The economic structure of a city evolves as the city develops, resulting in a change in energy consumption. This paper presents a historical review of Hong Kong's economic development and energy consumption from 1970 to 2015. Based on the official data from the Hong Kong government, it was found that Hong Kong's gross domestic product increased from HKD 208 billion in 1970 to HKD 2398 billion in 2015 in which the contribution from the manufacturing sector peaked in 1985. Energy consumption

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... ased by 9.3 times from 140.2 PJ in 1970 (mostly oil products) to 1298.2 PJ (including oil products, natural gas, coal, and imported electricity) in 2015. The greenhouse gas (GHG) emissions due to energy consumption were determined based on emission factors for different fuels. Results show that GHG emissions increased from 10.7 million tons (Mt) of CO 2 -equivalent in 1970 to 99.1 Mt of CO 2 -equivalent in 2015. and climate conditions [16] [17] [18] . It has been known that air pollutants such as sulfate aerosols and particulate matter can have an impact on radiative forcing, thus either warming or cooling the Earth's atmosphere system [16] , as well as visibility in cities [17, 18] . Although some previous studies explored the causal relationship between economic growth and energy consumption [19] [20] [21] [22] [23] as well the effect of climate conditions on energy consumption [24, 25] , very few of them focused on a densely populated city such as Hong Kong [24,25] and using long-term time series data [11] . Besides, very few studies, except Warren-Rhodes and Koenig [11] , explored Hong Kong's total energy consumption (local use and consumption due to outbound transportation services) using long-term time-series data. Warren-Rhodes and Koenig [11] showed that Hong Kong's CO 2 emission had risen by 250% from 1971 to 1997. Yet, no new study about Hong Kong's total CO 2 emission has been reported since Warren-Rhodes' [11] work. As Hong Kong is a special administrative region (SAR) of China-a key signatory of the Paris climate agreement-Hong Kong must determine and monitor its total energy consumption and greenhouse gas (GHG) emissions [26] . In fact, the central government of China stated clearly that the Paris climate agreement applies to Hong Kong and the Hong Kong Government had set an ambitious carbon intensity reduction target by lowering its total GHG emissions by 26-36% in 2030 using 2005 as the base year [26] . Hence, the objectives of the paper are to (i) provide a historical review of Hong Kong's energy consumption and economic development from 1970 to 2015, (ii) determine Hong Kong's GHG emissions due to energy consumption, and (iii) explore how GHG emissions are related to energy mix, population, and economic growth. The study contributes to understanding the relationships between urban socio-economic development, energy consumption, and GHG emissions. The findings can shed light to government of Hong Kong and that of other cities (including those in Mainland China) in developing appropriate energy policy and GHG mitigation plans.