I’ve moved to WordPress: http://bobtisdale.wordpress.com/

Monday, May 31, 2010

GISS Deletes Arctic And Southern Ocean Sea Surface Temperature Data

I’ve moved to WordPress.  This post can now be found at GISS Deletes Arctic And Southern Ocean Sea Surface Temperature Data

There are numerous blog posts and discussions about how the GISS global temperature anomaly product GISTEMP differs from the Hadley Centre and NCDC datasets. The repeated reasons presented for this are, GISS uses 1200km radius smoothing to fill in the areas of the globe with sparse surface temperature readings, and the area this has the greatest impact is the Arctic. Typically, a map or comparison of global temperature anomaly maps is included, similar to Figure 1. The top two maps were cropped from Figure 3 in the Real Climate post “2009 temperatures by Jim Hansen”. I added the third. The bottom map was created at the GISS Global Maps webpage. It’s a map of the GISTEMP Global Temperature Anomaly product with 250km radius smoothing for the calendar year 2005, the same year as the top two maps. I did not include a temperature scale because the bottom map was provided to allow a visual comparison of the spatial coverage of the HadCRUT product and the GISTEMP product with 250km radius smoothing. Examine the Arctic and the ocean surrounding Antarctica, the Southern Ocean. Notice a difference? In 2005, the HadCRUT data had better coverage of the Arctic and Southern Oceans than the GISTEMP dataset with 250km radius smoothing. What’s missing in the GISTEMP product? There’s no sea surface temperature data.

Figure 1


The general regions where GISS deletes Sea Surface Temperature data are shown in Figure 2. Three areas are highlighted: two cover the Arctic Ocean, and a third surrounds Antarctica. The specific locations are clarified in the following. GISS then uses their 1200km radius smoothing to replace the sea surface data with land data.
Figure 2

Tilo Reber in his recent “Diverging views” post at Watts Up With That? noted that the GISS Current Analysis webpage includes the following statement:

“Areas covered occasionally by sea ice are masked using a time-independent mask.”

This means that vast regions of Sea Surface Temperature (SST) anomaly data in the Arctic Ocean and Southern Ocean are deleted from the GISTEMP record. GISS does not delete all of the Arctic and Southern Ocean SST anomaly data, just the data from the areas where the annual sea ice melt occurs, and those are good portions of them.

I have looked for but have not found an explanation for this exclusion of Sea Surface Temperature data in the papers provided on the GISTEMP references page.

Figure 3 shows four Arctic (North Pole Stereographic, 65N-90N) maps prepared using the map-making feature of the KNMI Climate Explorer. The maps illustrate temperature anomalies and sea ice cover for the month of September, 2005. The calendar year 2005 was chosen because it was used in the RealClimate post by Jim Hansen, and September is shown because the minimum Arctic sea ice coverage occurs then. The contour levels on the temperature maps were established to reveal the Sea Surface Temperature anomalies. Cell (a) shows the Sea Ice Cover using the Reynolds (OI.v2) Sea Ice Concentration data. The data for the Sea Ice Cover map has been scaled so that zero sea ice is represented by grey. In the other cells, areas with no data are represented by white. Cell (b) illustrates the SST anomalies presented by the Reynolds (OI.v2) Sea Surface Temperature anomaly data. GISS has used the Reynolds (OI.v2) SST data since December 1981. It’s easy to see that SST anomaly data covers the vast majority of Arctic Ocean basin, wherever the drop in sea ice permits. Most of the data in these areas, however, are excluded by GISS in its GISTEMP product. This can be seen in Cell (c), which shows the GISTEMP surface temperature anomalies with 250km radius smoothing. The only SST anomaly data used by GISS exists north of the North Atlantic and north of Scandinavia. The rest of the SST data has been deleted. The colored cells that appear over oceans (for example, north of Siberia and west of northwestern Greenland) in Cell (c) are land surface data extending over the Arctic Ocean by the GISS 250km radius smoothing. And provided as a reference, Cell (d) presents the GISTEMP “combined” land plus sea surface temperature anomalies with 1200km radius smoothing, which is the standard global temperature anomaly product from GISS. Much of the Arctic Ocean in Cell (d) is colored red, indicating temperature anomalies greater than 1 deg C, while Cell (b) show considerably less area with elevated Sea Surface Temperature anomalies.
Figure 3

Basically, GISS excludes Arctic Ocean SST data from 65N to 90N and, for round numbers, from 40E to 40W. This is a good portion of the Arctic Ocean. Of course, the impact would be seasonal and would depend on the seasonal drop in sea ice extent or cover. The sea ice extent or cover has to decrease annually in order for sea surface temperature to be measured. I’ll use the above-listed coordinates for the examples that follow, but keep in mind that they do not include areas of sea ice in the Northern Hemisphere south of 65N where sea surface temperature data are also deleted by GISS. These additional areas are highlighted in Figure 4. They include the Bering Sea, Hudson Bay, Baffin Bay and the Davis Strait between Greenland and Canada, and the Sea of Okhotsk to the southwest of the Kamchatka Peninsula.
Figure 4

Note: GISS uses Hadley Centre HADISST data as its source of Sea Surface Temperature (SST) data from January 1880 to November 1981 and NCDC Reynolds (OI.v2) data from December 1981 to present. To eliminate the need to switch between or merge SST datasets, this post only examines the period from 1982 to present. And to assure the graphics presented in Figures 3 and 6 are not biased by differences in base years of the GISTEMP data and the Reynolds (OI.v2) SST data, the latter of which has only been available since November 1981, I’ve used the period of 1982 to 2009 as base years for all anomaly data.

Land Surface Temperature variations are much greater than Sea Surface Temperature variations. Refer to Figure 5. Since January 1982, the trend in GISTEMP Arctic Land Surface Temperature Anomalies (65N-90N, 40E-40W) with 250km radius smoothing is approximately 8 times higher than the Sea Surface Temperature anomaly trend for the same area. The Arctic Ocean SST anomaly linear trend is 0.082 deg C/ decade, while the linear trend for the land surface temperature anomalies is 0.68 deg C/decade. And as a reference, the “combined” GISTEMP Arctic temperature anomaly trend for that area is 9 times the SST anomaly trend.
Figure 5

By deleting the Sea Surface Temperature anomaly data, GISS relies on the dataset with the greater month-to-month variation and the much higher temperature anomaly trend for its depictions of Arctic temperature anomalies. This obviously biases the Arctic “combined” temperature anomalies in this area.


Figure 6 shows four maps of Antarctica and the Southern Ocean (South Pole Stereographic, 90S-60S). It is similar to Figure 8. Cell (b) illustrates the SST anomalies presented by the Reynolds (OI.v2) Sea Surface Temperature anomaly data. SST anomaly data covers most of the Southern Ocean, but GISS deletes a substantial portion of it, as shown in Cell (c). The only SST anomaly data exists toward some northern portions of the Southern Ocean. These are areas not “covered occasionally by sea ice”.
Figure 6

Figure 7 illustrates the following temperature anomalies for the latitude band from 75S-60S:
-Sea Surface Temperature, and
-Land Surface temperature of the GISTEMP product with 250km radius smoothing, and
-Combined Land and Sea Surface of the GISTEMP product with 1200km radius smoothing, the GISTEMP standard product.

The variability of the Antarctic land surface temperature anomaly data is much greater than the Southern Ocean sea surface temperature data. The linear trend of the sea surface temperature anomalies are negative while the land surface temperature data has a significant positive trend, so deleting the major portions of the Southern Ocean sea surface temperature data as shown in Cell (c) of Figure 6 and replacing it with land surface temperature data raises temperature anomalies for the region during periods of sea ice melt. Note that the combined GISTEMP product has a lower trend than the land only data. Part of this decrease in trend results because the latitude band used in this comparison still includes portions of sea surface temperature data that is not excluded by GISS (because it doesn’t change to sea ice in those areas).
Figure 7


When you create a map at the GISS Global Maps webpage, two graphics appear. The top one is the map, examples of which are illustrated in Figure 1, and the bottom is a Zonal Mean graph. The Zonal Mean graph presents the average temperature anomalies for latitudes, starting near the South Pole at 89S and ending near the North Pole at 89N. Figure 8 is a sample. It illustrates the changes (rises and falls) in Zonal Mean temperature anomalies from 1982 to 2009 of the GISTEMP combined land and sea surface temperature product with 1200km radius smoothing. The greatest change in the zonal mean temperature anomalies occurs at the North Pole, the Arctic. This is caused by a phenomenon called Polar Amplification.
Figure 8

To produce a graph similar to the GISS plot of the changes in Zonal Mean Temperature Anomalies, I determined the linear trends of the GISTEMP combined product (1200km radius smoothing) in 5 degree latitude increments from 90S-90N, for the years 1982 to 2009, then multiplied the decadal trends by 2.8 decades. I repeated the process for HADCRUT data. Refer to Figure 9. The two datasets are similar between the latitudes of 50S-50N, but then diverge toward the poles. As noted numerous times in this post, GISS deletes sea surface temperature data at higher latitudes (poleward of approximately 50S and 50N), and replaces it with land surface data.
Figure 9

Figure 10 shows the differences between the changes in GISTEMP and HADCRUT Zonal Mean Temperature Anomalies. This better illustrates the divergence at latitudes where GISS deletes Sea Surface Temperature data and replaces it with land surface temperature anomaly data, that latter of which naturally has higher linear trends during this period.
Figure 10

There appears to be some confusion in the comments in the WattsUpWithThat thread of my post GISS Deletes Arctic And Southern Ocean Sea Surface Temperature Data about what this post illustrates. I prepared a graph for this post but chose not to use it since it appeared redundant to me. It should clarify what is being presented. It is a comparison graph of GISTEMP Arctic Surface Temperature anomalies for the grid 65N-90N, 40E-40W, which is a major portion of Arctic Ocean as shown above in Figure 4. One dataset is the combined land plus sea surface data; the other is the land-only data. The two datasets are identical. If you subtract one from the other, the difference is 0.0 (zero) for all months. This indicates that there is no Sea Surface Temperature data in the combined product in this grid.
Update Figure 1

Does the Sea Surface Temperature data exist for this area? Yes. It is illustrated above as the green curve in Figure 5.

To me, this indicates that GISS deleted the sea surface temperature data for this portion of the Arctic.

Maps and data of sea ice cover and temperature anomalies are available through the KNMI Climate Explorer:

Monday, May 24, 2010

Mid-May 2010 SST Anomaly Update

I’ve moved to WordPress.  This post can now be found at Mid-May 2010 SST Anomaly Update
NOTE: The weekly OI.v2 SST data is available in two periods through the NOAA NOMADS website, from November 1981 to 1989, and from 1990 to present. I’ve been providing these mid-month updates with graphs that include the full term of the second batch of data. It’s really impossible to tell from those graphs what has transpired over the past few weeks due to the length of the dataset, so I’ve added shorter-term graphs, beginning in 2004, to make the wiggles visible.


NINO3.4 SST anomalies for the week centered on May 19, 2010 show that central equatorial Pacific SST anomalies are below zero and continuing their decline. Presently they’re at -0.21 deg C, which is in ENSO-neutral levels.
NINO3.4 SST Anomalies
NINO3.4 SST Anomalies - Short-Term

Weekly Global SST anomalies are still elevated, but they may have peaked for this El Nino. They are starting to show signs of a drop in response to the decline in central equatorial Pacific temperatures, but the global weekly data is much too variable to tell for sure.
Global SST Anomalies
Global SST Anomalies - Short-Term

OI.v2 SST anomaly data is available through the NOAA NOMADS system:

Wednesday, May 19, 2010

Tom Karl’s Trends Are Wrong - At Least in Slide 21

I’ve moved to WordPress.  This post can now be found at Tom Karl’s Trends Are Wrong – At Least in Slide 21
Correction: I have been advised that my Figure 4 in this post could be considered misleading because the trends intersect at 1900 and not toward the middle of the plot. The following illustration is a correction. It still shows, however, that the differences between two trends of 0.83 and 0.91 deg C/Century should be visible. (Thanks, Basil.)

Correction To Figure 4

A number of bloggers on the WattsUpWithThat thread “Tom Karl’s Senate Dog & Pony Show – it’s worse than we thought, again” noted the curious errors in the trend lines in Tom Karl’s presentation to Senate. The one that stood out for me was slide 21, presented here as Figure 1. It showed the global land surface temperature anomalies and linear trends for the new (Version 3) versus existing (Version 2) Global Historical Climatology Network (GHCN) dataset.
Figure 1

First Observation: The slide title states the data is monthly, but the data illustrated are annual averages. Figure 2 is a graph of monthly Global Land Surface Temperature anomalies presented by the NCDC from January 1900 to April 2010. Monthly global land surface temperature anomaly data should look like that, with lots of month-to-month variation.
Figure 2

Second, there are two linear trends listed on the Karl slide. Version 2 is noted to have a linear trend of 0.83 deg C/Century, while Version 3 is claimed to have a linear trend of 0.91 deg C/Century. But the trend lines are nearly identical and they present linear trends of approximately 0.75 deg C/Century, Figure 3. The trend lines are erroneous or the values listed for the trends are wrong.
Figure 3

Trend lines of 0.83 and 0.91 deg C/Century should be noticeably different, as shown in Figure 4.
Figure 4

And for reference, the NCDC’s Monthly Global Land Surface Temperature anomaly data, Figure 5, has a linear trend of 0.78 deg C/Century.
Figure 5

And the the NCDC’s Annual Global Land Surface Temperature anomaly data, Figure 6, has a linear trend of 0.77 deg C/Century.
Figure 6

Makes one wonder. If a simple comparison graph with linear trends is so error filled…

Tom Karl’s Powerpoint Presentation is available here:

A full-sized copy of Slide 21 is here:

The NCDC Land surface temperature anomaly data is available through the KNMI Climate Explorer:

Monday, May 17, 2010

NINO3.4 SST Anomalies Are Now Negative

I’ve moved to WordPress.  This post can now be found at NINO3.4 SST Anomalies Are Now Negative
I just took a quick look at NINO3.4 SST Anomalies, and for the week centered on Wednesday May 12th, they’ve dropped into negative numbers: -0.075 deg C.
NINO3.4 SST Anomalies – Week Of May 12, 2010


OI.v2 SST anomaly data is available through the NOAA NOMADS website:

Monday, May 10, 2010

April 2010 SST Anomaly Update

I’ve moved to WordPress.  This post can now be found at April 2010 SST Anomaly Update

The map of Global OI.v2 SST anomalies for April 2010 downloaded from the NOMADS website is shown below. The drop in central equatorial Pacific SST anomalies toward ENSO-neutral temperatures is obvious. The response should work its way eastward over the next couple of months.
April 2010 SST Anomalies Map (Global SST Anomaly = +0.32 deg C)


NINO3.4 SST anomalies are dropping but El Niño conditions remained during April in the central tropical Pacific (Monthly NINO3.4 SST Anomaly = +0.68 deg C). Weekly data has fallen into ENSO-neutral ranges (+0.30 deg C). Global SST anomalies increased slightly again during April (0.017 deg C). On a hemispheric basis, the rise was limited basically to the Northern Hemisphere, since the increase in the Southern Hemisphere was negligible (0.002 deg C). And looking at the major ocean basins, the North Pacific, South Atlantic, Indian Ocean, and the East Indian-West Pacific Ocean datasets all show drops this month, but they were not strong enough to outweigh the rises in the North Atlantic and South Pacific.
Monthly Change = +0.017 deg C
NINO3.4 SST Anomaly
Monthly Change = -0.46 deg C


The SST anomalies in the East Indian and West Pacific have ended (temporarily) their lagged rise in response to the El Niño . Will they also rise, noticeably, in response to a La Niña as they have in the past? Will there even be a La Niña following this El Niño? Refer to Typical (Average) El Nino, Traditional El Nino, and El Nino Modoki Events.

I’ve added this dataset in an attempt to draw attention to the upward step response. Using the 1986/87/88 and 1997/98 El Niño events as references, East Indian-West Pacific SST Anomalies peak about 7 to 9 months after the peak of the NINO3.4 SST anomalies, so we shouldn’t expect any visible sign of a step change for almost 18 to 24 months. We’ll just have to watch and see.
East Indian-West Pacific (60S-65N, 80E-180)
Monthly Change = -0.114 deg C

Further information on the upward “step changes” that result from strong El Niño events, refer to my posts from a year ago Can El Niño Events Explain All of the Global Warming Since 1976? – Part 1 and Can El Niño Events Explain All of the Global Warming Since 1976? – Part 2

And for the discussions of the processes that cause the rise, refer to More Detail On The Multiyear Aftereffects Of ENSO - Part 2 – La Niña Events Recharge The Heat Released By El Niño Events AND...During Major Traditional ENSO Events, Warm Water Is Redistributed Via Ocean Currents -AND- More Detail On The Multiyear Aftereffects Of ENSO - Part 3 – East Indian & West Pacific Oceans Can Warm In Response To Both El Niño & La Niña Events


The MONTHLY graphs illustrate raw monthly OI.v2 SST anomaly data from November 1981 to April 2009.

Northern Hemisphere
Monthly Change = +0.036 deg C
Southern Hemisphere
Monthly Change = +0.002 deg C
North Atlantic (0 to 75N, 78W to 10E)
Monthly Change = +0.156 deg C
South Atlantic (0 to 60S, 70W to 20E)
Monthly Change = -0.037 deg C

Note: I discussed the upward shift in the South Atlantic SST anomalies in the post The 2009/10 Warming Of The South Atlantic.

North Pacific (0 to 65N, 100 to 270E, where 270E=90W)
Monthly Change = -0.083 Deg C
South Pacific (0 to 60S, 145 to 290E, where 290E=70W)
Monthly Change = +0.105 deg C
Indian Ocean (30N to 60S, 20 to 145E)
Monthly Change = -0.072 deg C
Arctic Ocean (65 to 90N)
Monthly Change = +0.024 deg C
Southern Ocean (60 to 90S)
Monthly Change = -0.109 deg C


The weekly NINO3.4 SST anomaly data illustrate OI.v2 data centered on Wednesdays. The latest weekly NINO3.4 SST anomalies are +0.30 deg C. They’re working their way down. How low will they go?
Weekly NINO3.4 (5S-5N, 170W-120W)


The Optimally Interpolated Sea Surface Temperature Data (OISST) are available through the NOAA National Operational Model Archive & Distribution System (NOMADS).

Monday, May 3, 2010

NINO3.4 SST Anomalies In Neutral Territory

I’ve moved to WordPress.  This post can now be found at NINO3.4 SST Anomalies In Neutral Territory
Just a quick post. The weekly OI.v2 NINO3.4 SST anomalies dropped out of El Niño range last week, the week centered on Wednesday April 28th. They are presently at ~0.47 deg C.
Weekly NINO3.4 SST Anomalies

I’ll provide the monthly update for April on Monday when the monthly data is official.


OI.v2 SST data is available through the NOAA NOMADS website:

The 2009/10 Warming Of The South Atlantic

I’ve moved to WordPress.  This post can now be found at The 2009/10 Warming Of The South Atlantic
The Sea Surface Temperature (SST) anomalies for the South Atlantic are shown in Figure 1. First observation: it’s a noisy dataset. Then, other than the dip and rebound in 1991/92, likely caused by the eruption of Mount Pinatubo, and other than the mysterious dip and rebound that occurred in 1996/97, SST anomalies have been relatively flat there from the late 1980s to the late 1990s. Until 2009/2010. The normal dip after the seasonal spike did not occur early in 2009. SST anomalies rose instead.
Figure 1

This post will illustrate when and where the multiple warmings occurred in the South Atlantic during 2009, and it will illustrate if they appear to be normal or abnormal occurrences when compared to past variations.

Figure 2 shows four monthly SST anomaly maps for the South Pacific and South Atlantic. Cell a, January 2009, shows a strong warming in the mid latitudes, 50S-30S, along what appears to be the Antarctic Convergence Zone. In Cell b, May 2009, the mid-latitude warming is nearing its end, but there is a short spike in SST anomalies along the equatorial Atlantic. In cells c and d, the low-latitude warming, 30S-10S, is highlighted.
Figure 2

The low-latitude warming appears to begin just before the start of the secondary rise in NINO3.4 SST anomalies and continued until recently. What I’m referring to as a secondary rise can be seen in Figure 3. NINO3.4 SST anomalies paused during July through September then rose again in October until the peak in December.

Figure 3

The mid-latitude (50S-30S, 70W-20E) SST anomalies for the South Atlantic are shown in Figure 4. The warming in the early part of 2009 is not unusual. Larger spikes occurred in 1999/00 and 2001/03, and an earlier spike reached a similar magnitude in 1991. What is unusual in 2009 is the duration of the warming at these latitudes, having lasted a good portion of the year.
Figure 4

Figure 5 is a comparison of the mid-latitude SST anomalies with the SST anomalies for the entire South Atlantic basin. The mid-latitudes do account for part of the noise in the South Atlantic data, but note that the curious 1996/97 dip and rebound does not occur in the mid latitudes.
Figure 5

Comparing the mid-latitude SST anomalies of the South Atlantic to NINO3.4 SST anomalies, Figure 6, raises more questions than it answers. Are the spikes in 1999/00 and 2001/03 lagged responses to the 1997/98 El Niño, or seeming more likely, are they lagged responses to the variations of the 1998/99/00/01 La Niña? They do not appear to be responses to the Southern Annular Mode. (Not illustrated.)
Figure 6

I’m not going to spend much time on this area since the equatorial warming in mid year of 2009 lasted a month. Recall in Cell b of Figure 2, there was a warming in May 2009 along the equator. The very short mid-year warming and the timing are not unusual as can be seen in Figure 7.
Figure 7

Figure 8 compares the equatorial Atlantic SST anomalies to NINO3.4 SST anomalies. The equatorial Atlantic SST anomalies respond to some (the more significant) El Niño events, but not others (those that are less significant). Note the multiyear decays in the equatorial Atlantic SST anomalies after the 1986/87/88 and 1997/98 El Niño events. This is yet another SST anomaly dataset that does not respond to La Niña events.
Figure 8

The South Atlantic low latitude SST anomalies are illustrated in Figure 9. This is the area with the significant warming in the latter part of 2009. Refer back to Cells c and d of Figure 2. What stands out for me with this dataset is how flat it is for most of the term. How flat?
Figure 9

If we shorten this dataset to the period from July 1983 to November 2008 (the bottoms of the troughs in those years), Figure 10, the linear trend is 0.08 deg C per CENTURY. Can’t get much flatter than that.
Figure 10

Figure 11 is a comparison of South Atlantic low latitude SST anomalies and the SST anomalies for the South Atlantic basin. Though there are periods of divergence, the variations of the low-latitude data correlate well with the basin data--the low latitudes exaggerating the basin data.
Figure 11

Smoothing those two datasets and comparing them to NINO3.4 SST anomalies reveals the influence of major ENSO events on the South Atlantic, and the lack of influence of minor ENSO events.
Figure 12

Let’s take a look at the longer-term HADISST SST anomaly data for the South Atlantic and the Low Latitudes of the South Atlantic. While the responses of those datasets to the 2009/10 El Niño was significant, they are dwarfed by the reactions to the 1972/73 El Niño. Refer to Figure 13.
Figure 13

Note how the South Atlantic data remains relatively flat from the late 1950s to the early 1970s. It shifts up approximately 0.1 deg C after the 1972/73 El Niño, then remains flat from ~1976 to 1983. It clearly shifts again ~0.2 deg C in 1982/83, then remains relative flat for the next few decades. Curious.

I began writing this post a few weeks ago, and as I always do, I created the graphs first. Just to keep the post somewhat up-to-date, Figure 14 is a comparison graph of the weekly SST anomalies for the Low Latitudes of the South Atlantic and for the South Atlantic basin starting in January 2000 and ending on the week centered on April 28, 2010. Both datasets have begun their declines. The question now is: how low will they go?
Figure 14

As part of a long-term project, I’ve been creating animations of SST anomalies where I’ve used the averaging feature (12-month) of the KNMI Climate Explorer map-making software in an attempt to minimize the seasonal variations and weather noise. So far the animations have looked good. Example: Figure 15 is a .gif animation of Atlantic SST anomalies that captures the 1996/97 dip and rebound in the South Atlantic. It appears to show the dip was a response to the unofficial (very weak) La Niña of 1996/97
Figure 15

Figure 16 shows the Atlantic SST anomalies for the Atlantic for approximately the same period but without the smoothing. It would be difficult at best to determine what caused the dip from that animation.
Figure 16

The maps in Figure 2 and the OI.v2 SST anomaly data are available through the NOAA NOMADS website:

The HADISST data and the enhanced map-making features used to create the animations are available through the KNMI Climate Explorer:


Tips are now being accepted.

Comment Policy, SST Posts, and Notes

Comments that are political in nature or that have nothing to do with the post will be deleted.
The Smith and Reynolds SST Posts DOES NOT LIST ALL SST POSTS. I stopped using ERSST.v2 data for SST when NOAA deleted it from NOMADS early in 2009.

Please use the search feature in the upper left-hand corner of the page for posts on specific subjects.
NOTE: I’ve discovered that some of the links to older posts provide blank pages. While it’s possible to access that post by scrolling through the history, that’s time consuming. There’s a quick fix for the problem, so if you run into an absent post, please advise me. Thanks.
If you use the graphs, please cite or link to the address of the blog post or this website.