Why business as usual is just not good enough

ClairCity has been modelling emissions scenarios for each of their partner cities across Europe to figure out whether they are on track to meet air quality and carbon emission targets. Ahead of the Global Strike for Climate on September 20th and Zero Emissions Day on September 21st, we speak with our head modeller Kris Vanherle from TML in Belgium about ‘business as usual’ and whether that is enough for a future with clean air.


Why business as usual is not enough
Example of emissions modelling, showing how current pledges (business as usual) will almost certainly exceed 2° C warming. Source: World bank (2012). Turn down the heat. Why a 4˚C warmer world should be avoided.


So what is business as usual?

A business as usual (BAU) scenario is used as a benchmark to assess the impact of new policy measures in alternative emissions scenarios. Typically, the BAU scenario takes a central/conservative estimate of technological changes. Most importantly, they ONLY considers confirmed policy measures taken in the past that have a prolonged effect in the future.

A typical example in the case of air quality is emission standards of new cars (the so-called EURO-standards). While this policy measure is fully implemented, the impact takes some time to come into full effect because of the slow pace of vehicle replacement.

Apart from policy measures, a BAU scenario typically takes a central/conservative estimate in new technological evolutions – think electric vehicles. As well as a central/conservative estimate in non-technical trends such as population growth and/or Gross Domestic Product (GDP) growth. For variations in key trends it is possible to produce a range of figures, or a “bandwidth” for an expected future without further policy action.


What has your modelling revealed in ClairCity?

When assessing the BAU scenario in the ClairCity project, we’ve found that air quality will improve over time. This is due to existing policy measures coming into full effect, in combination with generic technological trends. These trends include the uptake of electric vehicles and lower domestic energy demand with new building techniques.

However, air pollution is not solved in full in the BAU scenario, which means that people will continue to suffer the health impacts. Even zero-emission electric vehicles cannot solve the problem due to particulate matter emitted from tyre and brake wear and tear. Moreover, the pace of improvement is slow and will continue to lead to exceedances of EU air quality limits in the immediate future. This leads to a twofold challenge: how to solve the immediate issue of exceedances of air quality standards; and how to develop new measures to improve air quality in the long-run.


What do you recommend we do about this?

On the basis of ClairCity findings, we recommend further (policy) action at two levels. Firstly, to ensure air quality is within current standards for human health, we need strong action to reduce pollution levels immediately. Examples of effective measures to address this are restricting access for polluting cars in city centres or banning the use of solid fuels for residential heating (and actually enforcing the ban!).

Secondly, action is also needed in the long-term as it is expected air quality standards will tighten further as evidence mounts for the adverse health effects from even low levels of pollution. To achieve compliance to more stringent targets and under continued pressure from concerned citizens, city authorities in particular will have to be more ambitious. This will require developing a more profound long-term strategy to fundamentally solve the problem of air pollution and carbon emissions.


What will that involve?

This will involve measures that have a strong yet gradual effect in the future and will impact the very core of the city. This means changing how we get around in the city, moving away from private car transport to more active travel, and requiring a fundamentally different strategy from city authorities in terms of public infrastructure investment. More ambitious urban planning and building codes for new buildings could also lead to zero-emissions of houses.

School Strike 4 Climate - Be Part of the Solution not the Pollution
School Strike 4 Climate Zagreb Demonstrations

We can see in the BAU scenario there is clear progress, but this is not enough to stop the impacts on human and planetary health.

ClairCity is urging for more action in the short-term to avoid air pollution exceedances and carbon emissions, and to achieve a future with clean air for all.




Zero Emissions Day happens each year on September 21st. It raises awareness of the need to act on air quality through a 24-hour Moratorium on the use of Fossil Fuels: http://zeroemissionsday.org/

The Global Climate Strike takes place from September 20-27th and is connected to School Strike 4 Climate (Fridays for Future). https://globalclimatestrike.net/

ClairCity has been producing resources for citizens wanting to act on these issues. Find them in our Take Action section or click on the cities above to find out how you can take action locally. We’ll be adding more resources in the coming months so stay tuned!