Abstract
AbstractThere have long been arguments about the impact of urbanization on local meteorological observations. This letter reviews up-to-date studies of the urbanization-related warming in the observed land surface air temperature series in China. Many previous studies have suggested that, over the past few decades, the local warming due to urbanization could have been about 0.1 °C/10 yr, or even larger. However, based on recently developed homogenized temperature records, the estimated urban bias is smaller. Major uncertainties arise from either the data quality or the techniques used to estimate the urbanization effect. A key example is the ‘observation-minus-reanalysis’ method, which tends to overestimate the urban signal in this region, partly due to systematic bias in the multi-decadal variability of surface air temperature in the reanalysis data. It is expected that improved numerical modeling with high-resolution information regarding the changing land surface in the region will help to further unde...
Highlights
Urbanization is a human activity that clearly modifies the earth system
It is expected that improved numerical modeling with high-resolution information regarding the changing land surface in the region will help to further understand and quantify the effect of urbanization in local temperature records
A typical example is the estimation of the urbanization effect at Beijing Observatory: an early analysis based on the original temperature observations in the region estimated that the contribution of urbanization to the recorded warming trend during recent decades was 80% (Ren et al 2007); having adjusted the biases in the temperature series at Beijing due to two major relocations, Yan et al (2010) estimated the urbanization-related warming to be about 40% of the observed warming trend; and by using a more complete homogenized dataset for the region, Wang et al (2013a) estimated that the urban warming contribution for Beijing was even less than 20%
Summary
Urbanization is a human activity that clearly modifies the earth system. Involving artificial changes to the land surface and growing energy consumption, urbanization affects the surface energy budget and land–atmosphere interaction, resulting in the ‘urban heat island’ (UHI) effect (Oke 1982; Arnfield 2003; Collier 2006), among a few other well-known effects. The present letter focuses on the influence of the long-term evolution of the UHI effect on station temperature records. Peterson (2003) found ‘no significant urbanization effect’ in the regional mean temperature series, based on homogenized data. Wang, Zeng, and Karl (1990) suggested that, since the late 1970s, the rate of urban warming at urban stations in China has exceeded 0.1 °C/10 yr. Portman (1993) suggested that urban stations in North China experienced an urban-induced warming trend of 0.15–0.26 °C/30 yr during 1954–1983. Based on a homogenized data-set of annual mean surface air temperature, Li et al (2004) assessed the urbanization effect in temperature records in China and concluded that the regional mean urbanization effect is less than 0.012 °C/10 yr for the period 1954–2001.
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