Guest essay by Paul Homewood
I ran a post earlier about UHI in South Korea. A study by two Korean scientists found that over half of the warming reported in Korea since 1954 was a result of UHI. In many cities, the effect of UHI was to add more than a degree to temperatures over the period they had analysed, 1954-2008.
I was already aware that GISS tended to allow only about 0.2C for UHI in other cities I had examined previously, so I was curious to find out what allowance they were making in Korea.
There are ten stations currently in use in South Korea, which are in the GHCN database, that in turn is used by GISS. These are all listed in Appendix A.
First, a brief explanatory note. GHCN collect temperature data, which they then put through a homogenisation algorithm, which may result in adjustments. These adjusted numbers are then used by GISS, who then put then through their own homogenisation process, which is designed to make allowance for UHI effects – more detail here.
The figures below compare the raw data with the “after GISS adjustment” data, so the resulting differences are due to a combination of both GHCN and GISS adjustments.
The study only listed Pohang, Seoul and Mokpo in the abstract. The other cities, marked as n/a, may be in the full paper, but it is paywalled!
The following points are noteworthy:-
- Out of the ten stations, only one, Ullungdo, is rural.
- The typical adjustment from raw to “UHI adjusted” is much less than the study found.
- The average adjustment for the nine urban sites is a paltry 0.05C
- There is, incredibly, no adjustment at all for Seoul, while the adjustments at Mokpo and Cheju have actually added to the warming trend.
- At the only rural station, Ullungdo, the GHCN adjustment has reduced the 1954 temperature, thus adding to the warming trend.
- It is often claimed that station moves out of city centres and into airports can offset UHI. This is not the case in South Korea, as only one site, Chunchon, is listed as an airport site on the GISS station list.
Since the 1940’s, there has been a massive increase in urbanisation in South Korea. The country’s population has risen from 20 million in 1949, to over 50 million today. Between 1945 and 1985, it has been estimated that the urban population increased from 14% to 65% of the total population, which would imply more than a tenfold increase in actual numbers.
On top of that, industrialisation and technology have made these cities unrecognisable from 50 years ago. It is inconceivable that these factors would not have created a significant increase in UHI effect over the years.
Which all raises the question, why are GISS allowing for so little? With only one rural station, their temperature calculations for the whole country are heavily skewed towards these urban sites, and therefore must be viewed with considerable scepticism.
What is true for South Korea is also true for much of the region, as mass urbanisation and industrialisation have similarly affected many other countries there, such as China. Has correct allowance been made for UHI in these?
Meanwhile Richard Muller tells us
Urban areas are heavily overrepresented in the siting of temperature stations: less than 1% of the globe is urban but 27% of the Global Historical Climatology Network Monthly (GHCN-M) stations are located in cities with a population greater than 50,000.
APPENDIX A – GISS TEMPERATURE RECORDS FOR SOUTH KOREA
1954 to 2008
1954 to 2008
After GISS Adj
|Chunchon AP *||141||0.71||0.58||0.13||n/a|
* Records for Chunchon and Taejon begin in 1967 and 1969 respectively
1) Raw temperature data
2) GISS adjusted data
3) UHI Study by Kim & Kim