Never before in history have human beings been called on to act collectively in defence of the Earth. As a species, we have endured world wars, epidemics, famine, slavery, apartheid and many other hideous consequences of religious, class, race, gender and ideological intolerance. People are extraordinarily resilient. The Earth has proven pretty resilient, too. It's managed to absorb most of what's been thrown at it since the industrial revolution and the invention of the internal combustion engine.

Until now, that is. Because the science is clear: the sponge that cushions and sustains us, our environment, is already saturated with carbon. If we don't limit global warming to two degrees or less we are doomed to a period of unprecedented instability, insecurity and loss of species. Fossil fuels have powered human endeavour since our ancestors developed the skills to make and manage fire. Coal, gas and oil warm our homes, fuel our industries and enable our movements. We have allowed ourselves to become totally dependent, and are guilty of ignoring the warning signs of pending disaster. It is time to act.

As responsible citizens of the world – sisters and brothers of one family, the human family, God's family – we have a duty to persuade our leaders to lead us in a new direction: to help us abandon our collective addiction to fossil fuels, starting this week in New York at the United Nations Climate Summit. Reducing our carbon footprint is not just a technical scientific necessity; it has also emerged as the human rights challenge of our time. While global emissions have risen unchecked, real-world impacts have taken hold in earnest. The most devastating effects of climate change – deadly storms, heat waves, droughts, rising food prices and the advent of climate refugees – are being visited on the world's poor. Those who have no involvement in creating the problem are the most affected, while those with the capacity to arrest the slide dither. Africans, who emit far less carbon than the people of any other continent, will pay the steepest price. It is a deep injustice.

The United Nations deserves kudos for its leadership on human rights issues. But on climate change, it has run up against governments and leaders of industry who have until now put short-term economic and political goals ahead of our collective long-term survival. We can no longer tinker about the edges. We can no longer continue feeding our addiction to fossil fuels as if there were no tomorrow. For there will be no tomorrow. As a matter of urgency we must begin a global transition to a new safe energy economy. This requires fundamentally rethinking our economic systems, to put them on a sustainable and more equitable footing.

I am not without hope. When we, humans, walk together in pursuit of a righteous cause, we become an irresistible force. There are many ways that all of us can fight climate change: by not wasting energy, for instance. But these individual measures will not, the scientists assure us, make a big enough difference. And they may not be appropriate for the world's poor.

We can boycott events, sports teams and media programming sponsored by fossil fuel companies; demand that their advertisements carry health warnings; organise car-free days and other platforms to build broader societal awareness; and ask our religious communities to speak out on the issue from their various pulpits. We can encourage energy companies to spend more of their resources on the development of sustainable energy products, and we can reward those companies that demonstrably do so by using their products to the exclusion of others.

Just as we argued in the 1980s that those who conducted business with apartheid South Africa were aiding and abetting an immoral system, we can say that nobody should profit from the rising temperatures, seas and human suffering caused by the burning of fossil fuels.

We can encourage more of our universities and municipalities, foundations, corporations, individuals and cultural institutions to cut their ties to the fossil fuel industry. To divest, and invest, instead, in renewable energy. To move their money out of the problem and into the solutions. We can urge our governments to invest in sustainable practices and stop subsidising fossil fuels; and to freeze further exploration for new fossil energy sources. The fossil reserves that have already been discovered exceed what can ever be safely used. Yet companies spend half a trillion dollars each year searching for more fuel. They should redirect this money toward developing clean energy solutions. We can support our leaders to make the correct moral choices and to avoid undue industry influence that blocks the political will to act on climate change. Through the power of our collective action we can hold those who rake in the profits accountable for cleaning up their mess. The good news is that we don't have to start from scratch. Young people across the world have identified climate change as the biggest challenge of our time, and already begun to do something about it.

Over the last three or four years, we have seen the rise of a new civil society divestment movement to stand alongside the scientists, environmentalists and social activists who have been challenging the moral standing of the fossil fuel industry.

Once again, it is a global movement led by students and faith groups, along with hospitals, cities, foundations, corporations and individuals. It is a moral movement to persuade fossil fuel companies away from a business model that threatens our very survival. My prayer is that humankind takes its first tangible steps in New York this week – as a collective – to move beyond the fossil fuel era.

There is a word we use in South Africa that describes human relationships: Ubuntu. It says: I am because you are. My successes and my failures are bound up in yours. We are made for each other, for interdependence. Together, we can change the world for the better.

Who can stop climate change? We can. You and you and you, and me. And it is not just that we can stop it, we have a responsibility to do so that began in the genesis of humanity, when God commanded the earliest human inhabitants of the Garden of Eden, "to till it and keep it". To "keep" it; not to abuse it, not to make as much money as possible from it, not to destroy it.