1998 Controversy (NASA Y2K Bug in GW Data?)

[Pangloss]

A DailyTech blog entry has been making the news & blogosphere rounds this week in which the author discusses a potential Y2K bug that has reportedly been found in NASA's data regarding global temperatures. The study is (or so it says here) the basis for ongoing media stories saying that 1998 is the warmest year on record, but the new information (if it's accurate) states that the corrected data shows 1934 to be warmest, and that it also disturbs the upward trend, instead showing half of the "warmest years" to be in the early part of the 20th century.

 

But the article also goes on to say that this would only impact the overall warming trend by 1-2%. Which really begs the question of whether this is really an important piece of information, or just more ammunition for what Newsweek this week called the organized effort to deny global warming.

 

http://www.dailytech.com/Blogger+finds+Y2K+bug+in+NASA+Climate+Data/article8383.htm

 

My opinion is that there have become evangelists on both sides of this issue and it's important that science remain vigilant to the truth, however inconvenient or messy or complex that happens to be. I think if we do that, eventually the world will come around and take the proper, necessary actions. If that means having to correct erroneous data from time to time, so be it. Best to be up front about these things. Transparency is key.

[bascule]

Some things to consider:

 

First, the original blog providing the information, not the DailyTech (huh, "DailyTech" is an authority on climate science?)

 

http://www.norcalblogs.com/watts/2007/08/1998_no_longer_the_hottest_yea.html

 

Next, here's RealClimate's take on the matter:

 

http://www.realclimate.org/index.php/archives/2007/08/1934-and-all-that/

 

Last Saturday, Steve McIntyre wrote an email to NASA GISS pointing out that for some North American stations in the GISTEMP analysis, there was an odd jump in going from 1999 to 2000. On Monday, the people who work on the temperature analysis (not me), looked into it and found that this coincided with the switch between two sources of US temperature data. There had been a faulty assumption that these two sources matched, but that turned out not to be the case. There were in fact a number of small offsets (of both sign) between the same stations in the two different data sets. The obvious fix was to make an adjustment based on a period of overlap so that these offsets disappear.

 

This was duly done by Tuesday, an email thanking McIntyre was sent and the data analysis (which had been due in any case for the processing of the July numbers) was updated accordingly along with an acknowledgment to McIntyre and update of the methodology.

 

Contrast this with DailyTech's "silently updated" allegations...

 

The end result for US climactic data?

 

The net effect of the change was to reduce mean US anomalies by about 0.15 ºC for the years 2000-2006. There were some very minor knock on effects in earlier years due to the GISTEMP adjustments for rural vs. urban trends. In the global or hemispheric mean, the differences were imperceptible (since the US is only a small fraction of the global area).

 

There were however some very minor re-arrangements in the various rankings (see data). Specifically, where 1998 (1.24 ºC anomaly compared to 1951-1980) had previously just beaten out 1934 (1.23 ºC) for the top US year, it now just misses: 1934 1.25ºC vs. 1998 1.23ºC. None of these differences are statistically significant.

 

The end result for global climactic data?

 

In the global mean, 2005 remains the warmest (as in the NCDC analysis). CRU has 1998 as the warmest year but there are differences in methodology, particularly concerning the Arctic (extrapolated in GISTEMP, not included in CRU) which is a big part of recent global warmth. No recent IPCC statements or conclusions are affected in the slightest.

 

Sum total of this change? A couple of hundredths of degrees in the US rankings and no change in anything that could be considered climatically important (specifically long term trends).

 

The change in the global mean surface temperature is not 1-2%. The change in the global mean surface temperature is statistically negligible.

 

Move on folks, nothing to see here...

[Pangloss]

Actually I thought what he meant was that the change in *data* (warming in that sense) was only off by 1-2%. But that would suggest that the difference is even less, would it not?

[iNow]

I suppose it's helpful that the evidence about global warming is far more extant than just one NASA study.

 

 

The eggs are in many baskets.

[bascule]

Actually I thought what he meant was that the change in *data* (warming in that sense) was only off by 1-2%. But that would suggest that the difference is even less, would it not?

 

The change in regional mean surface temperature (for the US) was less than 1%

 

The change in global mean surface temperature is not even worth noting (less than thousandths of a percent)

[Pangloss]

Thanks.