Digital Diatribes

A presentation of data on climate and other stuff

April 2009 Update on Global Temperature – GISS

Posted by The Diatribe Guy on April 24, 2009

VACATION ALERT: I will not be posting for the next couple of weeks. The family and I are driving cross-country in a big honkin’ white Cargo Van. We are going to Delaware. “Why Delaware”” you may ask. It’s a valid question. I won’t get into all the details, but let’s just say that we choose our vacation destinations by drawing them out of a hat, under the theory that every place has something to offer. That theory is about to be tested… Anyway, just wanted to let you know of the upcoming hiatus.

On to temperatures…

GISS is always an interesting data set to review, because you’re never quite sure what you’re going to get. In a world where people like consensus, it is somewhat striking to me that we have general agreement between the RSS and UAH, and even the HadCrut data sets, and whenever there is an outlier it’s likely to be the GISS data set. Yet, when people quote statistics on global temperature, the GISS is the preferred set. This, despite numerous documented algorithmic data adjustments that have, over time, a non-negligible impact. Also, there is the real question of whether or not the bias of James Hansen enters into the evaluation of the data.

Nonetheless, it’s the reality we deal with that this is data that is looked to for policy decisions. So, if for that reason alone, it is worth keeping an eye on it so we can speak intelligently to what it is telling us.

First, let’s review the most recent data point:

March anomaly = 47 (in terms of .01 degrees Celsius). This was the lowest March anomaly since the year 2000. It was 18 lower than the March 2008 anomaly, but 6 higher than the February 2009 anomaly. This is quite different than UAH, where the movements were reversed.

Streak: This month’s lower year-over-year anomaly broke a streak of 6 consecutive months where the anomaly was higher year-over-year.

Rank: March 2009 ranks as the 11th highest anomaly in the data (since 1880, or 130 anomalies. 8.5 percentile.) Overall it ranks as the 95th highest anomaly in the data set of 1,551 values (6.2 percentile).

Average: The 12 month average ticked down from a recent high last month, and stands at 46.8, which puts it right at the level it was in January.

SLOPES

GISS Overall

Overall slope since 1880 is 0.04700 hundredths of a degree warming per month. For those of you who prefer simpler numbers, that translates to 0.564 degrees Celsius per century.

GISS cooling

We can extend the current trend line back to December 2001 that indicates flat temperatures (slightly negative).

The period of time where a best-fit line can be drawn that indicates no change in global temperature is not 100 months long. The last time we had a stretch of 100 consecutive months where a negative trend line could be fit was the period beginning April 1988. In recent history, during the stretch of time for which we consider the warming to be measurable, the longest stretch where a horizontal/slightly negative trend line occurs is from January 1987 through April 1997. That spans 10 years and 4 months. If our current front anchor remains at December 2000 as a starting point, we will not reach that until March 2011 – 2 years from now. So we still have a ways to go to declare that this is beyond any previous hiatus in temperature rise during a potentially warming period. It could be less time than that if some cooler temperatures are forthcoming, driving our starting point back in time a bit. Supposing we would reach that point, the previous time a flat or negative trend line of that stretch occurred is the period beginning June 1969. At this point, it seems get pretty iffy whether or not the trend line can be explained away. But we’re not at that point quite yet.

Here are some notes on the different trend periods:
60-month: Current slope = -0.1123 (-1.35 degrees Celsius cooling per Century). Kind of hovering around the same level as the last four months (ranged from -0.1086 to -0.1151). Here is the comparison to its peak slope, period ending May 2007.

GISS 60 peak

Peak 60-month trend

120-month: Current trend = +0.13341 (1.73 warming per Century). After a spurt upward, the slope level is now back to it’s lowest level in nearly a year. With the front-end anomalies dropping off preceding the 1999-2000 temperature spike, the 10-year slope is now expected to decline quite swiftly. By the end of the year it will probably be around 0.06, even at the current average temperature anomalies. here is a look at the peak trend to give an idea how much the slope has since mitigated.

120 peak

120 month peak trend line.

180-month: Current trend is +0.1344 (1.61 degrees warming per Century).

GISS 180 raw

180 month current trend.

The current slope is the lowest since the period ending June 2002. We can see the peak slope and how it has trended down in the following two charts:

GISS 180 peak

180 month peak trend.

GISS 180 slope

180 month slopes trend.

This decline is expected to continue even under the current average GISS anomalies. By year-end, it is possible that we will see slope values not seen since the period ending in 1992. To get an idea as to how these slope values have cycled, the following chart is presented:
The current slope is the lowest since the period ending June 2002. We can see the peak slope and how it has trended down in the following two charts:

GISS 180 cycle

180 month slope cycle.

240-month: Current slope = +0.153727 (1.84 degrees warming per Century).
The current slope is the lowest since the period ending June 2002. We can see the peak slope and how it has trended down in the following two charts:

GISS 240 raw

240 month trend.

The 20-year slope dipped to a recent minimum in November 2006 (+0.15379) and then trended back up to levels above 0.16. It hovered between 0.16 and 0.163 from May 2007 through October 2008. Since then, it has dropped significantly, considering it’s 240-month length. The current slope value is now the lowest since the period ending February 2003. This could potentially drop below 0.14 by year end.

300-month: Current slope = +0.156241 (1.87 degrees Celsius per Century).
The current slope is the lowest since the period ending June 2002. We can see the peak slope and how it has trended down in the following two charts:

GISS 300 raw

300 month trend.

The value of this slope had not moved much over the last year and a half until the last couple months. It has now dipped below the level it was bouncing around in during that time, and now is the lowest value in a little over a year. For comparison, here is the peak value of the 200-month trend line:
The current slope is the lowest since the period ending June 2002. We can see the peak slope and how it has trended down in the following two charts:

GISS 300 peak

300 month peak trend.

To get an idea of the cyclical pattern of the 300 month slopes:
The current slope is the lowest since the period ending June 2002. We can see the peak slope and how it has trended down in the following two charts:

GISS 300 cycle

300 month slope cycles.

360-month: Current slope value = +0.131656 (1.58 degrees warming per Century). This continues a steady decline in the slope values, showing a continued slowing in the rate of warming. The decline is presented in this chart:
The current slope is the lowest since the period ending June 2002. We can see the peak slope and how it has trended down in the following two charts:

GISS 360 slope

360 month slope trend.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

 
%d bloggers like this: