"But, in matters of probability, it is not in every case we can be sure that we have all the particulars before us, that any way concern the question; and that there is no evidence behind, and yet unseen, which may cast the probability on the other side, and outweigh all that at present seems to preponderate with us. Who almost is there that hath the leisure, patience, and means to collect together all the proofs concerning most of the opinions he has, so as safely to conclude that he hath a clear and full view; and that there is no more to be alleged for his better information? And yet we are forced to determine ourselves on the one side or other. The conduct of our lives, and the management of our great concerns, will not bear delay: for those depend, for the most part, on the determination of our judgment in points wherein we are not capable of certain and demonstrative knowledge, and wherein it is necessary for us to embrace the one side or the other.
The right use of it, mutual charity and forbearance, in a necessary diversity of opinions. Since, therefore, it is unavoidable to the greatest part of men, if not all, to have several opinions, without certain and indubitable proofs of their truth; and it carries too great an imputation of ignorance, lightness, or folly for men to quit and renounce their former tenets presently upon the offer of an argument which they cannot immediately answer, and show the insufficiency of: it would, methinks, become all men to maintain peace, and the common offices of humanity, and friendship, in the diversity of opinions; since we cannot reasonably expect that any one should readily and obsequiously quit his own opinion, and embrace ours, with a blind resignation to an authority which the understanding of man acknowledges not. For however it may often mistake, it can own no other guide but reason, nor blindly submit to the will and dictates of another. If he you would bring over to your sentiments be one that examines before he assents, you must give him leave at his leisure to go over the account again, and, recalling what is out of his mind, examine all the particulars, to see on which side the advantage lies: and if he will not think our arguments of weight enough to engage him anew in so much pains, it is but what we often do ourselves in the like case; and we should take it amiss if others should prescribe to us what points we should study. And if he be one who takes his opinions upon trust, how can we imagine that he should renounce those tenets which time and custom have so settled in his mind, that he thinks them self-evident, and of an unquestionable certainty; or which he takes to be impressions he has received from God himself, or from men sent by him? How can we expect, I say, that opinions thus settled should be given up to the arguments or authority of a stranger or adversary, especially if there be any suspicion of interest or design, as there never fails to be, where men find themselves ill treated? We should do well to commiserate our mutual ignorance, and endeavour to remove it in all the gentle and fair ways of information; and not instantly treat others ill, as obstinate and perverse, because they will not renounce their own, and receive our opinions, or at least those we would force upon them, when it is more than probable that we are no less obstinate in not embracing some of theirs. For where is the man that has incontestable evidence of the truth of all that he holds, or of the falsehood of all he condemns; or can say that he has examined to the bottom all his own, or other men's opinions? The necessity of believing without knowledge, nay often upon very slight grounds, in this fleeting state of action and blindness we are in, should make us more busy and careful to inform ourselves than constrain others. At least, those who have not thoroughly examined to the bottom all their own tenets, must confess they are unfit to prescribe to others; and are unreasonable in imposing that as truth on other men's belief, which they themselves have not searched into, nor weighed the arguments of probability, on which they should receive or reject it. Those who have fairly and truly examined, and are thereby got past doubt in all the doctrines they profess and govern themselves by, would have a juster pretence to require others to follow them: but these are so few in number, and find so little reason to be magisterial in their opinions, that nothing insolent and imperious is to be expected from them: and there is reason to think, that, if men were better instructed themselves, they would be less imposing on others."
-John Locke, Essay Concerning Human Understanding, Book IV, Ch. XVI, Sec. 3-4
For your self-directed-learning pleasure, a few suggestions:
This thread suggests the best introductory texts on a wide variety of topics: [link]
Five Books-where an expert does an interview and recommends 5 books on a particular subject: [link]
The Lincoln Library of Essential Information-a two volume encyclopedia, organized by subject with further study recommendations and study questions after each section: [link]
You are not so smart-amusing articles on cognitive biases and miscellaneous psychology: [link]
Some 4 years later I’ve finally finished watching every movie in the list of 100 great films compiled by British critic Ronald Bergan, a list I chose because of its wide selection criteria, from the influential and innovative to the popular and critically acclaimed. With a set of films this broad, it’s inevitable that there will be a variety of reactions. Here are a few of my own, in (appropriately) list form. I did a similar list in 2008 when I made it halfway. You can find that list here.
Overrated: Star Wars The Conformist The Chelsea Girls Dr. Strangelove The Maltese Falcon Duck Soup Powerful and heartbreaking: The Passion of Joan of Arc Bicycle Thieves Pather Panchali The 400 Blows Andrei Rublev The Deer Hunter Come and See Shoah
Slow (aka deliberately paced): Paris, Texas L’Avventura Last Year in Marienbad Olympia Napoleon Nosferatu: A Symphony of Terror The Battleship Potemkin
All too accurate: City of God Traffic Unforgiven Taxi Driver The Battle of Algiers In Which We Serve
Gems of black and white: The Cabinet of Dr. Caligari City Lights King Kong The Grapes of Wrath Casablanca Saturday Night and Sunday Morning
Foreign masterpieces: Children of Paradise Rashomon Tokyo Story Three Colors: Blue, White, Red The Seventh Seal
Guaranteed to make you uncomfortable: Blue Velvet An Andalucian Dog Do the Right Thing In the Realm of the Senses The Blue Angel
Just plain enjoyable: Fargo Cinema Paradisio The Godfather The Sound of Music Breathless Some Like it Hot To Be or Not To Be His Girl Friday
Taittaitcha
Wednesday 15 September 2010 - 11:02:03
Lots of talk about Global Warming and Climate Change lately. Here’s my current take on the state of the debate, and the issues at hand. Please note that these are my views from a limited knowledge base. Still, hopefully they may be helpful. Feel free to forward it on.
Issue 1: Is there a current warming trend?
The short answer is a pretty unqualified YES. How do we know? Well, first there is the thermometer record since 1850. For instance, you can go to the NOAA and get surface and ocean temperatures since 1880 (http://www.ncdc.noaa.gov/oa/climate/research/anomalies/index.html ). The Hadley Centre also maintains a global surface temperature dataset (http://www.cru.uea.ac.uk/link/ ). There are two main concerns with these datasets. First, the Heat Island effect (where all the asphalt and buildings in urban centers, where many of the temperatures are taken, raises the local temperature ), and changing accuracy in thermometer design. The second concern is ameliorated by the variety of temperature methods simultaneously used (and thus can be verified for accuracy against each other ). The first concern, the Heat Island effect, is largely calibrated for with sea temperature readings. These readings were taken by ships throughout the globe, and are immune from the Heat Island effects. A rise in average temperature can be seen in these marine records as well as surface land records (see, for instance, [link] as well as [link] ). Another way to calibrate against local trends such as the Heat Island effect is troposphere temperatures. Satellites have been measuring the troposphere temperature since 1979. Balloon measurements begin to show good coverage in the 1950s. The University of Alabama and another group have studied this data and found an upward trend in temperatures.
Issue 2: What about a longer-term trend?
This is answered by other methods of extrapolating the global temperature readings further back in history. Note that these various methods are cross-referenced to verify their levels of accuracy. There are three main methods. Tree rings, isotope variations in ice cores, and coral growth.
Tree ring records go back about as far as 7000 years. They give a good general view of temperatures, and have a larger coverage of areas (due to different populations of trees and fossilized trees used ) versus coral or ice rings. There is an issue, however, with recent ring studies and warming trends not being adequately seen in the tree ring samples. That is, our more accurate methods of temperature recording show more warming than recent tree rings. Note that this is mostly a problem with northern trees, and is not a problem with coral or ice core samples. It’s referred to as the “divergence problem” and no conclusive solution has yet been advanced (see, for example, [link] ).
Ice cores are currently the most fruitful source of historical climate data. As these layers of ice are formed in various cold regions, they condense and trap tiny air bubbles on an annual basis. From Wikipedia: “Many materials can appear in an ice core. Layers can be measured in several ways to identify changes in composition. Small meteorites may be embedded in the ice. Volcanic eruptions leave identifiable ash layers. Dust in the core can be linked to increased desert area or wind speed.
Isotopic analysis of the ice in the core can be linked to temperature and global sea level variations. Analysis of the air contained in bubbles in the ice can reveal the palaeocomposition of the atmosphere, in particular CO2 variations. There are great problems relating the dating of the included bubbles to the dating of the ice, since the bubbles only slowly "close off" after the ice has been deposited. Nonetheless, recent work has tended to show that during deglaciations CO2 increases lags temperature increases by 600 +/- 400 years [9]. Beryllium-10 concentrations are linked to cosmic ray intensity which can be a proxy for solar strength.
There may be an association between atmospheric nitrates in ice and solar activity. However, recently it was discovered that sunlight triggers chemical changes within top levels of firn which significantly alter the pore air composition. This raises levels of formaldehyde and NOx. Although the remaining levels of nitrates may indeed be indicators of solar activity, there is ongoing investigation of resulting and related effects of effects upon ice core data.[10][11]” (http://en.wikipedia.org/wiki/Ice_core )The Vostic ice core records go back as far as 420,000 years. Others go as far as 800,000 years.
I’m not familiar with Coral dating (which has a pretty limited range of reference, anyway ), but here’s the basics: “The annual growth bands in bamboo corals and others allow geologists to construct year-by-year chronologies, a form of incremental dating, which can provide high-resolution records of past climatic and environmental changes using geochemical techniques.[31]
Certain species of corals form communities called microatolls. The vertical growth of microatolls is limited by average tidal height. By analyzing the various growth morphologies, microatolls can be used as a low resolution record of patterns of sea level change. Fossilized microatolls can also be dated using radioactive carbon dating. Such methods have been used to used to reconstruct Holocene sea levels.[32]” (Wikipedia, [link] )
So where does that leave us? Well, the National Research Council gave a good summary in their report on climate of the past 2000 years in response to a request from Congress: “Large-scale surface temperature reconstructions yield a generally consistent picture of temperature trends during the preceding millennium, including relatively warm conditions centered around A.D. 1000 (identified by some as the “Medieval Warm Period” ) and a relatively cold period (or “Little Ice Age” ) centered around 1700. The existence of a Little Ice Age from roughly 1500 to 1850 is supported by a wide variety of evidence including ice cores, tree rings, borehole temperatures, glacier length records, and historical documents. Evidence for regional warmth during medieval times can be found in a diverse but more limited set of records including ice cores, tree rings, marine sediments, and historical sources from Europe and Asia, but the exact timing and duration of warm periods may have varied from region to region, and the magnitude and geographic extent of the warmth are uncertain.” (see [link] )
In short, we can say with some confidence that recent warming trends are higher than at any point since 1600 AD. Prior to that we think it is still warmer than our records show, but there’s uncertainty due to the lack of direct measurements and uncertainties in the accuracy of ice cores, tree rings, etc.
Issue 3: What’s causing the trend?
Okay, now things really start to get tricky. There’s lots of mudslinging around this topic! But we’ll save the issue of scientific “consensus” for another point. For this one, let’s just look at the facts available. First, the different contributors to changes in climate, Greenhouse gases. These include carbon dioxide, methane, nitrous oxide, and CFC-12.
Carbon dioxide levels are shown in our proxy records (good ol ice cores ) to have naturally fluctuated in the past. 500 million years ago CO2 levels were likely 10 times higher than now (see GEOCARB III (Berner and Kothavala 2001 ), COPSE (Bergmann et al. 2004 ) and Rothman (2001 ) ). These CO2 levels also correlate well historically with higher global temperatures. Note that these are vastly different temperatures and environments than at any point in recorded human history. Also note that current CO2 levels greatly exceed any levels found in our ice core records (going back as far as 800,000 years ). Caution on this topic should be maintained, then, rather than reflexively pointing to higher CO2 levels in the past invalidating global warming fears. Isotopic analysis of atmospheric CO2 confirms that fossil fuel burning is the source of most of the CO2 increase, unlike during prior warming periods. (see Schimel, D. (1996 ). CO2 and the carbon cycle, pp.76-86 in Climate Change 1995: The Science of Climate Change. J.T. Houghton, L.G. Meira Filho, B.A. Callander, N. Harris, A. Kattenberg and K. Maskell (eds ), Cambridge University Press 1996. )
Land use is another significant factor in warming trends. Remember the Heat Island problem? Some use it as an attack on temperature records and thus implicitly an attack on global warming, but it is also a great example of land use influencing temperatures. Of course, cities cover a small area of land. But deforestation is a much larger human endeavor. Deforestation both reduces the amount of carbon dioxide absorbed by land no longer covered with CO2 absorbing trees, and releases greenhouse gases directly through the burning of the forests that often accompanies it.
Finally, Livestock production occupies about 30% of the ice-free land surface of the Earth. Methane from livestock is a particularly large greenhouse gas emitted in this way.
Issue 4: But what’s causing the trend? You didn’t really answer…
Okay, now that we know some of the main factors (oh yeah, and there’s a long-term trend in the angle of the earth and orbit, but that’s really slow and subtle, so doesn’t affect us in the short term of a few thousand years ) let’s address the question of what’s causing the trend.
Is it volcanoes? Not in the modern era. There was a colossal volcanic outgassing which raised the CO2 concentration of the atmosphere abruptly to 12%, about 350 times modern levels, causing extreme greenhouse conditions around the Neoproterozoic era (about 500 million years ago. See [link] ). This marked the close of the Precambrian eon, and was succeeded by the warmer Phanerozoic. No volcanic carbon dioxide emission of comparable scale has occurred since. In the modern era, emissions to the atmosphere from volcanoes are only about 1% of emissions from human sources. (see Gerlach, TM (1991 ). "Present-day CO2 emissions from volcanoes". Transactions of the American Geophysical Union 72: 249–55. )
Is it natural sources? This is an important question, because there ARE natural sources, and in any model they play an important role. It is important to note that consensus scientific opinion does not state that ALL warming is caused by human actions. Rather, human activity is having an increasing impact, and feedback loops as well as the human sources added on top of natural sources are all factors. So sayeth Wikipedia: “Natural sources of carbon dioxide are more than 20 times greater than sources due to human activity,[22] but over periods longer than a few years natural sources are closely balanced by natural sinks such as weathering of continental rocks and photosynthesis of carbon compounds by plants and marine plankton. As a result of this balance, the atmospheric concentration of carbon dioxide remained between 260 and 280 parts per million for the 10,000 years between the end of the last glacial maximum and the start of the industrial era.” (http://en.wikipedia.org/wiki/Greenhouse_gas )
Anyway, let’s get back to CO2 levels. And also back to those ice cores. Levels in recent history have been pretty steady. Atmospheric CO2 levels were about 280 parts per million by volume (ppmv ), and stayed between 260 and 280 during the preceding ten thousand years. (Flückiger, Jacqueline (2002 ). "High-resolution Holocene N2O ice core record and its relationship with CH4 and CO2". Global Biogeochemical Cycles 16: 1010 ).
And after the industrial revolution? Things have changed, a lot. For example, the concentration of carbon dioxide has increased by about 36% to 380 ppmv. The interesting thing here is that the first 50 ppmv increase happened over the course of about 200 years. The second 50 ppmv? That happened in just 33 years. Recent data suggests that the rate of increase in the 1960s is only 37% of what it was from 2000-2007. (for the datasets, go to [link] ). Methane has also increased about 67% over pre-industrial levels (that is, levels pre 1750 AD ), and Nitrous oxide has increased by about 17%.
Issue 5: So, is it people?
Most scientists think so. For example: The attribution of climate change is discussed extensively, with references to peer-reviewed research, in chapter 12 of the IPCC TAR, which discusses The Meaning of Detection and Attribution, Quantitative Comparison of Observed and Modelled Climate Change, Pattern Correlation Methods and Optimal Fingerprint Methods.
An essay in Science surveyed 928 abstracts related to climate change, and concluded that most journal reports accepted the consensus.
A 2002 paper in the Journal of Geophysical Research says "Our analysis suggests that the early twentieth century warming can best be explained by a combination of warming due to increases in greenhouse gases and natural forcing, some cooling due to other anthropogenic forcings, and a substantial, but not implausible, contribution from internal variability. In the second half of the century we find that the warming is largely caused by changes in greenhouse gases, with changes in sulphates and, perhaps, volcanic aerosol offsetting approximately one third of the warming."
In 1996, in a paper in Nature titled "A search for human influences on the thermal structure of the atmosphere", Benjamin D. Santer et al. wrote: "The observed spatial patterns of temperature change in the free atmosphere from 1963 to 1987 are similar to those predicted by state-of-the-art climate models incorporating various combinations of changes in carbon dioxide, anthropogenic sulphate aerosol and stratospheric ozone concentrations. The degree of pattern similarity between models and observations increases through this period. It is likely that this trend is partially due to human activities, although many uncertainties remain, particularly relating to estimates of natural variability."
Some scientists noted for their somewhat skeptical view of global warming accept that recent climate change is mostly anthropogenic. John Christy has said that he supports the American Geophysical Union (AGU ) declaration, and is convinced that human activities are the major cause of the global warming that has been measured.
Some scientists do disagree with the consensus: see list of scientists opposing global warming consensus. For example Willie Soon and Richard Lindzen[26] say that there is insufficient proof for anthropogenic attribution. Generally this position requires new physical mechanisms to explain the observed warming; for example "Climate hypersensitivity to solar forcing?", Soon W et al., 2000, Annales Geophysicae-Atmospheres Hydrospheres and Space Sciences 18(5 ): full text. To talk more about these alternate explanations of warming, see my attached earlier letter below. I address several of the main alternative theories.
Also of note: In recent years some skeptics have changed their positions regarding global warming. Ronald Bailey, author of Global Warming and Other Eco-Myths (published by the Competitive Enterprise Institute in 2002 ), stated in 2005, "Anyone still holding onto the idea that there is no global warming ought to hang it up".[170] By 2007, he wrote "Details like sea level rise will continue to be debated by researchers, but if the debate over whether or not humanity is contributing to global warming wasn't over before, it is now.... as the new IPCC Summary makes clear, climate change Pollyannaism is no longer looking very tenable".[171] Gregg Easterbrook characterized himself as having "a long record of opposing alarmism". In 2006, he stated, "based on the data I'm now switching sides regarding global warming, from skeptic to convert".[183] Issue 6: But is the CO2 correlation reliable?
Wikipedia has this to say on the topic, which is a common criticism leveled against Al Gore’s An Inconvenient Truth: “Factors other than increased CO2 concentrations can initiate warming or cooling episodes (see, e.g., orbital forcing ). The ice core record shows that on some occasions temperature starts rising hundreds of years before CO2 increases.[clarification needed][27][28] Such results confirm that the relationship between CO2 and climate can go in both directions: changes in CO2 concentrations affect climate, while changes in climate can affect CO2 concentrations. One proposed mechanism for this effect is increased release of sequestered CO2 from oceans as circulation patterns shift, perhaps abruptly, in response to climate change.[29][30]
A more speculative and polemical inference sometimes drawn is that the causal relationship between temperature rises and global CO2 concentrations is only one-way, so that historical increases in CO2 have been nothing more than the product of independently rising temperatures.[31] However, a strictly "one-way" view of the relationship between CO2 and temperature contradicts basic results in physics, specifically the fact that the absorption and emission of infrared radiation by CO2 increases as its atmospheric concentration increases.[32][33]
First principles as well as empirical observation suggest that positive feedbacks from CO2 concentrations amplify warming initially caused by other factors:
Close analysis of the relationship between the two curves [i] shows that, within the uncertainties of matching their timescales, the temperature led by a few centuries. This is expected, since it was changes in the Earth’s orbital parameters (including the shape of its orbit around the Sun, and the tilt of Earth’s axis ) that caused the small initial temperature rise. This then raised atmospheric CO2 levels, in part by outgassing from the oceans, causing the temperature to rise further. By amplifying each other’s response, this "positive feedback" can turn a small initial perturbation into a large climate change. There is therefore no surprise that the temperature and CO2 rose in parallel, with the temperature initially in advance. In the current case, the situation is different, because human actions are raising the CO2 level, and we are starting to observe the temperature response.[34]
Present CO2 levels greatly exceed the range found in the ice core data. Isotopic analysis of atmospheric CO2 confirms that fossil fuel burning is the source of most of the CO2 increase, unlike during prior interglacial periods.[35] As noted above, models that include increased CO2 levels when simulating recent climate match the observed data far better than those that do not.[2]” Issue 7: Okay, but what about the lying scientists?
Ah yes, you mean the leaked documents last year, right? That was the more than 1,000 e-mails, 2,000 documents, and commented source code, on climate change research covering a period from 1996 until 2009.
Well, it’s going to take a bit of time for that dust storm to settle. One independent panel that is assessing the allegations from the leaked documents is the Independent Climate Change Email Inquiry (http://www.cce-review.org ). It will release it’s findings around spring 2010.
A good Q&A article on the subject from the BBC: [link]
Whiew! A lot of ground covered, and still more to go. For instance, the Hockey Stick graph controversy:
The political significance of the scientific controversy over the graph centers on its use as part of the evidence for anthropogenic global warming. The MBH98 reconstruction was prominently featured in the 2001 United Nations Intergovernmental Panel on Climate Change (IPCC ) Third Assessment Report (TAR ) and as a result has been widely published in the media.
This dispute centered on technical aspects of the methodology and data sets used in creating the MBH98 reconstruction, originally raised by Stephen McIntyre and Ross McKitrick.[1] Their criticisms were that Mann et al.'s reconstructed millennial temperature graph (the hockey stick ) was an artifact of flawed calculations and serious data defects; in turn, MBH replied that these criticisms were spurious. ... One point of contention relates to McIntyre's requests for Mann to provide him with the data, methods and source code McIntyre needed to audit MBH98.[21] Mann provided some data and then stopped. After a long process - in which the National Science Foundation supported Mann - the code was made publicly available [22]. It happened because Congress investigated after an article in the Wall Street Journal [23] detailed criticisms raised by McIntyre.[24] Congress was especially concerned about Mann’s reported refusal to provide data. In June 2005, Congress asked Mann to testify before a special subcommittee. The chairman of the committee (Joe Barton, a prominent global warming denialist ) wrote a letter to Mann requesting he provide his data, including his source code, archives of all data for all of Mann's scientific publications, identities of his present and past scientific collaborators, and details of all funding for any of Mann's ongoing or prior research, including all of the supporting forms and agreements.[23] The American Association for the Advancement of Science viewed this as "a search for some basis on which to discredit these particular scientists and findings, rather than a search for understanding."[25] When Mann complied, all of the data was available for McIntyre. Congress also requested that third party science panels review the criticisms by McIntyre and McKitrick. The Wegman Panel [26] and the National Academy of Sciences [27] both published reports. McIntyre and McKitrick (2005 ) claim that 7 of their 10 findings in 2003 have been largely confirmed by these reviews.[28] Nature reported it as "Academy affirms hockey-stick graph - But it criticizes the way the controversial climate result was used." [29]
Well, there’s much to talk about and much unsettled, but hopefully this has given a decent introduction to some of the main issues at hand. Combined with my previous comments below, hopefully it can serve as a decent introduction (if far from complete ).
To complement this, here’s an older summary on the issue of Global Warming I compiled:
It's true that there are lots of issues where there are multiple points of view. Pretty much anything where people have a vested stake in the outcome will have several different views of what's going on. In part, I'd say it's because the world is much less fact-based than we'd like (or are inclined ) to believe. But that gets rather into philosophy.
The nice thing about global warming is that a large part of it is basically fact-based. Is global warming happening or not? I think by now we're in agreement that it is indeed happening? Recorded data is pretty reliable on this point. It may also be noted that, "With the July 2007 release of the revised statement by the American Association of Petroleum Geologists, no remaining scientific body of national or international standing is known to reject the basic findings of human influence on recent climate."
Also, on that topic is the idea of the Urban Heat effect (I've edited this quote a bit ): "Skeptics contend that stations located in more populated areas could show warming due to increased heat generated by cities, rather than a global temperature rise. The IPCC Third Assessment Report acknowledges that the urban heat island is an important local effect, but cites analyses of historical data indicating that the effect of the urban heat island on the global temperature trend is no more than 0.05 °C (0.09 °F ) degrees through 1990.[102] More recently, Peterson (2003 ) found no difference between the warming observed in urban and rural areas.[103] ...
Parker (2006 ) found that there was no difference in warming between calm and windy nights. Since the urban heat island effect is strongest for calm nights and is weak or absent on windy nights, this was taken as evidence that global temperature trends are not significantly contaminated by urban effects.[105] Pielke and Matsui published a paper disagreeing with Parker's conclusions.(Stephen McIntyre analyzed Peterson's raw data. He claimed to find "actual cities have a very substantial trend of over 2 °C per century relative to the rural network - and this assumes that there are no problems with rural network - something that is obviously not true since there are undoubtedly microsite and other problems."[104] McIntyre has not published his results in a peer-reviewed journal. )[106]"
But there is the non-fact-based part of global warming, which goes to causes. We cannot say for certain what causes warming on a global scale because we cannot isolate the factors. We can't just stop the volcanoes from erupting, or people from driving, or sunspots from forming, and see what happens. So, all of these things get a bit mixed up, and people take the conclusions from the observed data that they'd like to.
The issue is far from a lost cause, however, because there really aren't that many plausible explanations of global warming, and the longer we study the issue the more evidence we get concerning it.
So, what are the possible causes of global warming?
1) Greenhouse gasses 2) Natural Variation 3) Solar cycles 4) Ocean currents 5) Cosmic Rays 6) Unknown/Other 7) Combination of these factors
Let's look at number 3. The idea that increased solar activity was the cause of global warming came a couple of years ago, and was based on a recorded increase in the solar activity observed. Later observations have disproven this to be a major factor. Also, it may be noted that we now observe the sun to be once again cooling (as it does on 11 year cycles ), but global warming continues unabated. As the NASA Goddard Institute for Space Studies (GISS ) press release says, "...the solar increases do not have the ability to cause large global temperature increases...greenhouse gases are indeed playing the dominant role..." The Sun is once again less bright as we approach solar minimum, yet global warming continues. This is a nice one to disprove because we can successfully isolate it's impact. It lessens, but global warming continues. Hence, not a major factor.
Okay, number 4. This is advocated by a Hurricane scientist named William Grey. He's a bit of a difficult subject, because he's very well respected in hurricane circles (where he made many contributions ) but has been somewhat ostracized from mainstream circles by his views on the causes of global warming and his analysis of where they come from (he's said that the support from global warming comes from scientists afraid of losing funding, and is pushed by governments and environmentalists who want a global government ). He agrees that global warming is happening, but attributes most of it to ocean currents (his assertions have yet to be published in any peer-reviewed journals ). He also attacks Al Gore's assertion in his movie that increased hurricane activity is due to global warming. Here I think we can definitely believe him, as he has supplied considerable evidence that there is not a good direct link between ocean temperatures and hurricane formation. Furthermore, good analysis of the hurricane trends does not show an increase in hurricane activity. Many other scientists have also backed his assertion about hurricanes. A problem with Grey is that he's rather old, and seems to have a very negative view of the methods of modern scientists using computer models on principle. Also, Grey predicted in 2006 that there would be global cooling by 2009-10, and that at that point, the whole hysteria would be seen for the hoax it is. It will be interesting to see if his prediction comes true.
Number 5. The idea is that cosmic rays affect cloud formation, and thus affect global temperatures. Henrik Svensmark advocates this view. The delightful thing about this is that many scientists are currently working to verify his thesis. "Preliminary experimental verification has been conducted in the SKY Experiment at the Danish National Space Science Center. CERN, the European Organization for Nuclear Research in Geneva, is preparing comprehensive verification in the CLOUD Project." So, we'll be able to see for sure. A number of scientists up to this point have found very little correlation between cosmic ray activity and cloud formation. Svensmark has said he has replies to these studies, but they have not yet been published in any peer-reviewed journals.
Number 2. This goes along with number 6, and basically says that "we've seen temperature cycles in the past, and this is just another one." The most popular citation is from Gerard C. Bond, who suggested a 1500 year temperature cycle based on ice core samples. Unfortunately for many who have jumped on this cycle, Bond himself stresses that he does not believe the existence of this cycle in any way casts doubt on the current human caused global warming.
Number one is of course the main issue of contention, but here's a good summary on the subject. First, though, I might note that it is very clear that the increase in CO2 is not from natural sources (ie, volcanoes, oceans, etc ). This is important because some have accepted that the greenhouse gases are having an effect, but that they come from natural sources, and are thus the result of "natural" factors or cycles.("Analysis of carbon isotopes in atmospheric CO2 shows that the recent observed CO2 increase cannot have come from the oceans, volcanoes, or the biosphere" ): Okay, on to the summary: "
Over the past 150 years human activities have released increasing quantities of greenhouse gases into the atmosphere. This has led to increases in mean global temperature, or global warming. Other human effects are relevant—for example, sulphate aerosols are believed to lead to cooling—and natural factors also contribute. According to the historical temperature record of the last century, the Earth's near-surface air temperature has risen around 0.74 ± 0.18 °Celsius (1.3 ± 0.32 °Fahrenheit ).
A historically important question in climate change research has regarded the relative importance of human activity and non-anthropogenic causes during the period of instrumental record. In the 1995 Second Assessment Report (SAR ), the IPCC made the widely-quoted statement that "The balance of evidence suggests a discernible human influence on global climate". The phrase "balance of evidence" suggested the (English ) common-law standard of proof required in civil as opposed to criminal courts: not as high as "beyond reasonable doubt". In 2001 the Third Assessment Report (TAR ) refined this, saying "There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities".[9] The 2007 fourth assessment report (WG1 AR4 ) strengthened this finding:
"Anthropogenic warming of the climate system is widespread and can be detected in temperature observations taken at the surface, in the free atmosphere and in the oceans. Evidence of the effect of external influences, both anthropogenic and natural, on the climate system has continued to accumulate since the TAR."[5]
Over the past five decades there has been a global warming of approximately 0.65 °C (1.17 °F ) at the Earth's surface (see historical temperature record ). Among the possible factors that could produce changes in global mean temperature are internal variability of the climate system, external forcing, an increase in concentration of greenhouse gases, or any combination of these. Current studies indicate that the increase in greenhouse gases, most notably CO2, is mostly responsible for the observed warming. Evidence for this conclusion includes:
Estimates of internal variability from climate models, and reconstructions of past temperatures, indicate that the warming is unlikely to be entirely natural. Climate models forced by natural factors and increased greenhouse gases and aerosols reproduce the observed global temperature changes; those forced by natural factors alone do not[10]. "Fingerprint" methods indicate that the pattern of change is closer to that expected from greenhouse gas-forced change than from natural change.[11] The plateau in warming from the 1940s to 1960s can be attributed largely to sulphate aerosol cooling.[12]
In 2001, the U.S. National Academy of Sciences released a report supporting the IPCC's conclusions regarding the causes of recent climate change. It stated, "Greenhouse gases are accumulating in Earth's atmosphere as a result of human activities, causing surface air temperatures and subsurface ocean temperatures to rise. Temperatures are, in fact, rising. The changes observed over the last several decades are likely mostly due to human activities, but we cannot rule out that some significant part of these changes are also a reflection of natural variability."[13][14][15]"
Okay, last of all, the issue of funding in influencing scientists.
Well, there are three things we can look at. First, funding. On the one and, there are the big oil companies which have put money into the issue:
"The Union of Concerned Scientists have produced a report titled 'Smoke, Mirrors & Hot Air',[174] that criticizes ExxonMobil for "underwriting the most sophisticated and most successful disinformation campaign since the tobacco industry" and for "funneling about $16 million between 1998 and 2005 to a network of ideological and advocacy organizations that manufacture uncertainty on the issue." In 2006 Exxon claimed that it was no longer going to fund these groups[175] though that claim has been challenged by Greenpeace.[176]"
That 16 million funded such global warming skeptics as Fred Singer, Fred Seitz, and Patrick Michaels.
On the other hand, there is the funding that comes from governments. This, however, has had fewer examples to show.
"Richard Lindzen, the Alfred P. Sloan Professor of Meteorology at MIT, makes the specific claim that "[in] the winter of 1989 Reginald Newell, a professor of meteorology [at MIT], lost National Science Foundation funding for data analysis that were failing to show net warming over the past century." Lindzen also suggests four other scientists "apparently" lost their funding or positions after questioning the scientific underpinnings of global warming.[183] Lindzen himself, however, has been the recipient of money from energy interests such as OPEC and the Western Fuels Association, including "$2,500 a day for his consulting services",[184] as well as funding from federal sources including the National Science Foundation, the Department of Energy, and NASA.[185]"
A few other scientists besides Lindzen, however, have made similar claims. This doesn't square very well with the following, however:
"A survey of climate scientists which was reported to the US House Oversight and Government Reform Committee noted that "Nearly half of all respondents perceived or personally experienced pressure to eliminate the words 'climate change', 'global warming' or other similar terms from a variety of communications." These scientists were pressured to tailor their reports on global warming to fit the Bush administration's climate change skepticism. In some cases, this occurred at the request of a former oil-industry lobbyist.[208]. In a report by NASA's Office of the Inspector General it has been revealed that NASA officials censored and suppressed scientific data on global warming in order protect the Bush administration from controversy close to the 2004 presidential election[209]."
In other words, there is much more evidence that scientists have been suppressed in their findings for global warming, than that they have been suppressed for not finding it. However, it may be admitted that both cases could be true at the same time.
I recently did some sketches for a work related project. For inexplicable reasons, some of those sketches involved the characters from twilight. Behold the fruit of my labor!
On the Degrees of Assent
Tuesday 15 November 2011 - 13:36:26
