Response to Vahrenholt and Luning

Also published at My view on climate change.

In their reply to our criticisms, Prof Fritz Vahrenholt and Dr Sebastian Lüning exhibit a misunderstanding of various key aspects of climate science. Their claim, that mainstream science is radically wrong, is unfounded and not backed up by sufficiently strong evidence. In our response, also published at EER, we only focused on a few selected issues of contention. Here we reply to all of Vahrenholt’s and Lüning’s arguments and allegations.

However, the observations show that both surface temperatures as well as ocean heat content started to increase (during the 1970s and 80s) long after solar activity had reached its plateau (during the 1950s). This is inconsistent with a lagged response to the sun, as suggested by Vahrenholt and Lüning. The relatively steady rate of warming of both ocean and atmosphere over the past four decades indicates that this must be caused by another process. The sun cannot be responsible for the warming of the past four decades, irrespective of how strongly one wishes to amplify its effect.

Updated graphic of total heat content from Church et al 2011

Vahrenholt and Lüning cite the work of Solanki and co-authors in support of their claim. However, Solanki et al made the same point as we do: "This comparison shows without requiring any recourse to modeling that since roughly 1970 the solar influence on climate (through the channels considered here) cannot have been dominant" (Solanki et al., 2003), and: "Although the rarity of the current episode of high average sunspot numbers may indicate that the Sun has contributed to the unusual climate change during the twentieth century, we point out that solar variability is unlikely to have been the dominant cause of the strong warming during the past three decades." (Solanki et al., 2004, referring to their 2003 paper). This is just one of many examples where Vahrenholt and Lüning misinterpret what is written in the literature in order to bolster their point of view.

In short, Vahrenholt’s and Lüning’s reply does not change our conclusion: Their claim that “the contribution of CO2 to global warming is being exaggerated” does not stand up to scientific scrutiny. The sun is not responsible for the warming seen during the past 4 decades. Greenhouse gases in all likelihood are.

Climate changes in the deep past (going back hundreds of thousands or even millions of years) can not be explained, let alone quantitatively modeled, without a substantial warming effect from CO2. We invite readers to view this excellent talk by the American geologist Richard Alley. It's telling that no physics-based climate model has been developed that can simulate past and recent climate changes without a substantial warming effect from an increase in greenhouse gas concentrations. Wishing away the effects of CO2 is not enough in science; it needs to be quantitatively demonstrated.

Posted by Bart Verheggen on Tuesday, 26 June, 2012

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