Controversies in Science/Are humans causing global warming/A critique of Is Global Warming Mainly Due to Anthropogenic Greenhouse Gas Emissions?

(Review Paper) Cited in

Points Made
Scientist Richard Lindzen argues that global warming is not primarily anthropogenic, and that greenhouse gas is not as detrimental to the Earth’s cooling as previously believed.

Methods
Lindzen does not believe that global warming is human caused, that the IPCC’s models and assessments are too simplified, or alternatively giving too much significance to greenhouse gases. Lindzen believes that greenhouse gas is more likely contributing to global warming approximately 30%, therefore not the main contributor to global warming. Lindzen believes that the IPCC is not considering data from other climatological events such as El Nino or the Little Ice Age, for example, which could be significantly affecting our current climate change.

The IPCC’s main support for anthropogenic climate change stems from the theory that thermal radiation is causing cooling on Earth’s surface and greenhouse gases are destructive to this cooling system, resulting in warmer temperatures. Lindzen, however, does not believe that thermal radiation is the only source of cooling. The IPCC believes that climate change is primarily anthropogenic because greenhouse gas has increased steadily in the past century. Lindzen argues that thermal radiation is not solely responsible for cooling Earth's temperature, and that heat travels away from Earth’s surface in an upward motion until the thermal radiation can escape into space, which Lindzen calls the “Characteristic Emission Level”. Warming at this level would be warmer than at Earth’s surface, approximately twice to three times as much. Statistics show that the warming trend in the Characteristic Emission Level in the troposphere is only at 0.1 degrees Celsius, so that would put the warming trend on the surface at approximately 0.033 degrees Celsius.

Results
Because the estimated warming trend is 0.033, this is much lower than the IPCC's estimated warming trends of 1.8 - 4.0 degrees celsius on Earth's surface, which suggests that global warming is not primarily caused by greenhouse gas emissions, and therefore not caused by humans.