You just got done saying how insignificant CO2 is for climate impact (which is contrary to almost all published work in the field). Why don't you just tell us exactly what you mean then?
______________________________________________________________ I'll let you fill in the blank. You seem to enjoy it.
[This message has been edited by Formula88 (edited 08-25-2013).]
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05:06 PM
jmclemore Member
Posts: 2395 From: Wichita Ks USA Registered: Dec 2007
Clouds reflect solar radiation (cooling effect) and trap solar radiation (warming effect), in varying proportions, depending on what kind of cloud: Low altitude, high altitude, equatorial, temperate zone, polar, water droplets, ice crystals--it boggles the collective scientific mind.
Observations of changes in cloud patterns from 1952 forwards, to date, are consistent with a net cooling effect on global climate. This cooling effect has been less than the warming effect from anthropogenic greenhouse gas emissions, so the planet has still continued to warm, since 1952.
Cloud feedbacks are the wildcard in IPCC projections of global warming for the rest of this century. It's not yet known whether the net effect from clouds (currently, a cooling effect that partially mitigates global warming) will continue to be a cooling effect, or will change to a warming effect, as cloud formations change in a world that is still warming, because of the current equation:
anthropogenic greenhouse warming effect > net cooling effect from clouds
The unknowns associated with cloud feedbacks are one of the main reasons why the IPCC predictions of global warming, forwards to 2100, range from "somewhat disruptive to society", on the low end, up to "massively disruptive to society" on the high end.
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Unfortunately, the fact that clouds cool the planet on average tells us nothing about how cloud properties might change in a new climate. Suppose for example that the coverage of high clouds increased in a global warming scenario, while low clouds didn’t change at all. Because high clouds have a warming influence, one would expect this effect to amplify any warming that is caused by carbon dioxide or other human activities. This is an example of a positive feedback loop, but unfortunately we have very little understanding of cloud physics in a warming world. If the coverage of low clouds increased and reflected more sunlight, this would be a negative feedback, and would tend to mitigate the effects of human activities. Because of this uncertainty however, we can’t say with high confidence whether doubling the CO2 in our atmosphere will warm the planet by 3.5 degrees Fahrenheit or 8 degrees Fahrenheit, both of which are large for a global average but still call for completely different socio-economic and ecological impacts (there’s good evidence from past climate changes that the Earth isn’t any more or less sensitive than those extremes).
______________________________________________________________ I'll let you fill in the blank. You seem to enjoy it.
Well put. He certainly can't be counted on to understand what we are discussing, let alone be able to actually discuss it. When talking to him, it's like he isn't even having the same conversation.
[This message has been edited by fierobear (edited 08-26-2013).]
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10:03 AM
Mickey_Moose Member
Posts: 7543 From: Edmonton, AB, Canada Registered: May 2001
Introduction Since of the Earth's atmosphere is out-of-balance with the conditions expected from simple chemical equilibrium, it is very hard to say what precisely sets the level of the carbon dioxide content in the air throughout geologic time. While scientists are fairly certain that a 100 million years ago carbon dioxide values were many times higher than now, the exact value is in doubt. In very general terms, long-term reconstructions of atmospheric CO2 levels going back in time show that 500 million years ago atmospheric CO2 was some 20 times higher than present values. It dropped, then rose again some 200 million years ago to 4-5 times present levels--a period that saw the rise of giant fern forests--and then continued a slow decline until recent pre-industrial time.
History of Atmospheric CO2 through geological time (past 550 million years: from Berner, Science, 1997). The parameter RCO2 is defined as the ratio of the mass of CO2 in the atmosphere at some time in the past to that at present (with a pre-industrial value of 300 parts per million). The heavier line joining small squares represents the best estimate of past atmospheric CO2 levels based on geochemical modeling and updated to have the effect of land plants on weathering introduced 380 to 350 million years ago. The shaded area encloses the approximate range of error of the modeling based on sensitivity analysis. Vertical bars represent independent estimates of CO2 level based on the study of ancient soils.
Well put. He certainly can't be counted on to understand what we are discussing, let alone be able to actually discuss it. When talking to him, it's like he isn't even having the same conversation.
You're right, it's like not even having the same conversation, because you avoid (or are incapable of having) meaningful discussion. Spin, ignore, deflect.
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11:43 AM
Aug 27th, 2013
rinselberg Member
Posts: 16118 From: Sunnyvale, CA (USA) Registered: Mar 2010
Originally posted by NickD3.4: Their introduction is good enough for me.....in the 1970s it was all BS about global cooling and doom and gloom predictions about the next ten years. When I was a kid growing up, I was preached to about the coming ice age and how we caused it. Then...one magical day, things starting warming and it shifted to global warming!
what a ****ing joke. They can't predict the weather a week from now and I am supposed to trust fallible models being built to predict decades out? As they say in the computer model world, junk in=junk out, and the fact people think they have these models as being "accurate" smacks of arrogance.
Good luck believing the bulls**t. I have real issues to be worried about, not lining the pockets of climate change pimps to make another buck.
This saddens me. The member who posted that (above) is a blogger who has posted (here and on his own blog) many well thought out and deeply analytical reports and OpEds concerning law enforcement and police issues, and the pros and cons of anti-drug legislation and enforcement. He made that post (and some others in a similar vein) on another thread, but I am addressing it here, because it fits so perfectly with the subject of this thread (which I started). I have seen other PFF members posting in a similar vein about the "Ice Age Predictions of the 1970s", so I wanted to address this in a general way, for all members who decide to read here.
A similar report from Time Magazine of 1974, titled "Another Ice Age?", was used as the introduction to a Penn & Teller "Bulls**t!" segment about global warming--of which, I offered a substantial critique: https://www.fiero.nl/forum/F...057033-69.html#p2722
Penn Jillette (I won't include Teller, because he never speaks) wanted to discredit AGW (the anthropogenic explanation for global warming), and all of its likely implications, using a deja vu strategy of equating it with the impending ice age speculations of the 1970s.
The estimable AGW skeptic and former meteorologist Anthony Watts recently posted a long list of media reports (looks like upwards of 50 to perhaps as many as 100 separate reports) from 1970 to 1979 with alarming titles suggesting the likelihood of an imminent return to the planetary climate of the last major glacial, before the humongous polar ice sheets retreated about 15,000 years ago.
The Time and Newsweek reports (and many of these other media columns, I would guess) leave readers with the impression that there was a substantial scientific consensus that the planet was on the threshold of a major climatic shift towards significantly colder temperatures, with serious implications for the global food supply and other attendant impacts.
But there wasn't.
In The Myth of the 1970's Global Cooling Scientific Consensus (Peterson, Connolley and Fleck; Bulletin of the American Meteorological Society; September, 2008), the scientific literature of this period was reviewed, with these results:
Peterson et al (2008) fleshes out the current significance of this pie chart:
quote
Climate science as we know it today did not exist in the 1960s and 1970s. The integrated enterprise embodied in the Nobel Prize winning work of the Intergovernmental Panel on Climate Change existed then as separate threads of research pursued by independent groups of scientists. Atmospheric chemists and modelers grappled with the measurement and understanding of carbon dioxide and other atmospheric gases while geologists and paleoclimate researchers tried to understand when Earth slipped into and out of ice ages, and why. An enduring popular myth suggests that in the 1970s the climate science community was predicting “global cooling” and an “imminent” ice age, an observation frequently used by those who would undermine what climate scientists say today about the prospect of global warming.
A review of the literature suggests that, to the contrary, greenhouse warming even then dominated scientists’ thinking about the most important forces shaping Earth’s climate on human time scales. More importantly than showing the falsehood of the myth, this review shows the important way scientists of the time built the foundation on which the cohesive enterprise of modern climate science now rests.
Some of the 1970s "coldists"--scientists who were particularly concerned about the cooling effects of anthropogenic aerosols like smoke particles and sulfur compounds--were soon backtracking. Here's an excerpt from a column in New Scientists of May, 2007, titled Climate myths: They predicted global cooling in the 1970s:
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One of the sources of this idea may have been a 1971 paper by Stephen Schneider, then a climate researcher at NASA's Goddard Space Flight Center in Maryland, US. Schneider's paper suggested that the cooling effect of dirty air could outweigh the warming effect of carbon dioxide, potentially leading to an ice age if aerosol pollution quadrupled.
This scenario was seen as plausible by many other scientists, as at the time the planet had been cooling (see Global temperatures fell between 1940 and 1980). Furthermore, it had also become clear that the interglacial period we are in was lasting an unusually long time (see Record ice core gives fair forecast).
However, Schneider soon realised he had overestimated the cooling effect of aerosol pollution and underestimated the effect of CO2, meaning warming was more likely than cooling in the long run. In his review of a 1977 book called The Weather Conspiracy: The Coming of the New Ice Age, Schneider stated: "We just don't know...at this stage whether we are in for warming or cooling - or when." A 1975 report (pdf format) by the US National Academy of Sciences merely called for more research.
Returning to more current views, the New Scientist column ended with this:
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The calls for action to prevent further human-induced global warming, by contrast, are based on an enormous body of research by thousands of scientists over more than a century that has been subjected to intense--and sometimes ferocious--scrutiny. According to the latest IPCC report, it is more than 90% certain that the world is already warming as a result of human activity (see Blame for global warming placed firmly on humankind).
1971 was a banner year for coldists, as Climatepedia relates:
quote
In the 1970s, the uncertainties stemming from the cooling properties of aerosols led some scientists to believe that the world might enter another ice age as a result of unprecedented fossil fuel burning. One commonly cited global cooling paper is Rasool and Schneider's Atmospheric Carbon Dioxide and Aerosols: Effects of Large Increases on Global Climate, written in 1971. It initially found that although higher CO2 concentrations would increase temperatures, the cooling effect of aerosols would outweigh any warming--so much so that the earth would cool. Rasool and Schneider’s overestimation of the albedo effect and underestimation of the CO2-induced warming resulted in an incorrect global cooling calculation. In this way, global cooling and global warming are much more closely related than their names suggest. Some of Rasool and Schneider’s mistakes were later self-acknowledged by the authors a year after the paper’s original publication.
So, criticism of this paper revealed some flaws, and within a year (1972), Rasool and Schneider backtracked and removed some of the "cold" from of their "coldest" predictions.
Climatepedia describes how the lay media (or was that the "lie" media?) were crying wolf:
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In the 1970s, media outlets ran a disproportionate amount of stories on global cooling theories, in part because cold temperatures were on the public consciousness. Many parts of Asia and North America had experienced abnormal cold periods in 1972 and 1973. In addition, the first satellite measurements showed that the earth’s average temperature was actually decreasing from 1940 to around 1970. The media’s focus on global cooling fueled public opinion that the theory was a consensus of the scientific community, though no such consensus existed
This raises the question of what caused the Mid-20th Century Cooling--or "Flattening"--the word I would use:
quote
There was a very slight cooling in the average global surface temperature from about 1940 to 1975. Although the global temperature only decreased by approximately 0.1°C, this period represents a divergence from the warming periods of 1915 to 1940 and 1975 to Present.
The "warmists" at Skeptical Science, a blog that consistently lines up with the AGW point of view, offer an explanation:
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... anthropogenic sulfur emissions appear to be the main cause of the mid-century cooling. These emissions decreased the mean global surface temperature by approximately 0.5°C during this period, while anthropogenic greenhouse gas emissions caused a warming of approximately 0.4°C. Therefore, even though greenhouse gas emissions continued to have a warming effect during this period, it was more than offset (hidden) by anthropogenic aerosol emissions, until those emissions were brought under control by government intervention while greenhouse gas emissions continued to increase unabated. In other words, the mid-century cooling is actually an expected result based on our current understanding of climate science, and is successfully hindcasted by climate models (Meehl 2004).
Numerous studies have since shown that the cooling trend [1940 to 1975] was the result of fine aerosol pollution, which reflected solar radiation back out into space (also known as "global dimming").
So, according to these lines of thought, AGW reasserted itself, starting about 1975, because of the widespread abatement of sulfate and other aerosol pollutants after the adoption of the Clean Air Act of 1970 and subsequent legislation in the U.S. and similar measures in other industrialized countries.
What about the possibility that a resurgence of aerosol pollution will play havoc with the IPCC's predictions of continued global warming--a resurgence of aerosol pollution from countries like China, India, Indonesia, Mexico, Brazil and Thailand: countries with rapidly expanding economies and less than stellar track records of air quality regulation, compared to the U.S. and Western Europe?
I think that these countries will step up to the plate in terms of air quality (aerosol abatement), because of international pressure and the demands of their own populations. Here's something evidential:
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The evolution of global and regional anthropogenic SO2 emissions in the last decade has been estimated through a bottom-up calculation. After increasing until about 2006, we estimate a declining trend continuing until 2011. However, there is strong spatial variability, with North America and Europe continuing to reduce emissions, with an increasing role of Asia and international shipping. China remains a key contributor, but the introduction of stricter emission limits followed by an ambitious program of installing flue gas desulfurization on power plants resulted in a significant decline in emissions from the energy sector and stabilization of total Chinese SO2 emissions. Comparable mitigation strategies are not yet present in several other Asian countries and industrial sectors in general, while emissions from international shipping are expected to start declining soon following an international agreement to reduce the sulfur content of fuel oil. The estimated trends in global SO2 emissions are within the range of representative concentration pathway (RCP) projections and the uncertainty previously estimated for the year 2005.
So China leads, and India and the other such countries will follow (IMO).
I wouldn't blame anyone for a certain rational skepticism about the current state of climate science and its flagship product: the anthropogenic explanation of global warming, as exemplified by the warmist predictions of the IPCC.
But let's not irrationally "diss" today's climate science because of what happened in the 1970s: it was the lay media that cried wolf about global cooling in the 1970s--not the scientists.
Science and the media both have upped their game considerably in the 33 years that followed.
[This message has been edited by rinselberg (edited 08-27-2013).]
That GISS graph is a hoot. The net increase from 1940 to ~2010 is about 1/2 degree. That is over 70 years. Yet it is portrayed like a dramatic increase. Think about it. 1/2 degree over 70 years. Now that is Global Warming
[This message has been edited by Arns85GT (edited 08-27-2013).]
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02:12 PM
Scottzilla79 Member
Posts: 2573 From: Chicago, IL Registered: Oct 2009
But let's not irrationally "diss" today's climate science because of what happened in the 1970s: it was the lay media that cried wolf about global cooling in the 1970s--not the scientists. Science and the media both have upped their game considerably in the 33 years that followed.
There is some interesting stuff here, but what strikes me is this bolded part. It's not the laymedia that would call anyone who disagreed with global warming all sorts of names. Many people believe that having any doubts in the current iteration of climate science are equal to those who think the world is 6000 years old. It's really difficult to listen rationally if everytime you ask a question you are called names.
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02:59 PM
PFF
System Bot
rinselberg Member
Posts: 16118 From: Sunnyvale, CA (USA) Registered: Mar 2010
Originally posted by Arns85GT: That GISS graph is a hoot. The net increase from 1940 to ~2010 is about 1/2 degree. That is over 70 years. Yet it is portrayed like a dramatic increase. Think about it. 1/2 degree over 70 years. Now that is Global Warming
The opera isn't over until the fat lady sings.
That fat lady in the global warming opera is the Arctic.
Here's an excerpt from a very current NASA webpage:
As far back as 1896, the Swedish scientist Svante Arrhenius hypothesized that changes in the concentration of carbon dioxide in Earth’s atmosphere could alter surface temperatures. He also suggested that changes would be especially large at high latitudes.
Arrehenius didn’t get every detail right, but his argument has proven to be pretty sound. Since the mid-20th Century, average global temperatures have warmed about 0.6°C (1.1°F), but the warming has not occurred equally everywhere. Temperatures have increased about twice as fast in the Arctic as in the mid-latitudes, a phenomenon known as “Arctic amplification.”
The map above shows global temperature anomalies for 2000 to 2009. It does not depict absolute temperature, but rather how much warmer or colder a region is compared to the norm for that region from 1951 to 1980. Global temperatures from 2000–2009 were on average about 0.6°C higher than they were from 1951–1980. The Arctic, however, was about 2°C warmer.
That GISS graph, based on Global Mean Temperature, may look like a "hoot" to you, but one of the keys to unraveling what's going on with the earth's climate is the spatial distribution of temperature anomalies.
The science of AGW (Anthropogenic Global Warming) is far from being completely settled, but those who calls it already falsified are risking considerable egg on their faces. Depending on how much of the remainder of this century that they may be alive to witness.
The reports of AGW's death are greatly exaggerated.
[This message has been edited by rinselberg (edited 08-27-2013).]
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06:14 PM
fierobear Member
Posts: 27083 From: Safe in the Carolinas Registered: Aug 2000
Some Facts that I accept in regards to natural and human released gases into the atmosphere.
These gases are potentially bad Carbon dioxide Methane Nitrous oxide CFC-12 : if I'm correct we are depleting supply but not manufacturing any more. HCFC-22 : if I'm correct we are depleting supply but not manufacturing any more. Tetrafluoromethane Hexafluoroethane Sulfur hexafluoride Nitrogen trifluoride
This represents only the human release contribution. (not the natural releases such as volcanic activity)
Of the human released gases this is a representation of what human activities released them.
Also a fact is that while the EPA and IPCC measure water vapor in our atmosphere it is also true that they only focus on human release gases. The reason they do not focus on natural releases come from an assumption that only human releases can be controlled.
For example: While they acknowledge water vapor and volcanic activity as neutral releases They do not include those numbers when discussing human releases of GHG.
----------------------------------------------------------------------------------------------------------------- My Opinion and Suspicion.
It is hard to find a cliff notes version of "Natural GHG Releases".
When I have found a mention of natural contributors it is usually a general statement that quickly sweeps you back into a detailed presentation of human release GHG.
I have not (in searching) found data for both Natural and Human releases presented side by side by the same group.
Most of the proposed schemes for combating human released GHG's, mostly focus on CO2 as the primary basis for taxation.
Recently the EPA, IPCC and The UN have increased their characterization of Water Vapor as a greenhouse gas.
It is my opinion that the major Government and Global Players pushing for taxing greenhouse gas releases are focusing on the CO2 and Water Vapor because they make up the majority of gases present in the atmosphere. This gives them the ability to create massive new revenue streams via taxation.
Between Water Vapor and CO2 , both are massive enough that a change of 1% is a larger than a 1% change in a GHG that is a fraction of the size.
While I think there are GHG present in the atmosphere and that they can have an effect on global weather and temperatures, I can not help but find it suspicious that those calling for taxation (cap and trade) as a regulatory method have more to gain from the control and taxation of human activities than finding an actual solution to fix the problem.
At this point I have no problem accepting GHG and Weather Changes can and do contribute to one another. However, I do not (yet) accept GHG or Weather changes being the a sole cause or effect of the other. (they influence each other).
Though I'm am a skeptic, I have moved toward the claims on the basis of effect, but not cause. Where I remain highly skeptical is on the issue of invest interest(s). To many people and governments derive their funding or potential (tax) funding through affirming a position. without conclusive proof of their intent or will, No one can reasonably expect blind confidence.
[This message has been edited by jmclemore (edited 08-28-2013).]
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04:59 PM
Aug 29th, 2013
Tony Kania Member
Posts: 20794 From: The Inland Northwest Registered: Dec 2008
Holy cow! Global warming is real, and we have an explanation as to why the Earth has not warmed up as much as we said!
I hate the taste of deflection...
---------------------------------------------------------------------------------- Cooler Pacific Ocean May Explain Climate Change Paradox
LiveScience.com By Denise Chow, Staff Writer August 28, 2013 NatureLiveScience .
Cooling sea-surface temperatures in the tropical Pacific Ocean — a phase that is part of a natural warm and cold cycle — may explain why global average temperatures have stabilized in recent years, even as greenhouse gas emissions have been warming the planet, according to new research.
The findings suggest that the flattening in the rise of global temperatures recorded over the past 15 years are not signs of a "hiatus" in global warming, but are tied to cooling temperatures in the tropical or equatorial Pacific Ocean. When the tropical Pacific naturally switches back into a warm phase, the long-term trends in global warming, including more steeply rising global temperatures, will likely increase, said study co-author Shang-Ping Xie, a climate scientist at the University of California, San Diego.
"The engine driving atmospheric circulation on global scales resides in the tropical Pacific," Xie told LiveScience. "When the natural cycle shifts the next time to a warmer state, we're going to see more extreme warming on the global scale." [The Reality of Climate Change: 10 Myths Busted]
A climate paradox
In early May, a carbon dioxide monitor in Hawaii recorded the proportion of carbon dioxide in the atmosphere as being more than 400 parts per million (ppm) for the first time in human history, breaking a 3-million-year-old record. (Parts per million means that, in this example, for every million molecules of air, 400 of them are carbon dioxide.) But, over the past 15 years, global average temperatures have stabilized rather than sharply increased, as previous predictions suggested they should have, mystifying climate scientists and adding fuel to the fire for climate change skeptics.
"We had this puzzle — the concentration of carbon dioxide was over 400 ppm, last year we had record summer heat waves in the U.S., record retreat of Arctic sea ice. All of these things are consistent with the general warming of the climate," Xie said. "Yet, if you plot the global temperature, you see a flattening average over the last 15 years. On the one hand, scientists are saying carbon dioxide is causing the general rise of global temperatures, but on the other hand, in recent years there is no warming, so something very strange is going on."
Xie and his colleagues set out to solve this mystery using climate models to reproduce the long- and short-term trends based on global climate records from the past 130 years. The researchers found that sea-surface temperatures in the tropical Pacific Ocean, in spite of anthropogenic or manmade effects of global warming, were key ingredients in creating the flattening global temperatures seen in the past 15 years.
"In our model, we were able to show two forces: anthropogenic forces to raise global average temperature, and equatorial Pacific cooling, which tries to pull the temperature curve down, almost like in equilibrium," Xie said.
The effect is similar to the El Niño and La Niña cycles, which are parts of a natural oscillation in the ocean-atmosphere system that occur every three to four years, and can impact global weather and climate conditions, Xie explained. El Niño is characterized by warmer-than-average temperatures in the waters of the equatorial Pacific Ocean, while La Niña typically features colder-than-average waters.
The warm and cool phases in the Pacific Ocean studied by Xie and his colleagues appear to last much longer than the El Niño and La Niña cycles. Previously, the Earth experienced cooling in the tropical Pacific from the 1940s to the 1970s, before oscillating into a warm state from the 1970s to the 1990s.
Current scientific models are unable to predict when the current cooling period will end, Xie said, but when the ocean swings back into a warm phase, parts of the planet may experience warmer temperatures.
"The equatorial Pacific Ocean is associated with distinct regional patterns, like the Pacific coast of North America," Xie said. "Because of equatorial cooling, this area has not been warming as rapidly as before, but when the equatorial Pacific shifts into a warm state, those regions might expect rapid warming, on the order of 2 degrees Celsius [3.6 degrees Fahrenheit] over 15 years."
Implications for a warming planet
Scientists have known that the eastern equatorial Pacific Ocean takes in a significant amount of heat from the atmosphere, but this new study suggests this small portion of the world's oceans could have a big influence on global climate, said James Moum, a professor of physical oceanography at Oregon State University in Corvallis, Ore., who was not involved with the new study.
While the models used in the study rely on some assumptions (for instance, the researchers set the sea-surface temperature to what is observed, rather than computing the temperatures, as would be done in a numerical model), Moum called the research "a brave experiment."
"It provides a physical basis for the current global mean temperature leveling off, while at the same time, points to this equatorial cold tongue as being the major driver for that," Moum told LiveScience.
There are still many unknowns about how this warming and cooling in the Pacific Ocean interacts with man-made greenhouse gas emissions to change the Earth's climate.
"We had El Niñolong before we had anthropogenic forcing — they occur independently of man-made forcing, certainly," Moum said. "Whether they're amplified by it is another question. The flip side of the story is that if this part of the ocean has an outside influence when it cools, it's going to have an outside influence when it warms. It's definitely suggested in the paper that this is a cause for concern."
The detailed findings of the study were published online today (Aug. 28) in the journal Nature.
Follow Denise Chow on Twitter @denisechow. Follow LiveScience @livescience, Facebook & Google+. Original article on LiveScience.
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06:46 PM
avengador1 Member
Posts: 35468 From: Orlando, Florida Registered: Oct 2001
Considering some of the points raised by jmclemore's latest post, I found a brief and nicely written explanation of why water vapor (H2O) is a moot point as far as the MMGW (man made global warming) predictions from the IPCC and other prominent climate science organizations:
But there's more to water vapor than water vapor. The discussion that I just referenced is limited to the greenhouse (warming) effect of water molecules suspended as an invisible gas in the lower atmosphere: the familiar humidity measurement that comes with the standard local weather report. When water vapor condenses in the form of either water droplets or ice crystals and turns into clouds, the climate effects are far more complicated to unravel.
quote
One of the largest uncertainties in global climate models (GCMs) is the response of clouds in a warming world. Determining which types of cloud cover will increase or decrease, whether that will result in a net positive or negative feedback, and how large the feedback will be, are major challenges. The variation in global climate sensitivity among GCMs is largely attributable to differences in cloud feedbacks, and feedbacks of low-level clouds in particular.
For climate scientists who are skeptical that anthropogenic greenhouse gas emissions will cause a dangerous amount of warming, such as Richard Lindzen and Roy Spencer, their skepticism hinges mainly on this cloud cover uncertainty. They tend to believe that as the planet warms, low-level cloud cover will increase, thus increasing planetary albedo (overall reflectiveness of the Earth), offsetting the increased greenhouse effect and preventing a dangerous level of global warming from occurring.
But other researchers have drawn less reassuring conclusions:
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Other studies analyzing satellite data from the International Satellite Cloud Climatology Project (ISCCP), the Advanced Very High Resolution Radiometer (AVHRR), and the Clouds and the Earth’s Radiant Energy System (CERES) such as Chang and Coakley (2007) and Eitzen et al. (2008) have indicated that cloud optical depth of low marine clouds might be expected to decrease with increasing temperature. This suggests a positive shortwave cloud–climate feedback for marine stratocumulus decks.
In another recent paper, Clement et al. (2009) analyzed several decades of ship-based observations of cloud cover along with more recent satellite observations, with a focus on the northeastern Pacific. They found that there is a negative correlation between cloud cover and sea surface temperature apparent on a long time scale—again suggesting a positive cloud-climate feedback in this region.
And:
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Dessler and Loeb (2013) and Zhou et al. (2013) tested the robustness of the Dessler (2010) results. Zhou et al. used cloud measurement data from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite over the same 2000–2010 timeframe, while Dessler and Leob examine how the use of different clear-sky TOA energy flux and surface temperature measurements change the results using the approach in Dessler (2010).
Dessler and Loeb found that the relatively weak but postive short-term cloud feedback found in Dessler (2010) is a robust result across many different datasets. Zhou et al. found a small but slightly negative short-term cloud feedback using the MODIS data. However, the authors conclude that the cloud feedback estimate based on MODIS data is most likely biased low, and the Dessler results are most likely accurate.
In short, while much more research of the cloud-climate feedback is needed, the evidence is building against those who argue for a strongly negative cloud feedback. It's also important to remember that clouds are just one feedback among many, and there is a large amount of evidence that the net feedback is significantly positive, and climate sensitivity is not low.
The most abundant gas typically released into the atmosphere from volcanic systems is water vapor (H2O), followed by carbon dioxide (CO2) and sulfur dioxide (SO2). Volcanoes also release smaller amounts of others gases, including hydrogen sulfide (H2S), hydrogen (H2), carbon monoxide (CO), hydrogen chloride (HCL), hydrogen fluoride (HF), and helium (He).
As I said here in my very first post, year in and year out, human activities emit 100 times or more CO2 than all the world's continental, island and submarine volcanos.
Marie Edmonds, a volcanologist at Cambridge University agreed. While volcanoes are the most important natural source of atmospheric CO2, she noted, "The results show clearly that the amount is 100-150 times less than anthropogenic [human generated] amounts."
Why does this article refer to volcanos as the "most important" natural source of atmospheric CO2?
Other natural processes shift CO2 molecules around between the atmosphere, the oceans and the global biomass (land and marine organisms and topsoil.) Given enough time to reach equilibrium--which could run to many thousands of years--these processes would have neither a negative or positive carbon footprint. But volcanic processes release CO2 from deep within the earth's mantle, which translates into a positive carbon footprint, exactly like human fossil fuels use--but on a much smaller scale.
The takeaway here is that humans far outweigh volcanos, as far as CO2--the most commonly talked about and single most important driver of global warming.
I have not been able to Google my way to any credible statement that suggests that any of the long list of gases in varying quantities from all the world's volcanos are contributing in any measurable way to global warming.
On the contrary, there's a new report that volcanos have recently been acting like a brake, holding back the speed of global warming, slowing it down by about 25 percent. This is considered to be an effect of volcanic sulfur dioxide (SO2) infiltrating the stratosphere (upper atmosphere) as an aerosol, reflecting solar irradiance away from the earth's surface. Optical instruments have provided data that records that the aerosol content of the stratosphere has increased by about 4 to 7 percent since 2000. But the researchers caution against interpreting these results as a reliable natural antidote to MMGW:
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“The biggest implication here is that scientists need to pay more attention to small and moderate volcanic eruptions when trying to understand changes in Earth’s climate”, said Professor Brian Toon of CU-Boulder’s Department of Atmospheric and Oceanic Sciences.
“But overall these eruptions are not going to counter the greenhouse effect. Emissions of volcanic gases go up and down, helping to cool or heat the planet, while greenhouse gas emissions from human activity [apart from any reductions that might yet be achieved by greenhouse mitigation efforts] just continue to go up.”
[This message has been edited by rinselberg (edited 08-30-2013).]
