Straight from the horse's mouth: Hansen says global warming of late 20th century was NOT due CO2 or fossil fuel burning

In a paper published in PNAS in 2000, global warming religion high priest James Hansen argues that "rapid warming in recent decades has been driven mainly by non-CO₂ greenhouse gases... not by the products of fossil fuel burning, CO₂ and aerosols..." Furthermore, Hansen correctly points out "The growth rate of non-CO₂ greenhouse gases has declined in the past decade." The summary of the paper states, 

"Non-CO2 Greenhouse Gases: These gases are probably the main cause of observed global warming, with CH4 [methane] causing the largest net climate forcing." 

Hansen appears unaware methane represents an extremely tiny 0.0000017 mole fraction of the atmosphere and contributes almost nothing to the posited 'greenhouse' effect.


H/T to Bill Wallace of Global Hot Air for this discovery

Global warming in the twenty-first century: An alternative scenario

1. James Hansen*†, 
2. Makiko Sato*‡, 
3. Reto Ruedy*, 
4. Andrew Lacis*, and 
5. Valdar Oinas*§

1. ^*National Aeronautics and Space Administration Goddard Institute for Space Studies, ^‡Center for Climate Systems Research, Columbia University Earth Institute, and ^§Center for Environmental Prediction, Rutgers University, 2880 Broadway, New York, NY 10025

1. Contributed by James Hansen

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Abstract

A common view is that the current global warming rate will continue or accelerate. But we argue that rapid warming in recent decades has been driven mainly by non-CO₂ greenhouse gases (GHGs), such as chlorofluorocarbons, CH₄, and N₂O, not by the products of fossil fuel burning, CO₂ and aerosols, the positive and negative climate forcings of which are partially offsetting. The growth rate of non-CO₂ GHGs has declined in the past decade. If sources of CH₄ and O₃ precursors were reduced in the future, the change in climate forcing by non-CO₂ GHGs in the next 50 years could be near zero. Combined with a reduction of black carbon emissions and plausible success in slowing CO₂ emissions, this reduction of non-CO₂ GHGs could lead to a decline in the rate of global warming, reducing the danger of dramatic climate change. Such a focus on air pollution has practical benefits that unite the interests of developed and developing countries. However, assessment of ongoing and future climate change requires composition-specific long-term global monitoring of aerosol properties.