Climate Change Images Global Warming: Man or Myth?
Fiction: Surface Temperatures are Unreliable (UHI)

Fiction: Surface Temperatures are Unreliable (UHI)

The claim: Due to the Urban Heat Island Effect (UHI), temperatures are being warmed by thermometer placement and not by climate change.

Due to urbanization, some skeptics believe that the warming trend observed in the U.S. and other industrialized countries may be due in large part to the Urban Heat Island Effect. Anthony Watts, a weather forecaster, decided to pursue this claim. He launched a Website called and asked volunteers to canvass the countryside looking for weather observation stations that may be influenced by poor thermometer site placement. As of July, 2009, his organization claims to have observed and rated 82% of the NOAA 1218 USHCN stations. Of these, Watts claims that only 70 stations are considered good or best according to NOAA’s Climate Reference Network Site Handbook. The Heartland Institute has published his findings in a document titled: Is the U.S. temperature Record Reliable? Anything published by the ExxonMobil-funded Heartland Institute should be immediately suspicious. (See: Global Warming Denial Machine: Heartland Institute.)

NOAA Climate Services, in a brief titled: Talking Points related to concerns about whether the U.S. temperature record is reliable (2009) compared Watts' 70 good or best stations to the full set of 1218 stations. The results appear below in Figure 1.

Watts' 70 Best Stations Vs. All 1218 Stations
Figure 1: Watts' 70 best stations (blue) vs. all 1218 NOAA stations (red)

It is clear that UHI has not influenced the US temperature trend since 1950. Essentially the rising tide of global warming has "lifted all boats."

Compare figures 2 and 3 (Sato, 2009) which show the GISS global temperature anomalies for surface stations only and for surface stations plus satellite-derived ocean temperatures, respectively. There certainly is no UHI over the oceans and yet these two have similar trends in temperature!

Surface Stations Only
Figure 2: GISS data using only surface stations
GISS Data Using Land and Ocean
Figure 3: GISS data using land and ocean data

As discussed in Global Cooling, UAH and RSS are two other sources for global temperature data but these two do not use surface station data. Instead, they use satellite-derived lower tropospheric temperature data. (Note: both GISS and HadCRU use surface station data and satellite derived data.) It is important to understand that RSS and UAH do NOT use thermometers so there cannot be any UHI effect! Figure 4 (Rohde, 2009) shows the global temperatures for UAH (red), RSS (green), and direct surface measurements (blue).

UAH, RSS and Direct Measurements
Figure 4: global temperatures for UAH (red), RSS (green), and direct surface measurements (blue)

When satellite data are used, the trend is almost identical to that of surface measurements using thermometers. There is no detectable UHI effect.

Other research shows the same conclusion that there is little to no UHI effect:

Despite the relatively small effects of UHI, global temperature measurements by HadCRU and GISS do adjust their measurements to account for UHI. The technique is discussed in Hanson, et al. (2001), and in a NASA GISS press release.

The U.S. Climate Reference Network (USCRN) initial deployment of 114 stations in the continental U.S. was completed in September 2008. These stations are designed to yield high quality and continuous climate observations for highly stable sites for the next 50 years, tracing the national trends in temperature and precipitation over this time. All of these stations are in very remote locations.

This is what scientists do. If there is a suspected data issue, they go to great lengths to fix the problem. There is no hidden agenda nor negligence although Anthony Watts and other skeptics would have us believe so.

More recently (January 2010), Anthony Watts and Joseph D'Aleo submitted an unpeer-reviewed document titled: Surface Temperature Records: Policy Driven Deception? to the Science and Public Policy Institute (SPPI) that claims the surface temperature data has been altered and is essentially fraudulent. These are quite extraordinary claims! As described at, "the Science and Public Policy Institute (SPPI) is a global warming skeptics group which appears to primarily be the work of Robert Ferguson, its President; its website draws heavily on papers written by Christopher Monckton."

Once again, there is no merit to Watts' claims and Tamino at Open Mind completely shreds their claims by actually anlayzing data correctly. In a subsequent post by Tamino, the claim by Watts and D'Aleo that there is No Warming Trend In The 351-Year Central England Temperature Record is shown to be false. Essentially, Watts and D'Aleo began with a conclusion and then worked backward to try to fit data to support their conclusion. Of course, the scientific method is to have the data drive the conclusion and not the reverse.

Watts Up with Watts?Peter Sinclair's Climate Crock of the Week: Watts Up with Watts?
Watch this video to learn about Anthony Watts and his project...
Urban Heat Island EffectPeter Sinclair's Climate Crock of the Week: The "Urban Heat Island" Crock
and this video.

A superb analysis by Ned at Skeptical Science July, 2010: Assessing global surface temperature reconstructions

Scott A. Mandia
Professor - Physical Sciences
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Last updated: 07/24/10