Friday, June 05, 2009

Analysis of Australian Temperature - Part 4 - Summer/Winter Effect

If CO2 was the major cause of global warming, then we should see a constant increase of temperature in summer as in winter. The blanket of Co2 should increase the temperature constantly over the year. Likewise it should increase the temperature constantly over the day and night, however I have showed previously that this does not happen.

So are summer and winter temperatures in Australia in increasing at around the same rate? Even according to the Australian Bureau of Meteorology this isn't quite happening. Summer temperatures are increasingly, well, slightly as shown here, whilst winter temperatures are increasing at a rapid rate as shown here.

One could argue here that this occurs mainly because of the different tropical climates that Australia has, and indeed this may well be the case. As northern Australia's summer temperatures do not increase at all, whilst their winter does. And conversely, southern Australia's summer and winter temperatures seem to be increasing. I'm not 100% sure why the tropics summer tends not to increase in temperature. It might be a threshold (its damn hot up there already in summer), or it might be something to do with the humidity. I'm also not sure why the BOM only have a trend going back to 1950 on these graphs, when there clearly is more data available.

In fact, the more data that they could use is that of shown below which compares the summer and winter temperatures based on the standard times of midnight, 3am, 6am, 9am, noon, 3pm, 6pm and 9pm. We have showed previously how the minimum temperature is not a good indication of long term trends at night, so the analysis to come should be interesting.

If CO2 were the major cause of global warming, then we should see a relatively constant increase in temperature in summer when compared to winter across all the times given above. Lets see if we do:

So what do we find? We find that there is no difference between summer and winter trends at night (namely Midnight, 3am and 6am). This is no surprise as we previously found that overnight temperatures have hardly increased over the past 60 years. However something happens at 9am which is quite drastic. All of a sudden summer temperatures at 9am are decreasing at such a rate when compared to winter temperatures.

What does this mean? It means basically that at 9am winter temperatures are increasing quite drastically when compared to summer. This trend is not small either, it is at a rate of 3.1 degrees per 100 years, more than 3 times the world average. Similar trends, but decreasing in nature occur at Noon and 3pm, where as at 6pm and 9pm the trend is reversed.

Interestingly, at 6pm and 9pm the sun will generally still be in the sky and have an influence in summer in Australia, but not in winter. Perhaps this is the reason why summer temperatures are increasing at a greater rate than winter temperatures at this time?

Either way, the trends are extremely strong and disturbing. If CO2 were the major cause of global warming, then we should see a constant trend throughout the day, and when comparing summer and winter trends throughout the day. We see none of this, but rather the opposite.

Perhaps Australia's Cloud Cover levels could be a major contributor to the increasing temperatures that Australia is recording? We shall look at this in the next post.