Future prospects - Ice Ages and Interglacials: Measurements, Interpretation, and Models - page 324

big one is coming'' know full well that continued funding requires an atmosphere
of fear.
Benestad (2005) discussed the tension between those who study the variability
of the Sun as a source of climate change vs. those who are dedicated to CO 2 as
the major driver of climate change. Benestad (2005) said:

''I must admit that I have encountered entrenched positions on the subject
and some prejudice, as the issue of whether solar activity may affect terrestrial
temperatures appears to be laden with political and personal agendas .

Various hypotheses of solar regulation of our climate have sometimes been
presented as a scientific challenge to the established view that human emissions
of greenhouse gases represent a disrupting influence on our climate. Scientifically
speaking, such a challenge would be sound and the best thing that could happen
for further progress.''

...

However, he did not feel safe leaving it at that but felt compelled to pay lip
service to the consensus by saying it would be ''unfortunate'' if the claim that
anthropogenic climate disruption can result in severe climate change proves to be
real, and this challenge delayed response to this threat. He also knelt before the
king by assuring that ''solar influence on Earth's climate

... does not represent an

antithesis to the so-called enhanced greenhouse effect.''

11.1.3 Effect of CO 2 growth on global temperature
The question of interest here is whether projected CO 2 emissions in the 21st
century will produce enough global warming to prevent or seriously delay future
ice ages. Thus, we are concerned with the putative connection between CO 2 and
global warming.
As Figure 4.16 shows, the CO 2 concentration in the Earth's atmosphere in
the past has tended to vary between about 190 ppm during glacial maxima to
about 280 ppm during interglacial periods. Because changes in the CO 2 con-
centration lag changes in global average temperature by perhaps 1,000 years, it
seems likely that such changes are primarily the effects rather than the causes of
ice ages. Nevertheless, such changes in the CO 2 concentration undoubtedly
provide additional positive feedback to contribute to trends in climate change
during glacial-interglacial cycles. Furthermore, there is evidence that previous
interglacials reached higher temperatures than those of today; yet their CO 2
concentrations remained under 300 ppm. This seems very strange. The CO 2 con-
centration in the Earth's atmosphere has increased rapidly in the 20th and 21st
centuries, well beyond the expected range for glacial-interglacial cycles (see Figure
11.1 ). During the time the CO 2 concentration has increased, the Earth has also
undergone warming. Many climatologists believe that the rising CO 2 concentra-
tion has been the primary cause of this global warming. Figure 11.2 shows the
alarmist view of rising global temperatures in the 20th century compared with
rising CO 2 concentrations. However, there are diculties with this interpretation.