Posts Tagged ‘ Climate Change ’

Additive modelling and the HadCRUT3v global mean temperature series

June 12, 2011
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Additive modelling and the HadCRUT3v global mean temperature series

Earlier, I looked at the HadCRUT3vgl data set using generalized least squares to investigate whether the trend in temperature since 1995 was statistically significant. Here I want to follow-up one of the points from the earlier posting; namely using a … Continue reading →

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Global warming since 1995 ‘now significant’

June 11, 2011
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Global warming since 1995 ‘now significant’

Yesterday (June 11, 2011) the BBC reported on comments by Prof. Phil Jones, of the Climatic Research Unit (CRU), University of East Anglia (UEA), that the warming experienced by the planet since 1995 was statistically significant. That the trend in … Continue reading →

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Parametric Bootstrap Power Analysis of GISS Temp Data

October 24, 2010
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Parametric Bootstrap Power Analysis of GISS Temp Data

Previosly, I calculated a bunch of ad-hoc power curves from GISTEMP data. Power is essentially a reframing of the p-value, to see the significance of the trend lines in the global temps. However, power calculations are inherently very noisy, hence, my ad-hoc way of aggregating the data. Another method is to bootstrap through the responses

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Global Temperature Proxy Reconstructions ~ now with CO2 forcing

August 26, 2010
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Global Temperature Proxy Reconstructions ~ now with CO2 forcing

Previously, I did a simple Bayesian projection of recent temperature using proxy data and the methods shown in McShane and Wyner (2010). I showed that when you take out the last 30 years of data (1969~1998), the projection does not track the recent uptick in temperatures well. The “projection” is a simple unparametric bootstrap which

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Cherry Picking to Generalize ~ retrospective meta-power analysis using Cohen’s f^2 of NASA temp + visualization

July 17, 2010
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Cherry Picking to Generalize ~ retrospective meta-power analysis using Cohen’s f^2 of NASA temp + visualization

Previously, I plotted a grid of NASA GISS global temps in ggplot2 to show general trends by the brute force method. Here, I will again use the brute force method to do a simple power analysis on a portion of the data (data here). The general aim is to figure out what the minimum sample

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Area Plots with Intensity Coloring ~ el nino SST anomalies w/ ggplot2

July 10, 2010
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Area Plots with Intensity Coloring ~ el nino SST anomalies w/ ggplot2

I see many economy indicator graphs that show emphasis by shading in the curve under the area (while x-axis is time). The shade is stronger at higher values (example). I did this in R below (ggplot2). This was a little more difficult that I’d expected. The color gradients are good to color each individual points

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Cherry Picking to Generalize ~ NASA Global Temperature Trends ~ enhanced w/ ggplot2

April 12, 2010
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Cherry Picking to Generalize ~ NASA Global Temperature Trends ~ enhanced w/ ggplot2

In a prior article, I tried to visualize the linear global temperatures trends for a grid of start and end years. The visual I created was confusing in that the specification of color scale was interdependent with the data values. I wanted a blue -> white -> red scale of the temperatures indicating cool ->

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Cherry Picking to Generalize ~ NASA Global Temperature Trends

April 6, 2010
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Cherry Picking to Generalize ~ NASA Global Temperature Trends

The relatively (to this decade) cool 2008 global temperatures spurred talks of a warming pause, or even global cooling. The claim usually comes from people who cherry picked either data sets and(!)/or start and end points of the global temperature trends to back up their allegation. The blogosphere already has a lot on this: Skeptical

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Le Monde rank test

April 4, 2010
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Le Monde rank test

In the puzzle found in Le Monde of this weekend, the mathematical object behind the silly story is defined as a pseudo-Spearman rank correlation test statistic, where the difference between the ranks of the paired random variables and is in absolute value instead of being squared as in the Spearman rank test statistic. I don’t

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