Presentation on theme: "24 April 2014 The Great Channel 4 Swindle Robin Hogan Thanks to: Jonathan Gregory, Giles Harrison and Peter Stott Return."— Presentation transcript:
24 April 2014 The Great Channel 4 Swindle Robin Hogan Thanks to: Jonathan Gregory, Giles Harrison and Peter Stott Return
24 April 2014 Overview The following claims were made in The Great Global Warming Swindle produced by Martin Durkin: Concentrations of CO 2 are too small to be important CO 2 doesnt match 20th century temperature record It can all be explained by sunspots The troposphere isnt warming Volcanoes emit far more CO 2 than humans
24 April 2014 Concs of CO 2 (~300ppmv) are too small But the per-molecule absorption cross-section of CO 2 is hugely greater than N 2 and O 2 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 shouldnt 300 ppmv of CO 2 be important?
24 April 2014 CO 2 doesnt match temperature ?
24 April 2014 Whoever said only CO 2 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 Earths 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!
24 April 2014
Official NASA data have an earlier upturn ? ??
24 April 2014 From 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
24 April 2014
Shape of temperature rise can be calculated by considering natural and anthropogenic forcings Post-war economic boom led to aerosol emissions, initially offsetting the CO 2 forcing Pinatubo 1991 El Chichon 1982 Agung 1963
24 April 2014 More recently: IPCC 2007 Solar irradiance + volcanoes Carbon dioxide + aerosols All
24 April 2014 It can all be explained by solar-cycle length
24 April 2014 Friis-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
24 April 2014 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 CO 2, 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!
24 April 2014 Longer 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
24 April 2014 But 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
24 April 2014 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 surface Mears and Wentz corrected for diurnal drift of satellite: there is now consistency with theory
24 April 2014 IPCC 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
24 April 2014 Volcanoes emit more CO 2 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!
24 April 2014 Return Useful links RealClimate John Houghtons site The Independent Point-by-point rebuttal The graphs from the programme