He says "Whatever may come of all this scientific enquiry, as readers can see, the higher temperatures forecast by the IPCC, if and when they ever occur, may not result in lower rainfall."

Has anyone ever suggested higher temperatures would result in lower rainfall?? Is the author setting up a false straw man to shoot down? Or doesn't he understand what he reads about climate change?

It's absolutely elementary that warmer air can hold more water, and so higher temperatures should mean more rainfall (averaged worldwide).

It is widely reported that global warming is likely to lead to different weather _patterns_ (eg, zones of high or low rainfall would move to different places on the earth's surface), but the specifics of this are much harder to predict. Thus the lower rainfall around Perth corresponds to climatic zones moving southwards. But this doesn't mean lower rainfall worldwide.

Thus worse floods (due to (1) higher rainfall generally, and (2) high rainfall falling in different places, where the river systems haven't developed to handle it), and worse droughts (ie, (1) the effect is worse due to higher temperatures, and (2) worse in their effects because they occur in different places) are both to be expected as a result of global warming.

This is a very interesting article that is worthy of considerable thought.

Jeremy, it is probably reasonable to assume that Mark is writing about Oz. After all it is in Oz that our governments paper cutout scientists have been predicting eternal drought due to AGW, in an attempt to help Julia get her cap & trade [tax] up & running. This combines well with their desire to keep the gravy train on the rails.

Now of course, after a flood or 2, & a couple of cyclones those same paper cutouts have flipped, just like the PDO. Now we are all going to drown, not burn.

Perhaps if some of these people did some science, rather than look for an excuse to introduce a new tax, we would know a bit more about the POD, what it does, & why.

With your hotter atmosphere example, which side are you on, you do sound to be on the fence. Half the AGW warming crowd tell us the hotter atmosphere will hold, not drop more water, hence drought. The other half claim it will drop it all, & flood. I guess for them, & you, it depends what the newspaper headline said yesterday, as to what can be made most scary, Oh, & Julia's last press conference.

Mark Lawson here

Jeremy - I see you do realise that higher temperatures may have quite different effects on rainfall, but as Hasbeen correctly points out CSIRO and others have repeatedly warned us that higher temperatures mean more droughts. The droughts in the Murray-Darling basin were supposedly due to global warming and so on, and on. The Garnaut report (which used the CSIRO projections) said similar stuff.

Admittedly scientists never tried to sell that message in Europe, now that I think about it, as they knew they'd never get away with it. But in dryer Australia these warnings were constant. We are all going to starve to death because crops would wither in the heat etc, etc. Just why quite experienced scientists persist in projections based on very limited information while ignoring known climate cycles is an interesting question for another time.

Hasbeen and Mark Lawson
Jeremy is correct. A warmer atmosphere does hold more water. It has to fall out somewhere as rain or snow. Simple thermodynamics explains this very well, but most people don't understand this. We can expect regional hot, dry and and wet spots.

Hasbeen
A country's policy (where the ideological arguments are taking place) on adaptation and mitigation has nothing to do with the science.

Mark
No scientist, scientific academy or organisation has said droughts in the Murray-Darling basin were entirely due to global warming. If anything, they say there is an anthropogenic component to the warming.

It is hard enough to convey the science without journalists distorting what the IPCC, CSIRO, BOM and others have actually been saying. Whether you do this intentionally or not has the same effect - it creates doubt in the mind of your readers.

"We are all going to starve to death because crops would wither in the heat etc, etc."

One has to question your motives when you deliberately take things out of context and perpetuate the myth.

To be sure, the aftermath of this latest ENSO will result in a cooling. Nevertheless, the upward trend will prevail.

Bonmot said

"Jeremy is correct. A warmer atmosphere does hold more water. It has to fall out somewhere as rain or snow."

It seems that pro warmers have forgotten, rather conveniently, that prior to the big wet we are currently experiencing, AGW activists claimed that Global Warming would bring about an endless drought in Australia. The snowfields would, according to them, be seriously affected, and in the UK, the winters were supposed to be very mild from now on. All of this was proven to be completely wrong. The consequence of this was politicians built desalination plants and not dams.

Ian Plimer pointed out correctly at the time, that a warmer climate did indeed hold more water and was likely to result in greater not lesser rainfall. He was roundly criticised by AGW activists for that view.

If AGW proponents could make reliable predictions then maybe their support base would increase and not decrease as it is now.