Roy Spencer, a climate scientist who is skeptical of mainstream theories regarding man-made global warming, demands to see even ”one peer-reviewed paper that has ruled out natural, internal climate cycles as the cause of most of the recent warming in the thermometer record.”
THIS RESPONSE to Spencer’s challenge makes a good case.
This challenge is problematic for a few reasons. Firstly, the fact that research has not ruled out a hypothesis does not mean the hypothesis necessarily has any validity. For example, there have been no peer-reviewed papers ruling out leprehchauns as the cause of most of the recent global warming, either. But perhaps more importantly, our understanding that humans are causing global warming is not based on just one scientific study, but rather a very wide range of scientific evidence.
For example, scientists have measured the amount of heat being re-directed back towards the Earth’s surface due to the increased greenhouse effect. Quantifying the amount of global warming that this will cause simply involves multiplying the increased downward energy by the climate sensitivity. As the name suggests, climate sensitivity is a measure of how sensitive the climate is to this build-up in heat – how much the planet will warm in response to an increase in the amount of greenhouse gases in the atmosphere.
Therefore, in order to argue that humans are not the driving force behind the current global warming, skeptics like Spencer…require that the climate sensitivity to increasing greenhouse gases is low. The problem with this position is that there are many lines of evidence that the planet will warm between 2 and 4.5 degrees Celsius (°C) if the amount of carbon dioxide (CO2) in the atmosphere doubles.