While Prof. David Karoly’s guest post at RealClimate is admirably nuanced, he has graciously left some low-hanging fruit to take the stick to. He states:
1. Increases of mean temperature and mean maximum temperature in Australia have been attributed to anthropogenic climate change, as reported in the IPCC Fourth Assessment.
In a comment at ClimateAudit, Ian Castles remarked on a a similar temperature phenomenon attributed to David Karoly, but mysteriously dissapearing from the AR4:
As long ago as 1996 Professor David Karoly (subsequently a lead author of the TAR and AR4) included “reduction in the diurnal temperature range” (DTR) among the pieces of evidence that had led the IPCC to reach the conclusion that “the balance of evidence suggests a human influence on climate” (“Detecting a Human Influence on Climate” in Australian National Academies? Forum conference “Australians and Our Changing Climate: Past Experience and Future Destiny”, 25 November 1996, Summary of Proceedings, p. 39).
Now that it is recognized that the DTR did not change between 1979 and 2004, these confident assessments can no longer be sustained: there is no reference to the phenomenon in Table SPM-2 (p. in the SPM of the AR4. If models show a faster increase in nighttime temperatures in the last decades of the twentieth century, as stated in Chapter 8, the authors? confidence in the models should have been weakened (whereas the main theme of the Chapter is that confidence in the models has increased since the TAR).
While anybody can be wrong, or change their minds, it is interesting to see how inconvenient mistakes are swept under the rug.
2. While south-east Australia is expected to have reduced rainfall and more droughts due to anthropogenic climate change,
3. In addition, reduced rainfall and low relative humidity are expected in
southern Australia due to anthropogenic climate change.
In what was an otherwise immaculately referenced article, this assertion was strangely not referenced. It makes the dubious claim that due to a globally widespread phenomenon, a tiny localized area is expected (by whom?) to have lower rainfall. I wonder where it came from?
4. it is clear that climate change is increasing the likelihood of environmental conditions associated with extreme fire danger
Global warming is largely equivalent to the poleward movement of climate zones, and consequently vegetation types adapted to those zones. To anticipate the future fire danger in Victoria, one has only to look at the fire danger to the immediate north. I don’t know Victoria, but I bet the vegetation types to the north have a lower fire risk than the montane forests of Gippsland. At equilibrium the vegetation types will adjust and fire risk will reduce to those typical of a warmer, dryer climate composed of lower, more open forest. Temporary disequilibrium in the form of tall closed forests in a warm dry climate is probably the greatest contributor to high fire risk. Over time, as equilibrium reestablishes, the risk will return to normal.