Geoscience Reference
In-Depth Information
In estimating impacts, people often confuse weather and climate. A
persuasive body of evidence shows that especially hot weather reduces
farm yields in the United States. But studies show that a small climatic
warming would probably increase farm yields in the United States. The
difference is that farmers can adapt to the warmer climate by changing
their management practices, but they cannot easily adapt to a severe
and unexpected summer drought after all their planting decisions are
made. So stories about “weather disasters” tell us nothing about the im-
pacts of climate change. Of course, weather disasters like fl oods, hurri-
canes, and droughts bring adverse effects. But we need to know whether
there will be more of these weather disasters in a warmer world and
whether people can prepare for them.
The lesson here is that our analysis needs to be alert to examining
climatic impacts, including the adaptations that take place, while sep-
arating these from the background variability of day-to-day weather
events.
AN OVERVIEW OF IMPACTS ANALYSIS
When we consider the question of impacts, we are generally not
concerned about climate change itself. The average surface temperature
of the earth is by itself no more worrisome than the surface tempera-
ture of Jupiter. Rather, we are concerned about the effects of climate
change on physical and biological systems and on human societies. This
central point implies that sensible policies will depend upon our assess-
ment of the ways, some obvious and some subtle, that climate changes
affect the different human and natural systems.
A related important point concerns costs. Economists and engineers
who have studied ways to slow climate change or reduce its damaging
effects conclude that steps to slow global warming will impose costs.
Put differently, if we want to reduce our CO 2 emissions so as to reduce
impacts, it will require using costlier technologies and policies and
therefore will reduce real incomes. For example, we might lower CO 2
emissions by improving automobile fuel economy. Current automotive
technology can indeed improve fuel effi ciency, but it will raise the cost
of the car. A hybrid gas-electric car might reduce CO 2 emissions by 20
 
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