Scientists: Temperature Data Contamination Accounts For 33% – 75% Of Modern Warming
Urban heat from paved roads, buildings, and machinery can artificially inflate temperatures substantially above measured temperatures from non-urban areas. This introduces a significant non-climatic warming bias into long-term records.
Heat from an urban (or highly populated) environment can artificially raise temperatures by as much as 3°C to 10°C relative to nearby rural locations. This is true even for villages in the Arctic.
Imhoff et al., 2010 On a yearly average, urban areas are substantially warmer than the non-urban fringe by 2.9°C
This article presents the results of a study of the urban heat island (UHI) in the city of Apatity [Russian Arctic] during winter that were obtained according to the data of field meteorological measurements and satellite images. Calculations of the surface layer temperature have been made based on the surface temperature data obtained from satellite images. … As a result of the analysis of temperature fields, an intensive heat island (up to 3.2°C) has been identified.
Kim, 1992 The results indicate that urban heating is attributable to a large excess in heat from the rapidly heating urban surfaces consisting of buildings, asphalt, bare-soil and short grasses. In summer, the symptoms of diurnal heating begin to appear by mid-morning and can be about 10°C warmer than nearby woodlands.
Artificial Warming From Urban Bias A ‘Substantial Portion’ Of Overall Global Trend
Scientists were at one time concerned that artificial warming biases from expanding urbanization might contaminate the measured surface temperature record.
As recently as the late 1980s it was concluded that the “artificial warming” from urban heat could add an extraneous 0.1°C to 0.4°C of warming per decade in some regions and that the non-climatic warming attributed to urbanization exceeds the observed overall long-term trends after the 1950s. In other words, a substantial portion of the warming since the mid-20th century could be attributed to artificial heat.
Karl and Quayle, 1988 Karl et al., 1988) has shown that at some ‘sun belt’ cities in the West, the rise of temperature that can be attributed to the urban heat island is as much as 0.3 to 0.4°C per decade. In the East, the rise is over 0.1°C per decade. … The artificial warming in the primary station network, relative to the climate division data, is nearly 0.17°C over the past 34 years [1950s]. Such trends are at least as large as any of the observed trends over the United States (Karl, 1988) or the globe (Jones and Wigley, 1987).
Karl and Jones, 1989 Results indicate that in the United States the two global land-based temperature data sets have an urban bias between +0.1°C and +0.4°C over the twentieth century (1901-84). … The magnitude of this urban bias in two global, land-based data sets was found to be a substantial portion of the overall trend of global and regional temperatures.
Modern Temps Rising 0.05°C – 0.12°C/Decade…Urban Heat Bias Rising Faster
The IPCC considers the year 1750 as the starting point for the radiative anthropogenic influence on climate, due principally to fossil fuel burning and concomitant CO2 emissions. Since 1850, CO2 concentrations have risen from 285 ppm to 400 ppm. During these ~165 years, the IPCC has concluded that surface temperatures have warmed by 0.78°C. This is a warming rate of only 0.05°C per decade for 1850-2012 — which happens to be the same rate of warming over the 1998-2012 period. Temperatures are rising at a rate of 0.12°C per decade during 1951-2012.
IPCC AR5 (2013): The globally averaged combined land and ocean surface temperature data as calculated by a linear trend, show a warming of 0.85°C over the period 1880 to 2012 when multiple independently produced datasets exist. The total increase between the average of the 1850–1900 period and the 2003–2012 period is 0.78 °C, based on the single longest dataset available 4 (see Figure SPM.1). … [T]he rate of warming over the past 15 years (1998–2012; 0.05 °C per decade), which begins with a strong El Niño, is smaller than the rate calculated since 1951 (1951–2012; 0.12 °C per decade).
As suggested above, (a) non-climatic urban heating may artificially add 0.1°C per decade (or more) to the temperature record; (b) the overall surface temperature record is only rising at a rate of +0.05°C to +0.12°C per decade; therefore, (c) this would imply that all or nearly all the warming since 1850 or 1950 may be attributed to rapidly expanding urbanization and measurement bias, not climate change.
4 New Papers Highlight Artificial Warming Bias, Adjustments
Four new studies can be added to a large collection of scientific papers documenting an accelerating artificial warming bias.
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