National Committees Earth System Science
‘THE GREAT GLOBAL WARMING SWINDLE’ TELEVISION PROGRAM: COMMENTS BY THE ACADEMY’S NATIONAL COMMITTEE FOR EARTH SYSTEM SCIENCE
12 July 2007
It is both exasperating and unfortunate when the media either exaggerate stories, sometimes to idiotic degrees, or air poorly-vetted and inaccurate presentations that are purported to provide journalistic balance. It has been so for global warming ever since the topic burst into the media in the late 1980s with images of floods, droughted crops, storms, lightning bolts, cracked clay pans, carcasses in deserts, and people in deck-chairs on the beach up to their necks in sea water. This has created vividly false impressions. Now the TV program ‘The great global warming swindle’ (aired on Australian Broadcasting Corporation television on 12 July 2007) presents a counter story with even greater, but opposite, exaggeration and inaccuracy. What can the man in the street make of this? How can the publics’ right to be well informed be addressed by such polarizing and incompatible presentations in the media? Is human-induced climate change the biggest threat to the world this century, or is it just a fraudulent claim by climate scientists trying to drum up research dollars?
Just as newspapers feel the imperative to grab the attention of potential readers with exaggerated headlines, so do cash-strapped researchers need to present convincing cases of the imperative of their research proposal to potential funding agencies. Scientists are regularly entreated by managers and even politicians not to be back-room wimps but to get out and ‘market’ themselves and their stories widely. But such pressures are tempered by self-regulation procedures in science. Research grant-bids and publications in most research journals are vetted by the peer review process. Several independent referees’ reports are considered before publication: it is a rare manuscript that gets through that process without being modified in response.
Although fashionable but incorrect ideas can have an impact on what is published, they only do so for a while as these ideas are constantly being modified through the scientific evaluation process. An important aspect of this system of scientific checks and balances is the challenge to every scientist to find evidence that disproves other people’s hypotheses – especially well-entrenched ones. That’s how science works – by refuting hypotheses. It is a major motivation in the conduct of science alongside the desire to produce something enduring and useful and to be recognised for it.
A third and related check is that it is a fundamental assumption in science that every hypothesis is an approximation to reality and that further work will displace such generalizations with more accurate ones. ‘The great global warming swindle’ is a slick, hyped-up, graphics-enhanced, deceptively fraudulent in parts, production focusing on a carefully selected subset of out dated hypotheses that for the most part have been shown by the scientific method to be unacceptable on evidence so far.
Challenges to the conventional scientific wisdom and current conclusions are critical to the health of science, as long as they themselves are scientifically well-founded and credible. When such challenges include distortions and falsehoods and are presented one-sidedly and uncritically in the public arena as if they are true, they can set-back finding the truth and timely political action. Most of the data and ideas presented in the program have been through the scientific review process and have been discredited.
Here we present a series of responses to key claims made in the original program shown in the UK. We believe the original program has been edited for Australian viewers.
Claim: Temperature has always been variable and has gone through much bigger changes in the geological past. The Medieval Warm Period was warmer than now. So what’s new?
The first sentence is true but not relevant. Past climate variability does not prove that the current rapid warming is not man-made. Over the last 4,000 years, during the period of human civilisation and urbanisation, global temperatures have been relatively stable by geological standards. Our modern infrastructure, agriculture and lifestyles are adapted to, and partly dependent on, those relatively stable temperatures. They are also adapted to the associated sea-level. If man-induced global warming causes much disruption, it will cost a great deal to adapt to the changes. To many people this matters. Owing to variability in climate change around the world, some people may nevertheless benefit from human-induced warming, for a while at least.
The warmth of the Medieval Warm Period seems not to have been global but was restricted in location such as to parts of Europe. Analyses indicate that global average temperature at the peak of that warm period in Europe was not as warm as we have observed recently.
Claim: Carbon dioxide emissions from fossil fuel burning are very small compared with those from natural ecosystems, oceans and volcanos.
It is a major and long-recognised mistake to assert that the approximately 120 billion tonnes carbon per year (emitted as CO2 from biological respiration on land, including about 60 billion tonnes carbon per year from microbial and animal respiration) swamps the 7 billion tonnes carbon per year released to atmosphere from fossil fuel burning. It is a mistake because the emission from respiration has been occurring for millions of years, balanced by uptake via plant photosynthesis. It is the plant organic matter produced by photosynthesis that is respired back to CO2 by the plants and by organisms that feed on live plants and dead plant matter during the process of decomposition. That is why in the centuries before fossil fuel burning started in earnest, atmospheric CO2 concentration was rather stable – annual uptake of CO2 by photosynthesis was balanced automatically by annual CO2 emission by respiration of its organic products. Nearly all C that is fixed by photosynthesis is eventually respired back to CO2 – most of it within the year. A minute fraction of each year’s C turnover in that way does not respire quickly, accumulating instead in soil organic matter, sediments, forest regrowth and peat. This can cause small imbalances for periods of time during which the land biosphere can be a net source or a net sink. During the last few decades the land has been a net annual sink of approximately 1 to 2 billion tonnes carbon per year, despite the tropical deforestation that is occurring. An important area of current research is to assess how long that net sink might carry on for.
As is the case for the land, the oceans too have a two-way CO2 exchange. About 90 billion tonnes carbon per year are released as CO2 from the oceans as part of a natural process of ocean circulation and heating in certain regions. This out-gassing is closely matched by CO2 uptake of similar magnitude in other parts of the oceans. As on land, small mismatches between the oceanic release and uptake can lead to periods during which the oceans are a net source or a net sink. Over recent decades the oceans have been a net sink of about 2 billion tonnes carbon per year. Again it is an area of current research to deduce when that might switch to a source, possibly as a result of ocean warming and of ocean acidification caused by the increasing load of dissolved CO2.
The assertion in the program that volcanic emissions of CO2 are large relative to man-made sources is entirely false. The emission of CO2 from volcanos, earthquakes and fumaroles, and from other leaks of subsurface CO2 reservoirs, has long been known to total no more than 0.1 billion tonnes carbon per year globally, which is a tiny fraction of the 7 billion tonnes carbon per year released now from fossil fuel burning.
Satellite and radiosonde balloon data do not show the warming in the mid-troposphere that is recorded at ground level, while greenhouse theory says they should see warming amplified with altitude in the troposphere, the lowest level of Earth’s atmosphere.
This conflict of theory and apparent observation has been a source of raging scientific debate and analysis over the last decade. It was resolved in 2005. Technical measurement problems including those concerned with the conversion of the raw satellite and radiosonde data to temperature changes through time have been identified and corrected and there is no longer a significant conflict. In fact, the warming of the mid-troposphere does track that measured at ground level, and is also quite close to that predicted by the models based on greenhouse-theory. There may still be a small shortfall of measured warming in the mid-troposphere compared with the expectation from some models, but it is not thought to be a serious discrepancy.
Claim: Global average temperatures declined during the post-war period when rapid industrialization was occurring and, consequentially, CO2 concentration was rising more quickly than earlier. Therefore the CO2 increase does not cause warming.
The graphic used in the original program to depict the global average atmospheric temperature record of the last century does not reflect the widely accepted record from thermometers used by climate scientists world-wide. It accentuates the warming between 1910 and 1940, the cooling between 1940 and about 1970, and it does not include the most recent data. The existence of the post-war cooling period does not prove that increased carbon dioxide concentration does not lead to atmospheric warming. Atmospheric CO2 concentration is known to be one of several ‘forcing’ factors that can cause annual average temperatures to vary with time, and now dominates other factors. Earlier, CO2 was not the dominant source of temperature change from decade to decade. From 1940 to the mid-1970s human emission of industrial air pollution aerosols (filth) into the atmosphere during the post-war economic boom appears to have had a cooling effect that exceeded the small warming effect of the increased atmospheric CO2 at the time. After the clean-air movement reduced air pollution in the industrialised nations, the continued build up of atmospheric CO2 concentration became the dominant temperature-forcing agent. These changes have been successfully modelled by the global climate models leading to the conclusion that it is the now high CO2 concentration that is the cause of the rapid warming of the last couple of decades despite some offset recently by air pollution from the ‘Asian brown cloud’. Comparison of the infrared radiation loss from Earth between 1970 and 1997 gave direct observational proof that ‘greenhouse forcing’ had occurred.
Claim: The record of global temperature and atmospheric CO2 concentration obtained from ice-cores shows that atmospheric CO2 concentration increases about 800 years after global average temperature has increased as a result of other causes. Therefore atmospheric CO2 increase is a result, not a cause, of warming.
It is true that there has been a lag during deglaciations reported from analyses of the Antarctic ice-core record covering glacial-interglacial periods of the ice-age era. The length of that lag is still in doubt. Such a lag is not surprising, as CO2 is not considered to be a trigger of the transition out of the glacial periods of the Pleistocene: it is thought of as an amplifier. Any inference, purportedly derived from the ice-core data, that increased atmospheric CO2 does not produce atmospheric warming, is incorrect. Extra CO2 in the atmosphere causes warming of the atmosphere and positive feedbacks such as de-gassing of ocean water with warming, peat oxidation, and perhaps release of methane from peat deposits, can gradually cause build up of greenhouse gases in the atmosphere, which amplify the warming. This observed and natural delayed CO2 release is a reason for considerable concern with respect to future global warming driven initially by human-induced CO2 releases. It represents a potential delayed-action instability in the Earth’s climate system that it would be imprudent for man to unleash on future generations.
Claim: Atmospheric temperature variation over recent centuries is mainly an expression of variability in solar activity affecting cloud formation via cosmic ray load on the atmosphere.
This is a variant of an age-old hypothesis which has been exhaustively discussed over many decades. The cosmic ray link was an exciting hypothesis that has been examined closely and found wanting as an explanation of the observed post-war warming. Although small variations in solar intensity received on Earth caused by variations in the rotation and orbit of the Earth around the sun have been found to be the cause of ice-age development and retreat, the large climate change deriving from small solar changes is attributable to the gradual development of amplifying positive feedbacks involving, among other things, greenhouse gases mentioned above – but those responses take many millenia to exert influence. Over the last few decades, observed solar variations have been far too small to account for the observed warming in that period, while the increased concentrations of greenhouse gases can account for the observed increase, when the contrary effect of atmospheric aerosols is also factored in. The period of warming from about 1910 to 1940 is a response primarily to a volcanically quiet period, that led to reduced sulphate aerosol emissions from volcanic activity compared with previously and subsequently, reinforced somewhat by a small increase in atmospheric CO2 concentration during that period. Any contribution of solar intensity variation is still controversial as a potential third contributor to that period of warming. For variation in solar output to influence climate within years, there would have to be some unknown powerful amplifying mechanism. Much scientific discussion has, to date, failed to identify such a mechanism. The search will continue.
Dr Roger Gifford
On behalf of the Academy’s National Committee for Earth System Science
Guide to facts and fictions about climate change (The Royal Society, UK)
Swindled! (Real Climate, USA)
More information about climate change from the Academy is available.
The great global warming swindle: a critique. Bulletin of the Australian Meteorological and Oceanographic Society, volume 20.