Johann Hari

After Labour's long death-march to Henley cemetery last week, it's plain the future isn't Brown; it's black. No party has ever heaved itself out of a grave this deep in just two years. The next general election is lost – so for its remaining years in office, the Government has a contracted mission. They have to leave the Labour Party with enough sense of shared mission – enough sticky social democratic glue – to hold it together when it emerges, bankrupt and battered, from the 2010 landslide loss. If all the party's activists remember of 13 years of Labour rule is the Iraqi inferno and Heathrow and casinos, they may well leave it by the roadside to die.

Harriet Harman's Equality Bill is a glistening reminder of what a Labour government is for, but you wouldn't know it from the deafening cannon-fire of lies that have been blasted in her direction. The Bill takes some of the most blatant blocks on British people getting to use their talents – sexism, racism, homophobia, ageism, and prejudice against the disabled – and tries carefully to unpick them.

Let's focus on sexism, since it affects the largest number. The facts are plain: women in full-time work earn 17 per cent less than men. Women in part-time work earn 40 per cent less. Harman asks: "Do we think she is 40 per cent less hard-working, less intelligent, less qualified?" After a decade of the Government asking businesses nicely to change their ways, the situation is barely improving: the average woman is still cheated out of £330,000 in her career. At the current rate, there will be equal pay in Britain in 2088 – when everybody reading this article is dead.

So Harman believes the Government needs to act. Does anybody disagree? Yes, actually. Some right-wing critics have tried to stop her right there, at the first premise. The Daily Mail has announced that women "choose less well-paid jobs" because they want "more time with their families". In reality, this is a factor in lower pay for women – but it is relatively small. How do we know? Because the pay gap sets in and swells long before women have kids.

The Women and Work Commission found women with first-class degrees are earning considerably less than equally-qualified men virtually as soon as they enter the workplace. Within five years, the pay gap for highly qualified women is 15 percent – even though the women are on average just 26, and almost none have had babies.

All Harman has done is propose some straightforward measures, adopted in almost all the countries with narrower gaps. She wanted all employers to have to calculate the pay gap between men and women in their organisation, and publish it. It would take an afternoon. Women could then start to figure out if they were being cheated, and put it right workplace-by-workplace.

But there was fierce resistance from the Business Secretary, John Hutton, in Cabinet, so Harman had to accept a frustrating compromise. The public sector will now publish the gap and Harman-ise. Any private firms that sell to them will also at least have to add the gap up, and present it when bidding for government contracts. The rest of the private sector will be left as they are today.

For this, Harman has been called in the press "a patronising cow" and an "idiot" who is "hanging on by her pretty little fingernails". The metal-fetishising eunuch Jeremy Clarkson squealed: "Equality was tried very publicly in Russia. Rich people were shot. Everyone worked in a tractor factory." Uh ... there is a small difference between a pay audit and a gulag, Jeremy. He then wrote: "No matter how many times I applied, Sir Alex Ferguson would not employ me as his next striker. Under Harperson's regime, I'd be able to take him to court." Of course, dear.

The critics have fixated on one tiny part of the Bill that lets employers take gender or race into account if they have a skewed workforce. All this means is that if, say, a primary school is staffed only by women, the headteacher can legally decide to pick a man to balance things out, provided he is equally good. Yet the Daily Express reported this on its front page as: "White Men To Face Jobs Ban." It's hard to have a functioning democracy when the press lies en masse this blatantly.

When they have run out of all other arguments, the gap-dodging critics complain we can't afford gender equality while the economy sighs into recession. But wasting the education and talents and skills of a hefty chunk of the country is actually a drag on the economy – one that costs us £23bn a year. When Norway demanded that 40 per cent of all seats on corporate boards be female, business growth shot up. When McKinsey studied the effect of having women in senior positions, they found it boosted stock-price growth by 53 per cent. This shows that white men (like me) suffer when talent can't rise. We can't afford not to lift the sexist brakes.

The cultural chasm between Labour and the Tories on this was illustrated with Carry On garishness last week. On the Labour benches, there was a sea of men and women, black and white, gay and straight, trying to outlaw the most egregious forms of discrimination. Opposite there was a braying row of public schoolboys calling it "completely and utterly outrageous".

The culture among Tory MPs was compressed into a few sentences when one of them, David Heathcote-Amory, saw a black woman walking on the member's terrace and demanded to know if she was an MP. "Yes, I am actually. Are you?" Dawn Butler replied. He snapped to his colleagues: "They're letting anybody in nowadays."

When you see them massed, you realise David Cameron's Conservatives are an unreconstructed rich-boys-only club, opposed to basic gender equality. There are more Old Etonians on their benches than women (they're just 9 per cent), and the Shining Leader is even a member of White's, a club that bans females from setting foot inside. The only influential woman in Cameron's circle is his dowager-heiress wife, who spends her time designing £1,000 handbags. The fact the Tories' modernising-sheen soon rubs off matters: Boris ran as a "compassionate Conservative", but his first act as Mayor was to cancel half-price bus fares for 130,000 of the poorest Londoners.

When Barbara Castle pushed through the Equal Pay Act in 1970, the same predictions of economic apocalypse and misogynist insults were machine-gunned at her, word-for-word – but today we look back on it as one of the great achievements of the Wilson years. In a more equal Britain 30 years from now, we will feel the same about Harriet Harman – and we will remember this Bill in dark times as one of the reasons to fight for a Labour government.

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POSTSCRIPT: In my column today, I talk about the Equalities Bill – but I didn’t have room to ruminate on one of its best parts. (If my column was about 9,000 words, I think I could squeeze in each point I want to make on the subject du jour… Feel free to lobby our new editor to give me this space...)

In Britain today, there are people who can’t travel, can’t get a credit card, and can’t find a job, because of a factor totally beyond their control – their age. A super-healthy 77-year old friend of mine can’t afford to visit her son in Spain – one of the few pleasures in her life – any more, because when she hit 75 the cost of travel insurance suddenly sky-rocketed from £175 to more than £850. Her health hadn’t changed at all.

Help the Aged have great files stuffed full of ageism case studies. Here’s just one: “Joy was told [by the NHS] that her husband, a chair of school governors and DIY enthusiast, was not a life worth fighting for. Why? Because he was 76 years old.”

The Equalities Bill will ensure that if this happens again, the people responsible will end up in court. The zimmer-frame of progress has just rolled on a few inches.

Do you find yourself staring at the television and pining for a good leader – a person who will rise and make the world right again? Do you long for a Mandela, a Churchill, a Gandhi? Then grow up. Our political debate – what passes for it – increasingly focuses on a search for an elusive Messianic leader who will show us the way. This is the opposite of rational politics.

This search for leaders is based on a desire to return to childhood – to snuggle into the political cot and close our eyes, knowing daddy is outside watching over us. The highest compliment we pay to a politician is to call him "father of the nation". I feel this urge too. It is difficult and disturbing to try to figure out what is wrong in the world, and how to put it right. How much more tempting to simply snuffle out somebody who you think is good and decent and kind, elect them, and assume they will sort it all out.

But this discourages us from doing the one thing that might actually solve these problems – figuring out solutions for ourselves then going out and campaigning to make them happen. Every civilising advance in history – from workers' rights to women's rights to gay rights – was won because ordinary people banded together and agitated for it. If we had waited for a good leader to hand it down from above, we would still be waiting today.

There is a bigger danger still. It is that, in finding a "good" leader, we then blindly follow them into dark and fetid places. Let's look first at a leader whose ninetieth birthday we are celebrating this week: Nelson Mandela. Nobody needs to be reminded of his stunning heroism in the fight against apartheid. But because they were so awed by that, most South Africans followed him unquestioningly as he perpetuated economic apartheid – and worsened the most extreme economic inequality on earth.

Apartheid was not just a system of laws; it was an economic system where a tiny white elite owned almost everything. By 1990, the elite realised they could no longer maintain the laws – but they fought desperately to maintain economic control. They demanded that the land and resources they had stolen from poor blacks be recognised in the constitution as theirs, and never redistributed. They demanded that the new democracy pick up all of apartheid's debts, making spending to lift up the poor majority impossible. They demanded the recognition of "intellectual property rights", making the distribution of cheap Aids drugs unaffordable. They demanded their apartheid finance minister and head of the Central Bank continue in position. Western governments, the International Monetary Fund and World Bank piled in behind them in support.

Mandela agreed to it all. He discreetly buried the ANC's Freedom Charter, with its commitments to clean water, free healthcare and land for all. The result is that today whites own 70 per cent of the South African economy, despite being only 10 per cent of the population. Mandela believed this deal was the only way to prevent white flight and increase poverty. But he was wrong. Since the fall of apartheid, average life expectancy has fallen by 13 years. The black unemployment rate has doubled. This isn't because white ruled ceased; it is because it continues today, with a new black corporate logo.

People who are heroic in one respect can be fools or monsters in another. If we look at two of the most admired leaders of the twentieth century, this becomes even clearer. Mahatma Gandhi's shimmering qualities don't need to be rehearsed here – but who now remembers that he killed his wife, and told Europeans to allow the Nazis to conquer our continent?

The British occupiers of India jailed Gandhi and his wife Kasturba in 1942, and she soon developed bronchial pneumonia. Their son Devadas turned to the obvious solution: penicillin. But because of his Hindu fundamentalism, Gandhi believed "Western" medicine – medicine that had been tested in clinical trials to make sure it works – was immoral. He said she should drink muddy water from the "Holy" Ganges instead. Whenever Kasturba flickered into consciousness, he told her she would "bankrupt [his] faith" and hers if she took penicillin. So she died. Six weeks later, Gandhi himself got ill with malaria – and glugged down the "Western" medicine happily. For the rest of his life, he continued to condemn the medicines that had saved his life, and told his followers to eschew them.

Gandhi's response to Nazism was even worse. He said the peoples of Europe should let Hitler and Mussolini conquer and "allow yourselves, man, woman and child to be slaughtered". And the Jews? They "should have offered themselves to the butcher's knife. They should have thrown themselves into the sea from cliffs ... Collective suicide would have been heroism." It would be "immoral", he said, to fight back. Again, this was a result of his absurd superstitious beliefs.

What about Gandhi's nemesis, Winston Churchill? Today we only remember his heroic opposition to Nazism. But while he was against gassing and tyranny in Europe, he was passionately in favour of it for "uncivilised" human beings whose riches he wanted to seize. In the 1920s, Iraqis rose up against British imperial rule, and Churchill as Colonial Secretary thought of a good solution: gas them. He wrote: "I do not understand this squeamishness... I am strongly in favour of using poisoned gas against uncivilised tribes." It would "spread a lively terror". He was quite clear about why Britain should do this. He explained: "We have engrossed to ourselves an altogether disproportionate share of the wealth and traffic of the world... mainly acquired by violence, largely maintained by force."

Don't misunderstand me. There are no perfect leaders, but there are always better and worse ones. I would have backed Gandhi against Churchill, and Churchill against Hitler – while always condemning their flaws.

You can see this principle in the current US election. Barack Obama is considerably better than John McCain – but he too has his dreadful drawbacks we will have to oppose. He has pledged, if he wins, "Jerusalem will remain the capital of Israel, and it must remain undivided" – a pledge that would make any proper two-state solution impossible. He has defended the right of Colombia's hard-right government to invade its neighbours. Faced with this, you can't give up: support the great parts of his programme – like expanding healthcare in the US – and oppose the bad. Be a political adult.

Human beings are invariably flawed. Every person who is capable of moments of greatness is also capable of cruelty or stupidity. The only way to check this is for us to be constantly watching each other – even the best amongst us – and to never be blinded by admirable acts. We will never reach a point where we find the good leader and can sigh, sit back, and relax. If you care about the state of the world, you have to keep watching and pressuring and fighting, forever.

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Wherever the London Labour tribe gathers, they panic and weep and commiserate about Gordon Brown – and then a new whispered discussion begins. Who should be Labour’s candidate against Boris in 2012?

The political circumstances will be drastically different. The Conservatives will (alas) almost certainly have been in Downing Street for two years or more. London will be on the brink of staging the Olympic Games. If we are a jittery city – with the Games running behind schedule and over-budget – Boris won’t be able to blame a Labour government. But if they look likely to be a success, Boris will probably have the political wind at his back.

Snuffling out mayoral candidates in a parliamentary system isn’t easy. A political model dominated by party discipline doesn’t throw up the charismatic individualists you need for City Hall. It pasteurises politicians, training them to be dull and not distract from The Leader.

The obvious contender is come-back Ken. He has already declared his intention to run again at the age of 67, saying this weekend: “Tell me if this is too much information, but my prostate is as smooth as a billiard ball.” I’m a fan of his, and I think his achievements will look even more impressive after the Boris and Dave Etonian wall-game has dragged on for two years.

But I think there is a better Labour candidate still: Oona King. She was born in North London to a Jewish mother and a black-American father, and educated at the local comp. All through her career in London politics, she has been driven by the issues that dominate City Hall: housing and transport. If you even mention the word ‘housing’ in her presence, a three-hour lecture tumbles out about overcrowding and damp and council estates, all jammed with statistics, stories from her old Tower Hamlets constituency, and the burning hunger to do more than Boris ever would.

Oona is down-to-earth, clever, and a Londoner to her fingertips. Like Ken and Boris, everybody feels they know her. The issue that brought her career crashing down – Iraq – won’t be a big factor, since City Hall has no say on foreign policy. The only reason that she might hold back is she has just adopted a little boy and wants to spend time with him.

By 2012, we may well have a mixed-race President of the US by then. What better symbol of London than to pick a black-Jewish woman who has dedicated her career to lifting up the poor of all races as our leader?

This article was also accompanied by some smaller boxes:

Box I:

The tube is crammed with posters telling us - quite rightly - we will be prosecuted if we are “abusive” to the staff. But can’t we cut a deal: we won’t be rude to the tube workers if they stop being so bloody rude to us? I was about to get on the Northern Line recently when I saw a tube worker putting up a sign saying: “Today, there is a special service between Camden Town and Edgware.” With a friendly smile, I asked what they meant. “It means,” he snapped, “there is a special service.” Right. Does that mean there are more trains? Fewer? A replacement bus? “No,” he said, looking at me as if I was a simpleton. “It’s a special service. What part of that don’t you understand?”

Box II:

Is Lyndsay Duncan Britain’s most under-rated actress? I just saw her in the debut play by 20 year-old Polly Stenam ‘That Face’ at the Duke of York’s Theatre, where she plays an alcoholic mother slowly slipping away from sanity. She can pack decades of grief and loss and pain into a single sigh. In this play, she has a two-minute conversation with the speaking clock that condenses more truth than most actresses achieve in a career. Yet she is not yet ranked alongside Judi Dench and Eileen Atkins as one of our greats. Is it because she’s not just talented, but beautiful and blonde?

Box III:

I see Bernard Manning’s ashes have been turned into a mosaic to stand forever outside his Embassy Club in the North. (Presumably he wasn’t allowed to place it in Hitler’s bunker.) This set me off on a google-hunt for what to do with my own remains. It turns out you can have them turned into a diamond, fired into space, or pressed into a Frisbee. (“Let’s go throw Dad’s remains around the park!”) I’d like mine to be mixed with seed and fed to the pigeons in Trafalgar Square so they fly me all over London. Every time my friends are swooped on by these winged diseased rats, they’ll sense my presence, and smile.

As a country, we can spend countless hours discussing rival teams of men kicking a piece of plastic into a net. But we are all supposed to be shame-faced about discussing the fantastically complex dramas called Reality TV. Well, I'm not.

Have the sinews of racism and snobbery been more truthfully traced than in the showdown between Shilpa Shetty and Jade Goody? Has the reality of sexism in the workplace been laid out more rivettingly than in Alan Sugar's annual picking of amiable, malleable men over competent, dynamic women to be his apprentice? Now this glorious genre has dramatised the clash within British Islam – between secularisers and fanatics – with the same concision.

Reality TV has long shown a face of British Islam that contrasts with the murderous smirk of the Tube-bomber Mohammed Sidiq Khan. It gave us Chico Slimani, the buff, rippling ex-Chippendale who blagged his way through The X-Factor; Kemal Shahin, the smart, tart young gay man who dominated Big Brother 5; and Saira Khan, the feminist entrepreneur from The Apprentice who refuses to let her religion be hijacked by "bearded old men from the Middle East". They represent the first fragile shoots of a secularised Islam that – like most Christianity and Judaism in Europe – can be shrunk until it is a matter of custom and private conscience.

But on our reality TV shows, this has always been a one-sided fight. Fundamentalists, by their you're-all-damned nature, are not inclined to take part in reality TV. Until now.

If you were told the biographies of Big Brother contestants Mohamed Mohamed and Alex De-Gale, you wouldn't find it hard to guess which one is the fundamentalist. Mohamed was born in Somalia in 1985. When he was five years old, he saw his mother being held at gunpoint, and thought she was going to die. Since then, he has spent most of his life fleeing from one civil war to another – until, finally, he was granted asylum in Britain. De-Gale was born in the same year in south London, to black British parents. She is now a lithe accounts executive with high cheekbones, short skirts, a BMW, and a seven-year old daughter she brings up on her own.

You guessed wrong. They wouldn't use these terms, but Mohamed became a convinced secularist on the run from Somalia, while Alex learned a Wahhabbi interpretation of Islam on the streets of Tottenham. This emerged, as everything does on Big Brother, through a thicket of trivia. Mohamed's birthday fell a week into his stay in the Big Brother house, so the producers threw him a party, and let him pick the theme. Remembering a fun night he'd had at university, he said he wanted the male housemates to dress as women, and vice versa. Everyone cheered and howled for alcohol.

Except Alex. "First and foremost," she said, "I am a Muslim." And that meant the idea of a man dressing as a woman "made me feel sick". Jabbing her finger and shouting, she said to Mohamed: "Tell it to Allah [that] it's all in the name of fun. It's bad enough that we drink and smoke ... You're supposed to be a Muslim man, someone I can look up to for guidance. You will have my friends and family in uproar. I am disgraced by you ... 85 per cent of the people I know are Muslims. And trust me – the sheer horror they would have experienced ... [You have] disgraced Islam."

"You can't tell me I'm a bad Muslim," Mohamed replied. "I am old enough to be responsible for myself. Don't bring religion into it!" She snapped back: "It is! There's nothing else!" Alex was so enraged she announced she has "gangster friends" and, if she was evicted, "I get to go out [and] see everyone's friends, I get to see their family. I get to do the shit that I wanna do. Pow, pow, pow." This threat wasn't necessarily idle: Alex has a restraining order against her after she waged a "hate campaign" against a former friend.

In that little exchange, you see the contrast between two understandings of Islam. I live in the middle of the Muslim East End, and I see this raw, rubbing conflict being played out every day.

Alex believes that Islam offers Absolute Judgements, immutably cast in stone in the Koran. These are (of course) hellishly patriarchal, since they were formulated by illiterate desert merchants in the seventh century AD. She has been taught there is "nothing else". Later, she explained to another housemate that Islam forbids drinking and smoking. "What can you do then?" he asked. "Pray." That's all. If you see somebody acting in a way your pre-modern system judges to be "sick", is it perfectly moral to threaten to kill them?

Mohamed, by contrast, sees the religion as consisting of metaphors and moral guidance – and he thinks it has limits. There are places it shouldn't go. "She always brings religion into an equation that religion has nothing to do [with]," he said angrily. But what makes this argument even more fascinating – turning it from a scene by George Bernard Shaw into one by David Mamet – is the ambiguities within Alex's character. She howls about the morals of seventh-century Arabia, when they would have her stoned to death. Almost every Islamist I have met has this dissonance running through them. The 9/11 hijackers went to a strip-bar and got drunk before staging their cry for the construction of a Caliphate that would kill them for doing just that. The "moral" vision they believe in is so inhuman even they can't follow it.

So how do we make sure relaxed secularists like Mohamed, Chico, Kemal and Saira beat Alex's wing of Islam? They have answers of their own. They all start with us ceasing to show multicultural politeness towards fanatical theocrats. Saira Khan – who as a teenager was whipped by her father with a coat-hanger for letting her legs show – says we need to call misogyny and gay-bashing by their proper names. Muslims are not a homogenous block represented by the elderly Saudi-trained Mullahs who taught Alex their totalitarian model of Islam.

But we are handing more and more Muslim children over to them to indoctrinate. Faith schools herd the kids of Muslim parents away from the rest of us and pickle them in stale dogmas. Khan – who has spoken at many Muslim schools – says they "encourage segregation and women to be submissive". When I called Kemal, he was even more emphatic, saying: "I would have died in one of these Muslim-only faith schools." There, the Alexes can mass and shout down the Mohameds with the backing of their teachers. (Our oil-addicted foreign policy makes it easier to tell them the democratic society outside is evil.) Yet the Government is not dismantling faith schools – it is building more of them.

So watch that row between Mohamed and Alex again. It is a shouting match – "This is nothing to do with religion!" "Tell it to Allah!" – playing out in a million variations in souqs and madrassahs and Muslim homes across the world. Now that's what I call reality television.

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This spring, I took a month-long road trip across a country that we – you, me and everyone we know – are killing. One day, not long into my journey, I travelled over tiny ridges and groaning bridges on the back of a motorbike to reach the remote village of Munshigonj. The surviving villagers – gaunt, creased people – were sitting by a stagnant pond. They told me, slowly, what we have done to them.

Ten years ago, the village began to die. First, many of the trees turned a strange brownish-yellow colour and rotted. Then the rice paddies stopped growing and festered in the water. Then the fish floated to the surface of the rivers, gasping. Then many of the animals began to die. Then many of the children began to die.

The waters flowing through Munshigonj – which had once been sweet and clear and teeming with life – had turned salty and dead.

Arita Rani, a 25-year-old, sat looking at the salt water, swaddled in a blue sari and her grief. "We couldn't drink the water from the river, because it was suddenly full of salt and made us sick," she said. "So I had to give my children water from this pond. I knew it was a bad idea. People wash in this pond. It's dirty. So we all got dysentery." She keeps staring at its surface. "I have had it for 10 years now. You feel weak all the time, and you have terrible stomach pains. You need to run to the toilet 10 times a day. My boy Shupria was seven and he had this for his whole life. He was so weak, and kept getting coughs and fevers. And then one morning..."

Her mother interrupted the trailing silence. "He died," she said. Now Arita's surviving three-year-old, Ashik, is sick, too. He is sprawled on his back on the floor. He keeps collapsing; his eyes are watery and distant. His distended stomach feels like a balloon pumped full of water. "Why did this happen?" Arita asked.

It is happening because of us. Every flight, every hamburger, every coal power plant, ends here, with this. Bangladesh is a flat, low-lying land made of silt, squeezed in between the melting mountains of the Himalayas and the rising seas of the Bay of Bengal. As the world warms, the sea is swelling – and wiping Bangladesh off the map.

Deep below the ground of Munshigonj and thousands of villages like it, salt water is swelling up. It is this process – called "saline inundation" – that killed their trees and their fields and contaminated their drinking water. Some farmers have shifted from growing rice to farming shrimp – but that employs less than a quarter of the people, and it makes them dependent on a fickle export market. The scientific evidence shows that unless we change now, this salt water will keep rising and rising, until everything here is ocean.

I decided to embark on this trip when, sitting in my air-conditioned flat in London, I noticed a strange and seemingly impossible detail in a scientific report. The International Panel on Climate Change (IPCC) – whose predictions have consistently turned out to be underestimates – said that Bangladesh is on course to lose 17 per cent of its land and 30 per cent of its food production by 2050. For America, this would be equivalent to California and New York State drowning, and the entire mid-West turning salty and barren.

Surely this couldn't be right? How could more than 20 million Bangladeshis be turned into refugees so suddenly and so silently? I dug deeper, hoping it would be disproved – and found that many climatologists think the IPCC is way too optimistic about Bangladesh. I turned to Professor James Hansen, the director of Nasa's Goddard Institute for Space Studies, whose climate calculations have proved to be more accurate than anybody else's. He believes the melting of the Greenland ice cap being picked up by his satellites today, now, suggests we are facing a 25-metre rise in sea levels this century – which would drown Bangladesh entirely. When I heard this, I knew I had to go, and see.

1. The edge of a cliff

The first thing that happens when you arrive in Dhaka is that you stop. And wait. And wait. And all you see around you are cars, and all you hear is screaming. Bangladesh's capital is in permanent shrieking gridlock, with miles of rickshaws and mobile heaps of rust. The traffic advances by inches and by howling. Each driver screams himself hoarse announc-ing – that was my lane! Stay there! Stop moving! Go back! Go forward! It is a good-natured shrieking: everybody knows that this is what you do in Dhaka. If you are lucky, you enter a slipstream of traffic that moves for a minute – until the jams back up and the screaming begins once more.

Around you, this megalopolis of 20 million people seems to be screaming itself conscious. People burn rubbish by the roadside, or loll in the rivers. Children with skin deformities that look like infected burns try to thrust maps or sweets into your hand. Rickshaw drivers with thighs of steel pedal furious-ly as whole families cling on and offer their own high-volume traffic commentary to the groaning driver, and the groaning city.

I wanted to wade through all this chaos to find Bangladesh's climate scientists, who are toiling in the crannies of the city to figure out what – if anything – can be saved.

Dr Atiq Rahman's office in downtown Dhaka is a nest of scientific reports and books that, at every question, he dives into to reel off figures. He is a tidy, grey-moustached man who speaks English very fast, as if he is running out of time.

"It is clear from all the data we are gathering here in Bangladesh that the IPCC predictions were much too conservative," he said. He should know: he is one of the IPCC's leading members, and the UN has given him an award for his unusually prescient predictions. His work is used as one of the standard textbooks across the world, including at Oxford and Harvard. "We are facing a catastrophe in this country. We are talking about an absolutely massive displacement of human beings."

He handed me shafts of scientific studies as he explained: "This is the ground zero of global warming." He listed the effects. The seas are rising, so land is being claimed from the outside. (The largest island in the country, Bhola, has lost half its land in the past decade.) The rivers are super-charged, becoming wider and wider, so land is being claimed from within. (Erosion is up by 40 per cent). Cyclones are becoming more intense and more violent (2007 was the worst year on record for intense hurricanes here). And salt water is rendering the land barren. (The rate of saline inundation has trebled in the past 20 years.) "There is no question," Dr Rahman said, "that this is being caused primarily by human action. This is way outside natural variation. If you really want people in the West to understand the effect they are having here, it's simple. From now on, we need to have a system where for every 10,000 tons of carbon you emit, you have to take a Bangladeshi family to live with you. It is your responsibility." In the past, he has called it "climatic genocide".

The worst-case scenario, Dr Rahman said, is if one of the world's land-based ice-sheets breaks up. "Then we lose 70 to 80 per cent of our land, including Dhaka. It's a different world, and we're not on it. The evidence from Jim Hansen shows this is becoming more likely – and it can happen quickly and irreversibly. My best understanding of the evidence is that this will probably happen towards the end of the lifetime of babies born today."

I walked out in the ceaseless churning noise of Dhaka. Everywhere I looked, people were building and making and living: my eyes skimmed up higher and higher and find more and more activity. A team of workers were building a house; behind and above them, children were sewing mattresses on a roof; behind and above them, more men were building taller buildings. This is the most cramped country on earth: 150 million people living in an area the size of Iowa. Could all this life really be continuing on the crumbling edge of a cliff?

2. 'It is like the Bay is angry'

I was hurtling through the darkness at 120mph with my new driver, Shambrat. He was red-eyed from chewing pan, a leaf-stimulant that makes you buzz, and I could see nothing except the tiny pools of light cast by the car. They showed we were on narrow roads, darting between rice paddies and emptied shack-towns, in the midnight silence. I kept trying to put on my seatbelt, but every time Shambrat would cry, "You no need seatbelt! I good driver!" and burst into hysterical giggles.

To see if the seas were really rising, I had circled a random low-lying island on the map called Moheshkhali and asked Shambrat to get me there. It turned out the only route was to go to Coxs Bazar – Bangladesh's Blackpool – and then take a small wooden rowing boat that has a huge chugging engine attached to the front. I clambered in alongside three old men, a small herd of goats, and some chickens. The boat was operated by a 10-year-old child, whose job is to point the boat in the right direction, start the engine, and then begin using a small jug to frantically scoop out the water that starts to leak in. After an hour of the deafening ack-ack of the engine, we arrived at the muddy coast of Moheshkhali.

There was a makeshift wooden pier, where men were waiting with large sacks of salt. As we climbed up on to the fragile boards, people helped the old men lift up the animals. There were men mooching around the pier, waiting for a delivery. They looked bemused by my arrival. I asked them if the sea levels were rising here. Rezaul Karim Chowdry, a 34-year-old who looked like he is in his fifties, said plainly: "Of course. In the past 30 years, two-thirds of this island has gone under the water. I had to abandon my house. The land has gone into the sea." Immediately all the other men start to recount their stories. They have lost their houses, their land, and family members to the advance.

They agreed to show me their vanishing island. We clambered into a tuc-tuc – a motorbike with a carriage on the back – and set off across the island, riding along narrow ridges between cordoned-off areas of sand and salt. The men explained that this is salt-farming: the salt left behind by the tide is gathered and sold. "It is one of the last forms of farming that we can still do here," Rezaul said. As we passed through the forest, he told me to be careful: "Since we started to lose all our land, gangs are fighting for the territory that is left. They are very violent. A woman was shot in the crossfire yesterday. They will not like an outsider appearing from nowhere."

We pulled up outside a vast concrete structure on stilts. This, the men explained, is the cyclone shelter built by the Japanese years ago. We climbed to the top, and looked out towards the ocean. "Do you see the top of a tree, sticking out there?" Rezaul said, pointing into the far distance. I couldn't see anything, but then, eventually, I spotted a tiny jutting brown-green tip. "That is where my house was." When did you leave it? "In 2002. The ocean is coming very fast now. We think all this" – he waved his hand back over the island – "will be gone in 15 years."

Outside the rusty house next door, an ancient-looking man with a long grey beard was sitting cross-legged. I approached him, and he rose slowly. His name was Abdul Zabar; he didn't know his age, but guessed he is 80. "I was born here," he said. "There" – and he points out to the sea. "The island began to be swallowed in the 1960s, and it started going really quickly in 1991. I have lost my land, so I can't grow anything... I only live because one of my sons got a job in Saudi Arabia and sends money back to us. I am very frightened, but what can I do? I can only trust in God." The sea stops just in front of his home. What will you do, I asked, if it comes closer? "We will have nowhere to go to."

I was taken to the island's dam. It is a long stretch of hardened clay and concrete and mud. "This used to be enough," a man called Abul Kashin said, "but then the sea got so high that it came over the dam." They have tried to pile lumps of concrete on top, but they are simply washed away. "My family have left the island," he continued, "They were so sad to go. This is my homeland. If we had to leave here to go to some other place, it would be the worst day of my life."

Twenty years ago, there were 30,000 people on this island. There are 18,000 now – and most think they will be the last inhabitants.

On the beach, there were large wooden fishing boats lying unused. Abu Bashir, a lined, thin 28-year-old, pointed to his boat and said, "Fishing is almost impossible now. The waves are much bigger than they used to be. It used to be fine to go out in a normal [hand-rowed] boat. That is how my father and my grandfather and my ancestors lived.

"Now that is impossible. You need a [motor-driven] boat, and even that is thrown about by the waves so much. It's like the bay is angry."

The other fishermen burst in. "When there is a cyclone warning, we cannot go out fishing for 10 days. That is a lot of business lost. There used to be two or three warnings a year. Last year, there were 12. The sea is so violent. We are going hungry."

Yet the islanders insisted on offering me a feast of rice and fish and eggs. I was ushered into the council leader's house – a rusty shack near the sea – and the men sat around, urging me to tell the world what is happening. "If people know what is happening to us, they will help," they said. The women remained in the back room; when I glimpsed them and tried to thank them for the food, they giggled and vanished. I asked if the men had heard of global warming, and they looked puzzled. "No," they said. We stared out at the ocean and ate, as the sun slowly set on the island.

3. No hiding place

Through the morning mist, I peered out of the car window at the cratered landscape. Trees jutted out at surreal angles from the ground. One lay upside down with its roots sticking upwards towards the sky, looking like a sketch for a Dali painting. Shambrat had spat out his pan and was driving slowly now. "There are holes in the ground," he said, squinting with concentration. "From the cyclone. You fall in..." He made a splattering sound.

It was here, in the south of Bangladesh, that on 15 November last year, Cyclone Sidr arrived. It formed in the warmed Bay of Bengal and ripped across the land, taking more than 3,000 people with it. Like Americans talking about 9/11, everybody in Bangladesh knows where they were when Sidr struck. For miles, the upturned and smashed-out houses are intermixed with tents made from blue plastic sheeting. These stretches of plastic were handed out by the charities in the weeks after Sidr, and many families are still living in them now.

There have always been cyclones in Bangladesh, and there always will be – but global warming is making them much more violent. Back in Dhaka, the climatologist Ahsan Uddin Ahmed explained that cyclones use heat as a fuel: "The sea surface temperatures in the Bay of Bengal have been rising steadily for the past 40 years – and so, exactly as you would expect, the intensity of cyclones has risen too. They're up by 39 per cent on average." Again I circled a cyclone-struck island at random and headed for the dot.

The hour-long journey on a wooden rowing boat from the mainland to Charkashem Island passed in a dense mist that made it feel like crossing the River Styx. The spectral outline of other boats could sometimes be glimpsed, before they disappeared suddenly. One moment an old woman and a goat appeared and stared at me, then they were gone.

The island was a tiny dot of mud and lush, upturned greenery. It had no pier, so when the rowing boat bumped up against the sand I had to wade through the water.

I looked out over the silent island, and saw some familiar blue sheeting in the distance. As I trudged towards it, I saw some gaunt teenagers half-heartedly kicking a deflated football. From the sheeting, a man and woman stared, astonished.

"I was in my fields over there," Hanif Mridha said. "I saw the wind start, it was about eight at night, and I saw everything being blown around. I went and hid under an iron sheet, but that was blown away by the wind. The water came swelling up all of a sudden and was crashing all around me. I grabbed one of my children and ran to the forest" – he pointed to the cluster of trees at the heart of the island – "and climbed the tallest one I could reach. I went as high as I could but still the water kept rising and I thought – this is it, I'm going to drown. I'm dying, my children are dying, my wife is dying. I could see everything was under water and people were screaming everywhere. I held there for four hours with my son."

When the water washed away and he came down, everything was gone: his house, his crops, his animals, his possessions. A few days later, an aid agency arrived with some rice and some plastic sheeting to sleep under. Nobody has come since.

His wife, Begum Mridha, took over the story. Their children are terrified of the sea now, and have nightmares every night. They eat once a day, if they're lucky. "We are so hungry," she said. The new home they have built is made from twigs and the plastic sheet. Underneath it, they sleep with their eight children and Begum Mridha's mother. The children lay lethargically there, staring blankly into space over their distended bellies.

Begum Mridha cooks on a lantern. They eat once a day – if that. "It's so cold at night we can't sleep," she said. "The children all have diarrhoea and they are losing weight. It will take us more than two years to save up and get back what we had."

If cyclones hit this area more often, what would happen to you? Hanif looked down. He opened his mouth, but no words came.

4. Bangladesh's Noah

In the middle of Bangladesh, in the middle of my road trip, I tracked down Abul Hasanat Mohammed Rezwan. He was sitting under a parasol by the banks of a river, scribbling frenetically into his notebook.

"The catastrophe in Bangladesh has begun," he said. "The warnings [by the IPCC] are unfolding much faster than anyone anticipated." Until a few years ago, Rezwan was an architect, designing buildings for rich people – "but I thought, is this what I want to do while my country drowns? Create buildings that will be under water soon anyway?"

He considered dedicating his life to building schools and hospitals, "but then I realised they would be under water soon as well. I was hopeless. But then I thought of boats!"

He has turned himself into Bangladesh's Noah, urging his people to move on to boats as the Great Flood comes. Rezwan built a charity – Shidhulai Swanirvar Sangstha, which means self-reliance – that is building the only schools and hospitals and homes that can last now: ones that float.

We clambered on to his first school-boat, which is moored in Singra. In this area there is no electricity, no sewage system, and no state. The residents live the short lives of pre-modern people. But now, suddenly, they have a fleet of these boats, stocked with medicines and lined with books on everything from Shakespeare to accountancy to climatology. Nestling between them, there are six internet terminals with broadband access.

The boat began to float down the Curnai River, gathering scores of beaming kids as it went. Fatima Jahan, an unveiled 18-year-old girl dressed in bright red, arrived to go online. She was desperate to know the cricket scores. At every muddy village-stop, the boat inhaled more children, and I talked to the mothers who were beating their washing dry by the river. "I never went to school, and I never saw a doctor in my life. Now my children can do both!" a thin woman with a shimmering heart-shaped nose stud called Nurjahan Rupbhan told me. But when I asked about the changes in the climate, her forehead crumpled into long frown-lines.

I thought back to what the scientists told me in Dhaka. Bangladesh is a country with 230 rivers running through it like veins. They irrigate the land and give it its incredible fertility – but now the rivers are becoming supercharged. More water is coming down from the melting Himalayan glaciers, and more salt water is pushing up from the rising oceans. These two forces meet here in the heart of Bangladesh and make the rivers churn up – eroding the river banks with amazing speed. The water is getting wider, leaving the people to survive on ever-more narrow strips of land.

Nurjahan took me up to a crumbling river edge, where tree roots jutted out naked. "My house was here," she said. "It fell into the water. So now my house is here –" she motioned to a small clay hut behind us – "but now we realise this is going to fall in too. The river gets wider day by day."

But even this, Nurjahan said, is not the worst problem. The annual floods have become far more extreme, too. "Until about 10 years ago, the floods came every year and the water would stay for 15 days, and it helped to wet the land. Now the water stays for four months. Four months! It is too long. That doesn't wet the fields, it destroys them. We cannot plan for anything."

When the floods came last year, Nurjahan had no choice but to stay here. She lived with her children waist-deep in the cold brown water – for four months. "It was really hard to cook, or go to the toilet. We all got dysentery. It was miserable." Then she seemed to chastise herself. "But we survived! We are tough, don't you think?"

We sat by the river-bank, our feet dangling down towards the river. I asked if she agrees with Rezwan that her only option soon will be to move on to a boat. He is launching the first models this summer: floating homes with trays of earth where families can grow food. "Yes," she said, "We will be boat-people."

I clambered back on to one of the 42 school-boats in this area. Young children were in the front chanting the alphabet, and teenagers at the back were browsing through the books. I asked a 16-year-old boy called Mohammed Palosh Ali what he was reading about, and he said, "Global warming." I felt a small jolt. He was the first person to spontaneously raise global warming with me. Can you tell me what that is? "The climate is being changed by carbon dioxide," he said. "This is a gas that traps heat. So if there is more of it, then the ice in the north of the world melts and our seas rise here."

I asked if he had seen this warming in his own life. "Of course! The floods in 1998 and 2002 were worse than anything in my grandfather's life. We couldn't get any drinking water, so the dirty water I drank made me very sick. The shit from the toilet pits had risen up and was floating in the water, but we still had to drink it. We put tablets in it but it was still disgusting. What else could we do?"

Mohammed, do you know who is responsible for this global warming? He shakes his head. That answer lies a few pages further into the book. Soon he, and everybody else on this boat, will know it is me – and you.

5. The warming jihad

What happens to a country's mind as it drowns? Professor Philip Jenkins of Pennsylvania State University believes he can glimpse the answer: "The connection between climate change and religious violence is not tenuous," he says. "In fact, there's a historical indicator of how it could unfold: the Little Ice Age."

Between the ninth and 13th centuries, the northern hemisphere went through a natural phase of global warming. The harvests lasted longer – so there were more crops, and more leisure. Universities and the arts began to flower. But then in the late 13th century, the Little Ice Age struck. Crop production fell, and pack ice formed in the oceans, wrecking trade routes. People began to starve.

"In this climate of death and horror, people cast about for scapegoats, even before the Black Death struck," he says. Tolerance withered with the climate shocks: the Church declared witchcraft a heresy; the Jews began to be expelled from Britain. There was, he says, "a very close correlation between the cooling and a region-wide heightening of violent intolerance."

This time, there will be no need for imaginary scapegoats. The people responsible are on every TV screen, revving up their engines. Will jihadism swell with the rising seas? Bangladesh's religion seems to be low-key and local. In the countryside, Muslims – who make up 95 per cent of the nation – still worship Hindu saints and mix in a few Buddhist ideas, too. In the Arab world, people bring up God in almost every sentence. In Bangladesh, nobody does.

But then, as we returned to Dhaka, I was having a casual conversation with Shambrat. He had been driving all night – at his insistence – and by this point he was wired after chewing fistfuls of pan, and singing along at the top of his voice to the Eighties power ballads. I mentioned Osama bin Laden in passing, and he said, "Bin Laden – great man! He fight for Islam!" Then, without looking at me, he went back to singing: "It must have been love, but it's over now...."

I wondered how many Bangladeshis felt this way. The Chandni Chowk Bazaar – one of the city's main markets – was overcast the afternoon I decided to canvass opinions on Bin Laden. I approached a 24-year-old flower-seller called Mohammed Ashid, and as I inhaled the rich sweet scent of roses, he said: "I like him because he is a Muslim and I am a Muslim." Would you like Bin Laden to be in charge of Bangladesh? "Yes, of course," he said. And what would President Bin Laden do? "I have no idea," he shrugged. What would you want him to do? He furrowed his brow. "If Osama came to power he would make women cover up. Women are too free here." But what if women don't want to cover up? "They are Muslims. It's not up to them."

A very smartly dressed man called Shadul Ahmed was strolling down the street to his office, where he is in charge of advertising. "I like him," he said. "Bin Laden works for the Muslims." He conceded 9/11 "was bad because many innocents died," but added: "Osama didn't do it. The Americans did it. They are guilty."

As dozens of people paused from their shopping to talk, a pattern emerged: the men tend to like him, and the women don't. "I hate Bin Laden," one smartly dressed woman said, declining to give her name. "He is a fanatic. Bangladeshis do not like this." As the praise for Bin Laden was offered, I saw a boy go past on a rickshaw, stroking a girl's uncovered hair gently, sensuously. This is not the Arab world.

The only unpleasant moment came when I approached three women selling cigarettes by the side of the road. They were in their early thirties, wearing white hijabs and puffing away. Akli Mouna said, "I like him. He is a faithful Muslim." She said "it would be very nice" if he was president of Bangladesh. Really? Would you be happy if you were forced to wear a burqa, and only rarely allowed out of your house? She jabbed a finger at my chest. "Yes! It would be fine if Osama was president and told us to wear the burqa." But Akli – you aren't wearing a burqa now. "It's good to wear the burqa!" she yelled. Her teeth, I saw, were brown and rotting. "We are only here because we are poor! We should be kept in the house!"

I wanted to track down some Bangladeshi jihadis for myself, so I called the journalist Abu Sufian. He is a news reporter for BanglaVision, one of the main news channels, who made his name penetrating the thickets of the Islamist underground. He told me to meet him at the top of the BanglaVision skyscraper. As the city shrieked below us, he explained: "In the late 1980s, a group of mujahideen [holy warriors] who had been fighting the Soviets in Afghanistan came back to launch an Islamic revolution here in Bangladesh. They tried to mount an armed revolt in the north and kill the former Prime Minister. But it didn't come to much."

Islamic fundamentalism is hobbled in Bangladesh, because it is still associated for most people with Paki-stan – the country Bangladesh fought a bloody war of independence to escape from.

But Sufian says a new generation of Islamists is emerging with no memory of that war. "For example, I met a 21-year-old who had fought in Kashmir, whose father was a rickshaw driver. He said it was his holy duty to establish an Islamic state here through violence. Most were teenagers. All the jihadis I met hated democracy. They said it was the rule of man. According to them, only the rule of God is acceptable."

He said it would be almost impossible to track them down – they are in prison or hiding – but my best bet was to head for the Al-Amin Jami mosque in the north-west of Dhaka. "They are fundamentalist Wahhabis, and very dangerous," he said. Yet when I arrived, just before 6pm prayers, it was a bright building in one of the nicer parts of town. Men in white caps and white robes were streaming in. An ice-cream stall sat outside. I approached a fiftysomething man in flowing robes and designer shoes. He glared at me. I explained I was a journalist, and ask if it would it be possible to look inside the mosque? "No. Under no circumstances. At all."

OK. I asked a few polite questions about Islam, and then asked what he thought of Osama bin Laden. "Osama bin Laden?" he said. Yes. He scowled. "I have never heard of him." Never? "Never." I turned to the man standing, expectantly, next to him. "He has not heard of Osama bin Laden, either," he said. What about September 11 – you know, when the towers in New York fell? "I have never heard of this event, either." Some teenage boys were about to go in, so I approached them. Behind my back, I can sense the Gucci-man making gestures. "Uh... sorry... I don't think anything about Bin Laden," one of them said, awkwardly.

I lingered as prayers took place inside, until a flow of men poured out so thick and fast that they couldn't be instructed not to speak. "Yes, we would like Osama to run Bangladesh, he is a good man," the first person told me. There were nods. "He fights for Islam!" shouted another.

The crowd says this mosque – like most fundamentalist mosques on earth – is funded by Saudi Arabia, with the money you and I pay at the petrol pump. As I looked up at its green minaret jutting into the sky, it occurs to me that our oil purchases are simultaneously drowning Bangladesh, and paying for the victims to be fundamentalised.

After half-an-hour of watching this conversation and fuming, the initially recalcitrant man strode forward. "Why do you want to know about Bin Laden? We are Muslims. You are Christian. We all believe in the same God!" he announced.

Actually, I said, I am not a Christian. There was a hushed pause. "You are... a Jew?" he said. The crowd looked horrified; but then the man forced a rictus smile and announced: "We all believe in one God! We are all children of Abraham! We are cousins!" No, I said. I am an atheist. Everyone looked genuinely puzzled; they do not have a bromide for this occasion. "Well... then..." he paused, scrambling for a statement... "You must convert to Islam! Read the Koran! It is beautiful!" Ah – so can I come into the mosque after all? "No. Never."

6. The obituarist?

In a small café in Dhaka, a cool breeze was blowing in through the window along with the endless traffic-screams. The 32-year-old novelist Tahmima Anam was inhaling the aroma of coffee and close to despair.

She made her name by writing a tender novel – A Golden Age – about the birth of her country, Bangladesh. When the British finally withdrew from this subcontinent in 1948, the land they left behind was partitioned. Two chunks were carved out of India and declared to be a Muslim republic – East Pakistan and West Pakistan. But apart from their religion, they had very little in common. The gentle people of East Pakistan chafed under the dictatorial fundamentalism imposed from distant Islamabad. When they were ordered to start speaking Urdu, it was enough. Her novel tells how in 1971, they decided to declare independence and become Bangladesh. The Pakistanis fought back with staggering violence, but in the end Bangladesh was freed.

Now Anam is realising that unless we change, fast, this fight will have been for the freedom of a drowning land – and her next novel may have to be its obituary.

Anam came to Bangladesh late. Her Dhaka-born parents travelled the world, so she grew up in a slew of international schools, but she always dreamed of coming home. Her passion for this land, this place, this delta, aches through her work. About one of her characters, she wrote: "He had a love for all things Bengali: the swimming mud of the delta; the translucent, bony river fish; the shocking green palette of the paddy and the open, aching blue of the sky over flat land."

"You can see what has started to happen," she says. The vision of the country drowning is becoming more real every day. Where could all these 150 million people go? India is already building a border fence to keep them out; I can't imagine the country's other neighbour – Burma – will offer much refuge. "We are the first to be affected, not the last," Anam says. "Everyone should take a good look at Bangladesh. This story will become your story. We are your future."

It is, she says, our responsibility to stop this slow-mo drowning – and there is still time to save most of the country. "What could any Bangladeshi government do? We have virtually no carbon emissions to cut." They currently stand at 0.3 per cent of the world's – less than the island of Manhattan. "It's up to you."

Anam is defiantly optimistic that this change can happen if enough of us work for it – but, like every scientist I spoke to, she knows that dealing with it simply by adaptation by Bangladeshis is impossible. The country has a military-approved dictatorship incapable of taking long-term decisions, and Dutch-style dams won't work anyway. "Any large-scale construction is very hard in this country, because it's all made of shifting silt. There's nothing to build on."

So if we carry on as we are, Bangladesh will enter its endgame. "All the people who strain at this country's seams will drown with it," Anam says, "or be blown away to distant shores – casualties and refugees by the millions." The headstone would read, Bangladesh, 1971-2071: born in blood, died in water.