SDG Indicator 11.6.2

The following video gives a brief introduction to the United Nations Sustainable Development Goal indicator 11.6.2 (mean annual levels of fine particulate matter in cities, population-weighted) and the online platform for monitoring this indicator in Europe created by the SMURBS project. It also includes a discussion on the workflow approach, the sensitivity of the indicator to city definition, and how the tool is aimed at helping stakeholders to assess air quality in cities and exposure issues.

The video was first shown in December 2019 at the American Geophysical Union's Fall Meeting in San Francisco, California (see the presentation for more information).

What are SDG Indicators?

The United Nations (UN) is currently implementing the 2030 Agenda for Sustainable Development, which was adopted by all UN Member States in 2015 and includes 17 Sustainable Development Goals (SDGs) at its core, which seek to define and manage progress towards sustainable development through social inclusion, economic growth and environmental sustainability. The 17 SDGs are further defined into 169 related targets that are measured with 232 Indicators. The SDG indicators represent the means by which national governments can monitor achievement on and report progress toward the SDG targets. Each SDG indicator has one Custodian Agency mandated to compile monitoring guidelines for measuring and reporting on the indicator and to support national governments to set and report on national priorities and targets. Each indicator is classified by tier, based on the level of methodological development and overall data availability.

What is SDG 11.6.2?

SMURBS focuses on Indicator 11.6.2 of SDG goal 11, which aims to “make cities and human settlements inclusive, safe, resilient and sustainable.” Indicator 11.6.2 refers to the “Annual mean levels of fine particulate matter (e.g. PM2.5 and PM10) in cities (population weighted)” and works towards SDG target 11.6: “by 2030, reduce the adverse per capita environmental impact of cities, including by paying special attention to air quality and municipal and other waste management.” Indicator 11.6.2 is a tier 1 indicator, i.e. it has a conceptually clear, established methodology, standards available and data is regularly produced by countries, and the custodian agency is the World Health Organization (WHO).

What is particulate matter (PM)?

Particulate matter (PM) is an agreed upon indicator of air pollution (although there are many pollutants dictating air quality). Fine particles, i.e. PM_2.5, particles with a diameter of 2.5 microns or less, are able to penetrate deeply into the respiratory tract and shown to pose a major risk to health and increase the risk of morbidity and mortality [WHO]. In the urban setting, air pollution is a point of great concern as it relates to human health and presents city-specific complexities and can result in disproportionate impacts to subgroups of the city’s population. In Europe, although the air quality in many cities has improved over time, many urban areas still experience unsatisfactory air quality levels.

How does the UN measure Indicator 11.6.2?

The UN official approach for reporting on this indicator is to have the country’s national statistical offices or responsible agency (e.g. Ministries of Health or Environment) report a population weighted mean for the country, using the following algorithm:

C_n represents the estimated national annual mean concentration of PM_2.5 (measured in micrograms per cubic meter, μg/m³) of a specific sub-region, n, of the country, and P_n is the population of that region [UNSD].

What is SMURBS?

SMart URBan Solutions for air quality, disasters and city growth (SMURBS) is a project which integrates Earth Observation (EO) expertise to promote the ‘smart city’ concept and enhance urban resilience to specific urban pressures. SMURBS has received funding from the European Union’s Horizon 2020 Research and Innovation Programme, as the winning project of ERA-PLANET‘s transnational call under Strand 1 “Smart Cities and Resilient Societies”, and will be implemented between September 2017 and August 2020. For more information, please visit the website.

Why the SMURBS focus on cities?

An ever increasing number of European citizens lives in cities. Cities are a de facto concentration and population exposure hot spot. In urbanized areas of Europe, 90% of the population is exposed to harmful levels of air pollution, reports the European Environmental Agency. This is due to both local sources (industry, transport, fossil fuel combustion etc.) as well as transported anthropogenic or natural pollution (dust, wildfires etc). The SDG 11.6 target aims at reducing the actual PM_2.5 concentration and the consequent exposure.

One of SMURBS overarching goals is to address the SDG framework and specifically Goal 11. It also brings Earth Observation platforms (including satellites, in situ and models) and combines them with Smart City methods to create solutions for various urban pressures such as air pollution. Thus SMURBS, acknowledging the fact that most people live in cities and it is there where real opportunities lie to confront air pollution, has created this application utilizing Copernicus Services, a unique source of completely free and open high quality data (Copernicus Atmospheric Monitoring Service-CAMS and Copernicus Land Monitoring Service-CLMS), and the Joint Research Centre’s (JRC) Global Human Settlement Layer products, creating an elegant tool to i) provide a directly comparable product to the official UN indicator ii) highlight cities-hot spots that drive the Indicator iii) allow for comparisons, both in time and geographically as well as between different city definitions based on the Degree Of Urbanization concept (DEGURBA), i.e. Functional Urban Areas and Urban Centres (see section "Is there a harmonized city definition?") iv) demonstrate straightforwardly the sensitivity of the Indicator to this and the consequent policy implications.

How is the Indicator calculated?

The application, for the first approach, utilizes the Urban Centre (UC) concept based on the DEGURBA methodology. The population and city outline data are provided through the Global Human Settlement Layer (GHSL) and framework [EC,JRC], which incorporates human settlement information from satellite imagery and modeling and fine scale population data from censuses, but downscaled to a uniform grid of 1km2 to disregard administrative boundaries, thereby representing the presence and density of population (2015 reference year). An UC consists of non-diagonal contiguous grid cells with a population density of at least 1,500 inhabitants per km² or a density of built-up area greater than 50% per km², and a total population of at least 50,000 (see section "Is there a harmonized city definition?" for further details).

For the second approach, SMURBS follows the Functional Urban Area (FUA) concept [OECD & EC] that is provided by the Copernicus Land Monitoring Service (CLMS), where FUA is defined as the City and its commuting zone. The FUA methodology also follows the DEGURBA through the UC classification, but builds on it by overlaying the UCs onto Local Administrative Units (LAUs), which are then classified as Cities if at least 50% of the population in the LAU lives in one or more areas characterized as UCs. The commuting zone is in turn based on commuting patterns from Eurostat or country data. The population data for the FUA definition comes from CLMS Urban Atlas with 2012 as reference year.

For both approaches, the Air Quality (AQ) information is provided by the open and free data of the Copernicus Atmospheric Monitoring Service (CAMS). In particular, the application utilizes uses the CAMS regional ensemble reanalysis product, which includes annually averaged PM_2.5 concentrations throughout Europe with a spatial resolution of 0.1° x 0.1° (~11km) for 2014 – 2016 (validated data) and 2017-2018 (interim data, to be updated once available). These values are then masked using UC/FUA shapefiles defined above. Thus, a subset of the original array is created for both city definitions. All PM_2.5 values within each UC/FUA are then averaged to derive the concentration of PM_2.5 per city C_i, and are then multiplied with the respective UC/FUA population P_i. This is repeated for all of the remaining UCs/FUAs in a country. This provides the numerator, which, when divided by the total population P_total of the UCs/FUAs, results in a country-wide number that is equivalent to the UN indicator 11.6.2.

The EU and the Organization for Economic Cooperation and Development (OECD) have committed to and are developing a “global, people-based definition of cities and settlements” to be delivered to the UN Statistical Commission [European Commission]. SMURBS is exploring the sensitivity of Indicator 11.6.2 based on two separate, but EC endorsed definitions of cities that are directly linked to this global, harmonized definition: the Urban Centre (UC) based on the DEGURBA classification and the Functional Urban Area (FUA) concept that expands on DEGURBA and the UC by including commuting activity.

What is the Degree of Urbanization (DEGURBA)?

The DEGURBA is a classification that indicates the character of an area. The latest update of the classification is based on 2011 population grid and the 2014 Local Administrative Units (LAU) boundaries. The next major update will be based on 2020 Census results. Based on the share of local population living in urban clusters and in urban centres, it classifies LAU2 or communes into three types of area: Cities (densely populated areas) Towns and suburbs (intermediate density areas) Rural areas (thinly populated areas).

What is an Urban Centre?

Under JRC's Global Human Settlement Layer initiative, the DEGURBA methodology was expanded upon. The DEGURBA classifications were re-calculated using both population density criteria and density of built-up area derived from primary databases and not LAU data. In particular, an Urban Centre (UC) consists of contiguous grid cells with 1) population density of at least 1,500 inhabitants per km² OR 2) density of built-up area greater than 50% per km² AND 3) at least 50,000 total population. This definition is completely agnostic to national definitions of LAUs and is therefore more objective.

What is a Functional Urban Area?

The FUA methodology is yet another expansion of the UC implemented in two steps. Instead of arbitrarily assigning the "City" classification to a LAU, the LAU is overlaid over the UC database. Based off the type of grid cells (UC or not) the majority of the LAU population resides in, the LAU may receive the "City" classification. The second step for arriving at the FUA is including the commuting zone (based on commuting patterns from Eurostat or country data) of the aforementioned City to its overall extent.

When the user first enters the platform, there are many ways to start visualizing the Indicator data, beginning with the European viewpoint, zooming in to the country and eventually the city level.

To initiate exploration, the user can select the city definition (Functional Urban Area-FUA or Urban Centre-UC) and year of interest to view the population -weighted, average, annual particulate matter concentrations in cities and countries, i.e. the SDG 11.6.2 Indicator. Once a selection is made, the map, City Data and Country Data tables and overview chart will become populated with the indicator data across Europe and over time (from 2014-2018). The Overview chart presents indicator 11.6.2 for every European country (37 in total), ranked from highest to lowest values along with the EU Standard and WHO Guideline for PM_2.5. The user may remove annual data by selecting the year that is no longer of interest. The Capitals of Europe chart shows the same information, just for the capital city of every European country, once more, per city definition.

As regards the map view, each country receives a color based on its indicator 11.6.2 performance (through the bottom right color legend). The cities (either FUA or UC depending on user’s initial selection) are outlined within each country, and assigned their own color, based on the city’s value for the annual concentration average. This visualization allows a quick view of how European countries are performing in relation to the indicator, how this is sensitive to the city definition and moreover, whether cities that drive the national value exist.

Finally, regarding the City Comparison Chart, after selecting a specific city, the City and Country Data tables will highlight the city and respective country to allow for instant evaluation of the place of interest. The tables, whose columns can be ranked when column title is selected, display related information to the annual indicator values, such as population or number of cities within a country. Through selecting a city or country, the user can press “Add To Chart” and the Comparison chart will become populated. The Comparison chart is entirely interactive and a user can select any desired city or country to build the chart, allowing for a custom-made comparison. Again, the European value (where Europe is treated as one single geographical area, or “country” containing more than 750 FUAs and 800 UCs) or previously added country or city averages can be removed from the chart by pressing the corresponding button at the top of the chart.