Climate change is the defining issue of our time – and we are at a defining moment, says Antonio Guterres, the secretary general of the United Nations.

CLIMATE CHANGE is the defining issue of our time - and we are at a defining moment. We face a direct existential threat. Climate change is moving faster than we are. If we do not change course by 2020, we risk missing the point where we can avoid runaway climate change, with disastrous consequences for people and all the natural systems that sustain us.

We must break the paralysis. We have the moral and financial reasons to act. We have the tools to make our actions effective. What we still lack – even after the Paris Agreement – is leadership and the ambition to do what is needed.

My friends, let there be no doubt about the urgency of the crisis.

We are experiencing record-breaking temperatures around the world.

According to the World Meteorological Organization, the past two decades included 18 of the warmest years since 1850, when records began. This year is shaping up to be the fourth hottest.

We now know that Hurricane Maria killed almost 3,000 people in Puerto Rico last year, making it one of the deadliest extreme weather disasters in US history.

Many of these people died in the months after the storm because they lacked access to electricity, clean water and proper healthcare because of the hurricane.

What makes all of this even more disturbing is that we were warned.

Scientists have been telling us for decades. Over and over again. Far too many leaders have refused to listen. Far too few have acted with the vision science demands.

We see the results. In some cases, they are approaching scientists’ worst-case scenarios. Arctic sea ice is disappearing faster than we imagined possible.

Oceans are becoming more acidic, threatening the foundation of the food chains that sustain life.

Corals are dying in vast amounts, further depleting vital fisheries.

As climate change intensifies, water will become more scarce. We will find it harder to feed ourselves. Extinction rates will spike as vital habitats decline. More and more people will be forced to migrate from their homes as the land they depend on becomes less able to support them.

Put simply, we need to put the brake on deadly greenhouse gas emissions and drive climate action. We need to rapidly shift away from our dependence on fossil fuels. We need to replace them with clean energy from water, wind and sun. We must halt deforestation, restore degraded forests and change the way we farm.We need to embrace the circular economy and resource efficiency. Our cities and transport sectors will need to be overhauled. How we heat, cool and light our buildings will need to be rethought so we waste less energy.

Enormous benefits await humankind if we can rise to the climate challenge. A great many of these benefits are economic.

Humankind has confronted and overcome immense challenges before; challenges that have required us to work together and to put aside division and difference to fight a common threat.

That was how the United Nations came into being.It is how we have helped end wars, stop diseases, reduce global poverty and heal the ozone hole.

Now we stand at an existential crossroad. If we are to take the right path - the only sensible path - we will have to muster the full force of human ingenuity.

Technology is on our side in the battle to address climate change.

The rise of renewable energy has been tremendous. Climate change affects every aspect of the work of the United Nations. Keeping our planet’s warming to well below two degrees is essential for global prosperity, people’s well-being and the security of nations.

I am calling on all world leaders to come to next year’s Climate Summit prepared to report not only on what they are doing, but what more they intend to do when they convene in 2020 for the UN climate conference. And I am calling on civil society, and young people in particular, to campaign for climate action.

Let us use the next year for transformational decisions in board rooms, executive suites and parliaments across the world. Let us raise our sights, build coalitions and make our leaders listen.

I commit myself, and the entire United Nations, to this effort. We will support all leaders who rise to the challenge I have outlined today.

We are careering towards the edge of the abyss. It is not too late to shift course, but every day that passes means the world heats up a little more and the cost of our inaction mounts.

Every day we fail to act is a day that we step a little closer towards a fate that none of us wants - a fate that will resonate through generations in the damage done to humankind and life on earth.Our fate is in our own hands. The world is counting on all of us to rise to the challenge before it’s too late.

Antonio Guterres is the secretary general of the United Nations. Email feedback to columns@gleanerjm.com.