We can cut emissions in half by 2040 – but only if we build smarter cities

Shanghai's Jinmao Tower, under construction in 2009. Image: Getty.

As a planet, we have some serious climate targets to meet in the coming years. The Paris Agreement, signed by 192 countries, set an aspirational goal of limiting global warming to 1.5ᵒC. The United Nations Sustainable Development Goals, set to be achieved by 2030, commit the world to “take urgent action” on climate change.

All this will require ridding our economies of carbon. If we’re to do so, we need to completely rethink our cities.

The UN’s peak climate body showed in its most recent report that cities are crucial to preventing drastic climate change. Already, cities contribute 71 per cent to 76 per cent to energy-related carbon emissions.

In the Global South, energy consumption and emissions in urban areas tend to be way higher than those in rural areas. Future population growth is expected to take place almost entirely in cities and smaller urban settlements. Unfortunately, those smaller centres generally lack the capacity to properly address climate change.

China’s “New-type Urbanisation Policy” aims to raise its city populations from 54.2 per cent in 2012 to 60 per cent in 2020. This will mean building large urban infrastructure projects, and investing trillions of dollars into new developments. Meanwhile, India’s sheer volume of urbanisation and infrastructure needs are phenomenal.

The problem with infrastructure

Infrastructure contributes to greenhouse gas emissions in two ways: through construction (for example, the energy footprints of cement, steel and aluminium used in the building process) and through the things that go on to use that infrastructure (for example, cars or trains using new roads or tracks).

In a recent study, my colleagues and I have shown that the design of today’s transportation systems, buildings and other infrastructure will largely determine tomorrow’s CO2 emissions.

Less of this, please. Image: Getty.

But by building climate-smart urban infrastructure and buildings, we could cut future emissions in half from 2040 onwards. We could reduce future emissions by ten gigatonnes per year: almost the same quantity currently being emitted by the United States, Europe and India put together (11 gigatonnes).

We assessed cities’ potential to reduce emissions on the basis of three criteria: the emissions savings following upgrades to existing infrastructure; emissions savings from using new, energy-efficient infrastructure; and the additional emissions generated by construction.

In established cities, we found that considerable progress can be made through refurbishment of existing infrastructure. But the highest potential is offered by construction of new, energy-efficient projects from the beginning. The annual reductions that could be achieved by 2040 by using new infrastructure is three to four times higher than that of upgrading existing roads or buildings.

With this in mind, governments worldwide must guide cities towards low-carbon infrastructure development and green investment.


Urbanisation is about more than megacities

Significant opportunities exist to promote high-density living, build urban set-ups that mix residential, work and leisure in single spaces, and create better connectivity within and between cities. The existing window of opportunity to act is narrowing over time, as the Global South develops rapidly. It should not be missed.

Besides global megacities such as Shanghai and Mumbai, smaller cities must also be a focus for lowering emissions. Studies have shown a paradox for these places: the capacity for governance and finance are lower in the smaller cities, despite the fact that the majority of future urban populations will grow there, and they will expand quicker than their larger cousins.

We must give up on our obsession with megacities. Without building proper capacity in mid- and small-sized cities to address climate solutions, we cannot meet our climate goals.

Perhaps most important is raising the level of ambition in the existing climate policies in cities of all sizes, making them far-reaching, inclusive and robust. Despite the rhetoric, the scale of real change on ground from existing cities climate actions are unproven and unclear.

Existing cities’ climate mitigation plans and policies, such as in Tokyo, London, Bangkok, and activities promoted by networks such as ICLEI, C40, Covenant of Mayors for Energy and Environment are a good start; they must be appreciated but further strengthened.

But, to further support these good ideas, the world urgently needs support measures for urban mitigation from local to global levels together with a tracking framework and agreed set of indicators for measuring the extent of progress towards low-carbon future.

Only if we start with cities, big and small, will we manage to limit warming to 1.5°C.The Conversation

Shobhakar Dhakal is associate professor at the Asian Institute of Technology.

This article was originally published on The Conversation. Read the original article.

 
 
 
 

How bad is the air pollution on the average subway network?

The New York Subway. Image: Getty.

Four more major Indian cities will soon have their own metro lines, the country’s government has announced. On the other side of the Himalayas, Shanghai is building its 14th subway line, set to open in 2020, adding 38.5 km and 32 stations to the world’s largest subway network. And New Yorkers can finally enjoy their Second Avenue Subway line after waiting for almost 100 years for it to arrive.

In Europe alone, commuters in more than 60 cities use rail subways. Internationally, more than 120m people commute by them every day. We count around 4.8m riders per day in London, 5.3m in Paris, 6.8m in Tokyo, 9.7m in Moscow and 10m in Beijing.

Subways are vital for commuting in crowded cities, something that will become more and more important over time – according to a United Nations 2014 report, half of the world’s population is now urban. They can also play a part in reducing outdoor air pollution in large metropolises by helping to reduce motor-vehicle use.

Large amounts of breathable particles (particulate matter, or PM) and nitrogen dioxide (NO2), produced in part by industrial emissions and road traffic, are responsible for shortening the lifespans of city dwellers. Public transportation systems such as subways have thus seemed like a solution to reduce air pollution in the urban environment.

But what is the air like that we breathe underground, on the rail platforms and inside trains?

Mixed air quality

Over the last decade, several pioneering studies have monitored subway air quality across a range of cities in Europe, Asia and the Americas. The database is incomplete, but is growing and is already valuable.

Subway, Tokyo, 2016. Image: Mildiou/Flickr/creative commons.

For example, comparing air quality on subway, bus, tram and walking journeys from the same origin to the same destination in Barcelona, revealed that subway air had higher levels of air pollution than in trams or walking in the street, but slightly lower than those in buses. Similar lower values for subway environments compared to other public transport modes have been demonstrated by studies in Hong Kong, Mexico City, Istanbul and Santiago de Chile.

Of wheels and brakes

Such differences have been attributed to different wheel materials and braking mechanisms, as well as to variations in ventilation and air conditioning systems, but may also relate to differences in measurement campaign protocols and choice of sampling sites.

Second Avenue Subway in the making, New York, 2013. Image: MTA Capital Construction/Rehema Trimiew/Wikimedia Commons.

Key factors influencing subway air pollution will include station depth, date of construction, type of ventilation (natural/air conditioning), types of brakes (electromagnetic or conventional brake pads) and wheels (rubber or steel) used on the trains, train frequency and more recently the presence or absence of platform screen-door systems.

In particular, much subway particulate matter is sourced from moving train parts such as wheels and brake pads, as well as from the steel rails and power-supply materials, making the particles dominantly iron-containing.


To date, there is no clear epidemiological indication of abnormal health effects on underground workers and commuters. New York subway workers have been exposed to such air without significant observed impacts on their health, and no increased risk of lung cancer was found among subway train drivers in the Stockholm subway system.

But a note of caution is struck by the observations of scholars who found that employees working on the platforms of Stockholm underground, where PM concentrations were greatest, tended to have higher levels of risk markers for cardiovascular disease than ticket sellers and train drivers.

The dominantly ferrous particles are mixed with particles from a range of other sources, including rock ballast from the track, biological aerosols (such as bacteria and viruses), and air from the outdoors, and driven through the tunnel system on turbulent air currents generated by the trains themselves and ventilation systems.

Comparing platforms

The most extensive measurement programme on subway platforms to date has been carried out in the Barcelona subway system, where 30 stations with differing designs were studied under the frame of IMPROVE LIFE project with additional support from the AXA Research Fund.

It reveals substantial variations in particle-matter concentrations. The stations with just a single tunnel with one rail track separated from the platform by glass barrier systems showed on average half the concentration of such particles in comparison with conventional stations, which have no barrier between the platform and tracks. The use of air-conditioning has been shown to produce lower particle-matter concentrations inside carriages.

In trains where it is possible to open the windows, such as in Athens, concentrations can be shown generally to increase inside the train when passing through tunnels and more specifically when the train enters the tunnel at high speed.

According to their construction material, you may breath different kind of particles on various platforms worldwide. Image: London Tube/Wikimedia Commons.

Monitoring stations

Although there are no existing legal controls on air quality in the subway environment, research should be moving towards realistic methods of mitigating particle pollution. Our experience in the Barcelona subway system, with its considerable range of different station designs and operating ventilation systems, is that each platform has its own specific atmospheric micro environment.

To design solutions, one will need to take into account local conditions of each station. Only then can researchers assess the influences of pollution generated from moving train parts.

The ConversationSuch research is still growing and will increase as subway operating companies are now more aware about how cleaner air leads directly to better health for city commuters.

Fulvio Amato is a tenured scientist at the Spanish National Research CouncilTeresa Moreno is a tenured scientist at the Institute of Environmental Assessment and Water Research (IDAEA), Spanish Scientific Research Council CSIC.

This article was originally published on The Conversation. Read the original article.