Critique of Junk Science on Climate Change

An acquaintance cited this as a critique of climate science that debunks the “myth” of anthropogenic contributions to climate change:
http://junksciencearchive...reenhouse/What_Watt.html.  My response follows. 

From the beginning of this article, she is minimizing the significance of the role of CO₂ in the value of the mean global temperature.  She is also claiming that mean global temperature is not a significant number.  She writes, “… many excellent researchers who have pointed out that the concept of a globally averaged forcing constant is flawed and they are right. Sensitivity absolutely depends on where the forcing is applied and when. Unfortunately a globally averaged forcing value is applied via climate models and cited in IPCC documents and we are thus stuck with addressing an invalid value in common use.”  However, she doesn’t name these excellent researchers, nor does she explain why globally averaging the value is invalid.  When she states that the sensitivity depends on where and when, she is correct as for local effects.  But because of the convective action of the atmosphere and ocean, these local effects are naturally averaged out over the globe.  If one thinks about heating one’s house in winter, one could just as easily say that since the air coming from the vents when the furnace is running causes convection to occur near the vents and not so much away from the vents, trying to calculate the mean temperature rise in your house based on the total amount of heat coming from the furnace minus the heat that is being lost through the walls and ceiling is invalid.  Her reasoning, at least as stated, is incorrect. 
She next states, “climate models make much of water vapor "feedbacks" -- a multiplier effect due to a small warming from carbon dioxide increasing evaporation and thus adding to the major greenhouse gas, water vapor -- this in turn is supposed to increase the greenhouse effect, leading to more evaporation and yet more warming and so on. The amount of water vapor in the atmosphere is not a simple function of evaporation, however. All of the water vapor that is being continuously evaporated from the Earth's surface must eventually return to the surface as precipitation. The climate system strikes a balance, allowing only so much water vapor to accumulate before it is depleted by either rain or snow."

A fact that she is overlooking is that the amount of water vapor in the atmosphere is dependent on the temperature of the air.  The warmer the air, the more water vapor it can contain and on average will contain.  This is why we talk about relative humidity instead of absolute humidity.  Relative humidity is the amount of water vapor present compared to the amount it can hold.  The dew point is the temperature at which relative humidity equals 100%.  This temperature varies with the amount of water vapor actually present.  As an illustrative example without doing real calculations, if the RH is 70% at 50 F, then the dew point might be 40 F while if the RH is 70% at 70 F, the DP might be 45 F.  One can see this if one has noticed that, in general, dew won’t be present in winter, on those days when temperatures have remained above freezing, until a lower temperature than in summer.  The atmosphere will approach a dynamic equilibrium of the amount of water vapor present based on the global mean temperature.  It will vary from place to place and with the time of day, always changing everywhere, but on average, the vapor content will rise as the temperature rises.  There will be both more precipitation and more evaporation, but the balance will increase with increasing temperature.  See: http://www.giss.nasa.gov/research/briefs/lacis_01/ for a discussion based on recent satellite measurements.
She states, “climate models use λ values of 0.75 ± 0.25 °C per Wm^-2, 5-10 times greater than empirical measures support.”  This is false.  She has chosen the lowest empirical value available.  A value of ~0.7 k/Wm^-2 is empirically derived as shown in this article from Wikipedia: http://en.wikipedia.org/wiki/Climate_sensitivity.  This article includes citations giving a range of values for the climate sensitivity parameter. The rest of her article is similarly skewed.  She consistently cherry picks the data and research to support her point of view.  Consider her referenced to an article by Lyman et al.  It initially claimed that there had been a cooling of the ocean surface temperature in the early 2000s, but they later published a correction that stated that there had been no cooling, but the temperature had been stable during the three year time period of their study.  She includes this information, which is good, but then does not correct her conclusions to account for this.

In her discussion of cloud cover effects, she emphasizes only the negative feedback.  This is unwarranted.  Based on recent studies, it appears that thick clouds have a negative feedback effect (net cooling effect), but thin cloud cover like from cirrus clouds or contrails have a net positive feedback effect (net warming).  The balance between these two is unclear, but it seems to be that there is a net positive feedback based on the most recent satellite measurements.  See: http://sciencetrends.blogspot.com/2011/04/positive-and-negative-feedback-in.html for more detail.
Based on my analysis of her article, she is strongly biased against anthropogenic global warming.  She does not consider all the data that contradicts her position.  If this article is an example of how he analyzes scientific results, “Junk Science” applies more to what she has written than the science that she is trying to debunk.  The good climate scientists, as illustrated in the quoted Wikipedia article, cite a range of results, trying to make it as representative as possible.  There is much uncertainty in the climate models and in some of the data as well as a glaring lack of data in some areas.  However, on balance, the available data do support the contention that the global climate is warming and that it is warming at a rate higher than can be accounted for without considering the effect of anthropogenic CO₂.
Similarly, Bryson, http://drywind.net/blog/science/climatologist-who-discovered-jet-stream-debunks-human-caused-global-warming/75/, has discounted recent data and seems to dismiss climate model projections because he doesn't think they are good enough.  He may be right, but the fact is that the mean value of the results of the computer models twenty years ago underestimated the temperature rise and sea level rise.  Current models are improved because of more accurate and finer grained data.  The results published in the latest IPCC report,  a not perfect summary of the status of climate science, tend toward the conservative end of the projections.  If one actually considers all the data and not just the data that fits one's preconception or bias, the rising temperature trend is clear and the fact that human activity is contributing is clear.  It is not clear exactly how much of the warming is due to human activity, but it appears to be at least 30% of it.
It has also been suggested that higher CO2 content was actually beneficial because some plants were growing faster.  It is true that some plants are growing faster but that is only one effect (and does anyone in Georgia really want kudzu to grow any faster than it already does?).  The resulting warming from the increasing CO2 level also is eliminating the habitats of several species and possibly contributing to the decline of amphibians by enhancing the ability of certain fungal diseases to spread.  The warming is causing the Greenland ice cap and many continental glaciers to melt at an increasing rate, raising the sea level and threatening low-lying coastal areas and islands.  Parts of the Antarctic ice cap are increasing while other parts are decreasing, but overall there is a net decrease in the ice contained there that is also contributing to the sea level rise.  Rising temperatures also are improving the agricultural potential of northern areas such as Greenland and Iceland.  What have historically been considered tropical diseases, such as malaria and dengue fever, are now spreading to mid latitudes.  The ocean is acidifying, threatening the health of the plankton that form the base of the global food chain.  So obviously the effects are varied and complex.  The net effect, though, is deleterious to many species of land animals, including humans.  If the acidification continues, it will negatively impact nearly every species except bacteria.