April 10, 2023

The Great Channel 4 SwindleThe Great Channel 4 Swindle

Robin Hogan

Thanks to: Jonathan Gregory, Giles Harrison and Peter Stott

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April 10, 2023Overview

• The following claims were made in “The Great Global Warming Swindle” produced by Martin Durkin:

• “Concentrations of CO2 are too small to be important”

• “CO2 doesn’t match 20th century temperature record”

• “It can all be explained by sunspots”• “The troposphere isn’t warming”

• “Volcanoes emit far more CO2 than humans”

April 10, 2023“Concs of CO2 (~300ppmv) are

too small”

• But the “per-molecule” absorption cross-section of CO2 is hugely greater than N2 and O2 in the infrared

Carbon dioxide absorption in the middle of the infrared spectrum

…a daft comment anyway: 300 ppmv of HCN is lethal, so why shouldn’t 300 ppmv of CO2 be important?

April 10, 2023“CO2 doesn’t match

temperature”

?

April 10, 2023Whoever said only CO2

affects climate?

• Anthropogenic forcings• Carbon dioxide and other gases• Tropospheric aerosol emissions• Land use changes

• Natural forcings with an established mechanism• Stratospheric aerosol (volcanoes)• Solar irradiance changes• Changes to Earth’s orbit (Milankovic cycles) (~20 kyr)• Solar cycle effect on ozone via UV modulation (11 yr)

• Possible natural forcings lacking an established mechanism• Cosmic ray effects on clouds (11 or 22 yr?)• Solar system and galactic spiral arms (~0.5 Gyr)

• And natural variability!

April 10, 2023

April 10, 2023

April 10, 2023

Official NASA data have an earlier upturn

?

? ?

April 10, 2023From The Independent

• Source of Channel 4 temperature plot• 1998 article in “Medical Sentinel” by known climate

sceptics• From NASA but “Northern hemisphere land” (<1/3 of

globe)• Ended in the early-1980s so underplayed recent warming• Martin Durkin admitted that his graphics team changed

the scale so that it extended to 2000!• Durkin quotes on the matter

• “there was fluff there”• “the original Nasa data was very wiggly-lined and we

wanted the simplest line we could find”

April 10, 2023

• Shape of temperature rise can be calculated by considering natural and anthropogenic forcings

• “Post-war economic boom” led to aerosol emissions, initially offsetting the CO2 forcing

Pinatubo 1991El Chichon1982

Agung1963

April 10, 2023More recently: IPCC 2007

                                                                                         

                   

Solar irradiance + volcanoes

Carbon dioxide + aerosols

All

April 10, 2023“It can all be explained by solar-cycle

length”

April 10, 2023Friis-Christensen & Lassen

(1991)

Smoothed solar-cycle

length

Un-smoothed points (end of time series as of 1991)

Corrected by Damon and Laut (2004)

When the new data became available: Lassen and Friis-Christensen 2000

April 10, 2023

• Solar cycle length clearly cannot explain the last 50 years of warming

• But discredited data still used in C4 programme!

• Note that we can predict temperature change due to CO2, but cosmic ray link is currently just a correlation: mechanism is uncertain

Damon and Laut (2004)

Upturn previously used to explain recent

warming now looks like a blip!

April 10, 2023Longer periods…

? • Problems with fitting:• Maunder minimum

“filled in” with perfectly correlated data

• Two temperature series were “spliced together” at 1870, but lowering the second by 0.1 degrees!

• The result looks less convincing when these effects are corrected

April 10, 2023But lots of temperatures to

chose from!

• Key point: no change in solar activity has been observed that could explain the warming in the last few decades

• Note that changes to the solar irradiance are important at certain times (e.g. beginning of 20th century), but these are correlated to sunspot number so we must be very careful in attribution of correlations of temperature with solar activity

April 10, 2023“Troposphere should

warm faster than surface”

• This is consistent with recent analysis of satellite Microwave Sounding Unit (MSU)

Christy and Spencer (2003) analysis indicated troposphere warming slower than surfaceMears and Wentz corrected for diurnal drift of satellite: there is now consistency with theory

April 10, 2023IPCC verdict

• IPCC 2007:• “New analyses of balloon-borne and satellite

measurements of lower- and mid-tropospheric temperature show warming rates that are similar to those of the surface temperature record and are consistent within their respective uncertainties, largely reconciling a discrepancy noted in the TAR*.”

*TAR = Third Assessment Report, IPCC 2001

April 10, 2023“Volcanoes emit more CO2

than humans”

• Steady outgassing: up to 0.2 GtC/yr (Morner and Etiope 2002), but IPCC 2001 has < 0.1 (cf. anthropogenic: 6 GtC/yr)

• How much is emitted in a volcanic eruption?

                                                                                                     

     

Pinatubo 1991

El Chichon 1982

Agung 1963

…and Mauna Loa is itself a volcano!

April 10, 2023

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Useful links

• RealClimatehttp://www.realclimate.org/index.php/archives/2007/03/swindled/

• John Houghton’s sitehttp://www.jri.org.uk

• The Independenthttp://news.independent.co.uk/environment/climate_change/

article2355956.ece• Point-by-point rebuttal

http://portal.campaigncc.org/node/1843• The graphs from the programme

http://portal.campaigncc.org/node/1838