The Atmosphere and Climate Modeling - Introduction to Carbon Capture and Sequestration - page 71

the climate dice; i.e., they assumed that the deviations of the temperature
have a Gaussian distribution. The width of this distribution represents the
likelihood that at a given place on earth the average temperature during
a period of the year deviates from the average. On the basis of the
1951-1980 statistics one can estimate the fraction of the earth's surface
area that should experience extreme weather at any given time. For
example, for 2006-2011, the climate dice predicts that an average tem-
perature that deviates more than three standard deviations from the
30-year average should affect 0.1-0.4% of the surface of the earth. The
data from 2006-2011 in Figure 2.4.11 show that 4-13% of the planet
had such extreme weather. This is an order of magnitude more than one
could expect from a normal climate dice. Hence, while an individual heat
wave can be ignored as a natural fl uctuation, the total number of anoma-
lies in the climate cannot.

Carbon dioxide

A key question is, of course, whether these observations of global warm-
ing are related to CO 2 levels in the atmosphere. Data on CO 2 levels can
also be obtained from ice core data. Ice cores represent the accumula-
tion of snow for thousands of years (see Figure 2.4.12 ) [2.2]. With each
snowfall, small gas bubbles get trapped in these cores. Analyzing the
composition of the gas in the bubbles as a function of the depth of the
core sample gives us detailed information about the concentration of
various gasses in the air at the time these bubbles were formed. In these
experiments one can also measure the

18 O in shells, which is a proxy for
the average temperature when these shells were formed (see Box 2.4.1 ).
The data in Figure 2.4.13 show that over the last 600,000 years the tem-
peratures and CO 2 levels have fl uctuated within a very narrow range [2.2].
One can clearly see the interglacial warm periods. In these periods CO 2
levels are higher and volumes of ice are smaller. The current greenhouse
gas levels, indicated by stars, are signifi cantly higher than the levels seen
in the last 600,000 years. In Figure 2.4.14 the concentration of green-
house gasses in the atmosphere over the last 2,000 years is shown [2.2].
This fi gure emphasizes the anomaly of the current level of greenhouse
gasses in the atmosphere. Current concentrations of atmospheric CO 2
and CH 4 far exceed pre-industrial values found from polar ice core
records of atmospheric composition dating as far back as 650,000 years.

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