Hansen tells us that 4C UHI is insignificant, in comparison to the 0.4C anomaly of 2012.
NEW YORK CITY’S HEAT ISLAND.
(Rosenthal et al. 2003; Gaffin et al. 2008), and the heat island signal, measured as the difference between the urban core and the surrounding rural surface air temperature readings taken at National Weather Service (NWS) stations, averages ~4°C on summer nights (Kirkpatrick and Shulman 1987; Gedzelman et al. 2003; Gaffin et al. 2008). The greatest temperature differences typically are sustained between midnight and 0500 Eastern Standard Time (EST; Gaffin et al. 2008).
Surface air temperature readings from these stations show that the city was several degrees warmer than the suburbs, and up to 8°C warmer than rural areas within 100 km of the city, with conditions that had been sustained throughout the previous night.