In 2022, total gross greenhouse gas emissions in the United States were **** billion metric tons of carbon dioxide equivalent (GtCO₂e). Although this was the second consecutive year that U.S. GHG emissions increased, they remained below pre-COVID 19 levels. The U.S. has set the target of achieving a 50 to 52 percent reduction in economy-wide emissions by 2030, relative to 2005 levels. As of 2022, gross GHG emissions were **** percent lower than they were in 2005.

In 2022, total gross greenhouse gas emissions in the United States increased by *** percent from 2021 levels. The largest annual reduction in U.S. emissions over the past three decades was observed in 2020, when COVID-19-related lockdowns and restrictions caused emissions to plummet almost nine percent from 2019 levels. This was followed by an annual increase of *** percent.

Energy consumption in the United States produced 4.8 billion metric tons of carbon dioxide (GtCO₂) in 2024 - a decrease of 0.4 percent from the previous year. U.S. CO₂ emissions from energy consumption have fallen by approximately 20 percent since 2005. Sources of emissions in the U.S. The main source of CO₂ emissions in the U.S. is the transportation sector. For many years, the power sector was the country’s biggest contributor to CO₂ emissions, but the transition towards cleaner energy sources and a shift away from coal-fired power generation – the most carbon intensive fossil fuel – have slashed emissions from this sector. Meanwhile, transportation emissions have continued to rise, except for an unprecedented drop in 2020 due to the outbreak of COVID-19. U.S. transportation emissions The U.S. is the biggest contributor to global transportation emissions by far. The states with the largest transportation-related emissions in the U.S. are Texas and California, which combined account for almost one quarter of total U.S. transportation emissions.

Fossil fuel carbon dioxide emissions (ffCO2) constitute the majority of greenhouse gas emissions and are the main determinent of global climate change. The COVID-19 pandemic caused wide-scale disruption to human activity and provided an opportunity to evaluate our capability to detect ffCO2 emission reductions. Quantifying changes in ffCO2 levels is especially challenging in cities, where climate mitigation policies are being implemented but local emissions lead to spatially and temporally complex atmospheric mixing ratios. Here, we used direct observations of on-road CO2 mixing ratios with analyses of the radiocarbon (14C) content of annual grasses collected by community scientists in Los Angeles and California, USA to assess reductions in ffCO2 emissions during the first two years of the COVID-19 pandemic. With COVID-19 mobility restrictions in place in 2020, we observed a significant reduction in ffCO2 levels across California, especially in urban centers. In Los Angeles, CO2 enhancements on freeways were 60 ± 16% lower and ffCO2 levels were 38-52% lower than in pre-pandemic years. By 2021, California's ffCO2 levels rebounded to pre-pandemic levels, albeit with substantial spatial heterogeneity related to local and regional pandemic measures. Taken together, our results indicate that a reduction in traffic emissions by ~60% (or 10-24% of Los Angeles' total ffCO2 emissions) can be robustly detected by plant 14C analysis, and pave the way for mobile- and plant-based monitoring of ffCO2 emissions in cities without CO2 monitoring infrastructure such as those in the Global South. Methods On-road carbon dioxide (CO2) data was collected using a cavity ringdown spectrometer (Picarro, Inc) installed inside a mobile laboratory. Freeways in the Los Angeles metropolitan area in California were surveyed using the mobile laboratory on July weekdays in 2019, 2020, and 2021. Alongside the measurements of ambient CO2 mixing ratios on the freeways, we also measured meteorological variables using a compact weather sensor (METSENS500 Campbell Scientific, Inc) and position data using a global satellite positioning device (GPS 16X, Garmin, Ltd.). The CO2 data was calibrated using a two-point linear correction based on measurements of known mixing ratios before and after each day of data collection. Data was synchronized into five-second intervals and gridded into 100m road intervals. Enhancements of CO2 ("CO2xs") were calculated by subtracting a background from all measurements, which we characterized using flask sample data from NOAA's Global Monitoring Division's site in Cape Kumukahi, Hawaii (Dlugokencky et al., 2021). We filtered the data to only include measurements collected on freeways that spatially overlapped with the 2020 dataset. We also only include data collected during daytime hours (11AM - 4PM, local time). Plants for radiocarbon analysis were sampled by community scientists across the state of California in 2020 and 2021. Community scientists mailed annual grasses in paper envelopes with the sample location and collection date. To prepare the samples for radiocarbon analysis, we washed them and weighed out approximately 4 mg of the latest growing biomass. Then we sealed the samples into quartz tubes with cuprous oxide. The samples were then evacuated and combusted for three hours at 900°C. The resulting CO2 was purified cryogenically and converted to graphite using a sealed tube zinc reduction method (Xu et al., 2007). The graphite was then analyzed for radiocarbon at the W. M. Keck Carbon Cycle Accelerator Mass Spectrometer facility at the University of California, Irvine.

Recommended citation

Gütschow, J.; Busch, D.; Pflüger, M. (2025): The PRIMAP-hist national historical emissions time series v2.7 (1750-2024). zenodo. doi:10.5281/zenodo.17090760.

Gütschow, J.; Jeffery, L.; Gieseke, R.; Gebel, R.; Stevens, D.; Krapp, M.; Rocha, M. (2016): The PRIMAP-hist national historical emissions time series, Earth Syst. Sci. Data, 8, 571-603, doi:10.5194/essd-8-571-2016

Content

• Use of the dataset and full description
• Abstract
• Support
• Sources
• Files included in the dataset
• Notes
• Data format description (columns)
• References
• Changelog

Abstract

The PRIMAP-hist dataset combines several published datasets to create a comprehensive set of greenhouse gas emission pathways for every country and Kyoto gas, covering the years 1750 to 2024, and almost all UNFCCC (United Nations Framework Convention on Climate Change) member states as well as most non-UNFCCC territories. The data resolves the main IPCC (Intergovernmental Panel on Climate Change) 2006 categories. For CO2, CH4, and N2O subsector data for Energy, Industrial Processes and Product Use (IPPU), and Agriculture are available. The "country reported data priority" (CR) scenario of the PRIMAP-hist datset prioritizes data that individual countries report to the UNFCCC.

For developed countries, AnnexI in terms of the UNFCCC, this is the data submitted anually in the "National Inventory Submissions". Until 2023 data was submitted in the "Common Reporting Format" (CRF). Since 2024 the new "Common Reporting Tables" (CRT) are used.For developing countries, non-AnnexI in terms of the UNFCCC our preferred data source are the Common Reporting Tables (CRT) submitted with the Biannial Transparency Reports (BTR). When countries do not provide the tables we read available data from the pdf reports and use additional submissions (Biannial Update Reports (BUR), National Communications (NC), and National Inventory Reports (NIR)) read from pdf and xlsx/csv files and for older submissions obtained from the UNFCCC DI portal (di.unfccc.int). For a list of these submissions please see below. For South Korea the 2024 official GHG inventory has not yet been submitted to the UN but is included in PRIMAP-hist. PRIMAP-hist also includes official data for Taiwan which is not recognized as a party to the UNFCCC. As the USA have not submitted any data to the UNFCCC this year we use the draft inventory report which the Environmental Defense Fund (EDF) obtained from the US Environmental Protection Agency (EPA) through the Freedom of Information Act.

Gaps in the country reported data are filled using third party data such as CDIAC, EI (fossil CO2), Andrew cement emissions data (cement), FAOSTAT (agriculture), and EDGAR 2024 (all sectors for CO2, CH4, N2O, HFCs, PFCs, SF6, NF3, except energy CO2). Lower priority data are harmonized to higher priority data in the gap-filling process.

For the third party priority time series gaps in the third party data are filled from country reported data sources.

Data for earlier years which are not available in the above mentioned sources are sourced from EDGAR-HYDE, CEDS, and RCP (N2O only) historical emissions.

The v2.4 release of PRIMAP-hist reduced the time-lag from 2 to 1 years for the October release. Thus the present version 2.7 includes data for 2024. For energy CO2 growth rates from the Energy Institute's *Statistical Review of World Energy* are used to extend the country reported data to 2024. For CO2 from cement production Andrew cement data are used for a few countries. For all other sectors and gases no emission estimates exist. Thus PRIMAP-hist relies on numerical methods and uses a linear extrapolation based on the last 5 years. COVID-19 has primarily impacted energy related emissions and in tests with CRF data no impact of COVID in the performance of linear extrapolation of emissions data in the other sectors has been detected. For the few cases where extrapolation is needed for energy CO2 we use a 15 year trend for the extrapolation.

Version 2.7 of the PRIMAP-hist dataset does not include emissions from Land Use, Land-Use Change, and Forestry (LULUCF) in the main file. LULUCF data are included in the file with increased number of significant digits and have to be used with care as they are constructed from different sources using different methodologies and are not harmonized.

The PRIMAP-hist v2.7 dataset is an updated version of

Gütschow, J.; Pflüger, M.; Busch, D. (2025): The PRIMAP-hist national historical emissions time series v2.6.1 (1750-2023). zenodo. doi:10.5281/zenodo.15016289.

The Changelog indicates the most important changes. You can also check the issue tracker on github.com/JGuetschow/PRIMAP-hist for additional information on issues found after the release of the dataset. Detailed per country information is available from the detailed changelog which is available on the primap.org website and on zenodo.

Use of the dataset and full description

Before using the dataset, please read this document and the article describing the methodology, especially the section on uncertainties and the section on limitations of the method and use of the dataset.

Gütschow, J.; Jeffery, L.; Gieseke, R.; Gebel, R.; Stevens, D.; Krapp, M.; Rocha, M. (2016): The PRIMAP-hist national historical emissions time series, Earth Syst. Sci. Data, 8, 571-603, doi:10.5194/essd-8-571-2016

Please notify us (support@johannes-guetschow@.de) if you use the dataset so that we can keep track of how it is used and take that into consideration when updating and improving the dataset.

When using this dataset or one of its updates, please cite the DOI of the precise version of the dataset used and also the data description article which this dataset is supplement to (see above). Please consider also citing the relevant original sources when using the PRIMAP-hist dataset. See the full citations in the References section further below.

Since version 2.3 we use the data formats developed for the PRIMAP2 climate policy analysis suite: PRIMAP2 on GitHub. The data are published both in the interchange format which consists of a csv file with the data and a yaml file with additional metadata and the native NetCDF based format. For a detailed description of the data format we refer to the PRIMAP2 documentation.

We have also included files with more than three significant digits. These files are mainly aimed at people doing policy analysis using the country reported data scenario (HISTCR). Using the high precision data they can avoid questions on discrepancies with the reported data. The uncertainties of emissions data do not justify the additional significant digits and they might give a false sense of accuracy, so please use this version of the dataset with extra care.

Support

If you encounter possible errors or other things that should be noted, please check our issue tracker at github.com/JGuetschow/PRIMAP-hist and report your findings there. Please use the tag "v2.7" in any issue you create regarding this dataset.

If you need support in using the dataset or have any other questions regarding the dataset, please contact nc-support@johannes-guetschow.de.

Basic support is free for non-commercial users and most questions can be answered with a short e-mail. However, we do not have the resources to provide extensive support free of charge. For commercial users support will be included with the commercial license (see below).

License

Since v2.7 PRIMAP-hist is published under a non-commercial license (CC BY-NC-SA). This means that commercial users can not use it freely and have to obtain a commercial license. The commercial license is only available for the country reported priority (CR) time-series as the third party priority (TP) time-series builds heavily on EDGAR and FAOSTAT data. For commercial customers wanting to use the TP time-series we offer to develop custom code to generate the data locally. Please contact commercial-support@johannes-guetschow.de for more information.

Sources

• Global CO2 emissions from cement production v250226 data, paper: Andrew
  (2025), Andrew (2019)
• EI Statistical Review of World Energy 2025 website: Energy Institute (2025)
• CDIAC data: Hefner and Marland (2023), data: Hefner (2024), paper: Gilfillan and Marland (2021)
• CEDS: data: Hoesly et al. (2020), paper: Hoesly et al. (2018)
• EDGAR 2024: <a

Domestic commercial aircraft in the United States produced roughly *** million metric tons of carbon dioxide equivalent (MtCO₂e) in 2022. U.S. commercial aviation emissions have increased annually since 2020, a year in which COVID-19-related travel restrictions caused emissions to plummet ** percent year-on-year. Although emissions have rebounded since then, they have remained below pre-pandemic levels.

Global carbon dioxide emissions from fossil fuels and industry totaled 37.01 billion metric tons (GtCO₂) in 2023. Emissions are projected to have risen 1.08 percent in 2024 to reach a record high of 37.41 GtCO₂. Since 1990, global CO₂ emissions have increased by more than 60 percent. Who are the biggest emitters? The biggest contributor to global GHG emissions is China, followed by the United States. China wasn't always the world's biggest emitter, but rapid economic growth and industrialization in recent decades have seen emissions there soar. Since 1990, CO₂ emissions in China have increased by almost 450 percent. By comparison, U.S. CO₂ emissions have fallen by 6.1 percent. Nevertheless, the North American country remains the biggest carbon polluter in history. Global events cause emissions to drop The outbreak of COVID-19 caused global CO₂ emissions to plummet some 5.5 percent in 2020 as a result of lockdowns and other restrictions. However, this wasn't the only time in recent history when a major global event caused emissions reductions. For example, the global recession resulted in CO₂ levels to fall by almost two percent in 2009, while the recession in the early 1980s also had a notable impact on emissions. On a percentage basis, the largest annual reduction was at the end of the Second World War in 1945, when emissions decreased by 17 percent.

Qatar has the highest per capita carbon dioxide emissions worldwide, at **** metric tons per person. Many countries in the Middle East had high levels emissions, especially when compared to countries in Africa. Greenhouse gas emissions worldwide Some of the Middle East’s largest oil producing countries, including Qatar, the United Arab Emirates, and Saudi Arabia are among the world’s largest carbon dioxide (CO₂) emitters per capita. Countries such as the United States, Australia and Canada also show disproportionately high levels of emission per inhabitant. Despite a relatively low population for its size, Canada’s CO₂ emissions have recently surpassed *** million metric tons, and the country is now amongst the largest producers of CO₂ emissions worldwide. Rising emissions Global greenhouse gas emissions have been on the rise since the industrial revolution began approximately 200 years ago. Over the past half-century CO₂ emissions have skyrocketed, and climbed to a record high in recent years. Yet, emissions fell considerably in 2020 as a result of the COVID-19 pandemic, which caused disruptions to transportation and industrial activities.

China released **** billion metric tons of carbon dioxide emissions in 2023, making it by far the world's largest polluter that year. While most countries experienced dramatic emission reductions in 2020 due to COVID-19, China was one of only a handful of countries where emissions increased. China’s contribution to global emissions China is now the largest emitter of CO₂ emissions worldwide, producing more than twice the CO₂ emissions of the United States each year. Although China’s contributions to global CO₂ emissions only really started at the turn of the **** century, it has now produced the second-largest volume every in terms of cumulative CO₂ emissions. However, this is still half the total produced by the United States, where industrialization began far earlier. Main sources of China emissions One of the main reasons for China’s high level of emissions is the reliance on coal in its power mix. Coal is the most polluting of energy sources, and accounts for roughly ** percent of China’s electricity generation. In 2020, China announced an ambitious plan to become carbon-neutral by 2060, meaning a significant move away from fossil fuel powered transport and energy is needed.