The Atmosphere and Climate Modeling - Introduction to Carbon Capture and Sequestration - page 83

Pinatubo

Agung

Santa Maria

El Chichon

Figure 2.5.5 Temperature predictions of different climate models
Comparison between global mean surface temperature anomalies (°C) from observations
and climate model simulations. The black line represents experimental data. The thin yel-
low lines are the results of 58 simulations produced by 14 models with both anthropogenic
and natural forcings. The red line is the average of these 58 simulations. The thin vertical
lines indicate major volcanic events. Figure from IPCC, reproduced with permission [2.2].

As a result, their predictions are slightly different. These differences are a
very useful measure of the intrinsic uncertainties in the computer modeling
of climate. Figure 2.5.5 shows that the average of all models gives a sur-
prisingly accurate prediction of the long-term increase of the average
temperature as well as the drops in temperatures induced by the volcanic
eruptions [2.2]. That these models give such an accurate prediction of the
climate over a period of 100 years is impressive, and adds confi dence to
predictions based upon these models.
One of the most powerful applications of these climate models is
comparison of “parallel earths.” For example, we can rerun all the climate
models that are used to generate Figure 2.5.5 , but now with an earth in
which no fossil fuels are used. The models depicted in Figure 2.5.5
include the increase in CO 2 levels due to burning of fossil fuels. Figure
2.5.6 shows the same predictions, but now in a world in which there are
no anthropogenic emissions of greenhouse gasses [2.2] . These calcula-
tions show that, indeed, the recent temperature increase can only be
explained if we include anthropogenic emissions. These calculations
demonstrate that large scale CO 2 emissions infl uence the climate.