Global Warming Revisited (a)

Abstract

Is there statistical evidence of global warming? This case presents two sets of real global temperature data, one from the Met Office and another one from NASA, and asks students to assess if the data indeed support the belief that temperatures have been rising over the last 150+ years. The case is open-ended—it provides the data and references to some popular press articles on the subject. Also available is a B case that presents three sets of analysis typical for MBA students—an efficient starting point for class discussion. Excerpt UVA-QA-0808 Jun. 26, 2013 GLOBAL WARMING REVISITED (A) In early 2013, the global warming debate took an interesting turn when new reports noted that for several years, although greenhouse gas emissions had continued to rise, average global temperatures had been stable or had even declined—essentially, according to a NASA official, “flat for a decade.” Some experts referred to this phenomenon as a global warming “plateau” whose duration matched that of the previous warming trend. The significance of such a plateau had already been hotly contested: one scientist dismissed it as too short a period to be significant, while another saw it as an indication that computer models predicting global warming were “deeply flawed.” By mid-2013, it became clear that global temperatures were below even the lowest predictions of those computer models, despite continued increases in atmospheric CO2 concentrations; nobody knew quite why. Meanwhile, other studies continued to buttress arguments that global warming was an epic problem and that temperatures were much higher than they should be. According to the U.S. National Science Foundation, although the range of temperatures had remained relatively stable over the 11,000 years since the last ice age, the cycle of temperature extremes “has happened a lot more quickly” since the Industrial Revolution. The supplementary student spreadsheet (UVA-QA-0808X) presents two sets of average global temperature data: · “Met Office data” from the Climatic Research Unit at the University of East Anglia (United Kingdom). See http://www.cru.uea.ac.uk/ for more information about these data. · “NASA data” from the Goddard Institute for Space Studies (United States). See http://data.giss.nasa.gov/gistemp/ for more information about these data. . . .