On simple explanations

Clever Connolley caught me out with a comment here on simple explanations. Mencken says that the reason for the 'inferior man' hating knowledge is because it is complex. All superstition is a short cut to make the unintelligible simple. Connolley, apparently agreeing with Mencken, chides me for wanting a simple explanation for global warming.

But is Mencken right? The appeal of true scientific explanation generally does lie in its simplicity. There are obvious exceptions - the proof of the four colour theorem for example. But consider the explanation of an eclipse. That is pretty simple. The moon goes round the earth, the earth goes round the sun. The sun lights up the earth. Occasionally the moon gets in the way and casts a shadow. How simpler could it get? The theory that the eclipse is caused by a dragon crossing the sun, by contrast, requires a theory of dragons, and no theory of dragons - at least not one that gives a comprehensive treatment of them, including their metabolism, genetic structure etc - could be simple at all.
 
Or consider Augustine's explanation of why evil exists:

That the whole human race has been condemned in its first origin, this life itself, if life it is to be called, bears witness by the host of cruel ills with which it is filled. Is not this proved by the profound and dreadful ignorance which produces all the errors that enfold the children of Adam, and from which no man can be delivered without toil, pain, and fear? Is it not proved by his love of so many vain and hurtful things, which produces gnawing cares, disquiet, griefs, fears, wild joys, quarrels, lawsuits, wars, treasons, angers, hatreds, deceit, flattery, fraud, theft, robbery, perfidy, pride, ambition, envy, murders, parricides, cruelty, ferocity, wickedness, luxury, insolence, impudence, shamelessness, fornications, adulteries, incests, and the numberless uncleannesses and unnatural acts of both sexes, which it is shameful so much as to mention; sacrileges, heresies, blasphemies, perjuries, oppression of the innocent, calumnies, plots, falsehoods, false witnessings, unrighteous judgments, violent deeds, plunderings, and whatever similar wickedness has found its way into the lives of men, though it cannot find its way into the conception of pure minds? (City of God, Book 22 chapter 22)

The explanation - that Adam and Eve offended God, and that these evils are a punishment - appears simple at first sight, just like the dragon explanation.  But it is not, for it requires a theory of God, and also a theory of Paradise, which is problematic.  Sociobiology could probably provide a simpler one (although I'm not sure it has, yet).

Superstition is not necessarily a simpler theory. So, what distinguishes superstition from science?

165 objections to global warming

I just found this handy guide to sceptical arguments against ‘global warming’. There are 165 arguments in all, organised in order of supposed popularity or frequency.

I ignored this ordering and – because this is merely a logic blog – reclassified them by type of argument. In logical order, they are as follows. ‘Wrong effect’ is the objection that there is no warming, or that the observational data do not support the thesis that any such warming is statistically significant. ‘Wrong methodology’ is the negative claim that the evidence does not support the presumed causal relationship between greenhouse emissions and warming. ‘Wrong cause’ is the positive claim that, although warming is conceded, the cause is different from the standard one (i.e. greenhouse effect caused by industrialisation). ‘Lack of authority’ is the objection that there is no real scientific consensus about warming, or the cause-effect relationship. ‘Wrong consequence’ concedes the warming, and the causal relationship, but denies any real consequences. Finally, ‘We can’t prevent it’ concedes absolutely everything – disastrous consequences and all – but says there is no point in doing anything, because nothing would be effective anyway.

I will discuss these arguments in later posts, but my point for today is that none of these objections hit my sceptical worry about the global warming hypothesis (which I have defined as the hypothesis that greenhouse emissions will have potentially disastrous consequences for the world). The claim that ‘we can’t prevent it’ is not part of the hypothesis. The objection about scientific consensus is a form of ad hominem, which is a logical fallacy (although looking for agreement among experts is a useful heuristic to guide non-experts, and is the basis of most peer-review processes, and the underlying reason for examinations and qualifications and suchlike). Positive claims of ‘wrong cause’ are a form of straw man, and are also not properly sceptical (a sceptic avoids making any positive claim, preferring to question or express reasonable doubt). When replying to an argument, we must demonstrate what is wrong with the argument itself, or what is wrong with the premisses. Merely contradicting the conclusion, even for good reason, is not enough. That leaves ‘wrong effect’, ‘wrong methodology’ and ‘wrong consequence’, which I will discuss tomorrow.

Meanwhile, as a preliminary, you may want to revisit our old friends propter quid and quia, in particular, and more generally the posts about Aristotle’s Posterior Analytics.

Wrong effect (56)
142 "It warmed just as fast in 1860-1880 and 1910-1940" The warming trend over 1970 to 2001 is greater than warming from both 1860 to 1880 and 1910 to 1940.
21 "1934 - hottest year on record" 1934 was one of the hottest years in the US, not globally.
17 "Glaciers are growing" Most glaciers are retreating, posing a serious problem for millions who rely on glaciers for water.
9 "It hasn't warmed since 1998" For global records, 2010 is the hottest year on record, tied with 2005.
10 "Antarctica is gaining ice" Satellites measure Antarctica losing land ice at an accelerating rate.
7 "Temp record is unreliable" The warming trend is the same in rural and urban areas, measured by thermometers and satellites.
1 "Climate's changed before" Climate reacts to whatever forces it to change at the time; humans are now the dominant forcing.
4 "It's cooling" The last decade 2000-2009 was the hottest on record.
15 "Hockey stick is broken" Recent studies agree that recent global temperatures are unprecedented in the last 1000 years.
23 "It's freaking cold!" A local cold day has nothing to do with the long-term trend of increasing global temperatures.
25 "Sea level rise is exaggerated" A variety of different measurements find steadily rising sea levels over the past century.
26 "It's Urban Heat Island effect" Urban and rural regions show the same warming trend.
28 "Arctic icemelt is a natural cycle" Thick arctic sea ice is undergoing a rapid retreat.
30 "Medieval Warm Period was warmer" Globally averaged temperature now is higher than global temperature in medieval times.
31 "It's a 1500 year cycle" Ancient natural cycles are irrelevant for attributing recent global warming to humans.
85 "Record snowfall disproves global warming" Warming leads to increased evaporation and precipitation, which falls as increased snow in winter.
144 "Antarctica is too cold to lose ice" Glaciers are sliding faster into the ocean because ice shelves are thinning due to warming oceans.
164 "Ljungqvist broke the hockey stick" Ljungqvist's temperature reconstruction is very similar to other reconstructions by Moberg and Mann.
152 "DMI show cooling Arctic" While summer maximums have showed little trend, the annual average Arctic temperature has risen sharply in recent decades.
151 "Greenland has only lost a tiny fraction of its ice mass" Greenland's ice loss is accelerating & will add metres of sea level rise in upcoming centuries.
139 "Record high snow cover was set in winter 2008/2009" Winter snow cover in 2008/2009 was average while the long-term trend in spring, summer, and annual snow cover is rapid decline.
140 "Sea level is not rising" The claim sea level isn’t rising is based on blatantly doctored graphs contradicted by observations.
135 "The sun is getting hotter" The sun has just had the deepest solar minimum in 100 years.
125 "Ice Sheet losses are overestimated" A number of independent measurements find extensive ice loss from Antarctica and Greenland.
120 "IPCC ‘disappeared’ the Medieval Warm Period" The IPCC simply updated their temperature history graphs to show the best data available at the time.
114 "Earth hasn't warmed as much as expected" This argument ignores the cooling effect of aerosols and the planet's thermal inertia.
115 "Sea level rise is decelerating" Global sea level data shows that sea level rise has been increasing since 1880 while future sea level rise predictions are based on physics, not statistics.
113 "Ice isn't melting" Arctic sea ice has shrunk by an area equal to Western Australia, and summer or multi-year sea ice might be all gone within a decade.
110 "Arctic sea ice loss is matched by Antarctic sea ice gain" Arctic sea ice loss is three times greater than Antarctic sea ice gain.
99 "Dropped stations introduce warming bias" If the dropped stations had been kept, the temperature would actually be slightly higher.
96 "Tree-rings diverge from temperature after 1960" This is a detail that is complex, local, and irrelevant to the observed global warming trend.
91 "Southern sea ice is increasing" Antarctic sea ice has grown in recent decades despite the Southern Ocean warming at the same time.
92 "IPCC overestimate temperature rise" Monckton used the IPCC equation in an inappropriate manner.
93 "It's microsite influences" Microsite influences on temperature changes are minimal; good and bad sites show the same trend.
90 "Arctic was warmer in 1940" The actual data show high northern latitudes are warmer today than in 1940.
81 "Global warming stopped in 1998, 1995, 2002, 2007, 2010, ????" Global temperature is still rising and 2010 was the hottest recorded.
77 "Springs aren't advancing" Hundreds of flowers across the UK are flowering earlier now than any time in 250 years.
63 "It's the ocean" The oceans are warming and moreover are becoming more acidic, threatening the food chain.
61 "IPCC were wrong about Himalayan glaciers" Glaciers are in rapid retreat worldwide, despite 1 error in 1 paragraph in a 1000 page IPCC report.
49 "It warmed before 1940 when CO2 was low" Early 20th century warming is due to several causes, including rising CO2.
50 "Satellites show no warming in the troposphere" The most recent satellite data show that the earth as a whole is warming.
43 "Arctic sea ice has recovered" Thick arctic sea ice is in rapid retreat.
32 "Oceans are cooling" The most recent ocean measurements show consistent warming.
128 "Satellite error inflated Great Lakes temperatures" Temperature errors in the Great Lakes region are not used in any global temperature records.
41 "There's no empirical evidence" There are multiple lines of direct observations that humans are causing global warming.
36 "Greenland was green" Other parts of the earth got colder when Greenland got warmer.
37 "Greenland is gaining ice" Greenland on the whole is losing ice, as confirmed by satellite measurement.
38 "Polar bear numbers are increasing" Polar bears are in danger of extinction as well as many other species.
39 "It's not happening" There are many lines of evidence indicating global warming is unequivocal.
46 "It cooled mid-century" Mid-century cooling involved aerosols and is irrelevant for recent global warming.
44 "We're coming out of the Little Ice Age" Scientists have determined that the factors which caused the Little Ice Age cooling are not currently causing global warming
54 "Mt. Kilimanjaro's ice loss is due to land use" Most glaciers are in rapid retreat worldwide, notwithstanding a few complicated cases.
55 "There's no tropospheric hot spot" We see a clear "short-term hot spot" - there's various evidence for a "long-term hot spot".
56 "2009-2010 winter saw record cold spells" A cold day in Chicago in winter has nothing to do with the trend of global warming.
141 "We're heading into cooling" There is no scientific basis for claims that the planet will begin to cool in the near future.
13 "We're heading into an ice age" Worry about global warming impacts in the next 100 years, not an ice age in over 10,000 years.

Wrong methodology (5)
58 "Scientists can't even predict weather" Weather and climate are different; climate predictions do not need weather detail.
123 "Climate is chaotic and cannot be predicted" Weather is chaotic but climate is driven by Earth's energy imbalance, which is more predictable.
131 "Soares finds lack of correlation between CO2 and temperature" Soares looks at short-term trends which are swamped by natural variations while ignoring the long-term correlation.
82 "The science isn't settled" That human CO2 is causing global warming is known with high certainty & confirmed by observations.
6 "Models are unreliable" Models successfully reproduce temperatures since 1900 globally, by land, in the air and the ocean.

Wrong cause (60)
65 "It's not us" Multiple sets of independent observations find a human fingerprint on climate change.
68 "CO2 effect is saturated" Direct measurements find that rising CO2 is trapping more heat.
70 "Clouds provide negative feedback" Evidence is building that net cloud feedback is likely positive and unlikely to be strongly negative.
71 "Volcanoes emit more CO2 than humans" Humans emit 100 times more CO2 than volcanoes.
124 "Melting ice isn't warming the Arctic" Melting ice leads to more sunlight being absorbed by water, thus heating the Arctic.
157 "It's internal variability" Internal variability can only account for small amounts of warming and cooling over periods of decades, and scientific studies have consistently shown that it cannot account for the global warming over the past century.
2 "It's the sun" In the last 35 years of global warming, sun and climate have been going in opposite directions
20 "It's cosmic rays" Cosmic rays show no trend over the last 30 years & have had little impact on recent global warming.
24 "Extreme weather isn't caused by global warming" Extreme weather events are being made more frequent and worse by global warming.
94 "CO2 is not the only driver of climate" Theory, models and direct measurement confirm CO2 is currently the main driver of climate change.
95 "It's albedo" Albedo change in the Arctic, due to receding ice, is increasing global warming.
79 "It's land use" Land use plays a minor role in climate change, although carbon sequestration may help to mitigate.
89 "Solar Cycle Length proves its the sun" The sun has not warmed since 1970 and so cannot be driving global warming.
107 "It's a climate regime shift" There is no evidence that climate has chaotic “regimes” on a long-term basis.
112 "Solar cycles cause global warming" Over recent decades, the sun has been slightly cooling & is irrelevant to recent global warming.
137 "It's waste heat" Greenhouse warming is adding 100 times more heat to the climate than waste heat.
159 "It's satellite microwave transmissions" Satellite transmissions are extremely small and irrelevant.
161 "CO2 only causes 35% of global warming" CO2 and corresponding water vapor feedback are the biggest cause of global warming.
162 "We didn't have global warming during the Industrial Revolution" CO2 emissions were much smaller 100 years ago.
156 "CO2 limits won't cool the planet" CO2 limits won't cool the planet, but they can make the difference between continued accelerating global warming to catastrophic levels vs. slowing and eventually stopping the warming at hopefully safe levels
136 "Mauna Loa is a volcano" The global trend is calculated from hundreds of CO2 measuring stations and confirmed by satellites.
149 "Warming causes CO2 rise" Recent warming is due to rising CO2.
33 "Human CO2 is a tiny % of CO2 emissions" The natural cycle adds and removes CO2 to keep a balance; humans add extra CO2 without removing any.
34 "Water vapor is the most powerful greenhouse gas" Rising CO2 increases atmospheric water vapor, which makes global warming much worse.
51 "CO2 was higher in the past" When CO2 was higher in the past, the sun was cooler.
126 "A drop in volcanic activity caused warming" Volcanoes have had no warming effect in recent global warming - if anything, a cooling effect.
129 "Breathing contributes to CO2 buildup" By breathing out, we are simply returning to the air the same CO2 that was there to begin with.
47 "There's no correlation between CO2 and temperature" There is long-term correlation between CO2 and global temperature; other effects are short-term.
84 "CO2 is not increasing" CO2 is increasing rapidly, and is reaching levels not seen on the earth for millions of years.
86 "CO2 is coming from the ocean" The ocean is absorbing massive amounts of CO2, and is becoming more acidic as a result.
45 "CO2 is not a pollutant" Through its impacts on the climate, CO2 presents a danger to public health and welfare, and thus qualifies as an air pollutant
145 "Water levels correlate with sunspots" This detail is irrelevant to the observation of global warming caused by humans.
146 "CO2 was higher in the late Ordovician" The sun was much cooler during the Ordovician.
147 "It's CFCs" CFCs contribute at a small level.
57 "It's Pacific Decadal Oscillation" The PDO shows no trend, and therefore the PDO is not responsible for the trend of global warming.
59 "It's a natural cycle" No known natural forcing fits the fingerprints of observed warming except anthropogenic greenhouse gases.
73 "It's methane" Methane plays a minor role in global warming but could get much worse if permafrost starts to melt.
100 "Humans are too insignificant to affect global climate" Humans are small but powerful, and human CO2 emissions are causing global warming.
29 "Increasing CO2 has little to no effect" The strong CO2 effect has been observed by many different measurements.
143 "Venus doesn't have a runaway greenhouse effect" Venus very likely underwent a runaway or ‘moist’ greenhouse phase earlier in its history, and today is kept hot by a dense CO2 atmosphere.
133 "Water vapor in the stratosphere stopped global warming" This possibility just means that future global warming could be even worse.
134 "CO2 emissions do not correlate with CO2 concentration" That humans are causing the rise in atmospheric CO2 is confirmed by multiple isotopic analyses.
75 "Humidity is falling" Multiple lines of independent evidence indicate humidity is rising and provides positive feedback.
52 "It's aerosols" Aerosols have been masking global warming, which would be worse otherwise.
97 "It's soot" Soot stays in the atmosphere for days to weeks; carbon dioxide causes warming for centuries.
103 "It's global brightening" This is a complex aerosol effect with unclear temperature significance.
119 "It's ozone" Ozone has only a small effect.
53 "It's El Niño" El Nino has no trend and so is not responsible for the trend of global warming.
40 "Other planets are warming" Mars and Jupiter are not warming, and anyway the sun has recently been cooling slightly.
88 "Pluto is warming" And the sun has been recently cooling.
27 "Mars is warming" Mars is not warming globally.
76 "Neptune is warming" And the sun is cooling.
78 "Jupiter is warming" Jupiter is not warming, and anyway the sun is cooling.
80 "CO2 measurements are suspect" CO2 levels are measured by hundreds of stations across the globe, all reporting the same trend.
74 "CO2 has a short residence time" Excess CO2 from human emissions has a long residence time of over 100 years
12 "CO2 lags temperature" CO2 didn't initiate warming from past ice ages but it did amplify the warming.
154 "Positive feedback means runaway warming" Positive feedback won't lead to runaway warming; diminishing returns on feedback cycles limit the amplification.
18 "Climate sensitivity is low" Net positive feedback is confirmed by many different lines of evidence.
60 "2nd law of thermodynamics contradicts greenhouse theory" The 2nd law of thermodynamics is consistent with the greenhouse effect which is directly observed.
72 "Greenhouse effect has been falsified" The greenhouse effect is standard physics and confirmed by observations.

Lack of authority (24)
5 "There is no consensus" 97% of climate experts agree humans are causing global warming.
11 "Ice age predicted in the 70s" The vast majority of climate papers in the 1970s predicted warming.
19 "Al Gore got it wrong" Al Gore book is quite accurate, and far more accurate than contrarian books.
22 "Climategate CRU emails suggest conspiracy" A number of investigations have cleared scientists of any wrongdoing in the media-hyped email incident.
35 "IPCC is alarmist" The IPCC summarizes the recent research by leading scientific experts.
83 "500 scientists refute the consensus" Around 97% of climate experts agree that humans are causing global warming.
87 "Scientists tried to 'hide the decline' in global temperature" The 'decline' refers to a decline in northern tree-rings, not global temperature, and is openly discussed in papers and the IPCC reports.
108 "Peer review process was corrupted" An Independent Review concluded that CRU's actions were normal and didn't threaten the integrity of peer review.
109 "Less than half of published scientists endorse global warming" Around 97% of climate experts agree that humans are causing global warming.
101 "Lindzen and Choi find low climate sensitivity" Lindzen and Choi’s paper is viewed as unacceptably flawed by other climate scientists.
104 "Phil Jones says no global warming since 1995" Phil Jones was misquoted.
105 "Hansen's 1988 prediction was wrong" Jim Hansen had several possible scenarios; his mid-level scenario B was right.
117 "Over 31,000 scientists signed the OISM Petition Project" The 'OISM petition' was signed by only a few climatologists.
163 "Hansen predicted the West Side Highway would be underwater" Hansen was speculating on changes that might happen if CO2 doubled.
153 "Skeptics were kept out of the IPCC?" Official records, Editors and emails suggest CRU scientists acted in the spirit if not the letter of IPCC rules.
160 "Royal Society embraces skepticism" The Royal Society still strongly state that human activity is the dominant cause of global warming.
116 "Freedom of Information (FOI) requests were ignored" An independent inquiry found CRU is a small research unit with limited resources and their rigour and honesty are not in doubt.
121 "Naomi Oreskes' study on consensus was flawed" Benny Peiser, the Oreskes critic, retracted his criticism.
122 "Trenberth can't account for the lack of warming" Trenberth is talking about the details of energy flow, not whether global warming is happening.
130 "The IPCC consensus is phoney" 113 nations signed onto the 2007 IPCC report, which is simply a summary of the current body of climate science evidence
64 "IPCC were wrong about Amazon rainforests" The IPCC statement on Amazon rainforests was correct, and was incorrectly reported in some media.
132 "CRU tampered with temperature data" An independent inquiry went back to primary data sources and were able to replicate CRU's results.
106 "They changed the name from global warming to climate change" 'Global warming' and 'climate change' mean different things and have both been used for decades.
148 "Scientists retracted claim that sea levels are rising" The Siddall 2009 paper was retracted because its predicted sea level rise was too low.

Wrong consequences (12)
3 "It's not bad" Negative impacts of global warming on agriculture, health & environment far outweigh any positives.
8 "Animals and plants can adapt" Global warming will cause mass extinctions of species that cannot adapt on short time scales.
14 "Ocean acidification isn't serious" Past history shows that when CO2 rises quickly, there was mass extinctions of coral reefs.
16 "Hurricanes aren't linked to global warming" There is increasing evidence that hurricanes are getting stronger due to global warming.
155 "It's only a few degrees" A few degrees of global warming has a huge impact on ice sheets, sea levels and other aspects of climate.
138 "An exponential increase in CO2 will result in a linear increase in temperature" CO2 levels are rising so fast that unless we decrease emissions, global warming will accelerate this century.
111 "It's not urgent" A large amount of warming is delayed, and if we don’t act now we could pass tipping points.
150 "Coral atolls grow as sea levels rise" Thousands of coral atolls have "drowned" when unable to grow fast enough to survive at sea level.
69 "Corals are resilient to bleaching" Globally about 1% of coral is dying out each year.
48 "CO2 is plant food" The effects of enhanced CO2 on terrestrial plants are variable and complex and dependent on numerous factors
66 "Greenland ice sheet won't collapse" When Greenland was 3 to 5 degrees C warmer than today, a large portion of the Ice Sheet melted.
67 "Sea level rise predictions are exaggerated" Sea level rise is now increasing faster than predicted due to unexpectedly rapid ice melting.

We can’t prevent it (8)
165 "Removing all CO2 would make little difference" Removing CO2 would cause most water in the air to rain out and cancel most of the greenhouse effect.
158 "Renewable energy investment kills jobs" Investment in renewable energy creates more jobs than investment in fossil fuel energy.
118 "It's too hard" Scientific studies have determined that current technology is sufficient to reduce greenhouse gas emissions enough to avoid dangerous climate change.
127 "Renewables can't provide baseload power" A combination of renewables supplemented with natural gas can provide baseload power.
42 "CO2 limits will harm the economy" The benefits of a price on carbon outweigh the costs several times over.
62 "CO2 limits will hurt the poor" Those who contribute the least greenhouse gases will be most impacted by climate change.
98 "CO2 limits will make little difference" If every nation agrees to limit CO2 emissions, we can achieve significant cuts on a global scale.
102 "Renewable energy is too expensive" When you account for all of the costs associated with burning coal and other fossil fuels, like air pollution and health effects, in reality they are significantly more expensive than most renewable energy sources.

Global warming random walks

Someone mentioned randomness in an earlier post, and raised the problem of how it can exist in a (fairly) deterministic universe. Reply: this should not be a problem any more than the ‘randomness’ of the roulette wheel. Once the ball has left the hand of the croupier at a determinate momentum and velocity and place, and once the wheel is spinning without interference with determinate angular momentum, it is determinate where the ball will land. The physics of roulette is discussed here. But as Aristotle noted (somewhere) such determinism is nevertheless perfectly consistent with the appearance of randomness. Without accurate measuring equipment, and with the aid only of sight and hearing, we cannot predict where the roulette ball will fall, and so the outcome of each roulette game is effectively random (i.e. the statistical properties of the outcomes are not inconsistent with randomness). In roughly the same sense (I imagine) we cannot predict weather accurately. There is something about this here.

This does not mean that global warming is random, of course. As I understand it (I am sure the commenters will correct me if I am wrong), climate physics predicts an equilibrium temperature corresponding to any concentration of greenhouse gases in the atmosphere. All other things being equal, the temperature will revert over time to this value. But there are many forces pushing the climate away from and towards this equilibrium. There are cyclical forces pushing away from the equilibrium and back, e.g. the seasons. Summers tend to be warmer, winters colder, as we all know. In addition to this, there are apparently random deviations from these seasonal values which can be quite extreme.

The chart above shows the deviation of December minimum temperatures (as measured in Oxford) from 1853 to 2010 from the average minimum December temperature for all years. The mean is zero, but there is considerable deviation from that mean. Notable outliers are the Decembers of 1890, which is discussed here; 1962, which I remember as a young lad, when the sea froze and there was widespread disruption; 1981, when I was trapped in Wales for a few days in heavy snowfall; and 2010, when we even had snow in London.

Global warming - thanks for the links

Thanks to everyone who posted on my global warming questions.  It confirmed my view that the science of global warming is somewhat more complicated than the simple explanations suggest.  At some point I will collect together the links to resources, but I don't think that there is (yet) any resource on the web which takes the reader through every logical step of the argument but without being needlessly complex or difficult. The resources which go into detail have massively more than is logically required, and those which are aimed at a less 'technical' audience tend to skip over important logical steps - particularly the move involving the logarithm of CO2 concentration, which is not properly explained in any of the non-technical sources.

Wikipedia would be the ideal place for such a resource, but that has problems of its own (it seems to have a policy that the basic science should not be explained).

Global warming in logical form

I just found this draft paper. I hadn’t heard of Professor Bill Johns before, but his credentials seem respectable, and the paper is fascinating. It summarises the evidence and science behind each of the arguments that carbon dioxide is the main cause of the current global warming. In each case, it finds that the evidence is weaker than appears at first sight. The main arguments are as follows.

1. The Vostok argument. This is named from the Vostok ice core drilled by the Russians through Antarctic ice, and a subsequent study finding a strong correlation between the concentration of carbon dioxide and temperature over a period of 450,000 years. The data is available here. Johns notes that the correlation is striking but does not prove that increasing carbon dioxide causes increasing temperatures (medieval logicians called this the ‘fallacy of false cause’ - fallacia secundum non-causam ut causam). It is possible that the correlation simply results from the fact that when the global temperatures are low, carbon dioxide dissolves in the oceans and its concentration in the atmosphere is correspondingly reduced.

2. The exceptional rise argument. The argument is that the current rate of temperature rise is higher than any rise experienced on Earth for at least 10,000 years. This suggests that industrialisation is responsible for climate change. He concludes, using statistical analysis of earlier changes in temperature over long periods, that there may be something unusual in the current rate of global warming. “However, the statistics give only weak support to the hypothesis that there is something climatically unusual”.

3. The current correlation argument. The argument is that the current correlation between atmospheric carbon dioxide concentration and global warming is significant. Johns concludes that, from statistics alone, there is no reason to believe that the correlation between global warming and increased carbon dioxide concentrations is other than coincidence. “It follows that this coincidence cannot form part of the science supporting the Carbon Hypothesis”.

4. The simple science argument. Much of the support for the Carbon Hypothesis (as our commenter Belette noted) is that mathematical models of climate change predict temperatures rises with catastrophic results (i.e. 3 degrees C or more). Johns argues that mathematical models were originally designed for chemical or physical processes that are well understood, but the physics and chemistry of climate processes is not so well understood. “Modellers do not have a set of similar planets to test their models on, or to evolve their modelling tools”. His comments about the interaction between water vapour (which is the most significant greenhouse gas), and carbon dioxide, are interesting. In the presence of excess water vapour the absorptivity of carbon dioxide is strongly suppressed, and at sea level the contribution of carbon dioxide to infra-red absorption is negligible compared to the natural variability of water vapour concentration in the atmosphere. Thus the science is not so simple.

5. The consensus argument. The IPCC has a number of reliable climate models from which it concludes that there is a 90% probability that carbon dioxide is causing global warming. How can all of those scientists be wrong? Johns notes that few of these climate scientists are “main-stream scientists”, and that most come from a weather-forecasting (meteorology) background. They are not used to formulating and testing models like other scientists because they cannot go back to the laboratory to test the various elements of the model; they have to wait for the climatic conditions to arise that test the models. We should therefore read ‘scientific consensus on global warming’ as ‘meteorologists consensus on global warming’.

Please note that I am simply summarising his arguments. Note also that this is a logic blog. Arguments like ‘X doesn’t understand climate science’ or ‘Y is a global warming denier’ are logical fallacies. From a logical point of view, there are essentially only two replies to an argument of the form “p and p implies q, therefore q”. The first is that p does not imply q. The second is that p is not true.

The London plumbing crisis resolved

Summarising the gobal warming discussion so far. My ‘global warming scepticism’ is simply that the evidence for catastrophic climate change is not clear. A sceptic naturally wants evidence for p or not-p, otherwise (if necessary) he is entitled to be sceptical about both p and not-p. Excluded middle does not apply to propositions embedded in the ‘sceptical about’ operator.

Now, there is a simple ‘textbook’ or ‘idealised’ climate model that can be easily explained, and is clearly nothing to be sceptical about. But this predicts nothing catastrophic (at least not for a long time). Now there is a much more complex model, which involves ‘feedback’ effects. But the problem there, as our commenter says is that “If you want a very simple explanation of how much warming you get from increasing CO2 by Y% then you can't have one: the full theory plus modelling of the earth system is too complex.”

This is a problem for scepticism. If we drop the Fermi assumption that all complex things can be explained simply, and accept that there are some things that are simply too difficult to be explained in a short time, it follows that there will be situations where a sceptic – who is a generalist – is unable to challenge statements made by a specialist. But if unable to do that, he is no longer a sceptic.

One ray of light, however, is that at least one of my several plumbing crises may not be as serious as I feared. A clever site here tells us, for any given rise in sea level, whether our property is flooded or not. It tells me that substantial parts of West London will remain above water even with a rise of 3m. Within 500 years, London may look like Venice. That is something definitely to be welcomed.

How catastrophic is catastrophic?

As there has been no sign of a Fermi explanation so far, I had a go for myself, largely with the help of this paper. Yes, I am aware that Lindzen is widely held to be a climate change denialist and therefore an evil monster, but I admire the way he writes clearly and convincingly and without belittling or talking down to his audience.

The concentration of carbon dioxide has increased since the beginning of the industrial age from about 280 parts per million (ppm) to about 390 ppm.  According to the simple 'textbook' model* of global warming, it is generally accepted that the warming from a doubling of carbon dioxide would only be about 1°C.  That is, the amount of carbon dioxide currently in the atmosphere (about 390 ppm) would have to double to 780 ppm in order to cause a rise in global equilibrium temperature of 1°C.  Simple arithmetic based on the rate of increase in CO2 (see the graph above) suggest that this would take almost 250 years to happen. Furthermore, because of the logarithmic effect - each doubling producing the same arithmetic increase - it would take 250+500 = 750 years to produce a 2°C rise.  This is hardly catastrophic, and gives us some time to do something.  I'll hang on to those incandescent bulbs for now.

But this is much less than current climate models suggest from the warming from a doubling of carbon dioxide.  Why is that?

*To avoid any confusion, I mean the simple textbook model described here as ‘this model’, i.e. where it says “Thus this model predicts a global warming of ΔTs = 1.2 K for a doubling of carbon dioxide.”. 

Arctic meltdown to flood London

I discussed a suitable understanding of ‘global warming’ yesterday, settling on ‘catastrophic man-made global warming’. By extraordinary chance one of the cheaper (in fact free) tabloids this morning was talking about how global warming could cause a meltdown of the Arctic, flooding London. That’s what I call catastrophic! I live close to the Thames, and hardly relish the thought of having to leave the basement for the upper floors, and travelling to Tesco’s by boat, within my lifetime or my children’s.

But let’s move on to reasons for believing in this catastrophe. Clearly the catastrophic flooding will be caused by higher temperatures. But how high do the temperatures have to get, and how will this be caused? What is the Fermi explanation?

Definition of global warming

'Belette' commented that I hadn't been consistent in my definition of 'global warming'*.  I had asked for a 'Fermi explanation' showing why it exists, but that requires an understood and agreed definition of what it is.  OK.  There are three ideas locked up in that term, as commonly used and understood.  First, that warming is not a mere accident.  'Global warming' does not mean simply that the earth is hotter than it was some time ago. It means that there is some underlying cause or reason why it is getting warmer, and that as long as the cause exists, the warming will go on.  Second, that the underlying cause or reason is the cumulative increase in carbon dioxide in the atmosphere, caused by industrialisation.  This is properly called 'anthropogenic' global warming, but it usually has that meaning even without the qualification.  Third, that the warming will if unchecked lead to to disaster.  This should properly be called 'catastrophic anthropogenic global warming'. 

The proposition I am sceptical about is there "that increasing atmospheric concentrations of greenhouse gases, notably carbon dioxide, will have catastrophic consequences for mankind and for the planet".  Obvious I don't deny that the cumulative increase in carbon dioxide is causing long-term global temperature to rise.  But no one has explained clearly to me why this should matter.

*Vallicella has just reminded me that he has some definitions here.

Global Warming 2: “For details, read the papers”

The title is taken from a comment to my last post about global warming scepticism. That kind of remark is the source of my irritation with the global warmist lobby. They are telling us that everything is very bad, and exhorting me to throw away my stash of incandescent bulbs. But they aren’t given us sufficient reason to believe what they say, other than ‘scientific consensus’ or ‘read the papers’. Here is the comment:

The (surface of the) earth is warmer than if it was just heated by the sun, because it is heated by two sources: the sun and the atmosphere. [This is the inappropriately named ‘greenhouse effect’]. More atmosphere, more ‘greenhouse effect’. For the details, read the papers.

Commenter, this in no way wins you a £5 voucher. A ‘Fermi explanation’ has to be a complete chain of reasoning from cause (or evidence) to effect. Approximations are OK, so are gross assumptions, so long as they are reasonable assumptions, but every link of the logical chain has to be visible. Your comment is wholly useless in this respect. It doesn’t explain the relation between carbon emissions and ‘atmosphere’, nor the relation between ‘atmosphere’ and temperature, nor the relation between temperature and ‘damage’ or ‘harm to planet’. So, no prize, sorry.

On ‘read the article’, about a year ago I got tired of reading stuff about ‘scientific consensus’ and tried to work the whole thing out for myself. It was surprisingly hard. Wikipedia articles like this are a useful overview, but they remind me of those science books I read avidly at the age of 8, how telephones work, how air brakes work, how jet engines work. A useful ‘pictorial overview’, but without depth of explanation. This article is much better, but fails for two crucial reasons. First, it is mathematical. Although the mathematics is not very difficult, there are many people to whom this kind of reasoning is impenetrable. A verbal, or pictorial explanation (or a combination of those modes of explanation) is needed to explain the underlying reasoning, without the maths. The second fault is far worse, because it fails to connect the variable representing the amount of atmosphere, with the industrial process. It neatly explains in a quantitative way how increases in epsilon correspond to changes in equilibrium temperature. But it doesn’t explain how emissions in carbon dioxide are related to epsilon*. Which is what we wanted to know. How much is my stash of incandescent bulbs likely to increase the equilibrium temperature of the earth? Don’t know, and I am keeping the stash for now.

*To be fair, the article does state this implicitly, in the bit where it says “The radiative forcing for doubling carbon dioxide is 3.71 W m−2”. But it doesn’t explain where that figure comes from, nor does the article http://en.wikipedia.org/wiki/Radiative_forcing it links to. And it only gives figures for carbon dioxide emissions. As I mentioned in the previous post, carbon dioxide is not the only greenhouse gas.

Why I an a global warming sceptic

The Maverick Philosopher links to a global warming article by a Harvard Physics professor. The gist of it is that the current “climate crusade” against global warming is a moral epidemic. The notion that increasing atmospheric concentrations of greenhouse gases, notably carbon dioxide, will have disastrous consequences for mankind and for the planet, is based on contested science and dubious claims, he says.

This is a blog which is concerned with ‘sceptical’ issues, so it ought to be concerned with global warming scepticism. But that means scepticism in the strict and proper sense: not holding any positive opinions about p (or not-p), but rather holding that the evidence for p (or not-p) is not sufficient, or reasonable, or conclusive. Humanity is divided into fundamentally two types: those who sit at the front of the class and listen with rapt attention to everything Teacher said (as well as sucking up and toadying to Teacher and all other forms of authority with unquestioning acceptance); and those who sit and the back and talk and throw objects at those in the front, and generally disrepect all forms of authority. True believers at the front, sceptics and disbelievers and mockers and scorners, at the back. The world would be a disastrous place if either type predominated. A world of believers would be dreary and authoritarian if their beliefs were consistent. If not consistent, in would be full of more bloodshed and warfare. In a world of mockers and sneerers, nothing would ever get done, and it would also be boring with no true believers and boy scouts to sneer at and mock.

I am a global warming sceptic in the sense that I remain unconvinced that it exists. Equally I remain unconvinced that it doesn’t exist - being a cautious fellow and mindful of the possibility that it does, I very rarely use a car (the one I bought three years ago has done little more than 5,000 miles), and my heating bills are lower than anyone I know. I am both a global-warming and and anti-global warming sceptic.

Why am I sceptical that it exists? I see a scientific model, and empirical evidence adduced in support of the model. Taking the empirical evidence first, it is primarily statistical, given that the actual temperature data is noisy and subject to error. All kinds of extrapolation and curve-fitting is required to produce the neat ‘hockey stick’ graph that appears to show a constant temperature from the year 1000 until about 1850, when the temperature began to rise like the blade of a hockey stick. Since I don’t accept probabilities between 0 and 1, I don’t accept statistics. The temptation to select data to fit the theory is simply too strong. On the side of the model, there is a robust physical model which predicts rises in temperature for increasing amounts of greenhouse gases in the atmosphere. The problem is that water vapour is also a powerful greenhouse gas, and the amount of water vapour in the atmosphere is difficult to model. Add to that the fact that the effect of carbon dioxide obeys a logarithmic law – to get the same effect as doubling the amount, you have to double it again, and again) – a fact which I have never seen mentioned in any of the global warming propaganda in schools and the mainstream media. Nor is it mentioned in the truly horrible Wikipedia article on the Global Warming controversy. The article simply repeats over and over that there is a scientific consensus on GW (the word ‘consensus’ is repeated 26 times). It gives no substantial arguments or reasoning or basis facts on either side of the debate.

This will probably provoke all sorts of rude emails, to which I say, don’t be rude, just give me a neat Fermi argument to prove to me beyond reasonable doubt that a serious global warming problem exists. I am not interested in what any scientists conclude. I am interested in the basic evidence they have used, and the reasoning process which leads them to their conclusion. Possibility of another £5 Waitrose voucher for any decent answers (I am the final judge however).