Read here. It's become common knowledge that the UN's IPCC objective is not one of impartial, scientific analysis of climate change but instead one biased towards political governance and economic control goals. As a result, significant, non-CO2 impacts on global warming are either ignored or trivialized by the IPCC. The urban heat island (UHI) effect on temperature records is one such impact that the IPCC keeps trying to minimize but the actual science keeps refuting the IPCC's agenda-driven science.
Yang et al. published an extensive study on the impact of UHI on China's warming and discovered that over 40% of the increase could be explained by the UHI effect in some urban areas. This study represents additional empirical evidence that significant global warming is not exclusively due to the IPCC's politically correct causation, CO2 emissions.
"Monthly mean surface air temperature data from 463 meteorological stations, including those from the 1981–2007 ordinary and national basic reference surface stations in east China and from the National Centers for Environmental Prediction and National Center for Atmospheric Research (NCEP/NCAR) Reanalysis, are used to investigate the effect of rapid urbanization on temperature change...The trends of urban heat island (UHI) effects...are generally consistent and indicate that rapid urbanization has a significant influence on surface warming over east China. Overall, UHI effects contribute 24.2% to regional average warming trends. The strongest effect of urbanization on annual mean surface air temperature trends occurs over the metropolis and large city stations, with corresponding contributions of about 44% and 35% to total warming, respectively. The UHI trends are 0.398°C and 0.26°C decade. [Xuchao Yang, Yiling Hou, Baode Chen 2011: Journal of Geophysical Research]