Missing News: BoM admits to hot cities

BOM finally finds UHI in Australia's temperature record, and somehow ABC don't find it newsworthy!

Bureau of Meteorology

Wednesday 13 October 2010

MEDIA RELEASE

Hot cities

If you thought our cities are getting warmer, you're right.

Bureau of Meteorology researchers have found that daytime temperatures in our cities are warming more rapidly than those of the surrounding countryside and that this is due to the cities themselves.

Bureau climate scientist, Belinda Campbell, said "we've known for a while that city night time temperatures have been warmer because the heat's retained after sunset just that much longer than the countryside, and that city daytime temperatures have been warming too."

"But what we didn't know was whether city day time temperatures were also warmer because of the urbanisation or whether it was due to the overall warming of the planet associated with the enhanced greenhouse effect."

"We can now confidently say that the reason our cities are warmer and warming faster than the surrounding countryside during the day is because of the urbanisation, the fact that all those offices, houses and factories absorb the heat and retain it a little bit longer," Ms Campbell said.

Rest HERE and conference abstract HERE

We wonder how Laverton faired?

UPDATE: UHI at Laverton - Minister responds

Top: population growth around Laverton based on ABS statistics. 

Bottom: Laverton Mean temperature based on BOM records  

Note sharp rise in both after 2000

(click to enlarge)

We raised the issue of the Urban Heat Island effect at Laverton in a letter to the Hon. Peter Garrett Minister for Environmental Protection, Heritage and the Arts, following ABC's belated discovery of UHI. Part of Hon. P Garrett's brief is looking after Australia's Bureau of Meteorology (BOM). The content of the letter can be viewed at the Watts Up With That post titled "More weather BoM’s in Oz". The temperature data at Laverton was also discussed in this Watts Up With That post "Before one has data". Today we received a response from the Minister written on his behalf by Dr Greg Ayers Director of the Bureau of Meteorology.

The letter is shown below. Click on the image for a larger version.

BOM indicates it last looked at Laverton in 2003. Based on the graphs above we suggest BOM should complete its review of Laverton as a matter of urgency. In the meantime we have requested BOM supply the names of surrounding rural stations used in its comparison so that an independent audit of UHI at Laverton can be undertaken. As BOM appears to have closed most of its rural stations surrounding Laverton and as many of the remaining stations have their own data quality problems (see below) we are left to wonder which sites BOM have left to compare Laverton with? 

The published literature appears to disagree with BOM's letter. Torok et al demonstrate:

1. Based on the relationship between UHI and population in this paper UHI at Laverton can be estimated at about 5.18 degrees over rural temperatures.
2. Torok  et al state "It is possible that the measured Melbourne UHI is a slight underestimate, as measurements across the urban-rural boundary were not continued far into the rural area." 

Torok, Morris, Skinner, and Plummer. “Urban heat island features of southeast Australian towns”  in  Australian Meteorological Magazine  50 (2001): 1-13)

As stated it clear the hard yards have not been done in measuring UHI at this site. BOM may want to look at its method of measuring UHI given the rapid growth around Laverton. 

More on this as it arises.

By the way Ken Stewart has recently completed an audit of BOM's High Quality Temperature Site Network, finding that:

• Problems with the High Quality data include:
• It has been subjectively and manually adjusted.
• The methodology used is not uniformly followed, or else is not as described.
• Urban sites, sites with poor comparative data, and sites with short records have been included.
• Large quantities of data are not available, and have been filled in with estimates.
• The adjustments are not equally positive and negative, and have produced a major impact on the Australian temperature record.
• The adjustments produce a trend in mean temperatures that is roughly a quarter of a degree Celsius greater than the raw data does.
• The warming bias in the temperature trend is over 40%, and in the anomaly trend is 50%.
• The trend published by BOM is 66.67% greater than that of the raw data.
• The High Quality data does NOT give an accurate record of Australian temperatures over the last 100 years.

See Ken's post  The Australian Temperature Record- Part 8: The Big Picture

Missing News: Urban Heat Island effect at Laverton, VICTORIA

ABC finally discovers the Urban Heat Island Effect with this story that reports on a paper that uses climate models to forecast alarming future urban temperatures.

The UHI effect has a significant impact on temperature and is derived from man-made changes in the energy balance in urban centres, to the point where sites that are affected are not useful for monitoring climate unless they are adjusted. The bias arises as a direct result of two different but associated processes. The first involves direct heating of the air surrounding an instrument from vehicle emissions, air-conditioning, industry etc. The second involves land surface changes that include changes over time due to human influence in albedo (change in vegetation for instance), thermal aerodynamic properties (buildings that change air flow around a site), hydrology (affects evaporation) and morphology of the surface.

You'd think that Australia's Bureau of Meteorology would take steps to ensure station weather stations potentially affected by UHI were removed from its climate reference network. It seems that based on a letter featured on Watts up with that, that BOM has ignored investigating potential UHI for at least one of these "High Quality" stations. How many others are out there? Will the ABC investigate?

Note that as of 12:20pm 24 June 2010 AEST the post at WUWT shows a photo of Laverton Western Australia. The weather station in question is Laverton Victoria, not Western Australia. The station is indicated by the place mark in the image below (upper middle). While the local siting may be reasonable, the affect of encroaching development remains un-accounted for.
(Update: WUWT provide a corection and more analysis of Laverton data HERE)

Figure below is a comparison of temperature as recorded at BOM's Laverton station and population growth for the Laverton area. The recent increase in temperature trends appears linked to a rapid increase in population.

Out of interest the Mean Max temp for Laverton Western Australia appears to have dropped since the late 1970s. You can compare temperature data at BOM's climate data site:
http://www.bom.gov.au/climate/data/index.shtml

Laverton WA Station ID 12045 covers 1900-1970-mean max temp over this period is about 27.45 C.
Laverton AERO Station ID 12305 covers 1990-2010 with a mean temp of 26.8 C.  Gross cooling of about 0.65 C - WUWT!