The Earth is heating up, and human beings burning fossil fuels are the cause. It’s not ocean warming that’s causing it, it’s not cosmic rays, it’s not variations in the Earth’s orbit and tilt toward the sun (Milankovitch cycles), it’s not solar irradiance – it’s us. But there is a very vocal minority that refuses to believe global heating (the severity of the problem requires more urgent language, and besides, 105 degrees isn’t warmer than 100, it’s hotter) is real.
Global heating deniers fall back on a variety of claims in order to buttress their position. These claims vary from logical fallacies to pseudoscience to poor math to scientifically valid but disproved hypotheses. Yet every single claim against global heating I’ve found has been debunked at one time or another, and at this point, the only hypothesis that fits all the data is that human civilization is heating up the planet.
I’ve gathered the top anti-global heating claims into the following list and provided a reasonably thorough debunking for every one. I’ve focused only on the scientific claims because they can be addressed with data, and there are probably a few I’ve missed that I’ll happily tackle in the comments as needed. There were a number of claims that tied together, so I addressed them all at once rather than independently. And if I could quote references that weren’t the IPCC Working Group I: The Physical Basis for Climate Change detailed report (not the summary for policymakers), I did – too many people reject the IPCC out of hand and it’s always better to use the original source if it’s available.
DENIAL CLAIM #1: The source of all the CO2 in the air is outgassing from the mantle (Source: George V. Chilingar’s (of the Department of Civil and Environmental Engineering, University of Southern California) paper titled On global forces of nature driving the Earth’s climate. Are humans involved?).
Debunking: This theory proposes that the bulk of the CO2 in the air and oceans today is a direct result of outgassing from the Earth’s mantle, not from human consumption of fossil fuels. The key piece is this:
Recalculating this amount into the total anthropogenic carbon dioxide emission in grams of CO2, one obtains the estimate 1.003×1018 g, which constitutes less than 0.00022% of the total CO2 amount naturally degassed from the mantle during geologic history. Comparing these figures, one can conclude that anthropogenic carbon dioxide emission is negligible (indistinguishable) in any energy-matter transformation processes changing the Earth’s climate.(emphasis mine)
In essence, Prof. Chilingar is claiming that anthropogenic (human sourced) CO2 has had a negligible impact on the atmosphere over the last hundred years or so and will have no impact over next few hundred years because we are adding a fraction of the total CO2 outgassed by the mantle over the course of the last 4.5 billion years. Unfortunately, as W. Aeschbach-Hertig, of the Institute of Environmental Physics, University of Heidelberg, says in his rebuttal, there is at least one major error, like the fact that the modern atmosphere had only about 3×1018 g of CO2 in it (not the full amount every outgassed by the mantle, which is 100,000x greater), so adding 1×1018 g of new CO2 is a massive percentage change (~33%). In addition, time scales matter here – increasing the amount of CO2 by 33% over the course of a few decades would overwhelm any system (like the Earth’s climate) that has a time constant of centuries. And the fact that Prof. Chilingar concluded that direct heating of the air by human activity couldn’t possibly cause the observed heating – when every serious climate scientist (of which Prof. Chilingar is not – he’s a petroleum scientist) says that the greenhouse effect is the cause, not direct heating by human activity. (source above)
DENIAL CLAIM #2: The source of the CO2 in the air is thermal heating of the ocean causing dissolved gases like CO2 to come out of solution and enter the atmosphere (Source: “Apocalypse Canceled”, by Christopher Monckton as well as others).
Debunking: The main idea here is that, if you overlay CO2 concentration data from ice cores with temperature data, you notice that CO2 has always lagged after temperature. Because hot water cannot store as much dissolved gas as cold water can (this is fundamental physics, the data could lead people to reasonably conclude that the ocean is the source of the CO2 in the air and always has been. Unfortunately, there are two main problems with this argument. The first is the aforementioned “predictive appeal to history” logical fallacy – just because CO2 has lagged after temperature in the past doesn’t mean it always will (or is this time). The second is that this theory has been tested and been found incorrect.
If heating oceans were the source of the CO2 in today’s atmosphere, we could expect a historical trend of dropping CO2 concentrations in the oceans, yet we see the exact opposite – CO2 concentrations in the ocean have increased, driving down ocean pH (making it more acidic) and will continue to do so (source: Impacts of Anthropogenic CO2 on Ocean Chemistry and Biology, NOAA). In addition, if a hotter ocean were the cause of CO2, we would also see increasing concentrations of other dissolved gases such as oxygen, yet the concentration of oxygen in the atmosphere is actually decreasing, not increasing (sources: Environmental Chemistry.com’s CO2 Pollution and Global Warming page and IPCC Working Group 1 Report, Chapter 2, pages 138-139).
DENIAL CLAIM #3: We don’t know for sure where the added CO2 in the atmosphere is coming from, but it’s not from human consumption of fossil fuels (Source: distillation of multiple people’s claims at Wikipedia.org).
Debunking: We know exactly where the added CO2 is coming from, and it most certainly is from human activity (mostly the burning of fossil fuels, but some is from industry and slash-and-burn deforestation for agriculture). Carbon has two stable isotopes (atomic weights), C12 and C13. Plants prefer to use C12 over C13 (it takes slightly less energy to bond to C12 than to C13), so the naturally occurring ratio of the two isotopes is skewed toward C12 in plants. All fossil fuels were originally plants, and so if the C12/C13 ratio in the atmosphere is changing toward increased concentrations of C12, then the source of the new CO2 must be plants. In addition, since animal respiration isn’t enough to skew the C12/C13 ratio and simultaneously affect the concentration of CO2 and oxygen in the atmosphere, the source must be fossil fuels. (sources: Environmental Chemistry.com’s CO2 Pollution and Global Warming page and IPCC Working Group 1 Report, Chapter 2, pages 138-139)
DENIAL CLAIM #4: CO2 rates are rising only 0.38% per year, not the 1% per year called out in the Third IPCC assessment report (TAR) (Source: “Apocalypse Canceled”, by Christopher Monckton as well as others).
Debunking: Basically, this claim was used by Mr. Monckton to attack the validity of the TAR’s assessment. I was unable to find the exact data that Mr. Monckton used, so I’ll use the fourth assessment’s (AR4) data to make a point about how this error could have been made by Mr. Monckton. The average rate of change of the atmospheric concentration of CO2 over the last 250 years has been about 0.14% per year (100 ppm change, ~280 ppm starting point, and the change occurred over 250 years), but rate of change has not been constant. In fact, the average rate of change since ~1960 has been about 0.50% per year, and the average rate of change since 1995 has been about 0.68% per year. And if you look at the middle left graph in Figure 3.2 of the IPCC Working Group 1 TAR Chapter 3, on page 201, you’ll see that the actual graph of the data looks almost identical to the equivalent IPCC AR4 graph (Figure 1, FAQ2.1, page 135) and the description above. In the case of Mr. Monckton’s data, I suspect that he assumed a linear progression where the rate of change has been accelerating rather than remaining constant. (Source: IPCC Working Group 1 Report, Chapter 2, , page 137)
DENIAL CLAIM #5: CO2 is a sufficiently weak greenhouse gas that it could not be responsible for the level of climate change being modeled and observed (Source: distillation of multiple people’s claims at Wikipedia.org).
Debunking: CO2 is a relatively weak greenhouse gas compared to methane or nitrous oxide. If we use the radiative forcing (RF) values from Table 2.1 (page 141) of the IPCC Working Group 1 Report, Chapter 2 and assume a linear relationship between RF and concentration in the atmosphere, CO2 is about 0.0044 Watts per square meter per ppm (Wm-2ppm-1), compared to 0.2706 Wm-2ppm-1 for methane and 0.5016 Wm-2ppm-1 for nitrous oxide. This means that methane is about 62x as powerful a greenhouse gas than carbon dioxide, and nitrous oxide is about 114x as powerful as CO2. The problem is that CO2 concentration in the atmosphere is measured at 379 ppm, while methane is only 1.774 ppm (1,774 ppb), and nitrous oxide is only .319 ppm (319 ppb). Because there is 213x more CO2 than methane, and 1188x more CO2 than nitrous oxide, the fact that CO2 is a relatively weak greenhouse gas is more than compensated for by concentration in the atmosphere. (Source linked above)
DENIAL CLAIM #6: There is no correlation between CO2 in the atmosphere and the temperature, since 450 million years ago was the coldest in 0.5 billion years and also had the highest CO2 concentrations (Source: distillation of multiple people’s claims at Wikipedia.org).
Debunking: There is at least one peer-reviewed paper proposing that the rise of the Appalachian Mountains 450 million years ago caused the Ordovician ice age period 450 million years ago. The idea is that the brand new Appalachian Mountains eroded so fast, and in the process pulled so much CO2 out of the air, that it caused global temperatures to plummet. (Source: Appalachian Mountains, Carbon Dioxide Caused Long-ago Global Cooling) Apparently the ice age period we’re in/exiting now is believed to have been caused by rise of the Himalaya Mountains through the same weathering CO2 capture process.
DENIAL CLAIM #7: The Medieval Warm Period/Medieval Climate Anomaly (MWP) was warmer than conditions today (Source: “Apocalypse Canceled”, by Christopher Monckton among others).
Debunking: This claim has been addressed repeatedly, and every example I found basically summarized down to this: The evidence used by most scientists that believe this claim is anecdotal at best and that while this evidence applies regionally to the area between Greenland and the Ural Mountains, there is not yet enough evidence to support this claim on a hemispherical basis, never mind a global basis. In addition, there is a chance that the MWP and the Little Ice Age (see Denial Claim #9 below) are both artificial and arbitrary and are actually representative a gradual cooling trend as opposed to a periodic oscillation in the global temperature. Check through all the sources for more detailed information. (Sources: Climate of the Last Millennium, by Raymond S. Bradley, Climate System Research Center, Dept. of Geosciences, University of Massachusetts, Amherst, IPCC Working Group 1 Report, Chapter 6, Figure 6.10 and Box 6.4, pages 467-469, Climate Over Past Millennia, by P.D. Jones and M.E. Mann, Medieval Warm Period and the Little Ice Age Myths)
DENIAL CLAIM #8: The MWP has been ignored in order to produce the desired conclusion (Source: “Apocalypse Canceled”, by Christopher Monckton as well as others).
Debunking: Even if this were true in the past (and the sources for Claim #7 above show it has been addressed repeatedly since the release of the TAR), the IPCC Working Group 1 Report, Chapter 6, Figure 6.10 and Box 6.4, pages 467-469 addresses this specifically. In essence, there is statistical evidence that the MWP was not warmer than the last 25 years (since 1980), but there are enough errors in the MWP data to warrant additional research into the scope (Europe? The entire Northern Hemisphere? Global?) and magnitude of the MWP. (source linked above)
DENIAL CLAIM #9: The temperatures we’re experiencing in the later part of the 20th century are a result of the global climate finally coming out of the Little Ice Age (Source: distillation of multiple people’s claims at Wikipedia.org).
Debunking: The Little Ice Age is a period of significant cooling in Europe, but there are questions as to whether this known regional change was truly global in dimension. However, if you look at the graph of the temperature data for the last 2000 years, there is no period where the reconstructed global temperatures have changed at a faster rate than in the last 50 years or so. I refer people to the ;IPCC Working Group 1 Report, Chapter 6, Figure 6.10 and Box 6.4, pages 467-469, but also to this NCAR press release that verifies that the basic conclusions of the original “hockey stick” remain accurate even using multiple different models.
DENIAL CLAIM #10: There was a significant period of global cooling between the 1940s and the 1970s. This cooling period existed as anthropogenic CO2 levels were rising significantly. If anthropogenic CO2 is more important than natural drivers, then this cooling period would not exist, yet it does (Sources: produced by Rcronk in the comments to Eastern seaboard of the United States to be much hotter, but also made in the Wikipedia.org claims).
Debunking: That this cooling period existed and was global in scope is not disputable as the scope of the MWP is – scientists were directly monitoring temperatures globally by this point, and these three decades were cooler than the decades preceding them and dramatically cooler than recent decades. So what caused the cooling?
First, there is a correlation between sunspots and solar irradiance (output) on the Earth. During this period, sunspots were less common and there was less solar energy reaching the Earth, allowing it to cool slightly. Second, there were several volcanic eruptions that released massive amounts of sulfur dioxide into the atmosphere. Sulfur dioxide is an aerosol that forms droplets of sulphuric acid in the high atmosphere and reflects solar energy back into space, so these two volcanic eruptions had some short- to medium-term effects. In addition, prior to the 1970s there were limited pollution controls, allowing pollutant aerosols to act as coolants via reflection of solar radiation. Ultimately, though, it is believed that sometime after 1970 the concentration of CO2 rose to the point that solar forcing was no longer the dominant climate factor, anthropogenic CO2 was. (Sources: Do Models Underestimate the Solar Contribution to Recent Climate Change?, Swindled!)
DENIAL CLAIM #11: Cosmic rays (very high energy particles) striking the Earth’s atmosphere is the cause of global heating (Source: distillation of multiple people’s claims at Wikipedia.org).
Debunking: According to this theory, cosmic rays are responsible for cloud cover – fewer cosmic rays means fewer clouds and less cooling in the summer (clouds reflect the energy) and more heating in the winter (as clouds hold heat in). Unfortunately, there doesn’t appear to be any statistically significant trend in the number of cosmic rays hitting the Earth, and the few experiments performed to date appear to be stricken with error or a failure to address key points. This could be an aggravating factor, but is highly unlikely to be the primary source of global heating. (Sources: No Link Between Cosmic Rays and Global Warming, Cosmic Rays and Global Warming, Recent Warming but No Trend In Galactic Cosmic Rays)
DENIAL CLAIM #12: The Stefan-Boltzmann Law (the relationship between radiation and temperature of an ideal “black body” radiator) breaks the calculations required to make global heating work (Source: “Apocalypse Canceled”, by Christopher Monckton as well as others).
Debunking: This issue was the hardest to make heads or tails of, because the only people who really use it are deniers. That said, Mr. Monckton claims that the real value of lambda (the response of the Earth to radiative forcing) of between 0.22 and 0.33 C/W. But this number is only valid for an ideal black body model of the Earth, and the Earth is not even remotely close to a black body. Unfortunately, because I can’t find examples of the math involved to walk through it, I can’t say that this claim has been as well debunked as I’d like it to be, and as most climate scientists claim it is. (Source: Cuckoo Science)
DENIAL CLAIM #13: Using computer models is inherently inaccurate, especially of long-term changes in a system as complex as the Earth’s global climate (Source: Pretty much all of the deniers use this one, so there are more sources than I care to link to directly).
Debunking: Models are inherently inaccurate – anyone who tells you otherwise is trying to sell you a bad modeling software package. However, models can be made to accurately average out to something that represents reality, and this is the case with the IPCC models. I suggest that everyone read IPCC Working Group 1 Report, Chapter 8, FAQ 8.1, pages 600-601 and IPCC Working Group 1 Report, Chapter 9, page 684 to get a better understanding of how the models work, and the fact that models without anthropogenic CO2 simply don’t match the actual measured temperature changes.
DENIAL CLAIM #14: The Earth hasn’t warmed by the expected amount predicted in the IPCC TAR, and papers have suggested that oceanic storage of heat is the reason. However, the only part of the ocean that matters as a “thermal sink” for atmospheric heating is the top few meters and yet the calculations performed require that 1.25 miles of ocean are available as a “sink” to make the math work out. Unfortunately, deep ocean temperatures haven’t changed at all (Source: “Apocalypse Canceled”, by Christopher Monckton).
Debunking: First, let’s talk about what depths matter. It’s true that only the top 90 meters or so of the ocean matters to short-term absorption of heat, but because of oceanic currents, the entire ocean does turn over eventually, if very slowly. So the entire ocean must be modeled in order to understand just what the effects of the oceans actually are. Second, the IPCC TAR had to use a depth of 3000 m in order to correctly reconstruct existing temperature data using models, but the latest IPCC report (AR4) uses a depth of 700 m instead, with data correlations between the sea surface temperature, the 0-700 m ocean depth zone, and then down to 3000 m as well. These correlations were not possible back in 2001 when the TAR was released due to lack of data, and the data has significantly improved in the years since. Finally, most of the increase in the temperature of the ocean has bee in the top 300-700 m, and so no, the deep ocean temperature hasn’t changed a lot. Given that the time scales of interest when talking about the deep ocean are in the range of decades to centuries, it’s not a surprise and totally expected. (Sources: NOAA Office of Climate Observation: The Role of the Ocean in Climate, Warming of the World Ocean, 1955-2003, S. Levitus, J. Antonov, and T. Boyer)
DENIAL CLAIM #15: The ocean has already begun to cool as expected given recent changes in solar output, cosmic solar rays, etc. (Source: “Apocalypse Canceled”, by Christopher Monckton).
Debunking: A 2006 paper by John M. Lyman, Josh K. Willis, and Gregory C. Johnson published in Geophysical Research Letters suggested that the oceans had lost a massive amount of heat (~20% of all the heat it had absorbed since the 1950s) without the heat apparently going anywhere. This was latched on to by many global heating deniers to suggest that the ocean had begun to cool as required by numerous suggested methods to account for purely naturally-driven global heating, or that the estimates of ocean heating were just plain wrong. Unfortunately, Dr. Lyman and his colleagues discovered that, while they’d accounted for measurement errors, they’d missed measurement biases (deterministic offsets in temperature inherent to the equipment measuring it) in their measurement devices, and the data will have to be corrected to account for this bias. Until then, however, there is no reason to believe that the unexpected cooling will actually be anything more than a glitch in need of correction. (Source: Correction to “Recent Cooling of the Upper Ocean”)
DENIAL CLAIM #16: Global heating isn’t actually happening because satellite measurements of tropical temperatures have not been rising like directly-measured temperatures in the tropics (Source: distillation of multiple people’s claims at Wikipedia.org).
Debunking: The satellites used to measure tropical temperatures remotely were discovered to have been drifting in their orbit, producing temperature measurements that were not during the day as expected, but rather during the night, confusing the cooler evening and nighttime temperatures with warmer daytime temperatures. The paper this comes from is “The Effect of Diurnal Correction on Satellite-Derived Lower Tropospheric Temperature” by Carl A. Mears and Frank J. Wentz of Remote Sensing Systems. Unfortunately, there is not a .pdf of this document available that may be freely distributed. However, this was reported in U.S.A Today and Live Science, and if you search Google for “satellite balloon data error global warming” you’ll find a lot more.
DENIAL CLAIM #17: Some deniers don’t directly dispute that global heating is happening or that humans are the cause. Instead, they claim that global heating might just be good for the human race (Source: distillation of multiple people’s claims at Wikipedia.org).
Debunking: The effects of global heating have been investigated by many people and organizations with specific concerns in mind, ranging from the economy to public health to population migrations to political stability. Below is a sampling of the organizations who believe that global heating will not be good for the world and why.
- The Pew Center on Global Climate Change published “U.S. market consequences of global climate change in April 2004 where they estimated that global heating would be, using the most optimistic assumptions, a temporary boost to the U.S. economy by 0.7 to 1% by 2100, but that the most pessimistic assumptions would produce a reduction in GDP of approximately 3.0%. In addition, the benefits are almost exclusively in the agriculture and energy sectors and increasing temperature will ultimately reverse the gains in both sectors.
- According to Climate Change 2007: Impacts, Adaptation and Vulnerability, Working Group II Contribution to the Intergovernmental Panel on Climate Change Fourth Assessment Report – Summary for Policymakers (the full report is not yet available online), droughts will become more common as freshwater from melt and precipitation decreases, 20-30% of plant and animal species will be at increased risk of extinction and acidification of the ocean will adversely affect marine ecosystems, global agricultural productivity will increase slightly and then decrease as temperatures continue to rise, coastal flooding will cause serious problems (especially in Asia), and developing countries will be heavily hit by droughts, disease, and rising sea levels
- Lloyd’s of London, a major global insurance company and hardly a hotbed of liberal activism, released this 360 Risk Report titled “Climate Change: Adapt or Bust”. The gist of the report is that climate change is going to cause major losses to insurers if the risks aren’t managed carefully, and that the risks must be managed by working with businesses and governments as well as by updating internal risk models to account for a changing global climate.
- The CNA Corporation released a report on “National Security and the Threat of Global Climate Change.” The report is somewhat alarmist and the time scales described may be too aggressive, but the point that global heating will cause significant instability and impact U.S. national security is valid nonetheless.
- In a Pentagon report titled “An Abrupt Climate Change Scenario and Its Implications for United States National Security,” the authors propose an abrupt climate change situation that is unlikely but plausible and that results in massive food shortages, disruptions in energy supplies, droughts, and possibly even wars over access to fresh water, mass population migrations, and energy.
At one point or another, each of these claims represented a real problem with the science of global heating. But no longer – the scientific evidence has become overwhelming. However, it’s the minority composed of global heating deniers who continue to hunt for flaws in climate science, so the deniers serve a valuable scientific purpose – when they find a real hole, or just think they have, addressing their claims are what has made the science of global heating as bullet-proof as it now is.
It comes down to this simple fact: the overwhelming majority of the scientific evidence points to human-induced global heating, and every claim made by global heating deniers has been effectively debunked. And because the consequences of doing nothing are so severe, we must act now even as the data continues to improve – we can no longer afford to wait.
[Crossposted: The Daedalnexus]
NOTE: This post was inspired by a blog Whythawk posted a couple of weeks ago entitled Life Earth will end climate change the way Live Aid ended poverty in Africa – Er… where one of the comment posters, “2008Voter”, posted the links to some of the sources used for this blog.