Kumi Naidoo © Denis Sinyakov / Greenpeace

Dear Friends, 

As I look out my window here in Amsterdam, winter is nearly here, and with it comes the retreat of another year, and the passing of what has been to make way for the spring and the new. As the days get shorter and the weather colder, I'm thinking ahead to days of renewal and new beginnings.

As many of you know, I'm soon moving on from my post as Executive Director of Greenpeace International. I don't think of it as leaving Greenpeace, however. I think of it as exchanging my lofty title for a far more powerful one: that of a Greenpeace Volunteer. It's been an amazing journey with all of you, and I've loved every minute of challenge, every day of struggle, every week of progress, every month of triumph, every year we've been building a better world together.

It's hugely gratifying to be able to depart knowing the Paris climate agreement unanimously signalled the end of the era of fossil fuels by 2050. As imperfect as the agreement may be in how we get there, it marks a stark contrast and a huge advance over my first days with Greenpeace at the Copenhagen climate summit, and it gives me some small notion of closure: the world has taken an important step down a very long and difficult road, but the journey has now unquestionably begun.

Greenpeace had me stepping out of my comfort zone many times. And that, of course, is the place where you learn the most about yourself, when you stand at that line between courage and fear, weighing personal risk against what you believe to be right. I've spoken to so many of you who have had the same experience. People who spoke out, or stood up, who volunteered or took some small step or giant leap for the sake of a better future. So often those steps and leaps take us beyond what we thought we'd ever do – either because we were inspired, or angered, or feeling a bond of unity with others. If anything Greenpeace has ever done has catalysed one of those moments, we're doing our job. We're setting off a chain reaction of contagious courage.

For me, a series of ever escalating life choices eventually led me to a moment I will always cherish from my time at Greenpeace: the boarding of an oil rig in the Arctic, having an icy water cannon trained on me as I struggled to climb a ladder to oppose the absurdity of Arctic oil drilling. Experiences like that change you. And by “like that” I don't necessarily mean that extreme form of activism: I mean any action that disrupts your sense of self or your idea of who you are and puts it in a larger context of the human journey and the future of our world. It resets your notion of what you're capable of. And in so doing resets your notion of what humanity is capable of. And in so doing redefines your sense of what's possible.

I came to Greenpeace wanting to break the dichotomy between the environment and development. I knew, rationally, that there is a link between addressing poverty and human rights and addressing environmental injustice and climate injustice. But my time with Greenpeace drove this awareness deeper into my heart. Once you see it, you can't stop seeing it. From the woman who can no longer fish the African coasts for her family because European factory trawlers have emptied her seas, to the child in India choking on ash and coal dust in a village pillaged by the coal industry, to the infant breathing in toxic fumes in an electronic waste dump in China while his mother sets fire to a circuit board to scavenge components, to the devastated family living in a cardboard box after their home was destroyed by typhoon Hagupit in the Philippines: the people who pay the highest price for overconsumption and pollution are those who see the least benefit.

Greenpeace strengthened my belief in the power of nonviolent direct action and my conviction that civil disobedience is essential to addressing this core injustice, to bringing about a truly transformational change not only in the way we feed and fuel our world, but in how we think about wealth, growth, and value – how we reinvent the future in the face of what Naomi Klein has described as an incredible opportunity disguised as a crisis.

In the six years I've been with Greenpeace, we've secured so many victories – from Shell's decision to abandon Arctic Drilling to Italian energy giant ENEL's turning its back on fossil fuels. From dozens of major retailers agreeing to Detox their clothing lines to agreements with major deforesters to end peatland destruction in Indonesia. From Facebook's agreement to friend renewable energy to new Marine Reserves that have increased the size of our protected waters. But these are but small contributions to the vast changes that a far wider movement is driving – from the unprecedented court decision in the Netherlands that the government is negligent of its duty to protect its people if it doesn't cut CO2 by 25% by 2020 – driven by tiny NGO Urgenda – to Elon Musk's decision to open source the design of the Tesla electric car and the PowerWall smart battery, to crowdfunding campaigns for oceans plastic cleanup and prototype solar roadways to new models in the sharing economy to The Guardian's coal divestment campaign. I have found myself on podium after podium speaking from the same agenda of climate urgency as Sharan Burrow, the head of the global trade union movement. I leapt from my chair in celebration after reading the Pope's recent encyclical on stewardship over the Earth. From every category of human endeavour, from every continent, we're witnessing an awakening – an unprecedented conspiracy of courage and commitment to change.

To my successor I leave unfinished business and great challenges. The organisation is still licking its wounds from setbacks that have occurred on my watch – times when we have failed to live up to the values we champion. And while we can never promise to stop falling short of our own standards and expectations, we can commit to learning from those failures. They make us stronger.

My greatest hope is that my successor will continue the unfinished journey of ensuring that Greenpeace becomes more truly global and diverse, more open, better able to unleash the energy and creativity of our supporters and volunteers, more articulate about what we stand for and the solutions we champion, more cooperative in working with movement partners and using our reach to lift up the work of others, more willing to dare to risk – and achieve – the impossible.

As for me, I'm returning to one of the most beautiful places I know in Africa, Rustlers Valley in the Free State, South Africa near the border with Lesotho. There I will continue to work with the EarthRise Trust that is developing an activist school, ecological farming projects, educational development, and economic empowerment programmes. I'll be working alongside Greenpeace in the struggle against nuclear power and to reform the rules of the financial world to stop the flow of money toward projects which are holding back a more beautiful, sustainable, and equitable future for all humanity.

My friends, I leave you with a final thought. As you look around you, remember what the history of the human journey teaches us. The greatest struggle we face is not inventing clean technologies or fundamentally changing the way we produce value or measure growth: these are small challenges compared with how we have changed the world and our own civilization over the course of the few centuries that we've risen up. I refuse to believe that the pace of change for survival will be slower than the pace of change for profit. In times of war, in times of threat to our families or nations we've found unforeseen strength, and we've done impossible things.

But there's an essential ingredient. Without it, the burst of efforts and evidence of change that we see today will remain too little, too late.

That ingredient is hope. It's the belief that change is possible. I saw with my own eyes what happened to the struggle against Apartheid in South Africa once people in large numbers came to believe change was possible. I look around today, and I see more and more evidence that we can beat the worst ravages of climate change. It will take fast action. It will take courage like we have never witnessed on a global scale before – from banks, from corporations, from artists, governments, religious and labour leaders, the charity sector, the billionaires, and from every one of us. Every time the world takes a step forward, be it Apple powering all of its data centres on renewable energy, be it Obama saying no to Arctic oil, be it your university's decision to divest from coal, your neighbor's decision to grow their own vegetables, your parent's decision to volunteer for a cause, or your colleague's decision to eat less meat – whenever anyone makes a contribution to building that better world we know in our hearts it is possible, we have a duty. A duty to share. To tell the world. To make that courage contagious. Make it a norm. Make it an expectation that this is how the world works. Belief requires evidence, and the stories we tell one another evidence our beliefs: some stories propel us forward. Others hold us back. We can believe that change is impossible, or too expensive, or naive, and consign the fate of this earth to death by business as usual. Or we can fight back. We can stand up and say that a better world is not only possible, it's being built right now, by the individual and collective acts of courage of every one of us.

To all of you reading this, to all my colleagues at Greenpeace, to all of us working for a better world, thank you for letting me be a part of your journey. I wish you strength. I wish you happiness. I wish you courage.