Future prospects - Ice Ages and Interglacials: Measurements, Interpretation, and Models - page 338

also found a good correlation between global temperature and an ENSO
index for 2006-2008. Hence, it seems clear that global temperature changes for
2006-2008 were driven primarily by changes in the oceans, and changes in humid-
ity during that period were not a cause of global temperature change—but an
effect. The effect of changing CO 2 concentration and a putative water vapor green-
house effect are buried in the noise of a much stronger signal due to El Nin ˜ o
variability during these years. Therefore, it is physically impossible to derive water
feedback sensitivity from data limited to these two winters. Yet, the authors claim
that they have done so and quote a value in agreement with climate models.
This seems impossible to this writer. They then reach the rather incredible
conclusion:

''The existence of a strong and positive water-vapor feedback means that
projected business-as-usual greenhouse gas emissions over the next century are
virtually guaranteed to produce warming of several degrees Celsius.''

This conclusion is utterly unsupportable from the analysis of two winters' data
controlled by El Nin˜ o activity.
Dessler et al. (2008a) analyzed one month's data in 2005 to infer clear sky
top-of-atmosphere outgoing long-wavelength radiation (OLR) and its relationship
to humidity. As to whether this paper sheds any light on water feedback sensitivity
is not clear to this writer.
Gettleman and Fu (2008) analyzed the changes in humidity produced by
temperature changes from 2002 to 2007. As before, temperatures during this
period appear to have been determined by El Nin˜ o variability, and changes in
water vapor content appear to be effects of this temperature change. There is little
or no connection to heating produced by CO 2 and water feedback sensitivity does
not seem to be derivable from this work.
It is now becoming apparent that the high temperatures experienced by the
Earth in the late 1990s, and particularly in 1998, were related to the prevalence of
El Nin˜ o conditions and, with the advent of the La Nin˜ a in 2007-2008, world
temperatures dropped. Temperatures rose again with the El Nin˜ o of 2009, and
then faded with the La Nin˜ a of 2010. While it is possible that growth in CO 2
contributed to global warming during the 20th century, it is clear that large
fluctuations dictated by ocean conditions, aerosol emissions, and unknown factors
have masked the putative CO 2 effect, making it very dicult to unravel the con-
tribution of rising CO 2 . As Kondratyev et al. (2003) concluded: ''The principal
conclusion to be drawn

is that studies of such a complicated problem as global
carbon dynamics are still at an early stage of development

...

.''
Perhaps the most amazing thing about the debate on global warming and
greenhouse gases is that both sides (alarmists and naysayers) are so self-righteous
and certain they are right while the systems are so complex and poorly
understood.

...