North Carolina combined temperatures

The last post in this series, on South Carolina, brought up an unexpected temperature variation that, coincidentally, was being discussed both at Real Climate and at Climate Audit. The controversy at those two sites relates to the dip in sea surface temperatures (SST's) prior to 1970, and how accurately these were measured with the controversy relating to how many ships used a thermometer stuck into a bucket to measure the temperature, and how many used a measure of the temperature made at the inlet for the engine cooling water. Not wishing to step into that argument at the moment, what is interesting to me is that while the temperatures in Georgia and South Carolina showed a drop in temperatures over the same period and a quick check shows some drop in Maine, and Vermont, but looking at Massachusetts it seems more that the higher temperatures of around 1950 are the aberrant ones. But these are land-based and therefore not subject to the variations based on how the water was collected and held. So we will see how this pans out for North Carolina.

Location of the USHCN stations in North Carolina

North Carolina has the same number of USHCN stations as South Carolina (29) but it also has four GISS stations (whereas SC had none). The four stations are at Asheville (with data from 1903, a complete set from Charlotte, Greensboro has only data from 1948 on, and Raleigh. The average of the GISS stations shows the same drop that occurred in the states further South.

Average temperature in the state of North Carolina as a function of time, using the GISS station average.

Comparing this to the homogenized data from the stations in the USHCN, the drop is found, using the larger number of stations in that set of stations.

Average temperature in the state of North Carolina as a function of time, using the USHCN homogenized temperature average.

Average temperature in the state of North Carolina as a function of time, using the Time of Observation (TOBS) adjusted raw temperature average.

North Carolina is some 500 miles long and 130 miles wide. It runs from 75.5 deg W to 84.25 deg W, and from 34 deg N to 36.35 deg N. The central latitude is at 35.60 deg N. That of the GISS stations is at 35.65 deg N, while the USHCN is at 35.6 deg N. The state rises from sea level to 2,037 m, with a mean elevation of 213.4 m. The average GISS location is at 312.7 m, while that of the USHCN stations is at 260 m.

Looking to find the population around the different stations, Cape Hatteras is more the name of the barrier island than the community, so I checked with Google Earth:

Location of the USHCN station on Cape Hatteras near Frisco.

Frisco, checking with U.S. Beacon has a population of 401, though that was in 2000 and seems, from the photo, to be low.

And Transou does not appear in citi-data, so I also went to Google Earth for it. Looking around I decided it should have a population of about 50, although it turns out to be relatively close to Laurel Springs (population 1,400).

Location of Transou station in North Carolina – while there are lots of plots ready for housing development there are not a lot of houses yet.

The population around the GISS stations averages 361,732, while that of the USHCN stations is 61,431. That population difference might have caused a 0.47 deg difference making the GISS temperatures higher, while the difference is actually 0.22 degrees. That would be more than explained (about 0.5 deg) by the difference in elevation between the two averages.

Looking at the changes in temperature with location, North Carolina has the usual relationship with latitude:

Effect of latitude on average annual temperature in North Carolina

The state rises fairly significantly to the west:

Effect of longitude on average annual temperature in North Carolina

However the temperature fall is more likely correlated with elevation (since it goes down on the other side of the mountains).

Effect of elevation on average annual temperature in North Carolina

Looking at the population effect, and considering the average temperature over the past 5 years as the dependent variable:

Effect of local population on average temperature in North Carolina

Well it seems clear that the steep drop in temperatures around 1950 occurred in North Carolina also, so does it still hold true further north?

Oh, and that drop does not show up when one subtracts the TOBS data from the homogenized USHCN values, that adjustment is more linear.

Changing times and mining shovels

I have been discussing the technologies for oil well drilling and coal mining for quite some time, and am thinking that with that review available and just about complete, it might be time to switch the focus of these Sunday information topics. While I could give a more detailed discussion of the different topics that I have covered in the past, I suspect that this would be of decreasing interest to most and so I thought to change the subject matter. What I am planning on doing is to shift focus, and start to write about the different countries that have oil reserves (or had) and what we know about them. The idea, in much the same way as with the technical talks, will be to provide an informative set of background notes, so that, for example, if the topic of the Yamal gas fields comes up, you would know a little about where they are (a peninsula in Russia), and how much gas (maybe 30 trillion cubic meters) is there, as well as how soon they will be developed (not this year).

That is the plan for the future, but before moving there, I would like to revisit coal mining to wrap up the discussion with a small number of posts about surface mining. The first use of coal came from finding outcrops where the coal could easily be picked out of the seam, or where, in the North of England, the sea would do the mining and wash the coal up on the beach, where it could be collected.

Even today there are still areas around the world where there is coal very close to the surface, which can easily be uncovered and removed. Some years ago a farmer came to my office to discuss what he needed to do to mine a layer of coal he had found in his farm (in central Missouri) just below the surface. All that was needed, he thought, was a blade for his tractor to push the soil away, and then a loader to scoop up the coal and take it to market. I had to explain that those simple times had passed, and that there was a considerable body of regulation that he had to comply with before he could do that. And also he had to restore the land to the way it was, after he was done. The profit he had anticipated, faded as he went through some of the costs that he would have to face.

However, and this was part of my first talk at the ASPO-USA meeting in Washington earlier in the month) the technology for mining that coal on the surface remains at about the level of simplicity that he anticipated. Coal supplies, whether in Africa, Asia, Europe (though to a more limited extent) and America are still available that can be extracted with nothing more than a shovel. Now, having said that, the size of the shovel has undergone a significant change since the time that I manually wielded one, to move 15 yards of coal from the face to the conveyor (as I recounted in the video). And as an aside, the shape of mining shovels differs a bit from those usually seen at the surface.

Mining shovels and a pick (with the Engineer at an early age) at the Beamish Museum in the UK

The heart-shape allowed you to get under the coal and pry in a way that the square and molded shovels more common on the surface did not, though most of them came without the cross piece at the top end. Today’s shovels are electrically powered and have bucket sizes that can pick up between 7 and 36 cubic yards of material in a single scoop. They routinely fill 400-ton haul trucks in two to three scoops in operations at the tar sands, and in mines around the world.

Modern shovel loading a haul truck (P&H )

Shovel schematic to give an idea of size – the bucket can hold 170 tons, some 60 cu yds. of material.

With that relatively large-volume, simple approach it is difficult to envisage something that can be simpler or more economic, in the mining of minerals. And as long as this technology can be applied, the need for more advanced mining means does not exist. (And this was part of the talk that I gave at the ASPO meeting).

Mining shovels such as that shown above, which are generally powered by electricity – you can see the cable if you look closely – are used for the more precise removal of material that is needed when mining the valuable material, whether tar sand, coal or a metal ore. To remove the rock and dirt that lie on top of this valuable material, where there is not quite the same need for precision, it is quite common to use a machine known as a dragline. (There is a video of one working here ) Here the bucket is not rigidly connected to the boom as with the shovel shown above, but is instead connected through ropes. This, historically, made the bucket more difficult to control. However the arrival of the computer to both monitor and control rope position, now makes it much easier to "spot" and unload the bucket than in the past.

Working dimensions for a dragline (P&H )

A bucket might move 150 cu. yds at one time with an operating radius of some 350 ft, digging down to a depth of 180 ft and dropping the spoil in a height of up to 160 ft. That doesn't mean that they don't get stuck, or collapse on occasion.

The size of the shovels thus make it possible to mine very large quantities of material at one time, and make the economics of large-scale mining practical. The critical dimension is typically the relative depth of the soil and rock over the coal seam, in relation to the thickness of the coal. It is known as the stripping ratio, so that a coal seam that is 5 ft thick, for example, at a depth of 100 ft, would have a stripping ratio of 20. Depending on the costs of mining, and the quality of the coal, that may or may not be worth going after at this time.

There are other machines that are used in different parts of the world, the largest being the bucketwheel excavator, which usually only get into the news when they are on the move.



These machines work extremely well in a controlled environment, but are extremely expensive, and when they are down, so is production. (One of the main reasons that they are no longer used in mining tar sand in Canada). Mind it is not wise to get one irritated, since they have been know to eat uppity other equipment.



That aside, the nature of the rock and other material overlying the seam will also influence how that material (which is called overburden) is removed, and I’ll discuss that process in more detail next time.

How hot is the sea?

I am currently reading Richard Heinberg’s new book “Blackout – Coal, Climate and the Last Energy Crisis,” and will, hopefully before long, give you my review. Now it does contain a fair bit on climate change, but that is not why I would have bought it, if TOD had not arranged for me to get a review copy. The reason that I am reading it, and that I will review it relates to the discussion that it continues on the availability of coal in the different nations around the world.

But even if I were to review the climate change bit (and it will be hard not to make some comments, given that it is interwoven in the discussion throughout the text) I will promise that I will not subject the book to the sort of scrutiny and, in part nit-pickiness that Gorge Monbiot is currently subjecting Ian Plimer to over his book, Heaven and Earth: Global Warming – The Missing Science. (I did get a copy of that book, and suspect that I will now read it with the several piles of criticism from a number of the sources quoted by the Guardian printed out beside me on the table. – though I note that in the week since I ordered and got my copy it has gone out of print).

However it did get me curious about the genesis and history of a couple of plots of global temperature issued by the Hadley Climate Research Unit. Some time ago I had used the plots that used to sit on the top left of the Hadley site as a source of information and comment, and the one I used was this one.


Temperature changes since 1850 (Hadley)

However just recently when I went back to look, the easy graphs to find are now these:

Temperature changes since 1850 (Met Office)

Which should not be confused with the summary plot of annual temperatures which Hadley posts:

Temperature changes since 1850 (Hadley )

The difference that has me interested in the bit between 1940 and 1970. It used to be, (top graphs) that that was, overall rather flat – agreeing also with the bottom. But if you look at the new way of combining the data, the global temperature is now shown to have been steadily increasing since 1950.

This is due to the way in which the data is now combined, since it is being done through an integration of land and sea temperatures, rather than the integration of Northern and Southern Hemispheres, or so it would appear.

Now getting the average sea surface temperature (SST) is not an easy task. To illustrate this consider this thermal picture of the Gulf Stream, and you can see the great range of temperatures as that heads out from the American Coast over to Western Europe.

Satellite thermal Image of the Gulf Stream

Thus even when you get the satellite image it is subject to interpretation. It also only reads the temperature at the skin of the surface (i.e. top 0.1 mm) rather than at any defined depth. In contrast there are also buoys out there which can give a real set of measurements at defined depths (but which still have to be weighted and integrated to get an average). And I took the following plot from a talk by David Llewellyn-Jones which shows the correlations that can be achieved.

Comparison between buoy measured (AVHRR) and satellite (ATSR) readings of SST.

One can compare this data with that from NOAA

Global temperature changes from 1880 NOAA.

This shows a slightly different path between 1940 and 1970, but again not the steady increase since 1950. The problem with the data that is used to derive the averages historically is that it has been subject to the odd correction. There were corrections made because of the use of different types of buckets to collect the water, and whether they were insulated, rather than taking the temperatures from the water in the engine inlet ports of the measuring vessel.

Different (metal canvas and wood) buckets used to measure sea surface temperature

The “first guess” estimates also tried to take into account the speed of the ships at the time of sampling (since it affected the evaporation rates and thus the amount of cooling of the sample). It was as a result of the estimates of changes in the errors caused by these different methods of reading that the actual values measured were changed.

Annual anomalies of corrected SST (solid), uncorrected SST (dotted) and corrected NMAT (dashed) for (a) northern hemisphere, (b) southern hemisphere, and (c) globe. Values have been smoothed with a 21-term low-pass binomial filter.

With the original readings being the dotted lines, you can see how the pre-1940 values have been adjusted. The original work showed that the variations between buckets and non-buckets were location sensitive., and it has been shown that it is also seasonal.

With these uncertainties it appears that there are still questions as to which data is the most accurate. The problem is also that the different techniques measure temperatures at different points in the sea, and when one changes from one method to another then corrections must be estimated and applied to bring everything to a common level. As a result the confidence that the historic data, as reported by the different Climate groups, is accurate seems less secure than it should be, given the importance that is being placed upon it.

Sadly it is more likely that the curves will be chosen which best reflect the bias of the selector and used without recognition of the potential errors and assumptions that have been made in generating it.