Arguments from Global Warming Skeptics and what the science really says

 

Arguments from Global Warming Skeptics and what the science really says.

Global Warming & Climate Change Myths

Here is a summary of global warming and climate change myths, sorted by recent popularity vs what science says. Note that the one line responses are just a starting point – click the response for a more detailed response. You can also view them sorted by taxonomy, by popularity, in a print-friendly version, with short URLs or with fixed numbers you can use for permanent references.

Skeptic Argument vs What the Science Says
1 “Climate’s changed before” Climate reacts to whatever forces it to change at the time; humans are now the dominant forcing.
2 “It’s the sun” In the last 35 years of global warming, sun and climate have been going in opposite directions
3 “It’s not bad” Negative impacts of global warming on agriculture, health & environment far outweigh any positives.
4 “There is no consensus” 97% of climate experts agree humans are causing global warming.
5 “It’s cooling” The last decade 2000-2009 was the hottest on record.
6 “Models are unreliable” Models successfully reproduce temperatures since 1900 globally, by land, in the air and the ocean.
7 “Temp record is unreliable” The warming trend is the same in rural and urban areas, measured by thermometers and satellites.
8 “Animals and plants can adapt” Global warming will cause mass extinctions of species that cannot adapt on short time scales.
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.
11 “Ice age predicted in the 70s” The vast majority of climate papers in the 1970s predicted warming.
12 “CO2 lags temperature” CO2 didn’t initiate warming from past ice ages but it did amplify the warming.
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.
14 “Climate sensitivity is low” Net positive feedback is confirmed by many different lines of evidence.
15 “Ocean acidification isn’t serious” Past history shows that when CO2 rises quickly, there was mass extinctions of coral reefs.
16 “Hockey stick is broken” Recent studies agree that recent global temperatures are unprecedented in the last 1000 years.
17 “Hurricanes aren’t linked to global warming” There is increasing evidence that hurricanes are getting stronger due to global warming.
18 “Glaciers are growing” Most glaciers are retreating, posing a serious problem for millions who rely on glaciers for water.
19 “Al Gore got it wrong” Al Gore book is quite accurate, and far more accurate than contrarian books.
20 “Climategate CRU emails suggest conspiracy” A number of investigations have cleared scientists of any wrongdoing in the media-hyped email incident.
21 “It’s cosmic rays” Cosmic rays show no trend over the last 30 years & have had little impact on recent global warming.
22 “1934 – hottest year on record” 1934 was one of the hottest years in the US, not globally.
23 “It’s freaking cold!” A local cold day has nothing to do with the long-term trend of increasing global temperatures.
24 “Extreme weather isn’t caused by global warming” Extreme weather events are being made more frequent and worse by global warming.
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.
27 “Mars is warming” Mars is not warming globally.
28 “Arctic icemelt is a natural cycle” Thick arctic sea ice is undergoing a rapid retreat.
29 “Medieval Warm Period was warmer” Globally averaged temperature now is higher than global temperature in medieval times.
30 “Increasing CO2 has little to no effect” The strong CO2 effect has been observed by many different measurements.
31 “Oceans are cooling” The most recent ocean measurements show consistent warming.
32 “It’s a 1500 year cycle” Ancient natural cycles are irrelevant for attributing recent global warming to humans.
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.
35 “IPCC is alarmist” The IPCC summarizes the recent research by leading scientific experts.
36 “Polar bear numbers are increasing” Polar bears are in danger of extinction as well as many other species.
37 “Greenland was green” Other parts of the earth got colder when Greenland got warmer.
38 “Greenland is gaining ice” Greenland on the whole is losing ice, as confirmed by satellite measurement.
39 “It’s not happening” There are many lines of evidence indicating global warming is unequivocal.
40 “CO2 limits will harm the economy” The benefits of a price on carbon outweigh the costs several times over.
41 “Other planets are warming” Mars and Jupiter are not warming, and anyway the sun has recently been cooling slightly.
42 “There’s no empirical evidence” There are multiple lines of direct observations that humans are causing global warming.
43 “Arctic sea ice has recovered” Thick arctic sea ice is in rapid retreat.
44 “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
45 “There’s no correlation between CO2 and temperature” There is long-term correlation between CO2 and global temperature; other effects are short-term.
46 “CO2 is plant food” The effects of enhanced CO2 on terrestrial plants are variable and complex and dependent on numerous factors
47 “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
48 “It cooled mid-century” Mid-century cooling involved aerosols and is irrelevant for recent global warming.
49 “Satellites show no warming in the troposphere” The most recent satellite data show that the earth as a whole is warming.
50 “CO2 was higher in the past” When CO2 was higher in the past, the sun was cooler.
51 “It warmed before 1940 when CO2 was low” Early 20th century warming is due to several causes, including rising CO2.
52 “It’s aerosols” Aerosols have been masking global warming, which would be worse otherwise.
53 “It’s El Niño” El Nino has no trend and so is not responsible for the trend of 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 “It’s Pacific Decadal Oscillation” The PDO shows no trend, and therefore the PDO is not responsible for the trend of global warming.
57 “2009-2010 winter saw record cold spells” A cold day in Chicago in winter has nothing to do with the trend of global warming.
58 “It’s a natural cycle” No known natural forcing fits the fingerprints of observed warming except anthropogenic greenhouse gases.
59 “Scientists can’t even predict weather” Weather and climate are different; climate predictions do not need weather detail.
60 “IPCC were wrong about Himalayan glaciers” Glaciers are in rapid retreat worldwide, despite 1 error in 1 paragraph in a 1000 page IPCC report.
61 “2nd law of thermodynamics contradicts greenhouse theory” The 2nd law of thermodynamics is consistent with the greenhouse effect which is directly observed.
62 “It’s not us” Multiple sets of independent observations find a human fingerprint on climate change.
63 “It’s the ocean” The oceans are warming and moreover are becoming more acidic, threatening the food chain.
64 “IPCC were wrong about Amazon rainforests” The IPCC statement on Amazon rainforests was correct, and was incorrectly reported in some media.
65 “CO2 limits will hurt the poor” Those who contribute the least greenhouse gases will be most impacted by climate change.
66 “Clouds provide negative feedback” Evidence is building that net cloud feedback is likely positive and unlikely to be strongly negative.
67 “CO2 effect is saturated” Direct measurements find that rising CO2 is trapping more heat.
68 “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.
69 “Sea level rise predictions are exaggerated” Sea level rise is now increasing faster than predicted due to unexpectedly rapid ice melting.
70 “Volcanoes emit more CO2 than humans” Humans emit 100 times more CO2 than volcanoes.
71 “Corals are resilient to bleaching” Globally about 1% of coral is dying out each year.
72 “Greenhouse effect has been falsified” The greenhouse effect is standard physics and confirmed by observations.
73 “The science isn’t settled” That human CO2 is causing global warming is known with high certainty & confirmed by observations.
74 “It’s methane” Methane plays a minor role in global warming but could get much worse if permafrost starts to melt.
75 “Global warming stopped in 1998, 1995, 2002, 2007, 2010, ????” Global temperature is still rising and 2010 was the hottest recorded.
76 “CO2 has a short residence time” Excess CO2 from human emissions has a long residence time of over 100 years
77 “Humidity is falling” Multiple lines of independent evidence indicate humidity is rising and provides positive feedback.
78 “Neptune is warming” And the sun is cooling.
79 “Springs aren’t advancing” Hundreds of flowers across the UK are flowering earlier now than any time in 250 years.
80 “Jupiter is warming” Jupiter is not warming, and anyway the sun is cooling.
81 “CO2 measurements are suspect” CO2 levels are measured by hundreds of stations across the globe, all reporting the same trend.
82 “It’s land use” Land use plays a minor role in climate change, although carbon sequestration may help to mitigate.
83 “500 scientists refute the consensus” Around 97% of climate experts agree that humans are causing global warming.
84 “CO2 is not increasing” CO2 is increasing rapidly, and is reaching levels not seen on the earth for millions of years.
85 “Record snowfall disproves global warming” Warming leads to increased evaporation and precipitation, which falls as increased snow in winter.
86 “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.
87 “Pluto is warming” And the sun has been recently cooling.
88 “CO2 is coming from the ocean” The ocean is absorbing massive amounts of CO2, and is becoming more acidic as a result.
89 “Solar Cycle Length proves its the sun” The sun has not warmed since 1970 and so cannot be driving global warming.
90 “Arctic was warmer in 1940” The actual data show high northern latitudes are warmer today than in 1940.
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 “CO2 limits will make little difference” If every nation agrees to limit CO2 emissions, we can achieve significant cuts on a global scale.
94 “It’s microsite influences” Microsite influences on temperature changes are minimal; good and bad sites show the same trend.
95 “CO2 is not the only driver of climate” Theory, models and direct measurement confirm CO2 is currently the main driver of climate change.
96 “Peer review process was corrupted” An Independent Review concluded that CRU’s actions were normal and didn’t threaten the integrity of peer review.
97 “It’s albedo” Albedo change in the Arctic, due to receding ice, is increasing global warming.
98 “Tree-rings diverge from temperature after 1960” This is a detail that is complex, local, and irrelevant to the observed global warming trend.
99 “Lindzen and Choi find low climate sensitivity” Lindzen and Choi’s paper is viewed as unacceptably flawed by other climate scientists.
100 “It’s soot” Soot stays in the atmosphere for days to weeks; carbon dioxide causes warming for centuries.
101 “Humans are too insignificant to affect global climate” Humans are small but powerful, and human CO2 emissions are causing global warming.
102 “Dropped stations introduce warming bias” If the dropped stations had been kept, the temperature would actually be slightly higher.
103 “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.
104 “Phil Jones says no global warming since 1995” Phil Jones was misquoted.
105 “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.
106 “Roy Spencer finds negative feedback” Spencer’s model is too simple, excluding important factors like ocean dynamics and treats cloud feedbacks as forcings.
107 “Hansen’s 1988 prediction was wrong” Jim Hansen had several possible scenarios; his mid-level scenario B was right.
108 “It’s global brightening” This is a complex aerosol effect with unclear temperature significance.
109 “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.
110 “It’s too hard” Scientific studies have determined that current technology is sufficient to reduce greenhouse gas emissions enough to avoid dangerous climate change.
111 “It’s a climate regime shift” There is no evidence that climate has chaotic “regimes” on a long-term basis.
112 “It’s not urgent” A large amount of warming is delayed, and if we don’t act now we could pass tipping points.
113 “Less than half of published scientists endorse global warming” Around 97% of climate experts agree that humans are causing global warming.
114 “Arctic sea ice loss is matched by Antarctic sea ice gain” Arctic sea ice loss is three times greater than Antarctic sea ice gain.
115 “Solar cycles cause global warming” Over recent decades, the sun has been slightly cooling & is irrelevant to recent global warming.
116 “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.
117 “Over 31,000 scientists signed the OISM Petition Project” The ‘OISM petition’ was signed by only a few climatologists.
118 “Earth hasn’t warmed as much as expected” This argument ignores the cooling effect of aerosols and the planet’s thermal inertia.
119 “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.
120 “It’s ozone” Ozone has only a small effect.
121 “IPCC ‘disappeared’ the Medieval Warm Period” The IPCC simply updated their temperature history graphs to show the best data available at the time.
122 “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
123 “Trenberth can’t account for the lack of warming” Trenberth is talking about the details of energy flow, not whether global warming is happening.
124 “Ice Sheet losses are overestimated” A number of independent measurements find extensive ice loss from Antarctica and Greenland.
125 “Naomi Oreskes’ study on consensus was flawed” Benny Peiser, the Oreskes critic, retracted his criticism.
126 “Climate is chaotic and cannot be predicted” Weather is chaotic but climate is driven by Earth’s energy imbalance, which is more predictable.
127 “Melting ice isn’t warming the Arctic” Melting ice leads to more sunlight being absorbed by water, thus heating the Arctic.
128 “Climate ‘Skeptics’ are like Galileo” Modern scientists, not anti-science skeptics, follow in Galileo’s footsteps.
129 “A drop in volcanic activity caused warming” Volcanoes have had no warming effect in recent global warming – if anything, a cooling effect.
130 “Renewables can’t provide baseload power” A number of renewable sources already do provide baseload power, and we don’t need renewables to provide a large percentage of baseload power immediately.
131 “Breathing contributes to CO2 buildup” By breathing out, we are simply returning to the air the same CO2 that was there to begin with.
132 “Satellite error inflated Great Lakes temperatures” Temperature errors in the Great Lakes region are not used in any global temperature records.
133 “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.
134 “CRU tampered with temperature data” An independent inquiry went back to primary data sources and were able to replicate CRU’s results.
135 “Sea level is not rising” The claim sea level isn’t rising is based on blatantly doctored graphs contradicted by observations.
136 “Water vapor in the stratosphere stopped global warming” This possibility just means that future global warming could be even worse.
137 “CO2 emissions do not correlate with CO2 concentration” That humans are causing the rise in atmospheric CO2 is confirmed by multiple isotopic analyses.
138 “We’re heading into cooling” There is no scientific basis for claims that the planet will begin to cool in the near future.
139 “The sun is getting hotter” The sun has just had the deepest solar minimum in 100 years.
140 “Mauna Loa is a volcano” The global trend is calculated from hundreds of CO2 measuring stations and confirmed by satellites.
141 “It’s waste heat” Greenhouse warming is adding 100 times more heat to the climate than waste heat.
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.
143 “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.
144 “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.
145 “Murry Salby finds CO2 rise is natural” Multiple lines of evidence make it very clear that the rise in atmospheric CO2 is due to human emissions.
146 “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.
147 “Antarctica is too cold to lose ice” Glaciers are sliding faster into the ocean because ice shelves are thinning due to warming oceans.
148 “Water levels correlate with sunspots” This detail is irrelevant to the observation of global warming caused by humans.
149 “CO2 was higher in the late Ordovician” The sun was much cooler during the Ordovician.
150 “It’s CFCs” CFCs contribute at a small level.
151 “Scientists retracted claim that sea levels are rising” The Siddall 2009 paper was retracted because its predicted sea level rise was too low.
152 “Warming causes CO2 rise” Recent warming is due to rising CO2.
153 “Coral atolls grow as sea levels rise” Thousands of coral atolls have “drowned” when unable to grow fast enough to survive at sea level.
154 “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.
155 “Positive feedback means runaway warming” Positive feedback won’t lead to runaway warming; diminishing returns on feedback cycles limit the amplification.
156 “DMI show cooling Arctic” While summer maximums have showed little trend, the annual average Arctic temperature has risen sharply in recent decades.
157 “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.
158 “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.
159 “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.
160 “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
161 “Renewable energy investment kills jobs” Investment in renewable energy creates more jobs than investment in fossil fuel energy.
162 “CO2 increase is natural, not human-caused” Many lines of evidence, including simple accounting, demonstrate beyond a shadow of a doubt that the increase in atmospheric CO2 is due to human fossil fuel burning.
163 “Royal Society embraces skepticism” The Royal Society still strongly state that human activity is the dominant cause of global warming.
164 “It’s satellite microwave transmissions” Satellite transmissions are extremely small and irrelevant.
165 “CO2 only causes 35% of global warming” CO2 and corresponding water vapor feedback are the biggest cause of global warming.
166 “We didn’t have global warming during the Industrial Revolution” CO2 emissions were much smaller 100 years ago.
167 “Hansen predicted the West Side Highway would be underwater” Hansen was speculating on changes that might happen if CO2 doubled.
168 “Ljungqvist broke the hockey stick” Ljungqvist’s temperature reconstruction is very similar to other reconstructions by Moberg and Mann.
169 “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.
170 “Postma disproved the greenhouse effect” Postma’s model contains many simple errors; in no way does Postma undermine the existence or necessity of the greenhouse effect.
171 “Sea level fell in 2010” The temporary drop in sea level in 2010 was due to intense land flooding caused by a strong La Nina.

 

refutation of climate change deniers

Hi Hugh,

You say : “…the ten year cooling trend?…”

I say : What utter piffle ! Just look at this chart (link below). It’s
a very simplified form of the temperature charts, just to make it easy
for people like me to refute people like you :-

http://data.giss.nasa.gov/gistemp/graphs/Ts_vs.year+month.lrg.gif

More charts that refute your statement are here :-

http://data.giss.nasa.gov/gistemp/graphs/

http://www.ncdc.noaa.gov/oa/climate/research/2009/perspectives.html

You’re clearly not up-to-date. One icy winter does not Global Cooling
make. In fact, there could be an excessive warming trend for a while
(as opposed to a badly warming trend for a while) :-

http://blogs.usatoday.com/sciencefair/
“Global warming and a hotter solar cycle will bump up average
atmospheric temperatures about a third of a degree by 2014, and then
flatten out for the rest of the decade, suggest climate scientists.”

You are wrong about Global Warming, but you’re in communication with a
group of people who would deny black is black, so I don’t expect you
to believe me.

Please don’t continue sending me Climate Change Denier myths. Please
only talk to me about Energy.

 

Thank you,

Jo Abess

http://www.joabbess.com/
http://www.changecollege.org.uk/

The above in response to Hugh Sharman’s post below:
On Mon, Aug 24, 2009 at 8:34 AM, Hugh Sharmanwrote:
> ….continuing the ten year cooling trend?  We shall have to see!
>
> US Gas Market Watch
> NGW’s Gas Market Reconnaissance (Friday, Aug. 21, 2009) Full Story Pub Info
> Send to a Friend
> Natural gas prices fell nearly 4% Friday touching $2.776/MMBTtu, the lowest
> price since Aug. 12, 2002. Friday’s selling pressure was realized after
> hedge funds in the OTC market began pounding prices lower. Traders said the
> reality of a truly oversupplied market is creating an ultra-bearish
> sentiment throughout the gas market. However, Friday also marked the 12th
> consecutive losing session, so a rebound could be expected as September
> nears expiration on Thursday.
>
> Lucky US: Gas Storage Glut Could Meet Bone-Chilling Winter Loads
> Natural Gas Week (Monday, August 24, 2009) Full Story Pub Info Send to a
> Friend
> Some weather forecasting services are providing a preliminary glimpse at the
> upcoming 2009-10 winter … and the outlook is cold, very cold. In fact,
> some forecasters see the potential for the coldest winter in a decade. If
> these forecasts pan out, the US may need every molecule of natural gas being
> stuffed into its brimming storage fields.
>
> Hugh Sharman
> Box 39, Toldbodvej 12,
> DK-9370 Hals, Denmark,
> tel +45.9825.1760 fax +45.9825.2555
> cell +45.4055.1760
> MOMs (Danish VAT) DK.10.54.57.73

Seven Answers to Climate Contrarian Nonsense

On November 18, with the United Nations Global Warming Conference in Copenhagen fast approaching, U.S. Sen. James R. Inhofe (R–Okla.) took the floor of the Senate and proclaimed 2009 to be “The Year of the Skeptic.” Had the senator’s speech marked a new commitment to  dispassionate, rational inquiry, a respect for scientific thought and a well-grounded doubt in ghosts, astrology, creationism and homeopathy, it might have been cause for cheer. But Inhofe had a more narrow definition of skeptic in mind: he meant “standing up and exposing the science, the costs and the hysteria behind global warming alarmism.”

Within the community of scientists and others concerned about anthropogenic climate change, those whom Inhofe calls skeptics are more commonly termed contrarians, naysayers and denialists. Not everyone who questions climate change science fits that description, of course—some people are genuinely unaware of the facts or honestly disagree about their interpretation. What distinguishes the true naysayers is an unwavering dedication to denying the need for action on the problem, often with weak and long-disproved arguments about supposed weaknesses in the science behind global warming.

What follows is only a partial list of the contrarians’ bad arguments and some brief rebuttals of them.

Claim 1: Anthropogenic CO2 can’t be changing climate, because CO2 is only a trace gas in the atmosphere and the amount produced by humans is dwarfed by the amount from volcanoes and other natural sources. Water vapor is by far the most important greenhouse gas, so changes in CO2 are irrelevant.

Although CO2 makes up only 0.04 percent of the atmosphere, that small number says nothing about its significance in climate dynamics. Even at that low concentration, CO2 absorbs infrared radiation and acts as a greenhouse gas, as physicist John Tyndall demonstrated in 1859. The chemist Svante Arrhenius went further in 1896 by estimating the impact of CO2 on the climate; after painstaking hand calculations he concluded that doubling its concentration might cause almost 6 degrees Celsius of warming—an answer not much out of line with recent, far more rigorous computations.

Contrary to the contrarians, human activity is by far the largest contributor to the observed increase in atmospheric CO2. According to the U.S. Geological Survey, anthropogenic CO2 amounts to about 30 billion tons annually—more than 130 times as much as volcanoes produce. True, 95 percent of the releases of CO2 to the atmosphere are natural, but natural processes such as plant growth and absorption into the oceans pull the gas back out of the atmosphere and almost precisely offset them, leaving the human additions as a net surplus. Moreover, several sets of experimental measurements, including analyses of the shifting ratio of carbon isotopes in the air, further confirm that fossil-fuel burning and deforestation are the primary reasons that CO2 levels have risen 35 percent since 1832, from 284 parts per million (ppm) to 388 ppm—a remarkable jump to the highest levels seen in millions of years.

Contrarians frequently object that water vapor, not CO2, is the most abundant and powerful greenhouse gas; they insist that climate scientists routinely leave it out of their models. The latter is simply untrue: from Arrhenius on, climatologists have incorporated water vapor into their models. In fact, water vapor is why rising CO2 has such a big effect on climate. CO2 absorbs some wavelengths of infrared that water does not so it independently adds heat to the atmosphere. As the temperature rises, more water vapor enters the atmosphere and multiplies CO2’s greenhouse effect; the IPCC notes that water vapor (pdf) may “approximately double the increase in the greenhouse effect due to the added CO2 alone.”

Nevertheless, within this dynamic, the CO2 remains the main driver (what climatologists call a “forcing”) of the greenhouse effect. As NASA climatologist Gavin Schmidt has explained, water vapor enters and leaves the atmosphere much more quickly than CO2, and tends to preserve a fairly constant level of relative humidity, which caps off its greenhouse effect. Climatologists therefore categorize water vapor as a feedback rather than a forcing factor. (Contrarians who don’t see water vapor in climate models are looking for it in the wrong place.)

Because of CO2’s inescapable greenhouse effect, contrarians holding out for a natural explanation for current global warming need to explain why, in their scenarios, CO2 is not compounding the problem.

Claim 2: The alleged “hockey stick” graph of temperatures over the past 1,600 years has been disproved. It doesn’t even acknowledge the existence of a “medieval warm period” around 1000 A.D. that was hotter than today is. Therefore, global warming is a myth.

It is hard to know which is greater: contrarians’ overstatement of the flaws in the historical temperature reconstruction from 1998 by Michael E. Mann and his colleagues, or the ultimate insignificance of their argument to the case for climate change.

First, there is not simply one hockey-stick reconstruction of historical temperatures using one set of proxy data. Similar evidence for sharply increasing temperatures over the past couple of centuries has turned up independently while looking at ice cores, tree rings and other proxies for direct measurements, from many locations. Notwithstanding their differences, they corroborate that Earth has been getting sharply warmer.

A 2006 National Research Council review of the evidence concluded “with a high level of confidence that global mean surface temperature was higher during the last few decades of the 20th century than during any comparable period during the preceding four centuries”—which is the section of the graph most relevant to current climate trends. The report placed less faith in the reconstructions back to 900 A.D., although it still viewed them as “plausible.” Medieval warm periods in Europe and Asia with temperatures comparable to those seen in the 20th century were therefore similarly plausible but might have been local phenomena: the report noted “the magnitude and geographic extent of the warmth are uncertain.” And a new research paper by Mann and his colleagues seems to confirm that the Medieval Warm Period and the “Little Ice Age” between 1400 and 1700 were both caused by shifts in solar radiance and other natural factors that do not seem to be happening today.

After the NRC review was released, another analysis by four statisticians, called the Wegman report, which was not formally peer reviewed, was more critical of the hockey stick paper. But correction of the errors it pointed out did not substantially change the shape of the hockey stick graph. In 2008 Mann and his colleagues issued an updated version of the temperature reconstruction that echoed their earlier findings.

But hypothetically, even if the hockey stick was busted… What of it? The case for anthropogenic global warming originally came from studies of climate mechanics, not from reconstructions of past temperatures seeking a cause. Warnings about current warming trends came out years before Mann’s hockey stick graph. Even if the world were incontrovertibly warmer 1,000 years ago, it would not change the fact that the recent rapid rise in CO2 explains the current episode of warming more credibly than any natural factor does—and that no natural factor seems poised to offset further warming in the years ahead.

Claim 3: Global warming stopped a decade ago; Earth has been cooling since then.

1998 was the world’s warmest year in the U.K. Met Office Hadley Centre’s records; recent years have been cooler; therefore, the previous century’s global warming trend is over, right?

Anyone with even a glancing familiarity with statistics should be able to spot the weaknesses of that argument. Given the extended duration of the warming trend, the expected (and observed) variations in the rate of increase and the range of uncertainties in the temperature measurements and forecasts, a decade’s worth of mild interruption is too small a deviation to prove a break in the pattern, climatologists say.

Recently, Associated Press reporter Seth Borenstein asked four independent statisticians to look for trends in the temperature data sets without telling them what the numbers represented. “The experts found no true temperature declines over time,” he wrote.

If a lull in global warming continues for another decade, would that vindicate the contrarians’ case? Not necessarily, because climate is complex. For instance, Mojib Latif of the Leibniz Institute of Marine Sciences in Germany and his colleagues published a paper in 2008 that suggested ocean circulation patterns might cause a period of cooling in parts of the northern hemisphere, even though the long-term pattern of warming remained in effect. Fundamentally, contrarians who have resisted the abundant evidence that supports warming should not be too quick to leap on evidence that only hints at the opposite.

Claim 4: The sun or cosmic rays are much more likely to be the real causes of global warming. After all, Mars is warming up, too.

Astronomical phenomena are obvious natural factors to consider [pdf] when trying to understand climate, particularly the brightness of the sun and details of Earth’s orbit, because those seem to have been major drivers of the ice ages [pdf] and other climate changes before the rise of industrial civilization. Climatologists, therefore, do take them into account in their models. [pdf] But in defiance of the naysayers who want to chalk the recent warming up to natural cycles, there is insufficient evidence that enough extra solar energy is reaching our planet to account for the observed rise in global temperatures.

The IPCC notes that between 1750 and 2005, the radiative forcing from the sun increased by 0.12 watt/square-meter—less than a tenth of the net forcings from human activities [pdf] (1.6 W/m2). The largest uncertainty in that comparison comes from the estimated effects of aerosols in the atmosphere, which can variously shade Earth or warm it. Even granting the maximum uncertainties to these estimates, however, the increase in human influence on climate exceeds that of any solar variation.

Moreover, remember that the effect of CO2 and the other greenhouse gases is to amplify the sun’s warming. Contrarians looking to pin global warming on the sun can’t simply point to any trend in solar radiance: they also need to quantify its effect and explain why CO2 does not consequently become an even more powerful driver of climate change. (And is what weakens the greenhouse effect a necessary consequence of the rising solar influence or an ad hoc corollary added to give the desired result?)

The most recent contrarian fad is based largely on work by Henrik Svensmark of the Technical University of Denmark, who argues that the sun’s influence on cosmic rays needs to be considered. Cosmic rays entering the atmosphere help to seed the formation of aerosols and clouds that reflect sunlight. In Svensmark’s theory, the high solar magnetic activity over the past 50 years has shielded Earth from cosmic rays and allowed exceptional heating; but now that the sun is more magnetically quiet again, global warming will reverse. Svensmark claims that, in his model, temperature changes correlate better with cosmic ray levels and solar magnetic activity than with other greenhouse factors.

Svensmark’s theory has so far not persuaded most climatologists, however, because of weaknesses in its evidence. In particular, there do not seem to be clear long-term trends in the cosmic ray influxes or in the clouds that they are suppose to form, and his model does not explain (as greenhouse explanations do) some of the observed patterns in how the world is getting warmer (such as that more of the warming occurs at night). For now, at least, cosmic rays remain a less plausible culprit in climate change.

And the apparent warming seen on Mars? It is based on a very small base of measurements, so it may not represent a true trend. Too little is yet known about what governs the Martian climate to be sure, but a period of heavy dust storms on the planet that made its surface relatively dark might have increased the amount of absorbed sunlight and raised temperatures.

Claim 5: Climatologists conspire to hide the truth about global warming by locking away their data. Their so-called “consensus” on global warming is scientifically irrelevant because science isn’t settled by popularity.

It is virtually impossible to disprove accusations of giant global conspiracies to those already convinced of them (can anyone prove that the Freemasons and the Roswell aliens aren’t involved, too?). Let it therefore be noted that the magnitude of this hypothetical conspiracy would need to encompass many thousands of uncontroversial publications and respected scientists from around the world, stretching back through Arrhenius and Tyndall for almost 150 years. (See this feature on “Carbon Dioxide and Climate,” by Gilbert N. Plass, from Scientific American in July 1959.) It is also one so powerful that it has co-opted the  official positions of dozens of scientific organizations including the U.S. National Academy of Sciences, the Royal Society, the American Association for the Advancement of Science, the American Geophysical Union, the American Institute of Physics and the American Meteorological Society.

If there were a massive conspiracy to defraud the world on climate (and to what end?), surely the thousands of e-mails and other files stolen from the University of East Anglia’s Climatic Research Unit and distributed by hackers on November 20 would bear proof of it. So far, however, none has emerged. Most of the few statements that critics claim as evidence of malfeasance seem to have more innocent explanations that make sense in the context of scientists conversing privately and informally. It is deplorable if any of the scientists involved did prove to manipulate data dishonestly or thwart Freedom of Information requests; however, it is currently unclear whether that ultimately happened. What is missing is any clear indication of a widespread attempt to falsify and coordinate findings on a scale that could hold together a global cabal or significantly distort the record on climate change.

Climatologists are frequently frustrated by accusations that they are hiding their data or the details of their models because, as Gavin Schmidt points out, much of the relevant information is in public databases or otherwise accessible—a fact that contrarians conveniently ignore when insisting that scientists stonewall their requests. (And because nations differ in their rules on data confidentiality, scientists are not always at liberty to comply with some requests.) If contrarians want to deal a devastating blow to global warming theories, they should use the public data and develop their own credible models to demonstrate sound alternatives.

Yet that rarely occurs. In 2004 historian of science Naomi Oreskes published a well-known analysis of the peer-reviewed literature on global warming, “The Scientific Consensus on Climate Change.” Out of 928 papers whose abstracts she surveyed, she wrote, 75 percent explicitly or implicitly supported anthropogenic global warming, 25 percent were methodological or otherwise took no position on the subject—and none argued for purely natural explanations. Notwithstanding some attempts to debunk Oreskes’ findings that eventually fell apart, her conclusion stands.

Oreskes’ work does not mean that all climate scientists agree about climate change–obviously, some do not (though they are very much a minority). Rather, the meaningful consensus is not among the scientists but within the science: the overwhelming predominance of evidence for greenhouse-driven global warming that cannot easily be overturned even by a few contrary studies.

Claim 6: Climatologists have a vested interest in raising the alarm because it brings them money and prestige.

If climate scientists are angling for more money by hyping fears of climate change, they are not doing so very effectively. According to a 2006 Government Accountability Office study, between 1993 and 2004, U.S. federal spending on climate change rose from $3.3 billion to $5.1 billion—a 55 percent increase. (Total federal nondefense spending on research in 2004 exceeded $50 billion.) However, the research share of that money fell from 56 percent to 39 percent: most of it went to energy conservation projects and other technology programs. Climatologists’ funding therefore stayed almost flat while others, including those in industry, benefited handsomely. Surely, the Freemasons could do better than that.

 

 

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