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Friday, January 8, 2010

Fielding's Folly Part 2

In a previous post I discussed the following graph from Senator Stephen Fielding:

In that previous post I used graphs geneated by D. Kelly O'Day at this site.

In this post I will generate the graphs using the WoodForTrees site. This site provides a range of powerful tools for creating climate charts. I will include links to the charts at WoodForTrees. To the right of the charts are a series of drop down boxes that can be used to generate the charts. To any reader who is not familiar with the WoodForTrees site I recommend investigation of the drop downs to determine how I generated the charts.

The first graph is the temperature time series from 1995 to the present. I am using the UAH data, a measure of the tempeature of the lower part of the atmosphere. The reason for my choice of UAHis that it is the favourite of the climate change deniers, because it shows less warming than the surface temperature measurements. Any denier who happens across this post can't accuse me of cherry picking the termparature data. The graph can be found on the WoodForTrees site at this location.

There are a number of interesting issues to note with this graph. The temperature values vary from -0.2 to almost +0.8. These are not the actual temperatures, they are anomalies, that is the average temperatures for each similar month (all Januaries, all Februaries, etc) subtraced from the average monthly value. The average monthly temperatures are determined from a baseline period. For the UAH series the baseline is from Jan 1979 - Dec 1998. Anomalies are explained very well at the WoodForTrees site at this page.

The team at UAH use satelite measurements to construct their temperature series. The other group to use satelites is RSS. For details on the use of satelites to measure temperature see this article. There are three surface measurement groups: Hadley, GISS and NCDC.

Note that the temperature graph (red line) has a great deal of variability. Of particular interest is 1998, which stands out as a huge "tower" in the centre of the graph. The large increase in termperature for that year was caused by a very powerful El Niño. A significant decline in tempeature occurred in 2008, which was caused by a La Niña (see previous link).

It is not always easy to see a trend in data just by "eyeballing" it. Statisticians have developed methods of determining trends in data. One of them is regression. The green line shows the best fit regression trend line for the period of the chart. It is clear that the trend is positive.

The graph below shows the CO2 change over the period 1995 - 2009. The actual graph can be found here.

Note that there is a regular annual cycle, but that the amount of CO2 is increasing at a very regular rate. This consistent increase is clear without refering to the green trend line.

The scale on the left is in parts per million (ppm) and ranges from 360 to 387.

The chart below combines the two previous ones. It solves the problem with Fielding's two axis graph discussed in the previous post. There is only one scale on this chart, with the data adjusted to fit. This technique, which is available in WoodForTrees, is called normalization.

The chart is somewhat cluttered but the conclusion is clear: both the temperature and CO2 trends have been rising. The chart can be seen at this location.

The chart below is clearer as it just contains the trend information. It can be found here.

CO2 is increasing more quickly than temperature, but this is not a surprise. Climate science does not claim that CO2 is the only factor in play here. It is not even the only anthroprogenic (human caused) effect. As well as CO2 humanity is adding pollution to the atmosphere that is counteracting the greenhouse warming. The main pollutant is sulfur dioxide, which reflects some of the sun't energy out of the Earth system. Climate scientists call the sulfur dioxide particles aerosols. Here is an article on aerosol cooling.

It is clear that Fielding's claim that "global temperatures have remained steady over the last 10-15 years despite skyrocketing man made carbon emissions", is not true.

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