Over the past year, cities across the world have been buffeted by natural events. Floods ravaged the residents of Mumbai; and tropical storm Harvey left Houston underwater. Cape Town had its worst drought in over a century; and Shanghai, the world's most populous city, experienced its hottest day in recorded history.
While we can't say that these individual events were caused by climate change, they are likely to have been exacerbated by it. And scientific models predict that these kind of extreme weather events will become more common, and more intense, in the future.
Cities and their inhabitants will be increasingly vulnerable. Throughout human history, we have built our major settlements on low-lying land near rivers and seas. As these cities have grown, more people have packed into areas at risk of inundation. We've constructed our cities with tarmac, concrete and glass that reflect heat when it's sunny and collect, channel and speed up the water when it rains. And many cities find themselves at the end of long supply chains bringing them water, energy, and food. For these cities, climate change will pose severe and increasing risks.
City administrations are, of course, beginning to respond to these challenges. The C40 network of mega-cities is collaborating to cut carbon emissions. The Rockefeller 100 Resilient Cities initiative is helping administrations prepare for the impacts of a changing climate. Cities are using their power to advocate for action, and - as we have seen in Trump's America -- stepping-up when their national governments waver.
However, the stark reality is that, despite all the excellent initiatives that cities are taking to cut emissions, the CO2 humankind has already pumped into the atmosphere means the world is destined to suffer severe climate impacts. Cities will have to adapt.
Green infrastructure is an area where I think city governments should show more leadership and put more investment. This could be at the macro level across the whole city, or on the micro-level in individual dwellings. Done well, green infrastructure can provide multiple environmental and social benefits.
As we have seen in 2017, flooding is already a major global challenge. And here in the UK, according to the Environment Agency, floods are now the number one natural hazard facing the country. With climate change leading to rising sea levels, changing rainfall patterns, and severe storms, the threat is only going to get worse.
The rising tides cannot simply be held back with concrete and barriers; water needs to flow somewhere. The aim should be to slow it down, allow it to soak away, and give it somewhere to go. Cities should be designed to be more like a sponge than a table-top.
Green infrastructure can help. Green roofs slow water down. Front gardens allow it to soak away. New parks and playing fields can provide civic amenity for most of the year - and a harmless place for water during floods.
Green infrastructure can also help with overheating cities. Due to the 'urban heat island' effect, big cities are often more than 5 degrees warmer than the surrounding areas. Given that the world is only going to get warmer, residents in big metropolises will feel the heat. Trees provide shade and help cool the environment, as well as improving amenity and liveability. Having been hit by savage heat-waves over recent years Melbourne is working to double its tree canopy cover.
Green infrastructure also supports biodiversity, which will come under strain from a changing climate. A good example is the 'Wild West End' scheme in London, which, by providing new small habitats on roofs and parklets, and creating corridors between existing big habitats like the parks, is encouraging birds, bees and bats back into the centre of the capital.
Some of these green spaces might even support urban agriculture. Climate change is bound to affect farming and food security across the world. And city dwellers rely on imported food. I'm always struck by the fact that 90% of the Russian potato crop is grown in dacha gardens or small farms, because people think it is too important to rely on someone else for this staple.
Here in the UK, one of my favourite pieces of urban green infrastructure is the front garden. This small patch of green can do lots of good things: slow down rainwater and allow it to soak away; help cool the city; provide a habitat for biodiversity; reduce pollution and even be a place to grow some veg. Oh, and front gardens makes neighbourhoods more attractive places to live.
Yet across the UK, in an act of civic vandalism, these gardens are being dug up and concreted over to provide parking spaces. This is the opposite of what our cities need to be sustainable.
Despite the important role green infrastructure can play in making cities more resilient and more verdant and attractive, it too often gets ignored. Politicians don't give it the same political attention as roads and buildings. City administrators don't give it a senior boss or a budget. Engineers prefer to construct hard surfaces and to pour concrete. And citizens don't believe that their millions of small steps will add up to anything big enough. This has to change. And that requires civic leadership.
Peter Madden, OBE