Tracking every nation’s contribution to climate change
A groundbreaking study published today sheds light on the historical contributions of different nations to global warming through their emissions of key greenhouse gases since 1850. This research marks a significant step in tracking the impacts of climate change in a critical decade for climate policy.
The collaborative effort includes several members of the team responsible for the annual Global Carbon Budget and utilizes published records of historical emissions of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) from the pre-industrial period to 2021.
The study, led by Dr. Matthew Jones from the Tyndall Centre for Climate Change Research at the University of East Anglia (UEA) calculated the global mean surface temperature response to emissions of all three gases. The researchers also analyzed national contributions to warming resulting from emissions of each gas, including those from fossil fuel and land use sectors.
The findings, published in the journal Scientific Data, offer a comprehensive ranking of countries that have contributed the most to global warming and provide insights into how these contributions have evolved over recent decades.
For instance, the study highlights changes since 1992, when the United Nations Framework Convention on Climate Change (UNFCCC) was established, representing a key milestone in international climate policy.
Up to 2021, the largest contributors to global warming through emissions of all three gases since 1850 were the USA (0.28°C / 17.3% of warming induced by global emissions of all three GHGs), China (0.20°C / 12.3%), Russia (0.10°C / 6.1%), Brazil (0.08°C / 4.9%), India (0.08°C / 4.8%), and Indonesia, Germany, UK, Japan, and Canada (each contributing 0.03-0.05°C).
Of the three greenhouse gases, global emissions of CO2 have had the most significant impact on warming. The study reveals that up to 2021, warming through global CO2 emissions was 1.11°C, through CH4 emissions it was 0.41°C, and through N2O emissions it was 0.08°C.
Moreover, 69.1% of the total warming caused by the three gases was related to CO2 emissions alone. This percentage varies across countries and tends to be lowest in nations with large agricultural sectors, as agriculture is a major source of CH4 and N2O emissions.
As an example, the research breaks down the contributions of each gas for several countries: UK (CO2 accounts for 87.6% of warming induced by national emissions of all three GHGs), USA (83.3%), Russia (76.1%), Indonesia (71.3%), Brazil (64.7%), and China (64.3%).
The emissions data for CO2 used in this study came from the Global Carbon Budget, while figures for CH4 and N2O were provided by the Potsdam Institute for Climate Impact Research (PIK). This research represents a crucial tool for understanding the historical contributions of various countries to global warming and informing future climate policy discussions.
“Countries have made commitments to reduce their emissions of CO2, CH4 and N2O with the goal of avoiding the most detrimental impacts of climate change, including from drought, wildfires, flooding and sea level rise,” said Dr. Jones.
“This new dataset will prove a critical tool for tracking the effect of changing national emissions on warming, for example as a result of climate policies implemented since the Paris Agreement. During the coming years, we hope to see the warming contributions by all countries level off, with no new additions to warming year-on-year, as commitments to reach net-zero emissions are met or surpassed.”
Since 1992, there has been a shift in the contributions of various countries to global warming. China, for instance, has surpassed Russia and is now the second largest contributor to global warming. Similarly, Indonesia has overtaken Germany and the UK, securing the sixth spot on the list of top contributors to global warming.
“Notably, the combined contributions to warming from Brazil, South Africa, India and China rose from 17% in 1992 to 23% in 2021, whereas the contribution from the industrialised OECD countries fell slightly from 47% to 40%,” said Dr. Jones.
“These examples illustrate how the contributions to global warming from industrialising nations are rising as their emissions grow relative to early-industrialisers, many of which have begun to decarbonise.”
The study sheds light on the differing causes of national contributions to global warming, particularly in countries at varying stages of industrialization. It reveals that in 50% of the world’s nations, the land use and forestry sectors continue to have a significant impact on global warming, accounting for a substantial portion of emissions since 1850.
“The contributions of Brazil, Indonesia and Argentina and many other countries are still dominated by emissions linked to historical deforestation and agricultural expansion since 1850,” said Dr. Jones.
“However, in most countries, fossil emissions have exceeded land use during the past few decades, meaning additional contributions to warming have mainly been caused by fossil fuel emissions.
“Since 1992, the additional warming caused by global fossil fuel emissions has been over four times greater than the additional warming caused by land use change.”
The United Nations Framework Convention on Climate Change (UNFCCC) regulates the emissions of CO2, CH4, and N2O due to their enduring and potent impact on the climate. Under the Paris Agreement, countries set CO2 targets through nationally determined contributions (NDCs), with approximately 90% of NDCs also incorporating targets for CH4 and N2O emissions.
As a result, closely monitoring the emissions of CO2, CH4, and N2O, as well as the climate’s response to these emissions, is essential for maintaining accountability in relation to NDCs.
Additionally, this research aims to contribute to the first Global Stocktake of the UNFCCC, a process outlined in the Paris Agreement to evaluate each nation’s progress in achieving the agreement’s objective of limiting global warming to 1.5°C. The results of this study will be presented at the COP28 conference this year.
The group responsible for the creation of this new dataset comprises scientists from various prestigious institutions, including the Center for International Climate Research (CICERO) in Norway, the Potsdam Institute for Climate Impact Research (PIK) and Ludwig Maximilian University of Munich in Germany, the International Institute for Applied Systems Analysis (IIASA) in Austria, the Woodwell Climate Research Center in the United States, and the University of Exeter in the United Kingdom.
Study co-author Professor Pierre Friedlingstein, a member of Exeter’s Global Systems Institute, emphasized the dataset’s distinctiveness. “This publication is quite unique. It will provide not only an annual update on the greenhouse gas emissions for all countries of the world but also their respective contribution to global warming. The dataset reveals the dominant role of some key countries, such as the USA, China, and EU27, which together account for 40% of the global warming due to CO2, CH4, and N2O.”
Setting this dataset apart from its predecessors is its commitment to regular updates, with at least an annual refresh as new national emissions figures emerge, for instance, during the publication of the Global Carbon Budget. The dataset is accessible to the public through an online repository.
“By focusing on the three gases that most countries include in their NDCs, this dataset is uniquely positioned to informing climate policy and benchmarking,” said Dr. Jones. “It should become a living resource for continually tracking contributions to climate change and, more importantly, how those are changing.”
The warming resulting from the emissions of CO2, CH4, and N2O closely aligns with the values reported by the Intergovernmental Panel on Climate Change (IPCC). However, the present study does not take into account the cooling effect of human-generated aerosols, estimated by the IPCC to be 0.4°C, or the warming impact of certain other emitted gases, such as chlorofluorocarbons. These aerosols and gases are infrequently included in nationally determined contributions (NDCs).
The full dataset described in the paper is available via this link: https://zenodo.org/record/7636699#.Y_c9O-zP1JE
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