I told you it was cold in California… (Green is cold on this map)
This is a ‘live map’ so will change over time and in future months or years will look quite different. For now, it has a very hot “Bos-Wash to Midwest” but with everything from Wyoming west on the cold side (but with hot spots in the cities). These maps are all much larger than shown on the page. You ought to be able to click on them to get a very large version.
Interactive map maker with more choices at:
Agriculture Does It Different
In agriculture, they worry about how well plants will grow. They worry about this a lot. So they develop ways to track and predict plant growth. Well, one of THE most effective methods uses something called Degree Days (or sometimes Crop Heat Units or Growth Heat Units or…)
The basic idea is to take the MIN-MAX average for the day, difference it from a base value for your crop, then sum up how many heat units you have as a running total. For each crop there is a total number that says “I’m Ripe Now” and you must reach that number before you run out of growing season. As the total racks up, it also lets you know how soon to schedule the harvesting crews. Not too surprisingly, various insects also develop based on ‘degree days’ and emerge as pests right on queue with plant growth stages.
I’m rather fond of the way this site describes the process:
Different methods exist for calculating heat units depending on a) the crop or biological organism of interest and b) the whim or personal preference of the researcher. The calculation method most commonly used throughout the U.S. for determining heat unit accumulation relative to corn phenology is the formula first suggested by the National Oceanic and Atmospheric Administration in 1969 and labeled as the “‘Modified Growing Degree Day” formula in 1971.
This method calculates daily accumulation of GDDs as the average daily temperature (degrees F) minus 50. The “modification” refers to the limits imposed on the daily maximum and minimum temperatures allowed in the calculation. Daily maximums greater than 86 degrees F are set equal to 86 in the calculation of the daily average temperature. Similarly, daily minimums less than 50 degrees F are set equal to 50 in the calculation.
I like that “whim of the researcher” part. It is true, but the reality is that the ‘degree days’ calculated with a 41 degree reference point will not be dramatically different from the 40 point and most crops will not care which one you use (as long as you have calibrated that crop on that scale…) while repeatedly doing math in your head with 40 is likely easier than 41 for most folks, so a researcher may be prone to picking 41 vs 40 based on ‘whim’…
The Wiki that describes Degree Days is not too bad (at least for now, but since I’ve connected it to Global Warming watch out for the AGW Langoliers to start chewing on it…):
There is an interesting chart that shows typical baselines used for a sample of crops. In particular, note that the USDA zone maps are based on degree days with a very high baseline:
10 °C is the most common base for GDD calculations, however, the optimal base is often determined experimentally based on the lifecycle of the plant or insect in question.
5.5 °C wheat, barley, rye, oats, flaxseed, lettuce, asparagus
6 °C stalk borer moth
7 °C Corn rootworm
8 °C sunflower, potato
9 °C Alfalfa weevil
10 °C maize (including sweet corn), sorghum, rice, soybeans, tomato, Black cutworm, European Corn Borer, standard baseline for insect and mite pests of woody plants
11 °C Green Cloverworm
12 °C many other crop calculations
30 °C the USDA measure heat zones in GDD above 30 °C; for many plants this is significant for seed maturation, e.g. reed (Phragmites) requires at least some days reaching this temperature to mature viable seeds
GDDs may be calculated using either Celsius or Fahrenheit, though they must be converted appropriately; 5 GDDC = 9 GDDF
In Canada, they have a much shorter growing season than in California, and depend on more cold tolerant crops, so use lower reference points than the 50F for nighttime and have an interesting take on the night vs day temps:
Daily crop heat units are calculated from these min and max temperatures. There are separate calculations for day and night. The daytime relationship uses 10 °C (50 °F) as the base temperature and 30 °C (86 °F) as the optimum because warm-season crops do not develop when daytime temperatures fall below 10 °C and they develop fastest at about 30 °C. The nighttime relationship uses 4.4 °C (40 °F) as the base temperature and does not specify an optimum temperature because nighttime minimum temperatures very seldom exceed 25 °C in Ontario. The nighttime relationship is a straight line on the graph (Figure 1),while the daytime relationship is a curve that records greater crop heat units at 30 °C than at higher or lower temperatures. Daily crop heat units are calculated by using the average of the two daily values from the equations given in Figure 1 or they can be read from the matrix in Appendix I.
So you can see that ‘degree days’ matter and that if you get it wrong you have Big Problems.
Why Does It Matter To Non-Farmers?
Because it is a very fine grained process and because it has to be right or folks don’t eat.
None of this “Global Average” stuff and homogenizing the world either. It has to be accurate on YOUR FARM, not 3 counties over. None of this “3 thermometers on the SoCal Beach and one at S.F. Airport” like GHCN does for California either. You need to have lots of temperatures to make a fine grained product.
OK, I was tooling around looking into the Degree Days on the west coast (due to the complete lack of things to harvest from my way too late garden… We’ll, I did get one small yellow squash that made a side dish for two people. For mid-July in Coastal California that is just crazy. I’ve also got a handful of Dragon’s Tongue beans, but I’m running them to seed – and it ought to be a colander full… but I digress. It just isn’t what it ought to be as it’s been darned cold at night and not very warm mid-day.)
So I stumbled on this site:
and it lets you pick any of 3 major temperature points for your type of crop and see a map of Washington State for degree days to date. OR the variance from the 30 year average. This is the deviation chart:
The blue and red are ‘warmer’ and the green and tan are ‘cooler’. Uncolored is the same as the 30 year average.
What I find interesting about this map is the way the warmth is concentrated on and around nearly point sources. That one inland and North East from Seattle is a real hot spot. Those sources look to be largely the urban growth areas (with, perhaps, some very localized UHI impacts on small rural locations). There is a general ‘warming’ in valleys, but the real ‘hot spots’ are in or very near the urban areas. Most of the ‘out back’ rural areas are neutral or cooler than average.
For comparison, here is a Washington map of cities and roads:
This is particularly interesting in light of where GHCN has concentrated the “Global Thermometers”. They are largely moved to airports in valleys or near the coastline. (Folks don’t build major airports on the tops of mountains… it’s hard to get 10,000 feet of straight and level on a mountain top, and the cities are typically down in the valleys.)
So, to me, just looking at the Degree Day map explains a great deal about our “Global Warming”. We’ve moved the thermometers to where the people are located, down in the valleys, and put them at the airports where solar heating works really really well on black tarmac. But go ‘out in the country’ and it’s not so hot… and as in the case of Washington, it’s even below average and quite cold.
For Washington we could clearly make either a warming or a cooling ‘trend’ by simply choosing where we put the thermometers.
I’m presently wandering my way through other states. First stop after Washington was Oregon. This is a ‘live map’ so will change over time. But it’s the same pattern as Washington.
Gee, it’s hot in Reno and Las Vegas and the L.A. Basin is warmer than inland. Wonder why that’s where NOAA / NCDC choose to measure the temperatures for GHCN?
My final point here would be pretty simple: With the rather dramatic variation over very short geographical scales we would need far more than the slightly over 1000 thermometers used by GHCN to get any kind of accuracy in the global temperature picture. The GHCN data set is just not fine grained enough to avoid selection bias issues given the wide variation of temperatures on these graphs over very short geographic scales.
Further, there is a clear tendency for urban and valley areas to be anomalously hot (such as in Washington and Oregon, though oddly in California the Central Valley is cooler than usual – I would guess due to the extra clouds we’ve been having).. IMHO, this warmth is most likely because that is where the people are, where they run heaters and air conditioners, and where there are millions of cars on black tarmac and tons of aviation fuel being burned for take-offs at all the airports. Given that, the placement of the majority of GHCN thermometers at airports and in or near urban and low elevation locations introduces a clear bias to the basic data used in all the climatology studies.
Basically, we need a new data set and it needs to be a very fine grained one with full representation of the rural and high altitude areas. The present GHCN data set is polluted with selection bias that preferentially puts thermometers in lower elevations, near coastlines, and at airports in or near urban areas. Exactly the kinds of places shown to have ‘abnormal warming’ in the above fine grained maps.
On this map of Texas and nearby, it’s remarkably easy to pick out the Dallas-Fort-Worth metroplex. Almost as easy are the hot spots over Galveston and Oklahoma City. Abilene is the hot spot about 1/2 way from Dallas to New Mexico. Then there is El Paso, lit up like a bonfire. And above it Santa Fe New Mexico. The odd one for me was the hot spot almost on the Texas border and about 45 degrees SE of Santa Fe. Making the 3 rd point of a roughly equilateral triangle with El Paso and Abilene. There’s no there, there, I’m thinking…
Then I remembered a long ago time when I helped a friend move his ‘stuff’ from Clovis. Middle of nowhere. Where that hot spot is. And a US Air Base… (He was retired Air Force). Gotta love those large rural US Airbase facilities. Nice and warm places to put thermometers…
I can see that this new Shiny Toy is going to be having me running around for a while… Doing a search for an Australian Degree Day map turned up this chart of vintage years degree days:
It sure looks to me like no net heat gain in Australian Vineyards. Nice cyclical rolling motion, though. Bit ‘o warm in 2001, then a gentle fall off back to a lower normal range. 2004 ought to be a nice vintage for German Style whites… I’d expect the 2001 vintage to have been picked early for the reds, lest they be thin. But a properly harvested Australian Red from 2001 could be quite nice, especially the lighter styles. If the same pattern held for New Zealand, they might well have gotten enough heat to make some reds with rich body. (Often, New Zealand is not hot enough to make a sturdy red. They make wonderful wines, but a lighter style. I’ll have to look up a 2001 N.Z. red and see how it is..)