The wettest 30-year period was reconstructed in the twentieth century and the driest in the mid nineteenth century. Importantly, neither series shows a significant trend toward either wetter or drier conditions over the past 3 centuries. The wettest and driest years and 10-year periods were, however, all reconstructed during the twentieth century.

4 ten year periods and one 30 year period were significantly different (5%) to the long term mean for maximum extreme rainfall and runoff, and one ten year period and one 30 year period were statistically different for minimum extremes of each runoff and rainfall respectively.

In addition, the percentage of coefficient of variation (cv) of the reconstructed river flow series for the 3 subperiods was 50.1%, 48.1%, and 64.3%, respectively, again suggesting an increase in variability in the most recent period.

Two additional analyses were performed to test whether this suggested recent increase in river flow/rainfall variability was real and not an artifact of the varying number of coral series through time. First, a reconstruction of river flow from the 4 longest continuous coral series (Pandora 08B, Havannah O1A, Hook O1B and Humpy OlB), 1724—1983, showed the same increase in variance (though similar median flows) between 1749—1866 and 1867—1983 with the percentage cv increasing from 56.1% to 64.3%. The anomaly of percentage of years for very high and very low flow events changed from —5%, 1749—1866
to +7%, 1867—1983 (see Table 10). Second, the frequency of luminescent lines at three midshelf reefs, which only occasionally experience the largest flood events, was examined. Both these analyses support an increase in river flow/rainfall variability since the late nineteenth century.

A graph towards the end of the paper of the 21 year standard deviation of river flow shows a marked increase in the 20th century.

The wettest 30-year period was reconstructed in the twentieth century and the driest in the mid nineteenth century. Importantly, neither series shows a significant trend toward either wetter or drier conditions over the past 3 centuries. The wettest and driest years and 10-year periods were, however, all reconstructed during the twentieth century.

4 ten year periods and one 30 year period were significantly different (5%) to the long term mean for maximum extreme rainfall and runoff, and one ten year period and one 30 year period were statistically different for minimum extremes of each runoff and rainfall respectively.

In addition, the percentage of coefficient of variation (cv) of the reconstructed river flow series for the 3 subperiods was 50.1%, 48.1%, and 64.3%, respectively, again suggesting an increase in variability in the most recent period.

Two additional analyses were performed to test whether this suggested recent increase in river flow/rainfall variability was real and not an artifact of the varying number of coral series through time. First, a reconstruction of river flow from the 4 longest continuous coral series (Pandora 08B, Havannah O1A, Hook O1B and Humpy OlB), 1724—1983, showed the same increase in variance (though similar median flows) between 1749—1866 and 1867—1983 with the percentage cv increasing from 56.1% to 64.3%. The anomaly of percentage of years for very high and very low flow events changed from —5%, 1749—1866
to +7%, 1867—1983 (see Table 10). Second, the frequency of luminescent lines at three midshelf reefs, which only occasionally experience the largest flood events, was examined. Both these analyses support an increase in river flow/rainfall variability since the late nineteenth century.

A graph towards the end of the paper of the 21 year standard deviation of river flow shows a marked increase in the 20th century.

So one size doesn’t fit all. Different trends and interactions in different parts of the continent.

PALEOCEANOGRAPHY, VOL. 22, PA2218, doi:10.1029/2006PA001377, 2007

Tropical river flow and rainfall reconstructions from coral luminescence: Great Barrier Reef, Australia

Janice M. Lough, Australian Institute of Marine Science, Townsville, Queensland, Australia

Rainfall and river flow in northeast Queensland, Australia, are highly seasonal and show high interannual and decadal variability that is modulated by El Niño–Southern Oscillation (ENSO) events and the Pacific Decadal Oscillation (PDO). Reconstructions of October–September freshwater input to the Great Barrier Reef lagoon and October–September Queensland rainfall are developed from visual assessment of the occurrence and intensity of luminescent lines in massive Porites from up to 25 coral cores from 15 nearshore reefs regularly influenced by river flood plumes. Separate reconstructions are developed for four rivers (Herbert, Burdekin, Pioneer, and Fitzroy), and these are used to reconstruct total annual freshwater flow into the Great Barrier Reef (69–74% variance calibrated) and an index of Queensland rainfall (53–57% variance calibrated). The reconstructions extend back to 1631 but are most reliable from 1661 and capture significant decadal variability. The reconstructions provide insights into long-term tropical rainfall and river flow variability and the behavior of ENSO and the PDO over several centuries. Significant, though weak, relationships are found between these reconstructions and an independent reconstruction of ENSO. The reconstructions highlight that observations from the instrumental records of high interannual and decadal rainfall and river flow variability in northeast Australia also characterize the past few centuries.

Although there appears to be no overall trend toward wetter or drier conditions, the reconstructions suggest that the variability of rainfall and river flow has increased during the twentieth century with more very wet and very dry extremes than in earlier centuries, as projected for the region as a consequence of global warming.

So one size doesn’t fit all. Different trends and interactions in different parts of the continent.

PALEOCEANOGRAPHY, VOL. 22, PA2218, doi:10.1029/2006PA001377, 2007

Tropical river flow and rainfall reconstructions from coral luminescence: Great Barrier Reef, Australia

Janice M. Lough, Australian Institute of Marine Science, Townsville, Queensland, Australia

Rainfall and river flow in northeast Queensland, Australia, are highly seasonal and show high interannual and decadal variability that is modulated by El Niño–Southern Oscillation (ENSO) events and the Pacific Decadal Oscillation (PDO). Reconstructions of October–September freshwater input to the Great Barrier Reef lagoon and October–September Queensland rainfall are developed from visual assessment of the occurrence and intensity of luminescent lines in massive Porites from up to 25 coral cores from 15 nearshore reefs regularly influenced by river flood plumes. Separate reconstructions are developed for four rivers (Herbert, Burdekin, Pioneer, and Fitzroy), and these are used to reconstruct total annual freshwater flow into the Great Barrier Reef (69–74% variance calibrated) and an index of Queensland rainfall (53–57% variance calibrated). The reconstructions extend back to 1631 but are most reliable from 1661 and capture significant decadal variability. The reconstructions provide insights into long-term tropical rainfall and river flow variability and the behavior of ENSO and the PDO over several centuries. Significant, though weak, relationships are found between these reconstructions and an independent reconstruction of ENSO. The reconstructions highlight that observations from the instrumental records of high interannual and decadal rainfall and river flow variability in northeast Australia also characterize the past few centuries.

Although there appears to be no overall trend toward wetter or drier conditions, the reconstructions suggest that the variability of rainfall and river flow has increased during the twentieth century with more very wet and very dry extremes than in earlier centuries, as projected for the region as a consequence of global warming.

So rural groups are lobbying for ongoing support of assistance measures – what some might regard as agrarian socialism – capitalising gains and socialising losses ((in good seasons they keep the profits and the taxpayer bails them out in drought years). Small business owners in cities don’t get Exceptional Circumstances funding – panel beaters, grocers, hardware shops etc simply go broke and that’s that.

So “poor farmers” is a relative concept – is it a social condition or simply yet another business with risks of operation. Obviously that Exceptional Circumstances schemes exist at all means that there is some “sympathy” for and “shared ethos” between bush and city for farmers and graziers; and ancillary arguments also exist for national food security and the viability of entire regional rural communities and associated towns. Given subsidisation of agriculture, such as in the USA and Europe, some have also argued that EC perhaps just levels the playing field in agricultural commodity trading – as Australia has among the highest rainfall variation in the world.

But many think that farmers have had more than their share of 1 in 20 or 1 in 25 year assistance. It has been perhaps impertinently suggested that some have had their next 200 years of assistance in the last 20 years. Which might imply the climate has changed, or that our knowledge of multi-year droughts is poor, or that we don’t understand the interaction with revocation rules, or simply that the scheme is rorted? All heresy of course.

So David, the areas declared and frequency of declarations are another data set you could put your statistics to use on. Have some producers had “too much” assistance. Is there a case to be put? You might be able to tell us.

I reckon there is a hard economic rationalist line afoot to ditch the assistance scheme and go laissez faire. Which means some farmers without adequate cash reserves would go the wall in the recent droughts. But do we subsidise other businesses who find conditions tough?

As to the temperature issue, papers by both Cai and Nicholls have talked about the high temperatures and high evaporative demands levels as being higher in the Millennium drought (2001-) compared to the Federation Drought (1895-1902). That’s all discussed in the bravenewclimate link comments.

But back to original issue on rainfall – I’m still not sure your statistical complaint is reasonable as you’re confounding a boundary prediction issue with an initial value prediction issue. So you might for example have an excellent tidal model of a beach (~ long term climate) – but at any moment your ability to predict the waves beyond upper and lower bounds is very poor. So the tides are the analogy with long term climate and the minute by minute waves analogous of annual and decadal noise. However, you still have knowledge of the tidal forcing boundaries.

Of course one of the best adaptations “our poor farmers” might be use of various forecasts of rainfall using ENSO related indices. 3-9 months ahead. So one might roll with the seasonal conditions. But I shudder to think what a statistician might make of all that – http://portal.iri.columbia.edu/portal/server.pt?open=512&objID=584&PageID=0&cached=true&mode=2#mme But the worry for all seasonal forecasters is that their ENSO indices may not be climate change proof. i.e. see the decrease in the Walker Circulation.

So rural groups are lobbying for ongoing support of assistance measures – what some might regard as agrarian socialism – capitalising gains and socialising losses ((in good seasons they keep the profits and the taxpayer bails them out in drought years). Small business owners in cities don’t get Exceptional Circumstances funding – panel beaters, grocers, hardware shops etc simply go broke and that’s that.

So “poor farmers” is a relative concept – is it a social condition or simply yet another business with risks of operation. Obviously that Exceptional Circumstances schemes exist at all means that there is some “sympathy” for and “shared ethos” between bush and city for farmers and graziers; and ancillary arguments also exist for national food security and the viability of entire regional rural communities and associated towns. Given subsidisation of agriculture, such as in the USA and Europe, some have also argued that EC perhaps just levels the playing field in agricultural commodity trading – as Australia has among the highest rainfall variation in the world.

But many think that farmers have had more than their share of 1 in 20 or 1 in 25 year assistance. It has been perhaps impertinently suggested that some have had their next 200 years of assistance in the last 20 years. Which might imply the climate has changed, or that our knowledge of multi-year droughts is poor, or that we don’t understand the interaction with revocation rules, or simply that the scheme is rorted? All heresy of course.

So David, the areas declared and frequency of declarations are another data set you could put your statistics to use on. Have some producers had “too much” assistance. Is there a case to be put? You might be able to tell us.

I reckon there is a hard economic rationalist line afoot to ditch the assistance scheme and go laissez faire. Which means some farmers without adequate cash reserves would go the wall in the recent droughts. But do we subsidise other businesses who find conditions tough?

As to the temperature issue, papers by both Cai and Nicholls have talked about the high temperatures and high evaporative demands levels as being higher in the Millennium drought (2001-) compared to the Federation Drought (1895-1902). That’s all discussed in the bravenewclimate link comments.

But back to original issue on rainfall – I’m still not sure your statistical complaint is reasonable as you’re confounding a boundary prediction issue with an initial value prediction issue. So you might for example have an excellent tidal model of a beach (~ long term climate) – but at any moment your ability to predict the waves beyond upper and lower bounds is very poor. So the tides are the analogy with long term climate and the minute by minute waves analogous of annual and decadal noise. However, you still have knowledge of the tidal forcing boundaries.

Of course one of the best adaptations “our poor farmers” might be use of various forecasts of rainfall using ENSO related indices. 3-9 months ahead. So one might roll with the seasonal conditions. But I shudder to think what a statistician might make of all that – http://portal.iri.columbia.edu/portal/server.pt?open=512&objID=584&PageID=0&cached=true&mode=2#mme But the worry for all seasonal forecasters is that their ENSO indices may not be climate change proof. i.e. see the decrease in the Walker Circulation.

Don’t you think people would like to know when scientists are blowing smoke?

http://www.petergallagher.com.au/index.php/site/farmers-unhappy-about-csiro-drought-alarmism/

Association president Jock Laurie says while the Climate Report does say ‘exceptionally high temperatures’ are likely to occur frequently, this does not equate to drought. Alarmist reporting has added confusion and pressure to farm families at a time when they can least afford it. ‘We have received a number of calls from members who were extremely agitated, confused and upset about the reports of drought every second year in future.’ Mr Laurie said.”

Good, thought provoking observations Luke.

David Stockwells last blog post..DECR: The message starts to slide

Don’t you think people would like to know when scientists are blowing smoke?

http://www.petergallagher.com.au/index.php/site/farmers-unhappy-about-csiro-drought-alarmism/

Association president Jock Laurie says while the Climate Report does say ‘exceptionally high temperatures’ are likely to occur frequently, this does not equate to drought. Alarmist reporting has added confusion and pressure to farm families at a time when they can least afford it. ‘We have received a number of calls from members who were extremely agitated, confused and upset about the reports of drought every second year in future.’ Mr Laurie said.”

Good, thought provoking observations Luke.

David Stockwells last blog post..DECR: The message starts to slide