Source:
MIT emeritus Alfred P. Sloan
professor of meteorology
Richard S. Lindzen, PhD,
has published over 200 scientific articles and books over a five-decade career.
He has held professorships at the University of Chicago, Harvard University and MIT.
He is a member of the Nayional Academy of Science, the Norwegian Academy of Science and Letters, and the American Academy of Arts and Sciences.
He is a fellow and award recipient of the American Meteorological Society and the American Geophysical Union.
He is also a fellow of the American Association for the Advancement of Science, and was a lead author of the UN IPCC’s third assessment report’s scientific volume.
Quotes from
the 28 page PDF,
at the link above:
"It is commonly accepted that increasing CO2 in the atmosphere should lead to some warming (e.g. Arrhenius, 1896; Callendar, 1938).
This, per se, is not particularly worrisome.
The notion that any warming, however small, is evidence of coming disaster defies reason.
Remember, in natural systems, fluctuations are the norm.
For example, your body temperature always fluctuates a little.
Skyscrapers always sway a little.
This is a characteristic of all stable systems.
With respect to CO2, the dose is determined by what we call climate sensitivity.
By convention, this is the eventual total increase in global mean temperature associated with a doubling of CO2.
The reason we refer to a doubling is that the impact of each doubling is the same: i.e. a well-established equation based on empirical data shows that we get the same warming from an increase from 400 parts per million (ppm) to 800 ppm as we would from 200 ppm to 400 ppm (Pierrehumbert, 2011).
That is to say, the impact of each added unit of CO2 is less than the impact of its predecessor.
n addition, reasonably straightforward calculations suggest that, all other indirect factors (e.g. clouds) being held constant, a doubling of CO2 should produce about one degree Celsius (1°C) of direct warming—a value that is not generally held to be alarming (Wilson and Gea-Banacloche, 2012).
" ... we have seen a welcome warming of about 1°C.
After all, the Little Ice Age was hardly considered optimal.
The IPCC does not claim all of this small warming is due to increased greenhouse gases, but even if it were, it does not, on the face of it, suggest a high sensitivity.
However, most models employed by the UN’s Intergovernmental Panel on Climate Change display higher sensitivities (currently ranging from 1.5° – 4.5°C).
Moreover, the UN argues that higher values portend profound dangers (a dubious claim in its own right).
" ... many attempts to present this issue to the public have been oversimplified to the point of being totally misleading to both those endorsing alarm and to so-called skeptics (a previously honorable designation, but now claimed to be equivalent to holocaust denial).
" ... the greenhouse substances in the atmosphere diminish with altitude until, at some level, the infrared radiation can indeed escape to space.
Most discussions of the greenhouse effect restrict themselves to clear air where only the greenhouse gases are relevant. However, the infrared opacity of upper-level cirrus clouds is often large enough (Choi et al, 2005)
that when such clouds are above the emission level for the greenhouse gases, they block the infrared radiation from the gases ...
This is very important because in the presence of such clouds, the presence of the greenhouse gases below these clouds becomes relatively irrelevant to the greenhouse effect.
In particular, models fail to describe the behavior of upper-level cirrus clouds.
The very existence of such clouds and their substantial variability makes the description of the water vapor feedback incomplete unless one also considers the fact that this feedback only significantly operates in the variable area that is free of such clouds.
" ... a comparison of the present climate, that of the last glacial maximum (18 thousand years ago), and the Eocene (about 50 million years ago) shows that equatorial temperatures have not changed much, but that the temperature difference between the equator and the pole, changed profoundly.
However, since greenhouse-induced global warming became the focus of climate concern, the emphasis shifted to the global mean temperature anomaly.
The original basis for considering that high sensitivity is possible (namely, the hypothetical water vapor feedback of Manabe and Wetherald, 1975) is clearly contradicted by the measurements ... "
" ... for about 95 percent of the time since complex life systems appeared (about 600 million years ago), levels of CO2 were much higher than they are anticipated to become (as much as 10-20 mes today’s levels) without evidence of a relationship to global mean temperature."