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The Drought is natural climate variability?


I wonder how he validated his model that he ran backwards for 10 000 years, since it needed things like air pressure.


Dec. 28th, 2006 04:21 am (UTC)
There are ways to do it...just been too long since I've had much to do with climate models to think of how. Of course it's not going to be totally accurate, it's a model.

And I agree that the drought is most likely natural climate variability. There have been worse droughts since white settlement. We tend to go through cycles. What he says here is right:

Mr Hunt said climate change due to increased levels of greenhouse gases in the atmosphere built on naturally occurring patterns and would be felt in the coming years.

"At the moment I think natural variability dominates. Increasingly, over the next few decades you would expect to see the greenhouse effect start to dominate, particularly with things like temperature," he said.

We do need a few more decades data before you could start to say global warming is causing the changes. A decade or so of "changes" isn't enough.
Dec. 28th, 2006 04:24 am (UTC)
but it isn't enough to say conclusively either way and a lot of those models use huge assumptions.
Dec. 28th, 2006 04:35 am (UTC)
Yes, they do, but I think they have a fairly decent proxy record of drought, and as even records of the last 200 years have shown, the drought we're in now isn't overly unusual. Here shows some of the major droughts of the last hundred years. Another interesting article here.

And he is using words like highly likely. I'd go more with him than politicians. The 1 in a 1000 year drought statement has no merit at this stage. If the drought continues for a few more years it may need to be revisited. But at this stage it's still within the realms of natural variability.
Dec. 28th, 2006 04:39 am (UTC)
1 in 1000 statements NEVER have merit with me. You can't claim something without the data for the period. That's my only issue with the 10 000 year drought record thing. They do it in my field too all the time. It's meaningless.

The issue with drought though is ... if you look at Perth rainfall, which is a classic if you want to study variability and possible climate shifts is there is a marked step down in yearly averagerainfall in the early 1970s that separates pre 1970s data to post 1970s data. Something happened around that time and the rainfall has never recovered. It's quite fascinating.
Dec. 28th, 2006 05:10 am (UTC)
Yeah, totally meaningless, as he says in that article. Most people also don't understand what that statement means in terms of hazards. You can have two 1 in 100 year events within 20 years.

There is definitely something going on in the southwest of WA, as he mentions:

Mr Hunt said the dry sequence in the southwest was different, with a decline over 30 years, which included the odd year of above-average rainfall.

"It isn't violating what I am saying, but it is a very unusual sequence of events there," he said.

Two years ago my uni (including my honours and masters supervisors) released a study on the decrease in rainfall in that area, and their modelling suggests it may mainly be due to widespread land clearing (also here).
Dec. 28th, 2006 05:12 am (UTC)
ooh thanks for those - i'll have a look at them later! That's part of paper 2!!!!

You can have a 1 in 100 year storm two years running. But trying frigging explaining that to planners. It does my head in!!!!!
Dec. 28th, 2006 05:20 am (UTC)
Pitman, A. J., G. T. Narisma, R. A. Pielke Sr., and N. J. Holbrook, 2004: The impact of land cover change on the climate of southwest Western Australia. Journal of Geophysical Research - Atmospheres, 109, D18109, doi:10.1029/2003JD004347

There's a pdf here. Andy Pitman was my honours supervisor, Neil Holbrook my masters (and hence cohort in tropical cyclone forecasting).

People don't understand even the basics of risk. That's why they refuse to get their kids vaccinated on the minute risk of an adverse reaction, yet still strap them into the car or bathe them which have a much higher risk.
Dec. 28th, 2006 05:22 am (UTC)
I hear ya sista! Drives me nuts!!!! Chances of getting killed in a terrorist attack in London versus getting killed in a car accident and yet ppl tell me they are no longer travelling to Europe. And my sister totally picked her honeymoon location around tsunamis. *throws hands up in the air*

Thanks heaps for the pdf. I wonder if that counts as having worked on my thesis today?
Dec. 28th, 2006 04:40 am (UTC)
I guess also as you say - a drought isn't really one year with no rain. That's just a bad year. You have to have a sustained period of no rain for it to really be a drought. I guess what we don't know is what will happen on the other side and if this will end.

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