• Energy Research

Electricity demand for room air conditioners (ACs) has been growing significantly in China in response to rapid economic development and mounting impacts of climate change. In this study, we use the bottom-up model approach to predict the penetration rate of room ACs in the residential building sector of China at the provincial level, with the consideration of the urban-rural heterogeneity. In addition, we assess co-benefits associated with enhanced energy efficiency improvement of AC systems and the adoption of low-global-warming-potential (low-GWP) refrigerants in AC systems. The results indicate that the stock of room ACs in China grows from 568 million units in 2015 to 997 million units in 2030 and 1.1 billion units in 2050. The annual electricity saving from switching to more efficient ACs using low-GWP refrigerants is estimated at almost 1000 TWh in 2050 when taking account of the full technical energy efficiency potential. This is equivalent to approximately 4% of the expected total energy consumption in the Chinese building sector in 2050 or the avoidance of 284 new coal-fired power plants of 500 MW each. The cumulative CO2eq mitigation associated with both the electricity savings and the substitution of high-GWP refrigerants makes up 2.6% of total business-as-usual CO2eq emissions in China over the period 2020 to 2050. The transition toward the uptake of low-GWP refrigerants is as vital as the energy efficiency improvement of new room ACs, which can help and accelerate the ultimate goal of building a low-carbon society in China.

This dataset contains data presented on the World Emissions Clock hosted by the World Data Lab. The World Emissions Clock provides trajectories of future greenhouse gas emissions until 2050 for 182 countries (and international aviation + shipping), five main sectors and up to 24 subsectors, and three different scenarios. These hypothetical scenarios are: Business as usual (BAU), where technological advancement and policy-making roughly follows past trends without major shifts. Nationally determined contributions (NDC), where countries fully implement their unconditional climate pledges as submitted to the United Nations Framework Convention on Climate Change (UNFCCC). Achieving 1.5°C, where secotral emissions within countries follow a cost-efficient pathway towards limiting global warming to 1.5° Celsius by 2100. For further information, see the Methodology section of the World Emissions Clock. Contact wec@worlddata.io for access information. The World Emissions Clock was created in a cooperation of the World Data Lab with the International Institute for Applied Systems Analysis (IIASA), the Vienna University of Economics and Business (WU Vienna), and the University of Oxford and was supported from the German Federal Ministry for Economic Cooperation and Development (BMZ), the German Agency for International Cooperation (GIZ), and the Patrick J. McGovern Foundation.

Hydrofluorocarbons (HFCs) are synthetically produced compounds primarily used for cooling purposes and with strong global warming properties. In this paper, we analyze the global abatement costs for achieving the substantial reductions in HFC consumption agreed in the Kigali Amendment (KA) of the Montreal Protocol from October 2016. We estimate that compliance with the KA is expected to remove 39 Pg CO2eq or 61% of global baseline HFC emissions over the entire period 2018–2050. The marginal cost of meeting the KA targets is expected to remain below 60 €/t CO2eq throughout the period in all world regions except for developed regions where legislation to control HFC emissions has already been in place since a few years. For the latter regions, the required HFC consumption reduction is expected to come at a marginal cost increasing steadily to between 90 and 118 €/t CO2eq in 2050. Depending on the expected rate of technological development and the extent to which envisaged electricity savings can be realized, compliance with KA is estimated attainable at a global cost ranging from a net cost-saving of 240 billion € to a net cost of 350 billion € over the entire period 2018 to 2050 and with future global electricity-savings estimated at between 0.2% and 0.7% of expected future electricity consumption.

Abstract. Following the recent Global Carbon Project (GCP) synthesis of the decadal methane (CH4) budget over 2000–2012 (Saunois et al., 2016), we analyse here the same dataset with a focus on quasi-decadal and inter-annual variability in CH4 emissions. The GCP dataset integrates results from top-down studies (exploiting atmospheric observations within an atmospheric inverse-modelling framework) and bottom-up models (including process-based models for estimating land surface emissions and atmospheric chemistry), inventories of anthropogenic emissions, and data-driven approaches. The annual global methane emissions from top-down studies, which by construction match the observed methane growth rate within their uncertainties, all show an increase in total methane emissions over the period 2000–2012, but this increase is not linear over the 13 years. Despite differences between individual studies, the mean emission anomaly of the top-down ensemble shows no significant trend in total methane emissions over the period 2000–2006, during the plateau of atmospheric methane mole fractions, and also over the period 2008–2012, during the renewed atmospheric methane increase. However, the top-down ensemble mean produces an emission shift between 2006 and 2008, leading to 22 [16–32] Tg CH4 yr−1 higher methane emissions over the period 2008–2012 compared to 2002–2006. This emission increase mostly originated from the tropics, with a smaller contribution from mid-latitudes and no significant change from boreal regions. The regional contributions remain uncertain in top-down studies. Tropical South America and South and East Asia seem to contribute the most to the emission increase in the tropics. However, these two regions have only limited atmospheric measurements and remain therefore poorly constrained. The sectorial partitioning of this emission increase between the periods 2002–2006 and 2008–2012 differs from one atmospheric inversion study to another. However, all top-down studies suggest smaller changes in fossil fuel emissions (from oil, gas, and coal industries) compared to the mean of the bottom-up inventories included in this study. This difference is partly driven by a smaller emission change in China from the top-down studies compared to the estimate in the Emission Database for Global Atmospheric Research (EDGARv4.2) inventory, which should be revised to smaller values in a near future. We apply isotopic signatures to the emission changes estimated for individual studies based on five emission sectors and find that for six individual top-down studies (out of eight) the average isotopic signature of the emission changes is not consistent with the observed change in atmospheric 13CH4. However, the partitioning in emission change derived from the ensemble mean is consistent with this isotopic constraint. At the global scale, the top-down ensemble mean suggests that the dominant contribution to the resumed atmospheric CH4 growth after 2006 comes from microbial sources (more from agriculture and waste sectors than from natural wetlands), with an uncertain but smaller contribution from fossil CH4 emissions. In addition, a decrease in biomass burning emissions (in agreement with the biomass burning emission databases) makes the balance of sources consistent with atmospheric 13CH4 observations. In most of the top-down studies included here, OH concentrations are considered constant over the years (seasonal variations but without any inter-annual variability). As a result, the methane loss (in particular through OH oxidation) varies mainly through the change in methane concentrations and not its oxidants. For these reasons, changes in the methane loss could not be properly investigated in this study, although it may play a significant role in the recent atmospheric methane changes as briefly discussed at the end of the paper.