Climate-neutral cities

The world has not achieved its short-term objectives: instead of the intended reduction in CO2-emissions, global emissions increased by 1.6 % in 2017 and by 2.7% in 2018. The main reasons are increasing car ownership and use of coal. The chart below shows that all continents, except Europe, are responsible.

Global carbon emissions in 2018 are set to hit an all-time high of 31.1 billion tons. Source: University of East Anglia

From a scientific point of view, the relationship between global warming and greenhouse gas emissions above the critical level of 350 ppm (parts per million) is undisputed. The current global emission level is 415 ppm. It has also been proven that global warming higher than 1,5 degree from pre-industrial temperatures will be disastrous for the earth. The global temperature has already risen by 1oC above the pre-industrial level, leaving us a mere 0.5oC until 2050.

A climate neutral building: The Edge Amsterdam, headquarters of Deloitte – Photo Deloitte

Governments at all levels emphasize the urgency of reducing CO2-emissions. Many of them intend to reduce their emissions by half by 2030, giving themselves a 10 year window. There are well-founded doubts about the feasibility of this intention. Authoritative institutions such as Bloomberg and Arcadis predict, based on their knowledge of current trends and strategic plans of commercial actors, that by 2050 the use of carbon energy will be reduced by only 50%. Please note that the related urban policies will be discussed later. First, a recapitulation of the problem , so we have a proper framework for the solution.

Climate-neutral cities is the third in a series of short essays: Future cities. Smart by default. Humane by choice. Making cities more humane means finding a balance between sustainability, social justice and quality of life. This requires far-reaching choices. Once these choices have been made, it should go without saying that we will use smart technologies for their realization.
The already published essays are:
Introduction: Future Cities. Smart by default. Humane by choice
Healthy cities
Resilient cities

Where are we talking about?

In the first place, we should not focus our attentions solely on CO2-emissions, as there are other greenhouse gasses that should to be considered too. Each of these gases is created by human activities and contributes to global warming. 76% of the heating over a 100-year period is caused by carbon dioxide (CO2) that comes from burning fossil fuels, land use (deforestation, plowing), and industrial processes (62, 11 and 3% of total heating). Methane (CH4) comes from biomass burning, rice fields and cattle (16% of total heating). Nitrous oxide (N2O) comes from fertilizers (6% of total heating), and fluorinated gases (f-gasses) come from refrigerants and industrial processes (2% of total heating).

Secondly, we should look at the sectors responsible for global warming. This aligns with the groundbreaking work of the Drawdown project.

Graph: Drawdown project

Five major sectors are the main causes of the problem. These sectors are electricity, food & land use, industry, transportation, buildings and homes. The burning of coal, oil, and natural gas to generate electricity is the largest source of global emissions, but the sector food and land use follows second.


After the energy sector, the cement industry is the second largest source of CO2. It accounts for 5-6% of all anthropogenic emissions. Researchers in the US have developed a method for cement production that does not generate CO2 – emissions. They estimate that the new production process will also be cheaper than the existing process. Solar energy is used directly to heat and melt the limestone over 800oC. Next, the substance is electrolyzed resulting in lime with carbon monoxide and oxygen as by-products. However, the process still requires a lot of heat.

Thirdly, we must realize that the earth itself is capable of absorbing 55% of the greenhouse gas emissions, particularly the oceans and the forest lands. The creation of new forests, the restoration of carbon-rich soils in agricultural areas and the restoration of coastal ecosystems will contribute to increase the absorption capacity that has been destroyed by deforestation.

Last but not least, the impact of global warming differs between and within countries.  According to a study recently published in the Proceedings of the National Academy of Sciences, poorer countries have suffered more because they are already located in the warmest parts of the world, such as Africa, South Asia, and Central America. On the other hand, global warming in moderate climate zones can lead to higher productivity, agriculture yields and well-being. For example, global warming in Norway has increased the national product per capita by 34%, while India has experienced 31% less growth compared to the growth without global warming. Canada and Russia are supposed to benefit as well.

This does not mean that richer nations as a whole benefit. Different parts of the US are already experiencing extreme weather conditions, like hurricanes or droughts. The warmer regions in the south of the US will also suffer from high emissions, resulting in a huge shift of prosperity to the north and west, increasing the country’s economic inequality.

Country-level economic impact of global warming – Image National Academy of Sciences

City actions

Discussing policy making at city level (‘city actions’) cannot be done without mentioning the exemplary work of the C40 Cities Climate Leadership Group, which has been around for more than 12 years. The group represents 96 of the world’s largest cities, representing a total number of more than 650 million inhabitants. These cities include London, New York, Paris, Amsterdam and Rotterdam.

The C40 cities are determined to make an important contribution to the success of the Paris Agreement and have detailed plans to do so. It is estimated that by 2050, if we do not take any preventive action, global warming-related disasters will put 1.3 billion people and $158 trillion worth of assets at risk. Most cities have already started reporting observable climate changes. The graph below shows the nature of these changes.

Maximum warming of 1.5oC requires that between now and 2100 C40 cities limit emissions to 22 GtCO2e. In addition, they must contribute to global negative emissions, which means that 31 GtCO2e has to be removed from the atmosphere in the second half of this century.

Effects of climate change as reported by C40 cities – Picture C40

The C40 has published a handful of solid reports – along with Arup and McKinsey – that provide a roadmap towards the 1,5oC trajectory. Elsewhere I have summarized the content of these reports, including the targets for cities in different parts of the world in reducing their emissions and removing CO2 from the air (CCS or negative emissions). 

Until recently, these reports focused on the greenhouse gases produced within the city area. In the latest report The future of urban consumption in a 1,5oC world (June 2019) consumption-based emissions were also considered. These emissions are the ones related to what urban business and citizens use, eat, and wear, and how these things are made and transported. 85% of the emissions associated with the consumption of goods and services within their boundaries are imported from elsewhere.

As mentioned above, the contribution of city actions to reducing global warming includes both emissions produced in the city, and emissions resulting from consumption by local actors, regardless of where they are produced. These actions reduce total emissions by 51% at best. Of that 51%, only 20% is linked to direct actions by the municipal authorities. For the other 80%, other local actors must take the initiative, with or without stimulation, coordination or subsidies from municipal authorities.

So far, these numbers are not achieved. An inventory of the Carbon Disclosure Project showed that of the 696 cities, only 43 cities are taking drastic measures, including 24 North American Cities, like Toronto, Boston and New York, and European cities like Barcelona, Reykjavik, London and Paris.

Millions of people all over the world are involved in ‘city actions’. They decide to have fewer children, to enable girls to study, to use energy-saving devices for cooking, to cover their roofs with solar panels, to invest in isolation and heat-pumps, and to change their consumption pattern. However, the impact of these decisions is nothing compared to the decisions that have to be made at corporate level. In a thought-provoking article Derrick Jensen remembers us of the fact that in the US individual energy consumption was less than 25% of total energy use between 1994 – 2009, that 90% of fresh water goes to agriculture and industry and residential, and that government office waste comprises only 3% of total waste production. He concludes that if all Americans did everything to reduce their carbon footprint – amongst others driving cars and going vegan – US emissions would be reduced by only 22%.

A recent report from the Carbon Disclosure Project reveals that 100 oil and gas producing global corporates are responsible for 71% of all greenhouse gas emissions since 1988. These companies hold the most important key to reducing the production of carbon fuels. It is suggested that in the years following the signing of the Paris agreement, financial institutions have invested more than $ 478 billion in the exploitation of coal.

In order to realize the 51% contribution of city actions to the decrease of greenhouse gasses, municipal authorities have a vast informative, coordinative, supportive and legislative task, as apparent in the example of Amsterdam, to be found below. The realization of these plans depends on the level of agreement that municipal authorities will reach with stakeholders (ideally as many as possible), varying from corporations to (groups of) citizens.

The Amsterdam road map

Amsterdam recently published its own road map to strengthen the movement towards climate neutrality, and to stimulate the participation of as many residents, companies and institutions as possible. There is a distinction between four sectors, each with a significant share of CO2 emissions and therefore also their reduction: built environment (28%), traffic at the local road network (9%), energy (51%) and industry and port (11%). The municipality indicates that it only has a limited role in the field of energy supply, industry and port, but that it plays a major role in the built environment and with regard to mobility. The latter also applies to the municipal organization.

Photo: Marieke van Doornik – Alderman urban development and sustainable development – photo city of Amsterdam

The role of municipal authorities

The C40 has extensively documented how city action can help reduce greenhouse gas emissions. Many of the C40 cities have published their own plans.

The graph below illustrates the ambitions of the cities united in C40.

The contribution of city actions to the reduction of the most important sources of greenhouse gases is discussed below, with emphasis on the role of municipal authorities. The perspective of the humane city will also appear here, because it is not inconceivable that policies in favor of reducing greenhouse gas emissions will widen the gap between the poor and the rich. For example, 78.9% of grants for electric cars in the US went to people with an annual income of over $100,000.


The reduction of the greenhouse effect is usually related to the replacement of carbonaceous fuels by renewable sources of energy. The Drawdown report refers to a large number of additional options. Below, you will find a number of sources that reduce emission by more than 10 gigaton CO2 equivalents. Between parentheses, I refer to the ranking of each measure (between 1 – 100) and the estimated reduction of CO2-emission:

  • Wind on land (2; 89,60)
  • Solar parks (8; 36,90)
  • Solar panels on roofs (10; 24,60)
  • Geothermal heat (18; 16,60)
  • Nuclear energy (20; 10,09)
  • Wind on sea (22; 14,09)
  • Concentrated solar energy (25; 10,90).

In the Netherlands, the priorities are different. Firstly, wind at sea; then, solar panels at roofs; thirdly, biomass and lastly, thermal heat. The last source of energy is still largely unexplored.

Many cities want 50% of their use of electricity to be ‘green’ in the next 10 years, but city actions to achieve this goal are limited. Decisions on large-scale power-plants are rarely taken at local level, with the exception of world cities such as London and New York, which have their own plants. On the other hand, many owners (and sometimes tenants) of houses and buildings purchase massive amounts of solar panels, often facilitated by their municipalities. Cities are actively involved with or at least promote third-party campaigns that cover houses and commercial real estate with free solar panels. It is often mandatory that new houses and buildings be energy-neural.

The State of California has taken an important step: from 2020, all new homes will be built with solar panels and their own battery storage.

Nest and Sense: affordable devices to help citizens reduce their energy consumption

The Nest Learning Thermostat can program itself. It first examines the habits of its use and when its user changes the temperature. It then automatically chooses the most likely temperature at any time of the day. It continuously learns from any manual changes. The Nest also keeps track of energy consumption over time so that users can adjust their habits. With other new technologies, such as Sense, consumers can see which electronic devices are being used at any time. As a result, consumers can replace devices or lamps with less expensive versions if desired.

NEST Learning Thermostat – photo NEST

In many places, the possibilities to expand the number of solar panels are limited due to capacity problems on the electricity grid. It was better for communities to encourage energy cooperatives at neighborhood level instead of encouraging individual households to fill their roofs with solar panels. Energy cooperatives do not limit themselves to the production of electricity, but they also regulate storing and trading of energy in the event of surpluses or shortages.

The development of smart grids is an alternative to expensive expansion of the capacity of the existing network, which would be necessary due to the increasing use of electricity and the number of energy suppliers. The production and consumption of energy at neighborhood level can be optimized by solely having devices using, storing or producing energy which can communicate with each other using the Internet of Things.  Ideally, the members of energy co-operatives decide on the rules behind the algorithms in the computer-controlled operating system.

The smart grid in practice

The Amsterdam Citi-zen project has connected 10.000 residences to a smart grid, using over 9.000 smart meters, 13 monitored medium voltage stations (MVSs), and 22 monitored low voltage (LV) mainlines. Fifty battery systems in homes enable their owners to store and trade energy from solar panels on the energy market, making them pay and receive the real energy price. Another project had already shown that price differentiation is an incentive for people to participate in such projects. The third component was the use of electronic vehicles as energy buffers.

The project resulted in valuable insights to better realize the full potential of the smart grid. Accurate knowledge of the lay-out of the low voltage (LV) grid is a condition for determining where the measurement equipment must be placed to register the potential (over)load of the grid. 

The battery systems had various shortcomings. Batteries could not be used effectively because, due to installation standards, they were connected to a different phase of the 3-phase network than to which the solar panels and the electronic equipment were connected. An additional shortcoming was that the batteries sold their energy to the grid while energy was generated. This resulted in an additional peak load on the low-voltage grid, instead of reducing it. However, the number of traders was too small to follow the overall impact of the batteries on the grid. The same applied to the role of electric vehicles.

Battery system installed in Amsterdam – photo City-zen project

Housing, building and construction

Buildings and residential houses are the largest energy consumers in cities (heating, warming, cooling and lightning), not to speak about the production of building materials. They account for 40% of the global energy consumption. Massive realization of energy-neutral buildings (NZEBs) should therefore be top priority for urban developers.

Copenhagen plans to be CO2-neutral in 2025 and is on track, despite significant growth in population and jobs. District heating and cooling of almost the whole city is the most important tool to achieve this, along with the limitation of car use. Copenhagen implements a smart thermal grid, that uses all the residual heat that comes from industrial and commercial activities. Seawater is used for cooling.

Copenhagen is a shining example for the rest of Europe. There is sufficient residual heat to supply 90% of the heat demand of all houses and buildings. The Heat Europe project tries to link areas with a surplus of residual heat to areas with a shortage. The video below shows the ambitions, contours and outcomes of this project.

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The results are presented in the Pan-European Thermal Atlas.

New York is exemplary in another way. The Dirty Buildings Bill requires that 50,000 buildings reduce their emissions by 40% by 2030 and by 80% by 2050. This includes the installation of new windows, insulation, and other retrofit procedures. The law applies to buildings over 25,000 square feet, and together they account for half of all emissions from buildings, although they cover only 2% of total number of buildings in the city.

In a very informative paper, experts summarize dozens of ‘off the shelf’ technologies in the field of artificial intelligence and machine learning to reduce greenhouse gas emissions in the built environment.

Machine learning and warm water supply

Buildings offer numerous options for reducing greenhouse gas emissions. Remarkable results have been reported with fairly simple devices and the use of machine learning. Kazmi and his colleagues have used machine learning in heating and cooling (HVAC) systems, which are notoriously inefficient. With only three sensors (air temperature, water temperature, and energy use) a computer has applied deep learning techniques to gain detailed insight into what temperature of the water in the storage tank is needed to meet user requirements. The result was a scalable energy saving of 20%.

Predicted and observed water temperature in the storage tank – Source: Kazmi et al.

Building permits are useful instruments to influence energy consumption and to promote circularity. In a building permit, requirements can be set for the use of less cement and steel and a limitation of energy consumption. Switching to sustainable timber is an option for 90% of homes and 70% of offices being built. At the other hand, building in an energy neutral, or even positive way offers many advantages. That is why 37% of British developers are convinced that in a few years their portfolio will largely consist of green buildings. By the way, a city like London can save more than $11 billion over the next 5 years by using existing buildings more efficiently and avoiding new construction.

BREEAM: Sustainable buildings

Building Research Establishment Environmental Assessment Method (BREEAM) is a series of indicators for the sustainability of buildings. An example of an almost fully sustainable building is the Bloomberg HQ in London. Among the many (technological) means to achieve this is a green living wall, natural ventilation systems, and 4,000 integrated ceiling panels that combine heating, cooling, and lighting.

Probably the best example in the Netherlands is The Edge, Deloitte’s head office in Amsterdam. The building is energy neutral. To achieve this, the entire southern facade is equipped with solar panels. Rainwater is collected and reused. There is heat-cold storage installation that uses thermal energy.

Both buildings use Philips Ethernet-powered LED connected lighting system, which saves around 40% energy.

Bloomberg London Headquarters – Photo: Bloomberg

Another angle for urban administrators is the insolation of the existing stock of buildings and houses. In the case of new developments, legal regulation is possible. In the case of retrofitting, the municipality can play a supportive role by subsidizing projects by individual owners of houses and buildings, and housing associations. Conveniently, many housing associations and institutional investors have also committed themselves to the Paris agreements.


From an energy perspective, promoting electric cars is useful for emission reduction. From the point of view of livability, however, a reduction in the number of cars is necessary. Cities can keep polluting cars from central parts of the city or opt for a total ban in certain parts of the city. As in many other respects, such decisions have to be supported by the majority of the population, otherwise these decisions will not survive the next elections. As a result of limiting the ownership and use of private cars, 170 million m2 of street parking can be reused in C40-cities, for example for planting 2.5 million trees or creating 25,000 km of cycle paths.

There is a growing awareness that the positive impact of electric cars is overshadowed by the side effects of battery production. Raw materials must be imported from a limited number of countries where production has questionable environmental and social effects.

Anyway, the exchange from gas-fueled cars by (green) electric cars will be gradual, and in order to maintain support of the population, authorities have to offer excellent alternatives, like an efficient, save, affordable and user-friendly public transport. This must be supplemented by save and fast connection for micro-transport such as (shared) bikes or steps and integrated by a software supported Mobility-as-a-Service-system, adding rented cars to the available alternatives.


Municipalities can facilitate the transition to sustainable form of agriculture, as mentioned in the Drawdown report. Moreover, cities can promote the transition to a more plant-based diet, eating healthy quantities and to avoid food waste in the first place. Encouraging joint cultivation of crops by residents can help with this. The Drawdown report recommends reducing meat consumption to a maximum of 16 kg per person per year and dairy products to 90 kg per person per year. In the US that is now 58 kg of meat and 155 kg of dairy.

I have not commented on major changes in industry, aviation, and (international) transport because city authorities have hardly any influence on this.


The definitive termination of greenhouse gas emissions in C40 cities in 2050 requires huge investments, roughly $ 50 to $ 200 per ‘saved’ cubic meter CO2-equivalents. At the same time, these investments provide a global economic stimulus of $ 16,600 billion.

From 2016 to 2050, every C40 city will have to invest $ 10 billion to meet the ambition of the Paris Agreement. This is an investment of more than $ 1000 billion in all C40 cities combined. $ 375 billion is needed in the next four years alone.

Sustainability in the humane city

In summary, municipal authorities worldwide have to work together with all stakeholders, citizens not in the last place, to reduce global warming, and implement a series of activities such as:

  • Covering all suitable roofs with solar panels;
  • Installing wind turbines in seas adjacent to densely populated areas;
  • Creating sufficient storage options for the short and medium term;
  • Creating smart grids to manage the production and consumption of electricity;
  • Heating houses with district heating systems powered by industrial residual heat, hydrogen or heat pumps;
  • Reducing energy use through insulation, efficient use of buildings and smart thermostatic systems;
  • Scrutinizing the necessity of new construction and making sure that it meets breeam requirements;
  • Reducing use of cars (including electric ones) by urban design, enabling walking and cycling opportunities by public transport and by MaaS.
  • Reuse of waste at the highest possible level;
  • Intensification of responsible production of food;
  • Adjustment of consumption patterns by citizens.

All these measures meet only half of the challenge

The other half should be done through prevention of energy poverty, which is increasing in many countries. This term refers to the growing inequality as a result of global warming and some of the relating policies.

The Green New Deal initiative in the US by member of the House of Representatives Alexandria Ocasio-Cortez and Senator Ed Markey from Massachusetts is a good example of the link between the fight against global warming and that against growing social inequality, often along racial divides. The ambition to reduce global warming requires a huge increase in skilled labor and the acquisition of decently paid jobs is a powerful instrument to reduce inequality.

Massive training programs are therefore needed for the renewable energy and insulation sectors. Such programs have already been started. An example is ‘Solar for all’ in Illinois, a program aiming to drastically improve access to solar energy for lower income groups and associated jobs. Such programs are also useful for employees in the fossil fuel industry. Funding for the program comes from a renewable energy fund managed by the state and funded through utilities and energy suppliers.

The short video below, published by the American press agency Vox, summarizes the New Green Deal.

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Despite the magnitude of the challenge that the transition to climate-neutral cities involves, there is reason for optimism. This transition is largely possible with both existing technologies and new technologies that are within reach, such as measurement systems and artificial intelligence. Money is not the big issue. The required investments will pay for themselves in the long term and the transition to clean technology will contribute to responsible economic growth.

The overriding limitation is the lack of skilled labor and this is the connection with the humane city. Humane urban policy is driven by the ambition to involve all citizens in city life. That is why care for jobs, a reasonable income, adequate housing and education go hand in hand with combating global warming. Jobs are the best guarantee for a reasonable income and job opportunities are an incentive to invest in education. The transition to an energy-neutral society will offer ample job opportunities.

Finally, below a summary of the characteristics of a humane approach to sustainability in our cities, considering the relationship between a climate-neutrality, work, income, equality and education.

Actions for a humane approach to climate-neutral cities

1. Reduction of CO2 – emissions and of consumption of products with a high ecological footprint is required for cities that want to be humane, also due to the connection with health and living conditions.

2. Cities are collectively committed to reducing the undesirable environmental and social effects of the production of raw materials for batteries.

3. The international community shall permit countries that are disproportionately affected by the effects of global warming to tax products from countries that contribute disproportionately to greenhouse gas emissions. This money is used to mitigate the effects of global warming at the urban, regional and national levels.

4. Actions within cities to mitigate the effects of global warming are primarily aimed at protecting the densely populated neighborhoods.

5. Cities support the development of energy cooperatives at the local level. These cooperatives are funded to insulate houses and equip them with sustainable heating, cooling and cooking equipment. These investments are – at least partially – paid for by the difference between actual and new monthly energy expenditure.

6. As a fairer alternative to the CO2 emissions tax, companies – including farmers – may temporarily have certain emission levels that will decrease year after year. Interest-free loans are available to invest in this goal. Exceeding the permitted emission is punished.

7. All cities develop transition plans for a carbon-free future. These plans result from cooperation between companies, (knowledge) institutions, groups of citizens and municipal authorities. They are reviewed every two years based on the progress made and new insights.

8. Cities no longer invest in expanding road capacity for passenger cars. Instead, they invest in clearing parts of the city from cars, in public transport in micro transport and in facilities for carbon-free delivery of goods. As a special point of attention, the mobility of disabled people will be improved.

9. To maximize the use and efficiency of district heating, cities work together at regional level to coordinate supply and demand of industrial residual heat or cooling.

10. Cities invest in large-scale educational projects to train thousands of new employees for the sustainability industry (solar panels, district heat grids, insulation). Because many of these employees will not have work experience, their introduction to the labor market is carefully supervised.

11. Owners of houses and buildings are obliged to cover suitable roofs with solar panels for their own use or use by energy cooperatives. Where possible, solar panels are integrated in the roof. Monumental buildings can opt for exemptions for aesthetic reasons.

*) This article was brought to you by Professor Herman van den Bosch, Professor at Open University of The Netherlands.