Abstract. To track progress towards keeping global warming well below 2 ∘C or even 1.5 ∘C, as agreed in the Paris Agreement, comprehensiveup-to-date and reliable information on anthropogenic emissions and removalsof greenhouse gas (GHG) emissions is required. Here we compile a new synthetic dataset on anthropogenic GHG emissions for 1970–2018 with afast-track extension to 2019. Our dataset is global in coverage and includesCO2 emissions, CH4 emissions, N2O emissions, as well as those from fluorinated gases (F-gases: HFCs, PFCs, SF6, NF3) andprovides country and sector details. We build this dataset from the version 6 release of the Emissions Database for Global Atmospheric Research (EDGAR v6) and three bookkeeping models for CO2 emissions from land use,land-use change, and forestry (LULUCF). We assess the uncertainties of global greenhouse gases at the 90 % confidence interval (5th–95thpercentile range) by combining statistical analysis and comparisons ofglobal emissions inventories and top-down atmospheric measurements with anexpert judgement informed by the relevant scientific literature. We identifyimportant data gaps for F-gas emissions. The agreement between our bottom-up inventory estimates and top-downatmospheric-based emissions estimates is relatively close for some F-gasspecies (∼ 10 % or less), but estimates can differ by an order of magnitude or more for others. Our aggregated F-gas estimate is about 10 % lower than top-down estimates in recent years. However, emissions from excluded F-gas species such aschlorofluorocarbons (CFCs) or hydrochlorofluorocarbons (HCFCs) arecumulatively larger than the sum of the reported species. Using globalwarming potential values with a 100-year time horizon from the Sixth Assessment Report by the Intergovernmental Panel on Climate Change (IPCC),global GHG emissions in 2018 amounted to 58 ± 6.1 GtCO2 eq.consisting of CO2 from fossil fuel combustion and industry (FFI) 38 ± 3.0 GtCO2, CO2-LULUCF 5.7 ± 4.0 GtCO2, CH4 10 ± 3.1 GtCO2 eq., N2O2.6 ± 1.6 GtCO2 eq., and F-gases 1.3 ± 0.40 GtCO2 eq. Initial estimates suggest further growth of 1.3 GtCO2 eq. in GHG emissions to reach 59 ± 6.6 GtCO2 eq. by 2019. Our analysis ofglobal trends in anthropogenic GHG emissions over the past 5 decades (1970–2018) highlights a pattern of varied but sustained emissions growth. There is high confidence that global anthropogenic GHG emissions haveincreased every decade, and emissions growth has been persistent across the different (groups of) gases. There is also high confidence that globalanthropogenic GHG emissions levels were higher in 2009–2018 than in any previous decade and that GHG emissions levels grew throughout the most recent decade. While the average annual GHG emissions growth rate slowed between2009 and 2018 (1.2 % yr−1) compared to 2000–2009 (2.4 % yr−1), the absolute increase in average annual GHG emissions by decade was neverlarger than between 2000–2009 and 2009–2018. Our analysis further revealsthat there are no global sectors that show sustained reductions in GHGemissions. There are a number of countries that have reduced GHG emissionsover the past decade, but these reductions are comparatively modest andoutgrown by much larger emissions growth in some developing countries suchas China, India, and Indonesia. There is a need to further develop independent, robust, and timely emissions estimates across all gases. As such, tracking progress in climate policy requires substantial investmentsin independent GHG emissions accounting and monitoring as well as in national and international statistical infrastructures. The data associatedwith this article (Minx et al., 2021) can be found at https://doi.org/10.5281/zenodo.5566761.
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Atmospheric verification of emissions reductions on paths to deep decarbonization
A central challenge for sustaining international cooperation to cut global greenhouse gas emissions is confidence that national policy efforts are leading to a meaningful impact on the climate. Here, we apply a detection protocol to determine when the measurable signal of atmospheric CO2can be distinguished from the noise of the carbon cycle and uncertainties in emission trends. We test that protocol with a database of 226 emission mitigation scenarios—the universe of scenarios vetted by the Intergovernmental Panel on Climate Change. These scenarios are descriptive of ‘baseline’ trajectories of emissions trends in the absence of new policies along with trajectories that reflect substantial policy efforts to stop warming at 1.5 °C–2 °C above pre-industrial levels, as embodied in the Paris Agreement. The most aggressive mitigation scenarios (i.e. 1.5 °C) require 11–16 years to detect a signal of demonstrable progress from the noise; 2 °C scenarios lengthen detection by at least a decade. As more climate policy analysts face the reality that goals of 1.5 °C–2 °C seem infeasible, they have developed ‘overshoot’ scenarios with emissions that rise above the agreed goal and then, later on, fall aggressively to achieve it. These pathways come at the political cost of a 1–2 decade delay in detection, even for the 1.5 °C scenarios. The Paris Agreement requires a global ‘stocktake’ that interrogates national mitigation efforts; our results suggest that this effort must grapple with the question of when the world can gain confidence that the diplomacy on climate is demonstrably making an impact.
more » « less- NSF-PAR ID:
- 10401664
- Publisher / Repository:
- IOP Publishing
- Date Published:
- Journal Name:
- Environmental Research Letters
- Volume:
- 18
- Issue:
- 4
- ISSN:
- 1748-9326
- Page Range / eLocation ID:
- Article No. 044003
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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