Leading climate change researchers have launched a scathing attack on a speech delivered this week by Cardinal George Pell, describing it as “dreadful”, “utter rubbish” and “flawed”.

The Archbishop of Sydney Cardinal Pell, Australia’s most senior Catholic, is a long-time denier of the risks posed by human-caused climate change.

But he has taken his climate confusion right to the heart of England’s Catholic church, with a speech (you can read the whole thing here) delivered at Westminster’s Cathedral Hall.

During the speech, Pell claimed that global warming has “stopped”, that CO2 was “not a pollutant, but part of the stuff of life” and that if carbon dioxide in the atmosphere was doubled, then “plants would love it”.

The speech was given at the invitation of the Global Warming Policy Foundation — a think-tank founded in November 2009 by former UK chancellor Lord Nigel Lawson. An edited version of the speech was reproduced in The Australian yesterday.

Crikey asked several climate change researchers, including senior figures at the Bureau of Meteorology, CSIRO and leading research groups, to review the statements in Pell’s speech.

Professor Chris Turney, ARC Laureate Fellow in Climate Change at the University of New South Wales, told Crikey: “It’s all dreadful stuff, cherry picking statements to suit a belief which just doesn’t stack up against the weight of scientific evidence.”

In one section of the speech, Pell cites several climate change sceptics as proof that the Inter-governmental Panel on Climate Change, which provides guidance on the science to the UN, was “essentially reliant on computer modelling and lack empirical support”.

But Dr Karl Braganza, Manager of Climate Monitoring at the Bureau of Meteorology, said: “The notion that climate science lacks empirical evidence is specious. There is lots of observational evidence for the greenhouse effect, and the enhanced greenhouse effect.

“More generally, the idea that climate models are somehow outside the realms of normal science is flawed.  Complex system modeling using extremely well established physics and chemistry is the basis of modern day science. We use technology on a daily basis that is the result of insights from such modelling.”

Professor Steven Sherwood, of the UNSW Climate Change Research Centre, also said the claim the IPCC lacked empirical support was “false”.

He added: “IPCC estimates of past and future global warming are based mainly on analyses of past climate variations published in the peer-reviewed literature.  Computer models are used mainly to test that we understand what the past data are telling, us, and to predict regional details of future climates.”

Dr James Risbey, a senior climatologist at CSIRO Marine and Atmospheric Research, said: “Pell’s point that the IPCC’s conclusions are essentially dependent on the models is wrong.  Most of what is known about climate change and summarized in the IPCC is grounded on solid radiative physics and thermodynamic principles, and is well verified in the observational and paleoclimate record.”

Citing University of Adelaide geologist and mining company director Professor Ian Plimer, Pell said in the speech major volcanic eruptions were not being considered by climate models.

But Mike Sandiford, professor of geology at the University of Melbourne, said: “Pell refers to geologist Ian Plimer’s estimate of volcanic contributions to CO2 emissions, but volcanologists have demonstrated that Plimer’s estimate of volcanogenic CO2 emissions is too high by a factor of about 100. Plimer is just plain wrong on the volcanogenic CO2 emissions, and should be ignored.”

Professor Andy Pitman, director of the ARC Centre of Excellence for Climate System Science at the University of News South Wales, described the speech as “a combination of irrelevant statements with statements that are utter rubbish”.

At one point, Pell claims that “since 2001 carbon dioxide has increased by five per cent, but the atmosphere has failed to warm”.

Professor Pitman said: “This is a red-herring. CO2 acts on long time scales and there is literature — peer reviewed literature — that explains this in terms of masking of the warming by aerosols and La Nina.”

On a claim that the world had “cooled slightly” since 1998, Pitman added: “Whether it did or did not warm in a 10-year period is utterly irrelevant to global warming which is a multi-decadal phenomenon described by climatological timescales. Pell has presumably been told this but his statements continue to confuse climate CHANGE with climate VARIABILITY.”

Professor Roger Jones, of Victoria University, was a lead IPCC author for a 2007 report on “New Methods and Characterisations of the Future.”

Jones reviewed a section of the speech where Pell said climate change variants including “water vapour multipliers, sunspot activities and cloud formation, as well as deforestation, soil carbon and aerosols” were not well understood, as were “asteroid and comet impacts, and variations in cosmic rays.”

Jones said: “It’s hard to tell whether this is Gish’s Gallop, Pell’s Polka or Plimer’s Passe Doble. It’s a variant of yeti spotting when you’re completely lost and trying to convince your followers you know what you’re doing.”

He said water vapours were part of climate models, but there was still uncertainty about their distribution in atmosphere.

Jones added: “Clouds are pretty well agreed to be a positive feedback — this is not accepted by the denial industry. The background incidence of asteroids and comets is somewhat infrequent and a red herring. The other stuff is just not evident in past climates. The orbital characteristics are known but not big drivers on current timescales.”

As well as being at odds with the scientific evidence, Pell’s statement is also at odds with the Pontifical Academy of Sciences, which in April said: “We call on all people and nations to recognise the serious and potentially irreversible impacts of global warming caused by the anthropogenic emissions of greenhouse gases and other pollutants, and by changes in forests, wetlands, grasslands, and other land uses.”

Professor Turney added: “The simple fact is greenhouse gases keep the planet warm. Indeed, if they were to disappear from the atmosphere overnight, the temperature would plummet from a balmy average of around 14C to some -21C.

“If we flood the atmosphere with carbon, putting more greenhouse gases into the air, you would therefore expect the planet to warm further.

“As the famous quote goes, ‘Every scientific truth goes through three states: first, people say it conflicts with the Bible; next, they say it has been discovered before; lastly they say they always believed it.’ Looks like some are still in the first state.”