Why a salmon, a horse chestnut and a little old lady in Surrey are the difference between... ...a bank holiday weekend like this, or like that

For the past 50 years or so Jean, a spinster in her seventies who lives in Surrey, has documented a few simple facts about the countryside around her. In particular, she records the dates when four species of tree - oak, ash, horse-chestnut and lime - come into leaf. It's the sort of trivial task that machines aren't much good at, but which humans enjoy. She started doing it as part of a diary. Then she kept on doing it. For decades.

Now, Jean's data is precious, because scientists need it. Her full name and location are closely protected secrets at the Institute of Terrestrial Ecology (ITE), known only to a few scientists who are working on one of its simplest yet most important projects: collating the data to see whether global warming has started to affect British life.

Jean is not alone: the ITE co-ordinates a network of about 500 unpaid volunteers around the country who monitor nature and see how it is changing. Mavis Jones, for example, is a pensioner living in Hillingdon; for the past 10 years she has noted the arrival dates of migratory birds such as swallows and the hatching dates for blackbirds. Has it changed? "It's earlier than it used to be," she says. "Sometimes by days, sometimes weeks." She doesn't have much doubt about the reason. "Oh, it's this so-called global warming."

The results of the work will be announced next month by the Department of the Environment. And though the scientists collating the data are sworn to secrecy, there is little doubt that the 35 disparate pieces of information being monitored - on such topics as tree leafing dates, the arrival dates of swallows in spring, the number of days when skiing is possible in Scotland, and the number of cases of Lyme disease (caused by a tick that flourishes in warm weather) - will indicate that yes, Britain's climate is changing. Spring is happening earlier, birds are taking different migratory routes, "extreme" events such as floods are happening more frequently, average air temperatures are higher, underground chalk reservoirs are drier, and more of the coastline is collapsing into the sea.

To a scientist, the suggestion that the climate is changing presages trouble: more severe weather, such as hurricanes and tornadoes, higher sea levels, changes in biodiversity. But the problem that researchers and policy-makers face is: how do you persuade the man sitting in the car behind the Clapham omnibus that global warming is happening, and that he is contributing to it by driving rather than walking? And how do you persuade him to change his behaviour as a result?

"The only way you'd get people to notice global warming is if it raised the price of beer," comments Tim Sparks, one of the team at the ITE who has been analysing the data for next month's report.

In fact, we are already seeing the price of another liquid - vehicle fuel - rising faster than inflation, through the Government's "fuel duty escalator", whose purpose is claimed to be to encourage people to use less fuel. That has led to the lorry drivers' protests. But the row there is not over whether lorries contribute to the greenhouse effect. The drivers are just angry at the price. The Government certainly hasn't used carbon dioxide emissions as a justification for the duty hike.

Similarly, earlier this month the Government launched a witty ad campaign encouraging us to "do our bit" by recycling rubbish and bottles, sharing car journeys, taking showers not baths, walking instead of driving. Famous names such as George Best, Chris Evans and Ian McCaskill appear in the ads, yet phrases like "global warming" certainly don't. "Clean air", perhaps. "Recycle", certainly. But not the planet. The activists' phrase of a few years ago was "Think global, act local". The Government seems to prefer leaving the first bit out.

Yet there are a few groups of men and women (though perhaps not in the street) who have an inkling that global warming could affect them, and not positively.

The number of "spring salmon" - the large fish that return to spawn after spending more than a year in the sea - has falling by almost 40 per cent in the past five years. As a result, the Environment Agency (which issues salmon fishing licences) has banned the retention of salmon caught in the first five months of the year.

The agency blames changes in ocean currents and temperatures, which in turn affects the spawning and survival rates of the young fish. But, as one of the fisheries officers notes, "There's not much we can do about ocean currents." So it is the would-be fishermen and women who lose out.

Far from the riverbank, even mountaineers have discovered that global warming takes its toll. Last weekend, a husband and wife were descending from the summit of Mt Hood in Oregon, on the west coast of the US. The mountain is only one-third as high as Everest, but Oregon was experiencing temperatures which leapt above 30C for the first time this year. As the pair walked down, they slipped in mushy snow and fell more than 1,000ft to their deaths. In the Alps, summer climbers often note that ice and snow become mushy, and hence dangerous, earlier in the day. It is a subtle change - perhaps only a difference of a quarter of an hour - but one that old hands might note.

The trouble with evidence like that, from a scientist's viewpoint, is that it is anecdotal and short-term. "You need a long series of data to detect climate change," says Dr Sparks. "The man in the street doesn't care about statistical significance, but the scientific community needs that to be convinced." Hence the network of 500 or so "phenologists" (people who measure change) watching nature and passing the information back to the study for the Government. Data like Jean's - which covers a long time series - is especially valuable.

Another network member, Ann King, lives in Norfolk: for the past 10 years or so she has had a rivalry with her father, trying to be the first to hear a cuckoo or spot a swallow. She joined the study network because "I thought it would be interesting - you know, formalise my competition with my father".

Now she in turn hopes to recruit her former employer, a man with a large garden who has fastidiously kept daily rainfall records for the past 20 years. People like him are immensely valuable - especially when formal organisations are cutting back; the Nature Conservancy Council, for example, has reduced its monitoring of butterflies, a subtle indicator of environmental health, owing to funding cuts. People like Mrs King may have to fill the gap.

Even so, as people contemplate a spring that arrives about a week earlier than 20 or 30 years ago, and generally warmer bank holidays, the tendency is to think that there isn't really a downside to global warming; that a global rise in temperature of a few tenths of a degree won't make any difference to our daily lives.

And, indeed, how would you notice the effects of global warming in daily life? What, if anything, would be bad about them? Asked this, many scientists who are happy to talk about ice shelves in Antarctica and gas circulation in the upper atmosphere become stymied.

"There could be increased frequency of precipitation," says Dr John Mitchell, head of climate change modelling at the Meteorological Office's Hadley Centre in Bracknell, Berkshire.

You mean, it would rain more often? "Well, yes." For Dr Mitchell, who has been developing computer models of the entire globe, it is hard to see global warming on an individual's scale.

"In 50 years we could see a warming of 1.5C across the UK," he explains. "Some people think that's just like moving further south, but that's not accurate because the warmth there is due to the position of the sun in the sky, not the general air temperature. From day to day you wouldn't really notice it, because the weather generally is so variable."

Instead, Dr Mitchell deals in probabilities, chances, likelihoods. "A temperature rise like that would reduce the chance of frost by about 50 per cent. Gardeners wouldn't have much to worry about. But there would be 25 per cent more days when the temperature was over 25C." (That is, of course, at the Met Office, rather than John O'Groats.) It would be nice (and certainly convenient) if this were certain, but it isn't. People such as Jean, Mrs Jones and Mrs King can already see the subtle effects: the earlier leafing of trees, different birds, fewer ladybirds.

But as climate change becomes established, some changes could be dramatic. It's possible, for example, that malaria could become endemic in the south east of England. Alternatively, the whole of Britain could turn as cold and icy as Newfoundland on the Canadian coast. The two locations lie on the same latitude; our climate is warmer because of the Gulf Stream in the Atlantic. But some computer models suggest that as the seas warm, the complex system of currents that brings warm water up from the Equator could switch off, plunging us into freezing winters and miserable summers. The trouble is that we don't know for sure, and we don't know when we will know for sure.

But what else might there be? More cases of heat stroke? "With higher sea levels, you would expect more coastal erosion and more frequent severe flooding. But we won't notice it happening quickly. Global warming is one of those things that's subtle but, in the long term, could have massive consequences," says Dr Mitchell.

This is the essential problem with trying to persuade the public about global warming. It is what scientists call the "frog in a saucepan" phenomenon. Drop a frog into hot water, and it will jump out. Drop it into lukewarm water which you then heat, and it will stay, oblivious to changes that are killing it. In this scenario, we are the frogs, blissfully lounging in the ever-heating tub. The question is: what will it really take to make us jump?

Arts and Entertainment
Call The Midwife: Miranda Hart as Chummy

tv Review: Miranda Hart and co deliver the festive goods

Arts and Entertainment
The cast of Downton Abbey in the 2014 Christmas special

tvReview: Older generation get hot under the collar this Christmas

Arts and Entertainment
Dapper Laughs found success through the video app Vine

comedy Erm...he seems to be back

Arts and Entertainment
Wolf (Nathan McMullen), Ian (Dan Starky), The Doctor (Peter Capaldi), Clara (Jenna Coleman), Santa Claus (Nick Frost) in the Doctor Who Christmas Special (BBC/Photographer: David Venni)

tvReview: No ho-ho-hos with Nick Frost's badass Santa

Arts and Entertainment
Bruce Forsyth and Tess Daly flanking 'Strictly' winners Flavia Cacace and Louis Smith

tv Gymnast Louis Smith triumphed in the Christmas special

PROMOTED VIDEO
Arts and Entertainment
Rhys says: 'I'm not playing it for laughs, but I have learnt that if you fall over on stage, people can enjoy that as much as an amazing guitar solo'
musicGruff Rhys on his rock odyssey, and the trouble with independence
Arts and Entertainment
Krysia and Daniel (Hand out press photograph provided by Sally Richardson)
How do today's composers answer the challenge of the classical giant?
Have you tried new the Independent Digital Edition apps?
Arts and Entertainment

ebooksNow available in paperback
Arts and Entertainment

ebooks
News
Shenaz Treasurywala
film
News
tv
Arts and Entertainment
Jason Watkins as Christopher Jefferies
tv
Arts and Entertainment
Star Wars Director JJ Abrams: key character's names have been revealed
film
Arts and Entertainment
Pharrell Williams won two BBC Music Awards for Best Song and International Artist
music
Arts and Entertainment
Mark, Katie and Sanjay in The Apprentice boardroom
TV
Arts and Entertainment

Film The critics but sneer but these unfashionable festive films are our favourites

Arts and Entertainment
Frances O'Connor and James Nesbitt in 'The Missing'

TV We're so close to knowing what happened to Oliver Hughes, but a last-minute bluff crushes expectations

Arts and Entertainment
Joey Essex will be hitting the slopes for series two of The Jump

TV

Who is taking the plunge?
Arts and Entertainment
Katy Perry as an Ancient Egyptian princess in her latest music video for 'Dark Horse'

music
Arts and Entertainment
Dame Judi Dench, as M in Skyfall

film
Arts and Entertainment
Morrissey, 1988

TV
Latest stories from i100
Have you tried new the Independent Digital Edition apps?

ES Rentals

    Independent Dating
    and  

    By clicking 'Search' you
    are agreeing to our
    Terms of Use.

    A Christmas without hope: Fears grow in Gaza that the conflict with Israel will soon reignite

    Christmas without hope

    Gaza fears grow that conflict with Israel will soon reignite
    After 150 years, you can finally visit the grisliest museum in the country

    The 'Black Museum'

    After 150 years, you can finally visit Britain's grisliest museum
    No ho-ho-hos with Nick Frost's badass Santa

    No ho-ho-hos with Nick Frost's badass Santa

    Doctor Who Christmas Special TV review
    Chilly Christmas: Swimmers take festive dip for charity

    Chilly Christmas

    Swimmers dive into freezing British waters for charity
    Veterans' hostel 'overwhelmed by kindness' for festive dinner

    Homeless Veterans appeal

    In 2010, Sgt Gary Jamieson stepped on an IED in Afghanistan and lost his legs and an arm. He reveals what, and who, helped him to make a remarkable recovery
    Isis in Iraq: Yazidi girls killing themselves to escape rape and imprisonment by militants

    'Jilan killed herself in the bathroom. She cut her wrists and hanged herself'

    Yazidi girls killing themselves to escape rape and imprisonment
    Ed Balls interview: 'If I think about the deficit when I'm playing the piano, it all goes wrong'

    Ed Balls interview

    'If I think about the deficit when I'm playing the piano, it all goes wrong'
    He's behind you, dude!

    US stars in UK panto

    From David Hasselhoff to Jerry Hall
    Grace Dent's Christmas Quiz: What are you – a festive curmudgeon or top of the tree?

    Grace Dent's Christmas Quiz

    What are you – a festive curmudgeon or top of the tree?
    Nasa planning to build cloud cities in airships above Venus

    Nasa planning to build cloud cities in airships above Venus

    Planet’s surface is inhospitable to humans but 30 miles above it is almost perfect
    Surrounded by high-rise flats is a little house filled with Lebanon’s history - clocks, rifles, frogmen’s uniforms and colonial helmets

    Clocks, rifles, swords, frogmen’s uniforms

    Surrounded by high-rise flats is a little house filled with Lebanon’s history
    Return to Gaza: Four months on, the wounds left by Israel's bombardment have not yet healed

    Four months after the bombardment, Gaza’s wounds are yet to heal

    Kim Sengupta is reunited with a man whose plight mirrors the suffering of the Palestinian people
    Gastric surgery: Is it really the answer to the UK's obesity epidemic?

    Is gastric surgery really the answer to the UK's obesity epidemic?

    Critics argue that it’s crazy to operate on healthy people just to stop them eating
    Homeless Veterans appeal: Christmas charity auction Part 2 - now LIVE

    Homeless Veterans appeal: Christmas charity auction

    Bid on original art, or trips of a lifetime to Africa or the 'Corrie' set, and help Homeless Veterans
    Pantomime rings the changes to welcome autistic theatre-goers

    Autism-friendly theatre

    Pantomime leads the pack in quest to welcome all