Thursday, April 16, 2009

Analysis of Australian Temperature - Part 3

For all new readers, please read Analysis of Australian Temperature - Part 1 and Part 2 first.

Previously we found that temperatures overnight in Australia are staying relatively steady over the years despite the minimum temperatures increasing. Temperature trends over time suddenly rose when the sun made an appearance, increasing at a greater rate until the middle of the day and then fading away. A case for the sun can be easily argued here.

This can be backed up even more when looking at time based differences over the years. Shown below are the differences in temperature trend over the years for two neighbouring times.

The above graphs show us a few things. Firstly that there is no difference in temperature trends over time at night from 9pm to 6am. Temperatures are steady over time. Then suddenly at 9am we see a sudden increase in temperature. Temperatures remain steady throughout the day (despite a seemingly seasonal trend?), but at 6pm the temperature drastically decreases when compared to 3pm. All this could have been deduced from the previous graphs.

But what happens if we look at the differences in trends from summer and winter?
I will look into this further and in a lot more detail in the next post.

Wednesday, April 08, 2009

Analysis of Australian Temperature - Part 2

For all new readers, please read Analysis of Australian Temperature - Part 1 first.

Part 2:

What is interesting in the analysis done in Part 1, might not have been that 44% of all warming in Australia is accounted for, simply by a better mathematical method of analysing the data, but rather the variations in the temperature throughout the day as shown below:

Why is it that we are seeing a significant warming trend between the hours of 9am and 3pm, and a smaller increase in other times? Surely, if CO2 were the principle mean of global warming, then we should see a constant increase amongst all times. This clearly is not the case in the analysis of Australian temperatures.

We can look even closer at Australian time based temperatures by comparing their anomalies over time as compared to the maximum and minimum temperatures. If global warming has been by and large been a result of an increase in CO2 emissions, then we should have a steady increase when compared to maximum and minimum temperatures over time. This is what we find below:

What we find in the above is something quite extraordinary. For 9am, noon, 3pm, 6pm and 9pm there is little trend. This indicates that temperatures at these times have increased at around the same rate as the minimum temperature. Readers will note however a large increase in the last 10 years of differences in temperature between 9am and the minimum.

However for midnight, 3am and 6am, we see a very strong decreasing relationship. This indicates that the minimum temperature has increased at a significant rate when compared to these temperatures. Some readers will say that this is understandable considering the analysis done in part 1, however it is highlighted here for significantly.

It seems, that the minimum temperature is more strongly related to the temperature in the middle of the day than at night. Too may times, people quote minimum temperature trends as having something to do with overnight temperatures, when we clearly show here, and the fact that the minimum rarely occurs at night, that this is not the case.

Put frankly, the minimum is a poor measure of overnight temperatures, and its trend has more to do with day temperatures than night. And what of maximum temperatures? An analysis of time vs maximum temperatures is shown below.

Whilst the above graphs show that maximum temperatures have increased at a greater rate over time when compared to midnight, 3am and 6am temperatures, this was expected. What was not expected is the strong negative relationship between maximum temperatures and time based temperatures during the day. In particular 3pm. Maximum temperatures are shown here to be increasing at a lot larger rate over time when compared to 3pm (and other day temperatures).

This is strange, as we would expect the maximum temperature to be reached between noon and 6pm depending on various aspects, especially the season. What this indicates therefore, is that during the day, Australia is heating up at a greater rate per hour, reaching a peak temperature and then falling in temperature at a greater rate per hour.

One could argue that Co2 could not be the cause of this. The carbon blanket should increase temperatures steadily throughout the night and day at a relatively constant rate. However, what we are seeing here is minimal increases at night, and then steady increase and then decreases during the day, the rate of change of this increase and decrease during the day increasing over time.

What could cause this? Well in Part 3, we will compare time based temperatures as well as look at temperature trends based on season (summer, winter).

Friday, April 03, 2009

Analysis of Australian Temperature - Part 1

Australian temperatures are on the increase, there is little doubt about that. Maximum and minimum temperatures have risen by about 0.7 degrees in the last 100 years. Our analysis will look not only at maximum and minimum temperatures, but also at time based temperatures, which we previously argued are a better more consistent representation for temperature analysis.

Using 21 weather stations around Australia that have accurate and consitant time based temperature data from 1950 onwards, we also found that the maximum and minimum temperatures have significantly increased in the last 50 years. This is shown below. Click on them for a larger graph.

You should note a couple of things. Firstly, the maximum temperature has increased since 1950 at a rate of 1.5 degrees which is larger than normal. This is for a couple of different reasons. One is that temperature has warmed up quicker in the last 50 years than the 50 before that, and secondly, because we have had to use some urban weather station in our analysis which is not normally used because of the heat island effect. Thus the increase is greater than normal.

But that shouldn't worry us or hinder any analysis that we undertake. Secondly you will notice that the minimum temperature has increased at a rate to what was expected or at a lower rate than the maximum temperature. It is still a significant increase, although there seems to be no major changes in the temperature since around 1972. Before this we saw mostly negative anomalies, and after positive.

Either way, both maximum and minimum temperature are shown to have increased significantly since 1950 as expected.

So what about time based temperature? Well as shown below we have 8 time based temperature since 1950 for Midnight, 3am, 6am, 9am, Noon, 3pm, 6pm and 9pm. It must be noted that for some reason the amount of data for 9pm is less than the other time variables.

There are many things that we can talk about with regards to the above graphs. Readers will first note that night time temperatures (Midnight, 3am, 6am) show little increase in temperature. In fact, they average just 0.43, 0.26 and 0.28 degree increase in temperature per 100 years. This is a lot lower than the expected, which clearly indicates that night time temperatures in Australia are only increasing a very small amount.

But how can this be when the minimum temperature is shown to be increasing a lot more? Well the answer is simple and surprising to many, in that, the minimum temperature more often than not occurs during the day. Basically, as soon as the sun sets, the temperature decreases over night. When the sun rises it starts to heat up the atmosphere, and only after 30 mins to an hour after sunrise to we fall to a minimum and the temperature starts to increase again for the day.

Hence, the minimum temperature has little to do with night time temperature and is a lot more influenced by the sun and cloud cover.

Readers will also note the sudden increase in temperature at 9am, noon and 3pm. Which then starts to fade a way a little from 6pm onwards. This is highlighted in the graph below:

So it is clear that temperatures in the middle of the day have increased at a greater rate than temperature outside this time. What would cause this? It is also clear that the maximum (which generally occurs around 3pm depending on the season), and also the minimum (which generally occurs around 6am to 9am depending on the season) are highly influenced by the increase in temperature in the middle of the day.

This graph alone strongly suggests that analysis of maximum and minimum temperatures solely is not an accurate way to measure temperature. A better method would be to take the average of each of the times to come up with an average temperature increase since 1950.

Currently, climate change analysis simply averages the maximum and minimum temperatures to come to a conclusion that the world has increased by 0.7-1.0 degrees over the past 100 years. With our data, this equates to 1.17 degree increase per 100 years. However if we average all of the time based temperatures, which no doubt, would be a more accurate way of measuring temperature over time, we find an average increase of only 0.66 degree per 100 years. This is shown below:

Hence we can conclude that 44% (1 - 0.66/1.17) of all increase in temperature in Australia since 1950 can be accounted for, simply by a better mathematical method of measuring temperature!


We've just reduced the amount of temperature increase that Australia has seen, simply by looking closer to the data and analysing it in more depth. But we are going to get a lot more in depth that this. And that will have to wait till part 2.

Thursday, April 02, 2009

Melbourne Stage 4 Restrictions

Melbourne should now be in stage 4 restrictions for water usage, which means that watering the garden and washing the car is not allowed at all.

The trigger point for stage 4 restrictions is 29.3 percent. This was hit on the 30th of March, and already 2 days later, Melbourne's water storage levels are now at 29.1 percent.

The Brumby government said that they will stay on stage 3a till at least November. Water minister, Tim Holding said that

``We are not using trigger points because we need to take into account not only the level of water in the storages but the amount of demand there is on those storages,''

Brumby Government water minister Tim Holding said the mixture of 3a restrictions and the Target 155 water saving campaign meant metropolitan users were already held to a high standard.

It seems to me, that the only reason why we are not on stage 4 restrictions is that if we go there, then it is clear that the Brumby government's "Target 155" scheme was a failure.

With the population increasing all the time in Melbourne, and no extra water storages becoming available, it is clear that the Target 155 scheme will always inevitably be a failure.