Kitabı oku: «High Tide: How Climate Crisis is Engulfing Our Planet», sayfa 2

THE ‘SMOKING GUN’?

As it happens, such evidence is indeed available for the UK. To find out more, I went to visit the climatologist Dr Tim Osborn at the Climatic Research Unit (CRU), part of the University of East Anglia. It was almost two years to the day after the start of the autumn 2000 disaster, and there was a hint of winter in the air as the London train sped through the Essex town of Colchester, past the River Stour saltmarshes and on through the flat Norfolk fenlands to Norwich.

As so often, Osborn confounded my expectations. No white lab coat for him: instead, a youngish, fair-haired man in shorts, trainers and a red golfing T-shirt was leaning over the balcony three floors above as I arrived at the round, glass-fronted CRU building.

‘Hello! Come on up,’ he shouted as I climbed the stairs. His room was strewn with back copies of the International Journal of Climatology and meteorology books, as well as sheafs of paper – many covered with impenetrable algebraic scribbles.

‘Sorry about the mess,’ he said as I sat down on a free chair. Then he swivelled his own chair round to face the computer screen. ‘Now, have a look at this.’

Osborn has spent years analysing nearly half a century of rainfall statistics. From a damp day in 1960s Blackpool to a torrential summer downpour in 1990s Devon, all these records were fed into his number-crunching computer. When spat out the other end into a series of graphs, these statistics – rather than just showing the usual random vagaries of the British weather – showed that something very unusual was going on. In fact the trend was so clear that even Osborn himself was ‘surprised’ by what it revealed.

What Osborn discovered was that over recent decades heavy winter downpours have indeed increased dramatically. ‘Over the period from the 1960s to the mid-1990s there was a doubling of the amount of rain that came in the “heavy category” in winter,’ he explained. ‘So in the 1960s something like seven or eight per cent of each winter’s rainfall came from what we call the “heavy” events, whilst by the mid-1990s that had increased to about fifteen per cent.’⁶

With more rain falling in a short time, river systems were unable to cope – and floods were the inevitable result. What’s more, this heavier winter rainfall was directly related to rising atmospheric temperatures.

Straightforward atmospheric physics suggests this could be the global warming ‘smoking gun’. The relationship between temperature and the air’s capacity to hold water vapour is not linear – in fact the air can hold proportionally more water as temperature rises.⁷ So in a given ‘precipitation event’, whether it is snow, hail or rain, more water is available to fall out of the sky over the same short period of time.

This is exactly what seems to be happening in Britain: as a result of global warming, more warm, saturated air rushes in from the Atlantic, causing stronger storms and heavier rainfall. As a result, the probability of heavy rainfall has doubled over the last thirty-five to forty years in southeast England, according to observations and analysis conducted by Osborn and his CRU colleague Mike Hulme.⁸

These aren’t one-off downpours, either. The frequency of prolonged five-day heavy rainfall events has also been increasing. In Scotland floods have been getting far more frequent over the last few decades, whilst in England and Wales there have been four major floods in the last twelve winters: 1989/90, 1993/94, 1994/95 and, of course, 2000/01.⁹ The match for 2000 isn’t perfect because the worst flooding came during the autumn – but the floods also lasted right through until January, just as the trend would suggest.

Osborn’s work also coincides with evidence from other parts of the world. Study after study has come to the same conclusion: that throughout Earth’s mid-latitudes, rainfall is getting heavier and more destructive. There has been a steadily increasing rainfall trend in the United States through the twentieth century, and much of that increase has come in the heaviest downpours. A number of catastrophic floods in recent years – most notably the Mississippi floods of 1993, the New England floods of 1997 and the winter floods of 1997 in the Pacific northwest and California – seem to show the shape of things to come.¹⁰

Scientists have reached a similar conclusion in Europe,¹¹ whilst in Australia rainfall totals are also rising steadily.¹² This might seem to be a good thing in a continent often afflicted by drought – but again, much of the increase has come in the heaviest deluges, which are less likely to soak productively into farmland, and more likely to run quickly off the land in destructive torrents, taking the fertile topsoil with them.

One study looking specifically at large river basins – such as the Yangtze in China and the Danube in Europe – confirms what many people have long suspected: that big floods are indeed getting more frequent. In fact, sixteen of twenty-one ‘great floods’ during the twentieth century have occurred since 1953, and in the planetary mid-latitudes seven out of eight have also occurred in the second half of the century.¹³ UK-based researchers have also identified a near-global trend towards heavier rain and floods.¹⁴

In the most comprehensive survey of all, the Intergovernmental Panel on Climate Change (IPCC) confirmed that rainfall was getting heavier and more extreme in the United States, Canada, Switzerland, Japan, the UK, Norway, South Africa, northeast Brazil and the former USSR.¹⁵

This hasn’t affected everywhere: some places have got drier, such as the Sahel in Africa and northern China. But almost the whole of the Earth’s mid-latitudes has been affected, and as Osborn told me, ‘if there’s something coherent going on at all the mid-latitudes, then there must be something virtually global scale driving it’. Computer models of global warming have long illustrated this effect, and now it seems to be showing up in the real world, just as many scientists – including Osborn himself – have long predicted.

MONMOUTH, FEBRUARY 2002

Just under 10,000 homes were flooded in Britain during the 2000 event. Some were hit two or three times, and a few left completely uninhabitable. Transport and power services were disrupted, and the cost of flood-related damage eventually totalled around £1 billion, according to the government’s Environment Agency.¹⁶ Everybody breathed a sigh of relief when it was finally over, but only one year and three months later – in the first week of February 2002 – the floods were back.

This time one of the worst-hit places was Monmouth, a historic town just over the Welsh border at the confluence of the rivers Monnow and Wye. On 4 February ‘severe flood warnings’ were issued for both rivers, schools were closed and residents in low-lying areas began to move themselves upstairs. Twenty families were evacuated from mobile homes when the Wye burst its banks, and three streets were completely submerged.

Judging from the news Monmouth sounded well worth a visit. This meant hiring a car, but I was ready to leave by mid-morning, heading towards Cheltenham on the old A40. The River Thames was pretty high, and when the road crossed some small rivers on the way over the Cotswold hills, I could see that each was swollen, its banks only identifiable by lines of willow trees standing in the brown water.

Just outside Gloucester was the first sign of large-scale flooding – a huge new lake stretched almost as far as the eye could see. Trees, telegraph poles and even an electricity substation were surrounded by water, and a couple of swans paddled by.

I drove on. The sky was darkening again with ominous clouds as I neared Wales, and soon a heavy shower sent torrents of new water coursing down off the hillsides.

About ten miles outside Monmouth I spotted a ‘Road Closed’ sign and drove round it to investigate. I was deep in the Forest of Dean, and the small road led down a steep wooded valley towards the River Wye. On the river itself was a small village, little more than a hamlet, called Lower Lydbrook.

Lower Lydbrook looked like it had been doused entirely in mud. Mud was everywhere: across the road, the pavements, people’s drives and lawns. The whole area had clearly been awash with very dirty floodwater only a few hours beforehand. Outside the Courtfield Arms a man was sweeping the sticky brown mess off the car park. I slithered up to him and asked whether he felt the flooding was getting worse.

His answer was surprising. In the past the floods had come once every three or four years. Now it was two or three times in a single year. And the latest inundation was easily the worst for three decades.

On the other side of the road was a restaurant called the Garden Café. All the gravel in its neat drive was coated with the same brown layer, as was a car parked outside. I followed some fresh footprints round to a side door. It was swinging open, and I peered into the gloom inside. Not surprisingly the place was a mess: fridges were stacked up on tables and wet rugs were hanging from the beams. There was a pervasive damp musty smell, and a clear high-water line about a metre up the walls.

The owner was happy to take a break from cleaning up, and introduced himself. ‘Paul Hayes. Owner and chef of the Garden Café.’ He looked around at the disastrous mess and added: ‘Currently on holiday.’

Hayes was certain that the flooding had got worse in recent years. It wasn’t necessarily that more rain fell overall – but rather than being averaged out over a month, the whole lot simply fell in one night.

‘We don’t have a winter any more, we have a wet season. It’s like tropical rainstorms here. And because it’s a hilly area this translates into flash floods. The river rose six metres from its level last week. It came in here at four on Sunday morning, and within another two hours reached a metre up the wall. It never used to flood in the house, but that’s three years in a row we’ve been flooded now.’

As a result, his business was wrecked. All the fridges were ruined, he was losing customers every day the restaurant remained closed, and all his stock would have to be thrown away. Nor was this the first time: during the winter of 2000 – when the building had been flooded on three separate occasions in October, December and January – he had only managed to open for twelve days throughout the whole four-month period. And with the whole property now virtually uninsurable, no buyer would even look at it.

Hayes had a knowing, worldly manner, but I could tell that even he had been thrown by the latest deluge. ‘It came so suddenly,’ he said, almost perplexed. ‘I knew it was going to flood, even though there was no flood warning. And if it rains in the next week it’ll flood again – all that water’s got nowhere to go.’

In Monmouth itself the floodwaters had only just begun to recede. Most of the town was unaffected – the Romans had sensibly founded it on a hill, but developments in more recent centuries have extended the town right along the river. Built at the confluence of two rivers, and not far from the tidal estuary, the area has always been prone to flooding – the one reliable crossing point has been called Dry Bridge Street since Norman times.

When I arrived, though, Dry Bridge Street was half underwater.

Children were splashing around and riding their bikes through it, whilst dog-walkers in wellington boots waded through to a nearby park. Sandbags were stacked in front of every front door. Opposite the bridge itself, the Green Dragon pub had narrowly missed inundation just hours earlier. A hundred yards away, the Britannia Inn had not been so lucky, and water was still being pumped out of it into the road.

I knocked on the door and it was opened by a young woman with short brown hair.

‘We’re closed because of the floods,’ she began, looking at me as if I were stupid. But when I explained what I wanted, she invited me inside.

Several regulars were sitting on benches reading newspapers in the gloomy half-light. A couple of others were helping sweep mud off the stone floor. Everyone agreed that the flooding was getting worse.

‘This place is rotting,’ complained the landlady. ‘There is constant damp from the rain and sewage.’ She poked disapprovingly at some blistered paint on the lower walls. ‘It just keeps getting flooded. In the past it didn’t seem as often – now it’s twice a year. It’s just constantly, all the time. It’s hard enough to make a living in this trade as it is, without all this happening.’

‘Thirty years ago you knew what the seasons were,’ one of the regulars added, leaning on his broom. ‘Now you don’t know. It’s got to be to do with the way the weather changes – the rainfall is unbelievable.’

I drove out of Monmouth and into Wales, the first mountains rising up in the distance. It was raining again, and just before Crickhowell flood warnings appeared by the side of the road. A small house next to a layby was completely surrounded, the water so deep in places that only the tops of the roadsigns stood out. I reached Machynlleth and my old friend Helena’s house, on the west coast of Wales, long after dark, and lay awake listening to the rain hammering on the roof long into the night.

Machynlleth has a small museum-cum-art gallery called the Tabernacle, a compact slate-roofed building not far from the railway station. I headed down there in the morning with Helena. Not being a huge fan of the abstract oil paintings on the wall, I tried instead to engage the white-haired old lady behind the front desk in conversation. It’s always easy, whether you’re in England, Scotland or Wales, to strike up a conversation about the weather.

‘Terrible weather, isn’t it?’ I ventured. The old lady carried on arranging some leaflets on the desk. I noticed her hearing aid, and tried again, more loudly.

‘TERRIBLE WEATHER, ISN’T IT?’

‘Oh yes,’ she answered, ‘such a lot of rain.’

I nodded encouragingly, and she went on. ‘The last few years we’ve had more rain than I ever remember.’ She paused. ‘And no snow either. The last proper snow,’ (and she emphasised the word ‘proper’ to show that she meant snowploughs, the town cut off and so on) ‘was over twenty years ago. The snow we’ve had in the last few years has been hardly anything. Instead, it’s been rain, rain, rain.’

On sale next to the desk were several Christmas cards, each showing children making a snowman under a heavy winter sky, the pretty white flakes swirling around them as they gathered up the snow in their duffle coats and woolly mittens. It was the traditional British winter, everyone’s dream of a white Christmas. And what no one knows – or likes to admit – is that it’s probably gone for good.

SNOW PLACE TO GO

Snow was becoming a rarity even during my childhood. Apart from the years in Peru, I grew up in a small Nottinghamshire village called Colston Bassett – a tiny place with little more than a pub, a primary school, and a local dairy famous for its pungent stilton cheese. Every autumn the village held a harvest festival, when all the local farmers would bring their produce into the village hall for a lavish evening meal. I looked forward to it for two reasons: because I and the other village kids were allowed to get drunk on cider; and because it meant the onset of winter.

I loved winter. From the first frosts in October to the bursting of the buds in April I’d scan the skyline almost hourly for snow. It came, too: we even got snow on Easter Sunday one year. In January 1987 it fell so heavily overnight that the drifts piled up against the side of the house and meant a day off school. The school bus got through after a couple of days, but the snow lasted for almost a fortnight. Every winter there’d always be a few centimetres of snow which would generally last for two or three days. I was filled with barely-suppressed excitement each time the first flakes fluttered past the school windows.

I haven’t seen snow like this for over seven years in Oxford, which isn’t too far from where I grew up. Back in 1996 there were a few days of snow (no big deal, less than ten centimetres deep. I remember it principally because I fell off my bicycle on the ice) but since then nothing. In fact snow has become so rare that when it does fall – often just for a few hours – everything grinds to a halt. In early 2003 a ‘mighty’ five-centimetre snowfall in southeast England caused such severe traffic jams that many motorists had to stay in their cars overnight. Today’s kids are missing out: I haven’t seen a snowball fight in years, and I can’t even remember the last time I saw a snowman.

A quick glance at the official weather records for Oxford confirms my rather hazy impressions. The last decent snow was in 1985, when there were twenty-one days of snow cover. The winter of 1963 was the most extreme in England since 1740, and during the 1970s snow days averaged about eight days per season. How things have changed. Six out of the last ten years have been completely snowless, whereas between 1960 and 1990 there were only two snowless winters during the whole three decades.¹⁷

By the 2080s our grandchildren will only experience snow on the highest mountaintops in Scotland, because over most of the English lowlands and the south coast snowfall will be virtually unknown.¹⁸

Other familiar things may also look very different. Take the average British garden. Lawns will need mowing all year round, and will die in summer droughts unless heavily watered. Traditional herbaceous border species like aster, delphiniums and lupins will also struggle in the dry soils. Tree-ferns, palms, bamboos and bananas will replace holly, oak and ash. Many fruiting trees and bushes need winter chilling for bud formation, so blackcurrants and apples will need to be replaced with peaches and grapes. Overwintering bulbs need low temperatures to stimulate their development, so gardeners will need to dig up the bulbs and refrigerate them for a few days in order to coax spring flowers out of them. New pests and diseases will spread out of the greenhouse and into the open garden. Aphids, for example, begin their infestations two weeks earlier for every 1°C rise in temperature.¹⁹

Many of these changes are already underway, but have been accelerating over the last two decades. Termites have already moved into southern England. Garden centres are beginning to stock exotic sub-tropical species, which only a few years ago would have been killed off by winter.²⁰ In Surrey, horse chestnut trees now come into leaf twelve days earlier than they did in the 1980s. Oak is coming out ten days earlier, and ash six days earlier. Winter aconites are now flowering a month earlier than three decades ago, and crocuses – which used to flower in March – are now putting out petals in mid-January.²¹ The average UK growing season is now longer than at any time since records began in 1772. In 2000 there was hardly any cold weather at all: the growing season extended from 29 January to 21 December, leaving just thirty-nine days of winter.²²

In the summer of 2003 temperatures broke through the crucial 100°F level for the first time in recorded history, peaking at 100.6°F (38.1°C) on 10 August at Gravesend in Kent. Continental Europe, meanwhile, suffered its highest temperatures for 500 years, sparking catastrophic forest fires in France, Spain and Portugal, and killing thousands of elderly people in the sweltering cities. In France alone almost 15,000 people died in the heatwave, sparking a national crisis of guilt and soul-searching as the bodies piled up. Even in the cooler UK, 2000 people died.

Heatwaves catch the headlines, but the insidious effect of higher average temperatures is having a permanent effect on our surroundings. Indeed, the temperature rise is now so rapid that in climatic terms English gardens are moving south by twenty metres each day.²³ (This is because, with every 1°C rise in temperature, climatic zones move 150 kilometres north.) English temperatures are predicted to soar by up to 5°C this century alone,²⁴ so by the 2080s our gardens will – metaphorically speaking – be nearing the south of France.

This is particularly bad news for ‘heritage gardens’. The National Trust will be faced with the choice of uprooting everything from its much-loved English country gardens and trucking them to the north of Scotland, or giving up and letting the traditional species die.

In fact the British countryside our grandchildren grow up in is likely to be a very different place to the one we see today. According to the Woodland Trust, increased drought and water stress from hotter, dryer summers means that parts of London, East Anglia and the Midlands might become unsuitable for beech trees in the near future. Although beech woods on chalk soils should fare better (plant roots seem to be able to draw water large distances up through porous chalk rock), die-back has already begun in parts of East Anglia and Southern England. ‘In the worst-case scenarios, beech could soon be absent from large areas of the south,’ the Trust concludes.²⁵

Oaks are also going to be on the endangered list. Although more likely to withstand summer droughts and winter floods, oak trees are threatened by a new disease called oak wilt – which has already devastated woodland in North America.²⁶ Oak wilt thrives in warmer winters: it could turn into a plague of similar proportions to Dutch Elm Disease, which virtually wiped out elms in the UK, once a common wood and hedgerow tree species. Because of Dutch Elm Disease, I have never seen a fully-grown elm tree: and when I was growing up every field boundary was lined with their enormous skeletal carcasses. Could oaks go the same way?

Instead of these familiar trees, woodlands are likely to be predominantly composed of sycamore, with other invasive species like rhododendron and Japanese knotweed making up the undergrowth. The animals which currently fit into our woodland ecosystems will also disappear – woodpeckers, butterflies, frogs and toads – all will need to move to cooler climes or die.²⁷

In theory woodland species could ‘migrate’ further into the north and west of the British Isles to keep pace with the shifting climatic zones. Many butterflies and birds are already doing this: the speckled wood butterfly has moved north by over a hundred kilometres in the last sixty years – and it’s still lagging behind current rates of climate change.²⁸ The nuthatch, a colourful tree-dwelling bird, is now extending its range, and the reed warbler has begun for the first time to breed regularly in Scotland and Ireland.²⁹

But whilst birds and butterflies are clearly fairly mobile, most tree species are not. At the end of the last Ice Age trees could colonise new areas at a speed of up to a kilometre a year, by spreading their seeds and gradually establishing new saplings. But projected warming rates will far outstrip this: climatic zones in the twenty-first century will be shifting north seven times faster than most plant species can follow them.³⁰

There are also some serious practical reasons why natural ecosystems can’t simply move with a shifting climate, such as cities, enormous dead zones of intensive farmland and major roads. The great crested newt, for example, couldn’t move north even if it wanted to – it can’t cross the M4 motorway.³¹ Nor are my local beechwoods likely to be able to get round Birmingham and Manchester in their supposed long trek north.

Extinction is a certainty for highly-specialised plants and animals which already live in very restricted areas. Norwegian mugwort, a plant which lives only in the Arctic cold of the highest Scottish mountain summits, simply has nowhere higher to go. Nor has the capercaillie, the emblematic Scottish bird which lives in pinewoods and is similarly dependent on low temperatures for its survival. Also on the way out is the natterjack toad – which according to a government study is due to lose its ‘climate space’ as early as 2020, when the seasonal ponds it breeds in dry out. The mountain ringlet butterfly will lose its climate space by 2050, and it too is slated for extinction.³²

As with the National Trust’s gardens, climate change will ruin British nature conservation strategies, which are currently based around a patchwork of Sites of Special Scientific Interest and nature reserves. Almost all of these are adapted to specialised habitat – such as upland peatbogs, chalk grasslands or lowland heaths – which depend on particular rocks, soil and topography and therefore, by definition, cannot be moved.

Ecosystems are incredibly complex, with many different species occupying their own niche in the food web. Once these begin to fracture, specialised species will die out in all but the most tiny remnant habitats, to be replaced by only a few highly-adaptable weeds. Biodiversity will decline as these adaptable species, many of them invasive introductions from other parts of the world, take over ever-larger areas of our outdoors.

The British countryside of 2080 is likely to be an eerie, unnerving place, with the same familiar rolling landscape supporting only a few very mobile – but strangely unfamiliar – plants and animals.

Like the Christmas snow, the holly and the ivy may soon be distant memories.

Yet none of this has to happen, or at least not to the extent I’ve outlined above. Some amount of warming is already inevitable, but whether it reaches the extremes described above depends on all of us – and the decisions we take about how to run our lives and our economy. It depends crucially on one thing, and one thing only: how much greenhouse gas we release into the atmosphere over the decades ahead.

On the way back from Wales, I got caught in a traffic jam on the M6 just outside Birmingham. This one was a monster. Three lanes of cars, vans and lorries were packed solid. The whole place stank of petrol and diesel fumes, aggravated by a few irritated motorists who revved their engines pointlessly. A few drivers even got out and stood next to their vehicles, glaring at everyone else, looking for someone to blame. No one spoke. There was none of the camaraderie you often get on a broken-down bus or a delayed train. This was an atomising, frustrating experience. We were all trapped like prisoners in our little metal boxes, and every one of us hated it.

Despite jams and congestion, road traffic in Britain is rising inexorably. Every year Britons spend more time and travel greater distances in their cars. An increasing number of short journeys – under two miles in length, which could easily be done on foot or by bicycle – are now done in cars. Road-traffic levels rose by a fifth between 1988 and 1998, and are predicted to rise by nearly another two-thirds by 2031. Journeys by bicycle, meanwhile, are at an all-time low.³³

In many ways car use is a self-reinforcing process. When I was young most children used to walk to school or go by bus. Now – partly because of parental fears about busy roads – the ‘school run’ has become one of the biggest causes of urban congestion. It causes gridlock every morning around eight on many of the roads near where I live. It’s a vicious circle: the more parents who take their kids to school by car, the more cars on the road and the more dangerous the roads become for everyone else, forcing still more parents to resort to their cars. And so it goes on.

Similarly, the growth of out-of-town shopping has encouraged car use, putting town centre shops out of business and reducing the places one can shop without going in the car still further. By building new roads and supporting the growth of supermarkets the government has made matters worse – but we’ve all been complicit in these destructive trends.

And most people with cars can scarcely envisage living any other way. When the RAC recently asked motorists if they agreed with the statement: ‘I would find it very difficult to adjust my lifestyle to being without a car’, 89% said that they did.³⁴

Nor can those of us who have given up our cars – but still, like me, regularly travel by jet aircraft – afford to be smug. A single short-haul flight produces as much carbon dioxide as the average motorist gets through in a year. The flights I undertook to research this book directly produced over fifteen tonnes of carbon dioxide³⁵ – which is equivalent to about forty-five tonnes once the overall warming effect of aviation pollution is taken into account.³⁶ Many people who work for environmental organisations travel enormous distances by plane every year – each with similarly valid reasons for doing so as I felt I had. Speaking personally, the impact of these flights is so enormous that it wipes out all the other aspects of my relatively green lifestyle (no car, green electricity, local food and so on) and is equivalent to my total sustainable personal carbon budget for about twenty years.³⁷ Oh dear.

Although cars are a highly visible pollution source, and transport accounts for a third of the average person’s greenhouse gas emissions, another third comes from the home – over 50% of this from space heating.³⁸ With some insulation, a new boiler and some double glazing, heating costs and the associated emissions could be reduced dramatically – yet most of us don’t bother, or simply can’t afford to do so. Over a tenth of British houses have no insulation at all,³⁹ and 20,000 to 40,000 people – mainly the old and vulnerable – die every year because of cold-related killers like hypothermia and pneumonia.⁴⁰ As well as reducing climate change, better housing and insulation would save lives.