Wednesday, December 22, 2010

Rainfall and inflow: a summary

At present, I am still waiting on data. However, if I combine the two stations at this point, I get a value of 861.8 millimetres of rainfall thus far this year. Based on extrapolation, this would indicate that we have received approximately 160,000 megalitres of inflow.

The rainfall would thus be enough to blow through my limit of 850 millimetres. However, I am not certain that I am willing to concede as yet, even though there are nine days to go for the year and a little more rain is predicted to fall just after Christmas. As the station that I am using showed around 100 millimetres less rainfall by November, it is possibly that it has received 12 millimetres less in December. But we will see. ;)

Temperature datasets

As I keep losing track of these, I want to put them all in one place:






STAR mid-troposphere data (this is not directly comparable with UAH, but can be compared with the RSS mid-troposphere data).

Monday, December 13, 2010

Oops ...

I have made an embarrassing discovery: I have been using the wrong rainfall data for Canberra. The rainfall data that I have been using was from here:

I had made the assumption that this data was the same as the date from here:

This is not the case, as I would have realised had I been paying attention:

"Source of data

Observations were drawn from Canberra Airport {station 070351}.

Weather observations for Canberra were previously taken at a nearby site {number 070014}. These can be seen on the "Canberra Airport" Daily Weather Observations; you may need to consult these to get all the relevant data."

My predictions were based on the data from station 070014, as the data from station 070351 only goes back to the middle of 2008. This can be seen here:

So, at the moment it is not clear that my prediction has been falsified. I think that it has, but I will not know for certain until some time early next year.

To be sure that this is the data that I used, please read this post:

You can check the 10-year averages for temperature and rainfall from the data obtained from site 070014 and see that the slope between them is practically identical to the one displayed in the above post. The very small difference is due to slight corrections in the 2009 data, the latter part of it being still provisional in January 2010.

To go back a step, you can bring up the data by entering the site number into this web page:

So: we will soon see if my prediction has been falsified (which it likely has been).

Another consequence of this error on my part is that inflow for the rest of the year will be higher than it otherwise would have been, as the rate of inflow for megalitre has increased (due to there having been less rainfall at station 070014). Thus, my estimate for the inflow - and I must estimate it, because it cannot be measured as the dams are all above 100 per cent - will be greater. At present, that does not matter, as we have not had much rain since reaching 100 per cent. But rain is expected soon.

Tuesday, December 7, 2010

Prediction Shortgevity

Following on from my discussion about longevity comes something about the opposite: my short-lived prediction regarding Canberra rainfall. We have received a staggering 899 mm thus far this year, blowing past my 850 mm limit. Thus, my statistical analysis that pointed to technical desert conditions for Canberra by 2050 has been proven false.

So the key now for me is to keep watching to see where the evidence points. What is obvious now is that my conclusion was not warranted from the data, and I needed more data - data which I now have. But that is how science works: you build a model from observations and use that model to make predictions about the future, understanding that falsifying those predictions falsifies the model.

I will continue to track the rainfall and inflow (although with Canberra dams now at 100 per cent, tracking excess inflow is a little difficult - I will have to make some assumptions about extra inflow, and I am looking at what those assumptions might be at the moment.) We have received 142,000 megalitres of inflow thus far this year. What I might do is slightly increase the overall average to account for lost water. It should be pointed out that this amount of inflow is still significantly lower than the average.

Wednesday, December 1, 2010

Life expectancy for my age cohort

I have just been doing some calculations on my age cohort based on the observed improvements in life expectancy for Australians over the last 20 years. If those improvements are replicated every 20 years over the next century, the median life expectancy of all those aged 40 becomes 127.5, with those people living most of the last 40 years of their lives with a health approximating those in their early 70s today. They would have reached statistical immortality (see a previous post on this) at around age 90. Some of that cohort should live much longer than that, and there is a slim possibility that some of them could be alive hundreds of years from now.

That gives me reason to hope that I might be alive - doddering, perhaps, and dreaming of the past but alive - in the year 2100, an interesting milestone to me because (a) I am human and love nice round numbers and (b) it is a year about which there is much speculation in science fiction novels and roleplaying games (see (a)).

While I am a pessimist regarding climate change, I am also an optimist: while I believe that humans are going to cause a lot of suffering for ourselves and other species over the next century, I think that we as a species will pull through it and have an amazing history to write on our planet, on other locations in the solar system and among the stars. I would like to see more of that history. :)

Tuesday, November 30, 2010

Topping 700 mm - rainfall and inflow update

I have been holding off for a little while waiting for rainfall to top 700 mm for the year. And it has done so with a bang: we have now had 744.6 mm of rainfall this year, which is a very good year indeed, and we still have a month to go, which means that 800 mm looks to be well within reach. And it is possible that we will top 850 mm, blowing my statistical predictions out of the water, so to speak. But we will see.

Regarding inflow, the full inflow from the last two days rain has not yet been measured, but we are currently sitting at around 122500 megalitree for the year. This is still below what we would have expected from such an amount for rain, but it is still almost triple what we had last year.

Wednesday, November 24, 2010

Statistical immortality

Okay: first up, statistical immortality does not mean that you will live forever. But it does open up the possibility for people to live very long lives indeed.

What is statistical immortality? Statistical immortality, as I define it, is where the pace of increase in life expectancy reaches parity - in other words, life expectancy increases by a year every year.

At present, life expectancy is increasing by around one year every three years for those in rich Western nations like Australia. Most of this increase *not* in reduction in infant mortality - we have almost reached the limit of improvement there. Rather, most of it is coming at the other end of life: we are not dying when we used to.

To illustrate exactly what I mean, I will go through an example. Imagine a person who is 60. They have a life expectancy of a further 22.9 years. What this means is that some people of their age will die prior to 82.9 (and some will die before reaching 61!) and some will live longer, but that the average age of death for the group as a whole will be 82.9.

Looking at the table from the ABS, around 53 per cent would still be alive at 82.9. However, let us assume that by the time this cohort was 65, their life expectancy had increased five years to 87.9. Only around 3 per cent of them would be dead at this point. If we take them through five year steps, this pattern repeats, with a small per cent of them dying and the life expectancy of the rest extending further and further into the future.

Even with this small death rate, however, eventually the whole cohort would be dead. But this would take a significant amount of time. From an original cohort of 100,000 at age 60, there would still be around 50,000 alive after 23 steps - 115 years. So we are looking at a median age (the age by which half of them will be dead) of death for this cohort of 197.9.

Now, 197.9 is not immortality. So why would I call it statistical immortality? For two reasons: firstly, if you had an infinitely sized population (mathematicians like infinity) some of that cohort would be expected to survive forever (in fact, an infinite number of them :)); and secondly, this is so far beyond the usual life of a human being that it moves significant numbers of the population (50 per cent of this particular cohort) into a world that we can barely begin to imagine - one in which all sorts of other pathways would almost certainly open up for them.

Returning to climate change, the rapid increases in life expectancy that we are experiencing in the West at present makes it almost certain that, if you are reading this, you will be alive to see some of the worst effects. And then life expectancy may start to drop again ...

Tuesday, November 23, 2010

Life expectancy

One of the interesting things - to me - about the climate change debate is how many people seem to think that the effects of climate change will not be experienced by them but rather by their children or grandchildren.

These statements are even made, perhaps rhetorically, perhaps not, by people who are authorities on the science. Storms of my grandchildren is a book written by James Hansen, the head of the Goddard Institute and the man who runs one of the five major global temperature data sets, GISSTemp. While I am sure that James Hansen is aware of what climate change is doing to the world now, the emphasis is on what will occur many decades into the future. (To be fair, Hansen is 69, so his grandchildren are likely around 10 or so).

However, even someone who is 69 and who lives in the wealthy west has a reasonable chance of living for another 20 years.

And that leads me to the point of this post: examining life expectancy.

Let us examine the life expectancy by age tables published by the ABS here:

What they show us is that an Australian male (and James Hansen is American, but the difference will not be all that great) aged 69 has a life expectancy of a further 15.7 years.

The tables towards the bottom of the page show something even more interesting. They show that as you get older the age at which you are expected to die increases quite signficantly.

For example, someone who was 40 in 1989 was expected to die at age 75.9. Those members of that demographic who reached the age of 60 in 2009 were expected to die at age 82.9, an increase of seven years in a 20-year period.

If you think about, this is at least partly to be expected. If you survive from age 40 to age 60, the most obvious conclusion is that you have not died. Thus, you have successfully avoided the dangers that have taken the lives of others in your demographic. Those who died were taken into account in working out the expected age of death of 75.9. They no longer exist, and so the expected age of death for the survivors must be higher than 75.9.

However, an increase of seven years seems quite large. Think about it this way: once we reach a point where our average age of death increases by one year for every year that goes by, we will have reached statistical immortality (in a way - there will still be deaths, but they will be compensated for, in the statistical sense, by faster and faster increases in life expectancy). Seven in 20 is a reasonable step towards that mark. And the figures for those aged 60 in 1989 who survived to 80 in 2009 are even more interesting: the expected age at death increased by 10 years in those 20 years.

What is going on here? Well, apart from death winnowing out people from the second set of statistics (ie, not everyone is making it to 80), medical technology is improving quite rapidly. This is expanding life expectancy, and it is particularly doing so for those aged 40 or above.

Having done some calculations based on these tables, it is my conclusion that someone who is aged approximately 40 today has a 25 per cent chance of living to 120. These calculations assume the continuation of the steady increase in life expectancies, with no spectacular breakthroughs.

It is also my calculation that 'statistical immortality' will be acheived in 100 years, with those aged around 20 today having about a 30 per cent chance of reaching that point.

And I will write a more detailed post about what I mean by 'statistical immortality' in the near future.

Wednesday, October 20, 2010

Current inflow/rainfall totals

By my calculations, we have had around 112,500 megalitres of inflow so far this year, from around 630 mm of rainfall. Projected inflow is close to 150,000, which would be up around 85 per cent of the long-term average - a very good year, however, compared to more recent times.

Monday, October 11, 2010

Inflow and rainfall update

We are now approaching 95,000 megalitres of inflow for the year, having received 550.6 millimetres of rainfall. What has occurred in recent months has been large falls of rain combined with a high ratio of inflow per millimetre of rainfall. This could indicate that the subsurface soils in and around the ACT are now saturated and are acting more like they did 20 years ago with regards to moisture flows and retention.

However, it should be pointed out that even if we get 750 mm of rainfall we are unlikely to get more than 75 per cent of the average inflow for the region. This shows in how parlous a state our water system still is in - even after the brilliant year of rainfall that 2010 has been.

One year of data, and it has not been the data that I expected for this year. But we will get a better picture as we get more data. I will be very interested in seeing what sort of rainfall we get in the early part of next year, particularly March/April, and the corresponding inflows. If the subsurface is saturated, even a few months of very hot weather should not alter it all that much. We should see better inflows than at the same period last year. If we do not, that will also tell us something about what is going on beneath our feet.

Tuesday, September 7, 2010

More rain; heaps more rain!

As I said in my previous post, we are getting lots of rain at the moment. We had a huge amount of rain over the weekend, and we have now had 527.8 mm this year so far. If this continues, we should get close to 800 mm this year, and we might go over that.

Regarding inflow, we have had much more than I expected, and that is understating things. According to my calculations, we have now had close to 70,000 megalitres of inflow this year already, which indicates that we should top the 100,000 mark and then some. It should be noted, as ever, that the average inflow into Canberra dams is 180,000 megalitres, which would still mean that we are seeing a deficit. But that could simply be because of the terrible drying of the system that took place over the last 20 years, and we might be building towards a recovery.

So at present my predictions look very shaky indeed.

Friday, August 13, 2010

Rainfall and inflow update

We are getting *a lot* of rain, which is most certainly not what I expected for this year. We have had
490.4 mm of rain this year so far, which points to a final year tally of close to 750 mm. While la Nina may explain the rain for July and so far this August, it does not explain the very large amount of rain that we received early in the year.

Inflow so far is slightly under 48,000 megalitres. This indicates that we could well get over 70,000 megalitres for the year, which would be fantastic. However, it should again be noted that the Canberra average prior to the year 2000 was 180,000 megalitres ...

What does this amount of rainfall and inflow imply for my theory on the effect that climate change is having and will have on Canberra? Firstly, one year does not alter a trend. However, as I have laid out previously, a theory must be falsifiable for it to be of any value.

As my criteria lay out, if this year has rainfall of 850 mm then my theory will not likely be true. Further, if the next few years push the five-year average to 670 mm or greater then my theory will not likely be true. This will be something that I will keep an eye on.

Tuesday, August 3, 2010

Update on inflow/rainfall

We have now had seven months of the year. We have had well above average rainfall, over 400 mm, when the average is around 350 mm. This has given us inflows in the last seven months that are approaching the total inflows that we had last year. Currently, we sit on 42,800 megalitres; last year, we had 43,200 megalitres.

However, we are still well below the average inflow for this time of year, which is 110,000 megalitres.

One other point of interest: we are now climbing above the megalitre per millimetre rate from last year. This is an indication, perhaps, that the ground is getting wetter and some of the damage is healing. But it should be noted that we are still well below the average.

Over the next few months, La Nina is expected to have a strong influence. This means that it is more likely than not for there to be above average rainfall in the Canberra region. So my prediction for lower rainfall than 700 mm for this year may well be challenged. We will see. :)

Friday, July 23, 2010

Climate change and the election: who to vote for?

This is a post that I was not going to write. But I think at this point I have no choice. I am recommending a vote for the Greens in both the House and the Senate. And in terms of preferences, my strong feeling is that neither major party should be preferenced. While not preferencing them in the House is impossible, it is possible to leave the two major parties unpreferenced in the Senate if there are 20 candidates. This is because the rule is that you have to preference 90 per cent of the candidates. So, if there are 20, you can leave two spaces blank.

This is, however, only really possible in the ACT and the Northern Territory, as there will only be two candidates from each major party. Given that there will be 6 candidates from each major party in the states, it might be a little difficult to dump all of them - there would have to be 100 candidates. But you can at least preference them in the reverse order to that which they tell you to on their how-to-vote cards.

Note that your preferences are not determined by other parties unless you let them. If you vote above the line in the Senate, then sure, the party that gets your vote will decide where your preference ends up. If you are not lazy, however, and can spare the time to write a few numbers in boxes, you get to decide where your preference goes. It astonishes me how many people do not understand this point - the fault of the media, I guess, and of parties who want others to believe that they decide preferences.

So: vote Green. And do not preference the major parties, except in reverse order.

Monday, July 12, 2010

How to show that Arctic warming is affected by atmospheric CO2?

It is often asked by those who are sceptical of the warming influence of CO2 for evidence that the recent rapid melting of the Arctic is being caused by human created greenhouse gases. The above graph is something that everyone interested in this issue should pay attention to. What is shows is that there is a statistically significant correlation between the natural logarithm of atmospheric concentrations of CO2 and the temperature of the Arctic as measured by UAH. And the temperature of the Arctic certainly has an impact on Arctic ice. The data is taken from these two sites:

While this graph is not proof of a link, it is indeed evidence - all that science can provide. It should be noted that what the slope of the graph shows is that the climate sensitivity of the Artic region is seven degrees. In other words, for every doubling of CO2, the temperature of the Arctic as measured by satellite is projected to increase by seven degrees celsius. The speed of Arctic warming is thus between two and three times that of the earth as a whole - the range that was projected by the IPCC ...)

(The calculation of this is done as follows: take the slope, which is approximately 10, and multiply it by .7 - the natural logarithm of two, a doubling. This gives you the projected increase in temperature per doubling.)

Monday, July 5, 2010

Inflow into dams and rainfall for the first half of the year

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.

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 ...

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 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 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:

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.

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:

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:

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.

And the link to the historical data for sea ice area and extent used by the nsidc:

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.

Thursday, March 18, 2010

Runoff and rainfall for the year thus far

The runoff from the March rains has ended. Thus, I think that this is a reasonable time to record how much runoff we have had for the year at this point.

The total runoff that I have tracked is: 16560.28 megalitres

However, this does not take into account runoff from rainfall in January and early February. ACTEW said that the runoff from that rainfall was 'effectively zero'. However, as I am not sure what they mean by that - they might simply mean 'it was very low - I am going to use the runoff per millimetre of rainfall rate to calculate the runoff.

This brings my total runoff for the year to: 19281.05045 megalitres.

This runoff is the result of 180 mm of rainfall.

It should be noted that we only got 43240 megalitres of rainfall last year, so we are doing much better by comparison.

Tuesday, March 9, 2010

March rainfall and runoff

There have now been two falls of rain in March. The first was 9.6 mm. This resulted in runoff of 457 megalitres, which was very low (half of the predicted runoff based on last year's runoff and rainfall figures.)

Then on 5,6,7 and 8 of March we had a combined rainfall of 38.2 (it was a fair bit more than that at our house, but I am going with the station that the BOM use.)

I am now tracking the runoff from this.

Currently, we have had 155.2 mm of rainfall since I started analysing this (way above average for the period) and less than 11,485 megalitres of runoff (way below average for that amount of rainfall, and below the megalitre per millimetre of runoff that we acheived last year, in what was a very low year.)

I expect that rainfall will be above average for the year, but runoff to be below average - well below average.

Friday, February 26, 2010

The February Storm

On the weekend of the 13 and 14 February, Canberra enjoyed heavy rainfall, with 107.4 mm falling in the space of 50 hours or so.

Since then, I have been tracking inflows into Canberra dams to see how it compares with past inflows.

Today, I believe we have gained the vast majority of that inflow - we might get another 50 megalitres or so over the next couple of days, but probably not that even that much.

From this 107.4 mm of rainfall, Canberra dams received 8,756.6 megalitres of water. By comparison, from the 442.4 mm of rainfall in 2009, Canberra dams recieved 43,240 megalitres of water. This was a terrible year for inflows: 23 per cent of the long-term average.

However, if we recieve the same amount of rain this year as we did last year, and the inflow from that rainfall matches in a megalitre per millimetre sense what went into Canberra dams from the February storm, the percentage would drop below 20 per cent to 19.2 per cent.

Now, this storm was at the tail end of summer, so it can be assumed that the ground was thirsty for water. It may also be the case that big storms provide a lower level of inflow than smaller yet more frequent bursts. However, at this point, the storm has not provided much reason to be hopeful about the future of inflows in Canberra.

It of course remains to be seen whether we will get more rain this year than last year - the odds favour it, as currently (because of the storm) we are about 30 mm above average for the year so far. I will continue to track rainfall versus runoff for the course of this year to see if I can work out any patterns (unlikely from a year of data, but if they are strong they might show up.)

Monday, February 22, 2010

Why we lost

Those of us on the side of the debate who believe:

1.) the earth is warming;
2.) this warming is caused by increasing CO2;
3.) this increase in CO2 is being caused by human activity; and
4.) this warming will be bad for us and for many species;

have lost the debate, at least in the short term, and that may well mean that we have lost it for the long term - at least for the sake of the suffering of many people and many animals.

Why did we lose?

People often talk about people like Carl Sagan and Richard Dawkins, and wonder why we cannot come up with climate science communicators of their calibre. The problem here is not really to do with the calibre of the people - there are some excellent communicators of climate science; you do not have to look far to find them. The problem is to do with the comparative difficulty of explaining and selling - yes, it is about selling -cosmology, evolution and climate science.

Cosmology and evolution can both in their own ways be inspiring. They are answers to deep questions at the core of what it means to be human. They are able to be built as powerful and, more importantly, positive myths - even more powerful because they are true. Who has not looked up at the stars in wonder? Who has not thought about the diversity of life on this planet of ours and wondered where it came from? With these powerful stories as a base, a skilled communicator can move the world.

But climate science does not connect with humanity in the same fashion. We are not the end point in the story - we are star stuff and we are an endpoint of billions of years of the evolutionary process, but we are not 'climate stuff'. There is no place in the climate story for humans ... except as the villains of the piece. And there is the nub. Humans do not want to be the villains. We want to identify with the good guys; we want to be inspired.

Thursday, February 18, 2010

Submission to the ACT Legislative Assembly

A submission that I made to the ACT Legislative Assembly has now been made publicly available. It is here:

There are two mistakes in it, annoyingly. I forgot to alter 'one per cent' to 'five per cent' in the section on global warming and Canberra daytime temperatures. And in the references section, there is a typo, with 'factormation' instead of 'information' - maybe it will become a new word, though. ;)

I also did not explain something that I should have done. This was that, while changes in global temperatures cause changes in local temperatures and while changes in local temperatures cause changes in local rainfall, it is difficult to link changes in global temperatures with change in local rainfall *directly*. This is because there are many other factors. Given R^2 values of around 40 per cent for the two known relationships, there will be at best a 16% value for the correlation between the two more distant numbers - and it is likely to be much lower than that.

More to be added.

Tuesday, February 9, 2010

"2030 climate change may have already occurred in the Canberra region" ...

This is a submission to the ACT legislative assembly by the managing director of ACTEW Corporation, Mark Sullivan. It contains much of what I have already posted on. However, there is one key paragraph:

"It would be prudent in a risk management framework for Government to identify policies and implement programs based on the assumption that 2030 climate change may have already occurred in the Canberra region."

I wonder if the public of the ACT understands this; I wonder if the federal government understands this. We know that the federal opposition sure doesn't ...

The step change in WA

The above article demonstrates that climate change has already affected precipitation in Australia. Whether Canberra has been similarly affected is not known. But as I have previously reported the CSIRO believes, based on the statistics, that it is possible that Canberra has undergone a step change in precipitation.

They are understandably cautious: scientists usually are, and scientists working for government agencies even more so. But I think that the statistical evidence is very clear indeed. While I am unable to detect the mechanism by simply using statistical data, it is possible that a mechanism similar to that discussed in the article above is operating here.

Climate change is not some distant threat. Climate change is here.

Monday, February 8, 2010

Assumptions regarding Canberra rainfall predictions

I have made the prediction on this blog that Canberra inflow - the water that ends up in dams - will effectively drop to zero by around 2017. It should be noted that this is not a solid number - there is a considerable statistical range over which this could happen. But 2017 is the mean.

There are a number of assumptions underpinning this prediction. Any one of those assumptions might be wrong.

The basic argument is that rainfall is declining due to climate change and that declines in rainfall cause declines in runoff. This decline has been observed.

There are three sets of arguments running here.

Argument 1

Premise 1: Climate change will continue.
Premise 2: If climate change continues, daytime temperatures in Canberra will continue to increase.
Conclusion 1: Therefore, daytime temperatures in Canberra will continue to increase.

Argument 2

Premise 3: Increases in daytime temperatures reduce rainfall.
Premise 4: Reductions in rainfall lead to reductions in runoff.
Conclusion 2: Increases in daytime temperatures reduce runoff.

Argument 3:

Premise 5: Daytime temperatures in Canberra will continue to increase.
Premise 6: Increases in day time temperatures reduce runoff.
Conclusion 3: Runoff will reduce.

(Note how conclusions 1 and 2 became premises 5 and 6.)

There are other assumptions here - the premises have not been spelt out completely. The main assumptions involve the rate at which day time temperatures will increase and the rate at which those temperature increases will cause rainfall, and hence runoff, to decline. The rates predicted are based on empirical observation.

The problem with this is that the future may well differ from the past in this respect. Just as it is possible that we have undergone a step change in climate here in Canberra, so it is also possible that we will undergo another one soon.

Further, it is possible that there is a limit at which daytime temperature ceases to become the dominant driver of rainfall. Thus, a one degree rise in temperature in the future may not have the same effect as a one degree rise in the past.

So, my prediction could well be wrong. But that is how science advances: by linking empirical observation to a theoretical model and then testing that theoretical model against further empirical observation. At the moment, my theoretical model - based in empirical observation - is predicting an end to Canberra runoff by 2017.

Friday, February 5, 2010

The graphs

The first graph is for rainfall versus inflow for the last 14 years (23 years worth of data). As you can see, the R^2 value is .93, which is a very good fit.

The second graph is for rainfall decline over time for the same period. Again, there is a very good fit.

I have extended the graphs forward so that the conclusions of the previous post can be seen. By 2017, rainfall will drop below 450 mm. By that point, runoff will effectively be zero.

Worse than I thought

This report from ACTEW (Australian Capital Territory Electricity and Water) is essential reading for anyone interested in the future of Canberra's water supply.

Of particular note is this:

"Whilst global warming progresses proportionally to the build up of greenhouse gases in the atmosphere, it can result in rapid ‘step’ climate changes in a particular region. It is possible that the recent drought represents a shift in climate for Canberra. The past 5 to 10 years are clearly the most severe long-term dry period in the 1871 to present extended historic record inflow sequence."

I have looked at the data on inflows in this report at page 23 (PDF page 25) and tried to estimate the figures from the graph. While I may be out somewhat, it will not be by all that much (although I wish that they had included the data or at least a reference to it). When graphing the values for the last little while (14 years of 10-year averages, which includes 23 years of data) against the rolling 10-year rainfall figures for Canberra, I found that every 1 mm decline in the rainfall average means around a 70 megalitre decline in inflows. This means that when the 10-year average rainfall drops to around  450 mm, inflows drop to zero. Zero.

If the current trend in declining rainfall continues, this point will be reached by 2017, eight years from now. You heard it here first.

Again, the error margins here are reasonably large because of the autocorrelation in the 10-year averages. However, this is significantly sooner than my previous estimate of 2030 for zero inflow into Canberra dams.

Thursday, February 4, 2010

An image showing the last two years of Australian rainfall

Note the low rainfall in the south-east of Australia and the high rainfall in the north - this is the pattern of rainfall that climate change models predicted would occur as the world warmed. We are experiencing climate change now... 

Wednesday, February 3, 2010

Richard B. Alley: The biggest Control Knob: Carbon Dioxide in Earth’s Climate History (written summary) (video) (I now cannot get the video to work - I will keep the link here, though, and check back in a few days)

A fantastic summary of why we know CO2 causes warming, why we know the climate sensitivity is high and why we know that this century is going to be hot unless we do something ... fast.

Tuesday, February 2, 2010

Testing hypotheses

I have presented the hypothesis on this blog that Canberra will become a desert by mid century if greenhouse gas emissions are not dramatically reduced.

A test of whether a claim is scientific or not is whether there are empirical observations that would demonstrate that the claim is unlikely to be true. In the case of my hypothesis, there are indeed empirical observations that would demonstrate this, and I will list some of them here.

1.) Obviously, if the five-year average rainfall has not fallen to 250 mm or lower by 2050, my hypothesis would be 'unlikely to be true'. I would suggest that there is some wiggle-room here - if five-year average rainfall has fallen to 253 mm, then I would still claim that my hypothesis is likely to be correct. However, if we set 265 mm as the cut-off, that makes things very clear.

2.) The above empirical observation cannot be made until 2050, which is a fair way off. There are, however, observations that can be made sooner that would demonstrate that the claim is unlikely to be true. A year with rainfall of 850 mm or above would be just such an empirical observation. Further, I would suggest that for every five years that passes, we can reduce this by 30 mm. In other words, for the years 2010-2014, if any one of those has 850 mm of rainfall or above, my hypothesis is unlikely to be true; for the years 2015-2019, if any one of those has 820 mm rainfall or above, my hypothesis is unlikely to be true.

Five years out of 70 have had rainfall over 850 mm, so on average one year in 14 should meet that criteria.

It should be noted that these are the current numbers - they will not increase, but they may decrease as more data comes in that shows definitely that the variance in annual rainfall has declined - at the moment, these figures rely on the current observed variance. By way of an explanation, currently, the standard deviation is about 170 mm, meaning that 95 per cent of the time the rainfall will be within the range of the average plus or minus 340 mm.

3.) If any five-year average is 670 mm or greater. This figure will again decline by 30 mm for every five years that passes.

21 five-year periods out of 66 have had an average of 670 mm or greater, so one in three.

4.) If any 10-year average is 600 mm or greater. This figure will again decline by 30 mm for every five years that passes.

44 10-year periods out of 61 have had an average of 600 mm or greater, so more than two in three.

This should be sufficient for now. There are other possible criteria, such as rainfall in multiple five-year periods in a row, but they are mostly covered by the 10-year average situation.

Monday, February 1, 2010

Local short-term drought or long-term regional climate shift?

One question is thrown up by my analysis of Canberra rainfall over the last little while: isn't this simply a local drought that will pass at some point? If it is a local drought that will pass, as droughts do, then my analysis for the long term is flawed and we are likely to be having more rain in 2050 than we have had over the last few years.

However, there are two major lines of evidence that point to our recent weather ('recent' being weather over the last 15 years or so) being a long-term climate shift rather than short-term drought.

The first is the relationship between Canberra day-time temperature and rainfall. As temperature rises, rainfall decreases. This relationship has held for the entire period of record. We know that the global climate is warming and that locally we will continue to experience rising temperatures - indeed, we know that Canberra is warming and will continue to warm at two or more times the global average. So, if the relationship between temperature and rainfall holds - and the evidence is that it will - rainfall will continue to decline.

The second line of evidence is the unprecedented nature of the current rainfall deficit. There has never been a drought of this magnitude or of this length of time in the 70-year record. Indeed, prior to this drought, only eight five-year periods had qualified as drought periods. This drought has covered 6 consecutive five-year periods (which is, for clarification, 10 years in total). The drought during WWII covered 4 consecutive five-year periods, or eight years in total. And there is no sign that our current drought is going to end this year.

To compare further, the average yearly rainfall during the WWII drought was 530 mm. For the current period, the average yearly rainfall has been 519 mm. The current period has also had a much lower variability in yearly rainfall - all years in the decade have had below average rainfall except one, while in the eight years of the WWII drought, two years had above average rainfall.

The evidence is that this is not simply a local short-term drought. Rather, what we are experiencing is a long-term climate shift that is affecting not just Canberra but Victoria and the whole of southern NSW. Climate change is here.

Friday, January 29, 2010

Rainfall, evaporation and runoff

Rainfall turns into two things: evaporation and runoff. In Australia, across the entire continent on average 65 per cent of rainfall evaporates and 35 per cent becomes runoff.

As temperature increase, however, the percentage of evaporation tends to increase (there are limiting factors to this - if the atmosphere already contains lots of H2O, evaporation will be slower). Examining the recent evaporation history of the Canberra region, I found that evaporation rates have increased to around four per cent above the long-term average (we have data from 1967 to 2007 inclusive).

Based on the Australian average, this would mean a seven per cent decline in runoff (assuming constant rainfall, of course). Instead of a ratio of evaporation to rainfall of 65:35, we would have a ratio of 67.5:32.5.

I had a look at what this means for the trend in runoff. Over the last 20 years, when changes in evaporation are taken into account, runoff has decreased by around 9 mm per year. The long-term average is 224 mm of runoff per year. At present, we have an average runoff of 166 mm, which is the lowest recorded (note that we only have records for evaporation going back to 1967). This is two standard deviations below the mean.

If the trend continues, effectively we will have no runoff by 2030. None.

The error margins for this estimate are quite large, as we only have a relatively small amount of information. Further, while evaporation rates rise with temperature, they are also affected by things such as the amount of sunlight that reaches the earth. Global dimming, probably caused by aerosols, reduced evaporation between 1970 and 1990, and then as aerosols started to decline somewhat evaporation increased.

However, these trends should be closely examined. And there should be more discussion from government about them and what they are doing to protect Canberra from the effects of climate change. (And I should say here that these effects are almost inevitable at this point, as politically it is unlikely that we are going to significantly slow greenhouse gas emissions between now and 2030.)

More on the future of Canberra rainfall

The above publication, from 2004, discusses options for the future of Canberra's water supply. There are two things that stand out for me: firstly, the area that they are counting on for future water supplies has declined since 2003 from a five-year annual average of 830 mm to 630 mm (and 830 mm was already 90 mm below the long-term average ...); and secondly, the worst-case scenario prediction for rainfall decline for Canberra by 2030 is 9 per cent.

The data for the Brindabella region is here:

Now, it is possible that we are only talking about a short-term fluctuation in rainfall over the last little while, and that there will be a rebound in the near future that will take us back up to that 9 per cent decline or better position by 2030. But the evidence is that this will not be the case: it looks as though rainfall patterns in Australia have altered.

It should be noted that the predictions from the CSIRO and the IPCC are based on models that have very poor resolution at local levels. They can predict global climate quite well, but for regional climate - and regional rainfall/precipitation in particular - they are not able to do very well.

Rainfall decline versus runoff decline

I have been having a look at what happens to runoff, which is the water that ends up in our rivers and dams, when rainfall declines. There are three historical periods in Australia in the Murray-Darling Basin for which we have information on rainfall and runoff.

In the period 1895-1904 - the Federation drought - rainfall was 11 per cent below the long-term average. Runoff during this period was 31 per cent below the long-term average.

In the period 1937 to 1946, rainfall was 14 per cent below the long-term average. Runoff was 22 per cent below the long-term average.

In the period 1997-2006, rainfall was 13 per cent below the long-term average. Runoff was 39 per cent below the long-term average.

While there is a lack of consistency in the periods, what is clear is that a one per cent decrease in rainfall does not equate to a single per cent decline in runoff. Indeed, for the current period, a one per cent decrease in average rainfall has equated to a three per cent decline in runoff. This has potentially disastrous implications for areas such as Canberra, where the projections suggest a decrease in rainfall of 50 per cent by 2050.

I am hoping to get more information from ACTAGL regarding historical dam levels. This should enable me to specifically look at Canberra's situation.

Thursday, January 28, 2010

More on uncertainty in science

There is a great new article here: regarding uncertainties in climate science.

What is important to take away from this is that much of the uncertainty is on the bad side - in other words, it is more likely than not that our current knowledge of the science underestimates the negative effects of climate change.

As an example, the article talks about precipitation. In the 2007 IPCC report, there are some attempts at estimating the effects of climate change on precipitation in Australia. The table is at: What is says is that rainfall in south and west Australia is predicted to decline by between 0 and 15 per cent by 2020.

Unfortunately, as the Nature article suggests for other regions, the rainfall predictions are already proving somewhat optimistic.

First, it should be pointed out that we obviously only have three years of data to examine since the IPCC report came out - 2007, 2008 and 2009 - and the statistical value of three years is very small indeed. However, the results may be preliminary indicators that the IPCC has been optimistic.

In the south-east of Australia, the rainfall for the last three years was 12 per cent lower than the average for all the years preceeding 2007. Further, it remains on a trend line indicating that rainfall is declining at the rate of 1.5 per cent of the long-term average per year. By 2020, this predicts that rainfall in south-eastern Australia will be 27 per cent below the long-term average, and 15 per cent lower than the long-term average than it is today. So, even if the IPCC figure is measured as a percentage decline from today, the evidence is that the very top of the range for the south of Australia is likely to be hit or exceeded.

Monday, January 25, 2010

Problems with IPCC science

There have been a couple of issues raised regarding the science behind the IPCC reports raised recently, one a clear - and bad - error and the other a misreading of what the IPCC report actually said.

The error on glaciers was the statement in one section of the IPCC report that the Himalayan glaciers would be gone by 2035 at current rate of melting. This is not a claim supported by the evidence. While Himalayan glaciers are melting rapidly, these glaciers are huge. There is no known physical mechanism related to atmospheric temperature that could melt them all by 2035.

This was a bad error, and one that should have been caught earlier. However, it was caught - that it was the scientific process is all about, so it is not bad science that a mistake was made and then corrected.

It is bad politics, unfortunately. This is why politicians rarely admit an error even when they have made a blatant one. They understand that the public is not very forgiving of mistakes. And it is even less forgiving of mistakes by scientists. There is obviously a need for better checking of the material that goes into IPCC reports. Hopefully, the next one will not contain any errors approaching this magnitude. But in the meantime, we will have to deal with increasingly strident calls by those who disbelief AGW theory for the IPCC to be disbanded or some such. And the public may well listen now that an error has been admitted to. It makes our efforts more difficult, which is a sad thing. (Admitting the error is not a sad thing; it making things more difficult is sad.)

The other issue is the one to do with claims regarding increases in damage caused by extreme weather events as the world warms. There are accusations that the IPCC used one paper that made a claim that there was evidence that damage had increased over the past 30 years and that it was linked with global warming. However, while the IPCC did use this paper, it also looked at others that did not show an increase. The IPCC was balanced in its call for more examination of this issue. It put the view that there were risks associated with this, but that there was not enough evidence to quantify them.

Friday, January 22, 2010

Science, certainty and margins of error

One of the big problems that scientists have in explaining how the climate is changing and is going to change in the future is that science is not about certainty but people demand at least the illusion of certainty before making a decision. In the previous post, I discussed the trend in rainfall in Canberra, Australia and how that related to temperature increase. I made the prediction that Canberra will be a technical desert by 2048. However, the 95 per cent confidence interval for this prediction is something like 2025 to 2170, with the other five per cent spread out either side of those numbers. This means that there is a 97.5 per cent chance that Canberra will become a desert by 2170.

If I explained to you that there was a 97.5 per cent chance that Canberra would become a desert by 2170, what would your likely response be? I think it would be something like: 'The year 2170 is a long way off. There is not much point taking action at the moment - a lot will change over that time.' And that could be considered a reasonable response.

But what if I told you that because of the distribution of the data, the chance that Canberra will be a desert before 2050 is around 55 per cent? That would make it a bit more urgent. Further, what if I told you that the whole 'desert' thing is simply an arbitrary point of interest and that prior to becoming a desert Canberra will necessarily experience a decline in rainfall? In other words, we will not be going along fine until 2050 and then suddenly become a desert: we will feel the effects of climate change long before then - and in fact we are feeling the effects now. If we were not feeling the effects now - the decline in rainfall marching in lockstep with the rise in temperature - then there would be no data to extrapolate from.

My point is that some ways of talking about data are not effective at convicing people that action needs to be taken, while other ways of talking about the same data are effective. What I would like scientists in general to do is to explain what they mean when they talk about margin of error when discussing things with politicians and the general public. It is difficult: science is not about certainty. But if we want to manage the risks of climate change, then we are going to have to make critical decisions before we reach certainty of outcome. Humans do this all the time. We just need to convince large numbers of them to move in the same direction on this one.

Thursday, January 21, 2010

The future of rainfall in Canberra, Australia

The above graph should make anyone living in south-eastern Australia, and particularly those who live in Canberra, very alarmed.

What the graph is saying is that for every full degree rise in the 10-year average day time temperature there is a fall in the 10-year average rainfall of 78.8 mm.

At current rates of day time temperature increase in Canberra, which for the last 18 10-year periods have been rising at .087 degrees per year, this means that in 39 years - by the end of 2048 - the 10-year average rainfall in Canberra will be less than 250 mm, which would make Canberra a technical desert.

The period examined is from when records begin, which is 1940, until 2009. The correlation is quite good: an R^2 value of 0.6448.

At present, we are struggling for water, with the current 10-year value more than 100 mm below the average of the whole period. Imagine how bad things will be with rainfall less than half its present value ...

Update: I have just done an error analysis on the slope, including corrects for autocorrelation, and the error is quite large, with two standard deviations giving us a range of -22 mm/degree celsius to -134 mm/degree celsius. Note that there is also error in the slope for temperature. What this means is that a desert could still be a fair way off for Canberra - we might not be a technical desert until around 2170. But it also means that it is equally likely to arrive much more rapidly - we might be a desert by 2035. (note that a reduction in the value of the slope, because it is bounded by zero, increases the range in years much more than an equal increase in value in the slope).

Wednesday, January 20, 2010

The progressive paradox

I have just been watching the disappointing result in Massachusetts, where Scott Brown has just won the special senate election. It looks like a big blow against health care and against action on climate change, at least in the short term.

What I want to rant about here is my belief that it is in general progressives who have damaged the Democrat cause and the cause of left-wing progress more than the Tea Party or Beck or Hannity or anyone from the right.

The issue is one of the left always making the perfect the enemy of the good while ignoring political reality, which is the perfect will never pass a Senate that, while dominated in theory by Democrats, is in reality a conservative body with many members from fairly conservative districts.

Progressives love to talk about Obama failing to provide leadership on issues that are key to them, such as health care, climate change and the war in Afghanistan. It seems as if they believe that Obama can somehow force conservatives who feel a bit nervous about their re-election chances to suddenly change their positions and vote for a progressive agenda. It is a fantasy.

But when Obama fails to live up to the fantasy, he gets the blame. And thus the assault on Obama is from the right (which it always was going to be) and from the left.

Further, when Obama does make modest steps towards progressive goals, he is condemned for the deals he has to make in order to make those modest steps - it is almost as if the left think that Obama is betraying them by succeeding. The reason for this seems to be is that what they want is for him to try to things that are guaranteed to fail.

While over the long-term the progressive agenda is moving forward, in the short-term it seems as though progressives are determined to sabotage anything that is less than what they hoped for. And in the process they seem to want the Republicans to regain power, and are doing almost everything in their power to make that happen.

But I guess they can feel good about themselves: after all, they didn't sell out their principles. I hope that that keeps them warm at night - or, rather, cool when temperatures soar because they were not prepared to make some concessions.

Tuesday, January 19, 2010

Climate sensitivity, part 4

To quantify the reduction in forcings caused by effects other than greenhouse gases, we can take a ratio of these forcings to the forcings caused by greenhouse gases. If we exclude extremely negative forcing ratios, which mainly occur at the start of the period when variability was high, we end up with an average that is around -0.6. This means that forcings for greenhouse gases have been effectively reduced by an average of around 60 per cent.

Does this mean that my initial estimate of climate sensitivity of 2 plus or minus 1 degree celsius needs to be increased? Perhaps. It first needs to be recognised that the well-mixed greenhouse gases include more than just CO2. CO2 makes up around 60 per cent of the forcings here. So, if we take our initial number 2 degrees and mulitply it by 2.5 (we need to do this because only 40 per cent of the forcings from greenhouse gases is not countered by other negative forcings) that becomes 5 degrees. If we then take 60 per cent of that, we get a climate sensitivity of 3 degrees.

That for me is scary. If the observed non-equilibrium climate sensitivity is that high, then the equlibrium sensitivity must be at towards the high end of the IPCC range.

However, it must be recognised that there is a significant range in the observed sensitivity here - it ranges from 1.5 to 4.5, like the IPCC figure, and there may be a larger error margin in there simply because of the deviation in the reduction in forcings over time. By this I mean that while the average is 0.6, it ranges from around 0.3 to around 0.9.

Now, I am new at this so there may be some fundamental mistake I am making here in increasing the value. Any help would be appreciated.

Monday, January 18, 2010

Climate sensitivity, part 3

In this post, I will continue my examination of climate sensitivity using the forcing estimates published here:

In the previous post, I published a graph of total forcings versus temperature. These forcings are from multiple sources: carbon dioxide, methane, nitrous oxides, ozone, stratospheric H2O, the sun, land use, snow albedo (reflectivity), stratopspheric aerosols, black carbon, reflective aerosols and what are called 'aerosol indirect effects', which are mainly implications to do with how aerosols affect cloud formation.

It should be noted that the first three of those - carbon dioxide, methane and the nitrous oxides - are included in the GISS data as one entity called 'well-mixed greenhouse gases'.

When we examine the relationships between temperature and forcings for individual components, we find that there is only one that tracks closely the rate of temperature increases for total forcings, and that is the well-mixed greenhouse gases component.
If we combine all other forcings - the first graph above - we can see that over time these forcings have trended negative - and especially in recent times.

If we look at well-mixed greenhouse gases alone, we can see that the slope of this line is 24.137, indicating that for every full point increase in forcings from well-mixed gases the temperature increase .24137 degrees celsius.
What this indicates is that the climate sensitivity for well-mixed greenhouse gases is likely higher than the temperature increases indicate, as these increases have been suppressed by the other sources of forcing changes.

Climate sensitivity, part 2

In a previous post,, I showed a graph of the natural logarithm of atmospheric CO2 concentrations versus yearly temperature. This was in an attempt to work out the sensitivity of the climate to increases in atmospheric CO2. I came up with a figure of 2 degrees celsius per doubling of CO2 concentrations.

The question is: is this a good way of determining climate sensitivity?

The first issue is that there are many things that affect global temperature: the solar cycle, ENSO variations, atmospheric aerosols, ozone, orbital variations, other cycles et cetera. So maybe the variation that we see in temperature over time can be explained by things other than CO2, and thus a linear graph of CO2 v temperature is not a good way of working out the climate sensitivity.

However, in response to this point one of the benefits of doing this graph over a relatively long period - 130 years - is that many of these variations will have been included. There will have been about a dozen or so solar cycles over that time. ENSO will have gone from El Nino to La Nina on numerous occassions. Atmospheric aerosols will have risen and fallen in concentration, along with ozone. Cycles of length shorter than 130 years will have had all their various stages included.

The argument here is that all of these things will have averaged out over the 130 year period and that the only thing not taken into account will have been increases in CO2 concentrations. Thus, the climate sensitivity derived will be a reasonable estimate.

We can test this assumption by examining changes in forcings over this period. Carrick posted a link in the previous thread to data on forcings over this period. It is here:

What do I mean by 'forcings'? A forcing is the energy received by the earth from some particular source. They are measured in watts per square metre. As an example, the forcing from CO2 and other greenhouse gases in 2003 was 2.7487 watts per square metre. Totalled over the entire surface of the earth, this is a fair bit of energy.

Using the data, we can create a graph of total forcings versus temperature. This is what I have done above.

The graph has a slope of 21.682. This means that for every full point of increase in forcings, the earth increases in temperature by .21682 degrees celsisus.

I will examine what this means for my estimate of climate sensitivity to changes in CO2 in my next post.

Wednesday, January 13, 2010

The standard deviation of the slope

In a previous post,, I calculated the observed climate sensitivity of the earth over the past 130 years.

In this post, I will provide an estimate of the 95 per cent confidence interval for that climate sensitivity.

The data is autocorrelated. This means that I cannot use the normal method for calculating the standard deviation of a slope, which is given here:

What I need to do is make an estimate of the autoregression coefficient and then use this to substitute a new effective N into the standard deviation equation.

The effective N will equal N*(1-ARC)/(1+ARC), with ARC being the autoregression coefficient.

I examined the autocorrelation of the data and found the ARC to be .882. However, I do not think that it justifies that level of accuracy, as it might even be as high as .95, although that is unlikely.

An ARC of .882 yielded a 95 per cent confidence interval for the observed climate sensitivity over the past 130 years of 2.02 +/- .76 in degrees celsius. If it is as high as .95, then the 95 per cent confidence interval would be 2.02 +/- 1.64 in degrees celsius. This is a big range.


I have now re-examined the ARC and determined a 95 per cent confidence interval for it. This interval is from .84 to .99, with a middle value of close to .92. This middle value gives a range for the observed climate sensitivity of two plus or minus one degrees celsius.

Tuesday, January 12, 2010

Climate sensitivity

This is a graph of the natural logarithm of observed atmospheric carbon dioxide concentrations versus observed global annual temperatures since 1880, with the temperatures taken from GISS. Natural logarithm is used because the relationship of CO2 to temperature is not linear but logarithmic.

Using this graph, we can take a shot at working out what the climate sensitivity of the earth is.

First, what is climate sensitivity? Climate sensitivity in this case is basically how sensitive the climate is to changes in atmospheric concentrations of carbon dioxide. The standard way of describing it is how much the temperature will rise for a doubling of CO2.

The climate sensitivity usually suggested is 3 degrees plus or minus 1.5 degrees (centigrade). These numbers are the ones put forward by the IPCC.

The IPCC figure is for climate sensitivity at equilibrium - in other words, they are saying that the climate will have increased in temperature by somewhere between 1.5 and 4.5 degrees per doubling of CO2 once the earth settles into a stable state. This would presumably have to be some time after humans have ceased unsustainably pumping CO2 into the atmosphere.

The climate sensitivity that I will be examining here is the climate sensitivity when the earth is not yet at equilibrium. To do this, we need to look at the slope of the above graph.

The slope is 288. Given that GISS publishes its figures in 100ths of degrees celsius, we need to divide by 100. This gives us a figure of 2.88 degrees celsius.

However, this is an increase of 2.88 degrees per full point of increase in the natural logarithm of CO2. To determine the increase per doubling of CO2, we need to multiply the slope by .7. This is because the natural logarithm of 2 is .7.

The result is 2.01 - we may as well round to 2.

So, the observed non-equilibirum temperature sensitivity from 1880 to 2009 was 2 degrees per doubling.

I will post in a little while on whether or not this is a good way of calculating temperature sensitivity.