Tuesday, July 10, 2007

South East NSW

South East NSW through the weather stations of MORUYA HEADS PILOT STATION and POINT PERPENDICULAR LIGHTHOUSE COMPARISON doesn't have a lot of data at Midnight, 3am, 6am, Noon, 6pm and 9pm - each ranging back around 20 years, but 9am and 3pm records are good.

But firstly maximum temperatures recorded a significant increase in temperature (p < 0.01), with especially the last 10 years being well above the average. Minimum temperatures seem to be cyclic if anything, decreasing until about 1970 and increasing from then until now.

Temperatures at 9am showed no significant difference in temperature (albeit a slight though insignificant decrease), whilst temperatures at 3pm show a significant increase, which is understandable as the temperature range is only from the 1960s.

So what does this mean? It's getting hotter during the day, and outside this time is argueable. In fact taking the dfference between temperatures at 3am and 6am and the minimum temperature sees an increasing trend - especially of late.

This means that the minimum temperature is increasing at a rate much quicker than the temperatures at 3am and 6am. Thus indicating that the minimum temperature is not a good representation of overnight temperatures. Also the minimum temperature is increasing at a significant rate since 1957 as compared to 9am temperatures.

So it would be great if we were to stop analysing max and min temperatures as the ultimate measure of world wide temperature.

I still can't believe that scientists (obviously they aren't statisticians) believe that the formula

global temperature = (max + min) / 2

is a good formula for measuring average temperature. It's just plain ridiculous.

7 comments:

Philip said...

The trend in the minimum anomaly versus the 9am anomaly is striking. There must be a 1.5 degree difference over the last 50 years. Has someone been adjusting the minimum temperature and not the time based temperatures?

Jonathan Lowe said...

the difference between 9am and min is very strange and I dont believe occurs in many other places, I'll have to test it out. Might just be random error, but I doubt people are changing the min temperature to suit their needs - this type of data is generally automated nowadays

Carnival of Climate Change said...

You have been nominated for the Bloggers for Positive Global Change award:
http://www.carnivalofclimatechange.com/2007/07/bloggers-for-positive-global-change.html

Alan Woods said...

Jonathan, have your tried or are you going to calculate mean temperatures with the data you've got?
ie 12AM+3AM+6AM+9AM+12PM+3PM+6PM+9PM/ 8 (or some variation).
It would be interesting to see a time series for this vs BOM mean temp, even if it only for the last 20 years or so.

Jonathan Lowe said...

yes that would be interesting alan woods, however why make the variable a summary variable, when we can study what is happening at different times of the day instead?

Alan Woods said...

Well we (ie you) can do both. Sure it ain't perfect, but it might give a good visual exposition on why the min+max/2 measurement is inappropriate and that data is available to produce a more accurate average temp.

Philip_B said...

There is a general (universal) belief that increasing minimum temps mean increasing nighttime temps and less nighttime cooling.

Your analysis seems to disprove both. I.e. nighttime temperatures are not increasing (or are not increasing in line with min temps), and not only is nighttime cooling not decreasing, it must be increasing because the increased daytime warming is being lost at night.

The last finding is a blockbuster.

BTW, I agree with Alan that a time based average temperature (compared to a min/max based average) would be a worthwhile exercise.