Our world is changing at an accelerating rate. The global human population has grown from 6.1 billion to 7.1 billion in the last 15 years and is projected to reach 11.2 billion by the end of the century. The distribution of humans across the globe has also shifted, with more than 50 percent of the global population now living in urban areas, compared to 29 percent in 1950. Along with these trends, increasing energy demands, expanding industrial activities, and intensification of agricultural activities worldwide have in turn led to changes in emissions that have altered the composition of the atmosphere.
These changes have led to major challenges for society, including deleterious impacts on climate, human, and ecosystem health. Climate change is one of the greatest environmental challenges facing society today. Earth’s average surface temperature has already increased by more than 1.4°F (0.8°C) over the past 100 years and is expected to continue to increase, leading to major impacts on sea level, Arctic sea ice, and precipitation patterns. Air pollution is a major threat to human health, as one out of eight deaths globally is caused by air pollution. Future food production and global food security are vulnerable to both global change and air pollution. Atmospheric chemistry research (see Box S.1) is a key part of understanding and responding to these challenges.
Atmospheric chemistry research has supported policy decisions that have greatly improved human health and welfare. For example, research findings guided policies to reduce poor air quality in urban areas (“smog”), acid deposition (“acid rain”), and stratospheric ozone depletion (including the Antarctic “ozone hole”). These historical examples share some common elements. Knowledge drawn from laboratory experiments, theory, field measurements, and models provided a fundamental understanding of atmospheric behavior. When rapid environmental change was observed, additional and targeted research helped elucidate the physical processes and human activities driving these changes. A predictive capability was then developed that en-
abled evaluation of future scenarios of environmental and societal impacts that could inform policy choices (see Figure S.1). Continuing research refines the predictive capability and provides a context for interpreting observations from ongoing atmospheric monitoring and assessment efforts. The goal of atmospheric chemistry research is to anticipate and prepare for future environmental challenges with an enhanced predictive capability that foresees environmental changes and societal impacts, rather than just reacting to them after they occur.
The last comprehensive report to examine the field of atmospheric chemistry as a whole (Global Tropospheric Chemistry: A Plan for Action ) was published more than 30 years ago.
In 2015, the National Science Foundation (NSF) requested that the National Academies of Sciences, Engineering, and Medicine undertake a study to identify priorities and strategic steps forward for atmospheric chemistry research for the next decade. The Academies formed the Committee on the Future of Atmospheric Chemistry Research (referred to as the Committee) to summarize the rationale and need for supporting a comprehensive U.S. research program in atmospheric chemistry; comment on the broad trends in laboratory, field, satellite, and modeling studies of atmospheric chemistry; determine the priority areas of research for advancing the basic science of at-
mospheric chemistry; and identify the highest priority needs for improvements in the research infrastructure to address those priority research topics (see Box 1.2 for the full statement of task for this report). The report also describes the scientific advances over the past decade in six core areas of atmospheric chemistry: emissions, chemical transformations, oxidants, atmospheric dynamics and circulation, aerosol particles and clouds, and biogeochemical cycles and deposition. As shown in Figure S.1, these topics define core components of the scientific discipline of atmospheric chemistry. The report was developed for the NSF’s Atmospheric Chemistry Program; however, the results presented will be of interest to other agencies and programs that support atmospheric chemistry research.
A central part of the Committee’s activities was to seek advice from the U.S. atmospheric chemistry community. Community input was solicited during a series of “town hall” meetings and through an online “virtual town hall” website (see Appendix B). Using this community input and a survey of today’s research as the underlying basis, the Committee ultimately chose five Priority Science Areas that it believes will drive atmospheric chemistry research over the next decade. The first two Priority Science Areas are necessary for building the foundation of atmospheric chemistry, aimed at providing further growth in understanding how the atmosphere works. The next three Priority Science Areas directly address major challenges facing society, for which advances in atmospheric chemistry are required to make progress. In total, these Priority Science Areas cover a broad range of research questions. Specific areas of focus are provided to address key science gaps within each area, along with examples of actions needed to address those gaps (in Chapter 5).
Priority Science Area 1: Advance the fundamental atmospheric chemistry knowledge that enables predictive capability for the distribution, reactions, and lifetimes of gases and particles.
Predictive capability starts with a fundamental understanding of the atmospheric chemistry occurring now. While some predictions can be made with confidence using the current understanding, important gaps and inconsistencies remain. Advances in atmospheric chemistry experiments, theory, modeling, and observational capabilities enable atmospheric chemists to identify and begin to narrow those gaps and to resolve discrepancies for today’s atmospheric composition and chemical reactions.
Actions needed to address key scientific gaps include:
- Quantify reaction rates and understand detailed chemical mechanisms in multipollutant and multiphase environments that cover the chemical and dynamical regimes from polluted urban to natural remote regions.
- Identify and quantify important atmospheric oxidants or other reactants that lead to transformation and removal of chemical species from the atmosphere across broad spatial and temporal scales.
- Develop a stronger understanding of the influences that heterogeneous chemistry exerts on tropospheric composition.
- Understand and quantify the influence of the coupling between chemical and meteorological processes on the distribution of trace constituents in the troposphere.
- Understand and quantify the influence of the coupling between chemical, dynamical, and radiative processes involving stratospheric chemistry.
Priority Science Area 2: Quantify emissions and deposition of gases and particles in a changing Earth system.
Emission and deposition processes govern concentrations and spatial distributions of gases and particles in the atmosphere. A predictive capability of these distributions is key for assessing the impacts of atmospheric processes on human and ecosystem health, weather, and climate. Research is needed to reduce uncertainties in emissions for known sources and constrain emissions of poorly understood constituents (e.g., bioparticles), as well as to understand deposition processes that remove reactive species. Sources of atmospheric constituents change as humans make new decisions about technology, energy systems, pollution control, agriculture, and transportation. Natural sources respond to meteorological conditions, changes in land use, longer-term changes in climate, and biogechemical and ecosystem feedbacks.
Actions needed to address these key scientific gaps include:
- Better determine emissions from both anthropogenic and natural sources and their spatial and temporal variations and trends.
- Identify mechanisms and measure rates by which wet and dry deposition removes aerosol particles and trace gases from the atmosphere.
- Determine the role of meteorology, including temperature, precipitation, and extreme events, on emissions and removal of atmospheric species.
- Determine the role of global change and societal choices (including changes in climate, energy choices, and land use) on the emissions and removal of atmospheric species.
Priority Science Area 3: Advance the integration of atmospheric chemistry within weather and climate models to improve forecasting in a changing Earth system.
Greenhouse gases and atmospheric particles impact the Earth’s radiation budget and dynamics of the atmosphere and thereby alter weather, for example, via changing precipitation patterns and monsoon circulations. Aerosol particles play a critical role through their influence on the growth, formation, and development of clouds and precipitation. In global climate models, the effects of atmospheric aerosol particle concentrations on radiation and the distribution and radiative properties of the Earth’s clouds is the most uncertain component of overall global radiative forcing. Changes in atmospheric dynamics and circulation that are linked to changes in atmospheric composition (e.g., precipitation patterns, monsoon circulations) are even more uncer-
tain than radiative forcing. During the past decade of intensive aerosol–cloud–climate research, some scientific gaps have been closed, and additional processes have been identified that still elude quantification. As with many complex systems in intermediate stages of understanding, this progress has not yet reduced the overall magnitude of uncertainty, leaving major deficiencies in the ability to project future climate.
The chemical reactions involving aerosol particles and gases determine not only particle formation but also the processes by which climate-relevant trace species are removed from the atmosphere. Atmospheric chemistry, therefore, remains the crucial component that allows estimates of the atmospheric lifetimes of many species, and consequently the ability of pollution to accumulate in the atmosphere and thus influence climate and weather. Some, but not all, studies of regional climate change (seasonal-to-interannual or longer-term projections) or weather forecasting have included heterogeneously distributed aerosol particles or ozone in their models. The atmospheric chemistry community needs to continue to work with the climate and weather research communities in several major areas so that knowledge of the many roles that atmospheric composition plays in climate and weather can be built into dynamical models.
The atmospheric chemistry community should expand interactions with the climate and weather research community to address these key scientific gaps:
- Determine the global distributions and variability of atmospheric trace gases and aerosol particles, and better understand their climate-relevant properties.
- Understand the role of aerosol particles as a modulator of cloud microphysics and precipitation efficiency in natural and anthropogenically perturbed environments.
- Develop accurate descriptions of the complex chemical and physical evolution of atmospheric constituents that can be implemented in models for robust prediction of the impact of the chemical state of the atmosphere on climate and weather.
Priority Science Area 4: Understand the sources and atmospheric processes controlling the species most deleterious to human health.
Atmospheric gases and particles have documented effects on multiple adverse health outcomes, including chronic and acute effects that can lead to mortality and different types of morbidity. It is estimated that air pollution is responsible for 1 out of 8 premature deaths (more than 7 million annually) worldwide. However, the specific chemical species that cause these various effects and potential synergisms among them are not well understood. Advanced atmospheric chemistry research techniques (e.g., models,
analytical methods, and instrumentation) are necessary to understand the identities, sources, and fates of the air pollutants that negatively affect human health.
The atmospheric chemistry community should expand interactions with the exposure, epidemiology, and toxicology research communities to address these key scientific gaps:
- Develop mechanistic understanding to predict the composition and transformations of atmospheric trace species that contribute to impacts on human health.
- Quantify the distribution of atmospheric constituents that impact human health.
- Determine what unique sources and chemical reactions occur in indoor environments that have implications for atmospheric chemistry and human health.
Priority Science Area 5: Understand the feedbacks between atmospheric chemistry and the biogeochemistry of natural and managed ecosystems.
Biogeochemical cycles control the elements that are necessary for life and connect chemistry in the atmosphere with oceans, the solid earth, and the terrestrial and marine biospheres. This exchange of compounds is tightly coupled to global food security (e.g., agriculture, fisheries) and certain energy sources (e.g., biofuels, wood). These exchange processes are influenced by human activity and global climate and are directly tied to natural and managed ecosystem health. In addition, biogeochemical cycles and ecosystem health play a central role in climate by regulating carbon uptake by the biosphere and the exchange of greenhouse gases and aerosol particle precursors. Finally, the biogeochemical cycling of toxic constituents (e.g., mercury) directly affects ecosystems as well as human health.
Major scientific goals include understanding the cycling of elements through the various components of the Earth system, the impacts of deposition of atmospheric nutrients and contaminants to natural and managed ecosystems, and the feedbacks of ecosystems onto the atmosphere. New laboratory and field studies are needed to characterize these atmospheric chemistry processes for future use in predictive models.
The atmospheric chemistry community should expand interactions with the ocean, land surface, and other Earth science research communities to address these key scientific gaps:
- Quantify the full suite of trace gases and particles deposited from the atmosphere and connect these to ecosystem responses.
- Identify and quantify the chemical composition, transformations, bioavailability, and transport of nutrients and contaminants in the global atmosphere and their interactions with the biosphere.
- Identify important feedbacks between atmospheric chemistry and the biosphere under global change.
To understand the trends that are currently occurring in the field of atmospheric chemistry and the research emphases of different federal groups supporting work in this area, the Committee requested information from five government agencies. In summary, the judgment of the Committee is that the field of atmospheric chemistry has been expanding for the past several decades, but the amount of funding for research in the field has not increased substantially.
In this context, the Committee made recommendations to help support research for the next decade to enable the Priority Science Areas identified in Chapter 5 (see Figure S.2). These programmatic and logistical actions are primarily directed to the NSF Atmospheric Chemistry Program and include the development of “tools”; the collection, analysis, and exchange of data; and increased collaborations within atmospheric chemistry and with other communities. The Committee recognizes that an important fraction of the NSF-funded research involving atmospheric chemistry research occurs through support to the National Center for Atmospheric Research (NCAR), and thus we also comment on NCAR’s role.
Development of Tools for Atmospheric Chemistry Research
Instruments used in laboratory experiments and deployed for remote and in situ measurements are key tools used by atmospheric chemists. New analytical techniques, instruments, and instrument platforms are needed to support the Priority Science Areas above. Similarly, a range of modeling tools is central to the development of a predictive understanding of atmospheric chemistry. NSF will play an essential role in fostering the development of the next generation of many of these tools, as could industry and other government funding agencies.
NSF’s Major Research Instrumentation (MRI) and Small Business Innovation Research/Small Business Technology Transfer Research (SBIR/STTR) programs have produced valuable breakthrough technologies that enabled improvements in atmospheric chemistry research. However, there are generally few of these opportunities for high-risk, high-reward proposals for instrument development in atmospheric chemistry at NSF. The Committee encourages the Atmospheric Chemistry Program to consider mechanisms for providing more support for development of instruments and measurement platforms by working more closely with other NSF programs and directorates. Viable mechanisms need to also be available within the Atmospheric and Geospace Sciences Division to submit proposals for new instruments and techniques that take extended periods of time to develop and test before they can be used to generate accurate and reliable data.
There are a wide variety of available modeling tools that vary in both spatial and temporal scale and technical approach. This diversity of approaches is needed to develop a broad toolbox to understand the complex problems in atmospheric chemistry. The disparate spatial and temporal scales of chemistry and transport in the atmosphere present a major challenge in building modeling tools and methodological approaches that effectively integrate across the scales. NSF should continue its investments in atmospheric chemistry and tracer-transport model development and applications, from developing and incorporating theoretical chemistry to predicting global composition. NSF could also emphasize endeavors that focus on modeling across spatial scales (urban to global) and temporal scales (weather to climate) to promote collaboration and coordination across agencies and different NSF divisions.
Recommendation 1: The National Science Foundation should ensure adequate support for the development of the tools necessary to accomplish the scientific goals for the atmospheric chemistry community, including the development of new laboratory and analytical instrumentation, measurement platforms, and modeling capabilities.
Information Collection, Analysis, and Archiving in the Era of “Big Data”
The collection of measurement data over long periods of time allows the discernment of trends that are not apparent in one-time field projects. Research at long-term field sites representing different environments is not adequately supported in the United States. Changing this would require a large scale coordinated effort and commitment by the research community and multiple funding agencies.
Established research sites with core measurement capabilities and long-term knowledge about regional photochemistry, meteorology, ecosystem properties, and biosphere–atmosphere exchange processes are a critical resource for making and interpreting new measurements. A distributed set of research sites that take advantage of existing infrastructure in other programs as much as feasible would be most cost effective. An interagency panel could prioritize the long-term sites and determine
- the required infrastructure;
- whether the sites would be centrally managed or managed by individual principal investigators;
- core measurements to be included with each site;
- procedures for the archiving of the samples collected at these sites; and
- criteria and a review process to support funding decisions.
Recommendation 2: The National Science Foundation should take the lead in coordinating with other agencies to identify the scientific need for long-term measurements and to establish synergies with existing sites that could provide core support for long-term atmospheric chemistry measurements, including biosphere–atmosphere exchange of trace gases and aerosol particles.
Answers to research questions are often apparent only after intensive data analysis; for example, the synthesis and analysis of existing datasets can be applied to test models across various regimes and guide future research directions. However, funding is often insufficient to mine field data deeply for thorough analysis or to re-analyze existing datasets. Longer grant periods or supplemental installments to afford principal investigators the time and effort to continue analyses may be needed to accomplish these efforts. NSF should also encourage and support new projects that use data mining to advance the science—a cost-effective way to advance the atmospheric chemistry research agenda. For a fraction of the cost of a field study, NSF could dedicate funds to encourage analysis of existing high-quality datasets using powerful data mining techniques developed by the computer science community and perform detailed intercomparisons using satellites, field measurements, and models.
Recommendation 3: The National Science Foundation should encourage mining and integration of measurements and model results that can merge and exploit past datasets to provide insight into atmospheric processes, as well as guide planning for future studies.
Management of large volumes of “big data” is becoming ubiquitous in atmospheric chemistry research as vast and multidimensional datasets are continuously generated. These datasets require increasingly large resources to manage. Mechanisms are needed for effectively and efficiently archiving, sharing, and mining data, including making them easily available to the broad scientific community and to the public.
The current availability of datasets varies substantially; some are archived at data centers while others are available only upon request from individual scientists. Agencies (in particular the National Aeronautics and Space Administration [NASA] and the National Oceanic and Atmospheric Administration [NOAA]) maintain data separately, and there is not a common data format that allows integration between models and measurements. NSF-funded research does require data management plans, but no central coordinated data archive and sharing system exists for atmospheric chemistry research.
NSF should require that future NSF-funded datasets be handled in a manner that allows ready access and comparison with previous datasets. The Committee envisions a centralized system for providing and supporting data management for atmospheric chemistry. Apart from providing facilities for data archiving, accessibility, and transparency, a centralized responsibility could assure that datasets are managed with expert preparation and fostering, along with sufficient and standard documentation and metadata. NSF could take the lead in coordinating with other federal and state agencies to establish such a system.
Recommendation 4: The National Science Foundation (NSF) should establish a data archiving system for NSF-supported atmospheric chemistry research and take the lead in coordinating with other federal and possibly state agencies to create a comprehensive, compatible, and accessible data archive system.
Imperative for Collaborations
Understanding and addressing challenges faced by society will rely on close integration of knowledge from multiple disciplines, including the physical, biological, and social sciences and engineering. While there are examples within NSF of programs that encourage interdisciplinary work, the Committee is concerned that mechanisms to support interdisciplinary work may encounter barriers due to NSF institutional and review structures. Interdisciplinary research often requires sustained long-term funding, which can be difficult to achieve using the typical 3-year NSF grants.
Given the important cross-disciplinary aspects of the science priorities for atmospheric chemistry, the NSF Atmospheric Chemistry Program should explore multiple options to address these well recognized challenges that the Foundation faces. In some NSF directorates, an effective approach has been to fund either virtual or on-the-ground centers that draw together scientists who have different expertise and are often geographically dispersed. Other options include defining funding mechanisms whereby small, focused teams can integrate the necessary expertise from multiple disciplines; identifying and altering structures that discourage integration across disciplines; and placing value on a “cross-disciplinary integration” component of proposal evaluation. Both single agency and cross-agency efforts are an essential component of the Priority Science Areas identified above.
Recommendation 5: The National Science Foundation should improve opportunities that encourage interdisciplinary work in atmospheric chemistry and facilitate inte-
gration of expertise across disciplines and across academia, institutes, government, and industry. This improvement may include support of focused teams and virtual or physical centers of sizes appropriate to the problem at hand.
The past success in understanding and applying atmospheric chemistry should be leveraged to improve air quality in many parts of the world. Although emissions have been reduced and air quality improved in the United States, many individuals are still living with dangerously high pollutant levels that impact their communities’ health and society. Working with underrepresented groups within the United States and with the international community is important for developing a global understanding of atmospheric chemistry and its impacts on human activities, especially as the importance of long-range transport of air pollution has become evident.
Understanding the interface between the processes controlling regional air quality and global atmospheric chemistry often requires establishing experimental programs with communities not traditionally included in the atmospheric chemistry community, especially those outside of domestic borders. This work may require nontraditional or international partnerships, and in some cases can encourage local scientific capacity building. Building the expert human capacity and observational and modeling capability at the regional level within the developing world through collaborations between U.S. atmospheric chemists and scientists in these regions has the potential to be a sustainable approach to addressing global air quality challenges. One possibility is establishing sites in developing countries that are part of larger networks for global scientific measurements. Another is the transfer of measurement and modeling capabilities to scientists in developing nations. Yet another is engaging underserved communities within the United States in addressing air quality issues through citizen science.
NSF already does a substantial amount to promote international collaborations. Activities within NSF (e.g., Partnerships for International Research and Education) and across multiple U.S. agencies (e.g., Partnerships for Enhanced Engagement in Research) are important for fostering global research programs and building global capacity in atmospheric chemistry.
Recommendation 6: The National Science Foundation, in coordination with other agencies, should continue to encourage and support U.S. scientists involved in atmospheric chemistry research to engage with underserved groups, in capacity-building activities, and in international collaborations.
Role of a National Center
Answering today’s science questions requires significant resources and expertise to develop, maintain, and operate an array of instruments, platforms and laboratory tools, as well as significant expertise and computational resources to develop and run complex weather, chemistry, and climate models. A national center can be an optimal approach for providing these observational and computational capabilities because (1) dedicated center staff with expertise are most efficient at maintaining these complex capabilities; (2) NSF competitive processes are suitable for making support of these abilities available to individual or groups of principal investigators (PIs); and (3) the center can help foster the collaborative research needed to identify and solve critical science and societal problems. A national center can provide these resources and expertise to investigators in the broader community, primarily those served directly by NSF, while at the same time contributing directly to scientific advancements. In addition, a national center can also bring the community together by hosting a large steady flow of visitors of all stages in their careers, facilitating collaborations, holding conferences and workshops, and playing a leading role in the production of scientific assessments.
The National Center for Atmospheric Research (NCAR) was established as a federally funded national center dedicated to achieving excellence in atmospheric science research, of which atmospheric chemistry is an essential part. Atmospheric chemistry research occurs within many divisions of NCAR, especially the Earth Observing Laboratory and the Atmospheric Chemistry Observations and Modeling (ACOM) Laboratory. ACOM serves as one of NCAR’s primary connections to the atmospheric chemistry community; yet that community regularly questions how well ACOM has been fulfilling this complete vision of its role.
Many on the Committee have observed that ACOM’s capabilities have diminished in the past decade or so—including departures of some prominent atmospheric chemists. This situation occurred at the same time that NCAR ACOM scientists have been pushed to provide instruments, measurements, and models for numerous projects, reducing the time for them to pursue their own research and/or development interests.
The Committee believes that it is essential for NCAR to find its unique role in atmospheric chemistry research, complementing and enhancing research by the broader community, and engaging individual PIs from universities, federal labs, and the private sector. NCAR can improve its standing within the atmospheric chemistry community by aligning its strategic vision with the role of a national center laid out above and with the original founding charter of NCAR. To achieve this vision, NCAR, in conjunc-
tion with NSF, will need to provide strong leadership, strategic allocation of resources, and guidance on balancing scientific excellence and community service.
In summary, the partnership between the competitively funded NSF Atmospheric Chemistry Program and the facility-funded NSF programs at NCAR needs to be strengthened; if this vision can be realized, NCAR can play a pivotal role in facilitating greater scientific advances across the atmospheric chemistry community.
Recommendation 7: The National Center for Atmospheric Research (NCAR), in conjunction with the National Science Foundation, should develop and implement a strategy to make NCAR a vibrant and complementary partner within the atmospheric chemistry community. This strategy should ensure that scientific leadership at NCAR has the latitude to set an energizing vision with appropriate personnel, infrastructure, and allocation of resources; and that the research capabilities and facilities at NCAR serve a unique and essential role to the NSF atmospheric chemistry community.
Similar to 30 years ago, the field of atmospheric chemistry research is in the midst of redefining its role in science and society. While atmospheric chemistry research has its foundations in the traditional disciplines of chemistry, physics, biology, geology, oceanography, engineering, and meteorology, as the field has grown it has become a robust area of basic science in and of itself.
In addition, atmospheric chemistry research is now clearly a vital part of building predictive capability for the Earth system and human impacts. Today, the field covers a wide swath of topics that integrate how an understanding of the fundamental chemistry of the atmosphere relates to the climate system, weather, ecosystems, and human society. These challenges involve nothing less than the health of our planet and its inhabitants. The Committee sees a deliberate shift in the field of atmospheric chemistry in the future to fully embrace its dual role—observing, learning, and discovering for the sake of fundamentally understanding the Earth system and its underlying chemical, physical, and biological processes, while also making major contributions to addressing those challenges that directly affect society. Atmospheric chemistry research alone will not solve the challenges of global climate change or the impacts of air pollution on human and ecosystem health, but these challenges will not be solved without the knowledge that comes from atmospheric chemistry research.
Moving in both of these directions will take effort, investment, and a willingness to adapt by NSF, other agencies, and the atmospheric chemistry community as a whole. After conversations with many members of our community during the course of this study, the Committee is convinced that we are ready for these challenges. The future of atmospheric chemistry research relies on the community to continue advancing our scientific knowledge and applying these findings to improve the world around us.