According to popular belief, recent global warming has been caused largely by greenhouse gases, primarily CO2, accruing in the atmosphere, and man is responsible for most of the ~120 ppm increase in CO2 over the last 100 years. This article cites a number of recent peer-reviewed scientific papers, and finds that contrary arguments by a growing body of scientists are generally supported by better empirical data than those that favour the ‘anthropogenic warming’ hypothesis. These arguments invoke the effects of solar irradiance and ocean–atmosphere interactions, both of which have been shown to have warming effects at least as great as those claimed for CO2, and to be based on sound, well-understood scientific theory. Furthermore, the global warming models used by the Intergovernmental Panel on Climate Change (IPCC) and others have in some cases been shown to be incorrect and contrary to current temperature statistics. For these and other reasons, the CO2-driven, anthropogenic warming hypothesis is regarded by many as suspect and lacking in empirical evidence. The difficulty of refuting this popular hypothesis is exacerbated by the IPCC’s United Nations mandate to advise governments on the severity of man-made global warming, a mandate that they have followed faithfully, encouraging the emergence of a large body of funded research that supports their view. This presents a problem for global society, as the human-caused warming scenario diverts attention from other, at least equally serious environmental impacts of our industrial society. Recently, however, there appears to be a tilting of public opinion away from global warming alarmism, which may fundamentally affect the direction of the climate change debate.
Selon la croyance populaire, le réchauffement climatique actuel aurait été causé en grande partie par des gaz à effet de serre, principalement le CO2 s’accumulant dans l'atmosphère et, c’est l'homme qui serait à l’origine de l’augmentation de ~ 120 ppm de la teneur en CO2 au cours du dernier siècle. Dans le présent article on cite un certain nombre d’articles scientifiques à comité de lecture, et on conclut que des arguments contraires présentés par un nombre croissant de scientifiques, sont généralement soutenus par de meilleures données empiriques que celles qui favorisent l’hypothèse d’un « réchauffement anthropogénique ». À partir d’une théorie scientifique bien fondée, ces arguments montrent que les effets du rayonnement solaire et des interactions océan-atmosphère ont un effet climatique de réchauffement au moins aussi important que celui imputé au CO2. En outre, il a été démontré que les modèles de réchauffement de la planète utilisés par le Groupe d'experts intergouvernemental sur les changements climatiques (GIEC) et d'autres sont, dans certains cas avérés erronés et en contradiction avec les statistiques actuelles sur la température. Pour ces raisons et d'autres, nombreux sont ceux qui considèrent que l’hypothèse d’un réchauffement climatique anthropogénique par le CO2 est sujette à caution et manque de preuves empiriques. À noter qu’il est d’autant plus difficile de réfuter cette hypothèse populaire que l’Organisation des Nations Unies a confié au GIEC le mandat de conseiller les gouvernements sur la gravité du réchauffement climatique anthropogénique, mandat dont il s’acquitte avec application, ce qui favorise l'émergence d'un important volume de recherches financées, qui tendent à confirmer leur point de vue. Cela pose un problème pour l’humanité entière, en ce que le scénario d’un réchauffement climatique anthropogénique détourne l'attention d’autres problèmes de notre société industriel qui ont des répercussions au moins aussi graves sur l'environnement. Récemment, cependant, il semble y avoir un basculement de l'opinion publique qui tend à remettre en question l'alarmisme ambiant sur le réchauffement climatique planétaire, ce qui pourrait affecter fondamentalement le sens du débat sur le changement climatique.
1 The term ‘global warming’ is commonly used by the media to mean ‘anthropogenic’ global warming; that is, warming caused by human activity. In this article, the writer has chosen to prefix ‘global warming’, where appropriate, by the terms ‘anthropogenic or ‘human-caused’ in order to avoid confusion.
2 We are led today by our media, governments, schools and some scientific authorities to believe that, through his CO2 emissions, man is entirely, or almost entirely, responsible for the modest, modulated rise in global temperature of about 0.7° C that has taken place over the past 100 years. We are told, and many sincere people believe, that if we continue on this path, the planet will experience escalating temperature and dangerous sea-level rise before the end of this century. Over the past 20 years or so, this has become so much a part of our belief system, that to challenge it is to be labelled a ‘denier’ and put in the same category as a member of the Flat Earth Society. Yet, even a cursory review of the peer-reviewed scientific literature will show that the popular anthropogenic global warming dogma is being questioned by hundreds of respected scientists. Furthermore, emerging evidence points directly to other natural phenomena as probably having greater effects on global temperatures than can be attributed to human-caused CO2 emissions. The disproportionate scientific weighting attributed to the anthropogenic warming interpretation, and the general public perception of its validity, could be a serious problem for society, as the human-caused global warming belief is diverting our attention from other, more serious anthropogenic effects such as pollution and depletion of our water resources, contamination of our food and living space from chemicals, and diminishing conventional energy resources.
3 The fact that the world has undergone cycles of warming and cooling has been known for a very long time, but the question as to man’s influence on climate did not become a hot debate until after the mid-twentieth century, when Revelle and Seuss (1957) first drew attention to the possible effect of greenhouses gases (particularly CO2) on the earth’s temperature. Subsequent studies pointed to the increase in atmospheric CO2 from roughly 0.025% to 0.037%, or 50%, over the past 100 years. Much was made of the apparent but crude covariance of atmospheric CO2 and global temperature, and the conclusion was drawn that man’s escalating carbon emissions are responsible for the late 20th century temperature rise. Anxiety was rapidly raised among environmentalists, and also attracted many scientists who found ready funding for studies aimed at better understanding the problem. However, scientists soon encountered three important difficulties:
4 It is likely that the cyclical warming and cooling of the earth results from a number of different causes, none of which, taken alone, is dominant enough to be entirely responsible. The more important ones are solar changes (including both irradiance and magnetic field effects), atmosphere–ocean interaction (including both multi-decadal climatic oscillations and unforced internal variability), and greenhouse gases. All of these factors have been discussed by IPCC, but the first two have been dismissed as negligible in comparison with the greenhouse-gas effect and man’s contribution to it through anthropogenic CO2. It is claimed (e.g. Revelle and Suess 1957) that the particular infrared absorption bands of CO2 provide it with a special ability to absorb and re-radiate the sun’s longer wavelength radiation, causing warming of the troposphere and an increase in high-altitude (cirrus) cloud, further amplifying the heating process. Detailed arguments against this conclusion can be found in Spencer et al. (2007) and Gerlich and Tscheuschner (2009). These scientists point out (among other arguments, which include the logarithmic decrease in absorptive power of CO2 at increasing concentrations), that clouds have poor ability to emit radiation and that the transfer of heat from the atmosphere to a warmer body (the earth) defies the Second Law of Thermodynamics. They argue that the Plank and Stefan-Boltzman equations used in calculations of radiative heat transfer cannot be applied to gases in the atmosphere because of the highly complex multi-body nature of the problem. Veizer (2005) explains that, to play a significant role, CO2 requires an amplifier, in this case water vapour. He concludes that water vapour plays the dominant role in global warming and that solar effects are the driver, rather than CO2. A comprehensive critique of the greenhouse gas theory is provided by Hutton (2009).
5 It is firmly established that the sun is the primary heat source for the global climate system, and that the atmosphere and oceans modify and redirect the sun’s heat. According to Veizer (2005), cosmic rays from outer space cause clouds to form in the troposphere; these clouds shield the earth and provide a cooling effect. Solar radiation, on the other hand, produces a thermal energy flux which, combined with the solar magnetic field, acts as a shield against cosmic rays and thereby leads to global warming. Figures 3 and 4 illustrate both the cooling by cosmic rays (cosmic ray flux, or CRF) and warming by solar irradiation (total solar irradiance, or TSI) in the long term (500 Ma) and short term (50 years), respectively. CRF shows an excellent negative correlation with temperature, apart from a short period around 250 Ma (Fig. 3). In contrast, the reconstructed, oxygen isotope-based temperature curve illustrates a lack of correlation with CO2 except for a period around 350 Ma.
6 Other studies have highlighted the overriding effect of solar radiation on global heating. Soon (2005) studied solar irradiance as a possible agent for medium-term variations in Arctic temperatures over the past 135 years, and found a close correlation in both decadal (5–10 years) and multi-decadal (40–80 years) changes (Fig. 5). As to the control on this variation, the indirect effect of solar irradiance on cloud cover undoubtedly results in modulations of the sun’s direct warming of the earth. Veizer (2005) estimated that the heat reflected by cloud cover is about 78 watts/m2, compared to an insolation effect of 342 watts/m2, a modulation of more than 25%. This contrasts with an IPCC estimate of 1.46 watts/m2, or about 0.5% of TSI, for the radiative effect of anthropogenic CO2 accumulated in the modern industrial era (IPCC 2001). Veizer concludes: "A change of cloud cover of a few percent can therefore have a large impact on the planetary energy balance."
7 In addition to solar insolation effects, the intensity of the Earth’s magnetic field (which deflects the charged particles that constitute cosmic rays) and associated sun-spot maxima are correlated with historic periods of global warming such as the Medieval Climate Optimum (Fig. 6), and typically occur mid-way between ice ages (Veizer 2005). Solar magnetic minima have accompanied global cooling, such as occurred during the Little Ice Age between 1350 and 1850 A.D. A proxy for sunspot activity prior to the start of telescope observations in 1610 can be reconstructed from the abundance of cosmogenic 10Be in ice cores from Antarctica and Greenland (Miletsky et al. 2004).
8 Global temperature oscillations have been evident in both geologic and recent times, with periods varying from a few years (mostly solar and lunar driven) up to 120 million years (galactic and orbital influences) (Plimer 2009). In addition, ocean– atmosphere interactions are implicated in the control of some shorter-period climatic oscillations. For example, McLean et al. (2009) have studied the El Niño Southern Oscillation (ENSO), a tropical Pacific ocean–atmosphere phenomenon, and compared the index of intensity (the Southern Oscillation Index, or SOI) with global tropospheric temperature anomalies (GTTA) for the 1960–2009 period (Fig. 7). McLean et al. (2009) concluded that "Change in SOI accounts for 72% of the variance in GTTA for the 29-year long record, and 68% for the 50-year record". They found the same or stronger correlation between SOI and mean global temperature, in which SOI accounted for as much as 81% of the variance in the tropics (Fig. 8). A delay of 5 to 7 months was deduced between the SOI maximum and the associated temperature anomaly. Volcanic influences on temperature are also evident (Figs. 7, 8), probably caused by the injection of sulphur dioxide into the stratosphere, where it is converted into sulphate aerosols that reflect incoming solar radiation (McLean et al. 2009). The GTTA nearly always falls in the year or two following major eruptions.
9 Both solar irradiation and ocean–atmosphere oscillations have therefore been demonstrated to have effects on global temperature of at least the same order of magnitude as the CO2 greenhouse gas hypothesis, and these alternative mechanisms are supported by well-documented empirical data. Nevertheless, the CO2 hypothesis, the theoretical basis for which is being increasingly challenged, remains the popular explanation for global warming in the public domain.
10 The main factors that have led to heated scientific controversy regarding the cause of the mild late 20th century global warming can be summarized as follows:
11 The following examines various scenarios of climate change policy and other events that may develop over the next 5 to 10 years:
12 Some of the wisest words on the subject of global warming were uttered by Pope Benedict XVI (quoted by Plimer 2009):
13 One positive outcome of the rise and fall of human-caused global warming furor may be the rejection of post-modern science in favour of a revival of the traditional scientific culture which defers strictly to empirical facts and experiments rather than computer models, and encourages the questioning of accepted theory by ‘thinking outside the box’. Nearly all the great scientific breakthroughs and truths in history have been won by the relentless application of empirical methodology in an atmosphere of lateral thinking. Skepticism is an essential element in the search for scientific truth. As explained by Nield (2010): "Those who pay scant attention to history often find themselves denying a revolutionary idea because ‘how can so many people have been so wrong for so long’ "and "The number of people who believe something has no bearing on its rightness".
14 In 1954 the famous Canadian geophysicist J. Tuzo Wilson abandoned his belief that continents formed from volcanic island arcs, in favour of the theory of continental drift, earlier espoused by Alfred Wegener. Wilson’s enthusiasm for the new hypothesis was such that he became known, in some circles, as the Father of Continental Drift; his reputation suffered not at all.
The author acknowledges reviews by Andrew D. Miall and Bob Carter, and some valuable suggestions from Geo-science Canada editor Reginald Wilson.
Norman Paterson is a Professional Engineer and Consulting Geophysicist with 60 years’ experience in Mineral and Environmental Geophysics. He obtained his Ph. D in Geophysics at the University of Toronto in 1955, and was elected Fellow, Royal Society of Canada in 1977. His work has taken him to 43 countries, where he has done pioneering work on groundwater exploration and management, as well as mineral and hydrocarbon exploration. He was inducted into the Canadian Mining Hall of Fame in 2002.