely and far more destructive.”44 The impacts of climate change can also be gradual and/or have a slow-onset. The atmospheric concentrations of carbon dioxide, methane, and nitrous oxide have increased to levels unprecedented in at least the last 800,000 years. Carbon dioxide concentrations in the atmosphere have increased by 40% since pre-industrial times.45 The observed warming in the climate system is unequivocal and so far the global mean of earth atmospheric near surface temperature has warmed by roughly 0.8 degrees during the period 1880-2012.46 Figure 1: Natural Greenhouse Effect v. Human Enhanced Greenhouse Effect47 Source: Will Elder, National Park Service                                                                                                                         42 IPCC, 2014: Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, R.K. Pachauri and L.A. Meyer (eds.)]. IPCC, Geneva, Switzerland, 151 pp., Summary for Policymakers at 2. Available at https://www.ipcc.ch/pdf/assessment-report/ar5/syr/AR5_SYR_FINAL_SPM.pdf (last accessed June 15, 2015). 43 Polar Bears International, Climate Change, http://www.polarbearsinternational.org/about-polar-bears/climatechange (last accessed on September 15, 2015). 44 Stephen Lacey, Climate Progress, Media Connecting The Dots On U.S. Storms, Heat And Wildfires: ‘This Is What Global Warming Looks Like’, July 3, 2012, http://thinkprogress.org/climate/2012/07/03/510481/media-connectingthe-dots-on-us-storms-heat-and-wildfires-this-is-what-global-warming-looks-like/ (last accessed Sept. 15, 2015). 45 Ciais, P., C. Sabine, G. Bala, L. Bopp, V. Brovkin, J. Canadell, A. Chhabra, R. DeFries, J. Galloway, M. Heimann, C. Jones, C. Le Quéré, R.B. Myneni, S. Piao and P. Thornton, 2013: Carbon and Other Biogeochemical Cycles. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA at 467. 46 IPCC, 2013: Summary for Policymakers. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA at 4-5. 47 U.S. National Park Service, What is Climate Change, http://www.nps.gov/grba/learn/nature/what-is-climatechange.htm (last accessed September 15, 2015).             14