Our planet is facing a crisis. But even when we know that a war for our survival is raging, we don’t feel that it is our war. Although many of climate change’s accompanying calamities – extreme weather events, floods and wildfires, displacement and resource scarcity chief among them – are vivid, personal and suggestive of a worsening situation, they don’t feel that way in aggregate. The distance between awareness and feeling can make it very difficult for even thoughtful and politically engaged people – people who want to act – to act.

So-called climate change deniers reject the conclusion that 97% of climate scientists have reached: the planet is warming because of human activities. But what about those of us who say we accept the reality of human-caused climate change? We may not think the scientists are lying, but are we able truly to believe what they tell us? Such a belief would surely awaken us to the urgent ethical imperative attached to it, shake our collective conscience and render us willing to make small sacrifices in the present to avoid cataclysmic ones in the future.

In 2018, despite knowing more than we have ever known about human-caused climate change, humans produced more greenhouse gases than we’ve ever produced, at a rate three times that of population growth. There are tidy explanations – the growing use of coal in China and India, a strong global economy, unusually severe seasons that required spikes in energy for heating and cooling. But the truth is as crude as it is obvious: we don’t care. So now what?

Of course there are some moments when the planetary crisis is acutely felt. Watching Al Gore’s An Inconvenient Truth was an intellectual and emotional revelation for me. When the screen went dark after the final image, our situation seemed perfectly clear, as did my responsibility to participate in the struggle. And when that film’s credits rolled, at the moment of greatest enthusiasm to do whatever was asked to work against the imminent apocalypse that Gore had just delineated for us, suggested actions appeared on the screen. “Are you ready to change the way you live? The climate crisis can be solved. Here’s how to start.”

Among the suggestions were: tell your parents not to ruin the world that you will live in; if you are a parent, join with your children to save the world they will live in; switch to renewable sources of energy; plant trees, lots of trees; raise fuel economy standards; require lower emissions from automobiles.

Facebook Twitter Pinterest Al Gore in An Inconvenient Sequel: Truth to Power. Photograph: Participant Media/Paramount Pictures

There is a glaring absence in Gore’s list, and its invisibility recurs in 2017’s An Inconvenient Sequel: Truth to Power, with one minuscule exception. It is impossible to explain this omission as accidental without also accusing Gore of a kind of radical ignorance. In terms of the scale of the error, it would be equivalent to a doctor prescribing physical exercise to a patient recovering from a heart attack without also telling him he needs to quit smoking, reduce his stress and stop eating burgers and fries twice a day.

So why would Gore deliberately choose to leave this particular issue out? Almost certainly for fear that it would be distractingly controversial and dampen the enthusiasm he had just worked so hard to ignite. It has also been largely absent from the websites of leading environmental advocacy organisations – although this now seems to be changing. It is unmentioned in the celebrated book Dire Predictions, written by the climate scientists Michael E Mann and Lee R Kump. After forecasting existential climate disasters, the authors recommend that we substitute clotheslines for electric dryers and commute by bicycle. Among their suggestions, there is no reference to the everyday process that is, according to the research director of Project Drawdown – a collection of nearly 200 environmental scientists and thought leaders dedicated to identifying solutions to address climate change – “the most important contribution every individual can make to reversing global warming”.

Over the past couple of years, I ate meat a number of times. Usually burgers. How could I argue for radical change while eating meat for comfort?

What I am thinking of is the fact that we cannot save the planet unless we significantly reduce our consumption of animal products. This is not my opinion, or anyone’s opinion. It is the inconvenient science. Animal agriculture produces more greenhouse gas emissions than the entire transportation sector (all planes, cars and trains), and is the primary source of methane and nitrous oxide emissions (which are 86 and 310 times more powerful than CO 2 , respectively). Our meat habit is the leading cause of deforestation, which releases carbon when trees are burned (forests contain more carbon than do all exploitable fossil-fuel reserves), and also diminishes the planet’s ability to absorb carbon. According to a recent report from the Intergovernmental Panel on Climate Change, even if we were to do everything else that is necessary to save the planet, it will be impossible to meet the goals of the Paris Climate Accord if we do not dramatically reduce our consumption of animal products.

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Why is this subject avoided? Conversations about meat, dairy and eggs make people defensive. They make people annoyed. It’s far easier to vilify the fossil fuel industry and its lobbyists – which are without a doubt deserving of our vilification – than to examine our own eating habits. No one who isn’t a vegan is eager to go there, and the eagerness of vegans can be a further turnoff. But we have no hope of tackling climate change if we can’t speak honestly about what is causing it, as well as our potential to change in response.

It is hard to talk about our need to eat fewer animal products both because the topic is so fraught and because of the sacrifice involved. Most people like the taste of meat, dairy and eggs. Most people have eaten animal products at almost every meal since they were children, and it’s hard to change lifelong habits, even when they aren’t freighted with pleasure and identity. Those are meaningful challenges, not only worth acknowledging but necessary to acknowledge. Changing the way we eat is simple compared with converting the world’s power grid, or overcoming the influence of powerful lobbyists to pass carbon-tax legislation, or ratifying a significant international treaty on greenhouse gas emissions – but it isn’t simple.

Facebook Twitter Pinterest ‘Rarely a day has passed when I haven’t craved meat’ … Jonathan Safran Foer. Photograph: Christopher Lane

I certainly haven’t found it to be effortless. In my early 30s, I spent three years researching factory farming and wrote a book-length rejection of it called Eating Animals. I then spent nearly two years giving hundreds of readings, lectures and interviews on the subject, making the case that factory-farmed meat should not be eaten. So it would be far easier for me not to mention that in difficult periods over the past couple of years – while going through some painful personal experiences, while travelling the country to promote a novel when I was least suited for self-promotion – I ate meat a number of times. Usually burgers. Often at airports. Which is to say, meat from precisely the kinds of farms I argued most strongly against. And my reason for doing so makes my hypocrisy even more pathetic: they brought me comfort. I can imagine this confession eliciting some ironic comments and eye-rolling, and some giddy accusations of fraudulence. I wrote at length, and passionately, about how factory farming tortures animals and destroys the environment. How could I argue for radical change, how could I raise my children as vegetarians, while eating meat for comfort?

I wish I had found comfort elsewhere but I am who I am. Even as my commitment to vegetarianism, driven by the issue of animal welfare, has been deepened by a full awareness of meat’s environmental toll, rarely a day has passed when I haven’t craved it. At times I’ve wondered if my strengthening intellectual rejection of it has fuelled a strengthening desire to consume it.

Confronting my hypocrisy has reminded me how difficult it is to even try to live my values. Knowing that it will be tough helps make the efforts possible. Efforts, not effort. I cannot imagine a future in which I decide to become a meat-eater again, but I cannot imagine a future in which I don’t want to eat meat. Eating consciously will be one of the struggles that span and define my life.

Future generations will almost certainly look back and wonder why on earth – why on Earth – did we choose our suicide?

We do not simply feed our bellies, and we do not simply modify our appetites in response to principles. We eat to satisfy primitive cravings, to forge and express ourselves, to realise community. We eat with our mouths and stomachs, but also with our minds and hearts. All my different identities – father, son, American, New Yorker, progressive, Jew, writer, environmentalist, traveller, hedonist – are present when I eat, and so is my history. When I first chose to become vegetarian, as a nine-year-old, my motivation was simple: do not hurt animals. Over the years, my motivations changed – because the available information changed, but more importantly, because my life changed. As I imagine is the case for most people, ageing has proliferated my identities. Time softens ethical binaries and fosters a greater appreciation of what might be called the messiness of life.

There is a place at which one’s personal business and the business of being one of seven billion earthlings intersect. And for perhaps the first moment in history, the expression “one’s time” makes little sense. Climate change is not a jigsaw puzzle on the coffee table, which can be returned to when the schedule allows and the feeling inspires. It is a house on fire. The longer we fail to take care of it, the harder it becomes to take care of, and because of positive feedback loops – white ice melting to dark water that absorbs more heat; thawing permafrost releasing huge amounts of methane – we will very soon reach a tipping point of “runaway climate change”, when we will be unable to save ourselves, no matter how much effort we make.

We do not have the luxury of living in our time. We cannot go about our lives as if they were only ours. In a way that was not true for our ancestors, the lives we live will create a future that cannot be undone. The word “crisis” derives from the Greek krisis, meaning “decision”.

Future generations will almost certainly look back and wonder why on earth – why on Earth – did we choose our suicide? Perhaps we could plead that the decision wasn’t ours to make: as much as we cared, there was nothing we could do. We didn’t know enough at the time. Being mere individuals, we didn’t have the means to enact consequential change. We didn’t run the oil companies. We weren’t making government policy. The ability to save ourselves, and save them, was not in our hands. But that would be a lie.

Our attention has been fixed on fossil fuels, which has given us an incomplete picture of the planetary crisis and led us to feel that we are hurling rocks at a Goliath far out of reach. Even if they are not persuasive enough on their own to change our behaviour, facts can change our minds, and that’s where we need to begin. We know we have to do something, but “we have to do something” is usually an expression of incapacitation, or at least uncertainty. Without identifying the thing that we have to do, we cannot decide to do it.

Facebook Twitter Pinterest Forest fires in Altamira, Para state, Brazil … ‘Our meat habit is the leading cause of deforestation, which releases carbon when trees are burned’ Photograph: João Laet/AFP/Getty Images

Climate change is a crisis that will always be simultaneously addressed together and faced alone. The four highest impact things an individual can do to tackle the planetary crisis are: have fewer children; live car-free; avoid air travel; and eat a plant-based diet. Most people are not in the process of deciding whether to have a baby. Few drivers can simply decide to stop using their cars. A sizable portion of air travel is unavoidable. But everyone will eat a meal relatively soon and can immediately participate in the reversal of climate change. Furthermore, of those four high-impact actions, only plant-based eating immediately addresses methane and nitrous oxide, the most urgently important greenhouse gases.

Some argue that plant-based eating is elitist. They are either misinformed, or knowingly taking the favourite emergency exit of privileged, performatively thoughtful people who don’t want to change what they eat. It is true that a healthy traditional diet is more expensive than an unhealthy one – about $550 (£440) more expensive over the course of a year. And everyone should, as a right, have access to affordable healthy food. But a healthy vegetarian diet is, on average, about $750 (£600) less expensive per year than a healthy meat-based diet. In other words, it is about $200 (£160) cheaper per year to eat a healthy vegetarian diet than an unhealthy traditional diet. Not to mention the money saved by preventing diabetes, hypertension, heart disease and cancer – all associated with the consumption of animal products. Nine per cent of Americans making less than $30,000 per year identify as vegetarian, whereas only 4% of those making more than $75,000 are. People of colour are disproportionately vegetarian. It is not elitist to suggest that a cheaper, healthier, more environmentally sustainable diet is better. But what does strike me as elitist? When someone uses the existence of people without access to healthy food as an excuse not to change, rather than as a motivation to help those people.

Different studies suggest different dietary changes in response to climate change, but the ballpark is pretty clear. The most comprehensive assessment of the livestock industry’s environmental impact was published in Nature in October 2018. After analysing food-production systems from every country around the world, the authors concluded that while undernourished people living in poverty across the globe could actually eat a little more meat and dairy, the average world citizen needs to shift to a plant-based diet in order to prevent catastrophic, irreversible environmental damage. The average US and UK citizen must consume 90% less beef and 60% less dairy.

To prevent catastrophic envir­onmental damage, the average US and UK citizen must consume 90% less beef, 60% less dairy

No animal products for breakfast or lunch would come close to achieving that. It might not amount to precisely the reductions that are asked for, but it’s about right, and easy to remember.

It would be both disingenuous and counterproductive to pretend that eating only plant-based foods before dinner won’t require some adjusting. But I bet that if most people think back over their favourite meals of the past few years – the meals that brought them the most culinary and social pleasure, that meant the most culturally or religiously – virtually all of them would be dinners.

And we have to acknowledge that change is inevitable. We can choose to make changes, or we can be subject to other changes – mass migration of climate refugees, disease, armed conflict, a greatly diminished quality of life – but there is no future without change. The luxury of choosing which changes we prefer has an expiration date.

Doing what needs to be done will involve invention (such as creating veggie burgers that are indistinguishable from beef burgers), and legislation (such as adjusting farm subsidies and holding animal agriculture responsible for its environmental destruction), and bottom-up advocacy (such as college students demanding their cafeterias do not serve animal products before dinner), and top-down advocacy (such as celebrities spreading the message that we cannot save the planet without changing how we eat).

Emphasising individual responsibility doesn’t need to distract from corporate and federal responsibility. We absolutely need structural change – we need a global shift away from fossil fuels and towards renewable energy. We need to enforce something akin to a carbon tax, mandate environmental-impact labels for products, replace plastic with sustainable solutions and build walkable cities. We need to end subsidies to the factory farming industry, and hold it accountable for the environmental destruction it incurs. We need to ethically address the west’s relationship to the global south. We might even need a political revolution. These changes will require shifts that individuals alone cannot realise. But putting aside the fact that collective revolutions are made up of individuals, led by individuals, and reinforced by thousands of individual revolutions, we would have no chance of achieving our goal of limiting environmental destruction if individuals don’t make the very individual decision to live differently.

Every time we say “crisis”, we are also saying “decision”. The word “decision” derives from the Latin decidere, which means “to cut off”. Every decision requires loss, not only of what we might have done otherwise but of the world to which our alternative action would have contributed. Often that loss feels too small to notice; sometimes it feels too large to bear. Usually, we just don’t think about our decisions in those terms. We live in a culture of historically unprecedented acquisition. We are prompted to define ourselves by what we have: possessions, dollars, views and likes. But we are revealed by what we release.

Climate change is the greatest crisis humankind has ever faced, and it is one that will always be simultaneously addressed together and faced alone. We cannot keep eating the kinds of meals we have known and also keep the planet we have known. We must either let some eating habits go or let the planet go. It is that straightforward, and that fraught.

• We are the Weather by Jonathan Safran Foer is published on 10 October by Hamish Hamilton (£16.99). To order a copy go to guardianbookshop.com. Free UK p&p on all online orders over £15.