This paper investigates the effects of urban heat island (UHI) on outdoor lighting systems in terms of GHG emissions: a novel methodology is proposed to assess the carbon footprint (CF) change of lighting services in built areas caused by UHI-induced Delta T with particular focus on the evaluation of the energy consumption. The methodology can be applied also to other activities affected by the UHI, such as HVAC and transport systems. In particular, Delta CF was introduced by a two-fold approach: the quantification of the CF change due to UHI (as difference between CF in an UHI-affected case and CF for an UHI-less case) and the CF change produced by a 1 degrees C temperature change. A focus on LED lamps was developed: the lifetime of LEDs exponentially decreases with increasing temperature and the luminous flux exponentially decays with operation time. UHI (i.e. the increase in ambient temperature) affects the lifetime and the luminous flux of lamps producing higher energy consumption and higher replacement rates. Results showed that a positive AT due to UHI produces a positive ACE, which also becomes economically relevant in long-term scenarios. A case study was analyzed by applying the proposed methodology to Rome outdoor public lighting. (C) 2015 Elsevier B.V. All rights reserved.