It is a tenet of catastrophic anthropogenic global warming theory (CAGW) that our carbon dioxide emissions are the major cause of recent global warming. Although carbon dioxide is a very weak greenhouse gas, CAGW theory holds that it is enough to start the warming process which, in turn, evaporates water, and water vapor is a very strong greenhouse gas. CAGW proponents ignore the fact that more water vapor in the air produces clouds which block the sun (more on that below).

It follows from CAGW doctrine that more carbon dioxide emissions should increase the humidity of the air, thus establishing an enhanced greenhouse effect. Is that happening?

A new paper, Trends in U.S. surface humidity, 1930 – 2010, Journal of Applied Meteorology and Climatology, finds just the opposite: “Average long-term trends (1930 – 2010) indicate that temperature has warmed, but little change has occurred in dewpoint and specific humidity.” In other words, the mechanism for CAGW’s enhanced greenhouse effect is not happening according to observational data.

How, then, do we account for warming in the 20^th Century? Back in 2005, Dr. Roy Spencer published a book: “The Great Global Warming Blunder: How Mother Nature Fooled the World’s Top Climate Scientists” (see my review here). In that book Spencer proposed that “The most obvious way for warming to be caused naturally is for small, natural fluctuations in the circulation patterns of the atmosphere and ocean to result in a 1% or 2% decrease in global cloud cover. Clouds are the Earth’s sunshade, and if cloud cover changes for any reason, you have global warming — or global cooling.” Could such a small change in cloud cover be significant?

A new paper just published in the Journal of Climate finds that global cloudiness has decreased over the past 39 years from between 0.9 to 2.8% by continent. See graphs and a discussion of the paper at WUWT here.

The first paper falsifies the major CAGW tenet; carbon dioxide has been increasing but there has been no increase in humidity. The second paper provides confirmation of a natural control of global temperatures.

For a more detailed discussion of climate sensitivity to carbon dioxide see here. “Examination of Earth’s climate sensitivity by varied derivation reveals climate to be remarkably insensitive to changes in forcing from enhanced greenhouse effect.” “Evaluation of Earth’s natural greenhouse effect reveals forcing response to be considerably less than line by line spectral radiance evaluation would suggest. Net feedbacks are found to be negative.”

See also:

A Perspective on Climate Change a tutorial

Carbon Dioxide and the Greenhouse Effect

Humans and the Carbon Cycle

CERN experiment confirms cosmic ray effect on climate

20^th Century temperatures explained as natural recovery from Little Ice Age

“Scientists have long debated about the impact on global climate of water evaporated from vegetation. New research from Carnegie’s Global Ecology department concludes that evaporated water helps cool the earth as a whole, not just the local area of evaporation, demonstrating that evaporation of water from trees and lakes could have a cooling effect on the entire atmosphere.” –from press release Carnegie Institution.

The abstract from the paper:

Land use and land cover changes affect the partitioning of latent and sensible heat, which impacts the broader climate system. Increased latent heat flux to the atmosphere has a local cooling influence known as ‘evaporative cooling’, but this energy will be released back to the atmosphere wherever the water condenses. However, the extent to which local evaporative cooling provides a global cooling influence has not been well characterized. Here, we perform a highly idealized set of climate model simulations aimed at understanding the effects that changes in the balance between surface sensible and latent heating have on the global climate system. We find that globally adding a uniform 1 W m 2 source of latent heat flux along with a uniform 1 W m 2 sink of sensible heat leads to a decrease in global mean surface air temperature of 0.54 ± 0.04 K. This occurs largely as a consequence of planetary albedo increases associated with an increase in low elevation cloudiness caused by increased evaporation. Thus, our model results indicate that, on average, when latent heating replaces sensible heating, global, and not merely local, surface temperatures decrease.

Read full paper here.

Evaporation uses heat energy to put water vapor into the atmosphere. Water vapor is a strong greenhouse gas. Furthermore, when that water vapor condenses into rain or snow, it gives up its heat back to the atmosphere. The evaporation-condensation cycle is, however, energy neutral. The difference, apparently is that the cycle produces clouds which reflect sunlight, less energy reaches the ground. According to the Carnegie research, the net effect is one of cooling. IPCC climate models do not do well with clouds and assume a positive feedback, whereas the Carnegie research shows a negative feedback. Note that the Carnegie research is also a computer simulation. With all computer modeling, results depend on assumptions. In view of the poor record  of the IPCC climate models versus observations, it seems that the Carnegie model is closer to reality.

See also:

A Basic Error in Climate Models

Climate Model Projections vs Real World Observations

A Perspective on Climate Change a tutorial

This post is a review of the book: The Great Global Warming Blunder, How Mother Nature Fooled the World’s Top Climate Scientists, by Dr. Roy Spencer.

Meteorologist Dr. Roy Spencer is a principal research scientist at the University of Alabama in Huntsville, formerly a senior scientist for climate studies at NASA, and now leads the U.S. science team for the Advanced Microwave Scanning Radiometer for EOS on NASA’s Aqua satellite. Dr. Spencer is the co-developer of the original satellite method for precise monitoring of global temperature from Earth orbiting satellites.

Dr. Spencer makes two main contentions in his book. First, the climate is much less sensitive to carbon dioxide than the Intergovernmental Panel on Climate Change (IPCC) says it is. This means that carbon dioxide is not a significant driver of temperature. Second, the Pacific Decadal Oscillation (PDO) alone can account for most of the temperature variation in the 20^th Century and can account for 75% of the global warming. He supports these contentions with both observational and experimental evidence in the book. Spencer published this evidence in the peer-reviewed, Journal of Climate in 2008, but it was ignored by the IPCC and by the mainstream press – hence the book. He is taking his case to the public. The book is written in layman’s terms with easy-to-understand examples of how the climate works. He also takes on the establishment and shows how there is a vested interest in maintaining the fiction that there is a climate change problem.

Some excerpts:

“Conceptually, there are two main processes that govern any kind of climate change: forcing and feedback.” This is cause and effect, which Spencer says the IPCC has gotten mixed up.

“Worries over catastrophic global warming rest entirely on the belief that our climate system is very sensitive, that is, dominated by positive feedbacks, which amplify any warming or cooling influence. A few scientists are predicting planetary doom as a result of our burning of fossil fuels, and politicians are now using standard propaganda techniques to convince you that we must act quickly to save the Earth.”

“Whether it is the Earth’s climate, or a pot of water on the stove, a temperature change is always caused by an imbalance between energy gained and energy lost.”

“While forcing (an energy imbalance) determines whether a temperature change will occur, feedback determines how big that temperature change will be. It is feedback that ultimately determines whether man-made global warming is catastrophic, or merely lost in the noise of natural climate change.”

“A mix-up between cause and effect in observations of cloud behavior from satellites has led to the false illusion that our climate system is dominated by positive feedback. This, in turn, has led to the development of highly sensitive climate models that predict large amounts of global warming. But when the separate influences of forcing and feedback (cause and effect) are isolated, recent satellite data reveal the climate system to be dominated by negative, not positive, feedback.”

“In order to convince Congress to fund research into a problem, you must first convince them that a problem exists. This automatically makes man-made global warming a particularly lucrative field for funding – as long as the threat of man-made global warming continues. There are managers at NASA, the National Oceanic and Atmospheric Administration, the National Science Foundation, and the Department of Energy whose careers now depend on a continuous flow of research dollars through them to the science community.” Spencer notes that his own research funding comes from NASA.

“…natural cloud fluctuations in the climate system will cause a bias in the diagnosed feedback in the direction of positive feedback, thus giving the illusion of an overly sensitive climate system.”

(This statement follows a discussion of radiative and non-radiative forcings; read the book to find out what these are.)

” … the IPCC has ignored… radiative forcing generated internal to the climate system as a potential source of climate change.” What that means is “that the climate models are too sensitive, which is why they predict so much global warming for the future. In contrast, the satellite evidence indicates that the climate system is quite insensitive, which means that it doesn’t really care how big your carbon footprint is. Rather than 1.5 to 6 deg. C (or more) of warming as predicted by the IPCC, a careful examination of the satellite data suggests that man-made warming due to a doubling of atmospheric carbon dioxide could be less than 1 deg. C (1.8 deg. F) – possibly much less.”

“It would take natural variations of little more than 1 percent in global average cloud cover to explain most of the climate change seen in the last 2,000 years, yet our ability to measure such small changes has existed for only the last ten years.”

“The idea that nature was in delicate balance before mankind came along is religious, not scientific. Given the necessity of carbon dioxide for life on earth, we need to consider the possibility that more CO₂ in the atmosphere will be better for life on earth, not worse.”

I recommend this book. It is a good read. It gives an easily understandable explanation of how the climate works. The book is available from Amazon.com.