Illustrative: atmospheric layers at the limb, jet tracers and an aerosol plume lofted and sheared downwind

Risk Academy, led by the Nexus Consortium · Course catalogue · Earth and Environmental Sciences

Climate and Ocean Sciences

Atmosphere and air chemistry

Atmosphere and air chemistry, taught twice over: as the working methods of the field and as its frontier since 2024, with labs on the Academy's tools, open data and the Nexus Standards.

Core course Frontier course

The discipline

01Core course · L2 Intermediate

Atmosphere and air chemistry: foundations and practice

This area covers the composition and chemistry of the atmosphere: aerosols, ozone, reactive gases and greenhouse gases, their sources and transport, and their effects on climate, air quality and health.

Level
L2 Intermediate
Study time
about 24 hours (planning estimate)
Status
Planned
Prerequisites
An L1 course in the area, or an entry review

Why now

Geostationary air quality sounders now observe pollution hour by hour: NASA TEMPO over North America since 2023 joins Sentinel-5P TROPOMI daily global retrievals and Korea's GEMS, so city exposure can be tracked through the day rather than once at overpass. World Health Organization, WHO global air quality guidelines, 2021

Learning outcomes

  1. Define radiative forcing and the other key terms of the discipline and use them correctly in a written case
  2. Explain greenhouse gases and their monitoring and aerosols, clouds and radiative forcing with a worked example and its source
  3. Apply the discipline's method to a documented case and explain each result with its source
  4. Analyse a named case against tropospheric ozone and photochemical smog, stating evidence, date and limits

Modules

  1. Greenhouse gases and their monitoring
    • Greenhouse gases and their monitoring
    • Aerosols, clouds and radiative forcing
    • Tropospheric ozone and photochemical smog
  2. Stratospheric ozone and the Montreal Protocol
    • Stratospheric ozone and the Montreal Protocol
    • Particulate matter sources and transport
    • Atmospheric composition forecasting (CAMS)
  3. Wildfire and dust emissions
    • Wildfire and dust emissions
    • Methane and short-lived climate forcers
    • Satellite monitoring of atmospheric composition
  4. Lab: the discipline's method
    • A city's emission rate divided by the air that carries it away, wind speed times mixing height times width, gives its fine particle concentration above the regional background; an exposure-response function turns the concentration into a relative risk; the attributable share of baseline deaths is the quantity an air quality standard is written against.
    • Work the method through a documented case and explain each result
    • Read the method's sources and stated values

Labs with Academy tools

Open data

Assessment

  • 40%Lab recordWork the discipline's method through a documented case and explain each result with its source and date
  • 40%Case memoApply the discipline's methods to a named place or organisation, stating evidence and limits
  • 20%Key terms checkShort answers on the key terms, marked against the definitions

Delivery

  • Self-paced online, with the labs in the browser
  • Cohort study over six to eight weeks, with a weekly lab review
  • Co-delivered with a partner institution, inside its own courses

Partner on this course

  • Co-teach a module and bring a current case from your work
  • Host a cohort for your learners, with your own schedule and review
  • Contribute a lab: a dataset your institution publishes openly, or a model
  • Review the course content and its references before it opens
  • Translate the course and adapt its cases to your region

How institutions and experts take part

In the Academy LMS

Course on the learning platform
Intermediate, 4 topics
Cohort group
A community group for each cohort of learners
Achievement
Recorded on completion of the assessed work

References

  1. Burnett et al., Global estimates of mortality associated with long-term exposure to outdoor fine particulate matter, 2018
  2. World Health Organization, WHO global air quality guidelines: particulate matter, ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide, 2021
  3. van Donkelaar et al., Monthly global estimates of fine particulate matter and their uncertainty, 2021
02Live map

Hazards and exposure in Brazil

Flood water, active fires and surface heat beside population and night-time lights, over Brazil.

The interactive map needs JavaScript; the layer list and sources are below.

Layers 3

Hazards and exposure

Latest available

NASA GIBS / EOSDIS · ASTER GDEM (METI, NASA) · Blue Marble (NASA) · © OpenStreetMap contributors (ODbL) · Natural Earth

Loading the latest NASA imagery.

Drag to move. Ctrl or ⌘ and scroll, pinch or the buttons to zoom; hover for the values under the pointer; reset returns to the region.

Hazards and exposure, framed on Brazil.Satellite and model products as NASA publishes them, each with its own date. They are indicators, not assessments of any place.

Data: NASA GIBS · ASTER GDEM · Blue Marble · © OpenStreetMap contributors · Natural Earth · NASA EONET · U.S. Geological SurveySources and licences

  • We acknowledge the use of imagery provided by services from NASA's Global Imagery Browse Services (GIBS), part of NASA's Earth Science Data and Information System (ESDIS). Colours redrawn from the published colour map; values averaged into H3 cells where shown (modified). NASA open data
  • We acknowledge the use of imagery provided by services from NASA's Global Imagery Browse Services (GIBS), part of NASA's Earth Science Data and Information System (ESDIS). Colours redrawn from the published colour map; values averaged into H3 cells where shown (modified). NASA open data
  • VIIRS near-real-time products (flood, land surface temperature, snow cover, corrected reflectance), NASA LANCE; imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into H3 cells where shown (modified). NASA open data
  • NASA Fire Information for Resource Management System (FIRMS), VIIRS 375 m active fire product, NASA LANCE; vector tiles via NASA GIBS. Colours redrawn from the published colour map; values averaged into H3 cells where shown (modified). NASA open data
  • Center for International Earth Science Information Network (CIESIN), Columbia University. 2018. Gridded Population of the World, Version 4 (GPWv4): Population Density, Revision 11. NASA Socioeconomic Data and Applications Center (SEDAC). Licensed under CC BY 4.0. Colours redrawn from the published colour map; values averaged into H3 cells where shown (modified). doi:10.7927/H49C6VHW. CC BY 4.0
  • VIIRS Black Marble night-time lights, NASA Goddard Space Flight Center; distributed by the NASA Level-1 and Atmosphere Archive and Distribution System (LAADS DAAC); imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into H3 cells where shown (modified). NASA open data
  • MODIS and VIIRS atmosphere products, NASA LANCE and LAADS DAAC; imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into H3 cells where shown (modified). NASA open data
  • ASTER GDEM is a product of METI and NASA (ASTER Global Digital Elevation Model V003, NASA LP DAAC); imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into H3 cells where shown (modified). Cite as: NASA/METI/AIST/Japan Spacesystems and U.S./Japan ASTER Science Team (2019). ASTER Global Digital Elevation Model V003. doi:10.5067/ASTER/ASTGTM.003. NASA open data
  • Made with Natural Earth. Free vector and raster map data @ naturalearthdata.com. Public domain
  • © OpenStreetMap contributors (ODbL), via NASA GIBS (coastlines, boundaries, roads and place names). Colours redrawn from the published colour map; values averaged into H3 cells where shown (modified). ODbL
  • Blue Marble, NASA Earth Observatory; imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into H3 cells where shown (modified). NASA open data
  • Context on the globe and flat map: coastlines, boundaries, roads and place names from NASA GIBS reference layers (OpenStreetMap data, ODbL, © OpenStreetMap contributors); Blue Marble imagery as an optional base; 3D terrain and the elevation read-out from the ASTER GDEM elevation colour index (5 m to 200 m classes, exaggerated for legibility). Boundaries are drawn as published and imply no position on any territory.
  • Globe: MapLibre GL JS 6.9.1, BSD-3-Clause, © MapLibre contributors.
  • Live events: NASA Earth Observatory Natural Event Tracker (EONET); events are indicative and keep their original source links.
  • Live: NASA EONET Events are indicative, not authority warnings.
  • Live: U.S. Geological Survey Events are indicative, not authority warnings.
  • NASA GIBS: We acknowledge the use of imagery provided by services from NASA's Global Imagery Browse Services (GIBS), part of NASA's Earth Science Data and Information System (ESDIS).
  • River discharge forecast, 30 days with range (GloFAS via Open-Meteo): Contains modified Copernicus Emergency Management Service information 2026; not a flood warning.
  • Weather data by Open-Meteo.com (https://open-meteo.com/), licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/).
  • Optional layers (10 sources in the layer list: live, forecast, observed and context) print their provider credit on the map and here when switched on; forecasts are model output and derived indices are estimates.

Layers and dates

  • Flood water, 3-day composite: VIIRS Global Flood Product, NASA LANCE · 14 Oct 2026
  • Active fires and thermal anomalies: VIIRS NOAA-20 375 m (FIRMS), NASA LANCE FIRMS · 13 Oct 2026
  • Population density, 2020: Population: CIESIN, Columbia University, Gridded Population of the World v4.11 (2018), NASA SEDAC, CC BY 4.0 · static
  • Land surface temperature, day, 8-day composite: VIIRS NOAA-20 Level 3, 8-day, NASA LANCE · 14 Sep 2026
  • Night-time lights, daily: VIIRS Black Marble (VNP46A2), NASA LAADS DAAC · 12 Oct 2026
  • Aerosol optical depth, daily: VIIRS NOAA-20 Deep Blue AOD, NASA LANCE · 13 Oct 2026

03How learning runs

How learning runs, as a process you can run

Select a scenario and press Play: course, pathway, practice, faculty, cells and record.

04What is changing

What is changing, with standards and evidence

Atmosphere and air chemistry: frontier methods

The methods, data, tools and studies that changed atmosphere and air chemistry between 2024 and 2026, taught by reproducing them on open data.

Level
L3 Advanced
Study time
about 28 hours (planning estimate)
Status
Planned
Prerequisites
Atmosphere and air chemistry: foundations and practice; Working knowledge of a scripting language (Python or R) for the labs

Why now

Geostationary air quality sounders now observe pollution hour by hour: NASA TEMPO over North America since 2023 joins Sentinel-5P TROPOMI daily global retrievals and Korea's GEMS, so city exposure can be tracked through the day rather than once at overpass. World Health Organization, WHO global air quality guidelines, 2021

Learning outcomes

  1. Explain what changed in atmosphere and air chemistry since 2024 and cite the studies, data or rules behind each change
  2. Reproduce satellite retrievals of trace gases and aerosols on open data and state the uncertainty of the result
  3. Evaluate a 2024 to 2026 study: its question, data, method, limits and what it changes for practice
  4. Design an analysis that combines a frontier method with the faculty's instruments, and justify each choice

Modules

  1. Satellite retrievals of trace gases and aerosols
    • TROPOMI on Sentinel-5P: NO2, SO2, CO, CH4 and HCHO columns, averaging kernels and a priori profiles
    • TEMPO and GEMS hourly geostationary columns and the diurnal cycle of NO2
    • From column to surface: boundary-layer assumptions and their error budget
  2. Data assimilation and reanalysis
    • The CAMS reanalysis and the CAMS global and European forecasts
    • 4D-Var and ensemble Kalman filters for atmospheric composition
    • Emission inversion: top-down estimates of NOx and methane sources
  3. Low-cost sensors and calibration
    • Optical particle counters, humidity artefacts and drift
    • Collocation and correction models (the US EPA PurpleAir correction)
    • Network quality control and uncertainty statements
  4. Source apportionment
    • Positive matrix factorisation (EPA PMF) on speciated PM2.5
    • Receptor and dispersion models compared
    • Policy questions: how much of a city's PM2.5 is local
  5. Machine learning emulators of chemistry
    • Emulating chemical mechanisms and transport for speed
    • Physics constraints, conservation and out-of-distribution failure
    • Evaluating an emulator against the reference model
  6. Reproduction lab
    • Extend the discipline's method with one frontier method and compare its results
    • State the uncertainty and the limits of the result
    • Peer review against a shared checklist
  7. Technology that helps and the risks it carries
    • Machine learning forecasting, carbon dioxide removal and climate data infrastructure.
    • The governance of solar radiation modification and the integrity of carbon removal.

Labs with Academy tools

Open data

Assessment

  • 50%Method reproductionReproduce one frontier method on open data and state the uncertainty of the result
  • 30%Study reviewA critical review of a 2024 to 2026 study: question, data, method, limits, what it changes
  • 20%Peer reviewReview two other learners' reproductions against a shared checklist

Delivery

  • Self-paced online, with the labs in the browser
  • Cohort study over six to eight weeks, with a weekly lab review
  • Co-delivered with a partner institution, inside its own courses

Partner on this course

  • Co-teach a module and bring a current case from your work
  • Host a cohort for your learners, with your own schedule and review
  • Contribute a lab: a dataset your institution publishes openly, or a model
  • Review the course content and its references before it opens
  • Translate the course and adapt its cases to your region

How institutions and experts take part

In the Academy LMS

Course on the learning platform
Expert, 7 topics
Cohort group
A community group for each cohort of learners
Achievement
Recorded on completion of the assessed work

References

  1. World Health Organization, WHO global air quality guidelines, 2021
  2. Atmospheric Measurement Techniques, Development and application of a United States-wide correction for PM2.5 data collected with the PurpleAir sensor (Barkjohn et al.), 2021
  3. US EPA, Positive Matrix Factorization model for environmental data analyses, 2024
  4. GEOS-Chem community, GEOS-Chem chemical transport model, 2025
  5. Burnett et al., Global estimates of mortality associated with long-term exposure to outdoor fine particulate matter, 2018
  6. van Donkelaar et al., Monthly global estimates of fine particulate matter and their uncertainty, 2021
05Take part

Take part in the work

Start from who you are.

06Questions

Questions, answers and key terms

Is the course free?
Yes. Every course and learning material of Risk Academy, led by the Nexus Consortium, is free to study, self-paced or with a cohort. Ordinary participation has no fee; paid work, internships and fellowships are separate arrangements.
What does completing a course give me?
A completion record: the course, its version, the date and what was assessed, private by default and shared by you. It stacks into discipline, department and programme achievements. A record states what was studied and assessed and does not certify competence; it is not a licence, a professional title or an employment status.
Where do the data and the places come from?
Every faculty teaches on a twin of a real place built from open data; each layer carries its provider, licence and date, and every result on the Academy states its source. Maps and figures are indicators for teaching, never an assessment of a place.
How do I take part beyond the course?
Form a competence cell of three to seven people, study a shared pathway, take a supervised assignment in the National Working Groups, or bring a cohort from your institution. For organisations.

Key terms

Term

Radiative forcing

The change in the Earth's energy balance caused by a change in a driver such as a greenhouse gas or aerosol.

Term

Aerosol

A suspension of fine solid or liquid particles in the air, from dust and sea salt to smoke and sulphate.

Term

Short-lived climate forcer

A substance such as methane, black carbon or tropospheric ozone that affects climate over years to decades.

Term

Stratospheric ozone layer

The ozone between about 15 and 35 kilometres that absorbs most of the Sun's ultraviolet radiation.

ReportsContribute

Contribute evidence from this page.

Reports is the Consortium's quarterly publication. What you know about this subject can become evidence, a case or a correction in the next edition, credited to you and published under CC BY 4.0 where it is your own work.

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