It’s that time of month again. The monthly temperature anomalies are soon to be publicized. I’d usually ignore them, but I’ve had this (simple) script hanging around for about a month now, so I thought I’d use it. With UAH releasing their August temperature datum, and temperatures plunging in 2008 it seemed like a good opportunity to look at what the monthly changes in temperature anomaly mean (or don’t mean).

What this post will attempt to do is show the effects of instrument noise on the global mean temperature anomaly time series. I’m going to assume that anyone reading this has seen at least one of the temperature anomaly time series. Pick your favorite - it doesn’t really matter which one. I chose the GISTemp anomaly from 1880.
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McIntyre notes something explained by MET101. In this case, why the northern hemisphere is warming faster than the southern hemisphere.

Commenters provide possible reasons - most of them wrong:

• This proves CO2 isn’t a well-mixed gas!
• The RSS values have more data in the northern hemisphere.
• I have an interest in paleoclimate.

Then McIntyre provides his own explaination:
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Talking about the concentration of CO2 in the atmosphere seems to be cool this week. [1], [2], [3] It was brought up at one of the sites that the increase we’ve since the beginning of the Mauna Loa record may not be anthropogenic. First, I’ll outline using simply cartoons why it has to be anthropogenic.

Consider the amount of carbon dioxide in the atmosphere prior to the industrial revolution. Assume that it is in a steady-state equilibrium, and that all sources and sinks are natural. Use a bathtub as an analogy. If I add 3 buckets of water to the tub per hour, then the amount of water in the tub will steadily increase. However, if suddenly a friend starts taking water out of the tub at the same rate I add it, the water will retain the same level.
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Red is hot, and blue is cold. Seemingly everyone knows this. Even though blue light has a higher energy, and thus temperature, than red light. Watts has a recent post about Color and Temperature: Perception is everything. He questions, “Is it just me or does there appear to be a warm bias in the color temperature presentation of the majority of providers shown here?”

I have previously posted a couple thoughts on the use of color when presenting figures to the public; for example Using Color Contours to Improve Public Interpretation of the Temperature Record and Using Color to Visualize Decreases in Sea Ice Extent. Color is not just a way to make a boring figure pretty. The color has to add information. For instance, in his Color is Everything post, Watts shows current (at time of posting) national temperature figures from several sources.
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