Brazil’s Temperature Trends & UHI
By Paul Homewood
According to GISS, most of Brazil was a degree or more warmer last year than the 1951-80 average.
GHCN have 33 stations currently operating in the country, most of which are heavily urbanised or airport sites like Brasilia. Such sites clearly cannot be relied upon to give reliable temperature trends.
There are however 7 sites, which GISS classify as rural, based on satellite observed nightlights. In theory, GISS adjust temperatures at the urban sites for UHI, so as to align trends with the rural ones.
Sounds fine in theory? Well, let’s take a look at these rural sites.
At first sight, this one seems to confirm the trend in Brasilia. However, we learn from the GHCN station list that Sao Gabriel is also an airport location, with the sensor next to an asphalt runway. (This is a particular problem with locations like this – as the airports don’t work at night, there is no brightness for the satellite to spot, and therefore are counted as rural. Indeed, much the same applies to many small towns in out of the way places, which may be quite populous, have roads etc, but not much lighting at night).
While it is not a busy airport, the location clearly has an warming effect. The station metadata does not state how long the airport has been there, or how long the asphalt has been down.
As such, the temperature record at Sao Gabriel is worthless.
To cap it all, GHCN has decided to adjust temperatures up by about half a degree since recordings resumed a few years ago!
A very incomplete record until the last decade, during which temperatures have been declining. There is no assurance at all that the few temperature measurements taken in the 1970’s can safely be compared with current ones, in terms of quality, location etc.
Also, according to Wikipedia, Benjamin Constant has a population of 26000.
According to Wikipedia, Coari (Choary) is a Brazilian municipality in the Amazon region. It is also one of the largest cities of the Amazonas state. It is the seat of the Roman Catholic Diocese of Coari. The area has reserves of oil and natural gas, and has a population of 82000.
Barra do Corda
Again, despite its classification as rural, Barra do Corda has a population of 86000.
You’ve guessed it! According to Wikipedia, it has a population of 75000.
Cruzeiro do Sul
Population of 79000.
This one only has a population of 23000. The temperature recording station is bang in the middle of a built up area.
And that’s it! Not one station that could remotely be called a rural one. Moreover, in every case the amount of urban development that must have taken place in the last 50 years or so will have added significantly to any urban heat island effect.
To make matters worse, non rural sites are homogenised against these faux rural sites.
It is little wonder that GISS show Brazil as one of the fastest warming places on the planet.
The ugly truth is that we see this same sort of pattern in many, many parts of the world. Proper scientists would not touch any of this data with a bargepole.