The debate is the degree to which anthropogenic forces stack up against natural forces. That debate is far from settled. The significant slowdown over the last 18 years in global average temperature increases, despite over one-fifth of all human CO2 ever emitted going into the atmosphere, is fostering increasing doubt on the General Circulation Models (GCMs) used to underpin the IPCC conclusions.
This was noted in the final draft of the most recent Assessment Report (AR5) Summary for Policy Makers (SPM) of the IPCC: “Models do not generally reproduce the observed reduction in surface warming trend over the last 10-15 years.” Unfortunately, when government representatives (vs. the scientists) released the final SPM, this language was removed. And Mr. Peterman wonders about Mr. Pandelidis’ skepticism?
Mr. Peterman goes on about the hypothesis of climate change (I would suggest the evidence is too weak to term it a theory) and Arrhenius. While the basic physics of the greenhouse effect are well understood, the modeled effect on the climate requires the introduction of feedback loops and amplification, notably water vapor. Some of these feedbacks are poorly understood. Consider the language by Working Group 1 of AR5: ”The assessed literature suggests that the range of climate sensitivities and transient responses covered by CMIP3/5 cannot be narrowed significantly by constraining the models with observations of the mean climate and variability, consistent with the difficulty of constraining the cloud feedbacks from observations. ”
Translation: despite significant expenditure of resources, we cannot further narrow climate sensitivities (that is, the change in temperature in response to various forcing factors) and still don’t understand clouds. In fact, scientists are unsure on whether the feedback from clouds is positive or negative.
The climate models are increasingly diverging from the observed temperature record; they fail the engineering test of usability through a lack of validation and verification. From an engineering perspective, models behaving this way would be in the dustbin. Instead, we have zealots that want to reshape the regulatory state and energy economy on the basis of such shabby models. Unbelievable.