This post presents an R based chart of global GISS land and sea temperature anomaly data for the 1880-2009 period with both the long term trend and the individual decadal trends. Links to the source data file and the R script are provided so that readers can reproduce/ improve on this analysis.
Global Temperature Trends
I have a number of posts on global temperature trends (see my Climate Trends page for links). As I have studied climate change (see my ProcessTrends.com page for chronology of my learning curve) I have found that I needed to sharpen my trend analysis because climate trends are affected by annual, decadal and geologic time scale cycles as well as natural variation. El Nino and volcanoes, for example, play a major role in year to year variation in temperature trends (see my previous posts here, here and here).
In my George Will post, I showed why it is dangerous to over-interpret a short term, 10 year trend.
In this post, I show the decadal trends for the same data set I used in the George Will post.
GISS Anomaly Decadal Trend Rates
GISS provides an on-line file of monthly temperature anomalies since 1880 at this link. Here’s a sample of the file:
While this file is a great resource, it takes some work to develop an automatic way to update trend charts for do-it-yourselfers. Excel users need to use VBA.
As an aspiring R user, I needed help from LearningR to get the R script needed to automatically update the GISS monthly data. Thanks again to LearningR for the help.
Here’s my trend chart with decadal trend rates:
The R script for this automatic chart generation is doing quit a bit:
- Reading the raw GISS data file
- Extracting monthly data from 1880 to most current value
- Plotting overall data
- Calculating overall trend, plotting trend line and displaying rate
- Calculating decadal trend rates, displaying color coded trend lines for decade, and displaying color coded trend rate
Here’s a link to my R script.