Climate “skeptics,” more suitably referred to as denialists, attempt to advance their cause in two principal ways:
(1) present outdated or imaginary technical arguments;
(2) claim conspiracy on the part of climate science research organizations and climate scientists, to whom they often refer in derogatory ad-hominem terms.Using terms such as “alarmism,” denialists do not appear to recognize the professional and ethical responsibility of scientists to alert society to dangers, whether of natural or anthropogenic origin, such as looming epidemics, ultraviolet and cosmic radiation, smoking-related cancer, ozone depletion or the climate impasse.
Many of the denialists have been supported by fossil fuel interests. On 4.11.2006, Bob Ward, Senior Manager, Policy Communication, British Royal Society, addressed to a major oil company, stating, “… I am writing to express my disappointment at the inaccurate and misleading view of the science of climate change that these documents present .… leaves readers with such an inaccurate and misleading impression of the evidence on the causes of climate change that is documented in the scientific literature… My analysis indicates that (your company) provided more that $2.9 million to organizations in the United States which misinformed the public about climate change through their websites.”One example is the film “The Great Global Warming Swindle”, screened by the Australian Broadcasting Corporation on the 12 July, and which does not display temperature records since the 1980s onward, omitting the critical evidence for greenhouse-driven climate change during the last 30 years when temperatures rose by ~0.6oC, whereas solar radiation oscillated at +/-0.2 Watt/m2.Denialists repeatedly attack what they call “science by consensus”. However, science, a self-correcting method, advances by trial and error.
“But if … skeptics were successful in stopping policies to cut emissions and the IPCC projections turn out to be correct, then environmental catastrophe will follow and millions of people will die. Do they lose sleep over this? Do they worry about how their grandchildren will see them? Or are they so consumed by their crusade that they know they will never be proven wrong?”
Most arguments made by climate change deniers can be shown to be false:
1. A common argument relates to historical and geological warm periods, suggesting the current global warming is of natural rather than anthropogenic origin. However, studies of historical temperatures based ice cores, tree rings, corals, pollen, cave deposits, sediments and other proxies indicate late 20th to early 21st century mean temperatures exceed those of the Medieval Warm Period (1000 – 1150AD) by 0.5oC. Another argument is that the current warming represents a recovery from the “little ice age” (1600 – 1700AD), a period related to a near-cessation of sun spot activity. However, sunspot activity has peaked by the mid-20th century, whereas temperatures continue to rise by ~0.6oC.
2. References by denialists to past natural climate changes, including the Emian (124,000 years-ago) when temperatures exceeded 20thc century levels by ~1oC, or the mid-Pliocene (3 Ma) when temperatures were + 2 to 3oC higher, miss the point. It is no more warranted to artificially raise atmospheric temperatures than, for example, destroy the ozone layer or lower the pH of the ocean just because such changes have taken place in the past!
3. Denialists often attribute global warming to an increase in solar radiation. An increase in sunspot activity toward the mid-20th century is correlated with a rise in insolation by about 0.06 – 0.30 Watt/m2, with a mean of 0.12 Watt/m2, an order of magnitude lower than caused by GHG radiative forcing of ~1.6 Watt/m2. Concomitant rise in insolation, the effect of aerosols and rising GHG during ~1950 – 1975 partly masked the GHG effect, which is clearly decoupled from the solar effect from about 1975. Warming of the upper troposphere, cooling of the upper atmosphere (in part related to ozone depletion), surface warming during winters and nights are consistent with GHG effects rather than solar effects.
4. As it has been suggested cosmic ray activity helps nucleate low-level clouds (Svensmark, 2007), some denialists invoked low cosmic rays to account for global warming. As an inverse relation occurs between peak sun spot activity and cosmic ray activity, this implies an increase in solar radiation parallel with global warming, but such increase has not been recorded from the mid-20th century (Solanki, 2002, 2004). Claims of correlations between paleo-temperature variations based on δ18O and cosmic ray effects read from meteorites (Shaviv and Veizer, 2003) have been refuted by Rahmstorf et al. (2004), who showed the data have been de-trended.
5. In the absence of a common extraterrestrial cause, claims by some denialists as if Earth shares climate changes with Mars and Venus remain unsupported.
6. Another argument by denialists relates to an apparent lack of a top-tropospheric “hot spot” (TTHS) (Singer and Douglass, 2004), an expected consequence of global warming. However, the TTHS has been in fact identified (http://www.realclimate.org/index.php/archives/2008/05/tropical-tropopshere-ii/.)(seehttp://www.abc.net.au/ unleashed/stories/ s2323407.htm).
7. A common argument by denialists is a concentration of climate measurements around cities and conurbations. This argument, which may have had some validity during the earliest days of measurements, is negated by the global distribution of ground measurements, weather balloon measurements and satellite-based measurements over the world’s continents, oceans and polar regions. Hansen et al. (2001) estimate the effect of urban heat sources at ~0.1oC (http://earthobservatory.nasa.gov/ Features/ GISS.Temperature/printall.php)
8. Referring to annual to multi-annual mean temperature oscillations related to the ENSO cycle (El-Nino 1998, 2002, 2007; La-Nina 2000, 2003, 2006, 2008), denialists claim the Earth has been cooling since 2002. As shown by global temperature trends the decline in the mean rate of temperature rise during 2000 – 2007 relative to 1975 – 2000 correlates with the effects of lower sun spot activity, and in 2003 and 2006 with the La-Nina. In so far as ice sheet melting may result in retardation of the Gulf Stream, a lull in warming, or even cooling of the North Atlantic Ocean, may be expected as a stage in global climate impasse, possibly reflected by projection of Keenlyside et al. (2008). The critical manifestation of global warming comes from the poles, where mean temperatures have increased by up to 4oC.
9. Denialists often criticize computer models, betraying a misunderstanding of their nature which, as in other field in science, constitute tools used to test matches between direct measurements, calculations and interpretations. More than 20 independently developed climate models are consistent with directly observed trends when the effect of GHG forcing is included in the calculations.
10. Claims CO2 increases are beneficial as plant food overlook the drying/burning consequences of the extensive droughts associated with polar-ward migration of climate zones, in particular in mid-latitudes, as in the Murray-Darling Basin. Some crops which may grow faster under elevated temperature also need water, an increasingly scarce commodity in these latitudes. Where precipitation increases due to expansion of the tropics, it is often associated with devastating tropical cyclones. In so far as some agricultural advantages may arise in northern latitudes from thawing of sub-Arctic permafrost, they are more than negated by the release of methane from the permafrost as a powerful feedback effect of global warming.
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