The problem is global; the solution, local.

World governments are squabbling over what - sometimes, if anything - they need to do to tackle the climate emergency.

Donald Trump’s America a year ago gave 12-month’s notice that it would pull out of the last big international environmental deal, the 2015 Paris Agreement.

That decision is due to come in to effect just after Tuesday’s presidential election - whoever wins. But it has already had an impact: a growing realisation that the battle for the planet is too important to leave to presidents and princes, premiers and politburos.

So, gradually, it is not just nation-states which are leading on global heating. Substates, regions, counties and, especially, cities are doing so too.

Take Glasgow. This autumn Scotland’s biggest city - one of the pioneers of the industrial age responsible for global heating gases - was supposed to be hosting COP26, the United Nations summit to agree the treaty to replace Paris.

That conference has been shelved for a year because of the Coronavirus pandemic.

But that does not mean city authorities - who are in a race of their own to be net carbon neutral by 2030 - have stepped away from their own international efforts.

Glasgow council leader, Susan Aitken of the SNP, will next week tell a Herald event on the countdown to COP26 that her administration has teamed up with two major New World cities, Pittsburgh in the United States and Santiago in Chile, to share expertise on how to wean themselves off carbon.

This is not an old-school twinning arrangement for civic dignitaries in chains of office to visit each other. These are practical arrangements for world cities to exchange ideas.

Speaking ahead of The Herald event, Aitken said: “Addressing the climate emergency requires leadership and, increasingly, it is cities that are stepping up to take on that role – pushing beyond national targets and, in some cases, against inaction and outright hostility.

“Cities are where the race to zero is won. Nation states pledge – but cities deliver.

“More than half of the global population lives in cities – and the United Nations expects that to grow to 68% in just the next 30 years. Cities are also, overwhelming, where much of our knowledge and skills can be found – they drive our national and international economies and they are also where you turn for ideas and innovation.

“All of this not only means our cities are responsible for the majority of global emissions, but also makes us particularly vulnerable to the impact of climate change.

“The truth is that cities – like Glasgow, like Pittsburgh and like Santiago – can’t afford to wait.”

Aitken added: "We are making common cause with cities across the globe with similar pasts and facing the same challenges as us - to have our voices heard, but also to learn from each other. There is a wealth of real practical knowledge, experience and expertise that we need to share if we are going to make a just transition to greener, more sustainable cities.

"For instance, Pittsburgh is closer in some regards to Glasgow than Edinburgh is, in terms of our post-industrial trajectories - and there is much we can learn from their polices and interventions that might work well in Glasgow.

“We need to be using these connections now and mobilise our involvement in city alliances towards taking action and influencing the climate change agenda.

"For us as a city, it should not be a choice between service provision or working with international counterparts on tackling the climate emergency. It is doing both of the things with the desire to be a greener, more sustainable and equitable city at the heart of all we do.”

Santiago formally hosted the last COP summit in 2019 (even though the event was staged in Madrid because of mass protests in Chile). So it is handing over the baton to Glasgow.

However, there is more to the relationship that just this. The two cities were put together by matchmakers in the European Commission International Urban Co-operation programme because of common interests.

Santiago, like Glasgow, feels hosting a COP event adds a burden of exception that it will be in the winning pack of cities in what is being called the “Race to Zero”

Felipe Alessandri, mayor of Santiago, said: "We have a huge responsibility to lead the Santiago-Glasgow route between the two cities and from two hemispheres, being a beacon for the rest of the local governments of the planet towards COP26 but understanding that the climate emergency we are facing is the biggest challenge that humanity has.

“Cities must raise their ambition towards carbon neutrality by 2050 or before and send a message of hope to millions of people who expect from us a higher consciousness to live in a world; with less artificial intelligence and more human sensitivity.”

With the United States federal government seen as weak on the climate emergency, at least under Trump, cities, states and counties have gone a long way to push for carbon reduction.

This is particularly true for Pittsburgh. The Pennsylvanian steel city, like Glasgow, was a pioneer of industrialisation. Now it has a leadership role among American cities moving away from carbon.

Its mayor, William Peduto, said: "While the Scottish connection to Pittsburgh has long been established, from its naming by a Scot, General John Forbes to industrialist and shared native son Andrew Carnegie, through our shared rise as industrial powerhouses the two cities have a deep connection.

“The connection has been strengthened in recent years as we've shared the challenges of industrial heritage, built a renewed strength through a shared resilience journey and now seek to collaborate through a sister cities arrangement as we work together, to address issues of climate change, health inequality and building more equitable prosperity.”

The UN Environment Programme believes that cities account for three-quarters of climate-heating gases, mostly from transport and buildings.

In contrast rural areas are already at or close to net zero. In Scotland this includes the Highlands.

So governments wanting to stop heating the planet need to focus on major urban centres. The UNEP said: "It is essential to make cities an integral part of the solution in fighting climate change.

“Many cities are already doing a lot by using renewable energy sources, cleaner production techniques and regulations or incentives to limit industrial emissions. Cutting emissions will also reduce local pollution from industries and transport, thus improving urban air quality and the health of city dwellers.”

Glasgow has set a target of 2030 to be net zero carbon.

Sharing expertise is a key to getting to these targets. Back in 2018 Chatham House produced a report on the role of substate and non-state actors - local authorities, charities and businesses - in tackling climate change.

It said: “Global networks of cities, businesses and other actors offer a critical way to transmit information, expertise and resources to their constituents around the world. By linking domestic stakeholders to these networks, governments build domestic capacity to reach national goals.”