Policy Documents

Scientific Critique of IPCC’s 2013 'Summary for Policymakers'

October 16, 2013

The Summary for Policymakers released in September by the United Nations’ Intergovernmental Panel on Climate Change is filled with concessions that its past predictions were too extreme and misleading and unscientific language, according to a team of scientists from the U.S. and Australia.

The authors are part of the Nongovernmental Panel on Climate Change (NIPCC), an independent auditor of the work of the United Nations’ Intergovernmental Panel on Climate Change (IPCC). The NIPCC receives no government or corporate funding. On September 17, ten days before the IPCC released its fifth assessment report, NIPCC released Climate Change Reconsidered II: Physical Science, a 1,000-page report listing some 50 climate scientists as authors, contributors, or reviewers.

In a new and smaller report issued in mid-October, titled “Scientific Critique of the IPCC’s 2013 Summary for Policymakers,” four of the lead authors of the NIPCC report offer a withering critique of the IPCC’s latest report. Among the 11 “retreats” they identify in the IPCC’s latest report:

* Global temperatures stopped rising 15 years ago despite rising levels of carbon dioxide, the invisible gas the IPCC claims is responsible for causing global warming.

* Temperatures were warmer in many parts of the world approximately 1,000 years ago, during the so-called Mediaeval Warm Period, due entirely to natural causes.

* Antarctic sea ice extent is increasing rather than shrinking.

* Climate computer models fail to reproduce the observed reduction in surface warming trend over the last 10-15 years.

* Computer models fail to represent and quantify cloud and aerosol process.

* Solar cycles may account for the pause in global air temperature.

* “No best estimate for equilibrium climate sensitivity can now be given because of a lack of agreement on values across assessed lines of evidence and studies” (SPM-11, fn 16).”

* “Low confidence” is expressed that damaging increases will occur in either drought or tropical cyclone activity.

The NIPCC scientists also condemn “statements by the IPCC ... written in such a way that although they may be technically true, or nearly true, they are misleading of the actual state of affairs.” They fault the IPCC for claiming the warming of the late twentieth century was “unequivocal” when many temperature databases show no warming, and for saying changes since 1950 were “unprecedented” when the historical record contains many examples of changes due to natural causes that were more rapid or more extreme.

The scientists are especially critical of the IPCC’s claim that it is “95% confident” that global warming is man-made and will be harmful. “This terminology is unscientific,” they write. “It has been used improperly to create a false impression of increasing statistical certainty through the most recent IPCC assessment reports.... IPCC’s quasi-numeric confidence statements represent considered ‘expert opinion,’ reflecting a process not very different from a show of hands around a discussion table. The terminology confers an impression of scientific rectitude onto a process that is inescapably subjective and has been widely criticized as misleading.”

Regarding the IPCC’s claim that “The ocean has absorbed about 30% of the emitted anthropogenic carbon dioxide, causing ocean acidification” (SPM_7), the NIPCC authors say “This is alarmist and scientifically pernicious terminology. What is being described is actually the uncertain occurrence of a small decrease in the average alkalinity of the ocean. The IPCC assesses the likelihood of future pH change using unvalidated computer modeling that is known to be unreliable.”

Regarding the IPCC’s claim that “The total natural RF from solar irradiance changes and stratospheric volcanic aerosols made only a small contribution to the net radiative forcing throughout the last century, except for brief periods after large volcanic eruptions” (SPM_10), the NIPCC authors say the statement “is trivially true and at the same time profoundly misleading. The Sun’s effect on Earth’s climate extends far beyond simple variations in total solar insolation (TSI), and importantly includes magnetic and solar wind particle streams and their modulating effect on galactic cosmic rays. These effects are largely ignored by the IPCC.”

Read the full report here (PDF).

Read more about NIPCC here.