Saturday, March 1, 2008

Dodgy Peruvian Temperature Adjustments

There are a lot of funny things going on with the surface data compiled by the Goddard Institute for Space Studies (GISS). Many people probably believe that the raw data taken from temperature stations used to compile global temperature records are simply combined and averaged. In reality, there are a series of adjustments made to the data before it is presented to the public.

Up until recently, the raw data -- and the types of adjustments made to it -- wasn't even publicly available. Fortunately, public pressure has induced GISS and other agencies that compile temperature data to release their raw data and adjustments to the public. The result has been the discovery of some eye-opening adjustments made to the data. Not all adjustments are invalid. It is well known that as cities grow they become warmer. This is known as the Urban Heat Island (UHI) effect. It is entirely valid to attempt to remove this warming bias to get a true reading. However, many of the adjustments to the record appear to have no valid justification. The main effect of these adjustments appears to be to make recent global temperatures look warmer relative to the past. Voila, you have global warming.

One of the people taking a look at this data has been Steve McIntyre of "hockey stick" fame. His excellent website has a wealth of information on the statistical machinations of the global temperature cabal. He has also uncovered numerous seemingly wholly unjustified temperature adjustments that give the appearance of greater warming than may have actually occurred.

A recent post that caught my eye was on adjustments made to various temperature records from Peru. McIntyre presents graphics from four Peruvian temperature stations. I'm posting the Puerto Maldonado station graphic here that McIntyre created.

The black line is the plotted raw data. The red is the adjusted data. As can be clearly seen, the earlier data has been substantially adjusted downward. As much as 3 degrees. The more recent data hasn't been adjusted. The practical effect has been to change a falling trend into rising trend. Was this adjustment valid?

There are several things to take into consideration. Puerto Maldonado, the city where the temperature station is located, is the capitol city of the Department of Madre de Dios. A 2005 census put the population of the city at 51,349. It is now estimated to contain 56,917 people. The official census from 1981 put the population of the city at 12,693. An article in Conservation Biology on the effect of slash-and-burn agriculture in that region of Peru stated:

"Tambopata Province is in the Department of Madre de Dios, a remote and biodiverse region of Peru. This lowland, forested region was isolated from international markets until the rubber boom of the late 1800s, which gave rise to ribereƱo society (Amazonian residents of mixed ancestry), and decimated indigenous populations. The rubber industry collapsed in the early 1900s, and the local population remained relatively stable until the mid 1960s, when a road was constructed into Madre de Dios. Andean peasants were drawn to the region by gold, available land, and economic incentives for ranching and farming. Tambopata's population grew five-fold in 25 years, reaching 76,610 in 1997, with roughly half the population residing in the capitol city of Puerto Maldonado."*

So the population of Puerto Maldonado has grown since the 1960s, and has grown exponentially since 1981. This rapid urbanization certainly warrants an adjustment to the temperature record, but most of the adjustment should take place after 1981. Most of the adjusting done by GISS takes place prior to 1981. It is also interesting that the raw data show a cooling trend even in the face of rapid urbanization.

Here is a current satellite photograph of Puerto Maldonado from Google Earth.

As you can see, Puerto Maldonado is a good sized city. Pictures of the city can be see here, here, here, here, here, and here. According to the Weather Underground website, the temperature station in Puerto Maldonado is located at the airport. The airport is located at the bottom left corner of the above picture where there is a cluster of blue dots and one orange dot by the compass. Here's a closer look at the airport (Aeropuerto Internacionale Padre Aldamiz).

Pictures of the airport are here, here, and here. The airport is on the outskirts of the city, but has a lot of black top and concrete and is large enough to accommodate Boeing 707s.

The point of all this is that that the raw data shows a cooling trend despite rapid population growth. Adjusting the data properly should maintain or even enhance the cooling trend. Instead, the GISS adjustments created a warming trend. The warming in the record is indeed man-made, but has nothing to do with greenhouse gases.

*See: Lisa Naughton-Treves, Jose Luis Mena, Adrian Treves, Nora Alvarez, Volker Christian Radeloff (2003) Wildlife Survival Beyond Park Boundaries: the Impact of Slash-and-Burn Agriculture and Hunting on Mammals in Tambopata, Peru Conservation Biology 17 (4).


bernie said...

Interesting set of facts. However, I don't think we can say what the real trend in the temperature is until a station history is nailed down. There are simply too many factors to be considered.

Phil. said...

Not such a large city, about 2 miles X 1mile, most of the roads are dirt. The 'international airport' has a single runway about 2 miles long, completely surrounded by forest (nice job of clipping the image to avoid showing that by the way). As for 'lots of blacktop' apart from the runway it's about 200 yds square. (although that's probably more than in Puerto Maldonado itself)