Comparison of UAH and GISS Time Series with Common Baseline

In this post I set both UAH and GISS global temperature anomaly series to a common baseline period (1981-2010)  and compare them. Even though the UAH series is satellite based and GISS series is station based, the series exhibit striking similarities.

Common Baseline

In this previous post, I showed how to convert temperature anomaly time series from one baseline period to another period.  I use this technique in this post to directly compare UAH (baseline 1981-2010) and GISS (baseline 1951-1980) series.

The offsets are as follows:

• UAH:  -0.000978
• GISS: 0.34958

Since the UAH TLT 5.4 series is based on a 1981-2010 baseline, the offset is nearly zero (-0.00098 versus 0.0).

Users can reproduce my analysis on their own by downloading my CTS.csv file and applying the offsets to the UAH and GISS series.

Comparison of 1981-2010 Baseline Series

Here is a plot of UAH and GISS 12 month moving averages for 1979 to current: Click to EnlargeBoth 12-month moving average series show similar cyclical patterns with  positive trends. The UAH series shows a wider swing than GISS in both  high and low periods.

Here is the monthly trend chart for the 2 series: Click to Enlarge

The series seem to track each other quite well, with UAH tending to be higher in El Nino events and lower during La Nina events than GISS.

We can examine the delta (delta = UAH – GISS) between the two series to see the actual differences between the series each month. Click to Enlarge. In the 1979 – 2011 period, UAH has been greater than GISS 50% of the time and less than GISS 50% of the time.

Here is a scatter plot of the 2 series: Click to EnlargeResults

Once we set UAH and GISS series on the same baseline, the similarities between the 2 series become clear:

• Both series exhibit strong cyclical patterns, attributable in part to El Nino – La Nina cycles
• Both show upward trend
• Timing of cycles is comparable
• UAH is greater than GISS 50% of months
• GISS is greater than UAH 50% of months
• UAH seems to react more to El Nino – La Nina events than GISS

6 responses to “Comparison of UAH and GISS Time Series with Common Baseline”

Sorry, I could not find the R codes in this blog. Could you please share them. Thank you.

• Kelly

I did not include R script for the map. The post explains how to calcualte offsets. I proviced CSV file for both data sets if you want to generate similar charts.

2. Murray

Nice site. One suggestion for the GISS vs UAH comparisons -exaggerate the vertical scale, bring the curves up to the present and plot the trend lines. GISS starts very nearly 0.2 degrees cooler than UAH and ends very nearly 0.1 degrees warmer. I think you will find a very different trend, with GISS warming about 0.1 degrees C/decade quicker than UAH. AGW theory says that the lower troposphere should warm at a rate about 1.2x the surface rate, so if UAH is taken as correct, GISS warming is overstated by >0.12 degrees C/decade.

• Kelly

Murray

Can you elaborate on your points so that I can better respond? You say:

1. Bring curves up to present – They are updated through Feb, 2011! March data won’t be available for a few weeks.

2. GISS starts nearly 0.2 degrees cooler than UAH and ends up 0.1 degree warmer. – I don’t see where you got these observations from. The 12 month moving average chart doesn’t show this. Can you explain where thee points are?

3. AGW theory says that the lower troposphere should warm at a rate about 1.2x the surface rate – Please site a reference for this.

3. tony

I do not have the raw data in front of me but another possible conclusion is that the slope of the anomaly with respect to time is greater for GISS than for UAH. Each succeeding version of the GISS data lowers the earlier estimates of the anomaly and thereby increases the slope. You can note the consequence of this in your third graph where the preponderance of red is on the left side (the earlier years).