Imagine water crashing into your bedroom in the dead of night, dragging you from your bed and into its cold, murky depths. Imagine watching the roof above you being ripped away by a howling, raging wind. Imagine dodging flying debris and hearing your children’s screams mingled with yours above the roar of the storm. Imagine watching helplessly as your family is hauled away by a swirling, rushing deluge.

Imagine the aftermath, knowing that your house and everything that you own is gone. Imagine staggering through rows of bodies, with the gut-wrenching fear that one of the white sheets will unveil your loved one’s face. For many of us, these are fleeting scenes that we encounter in the media every now and then. But for those living with the worst effects of climate change this is their stark reality.

As leaders, the big question is: how do we impress upon the planet’s seven billion people that climate change is everybody’s problem? Its effects are becoming more dramatic every day with increasing droughts, floods and storms, and countries disappearing into the ocean as sea levels continue to rise. The headline is that no one is safe, that the experience of the unlucky millions who are bearing the brunt of it will soon be the reality of billions if we do not change our course. It is no exaggeration to say that this is about the survival of the human race.

As I came into office, this terrifying threat was one of the issues that weighed heaviest on my mind. It was not too long ago that Hurricane Erica unleashed its rage on Dominica, the beautiful island of my birth. It is painful to watch the place where my parents lived for most of the 70 years of their happy marriage lose 90 per cent of its GDP and decades of development progress in hours.

In the Pacific, Vanuatu and Fiji are struggling to recover from hundreds of millions of dollars worth of damage. But the worst aspect of these tragedies is the loss of life and the inconsolable grief that climate change is causing. From Pakistan to Australia to the UK, no region has been left untouched.

This is why within days of taking office at the Commonwealth Secretariat, I hosted a high-level dialogue on climate change to capture the views of experts and thought leaders on the topic, so that we could better shape our response. Now, today, I am here in New York to witness the signing of what has been described again and again as a landmark global agreement to tackle climate change. Most of the world will be represented, and despite what the critics say, I believe that each signature represents a recognition of the scale of the problem and a national commitment to take action.

I am particularly proud of the role the Commonwealth played in the success of this deal, which was made at the COP21 climate change summit in Paris last December. Just days before this historic agreement, Commonwealth leaders issued a statement on climate action, with a commitment to a climate change ‘speed limit’ of two degrees and aspirations for 1.5 degrees. We went to Paris, big and small, rich and poor, united in our aims and were able to truly amplify the voices of the small states who are worst affected by climate change.

Now we celebrate what is officially day one of the journey to the implementation of the Paris agreement. But the Commonwealth has already had a head start. We have been in conversations with multilateral institutions and our members about an initiative to swap national debt for climate change action. This Multilateral Debt Swap for Climate Action proposal, endorsed by the United Nations Secretary General, will help small states reduce their public debt in exchange for their commitment to use the repayments to finance local climate change projects.

Our pioneering Commonwealth Climate Finance Access Hub, agreed at the 2015 Commonwealth Heads of Government meeting, will ensure small and vulnerable states with acute capacity needs can successfully bid for climate action funding.

Working in collaboration with regional organisations such as the Caribbean Community Climate Change Centre in Belize, the Pacific Regional Environment Programme in Samoa and the Indian Ocean Commission in Mauritius, the Hub will offer tailored support to the countries that need it the most. Hosted by the Government of Mauritius and funded by The Government of Australia, the initiative is already in demand.

Ultimately, we are saying to our member countries, you are not alone in the climate change challenge. The Commonwealth will be with you every step of the way. So I am calling on governments to prove the critics wrong, to work tirelessly together to achieve our national commitments. To recognise the importance of having our populations behind us. We need an education drive like no other. We need allies in the technology and science fields to create a more eco-friendly world. We need to get into households to tell each individual what they can do in their daily lives to save our planet. We need to engage with schools, right down to the tiny tots.

This is a mission that must succeed, because to fail is to rob our children and grandchildren of their future.

Patricia Janet Scotland, Baroness Scotland of Asthal, is the sixth secretary general of the Commonwealth of Nations. She is the first woman to hold the post.