Guest Post by Willis Eschenbach
“I am but mad north-north-west: when the wind is southerly I know a hawk from a handsaw”
William Shakespeare, Hamlet, Act II, Scene ii
Following on from my look at the USHCN temperature dataset, I have gone north (if not north-north-west) and looked at the NORDKLIM dataset. This dataset covers Norway, Sweden, Finland, Denmark, and Iceland. Of the seventy-five stations in the dataset, fifty of them have records covering the period from 1900 to 1999. Figure 1 shows the average of those selected temperatures for that period.
Figure 1. Average of the 50 long-term stations in the NORDKLIM dataset. The warmest year in the data is 1934. Photo is of Tromso, Norway, 70° North Latitude.
As before, I wanted to look at the changes in different months, to see when during the year the warming occurred. Figure 2 shows the decadal changes in the temperature for each month.
Figure 2. Decade-by-decade changes in the temperature of the Nordic countries. Photo is of Tromsoe, Norway, 70° North Latitude
As you can see, the changes are similar to those in the US. The summer temperatures have not changed. Winter temperatures (January to March) have warmed. One difference is that the winter warming is larger in the NORDKLIM temperatures.
The more I look at these datasets, the more I think that we are looking at the Urban Heat Island (UHI) effect. This is the change in the recorded temperature due to increasing development around the recording station. Increasing houses, buildings, industry, parking lots, and roads all increase the recorded temperature at nearby stations. The NORDKLIM notes say:
Especially one should notice that stations represent local conditions, which may have been effected e.g. by urbanisation
This effect is known to be greater in winter than in summer. In a study done in Barrow, Alaska, for example, there is a 4.5°C difference in the UHI effect between January and July. The winter to summer difference in the UHI in Fairbanks, Alaska is estimated to be 1.2°C.
In addition to the physical development (buildings, roads, etc.), another reason for this UHI can be seen in the photos used to illustrate the graphs. This is the direct usage of energy in the cities. For example, estimates of the energy usage for the New York City area are on the order of 5 * 10^18 joules annually. This gives a local forcing of ~ 20 W/m2.
How large an effect is this? Well, to get this amount of forcing from increasing CO2, instead of merely doubling, it would have to increase by more than forty times …
The colder the city is on average, the more effect that this will have. A building kept at 70°F (20°C) will have little effect on temperature if the local temperature is only slightly below that. If the temperature is below freezing, on the other hand, this will be a much larger effect.
In addition, the colder the weather, the more energy is put into heating the buildings. This also increases the winter UHI. As a result, we would expect the effect we have seen, that the recorded change in winter temperatures is greater in the NORDKLIM dataset than in the USHCN dataset.
My conclusion? At least part of the warming in the US and the NORDKLIM datasets is the result of UHI distortion of the records. An unknown but likely significant amount of this UHI heating is due to direct energy consumption in the cities.
And knowing how much of the temperature change is from UHI is harder than telling a hawk from a handsaw.
Do we have reliable measurement and calculation of global temp rise from satellites? If so do they show the same warming as thermometers? If they do then doesn’t that discredit the UHI effect as insignificant? Or was most of the UHI effect created before the satellites started measuring?
ASn oldy but goody, moon phase and global temp, who knew!
http://scienceonline.org/cgi/reprint/269/5228/1284.pdf
Looks like buying some carbon credits would fix the winter warming.
“This effect is known to be greater in winter than in summer. In a study done in Barrow, Alaska, for example, there is a 4.5°C difference in the UHI effect between January and July. The winter to summer difference in the UHI in Fairbanks, Alaska is estimated to be 1.2°C”
That’s the study I wanted to hear about a few articles back. Thanks!
I still suggest that given MMTS siting considerations, there’s got to be some of that January vs July delta in even “rural” monitoring sites as well.
Speaking of hawks, Nasa’s new remote flying platform is ready to measure those pesky gases and particles. Hopefully the data will be available to the public,
http://www.nasa.gov/topics/earth/features/global-hawk.html
I’ll toss out another simpler theory for northern latitudes.
The side walk effect.
Anybody who has ever shoveled a sidewalk or driveway knows the snow melts faster near the sidewalk/driveway. As long as the side walk is covered in snow the whole area stays snow covered longer.
For for places like Barrow, simple side walks hasten spring snow melt, hence a change in albedo which creates warming.
Well done.
I’ve seen the same thing in GHCN.
I used to receive NOAA HRPT images at home. (Anthony will know what those are.) I had an IR image of the midwest taken on a clear night in the winter after a polar air mass had swept across the region. All the cities, even small ones, and also all the major roads were visible as warmer areas compared to the large rural areas showing the UHI exists. Too bad I lost it. I’m sure a similar image could be found if someone wanted to plod through the NOAA archive of POES satellite image data.
Significant amount? Nearly all of it! Or at least all of it that doesn’t radiate to space without warming the air.
Some of the issues touched on here have been discussed by ATJ deLaat in a paper titled:
“Current Climate Impact of Heating from Energy Use.”
I am not sure if this has been published in a Journal but it was available as a pdf document on the net about a year back. Well worth a look.
It’s a pity that the data set doesn’t reach into the 21st century, or to be more precise to 2009 at least. Is there a collected record for northern Europe right up to very recent times? I would be most interested in a URL.
I’m betting the climate changes to colder in the next 5 years due to the extended solar minimum, my secret weapon.
Sunspot number: 0
Updated 19 Apr 2010
Spotless Days
Current Stretch: 5 days
2010 total: 12 days (11%)
2009 total: 260 days (71%)
Since 2004: 782 days
Typical Solar Min: 485 days
Solar wind
speed: 359.0 km/sec
density: 2.2 protons/cm3
http://www.spaceweather.com/
“Henry chance (14:13:22) :
Looks like buying some carbon credits would fix the winter warming.”
How about bulldozing Stockholm? 😉
I think you’ll find that the picture is actually of Tromsø, not Oslo.
Not only does USHCN data show that rural areas warmed slower than suburban areas that warmed slower than urban areas during the warming period from 1979 – 1998, but also during the cooling period from 1998 – 2008 rural areas cooled faster (etc.). Pretty conclusive from what I could see.
throw in a couple of dozen winter days missing the minus sign and voila … global warming in winter …
I would also like to see the data from 2000-2009 included as we’ve previously been told from various sources that last decade was the warmest on record.
Is the data unavailable?
I spent yesterday evening tilling my garden and now Michael (14:30:46) tells me the sun isn’t going to cooperate. Well, I’ll settle for some snow peas and radishes and probably forget the ‘maters and peppers. Who needs the heartburn anyway?
In the case of this article, be carful with attributing to much winter heating to Uban Heat Island effect. With most of these areas near or north of the Arctic Circle, there is mostly only building heat affecting UHI in the winter. Very little concrete or surface changes causing heating during the long, long nights.
In fact, it could be a method of parsing out some contributors to UHI. 🙂
It would be interesting to study the graph of one of these southern american cities, Phoenix (AZ) for example, and see if there is a temperature increase versus energy consumption correlation.
My guess is that outside temperatures in Phoenix have raised during the summers due to the increased use of air conditioning units over the decades.
It would be a nice way to prove your theory. 🙂
Rob R (14:25:12)
Many thanks for the deLaat citation, it is available here. He supports my conclusion, viz:
UHI is real and I don’t think any reasonable person would say otherwise. It seems to me the debate is not so much about is or is not but about how much. I strongly suspect the complexities of the problem will only be magnified when the local situation is considered from one location to the next. Making gross adjustments based on some model or another would be almost as problematic as making none at all. I don’t see an easy way out of this mess and that is probably why no action is being taken. What ever is done will cost plenty to do and will need to be uniform across the whole works.
I’ve always said that this is Mann-made ‘global’ warming. How the climate scientists are able to tweaze out UHI to within tenths of a degree is beyond me. Doesn’t bias ever come into it? :o)
The EPA says:
“Heat islands occur on the surface and in the atmosphere. On a hot, sunny summer day, the sun can heat dry, exposed urban surfaces, such as roofs and pavement, to temperatures 50–90°F (27–50°C) hotter than the air,2 while shaded or moist surfaces—often in more rural surroundings—remain close to air temperatures. Surface urban heat islands are typically present day and night, but tend to be strongest during the day when the sun is shining.
In contrast, atmospheric urban heat islands are often weak during the late morning and throughout the day and become more pronounced after sunset due to the slow release of heat from urban infrastructure. The annual mean air temperature of a city with 1 million people or more can be 1.8–5.4°F (1–3°C) warmer than its surroundings.3 On a clear, calm night, however, the temperature difference can be as much as 22°F (12°C).3”
http://www.epa.gov/hiri/about/index.htm
Since CO_2 forcing is logarithmic, you have to be careful how you word such statements. Maybe something like “this is forty times the amount of forcing attributed to the rise of CO_2 levels since 1900” could have been better.
Beyond that is the question of whether it is even meaningful to compare these two `forcings’ as they are not even being applied to the same system. One is a local forcing which will have a purely local effect, while the other is a global forcing will cause a more complicated global effect involving feedback mechanisms not present in the local case.
Willis, I appreciate your efforts here, and I really like the way you’re graphing the temps. I understand the UHI being more pronounced during the winter, however, when I look at the graphs, the divergence between 12 and 1, or Dec and Jan seem too large. I would have expected a more consistent flow. Of course, it could be my eyes, but I’m wondering if you’ve graphed the data with 1 or 12 at the center of the X axis? Yes, it would make for an ugly graph, but…….