One of the main reasons I am breaking the year down in the way that I am is to really show the difference between temperature anomaly data and temperature data. It also highlights the issue related to the Urban Heat Island (UHI) effect. I have been comparing the temperature of Boise, Idaho to that of McCall, Idaho. The two places are ~100 miles apart and share the same weather. A warm front will cause both places to warm up and a cold front the reverse. This is easily shown in the daily temperature data for both locations year to date.
I am using the Weather Underground as the source for the daily temperatures.
Each day uses a total of four numbers to generate the daily anomaly. The Tmax, Tmin, AverageTmax, AverageTmin. This is how the climate data is generated by the ‘official’ places like the CRU. Here are the four main temperatures for each location for the first half of 2011.
What is most interesting for both places so far this year is the constantly negative anomaly for the high temperature each day. Both locations are well below average for the daily high temperature anomaly. The low temperatures are not that different.
The important part is the different between the two locations. There is consistently a 1.6 °C difference in anomaly between the two locations. This difference is associated with urban to non-urban areas. Urban areas warm up more because of the changes to the land. Concrete warms up more than meadows. Brick buildings warm up more than forests. That is the essence of the UHI.
The Boise region has grown dramatically in the past 50 years. In 1960 the population of the entire Ada county was 93k. In 2010 that population was 392k. That growth has caused the area to change from an agricultural one to a mostly urban one. The result of that is warmer temperatures in the area. Average temperatures are based on the period when it was agricultural and now it is a different place. The result is the appearance of warming. While this is not really critical to the warming that has taken place in the past 40 years overall for the Earth, it is significant and should not be ignored. More importantly it is the places most affected by the UHI that have the oldest records. Something worth keeping in mind.
Usually the more the data is understood the clearer the potential problems are. If I said the average anomaly for the region was -1.6 °C I would be correct in a sense, but I would really be missing a lot of information. The high temperature anomaly for both locations is -3.1 °C which is about double what the average anomaly is. The NCDC gives the region an anomaly for the year so far of -0.9 °C. That is the only piece of information they provide. Knowing just a little bit more is always a good thing. In this case I know that the high temperatures for the region are significantly different than the information provided.
For those that think Skeptics ignore the science, perhaps I should remind you that the Earth was supposed to be almost a 1.0 °C warmer today than it was in 1990. According to the latest satellite data it is almost the same temperature now that it was in 1990. So if the past 21 years of CO2 emissions have resulted in no significant change in temperature, who is really ignoring the science?