Urban Heat Island Influence Inadequately Considered in Climate Research

By Dr. Tim Ball – Re-Blogged From WUWT

The Intergovernmental Panel on Climate Change (IPCC) deliberately limited climate science to focus on CO2 and temperature. The United Nations Framework Convention on Climate Change (UNFCCC) directed them only to consider human causes of climate change. They used this to narrow the focus of all variables that create the climate and thus eliminate major variables that cause climate change. A major example is the so-called greenhouse gases (GHG). Three of them account for almost 100% of the total; by volume, they are Water vapor (H2O) (95%), Carbon dioxide (CO2) (4%) and Methane (CH4) (0.36%). There are no accurate measures of any of these regarding the amount actually in the atmosphere or the changes in input and output from natural sources over any period.

All agencies agree that Water vapor is by far the largest and most important, but it gets virtually no attention. I do not intend to argue about the various attempts to downplay its importance. They are all proof of how little we know because each manipulator achieves different results. The IPCC admits humans add H2O to the atmosphere. However, they consider the amount so small relative to the atmospheric total and therefore of no consequence in their calculations. The problem is the effect of water vapor as a GHG is so large that it is probable that even a 2% variation could explain a great deal of the effect of CO2 and indeed all the effect of human-produced CO2. Proving this is complicated by the fact that H2O and CO2 overlap significantly on the Electromagnetic Spectrum.


The second significant IPCC bias is on temperature and specifically global warming. The planet is named Earth but should be Water. There is no life without it. Vladimir Koppen recognized its importance in climate. The first operation in his climate classification system is to identify those climates with insufficient rainfall to support plants.

The global temperature data is entirely inadequate to determine anything other than the data is inadequate. It only covers 15% of the surface and less than 1% above the surface. The US temperature record is probably the best in coverage and instrumentation, yet the Watts surface station analysis found only 7.9% with accuracy better than 1°C.


It is multiple times worse for precipitation data. Distribution is almost infinitely variable with large differences occurring in a matter of meters. It is problematic even with vertical fall, but the wind makes that rare, and instrument design the most difficult of any at the weather station. That is for rainfall; accurate snowfall measurement is far more difficult.

On a global basis, the network is inadequate over vast areas. A 2006 study of monsoons in Africa concluded,

Africa’s network of 1152 weather watch stations, which provide real-time data and supply international climate archives, is just one-eighth the minimum density recommended by the World Meteorological Organization (WMO). Furthermore, the stations that do exist often fail to report.

The Urban Heat Island Effect (UHIE) contaminates the surface temperature data. The first study to measure the UHIE was by Tom Chandler and detailed in the 1965 book The Climate of London. The work triggered heat island studies in many urban areas, including the ones I participated in for Winnipeg in the late 1960s

Urban Heat Island profile Image from Lawrence Berkeley Labs

A simple schematic of an Urban Heat Island Dome

After establishing its existence, adjustments to many temperature records began. They still make them, but it is a very imprecise adjustment. It is a major cause of the variations between regional and global averages by different groups. You can influence the outcome you desire by choosing the amount of adjustment made. Urban areas are almost all growing, so, presumably, there is a changing adjustment. This is problematic and when combined with the paucity of weather stations, underscores the difficulty of establishing a global temperature.

Precipitation records are even less adequate. In a way, this makes my next point academic. (Notice how that means it is irrelevant to the real world.) In 1967, my thesis supervisor, Dr. Bruce Atkinson, published work based on his doctoral thesis titled, A Preliminary Examination of the Possible Effect of London’s Urban Area on the Distribution of Thunder Rainfall 1951-60.” The argument is that precipitation potential is enhanced in the urban environment by

  • more rapid evaporation,
  • an increased volume of evaporated moisture,
  • increased condensation nuclei from the production of dust particles,
  • upward transport of the particles in the convective cell that is the urban heat island,
  • upward transport and cooling in the urban cell,
  • increased instability of adiabats as they travel over the outside of the urban dome.

In 1968, support for this urban influence on precipitation appeared in a report of the La Porte weather anomaly. The city of La Porte is in the county of LaPorte, Indiana. While plotting precipitation patterns in the region, Stanley Changnon noticed a significant increase, (30 to 40%) in precipitation levels after 1925. He attributed the increase to the growth of the urban area of Chicago and particularly the construction of steel mills and other heavy industries.

The La Porte claim engendered discussion and disagreements, notwithstanding Atkinson’s research in London. Years later the American Meteorological Society (AMS) reported that,

Earlier research has used ground-based instruments, including rain gauge networks, ground-based radar, or model simulations, to show that urban heat islands can impact local rainfall around cities like St. Louis, Chicago, Mexico City and Atlanta.

NASA resolved the disagreement in 2002 when Dr. J. Marshall Shepherd and colleagues published the results of a study using data from the Tropical Rainfall Measuring Mission (TRMM) satellite. They found that,

…mean monthly rainfall rates within 30-60 kilometers (18 to 36 miles) downwind of the cities were, on average, about 28 percent greater than the upwind region. In some cities, the downwind area exhibited increases as high as 51 percent.

I was unable to find any reference to adjustments to precipitation data based on these findings. The IPCC AR5 Physical Science Report appears to confirm the lack of adjustments. However, much of what they report appears to indicate the data is affected by the UHIE. In their general observations about precipitation they wrote,

Confidence in precipitation change averaged over global land areas is low prior to 1951 and medium afterwards because of insufficient data, particularly in the earlier part of the record (for an overview of observed and projected changes in the global water cycle see TFE.1). Further, when virtually all the land area is filled in using a reconstruction method, the resulting time series shows little change in land- based precipitation since 1901. NH mid-latitude land areas do show a likely overall increase in precipitation (medium confidence prior to 1951, but high confidence afterwards). For other latitudes area-averaged long-term positive or negative trends have low confidence (TFE.1, Figure 1). {2.5.1}

In their more detailed analysis. they wrote,

It is likely that since about 1950 the number of heavy precipitation events over land has increased in more regions than it has decreased. Confidence is highest for North America and Europe where there have been likely increases in either the frequency or intensity of heavy precipitation with some seasonal and regional variations. It is very likely that there have been trends towards heavier precipitation events in central North America.

The areas they identify are where the weather station network is inadequate, but the best globally. The NASA study also notes that,

By showing how space-borne platforms can be used to identify rainfall changes linked to cities and urban sprawl, the research may help land managers and engineers design better drainage systems, plan land-use, and identify the best areas for agriculture. Also, it highlights the need for scientists to account for impacts of urbanization when they design computer models that forecast the weather or predict regional climates.

There is some crude accommodation for the temperature impact of the urban heat island. All it does is create confusion because the overall database is inadequate and the variations due to the effect even more uncertain. In reality, a temperature error of even 2 or 3°C is of little consequence. However, 30 and 40% errors in precipitation are of great consequence for all the managers and engineers planning the list NASA identifies.

It is time to shut down the IPCC and its politically biased climate claims that focus on temperature and CO2 while ignoring or distorting far more important variables and factors.



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