December 7, 2021

I, Science

The science magazine of Imperial College

Three cities that are doing their best to halt climate change

Climate change is one of our planet’s biggest threats. Occurring at an ever-increasing rate, there is an urgent need to act now, before it’s too late. As French Foreign Minister Laurent Fabius put it ahead of the Paris Climate Negotiations: “we are the first generation to become aware of the problem, and yet the last generation that can deal with it.”

desert city transitioning to green city
Cities are starting to look closer at sustainable infrastructure

Many approaches have been suggested to reduce the global temperature of the Earth. One option is to launch flexible space reflectors into orbit to reduce the amount of sunlight reaching the Earth’s surface. Another involves releasing stratospheric aerosols into the upper atmosphere to scatter incoming sunrays. We could alter the Earth’s albedo, a measure of its surface reflectivity, with earthbound reflectors. Some scientists have even suggested using algae to absorb excess carbon in the ocean.

As the old saying goes, ‘prevention is far better than cure’. All the ‘cures’ mentioned above would cost vast sums of money, and could trigger potential disasters within our delicate ecosystems. The best way to prevent climate change is instead to instate policies and encourage attitudes that reduce the production of greenhouse gases. Policy also needs to target waste, since recycling industrial materials such as copper and steel can reduce net carbon emissions by 400-500%. We should start by looking at urban areas, where 54% of the world’s population live – a figure expected to rise to 66% by 2050. The Intergovernmental Panel on Climate Change (IPCC) reported in 2010 that urban areas account for 71-76% of global CO2 emissions through energy use. This goes to show how much of an impact a more sustainable urban environment could have in fighting climate change. The following three cities have taken the initiative, and are excellent examples of how urban centres can tackle climate change head on.


green plastic bag of trash in front of wall
The plastic bag – hopefully soon to be an image of the past

Last year, the average English person used 140 plastic bags. In a city the size of London, that equates to 1.2 billion bags, or approximately 9,700 tonnes of plastic – the weight of over four London Eyes. England saw the introduction of a 5p levy on plastic bags in October 2015 which will hopefully alleviate much of this waste problem.Londoners are also increasingly subscribing to vegetarian and vegan diets. This may not sound like much, but animal agriculture accounts for 14.5% of greenhouse emissions, which is more than all transport exhaust emissions combined (13%).

Two other examples of carbon reduction in London are upcycling and supermarket food donation. Upcycling is the reuse of discarded objects to make objects with a higher function or value. For instance, some people are now upcycling wood that would otherwise be discarded to make household furniture. Supermarkets produce a lot of waste, but recent initiatives encourage donating this food to charities and the homeless, serving both the environment and people in need.

New York City

Mayor Bill de Blasio recently claimed that New York “is a global leader when it comes to taking on climate change and reducing our environmental footprint. It’s time that our investments catch up – and divestment from coal is where we must start.” Divestment is the opposite of investment – in this case the selling of stocks due to ethical and sustainability concerns. De Blasio recently urged the city’s five pension funds, worth a collective US$160 billion, to sell their US$33 million exposure to coal. New York is taking a huge step in the right direction, and the trendsetting city could encourage other urban centres to follow suit. By 2050, New York aims to reduce its greenhouse gas emissions to 80% of their 1990s levels.


Bogotá is one of the largest cities in South America, with a rapidly growing population of 8 million. The city is already prone to flooding and landslides, generally due to La Niña, climatic events which bring increased regional precipitation. As a result, they face an urgent need to combat any further climate change. Many scientists believe that La Niña events will increase in frequency and intensity with further global warming.

In 2000, Bogotá introduced TransMilenio, a bus rapid transit (BRT) system consisting of 850 buses that provides transport for 1.4 million passengers per day. Since its introduction, TransMilenio has reduced Bogotá’s greenhouse emissions by 40%, as well as cutting travelling time by 32%. BRT systems are a hugely effective way for cities in developing countries to reduce their greenhouse emissions, as it reduces traffic without the need for the large investments in infrastructure that tram and underground systems bring. Nevertheless, one lesson we may learn from Bogotá is that such schemes require hefty government subsidy. The current fare for TransMilenio is 1700 Colombian pesos (US$1), which is steep considering the average low-income worker earns approximately US$3 a day.

By the end of this year, these three cities will no longer be fighting climate change unaided. The 2015 United Nations Climate Change Conference aimed to oversee the first ever legally binding agreement among all countries of the world to fight climate change. The conference hoped to contain global warming to a 2°C increase from pre-industrial temperatures. Above this, serious and irreversible consequences are inevitable. It is hoped that over $100 billion can be raised from both public and private sources in developed countries across the globe. This money will go towards helping the economies of developing countries grow in a sustainable manner, reducing the economic pressures of their new green initiatives and technology.

Children protesters with sign that says "There is no planet B"
Nearly 60,000 people took to London’s streets to protest on November 29th 2015

Climate change is occurring whether we like it or not. It is up to us, particularly those in urban areas, to help combat it. This means doing whatever we can to help reduce our impact on the environment; be it eating less meat, upcycling, recycling or simply cycling more. A change in personal attitudes is essential for combating climate change, but we should also put pressure on governments to recognise that we want to live in a sustainable environment. More of us should seize opportunities like Novembers’s Climate March on London to voice our concerns.

Remember the words of UN Secretary General Ban Ki-Moon: “There is no ‘Plan B’ for action, as there is no ‘Planet B’.”

Shane Morris is a research postgraduate in life sciences 

Images: Urban Landscape, kwest; Plastic Bag, antoniomas; Climate March, Ryan Rodrick Beiler