Nathan Scandella (personal)

Climate Change Mythbusting (Part III)

Another popular skeptical argument, concerning climate change, is that not only is global warming not happening, but we're now in a period of global cooling. This is patently false.

First of all, complicating the matter for people who aren't used to analyzing statistical data, is the fact that short term fluctuations in temperature are actually of much greater magnitude than long term fluctuations, such as our current warming trend. It's impossible to justify, or refute, climate trends by saying, "well, this year doesn't seem any warmer than the last couple years". That's just a nonsense approach, and anyone with a math background knows it.

In order to detect long term trends in noisy data sets, you have to use moving averages, or filtering, to smooth out the high-frequency fluctuations. In the case of climate trends, that means smoothing out the short-term trends due to weather variations, and changes in total solar irradiance. When you do that, you find that we are still in a warming trend. A recent independent analysis by statisticians, who were not told that the data was global temperature data, confirmed that there is no recent cooling trend to speak of, and that the earth is still warming, on average.

One popular tactic of skeptics is to quote temperature changes since 1998. They pick 1998, because it was a record hot year. So, with 1998 setting the bar so high, the years immediately following it are likely to look a little cooler to the untrained eye, simply because every year is not going to break a new record. If LeBron James scores 30, 32, 36, 39, 51, and 42 points, would you claim that the last game shows that his scoring output is dropping? That would be fairly ridiculous. That's exactly what skeptics are doing when they claim cooling based on an arbitrary period, that begins in 1998. In fact, just as 1998 was significantly above trend, the next year was significantly below trend (cooler). If you simply average the two years out, you see that there's nothing particularly out of line with the gradual warming trend. Thus, one could arbitrarily pick 1999 as a start year, and point to a greater warming trend, compared to a start date of 1998. That's why we don't talk about climate change in the context of a few years. If this trend weren't observable over a period of multiple decades, which encompasses multiple (11-year) solar cycles, then I would agree that the data is inconclusive. But, the trends do persist over multiple decades.

Another cheap math trick used by skeptics is to focus on the last few years, such as this decade alone. However, aside from the fact that temperature data is noisy, and you always need to look at long-term trends, and filtered data, there's another factor. Our current solar cycle peaked in intensity in 2001, and has been lower-intensity ever since then. We're now only slightly up from the low point in solar irradiance. So, if you take a sample of data from 1998, or 2001, until 2009, you will be sampling a period over which the sun's intensity has mostly been waning. Unfortunately, we know that the next few years will not afford us that same luxury, as solar irradiance will once again be rising. But for skeptics, the solar trend may just buy them another few years to keep stalling efforts to take real action to prevent catastrophic climate change.

http://upload.wikimedia.org/wikipedia/commons/thumb/7/7b/Temp-sunspot-co2.svg/720px-Temp-sunspot-co2.svg.png
Note: sunspots correlate highly with solar irradiance, so sunspot measurements are often used as a proxy for the sun's intensity

Finally, I'd like to point out that in the article linked to above, it mentions the discrepancy between land and satellite based temperature measurements. As the article mentions, it's important to note that the satellite data program is managed by John Christy at the University of Alabama at Huntsville. I think it's relevant to mention that Christy, like many climate change skeptics, is a man of extreme faith. Not merely the kind of faith that sends one to church on Sundays because that's what the rest of the family does. This man was actually a missionary, and has a degree in divinity. Sorry, but if you embrace the evidence-free-zone of Christianity to the extent that you get a degree in it, and attempt to spread it to vulnerable third-world non-believers, then you're not in a position to be trusted with major scientific responsibilities. Why is it that religion is so prevalent in climate change skeptics, both scientists, and non-scientists alike? (Answer left as an exercise for the reader)

Edit: By the way, John Christy's primary colleague leading the Alabama-Huntsville satellite team is Roy Spencer. Spencer openly supports Intelligent Design. And as another of Alabama's enlightened sons, Forrest, Forrest Gump once said, "That's all I have to say about that".

Posted at 12:21AM Oct 27, 2009 by Nathan in Environment  |  Comments[0]