Proof that warming in Western Australia is all about the sun

I promised you some good analysis on Southern Pilbara (central-west Western Australia) yesterday when I analysed the temperatures and I keep to my promise so here it is:

Yesterday we came up with the very unusual result that despite the fact that there was no significant increases in temperature from 9pm to 6am in southern Pilbara - and not even any recogniseable patterns – we found that the area recorded a significant increase in minimum temperature. This is very surprising. We also found that in the area temperatures were significantly higher from 9am thru to 3pm when the sun is at it’s hottest.

At first look it’s quite clear that the reason southern Pilbara is heating up is solely due to the sun. The sun is just getting damned hotter. So why the increase in minimum temperatures, especially when there is no difference in temperatures throughout the night?

I decided to have a look at the differences in temperature anomalies for neighboring times over the years. In other words, I looked at the temperature anomalies for Midnight minus 9pm. As previously noted, 9pm doesn’t have a lot of data for Southern Pilbara so it is hard to find a pattern, and the statistics suggest no difference (t = 0.24, p = 0.81). In other words, Midnight has not been heating up at a quicker rate than 9pm over the years in Southern Pilbara.

The same goes for 3am minus Midnight, only this time we have a good amount of data. There is no pattern. Temperatuers at 3am have not been heating up quicker or slower than Midnight over the years (t = 1.4, p = 0.15).

But wow, look at this. When looking at 6am minus 3am, we find that temperatures have increased at a significantly higher rate at 6am than 3am (t = 5.3, p < 0.01). Keeping in mind that we did not find a significant increase in temperature at 6am, however we have found that the temperature increase at 6am is significantly greater than 3am. This has occurred with especial magnitude in the last 10 years as shown in the graph.

And a similar pattern occurs when looking at the 9am – 6am anomalies. A significant increase occurs (t = 6.04, p < 0.01). With temperatures increasing on average 0.5 degrees more in the past 10 years. If you look at the 6am and 9am graphs, this makes sence, as in the last 10 years 6am was about average temperature whilst 9am temperatures were about 0.5 degrees above the norm.

Surprisingly this is where the large boom stops. Analysis of Noon minus 9am temperatures suggest no increase or decrease in temperature (t = -0.6, p =0.55). A cyclic pattern can be seen, but this could be purely due to random variation.

And now for the even more surprising results. 3pm minus Noon saw a significant decrease in anomaly temperatures (t = -8.1, p < 0.01). The decrease is almost perfectly linear and is clearly obvious. So despite significant increase in temperature for south Pilbara for Noon and 3pm, 3pm isn’t heating up as much as it has been 3 hours before.

The obvious linear line in the graph of 6pm to 3pm is startling. So perfect is the line, that the amount of variability is very small. The decreasing trend is very significant (t = -10.8, p < 0.01).

There was no significant difference in temperatures when looking at the differences between the 9pm and 6pm anomalies, however a smaller database for temperatures at 9pm could have been a factor (t = 1.3, p = 0.18).

So what does all this mean? How is this all relevant. Well let’s summarise what we have just found. The rate of increase or decrease in temperatures with respect to the time 3 years prior makes little difference at night, but when the sun is a factor the difference is significant. Temperature anomalies at 6am and 9am have increased significantly with respect to the time 3 hours previous over the years, whilst temperatures at 3pm and 6pm have decreased significantly with respect to the time 3 hours previous.

But to understand fully what this means, we have to discuss very briefly how daily temperature works. Basically we reach a maximum temperature, and from that point on the temperature generally decreases. When the sun as set, there is no general reason why temperatures will be on the rise, so they decrease until the sun makes an appearance again. In southern Pilbara the sun rises in general half way between 6am and 9am depending on the season.

We suggested before that is was relatively obvious that the sun was a major factor in determining the average maximum temperature in Southern Pilbara, as we saw no increases in temperature over night. We have also proven that the sun has made significant increases in maximum temperature rather than minimum during years when Australia is heating up. So would a stronger sun therefore also have an influence on minimum temperatures? Our analysis suggests so.

Whilst no increases in temperature were found for Southern Pilbara from between 9pm and 6am when the sun was set, at 6am, the temperature increase as compared to 3am was highly significant. The sun, whilst not risen, quite possibly was warming up neighbouring areas more than normal, and adding heat to the air above at a greater rate than normal. Thus paving the way for when it makes its grand entrance at sunrise.

Hence, whilst not making a significant temperature difference at 6am before sunrise, it made a significant increase in temperature compared to 3 hours prior at a time where normally the minimum temperature would have been reached. This extra layer of heat paved the way for massive increases in temperature at 9am after the sun had risen. Following, due to the massive increases in temperature 9am, Noon and 3pm also had increasing temperatures due to the intensity of the sun, but not quite as dramatic as that when the sun rose. Hence we have a situation where we have a significant increase in temperature at 3pm but a highly significant decrease in temperature at 3pm with relation to Noon. I guess there’s only so much difference that the sun can make.

So what can we conclude about Southern Pilbara? That increases in the suns intensity has caused the area to heat up during the day, to stay at a constant temperature during the night, and most importantly, that increased intensity in the sun has not only caused increases in maximum temperatures but also increases in minimum temperatures.

Who would have thought that the sun has something to do with heat?