My Comment On The New Paper “Urban Heat Island Effects On Estimates Of Observed Climate Change” By David E. Parker

There is a new paper by David Parker

Parker, David E. , 2010: Urban heat island effects on estimates of observed climate change. Climate  Change 2010 1 123–133

The abstract reads

“Urban heat islands are a result of the physical properties of buildings and other structures, and the emission of heat by human activities. They are most pronounced on clear, calm nights; their strength depends also on the background geography and climate, and there are often cool islands in parks and less-developed areas. Some old city centers no longer show warming trends relative to rural neighbourhoods, because urban development has stabilised. This article reviews the effects that urban heat islands may have on estimates of global near-surface temperature trends. These effects have been reduced by avoiding or adjusting urban temperature measurements. Comparisons of windy weather with calm weather air temperature trends for a worldwide set of observing sites suggest that global near-surface temperature trends have not been greatly affected by urban warming trends; this is supported by comparisons with marine surface temperatures. The use of dynamical-model-based reanalyses to estimate urban influences has been hindered by the heterogeneity of the data input to the reanalyses and by biases in the models. However, improvements in reanalyses are increasing their utility for assessing the surface air temperature record. Highresolution climate models and data on changing land use offer potential for future assessment of worldwide urban warming influences. The latest assessments of the likely magnitude of the residual urban trend in available global near-surface temperature records are summarized, along with the uncertainties of these residual trends.”

The paper, however, has serious flaws. First, the paper contradicts itself in the conclusion where Parker writes

“Nonetheless, city-dwellers experience urban warming superimposed on the regional manifestation of global warming. Increased vegetation and/or reflective roofing have been proposed as means to mitigate urban heat islands: see for example Chicago at http://www.globalchange.gov/images/cir/pdf/midwest. pdf.”

You cannot have it both ways. The trends in the rural and urban temperatures cannot be essentially the same but at the same time recognize that the details of the change in the urban landscape over time alter the warming rate!

A second serious issue is that this paper  neglects papers that document remaining problems and issues with the surface temperature record. These include those summarized in

Pielke Sr., R.A., C. Davey, D. Niyogi, S. Fall, J. Steinweg-Woods, K. Hubbard, X. Lin, M. Cai, Y.-K. Lim, H. Li, J. Nielsen-Gammon, K. Gallo, R. Hale, R. Mahmood, S. Foster, R.T. McNider, and P. Blanken, 2007: Unresolved issues with the assessment of multi-decadal global land surface temperature trends. J. Geophys. Res., 112, D24S08, doi:10.1029/2006JD008229.

The Parker 2010 paper does not even reference the Comment/Reply that he had on this paper; i.e.

Parker, D. E., P. Jones, T. C. Peterson, and J. Kennedy, 2009: Comment on Unresolved issues with the assessment of multidecadal global land surface temperature trends by Roger A. Pielke Sr. et al.,J. Geophys. Res., 114, D05104, doi:10.1029/2008JD010450

Pielke Sr., R.A., C. Davey, D. Niyogi, S. Fall, J. Steinweg-Woods, K. Hubbard, X. Lin, M. Cai, Y.-K. Lim, H. Li, J. Nielsen-Gammon, K. Gallo, R. Hale, R. Mahmood, S. Foster, R.T. McNider, and P. Blanken, 2009: Reply to comment by David E. Parker, Phil Jones, Thomas C. Peterson, and John Kennedy on “Unresolved issues with the assessment of multi-decadal global land surface temperature trends”. J. Geophys. Res., 114, D05105, doi:10.1029/2008JD010938.

As we presented in our weblog post

Reply By Pielke Et Al To The Comment By Parker Et Al. On Our 2007 JGR paper “Unresolved Issues With The Assessment Of Multi-Decadal Global Land Surface Temperature Trends”

the referees agreed with us on our Reply.

Parker is presenting an old perspective in a 2010 format. The paper is misleading readers that this is actually new research and is up-to-date with the current issues in the multi-decadal surface temperature record.

The recent paper

McCarthy , M. P., M. J. Best, and R. A. Betts (2010), Climate change in cities due to global warming and urban effects, Geophys. Res. Lett., 37, L09705, doi:10.1029/2010GL042845.

affirms that urban areas have different long term trends. The introduction of that paper reads

“Urban micro‐climates have long been recognised [Howard, 1833; Oke, 1987], and in the monitoring and detection of global climate change climatologists have gone to great lengths to remove or minimise the potential influence of urbanisation on the historical climate record [Parker, 2010]. This is vital for trying to detect warming trends of the order
0.1°C per decade. However, observational evidence shows trends in urban heat islands in some locations of a similar
magnitude or greater than that from greenhouse gas forced climate change [Stone, 2007; Fujibe, 2009] and further urbanisation of the global population is expected through the 21st century [United Nations, 2007]. The latest report from the Intergovernmental Panel on Climate Change recognises that urbanisation is missing from climate model projections [Christensen et al., 2007], and the potential for differential rates of radiatively‐forced climate change in urban compared to rural areas has received little attention.”

The Parker (2010) paper, therefore, perpetuates an inaccurate summary of the current understanding of the role of urbanization in long term surface temperature trends.

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