Dear Greta,

Thank you for travelling across the Atlantic to north America to help us do the most important work in the world. There are those of us who welcome you and those who do not because you have landed in two places, a place being born and a place dying, noisily, violently, with as much damage as possible.

It has always been two places, since the earliest Europeans arrived in places where Native people already lived, and pretended they were new and gave them the wrong names. You can tell the history of the United States – which are not very united now – as the history of Sojourner Truth, the heroine who helped liberate the enslaved, as that of the slaveowners and defenders of slavery, as a place of visionary environmental voices such as Rachel Carson and the corporate powers and profiteers she fought and exposed.

Right now the US is the country of Donald Trump and of Alexandria Ocasio-Cortez, of climate destroyers and climate protectors. Sometimes the Truths and the Carsons have won. I believe it is more than possible for Ocasio-Cortez and the Green New Deal to win, for the spirit of generosity and inclusion and the protection of nature to win – but that depends on what we do now. Which is why I’m so grateful that you have arrived to galvanize us with your clarity of vision and passionate commitment.

To be a climate activist anywhere on Earth now is to stand at a crossroads: heaven on one side and hell on the other

Not long ago I talked to a powerful climate organizer who began her work when she was only a little older than you, and she told me that her hope right now is that people recognize that this is a moment of great possibility, of openings and momentum, and a growing alarm and commitment to what the changing climate requires of us. Something has changed, thanks to you and to the young people who have brought new urgency and vision to the climate movement. Many people have become concerned and awake for the first time, and the conversation we need to have is opening up. People are ready for change, or some of us are. This is what’s being born in the US and around the world: not only new energy systems, but new social systems with more room for the voices of those who are not white or male or straight or neurotypical.

The old energy system was about centralized control and the malevolent power of Gazprom and BP, Shell and Chevron, and the governments warped into serving them rather than humanity. The new system must not only be about localized energy, but democratized decision-making, about the rights of nature and the rights of the vulnerable and the future, over profit.

Some of this is already here: not only the larger groups you’re surely heard of – the Sunrise Movement, 350.org, the Sierra Club, Rainforest Action Network – but countless local and tribal groups that have arisen to stop this pipeline or that coal port or these fracking projects, to protect this forest or this mountain or these waters. They are not visible the way the United Nations or the US Congress or European Union is, but their work matters, and perhaps we will build a lot of this transition out from below – but we need the big policy agendas set from above as well.

US generates more electricity from renewables than coal for first time ever Read more

Everywhere I see remarkable things happening. No matter how much you see of this big country, this huge continent, there is more than you can see. I hope you have a chance to see some of the beauty of the American landscapes, from rainforests to deserts; there is also beauty in the passionate commitment around the country. Coalminers in Kentucky have been blocking a coal train track for a month, because their bankrupt company stiffed them on wages, and coalminers elsewhere recently spoke to this newspaper about their clarity that coal is over and that the Green New Deal and its jobs are welcome. The gigantic coal-burning, sky-polluting Navajo Generating Station in Arizona will shut down later this year, and, Scientific American reported, “Its average annual emissions over that period are roughly equivalent to what 3.3 million passenger cars would pump into the atmosphere in a single year. The Navajo Generating Station isn’t alone. It’s among a new wave of super-polluters headed for the scrap heap,” including giant plants in Kentucky and Pennsylvania.” Last year, US coal plants with annual emissions of 83 million tonnes of carbon were shut down.

Play Video 0:54 'A massive wall of fire': wildfires rage in California – video

Several states – California, New York, Hawaii, New Mexico – have made commitments to 100% renewable electricity in the near future, and while the federal government tries to push us backward, many states lean forward. This summer Texas began to get more energy from wind than from coal. Iowa in the midwest now gets 37% of its electricity from wind, not because of idealism alone, but pragmatism: wind is cheaper. Science magazine reported last month, “Solar plus batteries is now cheaper than fossil power,” and a Connecticut newspaper recently announced that Chubb, the largest commercial insurer in the USA, will stop insuring coal plants and coal mining.

Worldwide, we are in the midst of an energy revolution that dwarfs the industrial revolution: human beings will for the first time not use fire, will not release carbon into the sky, to get most of our energy. We will inevitably transition away from fossil fuels as a primary energy source, and the question is only when. If we do it swiftly, we minimize damage to the climate; if we wait, we maximize it. The damage is here, and it’s not only destroying nature, it’s killing us. When the California town of Paradise burned down last November, at least 86 people burned to death or choked on smoke; millions suffered from the smoke that spread across the region. Heat deaths are up in the south-west, where 235 people died in Arizona alone from this cause during 2017.

But we also know that there are so many uncounted deaths from poisonous fossil fuels. We know that many of the refugees on the USA’s southern border are climate refugees, driven out of their homes in Central America by the failure of agriculture from unpredictable and violent weather, heat, and drought. We know that Alaska was this month for the first time ice-free all along its coast, and the hot dry weather inland led to horrific wildfires. “Starting on the fourth of July and lasting multiple days, temperatures across Alaska were 20 to 30 degrees above average in some locations,” reported National Oceanic and Atmospheric Administration.

'Let's do it now': Greta Thunberg crosses Atlantic and calls for urgent climate action Read more

To be a climate activist anywhere on Earth now is to stand at a crossroads: heaven on one side and hell on the other. Heaven because the transition we need to make and are making – just not big enough or fast enough – is not only an power-generation revolution, but a decentralization of political power, a shift away from the big energy companies who used governments to make wars and make profits for them, a shift away from the poisonousness of fossil fuel. Hell because the destruction of what it took nature millions of years to create – the exquisite balance of ecosystems, of bird migration in harmony with seasons, of symbioses between species, of the great Himalayan and Andean glaciers whose waters feed so many people, of rainforests and temperate forests – is hideous as well as terrifying. The Amazon is burning because of one rightwing leader and a system that rewards agricultural products but not forest protection, even though we need rainforests more than we need the soybeans and beef raised on the land stolen from the rainforest and its indigenous inhabitants.

I’ve mentioned a bit of what is going on in my troubled, complicated country, the US, but of course these are global conflicts and global situations, and the solutions are advancing almost everywhere, because they are good solutions to terrible problems.

You have come to help us choose the former over the latter, and more of us thank you than you will ever be able to see or hear. More than that, we’re with you, trying to realize the goals that the climate demands of us, to make a sustainable world for those who are young now, those yet to come, and for the beauty of the world that is still with us.

• Rebecca Solnit is a journalist and author.