Assessments

The Montreal Protocol on Substances that Deplete the Ozone Layer was a landmark global agreement, signed in 1987, to protect the stratospheric ozone layer by phasing out the production and consumption of ozone depleting substances. The Scientific Assessment Panel (SAP) of the Montreal Protocol is charged with providing the scientific information that forms the basis for decisions made by the Parties to the treaty and producing the quadrennial Scientific Assessment of Ozone Depletion. CSL Director David Fahey serves as one of the four co-chairs of the SAP that produces the report. The 2022 Ozone Assessment is the tenth such report, and contains the most up-to-date understanding of stratospheric ozone depletion.

WMO/UNEP Scientific Assessments of Ozone Depletion

35th Anniversary Protecting the Ozone Layer (2022)

Additional UNEP Synthesis reports related to the Montreal Protocol:

• One Atmosphere: An Independent Expert Review on Solar Radiation Modification Research and Deployment (2023)
• Report on the Unexpected Emissions of CFC-11 (2021)
• Cooling Emissions and Policy Synthesis Report: Benefits of cooling efficiency and the Kigali Amendment (2020)
• Drawing Down N₂O to Protect Climate and the Ozone Layer (2013)
• HFCs: A Critical Link in Protecting Climate and the Ozone Layer (2011)

Since its inception in 1988, the Intergovernmental Panel on Climate Change (IPCC) Working Group I (WGI) has provided assessments and special reports that inform policy makers worldwide about global climate change. CSL scientists have served as chairs, authors, or reviewers for all of the six Assessment Reports (AR). The latest report, AR6 released in 2021, provides a comprehensive assessment of the physical science basis of climate change since the prior report was released.

IPCC AR6 Climate Change 2021: The Physical Science Basis
IPCC AR5 Climate Change 2013: The Physical Science Basis

The U.S. Global Change Research Program (USGCRP) is a federally-mandated program that coordinates research and collaboration between 13 U.S. Federal agencies in understanding the natural and man-made forces that influence global climate and the impacts on society. The Global Change Research Act of 1990 mandates that the USGCRP deliver a national climate assessment report to Congress and the President no less than every 4 years. This report provides a synthesis of the cumulative knowledge on climate to inform U.S. policy makers in their efforts to formulate effective strategies for preventing, mitigating, and adapting to the effects of global change. The Fourth National Climate Assessment (NCA4) is the most recent report, consisting of two volumes published in 2017 and 2018. CSL Director David Fahey served as a Coordinating Lead Author for the NC4.

NCA4, Volume I: Climate Science Special Report
NCA4, Volume II: Impacts, Risks, and Adaptation in the United States

Tropospheric Ozone Assessment Report (TOAR) Global metrics for climate change, human health, and crop/ecosystem research is an official Activity of the International Global Atmospheric Chemistry Project (IGAC), co-chaired by CSL/CIRES scientist Owen Cooper. TOAR's mission is to provide the research community with an up-to-date scientific assessment of the global distribution and trends of tropospheric ozone from the surface to the tropopause. The first phase of TOAR (TOAR-I) spanned 2014–2019 and the findings were published as a series of open-access, peer-reviewed manuscripts in a Special Feature of the journal Elementa. The second phase of TOAR (known as TOAR-II) was initiated by the IGAC SSC on 6 November 2019 and spans the next five years (2020-2024).

TOAR has also built the world's largest database of ozone metrics, calculated consistently for over 9000 surface ozone time series worldwide. Created by Forschungszentrum Jülich, the database is entirely open-access, allowing anyone to download the ozone metrics and conduct their own research.

TOAR-I Elementa: Science of the Anthropocene Special Feature Collection
TOAR Data Portal: Tropospheric Ozone Database

Data and metrics from TOAR were included in The Global Burden of Disease 2019 study to assess the human mortality due to long-term ozone exposure.

CSL scientists regularly contribute to the annual State of the Climate reports, which are led by NOAA's Center for Weather and Climate at the National Centers for Environmental Information (NCEI) and published by the Bulletin of the American Meteorological Society (BAMS). The State of the Climate report offers annual insights on global climate indicators, extreme weather events, and other important environmental data.

In recent years, CSL scientists have co-authored chapters on Tropospheric Ozone (Owen Cooper, 2015–2022), Stratospheric Water Vapor (Sean Davis and Karen Rosenlof, 2015–2022), and Sudden Stratospheric Warming (Amy Butler, 2019 and 2021).

Annual State of the Climate Reports

Chemical Kinetics and Photochemical Data for Use in Atmospheric Studies is compilation and evaluation of the latest kinetic and photochemical data for use by modelers in computer simulations of atmospheric chemistry, which is updated and published every 2-3 years. The most recent, Evaluation Number 19, was published in 2020. Evaluations are prepared by the NASA/JPL Panel for Data Evaluation, which is currently co-chaired by CSL scientist Jim Burkholder.

Jet Propulsion Laboratory (JPL) Kinetic Data Evaluation

SPARC (Stratosphere-troposphere Processes and their Role in Climate) is a core project of the World Climate Research Programme (WCRP) that coordinates efforts and assessments relating to climate variability and prediction. Several CSL scientists are involved in SPARC activities and have contributed to recent reports.

• SPARC Hunga Tonga-Hunga Ha'apai (HTHH) stratospheric impacts
• SPARC Water Vapour Assessment (WAVAS) Phase I and Phase II
• SPARC/IO3C/GAW Report on Long-term Ozone Trends and Uncertainties in the Stratosphere
• SPARC Report on the Mystery of Carbon Tetrachloride
• SPARC Reanalysis Intercomparison Project (S-RIP)
• SPARC Lifetimes of Stratospheric Ozone-Depleting Substances, Their Replacements, and Related Species