FUTURE CLIMATE CHANGE - The Climate Casino - page 46

1.0

Hadley Center
National Climatic Data Center
GISS

0.8

0.6

0.4

0.2

0.0

-0.2

-0.4

1860 1880 1900 1920 1940 1960 1980 2000 2020

Figure 8. Global temperature trend as constructed by three research groups, 1850- 2012.

The second approach applies integrated assessment models (IAMs),
the economic models discussed in Chapter 3. These models combine
population, technology, energy sectors, and economic growth as well as
carbon cycles and climate models. They construct what might be called
a combined best estimate of climate change over the coming years. For
this calculation, I use the average of CO 2 concentrations from the differ-
ent EMF-22 models shown in Figure 5. 11 For comparison, I also show
the temperature projections from climate models reviewed by the IPCC
using the stylized emissions scenarios.
Figure 9 shows the results of these estimates. 12 The two heavy lines
in the middle indicate the average of the EMF-22 models (dashed line)
and the results from the RICE model (heavy solid line). This picture
provides a good overview of different future climate-change possibili-
ties predicted by multiple modeling groups around the world.
Let's focus on the IAMs. Although the models have different as-
sumptions about economic growth, population, the energy sector, new
technologies, and the carbon cycle, they generate very similar tempera-