Ten years ago, London was a world-leading city for action to tackle climate change. We had set ambitious climate change targets and had an ambitious plan to meet them. ??

The action needed to protect our environment helped people too.

Investment in public transport such as the London Overground and affordable travel brought jobs and business to London, helping to keep the cost of living down.

That’s why as mayor I would freeze bus and tube fares and invest in Dutch-style segregated cycling to ensure that cyclists feel safe on our city’s roads. ??

However, today it seems Boris Johnson is doing his best to put our great city on the wrong side of history.

Around the world the movement to divest from fossil fuels is growing. Here in London the School of Oriental and African Studies at the University of London became one of the first to commit to divesting its fossil fuel assets following an inspiring student-led campaign.

It is right to do so. Scientists agree that three-quarters of known fossil fuel reserves — coal, oil and gas deposits that are already owned, bought and sold — must not be burned if we are to avoid tipping the climate into a global catastrophe.

Even Mark Carney, the governor of the Bank of England, has said that the majority of fossil fuels cannot be burned. This has profound implications and must be tackled head on.

The London Assembly has voted to divest the Greater London Authority (GLA) from fossil fuels. But the move is being blocked by Johnson, who is instead calling for London to be fracked, despite the significant health, water contamination, environmental and climate concerns that have led to bans and moratoriums on fracking in Scotland, Wales, Germany, France and states across the US.

??It is reckless to ignore the increasing dangers of runaway climate change, which risks millions of lives worldwide and threatens economic disaster, but Johnson’s support for fracking does just that.

This is the same irresponsibility and disdain for people’s lives that the Tories have shown time and again. Whether it is to the 9,500 Londoners who die needlessly every year because of air pollution, to the 800,000 people freezing in their draughty, poorly insulated homes every winter — while struggling to pay their energy bills — or their cruel welfare caps that are forcing families out of their homes and this city altogether. ??

As mayor I would divest the GLA from all fossil fuels. Even if nations drag their feet, cities can lead way in creating sustainable environments that are pleasant to live and work in.

I would tackle the cost of living and the climate crisis together — by investing in warm homes, cleaning up our air and making public transport affordable. ?But it is not just reckless not to act. It is to miss an opportunity for our city.

Investment in green infrastructure, such as new sustainable, affordable housing, would create thousands of jobs, as would a programme to fully insulate existing heat-leaking homes. Modern homes in modern cities should mean that most of the year the heating does not even need to be switched on.

Making London a city based on renewable energy is now possible and affordable. The price of solar panels has fallen 70 per cent in five years, following the dramatic growth of the industry worldwide.

My Mayoral Green Fund would offer the opportunity for every school to have solar panels with a revolving fund, saving each school an average of £8,000 a year — not just divesting, but investing too. ??

London is a world-leading city — it should lead the way in tackling today’s greatest threat to humanity. Millions of people around the globe are already suffering from more frequent extreme weather, including droughts, floods and hurricanes caused by the climate change that has already happened.

??I believe that protecting people and protecting the planet go hand in hand.

As mayor, I would seek to build a modern, green and affordable city that works for the majority of Londoners and protects our environment for the future. We have the technology — already many other global cities have left us behind. All that is needed is the political will. ?

• Diane Abbott is the Labour MP for Hackney North and Stoke Newington and running to be Labour’s candidate for mayor of London. More information at www.diane4london.co.uk