When we speak of the impacts of global warming, we are really talking about climate change and its impacts. Climate—that is, long-term weather patterns—is changing in response to the warming in a wide variety of interrelated ways, with diff ering consequences for diff erent places on Earth.
Th e oceans are taking the brunt of the consequences. Oceans absorb 90 percent of the excess heat energy trapped by the greenhouse eff ect, 41 which, in turn, causes warming of the deep ocean interior and disruption of deep ocean currents. Oceans also absorb nearly half of the carbon dioxide that we place in the atmosphere, 42 which makes the ocean more acidic. Together these two phenomena are changing the global oceanic ecosystem.
Coral and shellfi sh are declining precipitously because they have diffi culties forming shells and skeletons in a warmer and more acidic ocean. 43 Trichodesmium, a type of cyanobacteria, is currently rapidly overpopulating in response to the changing ocean conditions. In laboratory studies, rapid overpopulation of Trichodesmium is followed by a sudden catastrophic die-off when nutrients become overused and thus scarce. 44 If Trichodesmium in the ocean undergoes a similar die-off , it would severely disrupt
40 Pacifi c Northwest National Laboratory, “Earth’s Climate Is Starting to Change Faster, New Research
Shows,” ScienceDaily (2015). Online: http://www.sciencedaily.com/releases/2015/03/150309134642.
htm (accessed March 25, 2015); Steven Smith et al., “ Near-term Acceleration in the Rate of Temperature Change ,” Nature Climate Change 5 ( 2015 ): 333–6 .
41 NOAA, “Climate Change: Ocean Heat Content” (2014). Online: https://www.climate.gov/news
-features/understanding-climate/climate-change-ocean-heat-content (accessed December 31, 2015); N.L. Bindoff et al., “ Observations: Oceanic Climate Change and Sea Level ,” in Climate Change 2007: Th e Physical Science Basis , (eds.) S. Solomon et al . ( Cambridge and New York : Cambridge University Press , 2007 ).
42 NOAA, “NOAA, Partners: Earth’s Oceans and Ecosystems Still Absorbing about Half the Greenhouse
Gases Emitted by People” (2012). Online: http://www.noaanews.noaa.gov/stories2012/20120801 Hawaii at Manoa, “Rapidly Acidifying Waters Pose Major Th reat for Southern Ocean Ecosystem”;
Hauri et al., “Abrupt Onset and Prolongation of Aragonite Undersaturation Events in the Southern Ocean,” 172–6.
44 University of Southern California, “Climate Change Will Irreversibly Force Key Ocean
Bacteria into Overdrive,” ScienceDaily (2015). Online: http://www.sciencedaily.com /releases/2015/09/150901140204.htm (accessed December 3, 2015); David Hutchins et al.,
“ Irreversibly Increased Nitrogen Fixation in Trichodesmium Experimentally Adapted to Elevated Carbon Dioxide ,” Nature Communications 6 ( 2015 ): 8155 .
the global oceanic food chain: Trichodesmium is one of the few key species that fi x nitrogen and thus form a substantial part of the base of the oceanic food chain. 45
Meanwhile, the sea level is indeed rising. Th e United Nations Intergovernmental Panel on Climate Change (IPCC) is predicting a rise of between 0.26 and 0.82 meters (0.8 and 2.7 feet) by the end of this century. 46 Recent research fi ndings—far too new to have made their way into the intergovernmental reports—predict a much larger sea level rise, perhaps as much as 5 meters (15 feet) in a similar time period. 47 Th is much higher prediction comes from a detailed computer simulation that brings together a wide range of considerations including paleoclimatic data, the eff ects of changes in ocean salinity, the eff ects of meltwater injection on deep ocean energetics and currents, and new understandings of ice melt rates. 48
Th e average sea level has already risen about 20 centimeters (9 inches) since 1880.
Th is is enough to cause immediate impacts 49 such as salt water intrusion into freshwater aquifers and coastal destruction from higher storm surges. Th ese eff ects are being felt along coastlines in the United States 50 and, especially, on highly vulnerable islands such as Kiribati 51 and the Solomon Islands. 52
Th e role of climate change in driving extreme weather events—superstorms, fl oods, droughts, extreme heat waves, and extreme cold—is frequently misunderstood.
Climate change is never the sole cause of such events; however, it creates conditions that make weather events become more frequently extreme. Th e underlying physical causes of this relationship are easy to understand in principle, even if making detailed models of those relationships is diffi cult.
With global warming, the number of storms experienced per year is not likely to change; in fact, it may even get slightly smaller. However, the strength of hurricanes and typhoons will change noticeably. Warmer sea surface temperatures and warmer air provide more energy for storms. Increased moisture in the atmosphere provides more
48 J. Hansen et al., “ Ice Melt, Sea Level Rise and Superstorms ,” Atmospheric Chemistry and Physics
Discussions 15 ( 2015 ): 20059–179 .
49 IPCC , “ Climate Change 2014: Impacts, Adaptation, and Vulnerability. Part A: Global and Sectoral
Aspects ,” in Contribution of Working Group II to the Fift h Assessment Report of the Intergovernmental Panel on Climate Change , (eds.) C. Field et al. ( Cambridge and New York : Cambridge University Press , 2014 ).
50 National Center for Atmospheric Research, “Evaluating the Eff ects of Future Sea Level Rise and
Storm Surges along US Coastlines.” Online: https://ncar.ucar.edu/press/evaluating-the-eff ects-of -future-sea-level-rise-and-storm-surges-along-us-coastlines (accessed January 1, 2016); C. Tebaldi , B. Strauss , and C. Zervas , “ Modelling Sea Level Rise Impacts on Storm Surges along US Coasts ,”
45 Richard Feely, Christopher Sabine, and Victoria Fabry, “Carbon Dioxide and Our Ocean Legacy,”
NOAA Pacifi c Marine Environmental Laboratory (2006). Online: http://www.pmel.noaa.gov/pubs /PDF/feel2899/feel2899.pdf (accessed July 1, 2014).
Prologue 19
water for storms to drop as torrential rainfall. 53 Th ese factors, coupled with an observed correlation between warming ocean temperatures and an increase in damaging hurricanes, 54 lead to a growing consensus that as the climate warms, large storms will get bigger and more destructive. Th us, we can expect to see large superstorms more frequently, not because there will be more storms, but because larger storms will grow much larger. 55
Over land, storms are expected to become more concentrated and to drop larger amounts of rain. 56 In general, wet regions will get wetter and experience catastrophic (100-year or greater) fl ooding. 57 Dry regions, on the other hand, will get drier and thus become susceptible to extreme droughts. Lightning strikes will become more frequent, which, coupled with conditions caused by drought, will lead to more incidences of uncontrollable wildfi res. 58
Th e consequences for human health and well-being are many. Th e US Centers for Disease Control and Prevention are predicting the spread of diseases, both common ones like asthma and cardiovascular diseases and rare ones like infectious tropical and water-borne diseases. Th ey predict growing incidences of illnesses and deaths from extreme heat, malnutrition, and water shortages. And, with living conditions deteriorating in many localities, they predict increased incidences of forced migrations and civil confl icts. 59 By 2050, the number of climate migrants may reach 200 million people, with the majority being children and the poor. 60
Th e quest to trace specifi c extreme weather events to human-caused climate change is hampered by the complexities of the climate system and by the need to carry out modeling at very small resolutions in order to show direct causality.
Current work is aimed at improving the resolution scale (from several hundred square kilometers to 60 square kilometers) and speeding up the computational time needed to make such calculations (from years to weeks or days). Th is is now allowing specifi c attribution of some broad-scale events, such as heat waves or cold spells, to climate change, but it is still insuffi cient to make attributions of small-scale
53 Adam Volland, “In a Warming World, Storms May Be Fewer but Stronger,” NASA Earth Observatory /releases/2015/01/150129143040.htm (accessed January 1, 2016 ) .
56 Seung-Ki Min , Xuebin Zhang , Francis Zwiers , and Gabriele Hegerl , “ Human Contribution to
More-intense Precipitation Extremes ,” Nature 470 . 7334 ( 2011 ): 378–81 .
57 Yukiko Hirabayashi et al., “ Global Flood Risk under Climate Change ,” Nature Climate Change 3
( 2013 ): 816–21 .
58 O. Pechony and D. Shindell , “ Driving Forces of Global Wildfi res over the Past Millennium and
the Forthcoming Century ,” Proceedings of the National Academy of Sciences of the United States of America 107 ( 2010 ): 19167–70 ; R. Seager et al., “ Model Projections of an Imminent Transition to a More Arid Climate in Southwestern North America ,” Science 316 ( 2007 ): 1181–4 .
59 Centers for Disease Control and Prevention, “Climate Eff ects on Health.” Online: http://www.cdc
.gov/climateandhealth/eff ects/ (accessed January 2, 2016).
60 Princeton University, “As Global Temperatures Rise, Children Must Be Central
Climate Change Debates,” ScienceDaily (2016). Online: https://www.sciencedaily.com /releases/2016/05/160504121330.htm (accessed May 5, 2016).
phenomena such as hurricanes or localized rainfall events. 61 It is important to note, however, that the current inability to directly attribute extreme weather events to human-caused climate change is not evidence that no such links exist. Rather, it is merely evidence that our ability to trace through the fi ne-scale details involved is still nascent.
Pope Francis, writing in his papal encyclical Laudato Si’ , aptly sums up the situation:
A very solid scientifi c consensus indicates that we are presently witnessing a disturbing warming of the climatic system. In recent decades, this warming has been accompanied by a constant rise in the sea level and, it would appear, by an increase of extreme weather events, even if a scientifi cally determinable cause cannot be assigned to each particular phenomenon. Humanity is called to recognize the need for changes of lifestyle, production and consumption, in order to combat this warming or at least the human causes which produce or aggravate it. 62
Solutions
Pope Francis says very clearly that we must convert to renewable sources of energy and develop better capacities for storing energy. 63 However, he leaves open the question of how far we should go in this regard and how fast we should do it. Th is omission is appropriate because debates over the levels to which we should allow the warming to proceed or the pace at which we should reduce greenhouse gas emissions 64 distract attention from the key point: it will take a very long time for carbon dioxide in our atmosphere to return to preindustrial levels. Most of the excess carbon dioxide will remain for at least hundreds or thousands of years, and some will remain for tens of thousands or even hundreds of thousands of years. 65 Th e only reasonable solution, therefore, is to stop all carbon emissions and stop them now : keep all of the remaining carbon in the ground.
Th e cost of delay is profound. With every ten years of delay in reducing greenhouse gas emissions, the peak warming temperature will increase by about 0.5 degrees Celsius. In other words, the actions taken today to limit global warming to 2 degrees
62 Pope Francis , Laudato Si’: On Care for Our Common Home ( Th e Holy See : Vatican Press , 2015 ), §23 .
63 Ibid., §26.
64 UN Conference on Climate Change (COP21). Online: http://www.cop21.gouv.fr/en/more-details
-about-the-agreement/ (accessed December 30, 2015).
65 David Archer et al., “ Atmospheric Lifetime of Fossil Fuel Carbon Dioxide ,” Annual Review of Earth
and Planetary Sciences 37 ( 2009 ): 117–34 .
61 Warren Cornwall , “ Eff orts to Link Climate Change to Severe Weather Gain Ground ,” Science 351 . 6279
( 2016 ): 1249–50 ; National Academies of Sciences, Engineering, and Medicine , Attribution of Extreme Weather Events in the Context of Climate Change ( Washington, DC : Th e National Academies Press , 2016 ) ; NOAA, “Human-caused Climate Change Increased the Severity of Many Extreme Events in 2014,” ScienceDaily (2015). Online: http://www.sciencedaily.com/releases/2015/11/151107202528 .htm (accessed December 30, 2015); S. Herring et al. (eds.), “ Explaining Extreme Events of 2014 from a Climate Perspective ,” Special Supplement to the Bulletin of the American Meteorological Society , 96 . 12 ( 2015 ).
Prologue 21
Celsius, would, if taken ten years hence, limit the warming to only 2.5 degrees Celsius.
Th e extra “push” we give to global warming during the years of delay makes it that much harder to ultimately stop the warming. 66
Is it possible to change our energy production entirely to renewable sources? Th e US Department of Energy’s National Renewable Energy Laboratory (NREL) thinks so: “Renewable electricity generation from technologies that are commercially available today, in combination with a more fl exible electric system, is more than adequate to supply 80 percent of total US electricity generation in 2050.” 67 In making this assessment, the NREL assumed a future in which half of the energy needs would be supplied by solar and wind power, with the rest coming from a combination of biomass, geothermal, and hydropower. Th ese sources would have to be supported by much greater attention to energy effi ciency, development of a more fl exible and effi cient energy transmission system, and development of better energy storage capacity. Th ey did not take into account the very real probability that vast technological improvements in these and other renewable energy generation methods will occur in the next few decades. As such technologies develop, the prospects for converting completely to renewable energy grow ever higher, particularly since the costs for renewable energy are declining precipitously and the rates of new installations are increasing rapidly. 68
Th e problem, then, is not one of technology; it is a problem of changing human-devised systems. We have become reliant upon a vast infrastructure for delivering energy from fossil fuels: an interlocking electrical grid, a plethora of gasoline stations, and a vast network of oil and natural gas pipelines. In order to replace fossil fuels with renewable sources of energy, we have to rebuild our systems of energy delivery. In particular, the electric grid has to be made able to accept input of electricity from a widely distributed array of solar, wind, and hydroelectric sources, and it has to be able to compensate for times when the Sun is not shining and the wind is not blowing. Ways to store massive amounts of electrical energy for use at later times then become essential. It is also a problem of adapting the human-made economic, regulatory, and social systems that have been built upon the premise of readily available energy from fossil fuels.
Th e essential question, therefore, is: Do we have the societal will necessary to make the economic, social, regulatory, and energy infrastructure changes needed to convert to renewable energy? Bill McKibben, writing in the New Republic , asserts that the climate crisis is akin to a World War and that a wartime reindustrialization is necessary in order to win the war against climate change. 69 Although this sounds like hyperbole, it
66 University of Bern, “Timely Action Needed to Meet Climate Targets,” ScienceDaily (2016).
68 US Department of Energy, Revolution Now—2016 Updates. Online: http://energy.gov/eere
/downloads/revolutionnow-2016-update (accessed October 5, 2016).
69 Bill McKibben, “A World at War,” New Republic (2016). Online: https://newrepublic.com
/article/135684/declare-war-climate-change-mobilize-wwii (accessed August 17, 2016).
is unfortunately true. A massive restructuring of lifestyles and an intense national (and international) focus is indeed necessary to ward off the worst eff ects of climate change.
With the tremendous leverage provided by Laudato Si’ , the landmark agreements reached at the 2015 United Nations Conference on Climate Change, 70 and the growing interest in sustainable lifestyles, we are beginning to move in the right direction.
However, a much more rapid and serious eff ort is necessary if we are to win this war.