Seite - 168 - in Water, Energy, and Environment - A Primer

This conclusionwasquestionedbysomeformanyyears (though not by the vastmajority of the scientific community) but now is widely acceptedby scientists andpolicymakers alike.Today Jim Hansen serves as director of the Program on Climate Science, Awareness and Solutions of the Earth Institute at Columbia University.Hiswork, and that of his scientific predecessors, has laid a solid foundation for understanding the physical basis of globalwarming.Understanding theglobal energyexchangesand the weather changes associated with this warming may be the most important scientific activitycurrentlyunderway. 10.1.2 Is theredocumentedevidence forglobal warmingandclimatechange? Globalwarmingisnotatheoreticalconcept.Concernaboutglobal warmingandassociatedclimatechangeisbasedonphysical,well documented measurements. Perhaps the most attention-getting are the impacts on water: melting of glaciers, rising sea levels, changes in rainfall patterns, and water and wind damage from more powerful storms. These effects are real, well documented, and increasinglywellmodeled. Accurate measurements of atmospheric CO2 were begun by Dave Keeling at Caltech in the early 1950s and moved to MaunaLoa inHawaii in 1958.Thesemeasurements continue to this day, and similar measurements are nowmade routinely at many sites around theworld. Based on these measurements, deep geological core measurements, and related scientific analysis, it is understood that CO2 concentrations have varied widely over the past 400,000 years, from about 180ppmduring periods of extensive glacier formation to 280ppm during the interglacial periods (seeFigure 10.1). With the advent of the industrial revolution in the 1800s, and the increasing use of fossil fuels, atmospheric CO2 concentrations have grown steadily (64), and as of 2018 have Water,Energy, andEnvironment–APrimer168