Mr. Suffron’s letter of Oct. 13 is largely based on the “Key Uncertainties” section of the AR5 Summary, without any deeper understanding or context. Box TS.1, pg. 36 of the AR5 Summary, provides important guidance on how to interpret confidence ratings in the report. “Confidence is expressed qualitatively. Quantified measures of uncertainty in a finding are expressed probabilistically and are based on a combination of statistical analyses of observations or model results, or both, and expert judgment.” In this regard, the terms “virtually certain” and “very likely” describe probabilities of 99 to 100 per cent and 90 to 100 per cent, respectively. The probability of global-scale extreme weather and climate change events are summarized in the AR5 Summary, TFE.9, Table 1, pg.110. The following events are either virtually certain or very likely to occur by the late 21st Century: warmer days and fewer cold nights, warmer and/or more frequent hot days and nights; warmer spells/heat waves; heavy precipitation events; increased incidence and/or magnitude of extreme high sea levels. Regarding his confidence concerns about the rate of tropospheric warming and decadal predictions. Firstly, AR5 recognizes that decadal tropospheric projections are in their infancy and likely to improve in the future (AR5, Chapter 11, pg. 965). Secondly, although there are uncertainties about the rate of tropospheric warming as Mr. Suffron emphasized, “…it is virtually certain that globally the troposphere has warmed…,” and there is unanimous agreement on the upward trend (Chapter 11, pg. 196). Although there are uncertainties about the rate of tropospheric temperature increase, this is not the case for the surface, “…it is certain that globally average near surface temperatures have increased since the late 19th Century…” (Chapter 2, pg. 194). Further, “…that the world has warmed since the 19th Century is unequivocal…” “Evidence for a warming world comes from multiple independent climate indicators...[and]…include changes in surface, atmospheric, and oceanic temperatures; glaciers; snow cover; sea ice; sea level and atmospheric water vapour. Scientists from all over the world have independently verified this evidence many times.” (Chapter 2, pg. 198). Regarding David Legate, Science & Education August 2013, the difference in the findings between Legate and Cook have to do entirely with how consensus is defined. “In the end, of all the abstracts that took a position on the subject, 22.97 per cent and 72.50 per cent were found to take an explicit but unquantified endorsement position or an implicit endorsement position, respectively.” (http://www.wikiwand.com/en/Surveys_of_scientists%27_views_on_climate_change#/Powell.2C_2013). Mr. Suffron has expressed displeasure with Cook 2013, and perhaps with some justification. For alternative studies with similar findings, Mr. Suffron can also refer to Benestad 2015, “Learning from mistakes in climate research,” Theoretical and Applied Climatology (http://link.springer.com/article/10.1007/s00704-015-1597-5) where again, the Introduction shows that the majority opinion is that anthropogenic climate change or global warming is a reality. Also see the above well-referenced Wikiwand link. In conclusion and with respect to Mr. Suffron’s misunderstanding, Benestad (2015) writes, “There is a lack of public awareness about the level of scientific agreement underpinning the view on anthropogenic global warming.“
Denis Stefani
