Tracking Long Term and Recent UAH Channel 5 Anomally Trends

In this post I present  combined long term and recent trend charts of UAH Channel 5 temperature anomalies using R’s figure inside figure capability.  This approach provides a better picture of global temperature trends than UAH’s day-of-year plots.

Introduction

The University of Alabama Huntsville (UAH) provides a daily update to their Channel 5 global average temperature at 14,000 feet. I have previously posted about this data set here. The source data file link is here.

Here’s a snap-shot of the default UAH Channel 5 plot for May 9, 2010, showing the day of year values for 2010, 2009 and the 20-year baseline period average.

Figure 1: UAH Channel 5 Default Plot (5/9/2010)

This chart highlights the last reading for the current year with the small box. Users can check the option boxes below the plot to display other years and/or add the minimum and maximum values.

Many climate observers use this charting tool to assess global temperature trends because it is updated daily  with only a 2 day lag and provides complete global coverage from satellite imagery.

The default chart does not provide information on long term trends over the full data series period (1998-2010). To try and see the long term trends, some users check several/ all of the individual year options to show individual years from 1998 to 2010, as shown in Figure 2.

Figure 2: All Years and Minimum, Average and Maximum for 20 year baseline period

Figure 2 looks more like a bowl of colored spaghetti than a statistical chart.  It’s impossible to see the long term trend and it is hard to see more than the fact that the latest daily values are higher than the previous daily 20 year baseline period maximums. Is there a better way to plot this data so that we can clearly see both the long term and recent trends?

Figure Inside Figure Approach

Here’s my R script based plot of the UAH’s daily channel 5 chart (Click to enlarge).

Figure 3: R Script Based Chart - Long Term and Current Month Trends

I made several changes in my version:

1. I use R’s figure inside figure capability to make 2 plots: a) long term trend and b) current month trend
2. I use anomalies rather than temperatures
3. I show historic monthly mean anomalies for entire data series period
4. I show daily values for current month in Figure b
5. I highlight and display value for latest reading on both long term and recent trend charts
6. I show daily maximum values for current month
7. I show month-to-date (MTD) average  for current month
8. I show historic maximum for current month

I will add this chart to my Climate Images series and plan to update it on a weekly basis so that readers can see how the current month stacks up with the UAH Ch5 long term trends,

The RClimate script for downloading and plotting the UAH channel 5 data is available at this link.

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