So we now have data for roughly six months - rainfall data for six months, but dam inflow data for slightly less than that (I am extrapolating out to six months from the data that I have).
We have had 336.4 mm of rainfall so far this year, above the average by around 30 mm.
I have measured 29,500 megalitres of inflow. Extrapolating over the period that I have no data for, that suggests that we have had 32,000 megalitres of inflow this year so far.
While we have had an excellent year of rain, we are still headed for a very low year of dam inflow. If we get 700 mm of rainfall this year, we will get around 66,000 megalitres of inflow. But I do not think that that will happen. My prediction is still for less rainfall than 700 mm and inflow of around 60,000 megalitres.
The fact that this has been a high rainfall year but that inflow is low should be sending warning signals to all in the ACT about the risks that climate change poses to our water supply. While ACTEWAGL are taking steps to ensure our water security, they are not moving fast enough. Without public pressure, it is doubtful that the government will act.
Monday, July 5, 2010
Wednesday, June 16, 2010
Rainfall, runoff and prediction
Rainfall for the year thus far has been 313 mm, and we are expecting some more tomorrow, albeit it a small amount. Thus, we are on track towards 700 mm, but will probably not quite get there.
Runoff, according to my calculations, has been close to 27,750 megalitres. If we did get 700 mm of rainfall this year and if the ratio of runoff to rainfall held, then we would get close to 61,600 megalitres of runoff for the year. I think that we will likely fail to get this amount, and thus maintain my prediction of 60,000 megalitres of runoff.
To put this in perspective, this is about a third of the average runoff that Canberra usually recieves - although when I say 'usually' I mean 'for the period from 1940 to the mid-1990s'. The reason I say that is that our runoff has sharply declined in the last 15 years, as has our rainfall. It will be nice - if temporary, I believe - to get an above average rainfall year.
I would also like to raise one other point in this post. Some people are suggesting that water restrictions can be lifted in Canberra, as we have had lots of rain. However, they fail to take into account two things: the fact that the water restrictions have reduced water consumption in Canberra to around 45,000 megalitres annually and the fact that runoff is not recovering to levels previously comensurate with rainfall. If we are only getting 60,000 megalitres of water in a good rainfall year, it would be madness to remove water restrictions such that our water consumption rose to match that level. If it did, then bad years would be even worse - especially as it takes a year or two to 'train' the population to do what is required when water restrictions have to be reintroduced ...
Runoff, according to my calculations, has been close to 27,750 megalitres. If we did get 700 mm of rainfall this year and if the ratio of runoff to rainfall held, then we would get close to 61,600 megalitres of runoff for the year. I think that we will likely fail to get this amount, and thus maintain my prediction of 60,000 megalitres of runoff.
To put this in perspective, this is about a third of the average runoff that Canberra usually recieves - although when I say 'usually' I mean 'for the period from 1940 to the mid-1990s'. The reason I say that is that our runoff has sharply declined in the last 15 years, as has our rainfall. It will be nice - if temporary, I believe - to get an above average rainfall year.
I would also like to raise one other point in this post. Some people are suggesting that water restrictions can be lifted in Canberra, as we have had lots of rain. However, they fail to take into account two things: the fact that the water restrictions have reduced water consumption in Canberra to around 45,000 megalitres annually and the fact that runoff is not recovering to levels previously comensurate with rainfall. If we are only getting 60,000 megalitres of water in a good rainfall year, it would be madness to remove water restrictions such that our water consumption rose to match that level. If it did, then bad years would be even worse - especially as it takes a year or two to 'train' the population to do what is required when water restrictions have to be reintroduced ...
Wednesday, June 2, 2010
The wager
Willis Eschenbach has made a bet with me regarding ice extent. The proposition is that daily ice extent will fall below one million square kilometres by the end of the 2014 melt season. Willis has the negative; I have the affirmative. The bet is for $US100.
We will use the http://www.ijis.iarc.uaf.edu/en/home/seaice_extent.htm as our adjudicator, with the final values on 1 November 2014. Obviously, I can win the bet well before then - if sea ice drops below that value on 14 September this year, for example. If Willis wins, he will have to wait for his money until November 2014.
These are the relevant posts from WUWT:
Willis Eschenbach says:
June 1, 2010 at 2:53 am
David Gould says:
June 1, 2010 at 2:15 am
Nigel Harris,
I agree. It is exactly the pattern that we would expect to see. 2007 changed things. It was, indeed, a tipping point (and I know how much that term is loved here. :)). I am one of those alarmists who think that the Arctic will effectively be ice free at the end of the melt period very soon. My specific guess is 2014.
Care to put some money on that prediction? I’m a betting man … a hundred bucks says it won’t go below a million square km of ice by 2014?
And why is it “the pattern that we would expect to see”? Do you know of anyone who predicted it before 2007, anyone who foresaw that we would see a) increasing ice area, combined with b) greatly increased winter ice, and c) greatly reduced summer ice? This is historical revisionism.
Me, I think this new pattern reflects a change in satellites, or a change in procedures, or something like that. But hey, I’ve been wrong before …
1. David Gould says:
June 1, 2010 at 3:09 am
Willis Eschenbach,
No, I know of no specific prediction of this. However, ice cover is a two-dimensional model. Thus, if we have strong melting in the melt period, we would still expect the ice to recover on the surface during winter, and to roughly the same extent as usual – in other words, we would see a strong up and down signal, with more variance between the top and the bottom.
You are correct that there would be no expectation for a higher rebound in winter. That is more likely to be noise over the last couple of years.
As to a bet, $100 sounds fine. I am assuming that you are talking in US dollars.
And which dataset do you want to use? They are all somewhat different in the values that they give, as they all have slightly different procedures. These guys http://www.ijis.iarc.uaf.edu/en/home/seaice_extent.htm are fine with me. We should wait for corrections, though. I am not sure how long they take, but perhaps the data as presented on that site on 1 November 2014, my time (Australian time)?
We will use the http://www.ijis.iarc.uaf.edu/en/home/seaice_extent.htm as our adjudicator, with the final values on 1 November 2014. Obviously, I can win the bet well before then - if sea ice drops below that value on 14 September this year, for example. If Willis wins, he will have to wait for his money until November 2014.
These are the relevant posts from WUWT:
Willis Eschenbach says:
June 1, 2010 at 2:53 am
David Gould says:
June 1, 2010 at 2:15 am
Nigel Harris,
I agree. It is exactly the pattern that we would expect to see. 2007 changed things. It was, indeed, a tipping point (and I know how much that term is loved here. :)). I am one of those alarmists who think that the Arctic will effectively be ice free at the end of the melt period very soon. My specific guess is 2014.
Care to put some money on that prediction? I’m a betting man … a hundred bucks says it won’t go below a million square km of ice by 2014?
And why is it “the pattern that we would expect to see”? Do you know of anyone who predicted it before 2007, anyone who foresaw that we would see a) increasing ice area, combined with b) greatly increased winter ice, and c) greatly reduced summer ice? This is historical revisionism.
Me, I think this new pattern reflects a change in satellites, or a change in procedures, or something like that. But hey, I’ve been wrong before …
1. David Gould says:
June 1, 2010 at 3:09 am
Willis Eschenbach,
No, I know of no specific prediction of this. However, ice cover is a two-dimensional model. Thus, if we have strong melting in the melt period, we would still expect the ice to recover on the surface during winter, and to roughly the same extent as usual – in other words, we would see a strong up and down signal, with more variance between the top and the bottom.
You are correct that there would be no expectation for a higher rebound in winter. That is more likely to be noise over the last couple of years.
As to a bet, $100 sounds fine. I am assuming that you are talking in US dollars.
And which dataset do you want to use? They are all somewhat different in the values that they give, as they all have slightly different procedures. These guys http://www.ijis.iarc.uaf.edu/en/home/seaice_extent.htm are fine with me. We should wait for corrections, though. I am not sure how long they take, but perhaps the data as presented on that site on 1 November 2014, my time (Australian time)?
Monday, May 31, 2010
Sea ice volume
Arctic sea ice has an average volume of 28,600 cubic kilometres at the end of April, the freeze. It has an average volume of 14,400 at the end of September, the thaw. (note: this is the average over the satellite period, and it is likely that the averages were at least slightly higher immediately prior to this period).
Since the satellite record began, Arctic sea ice volume has declined at a rate of 340 cubic kilometres per year.
From 2002 to the start of 2010, sea ice volume declined at a rate of 800 cubic kilometres per year. At that rate, by the end of this year sea ice volume should be 7,900 cubic kilometres below the long-term average. Over the longer term, that would mean an end to summer Arctic sea ice by 2020 (more than 14,400 cubic kilometres of volume loss).
However, at present, sea ice volume is 9,500 cubic kilometres below the long-term average. If we assume that it stays there until the end of the year, we will have had three year's worth of decline in a single year.
I believe that my prediction for 2014 as the year we first get an ice-free summer is a pretty good one. It should be noted that the scientist who works most closely with the direct data (which is partly gathered from submarines from the US Navy using sonar to scan the ice from beneath) predicted an ice-free summer for 2013 way back in 2003. His name is Dr Wieslaw Maslowski.
A link to the page with my bet with Willis Eschenbach:
http://wattsupwiththat.com/2010/06/01/the-ice-who-came-in-from-the-cold/
Since the satellite record began, Arctic sea ice volume has declined at a rate of 340 cubic kilometres per year.
From 2002 to the start of 2010, sea ice volume declined at a rate of 800 cubic kilometres per year. At that rate, by the end of this year sea ice volume should be 7,900 cubic kilometres below the long-term average. Over the longer term, that would mean an end to summer Arctic sea ice by 2020 (more than 14,400 cubic kilometres of volume loss).
However, at present, sea ice volume is 9,500 cubic kilometres below the long-term average. If we assume that it stays there until the end of the year, we will have had three year's worth of decline in a single year.
I believe that my prediction for 2014 as the year we first get an ice-free summer is a pretty good one. It should be noted that the scientist who works most closely with the direct data (which is partly gathered from submarines from the US Navy using sonar to scan the ice from beneath) predicted an ice-free summer for 2013 way back in 2003. His name is Dr Wieslaw Maslowski.
A link to the page with my bet with Willis Eschenbach:
http://wattsupwiththat.com/2010/06/01/the-ice-who-came-in-from-the-cold/
Friday, May 28, 2010
Rain/Inflow thus far this year
We have had close to 270 mm of rainfall this year. With what is expected over the weekend, we may top 300 mm, which is very good for this time of the year.
Inflows to dams, however, are not proceeding as well. My previous prediction that we would hit close to 23,000 megalitres from the good rainfall in April did not eventuate. We have received 22,400 megalitres as of today. We should, based again on predictions for some catch-up and for the predicted rainfall, exceed 25,000 megalitres some time in the next two weeks.
I am downgrading my prediction for total inflow for the year to 60,000 megalitres. This has been a very bad year for megalitres of inflow per millimetre of rainfall - the worst, from what I can gather, on record. But we will still receive much more inflow than last year, simply because we are having an above average rainfall year.
Inflows to dams, however, are not proceeding as well. My previous prediction that we would hit close to 23,000 megalitres from the good rainfall in April did not eventuate. We have received 22,400 megalitres as of today. We should, based again on predictions for some catch-up and for the predicted rainfall, exceed 25,000 megalitres some time in the next two weeks.
I am downgrading my prediction for total inflow for the year to 60,000 megalitres. This has been a very bad year for megalitres of inflow per millimetre of rainfall - the worst, from what I can gather, on record. But we will still receive much more inflow than last year, simply because we are having an above average rainfall year.
Monday, May 17, 2010
Arctic Ice
This is not something that I have blogged on previously, but new information has come to my attention suggesting that arctic summer sea ice may be gone even before Canberra's water. The above graph is from here: http://psc.apl.washington.edu/ArcticSeaiceVolume/IceVolume.php
This graph shows the daily ice volume anomaly. At present, we are heading for record low ice volume by the end of this year's northern summer.
Compare the above graph with this image:
This second graph is from here: http://freshnor.dmi.dk/handout_freshnor.pdf
The second graph only uses data up until 2004. However, even given that, it is projecting the end of summer arctic sea ice by sometime this decade. The observations in the first graph not only confirm the projection based on the 2004 data but suggest that things have started to get worse. With the median projection is that summer sea ice will be gone by around 2014, it is getting more and more probable that it will disappear in the next two or three years.
For clarification, the two graphs have a different scale: 10^3 kilometres cubed for the first one and 10^4 kilometres cubed for the second one.
I should also add that personally my bet is for around 2014, even with the new data. Solar maximum will be somewhere around that time and that increases the likelihood of something bad happening.
And an interesting link on daily temperatures in the Arctic.
http://ocean.dmi.dk/arctic/meant80n.uk.php
And the link to the historical data for sea ice area and extent used by the nsidc:
ftp://sidads.colorado.edu/DATASETS/NOAA/G02135
Wednesday, May 5, 2010
Current rainfall versus inflow
For the year thus far, we have had 260.8 mm of rain, above the average. The indications are that we will get around 700 mm in total this year, assuming past years are a reasonable guide.
We have had 20,704 megalitres of dam inflow thus far this year, although I would add around 2,000 megalitres to that for the rainfall that we have received in recent days. Call it 23,000. This means that I project we will get 65,260 megalitres of inflow this year, much more than last year. However, this would still equate to less than 35 per cent of average annual inflow, showing the dangerous state of our water situation.
To spell out what this means, we used to get about 180,000 megalitres of inflow per year, on average, with an average rainfall of around 630 mm per year. If the year plays out roughly as I expect, we will be getting 10 per cent more rain than that average but only around a third of the average inflow into our dams.
Something is broken in the hyrdological system. It could be the subsurface soil structure; it could be transpiration and evaporation rates; it could be that *where* the rain is falling has shifted. Is it climate change? Yes. Is it going to get worse? Yes.
Take action now, people. If we wait until mid-decade, Canberra will be facing a disastrous water situation.
We have had 20,704 megalitres of dam inflow thus far this year, although I would add around 2,000 megalitres to that for the rainfall that we have received in recent days. Call it 23,000. This means that I project we will get 65,260 megalitres of inflow this year, much more than last year. However, this would still equate to less than 35 per cent of average annual inflow, showing the dangerous state of our water situation.
To spell out what this means, we used to get about 180,000 megalitres of inflow per year, on average, with an average rainfall of around 630 mm per year. If the year plays out roughly as I expect, we will be getting 10 per cent more rain than that average but only around a third of the average inflow into our dams.
Something is broken in the hyrdological system. It could be the subsurface soil structure; it could be transpiration and evaporation rates; it could be that *where* the rain is falling has shifted. Is it climate change? Yes. Is it going to get worse? Yes.
Take action now, people. If we wait until mid-decade, Canberra will be facing a disastrous water situation.
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