The capacity of cities to act on climate change mitigation is essential to fulfil the Paris Agreement target. In order to do so, cities should establish an effective climate policy which requires, as a first step, a complete greenhouse gas (GHG) emissions inventory. The accurate city-scale GHG inventory enables cities to develop, implement and track climate solution measures, mainly those related to transportation. The compilation of a city-scale GHG inventory requires a standardized method and up-to-date activity data. This systematic review critically examines 40 articles over the past 20 years to (1) identify city-scale GHG inventory methods being applied worldwide, (2) evaluate how these methods are evolving, (3) elaborate how emissions from transport sector are being estimated, and ( 4) determine what data types and sources of transport-related data are being used. The review was limited to articles that addressed the process of compilation of a GHG inventory. The results demonstrate that city-scale GHG inventory methods evolved from the Intergovernmental Panel on Climate Change (IPCC) Guidelines to a variety of GHG accounting methods that offer levels of complexity to estimate city-scale emissions. Although GHG inventory methods for city-scale have advanced over the years, almost one third of the articles reviewed were focused on the proposal of a GHG inventory framework, adjusting current methods to each city's reality or proposing new ones. The majority of the cities analysed lack local transport-related data to measure GHG emissions based on the bottom-up approach. Yet, more than 40% of the articles managed to deliver the bottom-up inventory using a diversity of data types and sources. This review shows that there is still a path to achieve a globally compatible method. This would require a joint effort between researchers and city authorities to make international protocols more compliant to each city's data availability along with the improvement of cities data collection.

As of June 2017, 150 countries have ratified the Paris Climate Agreement. This agreement calls for, among other things, strong reductions in CO 2 emissions by 2030 and beyond. This paper reviews the Nationally Determined Contribution (NDCs) plans of six Association of Southeast Asian Nations (ASEAN) countries and compares their current and projected future CO 2 levels across sectors, and their stated targets in the context of their economic and demographic situations. This comparison reveals wide variations in the types of targets, with the "ambition" level changing as the perspective changes from total CO 2 to CO 2 /capita and per unit gross domestic product (GDP). We also review national plans as stated in NDCs and find that while there are many types of policies listed, few are quantified and no attempts are made to score individual or groups of policies for their likelihood in achieving stated targets. We conclude that more analysis is needed to better understand the possible impacts of current policies and plans on CO 2 emissions, and whether current plans are adequate to hit targets. Considerations on better aligning targets are also provided.

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Decarbonizing transportation in emerging economies will be one of the key challenges in global climate change mitigation efforts. In this paper, pathways are developed towards achieving a 1.5° degree scenario for land-transport for four emerging economies (Brazil, India, Kenya and Vietnam). This aims to highlight the key opportunities and challenges for low-carbon transport in countries with rapidly growing mobility demand. The main focus of this paper is to reconcile actual and required emission reduction targets and develop plausible pathways to achieve these targets. The paper also identifies potential strategies and measures for these countries to follow these pathways. The analysis considers the contributions of "avoid" (cutting travel growth), "shift" (to lower CO2 modes) and "improve" (vehicle and fuel CO2 characteristics) interventions to decarbonisation scenarios. These scenarios aim to inform renewed Nationally Determined Contributions and shed light on the feasibility of deep decarbonisation pathways that would be in line with the Paris Agreement. Results from this study show that achieving 1.5DS would require dramatic changes in travel patterns, technology and fuels, and major intensification of current policy approaches. Decarbonization solutions will need to include greater use and investment of efficient modes, major shifts toward near-zero carbon fuels such as clean electricity, systems integration, modal shift and urban planning solutions. Although the socio-economic situations and national transport systems differ between the selected countries, some fairly similar strategies appear likely to be core to the mitigation effort, such as rapid growth in light-and heavy-duty vehicle electrification and investments in public transit systems.