Environmental Problems, Their Causes, and Sustainability 1

CellCloudsLandOceanAccording to the IPCC, it is very likely that this willbe the fastest temperature change of the past 1,000years. Such rapid temperature change can affect theavailability of water resources by altering rates ofevaporation and precipitation. It can also change windpatterns and weather, dry some areas, add moisture toothers, alter some ocean currents, shift areas wherecrops can be grown, increase average sea levels andflood some coastal wetlands and cities and low-lyingislands, and alter the structure and location of some ofthe world’s biomes. These are major changes in theearth’s atmospheric conditions. An increase in theearth’s average temperature within a few decades or acentury gives us little time to deal with its effects.In 2002, the U.S. National Academy of Sciences issueda study, which raised the possibility that the temperatureof the troposphere could rise drastically inonly a decade or two. The report cited abrupt andlong-lasting changes in tropospheric temperatures thathave occurred during the last 100,000 years.The report lays out a nightmarish worst-case scenarioin which ecosystems suddenly collapse, lowlyingcities are flooded, forests are consumed in vastfires, grasslands die out and turn into dust bowls,wildlife disappears, and tropical waterborne and insect-transmittedinfectious diseases spread rapidly beyondtheir current ranges.Figure 21-10 Global circulation model (GCM) of climate dividesthe earth’s atmosphere into large numbers of giganticboxes or cells stacked many layers high. The laws of physicsand our understanding of global air circulation patterns andother factors that can affect climate are used to describe numericallywhat happens to major variables affecting climate ineach cell and how they change from one cell to another.nuity to offset most of the undesirable effects of climatechange.xHOW WOULD YOU VOTE? Do you believe that we will experiencesignificant global warming during this century? Castyour vote online at http://biology.brookscole.com/miller14.Why Should We Be Concerned about aWarmer Earth? The Speed of ChangeIs What CountsA rapid increase in the temperature of the tropospherewould give humans and other species littletime to deal with its effects.Climate scientists warn that the concern is not just atemperature change but how rapidly it occurs, regardlessof cause. Past temperature changes often tookplace over thousands to a hundred thousand years(Figure 21-2, top left). The problem we face is a fairlysharp projected increase in the temperature of the troposphereduring this century (Figure 21-11).Change in temperature (°C)6.05.55.04.54.03.53.02.52.01.51.00.501850 1875 1900 1925 1950 1975 2000 2025 2050 2075 2100YearFigure 21-11 Comparison of measured changes in theaverage temperature of the atmosphere at the earth’s surfacebetween 1860 and 2003 and the projected range of temperatureincrease during the rest of this century. (Data fromU.S. National Academy of Sciences, National Center forAtmospheric Research, and Intergovernmental Panel onClimate Change)http://biology.brookscole.com/miller14471