Hypothesis 1: Human influence on climate variability and change is of minimal importance, and natural causes dominate climate variations and changes on all time scales. In coming decades, the human influence will continue to be minimal.Roger Pielke snr invited feedback on these hypotheses following criticism of them at Real Climate: What do Climate Scientists Think? (See Comments 36, 43, 49)
Hypothesis 2a: Although the natural causes of climate variations and changes are undoubtedly important, the human influences are significant and involve a diverse range of first order climate forcings, including, but not limited to, the human input of carbon dioxide (CO2). Most, if not all, of these human influences on regional and global climate will continue to be of concern during the coming decades.
Hypothesis 2b: Although the natural causes of climate variations and changes are undoubtedly important, the human influences are significant and are dominated by the emissions into the atmosphere of greenhouse gases, the most important of which is CO2. The adverse impact of these gases on regional and global climate constitutes the primary climate issue for the coming decades.
- Invitation On Assessing Three Climate Hypotheses
Pielke snr has now published the feedback he has received about the different hypotheses: Feedback On My Invitation On The Three Hypotheses Regarding Climate Forcings
I did post comments (and received responses) to John Cook’s blog: A Scientific Guide to the 'Skeptics Handbook' , which does seem to make an honest attempt to evaluate evidence about climate change, about Pielke snrs invitation to improve his hypotheses.
32. billkerr at 11:11 AM on 2 July, 2010.
hi John,
Have you considered the choice b/w Pielke snrs invitation and hypotheses 2a and 2b? (Invitation On Assessing Three Climate Hypotheses) You seem to support 2b judging by your handbook's CO2 emphasis but 2a may be a better fit for the evidence
Hypothesis 2a: Although the natural causes of climate variations and changes are undoubtedly important, the human influences are significant and involve a diverse range of first order climate forcings, including, but not limited to, the human input of carbon dioxide (CO2). Most, if not all, of these human influences on regional and global climate will continue to be of concern during the coming decades.
Hypothesis 2b: Although the natural causes of climate variations and changes are undoubtedly important, the human influences are significant and are dominated by the emissions into the atmosphere of greenhouse gases, the most important of which is CO2. The adverse impact of these gases on regional and global climate constitutes the primary climate issue for the coming decades.
Response: I hadn't seen Pielke's hypotheses. It seems to me 2a and 2b aren't mutually exclusive - any climate scientist would agree that CO2 is not the only driver of climate and that we need to take into account all forcings. The reason for the emphasis on CO2 is because it is the most dominant and fastest rising forcing. The emphasis on CO2 in the Scientific Guide is also necessary as the 'Skeptics Handbook' fails to recognise the many lines of evidence that more CO2 forces up temperature - this is a somewhat more extreme stance than the more nuanced views of Roger Pielke Snr.
50. billkerr at 10:03 AM on 3 July, 2010
#32 and #33
John,
When you say "The reason for the emphasis on CO2 is because it is the most dominant and fastest rising forcing" you are supporting Pielke snrs hypothesis 2b and rejecting 2a. They are mutually exclusive by my reading.
Doug and John,
The Real Climate discussion that Doug links to predates Pielke snrs invitation for people to improve the wording of the hypotheses if they feel the wording is inadequate, as claimed by Eric in the Real Climate discussion. This Pielke snr post, which also predates the invitation, condenses the different viewpoints
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