Geoscience Reference
In-Depth Information
Table 1.
Projections of uncontrolled CO
2
emissions for the United States and
the world, 2010-2050.
Growth rate
(% per year)
2010
2050
United States
GDP/Pop (2005 $/person)
42,300
83,700
1.7
CO
2
/GDP (tons/$1,000,000)
432
226
−
1.6
Population (millions)
309
399
0.6
Total CO
2
Emissions (million tons CO
2
)
5,640
7,550
0.7
Global
GDP/Pop (2005 $/person)
9,780
22,400
2.1
CO
2
/GDP (tons/$1,000,000)
522
278
−
1.6
Population (millions)
6,410
9,170
0.9
Total CO
2
Emissions (million tons CO
2
) 4, 00 , 00
.3
have elaborate energy-sector models to project the availability and use
of different fuels. The output projections might take into account the
capital in structures and equipment, software, technological change, and
other factors. But the essential idea can be captured by this example.
The bottom half of Table 1 shows projections for the world (including
CO
2
released by land-use changes as well as industrial emissions). If there
are no policies to curb emissions, the global total of CO
2
emissions is pro-
jected to rise about 1.3 percent per year to midcentury. The difference
between the top and bottom projections is primarily due to expectations
that developing countries will grow more rapidly than the United States.
Table 1 suggests that there are three ways to reduce emissions: lower
population growth, lower growth in living standards, and lower CO
2
intensity (decarbonization). People sometimes think that the CO
2
growth
rates shown in Table 1 are ironclad laws that are unresponsive to eco-
nomic policy, or, perhaps even more pessimistically, that we can only
bend down the emissions trajectory by severely limiting growth in living
standards or imposing draconian limits on population.
Such pessimistic conclusions are an incorrect reading of both his-
tory and policy. Societies can bend down the CO
2
growth curve by
