Here is a review of the major global temperature metrics in tabular and graph form. There is a bit of disagreement this month. GISS still comes out the warmest, as it did last month, and the month before, and there is a bit of divergence between the RSS and UAH satelitte derived datasets.
I’m a little late to this game as I’ve been busy catching up on personal business since my trip to NCDC Asheville and 20 station survey across North Carolina, but I thought it was worth a review.
RSS (Remote Sensing Systems of Santa Rosa, CA) RSS Microwave Sounder Unit (MSU) global temperature anomaly data by For April 2008 has moved a tiny bit higher, with a value of .080°C for a change (∆T) of 0.001°C globally from March.
2008 1 -0.070
2008 2 -0.002
2008 3 0.079
2008 4 0.080
RAW RSS data is available here
Note that there does not appear to be any sustained upwards trend post 1998.
Here is the entire RSS MSU dataset plotted:
click for a larger image
Reference: RSS data here (RSS Data Version 3.1)
University of Alabama, Huntsville (UAH) published their data set for April 2008, and it is in slight disagreement with the RSS data, dropping with greater magnitude than RSS. The ∆T for April 2008 was -.079°C for an anomaly value of 0.015°C
2008 1 -0.046
2008 2 0.020
2008 3 0.094
2008 4 0.015
Click for a larger image
Reference: UAH lower troposphere data
Both RSS and UAH datasets are just slightly about the zero anomaly line, which when compared to the last peak in global temperature in January 2007, is about 0.5°C cooler. That drop in the last year seems to be holding for now.
HadCRUT (Hadley Climate Research Unit Temperature, UK) surface, land-ocean
Last month HadCRUT took a positive jump to 0.430°C but went down again this month in agreement with drops noted in RSS and UAH global datasets. This month’s anomaly is 0.250°C for a change (∆T) of -0.18°C globally from March 2008.
GISS (Goddard Institute for Space Studies, New York)
(surface, land-ocean, polar estimates)
Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
2007 .86 .63 .60 .64 .56 .53 .53 .57 .51 .55 .49 .40
2008 .12 .26 .67 .41
2008 .13 .26 .60 .41
I don’t bother plotting GISS global temperature anomaly data anymore for two reasons:
1) The format that the data is presented in requires me to do extra work to get it into an easily plotable form since it spans rows and columns, instead of being one long linear column of data for easy import.
2) I simply don’t trust the representivity of the GISS dataset. Since GISS uses polar “interpolated” data which does not exist in any of the other three datasets, I see GISS as an outlier and not truly representative of global temperature. For example, GISS interpolates from the closest high latitude surface stations and adds that data for the very high latitude arctic where no weather stations exist. None of the other 3 data sets use interpolation to create data for the arctic where no measurements exist. Hence, I have a greater degree of trust for RSS, UAH, and HadCRUT global temperature anomaly data.
And there’s more, see a post called “The Accidental Tourist” about GISS data problems, from John Goetz (originally posted on Climate Audit) which I’ve reposted as the next item down.
Reference: GISS dataset temperature index data here
In summary, it appears that all four global datasets are maintaining the drop in temperature noted globally in the last year since the last peak in January 2007. With the exception of GISS, the other three datasets show an anomaly just slightly above the zero baseline for April 2008.
UPDATE2: Thanks to Barry Hearn at http://www.junkscience.com and his processed CSV file I was able to easily plot the GISS Global Temperature anomaly without going through formatting conversions, the result is shown below:
I noted that unlike the other three metrics, GISS shows peaks in 2002 and 2007 that exceed the peak of 1998 in magnitude. How can GISS arrive at these values with combined land+ocean when HadCRUT does not? Curious.