Present climate and biological change - Climate Change: Biological and Human Aspects - page 222

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Fig. 5.5 The1990IPCCBusiness-as-Usual(B-a-U)scenariosimulatingtheanticipatedincreaseinglobalmean

temperaturewithbestestimate(thickline)andupperandlowerestimates(thinlines)showingthe
temperatureriseabovethe1765value.TheIPCCsubsequentlyrevisedthewayitpresenteditsscenariosand
itsforecastsin1992andadheredtotheseforits1995review.ThenearestequivalentstotheIPCC1990B-a-U
scenarioaretheIPCCIS92scenariosaandbandtheyareportrayedapproximatelybythedashedline.Asthese
scenariosarewithintheupperandlowerestimatesofthe1990B-a-Uforecast,andasalltheIPCCforecastsare
decidedbycommittee(hencearebasedonscientists'opinionsratherthanscientiicfact)therewas,atthe
timeofthesecondreport,littleadvantageinconsideringotherforecaststhanthe1990B-a-U.Thetake-home
messageovertheinterveninghalfdecadewasessentiallythesame,beitregardingenergy-policyquestions
raisedorthepossibleenvironmentalimpactstoconsider.InpartafterIPCC(1990).

nations will not be immune to impacts arising from likely climate change. Meanwhile,
those in the less-developed nations have been, and are, less fortunate and vulnerable
to direct impacts from climate change.

5.3 Climateandbusinessasusualinthe21stcentury

5.3.1 TheIPCCBusiness-as-Usualscenario

No one can see into the future, but we can attempt to forecast what might happen given
certain circumstances. One set of circumstances is known as the Business-as-Usual
scenario or B-a-U scenario (Figure 5.5). The next chapter looks at our greenhouse
gas contributions, especially from energy, at the moment and for the rest of the
21st century. For now, while looking specifically at climate, it is worth appraising
the scientific consensus for global warming forecast under the B-a-U scenario. In
the 1980s there was such concern about the possibilities of global warming, as well
as confusion, with doubt that anthropogenic climate change was even likely, that