Comments on: Statisticians Cool Down the Climate Controversy http://www.scienceline.org/2009/10/28/blog_peeples_global-cooling-controvers/ The Shortest Distance Between You and Science Fri, 19 Mar 2010 03:48:50 -0400 http://wordpress.org/?v=2.8.4 hourly 1 By: R. Jackson http://www.scienceline.org/2009/10/28/blog_peeples_global-cooling-controvers/comment-page-1/#comment-4445 R. Jackson Wed, 03 Feb 2010 07:16:34 +0000 http://www.scienceline.org/?p=3360#comment-4445 re: #1: This article actually addresses your criticism very directly. Yes, it is true that displaying a 10 year moving average is somewhat subjective. The point, however, is that a multi-year averaging is exactly what is needed to detect trends in climate, which by definition express themselves over multiple years. A 4 year moving average plotted for this data would still show the same long term trend. The difference would be that the blue line would be less smooth and tip down more at the right side of the chart. The overall trend would remain. Looking at the annual mean data there are plenty of segments where someone could say "look at the downward trend here" (for example, the 1940s data). The issue, metaphorically speaking, is whether such trends from peaks to troughs are reflective of the actual landscape or the anthills along the way. It is not a deception to state upfront that a moving average was chosen based on known variabilities and then analyze the data with the averaged data. Why would you choose to define a climate trend based exclusively on four years of data, given what is known about inter-annual variations in weather (such as El Nino/La Nina patterns), while ignoring 120 previous years of data? re: #1: This article actually addresses your criticism very directly. Yes, it is true that displaying a 10 year moving average is somewhat subjective. The point, however, is that a multi-year averaging is exactly what is needed to detect trends in climate, which by definition express themselves over multiple years.

A 4 year moving average plotted for this data would still show the same long term trend. The difference would be that the blue line would be less smooth and tip down more at the right side of the chart. The overall trend would remain. Looking at the annual mean data there are plenty of segments where someone could say “look at the downward trend here” (for example, the 1940s data). The issue, metaphorically speaking, is whether such trends from peaks to troughs are reflective of the actual landscape or the anthills along the way. It is not a deception to state upfront that a moving average was chosen based on known variabilities and then analyze the data with the averaged data. Why would you choose to define a climate trend based exclusively on four years of data, given what is known about inter-annual variations in weather (such as El Nino/La Nina patterns), while ignoring 120 previous years of data?

]]> By: C. Bruce Richardson Jr. http://www.scienceline.org/2009/10/28/blog_peeples_global-cooling-controvers/comment-page-1/#comment-4046 C. Bruce Richardson Jr. Wed, 11 Nov 2009 03:52:28 +0000 http://www.scienceline.org/?p=3360#comment-4046 Folks can download that data and plot it using Excel. That's what I do because the climate issue is so politicized that there is often fudging. Take a look at the chart above. The blue plot is a moving average. Under that are red bars representing the separate years. Notice that each of the last four years is cooler that the year before it. That is a short term cooling trend. What it means is subject to debate. The fact that it is there, is not. Now look that the blue line. It isn't reflecting that cooling trend because the averaging span is longer than the trend. That is deceptive. And I believe that it is intended to be deceptive. The AP article is fudging in a very similar way. That's clever I suppose but should deception be a part of science? Folks can download that data and plot it using Excel. That’s what I do because the climate issue is so politicized that there is often fudging. Take a look at the chart above. The blue plot is a moving average. Under that are red bars representing the separate years. Notice that each of the last four years is cooler that the year before it. That is a short term cooling trend. What it means is subject to debate. The fact that it is there, is not. Now look that the blue line. It isn’t reflecting that cooling trend because the averaging span is longer than the trend. That is deceptive. And I believe that it is intended to be deceptive. The AP article is fudging in a very similar way. That’s clever I suppose but should deception be a part of science?

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