It isn't as easy as you might think.

Three years ago, I pondered the problem with the Ethical Man producer, Sara, for a couple of days before we had a moment of genius.

Our solution infuriated my wife, enraged my colleagues and alienated a large section of our audience but I still stand by it.

So what was this brilliant idea?

We decided that I should illustrate the impact of flying by jetting off for a weekend in Jamaica.

I know. That's what my wife thought too.

And to make matters worse I filmed the moment I revealed our plans to her. You can watch my marriage disintegrate here.

Please tell me if you think our approach was misguided.

For the record, here's my defence. We reasoned that if you watched our film and thought the idea of a man calling himself "ethical" flying off to Jamaica for the weekend smacked of hypocrisy, it might make you reflect on your own behaviour and consider flying less.

And, because we were keeping a tally of my carbon footprint, we reckoned the record of my flight would serve as a reminder of just how carbon-intensive flying is.

I did say this at the time but, judging by the avalanche of outraged emails we received, it fell on deaf ears.

The truth is, flying is the single most intractable climate change issue.

There is a solution to most of the other stuff - we can cut our energy use, change how we generate power, drive electric cars, eat less meat etc... but there is no alternative to flying.

And how we love to fly. A least one foreign holiday a year now seems to be regarded as pretty much a right of citizenship. Which is why politicians are so worried about stopping us doing it.

Why is flying such a problem?

Let's start with the good news: a couple of years ago I looked into the numbers and found that modern jet aeroplanes are actually a very efficient form of transport .

The jet engine is actually one of the most effective ways to convert the energy from fuel into thrust. The best jets are 37% efficient. By contrast modern petrol engines are around 25% efficient while a finely tuned diesel will achieve, at best, 32% efficiency.

How does that translate into actual fuel consumption?

Take a look at some figures: my old car - a two litre petrol Saab 9-5 estate - uses 8.6 litres per 100km.The most efficient cars do better than that. The Toyota Prius, for example, is much more frugal. It uses 4.3l/100km.

So what about aircraft? The average jet plane now uses around 4.8l/100km per passenger - just a little worse than a Prius with no passengers. But the manufacturers say modern jets are much more efficient.

Airbus claims it makes the most efficient aeroplane currently flying, the A380. It says this behemoth uses just 2.9l/100km per passenger. (Here's the dull bit: that's the fuel consumption when you assume a three class configuration operating at capacity with 525 passengers.)

So far as I can tell, the latest jumbos are similarly efficient - it is hard to be certain because the manufacturers do not publish comparable figures - but Boeing's 747-8 uses 3.7l/100km per passenger when operating at 70% capacity. (Assuming it is configured to hold 470 passengers in three classes.)

So, if jet engines are more efficient than car engines why do they get such a bad rap?

The anwer is pretty obvious - we use planes to travel extremely long distances. That weekend in Jamaica racked up just over 15,000km. That's pretty much what the average British driver would do in an entire year.

The other problem is that planes release their pollutants high up in the atmosphere where they have an even stronger greenhouse effect. The process is known as radiative forcing and means aircraft emissions are reckoned to be almost twice as damaging as emissions at ground level.

So, combine the distance you fly with the effect of radiative forcing and you can see why our appetite for air travel is so worrying.

You can do as I did - get rid of your car , switch to energy efficient bulbs , eat locally grown food - but take one holiday flight and you will erase all your careful carbon cuts.

So what are the alternatives?

Here's the rub. As my figures show, even if you did take the car instead of the plane you would still emit huge amounts of carbon, because of the vast distances covered in most journeys by air.

I've already done the maths on trains and buses. If you pack them full of passengers they will offer some carbon savings but, like cars, they leave the tricky little challenge of crossing oceans. Boats will do that job but there's a hefty carbon price to pay there too.

And these alternatives ignoring perhaps the most important feature of flying: it is extremely fast.

Lots of environmentalists regard speed as some kind of crime but much (not all) time spent travelling is time not spent doing something else - often a productive activity. So there is an economic cost to slow travel.

So what's the answer?

It's a tough one isn't it? Do write in if you've got any good ideas.

In the meantime how about this: establish a price system that accurately reflects the impact that carbon emissions have on the environment? That way the price of a plane ticket would include all the costs of our holiday.

It would mean we would all fly less, of course. But, given the problems my weekend in Jamaica caused me, maybe that would not be such a bad thing.

Read on, because I will tell you how to just that. I will show you how to take a substance we all throw away and convert it into something useful.

The discovery came at a high price. It involved making one of the most humiliating television reports ever broadcast by the BBC.

BE WARNED: this report features nudity, public urination, a surprising swimming pool sequence, a discussion of one of our most taboo topics and a shocking shower cap.

It also features footage of a minor celebrity in his Speedos - can anyone spot him?

So what has saving water got to do with making a fortune?

The answer lies in that back garden in York, featured in the video. What I saw there led me in search of the man who inspired the system.

And - three years later - I managed to track him down in his cabin in the backwoods of Pennsylvania.

The man I met in his home in the woods earlier this year has developed a revolutionary new system for dealing with one of the most fundamental processes on earth. By doing so he has become an inspirational leader, not just for John in York, but for tens of thousands of people around the world.

He has - how shall I put this? - started his own movement.

He's called Joe Jenkins and is the author of The Humanure Handbook, the world's first guide to composting your own poo.

That's right, the book that Britain's "king of compost", John Cossham, says "changed his life".

Obviously, I am alive to the comic aspects of these two men's obsession but the problems caused by human sewage are no joke. Sewage pollutes water and spreads disease. Millions of people around the world die every year from illnesses spread by sewage.

It is expensive too. Joe claims that we each produce over a kilo of the stuff every day - a total of half a tonne a year. That's 30 million tonnes of human sewage every single year in Britain. Disposing of all that waste costs hundreds of millions of pounds a year.

Which is where Joe's system comes in. Instead of regarding human excrement as a waste product Joe sees it as something that can be useful.

Our sewage is full of nutrients: "faeces and urine," writes Joe in his book, "are examples of natural, beneficial, organic materials... they are only waste when we discard them."

What Joe's composting system does is capture those valuable nutrients and return them to the soil.

Joe collects his and his family's waste and converts it into a rich compost which he uses to fertilise his garden. Thereby, says Joe, "closing the human nutrient cycle".

I ate a venison chilli Joe prepared with "humanure" fertilised tomatoes from his garden. Delicious!

Of course the idea of composting human excrement is not new, people have been doing it for millennia. What Joe has done is brought a scientific approach to the process. He has shown that, when composted properly, all the pathogens in poo are destroyed.

He has also demonstrated that "humanure" composting can be done almost anywhere. There are composting toilets based on Joe's system everywhere from Manhattan apartments to yurts on the Mongolian steppes.

And Joe's experiments with "humanure" can cut carbon emissions. It takes huge amounts of energy to fix the nitrogen used in most commercial fertilisers and they cause the release of huge amounts of nitrous oxide from the soil. And nitrous oxide has 296 times the global warming power of carbon dioxide.

Greenpeace estimates the effects of nitrous oxide and the emissions from the energy required to make fertiliser together account for almost half of all the direct emission from agriculture - that works out at almost 5% of total world greenhouse gas emissions!

Joe is convinced that large-scale "humanure" production could become a source of low-carbon fertility for the soil.

It could also reduce the 3.4% of the world emissions generated by waste processing.

This year, Joe has been exploring how his composting processes can be scaled up. He's had an intern from a local university working full time on the project. The ultimate aim is to make composting human waste into an industrial process.

His book and sales of his toilet system have earned Joe a very comfortable income.

The fortune will come if he can achieve his dream - spreading "humanure" across the world.

So who wants to take this technology on? Are you ready to install a composting toilet in your house?

(You will be pleased to know that, in keeping with the ethos of the Ethical Man project, this article is recycled from a previous post. Also, Francis Maude is now Shadow Minister of the Cabinet Office rather than Chairman of the Conservative Party, as he was in 2006 when the first video was filmed - but there is no reason to suppose that this has changed his approach to composting.)

Update 1545 30/11/09: Some eagle-eyed readers spotted a mistake in my copy (see comments below). This has now been corrected.
Update 1600 30/11/09: In the interests of clarity, the change referred to above was made yesterday.

This article is about why the calories we consume make it so difficult for democratic societies to tackle climate change. If that sounds ridiculous then please bear with me.

We normally only worry about what the calories in our food will do to our waistlines, but calories can also be used to measure the energy in fuel.

What do you think your total calorie count would be if instead of calculating the energy you need to eat to stay healthy you added up all the energy you use to keep yourself warm, to travel around, to produce the food you eat and the entertainment you enjoy?

The difference between those two figures - how much it takes to keep us alive and how much energy we actually use - is a measure of the challenge that tackling global warming presents.

It also explains why democracies may never be able to get to grips with the problem.

I'll come to the actual figures soon, first let's explore the link between calorie counting and the big issues.

It's pretty simple really. In most modern societies the vast majority of the calories we use come from not from food but from fossil fuels. And fossil fuels - as everyone now knows - produce greenhouse gases which, in turn, cause climate change.

We all now also know the risks that climate change presents. We know that, if unchecked, scientists expect it to cause droughts, floods and storms which will disrupt agricultural production around the world and lead to famines, mass migration and conflict.

I know what you are thinking. You are thinking he's about to lay a dieting metaphor on me. And you are right - but only up to a point.

Of course a diet is the answer. Cut out all those fossil fuel calories we use and bingo! Problem solved. My question is whether our political systems will ever be able to put us on the diet the world needs.

Anyone who has been on a diet knows how unpleasant and difficult it can be. And make no mistake this fossil fuel diet is going to be uncomfortable too.

Fossil fuels are an extraordinarily concentrated energy source and moving to alternatives will have a cost. It will mean we have to change the way we do things, and many people will find that difficult and unsettling.

Regulating or taxing fossil fuel use will raise the price of energy and -at least in the short run - that's going to push up the price of pretty much everything.

Bizarre as it might sound, that may not actually mean we pay more. If you improve the insulation in your home or drive a more fuel efficient vehicle then energy prices can rise and you still end up paying less.

What's more higher prices for energy from fossil fuels should spur a move to renewable energy sources and make them much cheaper in the long run.

But the key point is this. Along the way it will mean some sacrifices and some big changes and many people are going to find that uncomfortable.

What is more, the systemic nature of the changes that are needed mean we can't expect individuals to do it on their own. This diet is going to have to be forced on us by government - which is where the tricky little problem of democracy comes in.

The challenge for democracy is this: will we - the electorate - ever vote for a government that will force us to use less fossil fuel?

President Obama said he'd try and do just that. You can see what happened to his promise and follow my madcap journey around America on BBC2 tonight at 7.00pm.

Of course, democratic societies have risen to some pretty big challenges in the past. They've overcome war, depression and social upheaval.

But climate change is a bigger challenge than even a world war.

Climate change requires people to recognise the need for a unique trade-off. We need to agree to make sacrifices now - the diet - to deal with a threat that lies way in the future.

And democracies tend to be poor at long term planning. Unpopular politicians don't get elected and telling people they have to make sacrifices is not going to make a politician popular unless there is a damn good reason.

Most voters would recognise that the German army threatening to invade is a good reason. The threat of global warming is a tougher proposition.

It requires that the electorate believe the science. They need to believe that the invisible gases produced by the very activities that make modern life so comfortable will slowly make the world less and less inhabitable.

And science is contestable. Just take a look what happened when I appeared on an American talk radio show.

Like dieters who find excuses to have that one cream cake or another glass of red wine: people are going to find excuses to avoid a fossil fuel diet.

And the tougher the diet, the more likely people are to try and avoid it. So what's our calorie count?

The average woman needs 2,000 calories a day to stay healthy. Men get a bit more. We need 2,500 calories a day.

In America the average person uses the equivalent of 216,728 calories every day, not including food - over 100 times more.

In Britain we use around half the amount of energy - a which works out at around 106,000 calories a day. It is more modest, but still a huge daily diet of calories.

So here's the big question, will democratic politicians be able to tackle climate change in societies as energy-hungry as ours?

The truth is that ultimately only you the voter can answer that question - at the ballot box.

What I am going to say will challenge everything you have heard about environmentally friendly lifestyles.

I am going to argue that cars can be greener than public transport.

But before I do, I should put my cards on the table. I'm a pretty ordinary bloke. I love driving and have been a car owner and driver ever since I passed my test. But I was forced to get rid of my car after I was press-ganged by the Newsnight editor into a year-long experiment in ethical living.

It was a sad moment as I stood with my family in 2006 and watched my precious Saab being winched away from outside my home.

You can see my humiliation for yourself here and judge for yourself whether you think my experiences have clouded my judgement on this issue.

Since that fateful day - and I've remained car-free all this time - I've been studying the carbon consequences of car ownership.

So let's look at the facts.

It is true that at first glance cars appear to compare very badly in terms of carbon dioxide emissions to other forms of transport.

The average car emits something like 180g per passenger kilometre.

You may be surprised to learn that, on that basis, taking the car is less environmentally friendly than taking a typical, well-filled short-haul plane, which emits 150g/km per passenger.

The figures show trains to be much greener, as you might expect. According to its publicity, one of Virgin's new Pendolino trains travelling half full up the West Coast main line clocks up just 27g per passenger kilometre.

But it is quite easy to tilt the statistics in favour of the automobile.

Cars appear very inefficient because, more often than not, just one person travels in a car. Pack in extra passengers and you quickly make the car a dramatically greener option.

The extra weight does increase fuel consumption - but only very marginally. Why? Because each additional passenger only weighs a tiny fraction of the weight of the car itself.

Think about it. The average car weighs in at over a tonne. Meanwhile the average passenger weighs around 70kg (the average British woman weighs 65kg and the average man something like 75kg).

That means each additional passenger adds just 7% of extra weight. Taking our average vehicle, that works out at just over 12g/km per extra passenger.

So, if I pack my family of five into a car, the average emissions per passenger falls to just 45g/km (and that's not taking into account the fact that most members of my family are very small).

But - I can hear the greens amongst you protesting - the train still wins out. Does it? Really?

Earlier this year, the Guardian and New Scientist writer Fred Pearce dug a bit deeper into the green claims made by train companies.

He found that most Virgin trains are nowhere near as clean as the Pendolinos. Virgin's most modern diesel train, the Voyager, emits 74g per passenger kilometre when travelling half-full. That's almost three times as much as the Pendolino, and half as much again as each member of my family travelling by car.

Travel on a Voyager when it is a quarter full and your emissions per kilometre travelled are about the same as sitting in a fullish plane. "More leg room", says Fred, "but no greener."

Catch a half-full sleeper up to Scotland and your carbon footprint is much worse. He calculates that with 12 people in a carriage you'd be lucky to emit less than 200g/km.

And the truth is, buses don't do much better. According to figures from the US Department of Energy, a bus with average occupancy (9 people) is more polluting than a car with average occupancy (1.57 people).

The figures are likely to be pretty similar in the UK. Some suburban bus routes in London are subsidised to the tune of £10 per passenger journey apparently (at least, that's what a mole inside the Mayor's office tells me). That suggests very low occupancy, and therefore a whopping carbon footprint.

But am I being fair comparing a car full of people with an empty bus or train?

It is true that full buses and trains are significantly less polluting per passenger than cars (even cars full of passengers). The problem is, for most of the day our buses and trains are far from full.

I couldn't find good occupancy figures for UK public transport systems - please help me if you can - but it seems most of our buses and trains are far from full most of the time.

That's because public transport systems are designed to meet peak demand.

Double-decker buses make a lot of sense in the rush hour but rumble around our cities almost empty in off-peak periods. Indeed, even at peak times every packed rush-hour bus is likely to make its return journey nearly empty.

And public transport has to offer a frequent service all day long. People won't use buses and trains unless they know they can get to where they want when they want.

We could run smaller buses in off-peak periods to cut emissions but think of the cost: bus companies would have to buy twice the number of vehicles. Read more about why public transport can be high-carbon here.

Should we conclude from this that the green choice is the car?

Here's where I get back on message. Even though travelling by car can be less polluting than public transport you should always take the public transport option.

That's because buses and trains are running anyway. They will be out there generating CO2 whether you ride them or not. So when you choose to take your car, the pollution you create will be on top of whatever the public transport option is producing.

The other key point is that my argument only really holds so long as you have other people in your car with you. Travel alone - the statistics show - and the car is, just as the greens claim, one of the most polluting forms of transport on earth.

So how have I got on without my Saab?

Well, despite my misgivings about getting rid of it, the truth is I found life without it much easier than I thought.

I recognise that giving up the car will not be so easy for most people. I live right in the heart of London, where public transport is almost always quicker and easier than taking the car.

But if you insist on continuing to use your car, you can get some tips on driving the low-carbon way in this video (made several months after I gave up the Saab). You can also see how a friend and I came up with a novel way of using my car to cut both our carbon footprints.

Wolfgirl asked: Does Mr Miliband offset any of his personal emissions? If not, why not? Does he think that offsetting emissions can help us to tackle climate change?

"The first thing I do is look to reduce my emissions. So I take the train and have taken steps to reduce the energy I use in my home.
 
"Carbon offsetting is not a cure for climate change, but it can help raise awareness and reduce the impact of our actions.
 
"Offsetting can be useful when we need to compensate for unavoidable emissions. In this way, offsetting can play a useful part in helping to meet carbon reduction targets.
 
"Robust offsetting projects can, however, provide a route for investment in clean technology in the areas which lack it the most. This investment really does help lead to the spread of low-carbon development across entire regions.
 
"The government is becoming increasingly aware of the environmental impact of travel by our ministers and officials. That's why we have offset all our emissions from air travel since April 2006."

MrWaves asked: Given that so many technologies such as wave, tidal, carbon capture and large scale solar are still in their infancy, how will we grow at least some of these into worthwhile energy sources and how do we plan with so much uncertainty?

"Wave and tidal energy and clean coal have enormous potential, and I'm proud that the UK is seen as a world leader in the development of these cutting-edge technologies. All are going to be necessary, we can't pick and choose.
 
"We are working closely with industry to develop these technologies that aren't yet commercially viable. That's the government taking a strategic role in helping that technology along.
 
"Just last week we published our new clean coal policy - which is the most environmentally ambitious set of coal conditions of any country in the world. It says that there will be no new coal without carbon capture and storage.
 
"Our island nation also means we've got huge potential in the area of wave and tidal energy and there's loads of work already underway. We've recently made £22m available to developers to accelerate the commercial development of marine energy in the UK. Work began this month on a 'Wave Hub' in south-west England which will help developers test their designs, and we have a £50m Marine Deployment Fund for the projects once they are ready for commercial testing.
 
"So we are putting the measures in place to develop these technologies - which will all be vital as we decarbonise our energy supplies."

DocDim asked: Does Mr Miliband see such initiatives as Copenhagen as having more or less value than actions taken by individuals, such as assuming a suitable moral stance (intrinsically motivated) as opposed to one decreed by governments (extrinsically motivated)?

"The bottom line for me is that politicians and governments have got to take a lead in sorting the problem out, and that's where Copenhagen comes in. We can't afford for any country to be left out, or left behind. And the UK has been pushing really hard to get the most ambitious deal possible.
 
"But 'Doc Dim' is right to bring up the role of individuals. Individuals all over the world have and must continue to play a vital role in mobilising and putting pressure on their governments to do the right thing when it comes to the climate.
 
"There's also the simple things that we can do in our homes - we're all part of the solution. Some 40% of the UK's emissions are down to what we do in our personal lives - transport, heating, power use. It would be wrong - and impractical - for government to just leave it at that, and say 'it's over to you and it's your responsibility'.
 
"Governments should make sure that we put in place the measures and help so that people play their part in tackling climate change, find it easy, and that it doesn't cost too much. That's what we're doing through our pay as you save home insulation pilots, to the new clean energy cash-back schemes for people who start to generate their own energy.
 
"Personally, I think it's not a good idea for politicians to lecture the public. It's my role to communicate a message of optimism and hope - not a message of gloom and defeatism."

Brightyangthing asked: If a means of power generation for the future had to be 'in your back yard', and assuming that without it, you would have no domestic heating or lighting three days a week, which box would you tick: Wind farm, Coal-fired power station, Nuclear, Other?

"Firstly, no-one is going to have a nuclear power station or a coal power station in their back yard - there's pretty strict rules on where they get built, as you'd expect!
 
"But people's back yards could be great for small-scale technology such as a ground source heat pump or solar panels. And from next year, through the clean energy cash-back scheme, people are going to be able to produce their own clean energy in their back yard and get paid for doing it as well.
 
"In my local area of Doncaster, we already have a coal power plant which could be one of the first in the world to develop CCS, and there are plans to build wind farms too.
 
"But we need all kinds of energy technology across Britain - in the right places - to supply us with the secure low carbon energy we need in the future. And we shouldn't forget the jobs and economic benefit that this investment brings to each area."

That's what my wife and I were asking ourselves a couple of years ago after I, rather recklessly, agreed to accept a BBC challenge to try to cut the family's greenhouse gas emissions.

Here's how we got on and - as you will see - we started our eco-makeover with our home - a pretty sensible place to begin, as our homes are together responsible for a quarter of this country's carbon emissions.

Trying to make my home more carbon efficient taught me a very important lesson - the only way to get significant cuts is if you look at all aspects of your home.

You can't just put in a bit more insulation, you also need to turn down your thermostat, change the bulbs, get thicker curtains etc, etc, etc...

But one area of our home lives always tends to escape under the ethical radar - our pets. I think it is time to give them the "ethical" attention they deserve.

First, a few pet related facts:

• The most popular pets are, overwhelmingly, cats and dogs
• According to the Pet Food Manufacturers Association dogs sneak into the number one spot - six million UK households (23% of the total) own a dog
• Cats are pretty close behind though, 5.2 million UK households have at least one cat (20%)
• In terms of actual numbers our affections are evenly split - we own eight million of each

That's right 16 million dogs and cats!

I know what you are thinking... and the average dog is reckoned to produce half a tonne of the stuff in its 10-year life.

But it is not what comes out of our dogs and cats but what goes into them which presents the biggest environmental dilemma of pet ownership.

What I am talking about is our pets' environmental "pawprint".

A big dog like a Labrador or Alsatian consumes around 1,000 calories a day - half that of an adult woman.

And, because dogs (and cats) are primarily carnivorous, they get those calories from the most carbon intensive of foods - meat.

The issue of carbon pawprints has been in the news recently thanks to a new book: Time to Eat the Dog.

The authors have attempted to estimate the environmental impact of a range of popular pets.

Their most startling conclusion is that dogs are significantly more damaging to the planet than SUVs.

The authors claim that keeping a medium-sized dog has the same ecological impact as driving a 4.6 litre Land Cruiser 10,000km a year.

They use a rather unusual method of calculating environmental impact.

Instead of measuring emissions of CO2, or CO2 equivalent, they calculate the literal footprint or "global hectare" (gha) - the amount of land it takes to support a given activity.

So they work out that constructing and driving the Land Cruiser for a year takes 0.41 gha.

Growing and manufacturing the 164kg of meat and 95kg of cereals a border collie or cocker spaniel eats every year takes about 0.84 gha.

A bigger dog such as a German shepherd consumes even more - its pawprint is more like 1.1 gha.

By their reckoning, that is more than the environmental footprint of the average Indian person, who uses just 0.8 gha of resources.

If you are a multiple dog owner you are in even more trouble. Two big dogs have a bigger carbon footprint than some British citizens.

According to the book the average resident of Cardiff requires just 1.89 gha.

The average American, by contrast, requires a whopping 9.5 gha.

You will be glad to hear that other pets are not so damaging.

A cat needs 0.15 gha, a hamster 0.014 gha, and a canary 0.007 gha.

The most carbon efficient pet is a goldfish. Its tiny "finprint" requires just 0.00034 gha.

So how can we get the companionship and pleasure of pet ownership without it weighing too heavily on our carbon consciences?

The authors have an answer to that - we need to start eating our pets!

They suggest that instead of dogs and cats we should keep chickens and rabbits which will keep us company and make a tasty dinner too.

What will you do with your pet dog now you've been convinced that he or she is an enemy of the environment?

The book draws a blank here. It doesn't have a single recipe for dog!

So if you are planning to pop your pooch in the pot here's a link that will tell you how to make a really tasty dog stew.

Enjoy.

I'll post them as soon as they come in.

Those talks may sound distant and abstract but if a deal is done it will begin a process that will affect all of us, changing how we live our lives.

Why? Because the Copenhagen talks are about how the world will cut greenhouse gas emissions. That will affect us all because almost everything we do involves greenhouse gases one way or another.

Think about it. As soon as you start up your car, put on the kettle, turn up the thermostat a notch or even buy a bag of potatoes you are creating carbon dioxide, the key greenhouse gas.

So those talks aren't abstract. Ultimately they are about everything we do: how we travel, how we heat and power our homes, what we buy, what we eat.

So how might our lives change?

Well, I've got a pretty unique insight into that question because I was involved in a bizarre BBC experiment.

My family and I were challenged by my editor on Newsnight to spend a year doing everything we could to cut our greenhouse gas emissions.

To be honest I thought it sounded really dull - a kind of muesli correspondent. I'd pictured myself more as the jet-setting foreign correspondent. But this was my very first day on the programme so I told him what a great idea I thought it was and... well, you can guess what he said next - he wanted me to do it.

And, to be fair, it was actually a very good idea. Take one fairly ordinary family. Then apply the latest thinking on low-carbon lifestyles. Then watch the results!

It was a combination of the utter humiliation of a reality TV challenge with a serious inquiry into the role of individuals in tackling climate change. So you get to see whether lifestyle changes and new technologies really do cut carbon emissions AND get the vicarious pleasure of watching a family suffer as they try and live a more ethical life.

In the run up to the Copenhagen conference, we'll be featuring those films here on the BBC website.

Here's the first one, where I attempt to get to grips with what the challenge is actually going to mean for me, my wife and our two young children.

Watching the film again after three-and-a-half years is very odd for me. It's amazing how much the kids have grown but it is also amazing just how much the nature of the debate has changed.

I remember sitting down with Sara, the Ethical Man producer, to discuss whether we needed to explain the idea of a "carbon footprint". It was a new concept back then. Now put the words into a search engine and you get millions of results.

It felt as if we were venturing into new territory. Of course there are lots of people who have been worried about their impact on the environment and have been trying to live low-impact lifestyles. But they tended to be deep greens, the sort of people who would be happy to live in a yurt.

Cutting carbon emissions simply wasn't an issue that preoccupied most people.

Now many newspapers have "ethical" correspondents. Companies will boast about their green credentials. Adverts will tell you how low-impact the foot spa you are about to buy is.

The debate has certainly changed but the fact is most of us have not changed the way we live.

That fact has prompted me to agree to another unreasonable request from the Newsnight editor. I have agreed that he can turn our home into a temporary television studio in the run-up to the Copenhagen conference.

Since what is being discussed at the conference is ultimately about how we all live our lives, then where better to discuss the issues it raises but in a fairly ordinary home?

We'll be inviting world leaders, top scientists, environmental campaigners - in fact anyone else we think is interesting - to join me around my kitchen table. They'll get a mug of tea and then we'll discuss the key issues.

The first of these experiments in broadcasting will be on the programme tonight. My house guests include none other than the climate change secretary himself, Ed Miliband.

We'll be discussing what might actually be agreed at Copenhagen and what it will mean for us all. So tune in at the usual time - BBC2 at 2230 GMT.

If you've got any questions for Mr Miliband, please send them to me here.

I'd also be very grateful if you have any tips you might have on interesting or innovative ways we can all cut our carbon footprints.

UPDATE - HERE IS THE FILM FROM MONDAY NIGHT IN WHICH JUSTIN IS JOINED AT HIS HOUSE BY CLIMATE CHANGE SECRETARY ED MILIBAND, ECONOMIST VIJAY JOSHI AND SARAH-JAYNE CLIFTON FROM FRIENDS OF THE EARTH TO DISCUSS THE COPENHAGEN CONFERENCE.

In the US state of Virginia the talk is of revolution. In the basement of a restaurant in Richmond we met 100 or so American patriots -ordinary people who claim to be the vanguard of a great new movement, a movement for American liberty.

"Lower taxes, less government, more freedom", is their rallying cry.

The words of Patrick Henry, a son of Virginia and one of the founding fathers of the United States, ricocheted around the room: "Give me liberty, or give me death."

The echo of the American Revolution is deliberate. This movement takes as its manifesto the Declaration of Independence itself. Many supporters say they carry a copy of it with them at all times.

The meeting in the Richmond basement was organised by a group called FreedomWorks. Supporters describe themselves as "conservative" but they are not necessarily Republicans.

Greenhouse gas cap and trade

Their call to arms focuses on two issues: healthcare reform and - you guessed it - President Barack Obama's plan for a cap and trade system to regulate greenhouse gas emissions.

It presents its aggressively libertarian, small government agenda as a direct challenge to the politics of the new administration.

It claims to be engaged in nothing less than a battle for American freedom.

The scale of this new revolutionary army became apparent in September with a giant rally in Washington to commemorate the day after the 9/11 attacks on the Twin Towers.

A day when, the movement says: "we were united as Americans, standing together to protect the greatest nation ever created".

How many actually attended is contested. According to the official count tens of thousands marched; the organisers say hundreds of thousands, even millions turned out. But there is no question this movement has wide appeal.

It has been picked up and fostered by the right-wing media, in particular Fox News and its anchormen Glenn Beck and Sean Hannity.

Potent appeal

But this cannot be dismissed as a trivial media confection.

The notion of freedom this movement promotes has potent appeal here in the US.

It is rooted in the founding principles of the US themselves - the "inalienable" rights to life, liberty and the pursuit of happiness that the Declaration of Independence holds to be "self-evident".

This is the idea that individuals have inherent rights, including property rights, which may not be arbitrarily overridden.

(An idea that is, incidentally, arguably Britain's greatest legacy to the US).

The movement argues that the Declaration is a charter for small government and quotes George Washington in support: "Government is like fire, a handy servant, but a dangerous master."

They claim that the Obama administration's cap and trade plans, together with its stimulus package and its plans for healthcare reform, represent an unwarranted incursion into the rights of Americans.

Unworried by climate change

These conservatives are changing the context in which the Obama administration has to make its case for government action on climate.

The argument that the effects of climate change will make pursuing life, liberty and happiness very difficult just does not wash with them.

Most of the people I spoke at the Richmond meeting did not believe climate change is something they need worry about.

A recent poll found most Americans agree. Just 35% describe global warming as a "serious problem".

Debate on how to tackle a problem becomes very difficult when people do not believe it is a problem that needs to be solved.

As the meeting broke up one man took me aside to say he was not persuaded by the arguments he had heard.

"You are in a state that fought for the freedom to keep people in slavery," Phil told me.

Meaning of freedom

Indeed, Patrick Henry, who demanded liberty or death as he helped launch the revolt against British tyranny, subsequently worked to defend the slave trade as an attorney.

Phil told me the story of Gabriel, a slave who, 24 years after the Declaration of Independence, attempted to lead a rebellion against the slave owners here in Richmond Virginia.

Gabriel turned Patrick Henry's words around - "Death or liberty" was his slogan.

Liberty eluded Gabriel. He was betrayed and his rebellion was crushed by the Virginia state militia before it had even begun.

Gabriel was hanged just a couple of blocks away from the cellar where the FreedomWorks meeting was held.

"Freedom means different things to different people," Phil said as he left the meeting.

West Virginia is the mountain state. Its mountains have defined the state's history, and now the mountains of Virginia look set to determine whether the world begins to tackle global warming.

That may sound a little apocalyptic, but please bear with me.

The American nation was born in Virginia where the tobacco plantations - established in the early 17th Century - gave the country its first economic boom.

Neighbouring West Virginia, by contrast, remained a rural backwater thanks to its vertiginous topography.

A life shaped by terrain

The mountains of West Virginia are not high, but boy are there a lot of them. As a result, the state had little to attract settlers.

The sea of mountains makes travel difficult and farming near impossible. West Virginia's only significant industries until the middle of the 19th Century were salt mining and charcoal burning.

And, 150 years on, West Virginia is still predominantly a rural state. Its population is less than two million, its state capital, Charleston, has just over 50,000 residents.

So how come this remote, rural state is playing a pivotal role in determining the international deal on greenhouse gas emissions that is likely to be done at the Copenhagen conference?

The reason comes back, again, to those mountains.

West Virginia remains economically isolated. There is still virtually no industry here. It is the third poorest state in the union in terms of per capita income.

But there is one thing West Virginia has mountains of - and I mean literally mountains -and that is coal.

The US Department of Energy estimates that West Virginia has 28.5bn tonnes of high quality coal left. That's right, 28,500,000,000 tonnes of energy-rich, carbon-dense, bituminous coal.

You get a sense of the true scale of that figure when you meet some of the guys who dig the stuff up.

Foundation of industrial America

The miners I met up in the hills outside Fairmont all work a single seam of coal, the famous Pittsburgh seam, one of the greatest mineral resources in the US.

The seam is up to eight feet (2.4m) thick and runs for hundreds of miles from Maryland to Ohio and from Pennsylvania deep into West Virginia.

It is so vast it has been being worked constantly for almost 200 years.

Indeed, the Pittsburgh seam can reasonably claim to have laid the foundation for the industrialisation of the US.

It is perfect for coking and therefore perfect for making steel, as industrialist Andrew Carnegie discovered. His great fortune was made using Pittsburgh seam coal to make the steel that built modern America.

One of the miners I met, DJ Weaver, is the fourth generation of his family to mine the Pittsburgh seam.

He, his father, his grandfather and his great-grandfather all spent their lives working Pittsburgh, and there is reckoned to be enough coal left for another couple of generations of the Weaver family to be employed on the seam.

And the Pittsburgh seam is just one of West Virginia's coal reserves.

Pivotal position

Not surprisingly, coal dominates the economy of this state and has also shaped its politics.

The governorship, two of the state's three House of Representatives seats and, crucially, both Senate seats are held by Democrats.

It is those two Senate seats that have put West Virginia in such a pivotal position in terms of climate legislation.

The Obama administration needs 60 Senate votes for its climate bill if it is to avoid a Republican filibuster - a roadblock to the bill.

The electoral calculation only adds up so long as every Democratic senator votes with the administration.

But both Democratic senators here in West Virginia have said they will vote against the bill.

That means Senator John Kerry, the former presidential candidate who is sponsoring the bill, is looking for compromises that might draw them back into the fold.

He is also being forced to consider inducements - like offshore drilling permits and incentives for the nuclear industry - which might attract wavering Republicans.

In short, West Virginia's opposition to the Senate climate bill will end up watering down America's position on climate.

That, in turn, will dilute any deal done at Copenhagen .

It may seem extraordinary that a sparsely populated, rural state like West Virginia could hold such sway in international politics, but the logic here on the ground is compelling.

"What would you do if the mines closed?" I asked the miners.

They shook their heads: There aren't any good jobs outside of coal here", they told me, "West Virginia is coal".

There are just 42 days left until the world's environment ministers will sit down around the negotiating table in Copenhagen to try to agree a deal to begin to cut greenhouse gas emissions.

The original objective for the conference was to produce a new international treaty to replace the Kyoto treaty. Now even the UN's climate change chief, Yvo de Boer believes the talks this December will not achieve that.

So why have international ambitions for the conference been so dramatically scaled back? A key answer is the US' position on the climate issue.

In the weeks after President Barack Obama took office I travelled 6,000 miles (9,656 km) around the US looking at the efforts the country is making to tackle climate change.

Mr Obama said his administration would lead the world on tackling global warming and we found all sorts of exciting examples of how the world's most powerful nation is facing up to the climate challenge.

In Detroit we saw how some of the country's biggest corporations are putting their muscle behind legislation to limit carbon emissions, in Washington we met an army of activists ready to take their battle on climate onto Main Street, in Texas we found a thriving wind industry right in the heart of the oil state, and in California we discovered how regulation had been used to foster energy efficiency.

Eight months on, and the Ethical Man team has returned to America.

The story seems very different now. Many commentators believe Mr Obama's plans for a cap and trade bill to limit the US' greenhouse gas emissions have become fatally mired in the Senate.

It now seems likely that America will go to Copenhagen without a firm commitment to reducing its own greenhouse gas emissions. Indeed, Mr Obama is now not even expected attend Copenhagen summit.

The problem is, without a clear commitment to cut American emissions, a comprehensive deal is very unlikely.

Why? Think about your own life. Imagine you want to do your bit to reduce your impact on the environment. You splash out on new insulation and double-glazing. You sell your gas-guzzling people carrier and start catching the bus. You stop jetting off to the sun and you turn down the heating in your home.

Fine. You've cut tonnes off your carbon footprint.

Now imagine you look over the hedge into your neighbour's house. It is winter and he is sporting the sort of tan you only get in the tropics. He is drinking a cold beer under the heat of a roaring patio heater. Parked in his drive you see a brand new top-spec Range Rover.

Do you still feel so good about all the sacrifices you have made to try and save the world?

The US is no longer the biggest polluting nation on the planet - China knocked it off the top spot last year. But look at historic emissions - if you add up all the greenhouse gases emitted over the last 100 years the US comes in at first place by a considerable margin.

The fact is that if the US refuses to cut its emissions other countries are likely to refuse too - or at least do a lot less.

We have come back to America to ask whether, in these last few weeks, the Obama administration will be able to pull a deal on its own emissions out of the bag.

We will be following the progress of the climate bill in the Senate. Can former presidential candidate Senator John Kerry scrape the majority he needs to get the bill passed?

We will look at how the American right has been organising its own army of activists to campaign against the cap and trade legislation and at the tactics of the coal and oil lobbies.

I will also be exploring whether the administration has an alternative plan up its sleeve if cannot get the climate bill through.

Once again, it is worth remembering what is at stake here. The Copenhagen conference is reckoned by many to be pretty much the last chance the world has to begin to cut greenhouse gas emissions before catastrophic climate change becomes inevitable.

To follow our journey stay tuned to this blog and follow my updates on Twitter.

Mr de Boer told the newspaper that the Copenhagen climate change conference will not produce a new international treaty to replace the Kyoto treaty.

Since that is precisely what the Copenhagen conference was intended to do this is a significant admission from the man whose job it is to bring December's negotiations to a successful conclusion.

"A fully fledged new international treaty under the [UN framework] convention [on climate change] - I do not think that will happen." He said. "If you look at the limited amount of time remaining to Copenhagen, it's clear."

So where does that leave the negotiations?

The truth is that Mr de Boer is just expressing what has become clear to most observers of these complex talks.

Managing expectations

The original ambition for the Copenhagen conference was to put in place a legal architecture for enforcing an international agreement on emissions reductions.

That is what the Kyoto treaty did in 1997. It expires in 2012 and the idea was that Copenhagen would draw up its replacement.

But it has become increasingly clear over recent months that the world is just not ready to sign up to a sweeping accord of this nature.

Mr de Boer's interview is designed to scale back expectations.

The need now, he said, is to "concentrate on the political imperatives that make it clear how countries are committed [to tackling climate change] and engaging in cutting emissions, and what co-operative mechanisms they need to put in place".

What that means in practice is that he will be happy if the UN comes away from Copenhagen with a series of commitments from individual countries about how they intend to cut or stabilise their emissions.

These commitments will only have force in national law.

The UN has not given up on the goal of a legally binding international agreement, however.

Mr de Boer told the FT that he wants to see a decision on a long-term target for emissions cuts.

He wants ministers to "decide a deadline by which that architecture can be negotiated into something comprehensive".

High stakes

Nevertheless, what is clear from the interview is that what is agreed at Copenhagen is likely to fall so far short of original expectations.

Let's not forget what is at stake here. The Copenhagen conference is reckoned by many to be pretty much the last chance the world has to begin to cut greenhouse gas emissions before catastrophic climate change becomes inevitable.

So how is it that a deal has been derailed before the world's environment ministers have even sat down at the table?

I hope I will be able to find some answers to that question over the next couple of weeks because the Ethical Man team is returning to the United States.

In the last weeks before the Copenhagen conference begins we will be exploring the role the world's most powerful nation has played in the run up to the talks and asking if the US is responsible for the likely failure of negotiations.

Sign up here to follow our journey or sign up to my Twitter account for regular posts on our travels.

There is growing evidence that people now "get" climate change. They understand what the term means, believe it is happening and that man's activities are one cause. That's an important result for the green movement but, with respect, that's the easy bit - it doesn't cost anything to change your mind.

The difficult work starts now. If we are going to meet the targets for carbon cuts which scientists say are necessary then we need to get people to change their behaviour and begin to reduce their carbon footprints.

Here the record is much poorer. It seems people simply do not want to give up their high carbon lifestyles. Just look at the findings of Loughborough University's work on flying. Fewer than one in five people said they would be willing to cut the number of flights they take for environmental reasons.

Some critics say the Green message of self-denial and sacrifice has put people off. There may be an element of the problem but - as I discovered in my year as Ethical Man - the fact is cutting carbon emissions does mean sacrifice, it does mean doing less of things that most people like doing - flying, driving, heating your home.

So how can we find ways to persuade people to change their behaviour? Most economists believe the most powerful instrument for changing behaviour is the market. They argue we need a system to put a price on greenhouse gases that reflects the damage they do to the environment.

Economists say we need some system of "carbon pricing".

Yet many Greens are profoundly sceptical of market solutions. This year protesters from Climate Camp picketed the London Carbon Exchange in an attempt to shut it down.

There's a good reason for the green antipathy to markets. Greens argue that market capitalism is based on growth and a finite planet cannot sustain continuous growth. Check out the New Economics Foundation's work on the subject.

These arguments lead Greens to say that we need to smash capitalism - or at least radically change its priorities - if we are to successfully tackle climate change.

It is not a policy that is likely to engage most mainstream politicians - or for that matter - ordinary people. What is more, spurning market solutions means ignoring one of the most powerful mechanisms for changing behaviour ever developed.

Just as with technology it seems the Greens are being ideological and impractical in the face of the global emergency of climate change.

We are told carbon emissions have to peak by around 2015 if we are to stay within the crucial 2C temperature rise after which scientists say global warming could become uncontrolled.

With just six years left, surely we should use all the weapons in our armoury to get change.

There is no doubt that the green movement has been instrumental in raising the profile of the climate issue. But, having moved green issues into the political mainstream, can the green movement offer solutions to global warming?

No, says David King, Britain's former chief scientist. He says if we want to move to a low carbon economy we are going have to - as he puts it - "use every tool in the box". But the green movement rules out quite a few of the most promising tools.

Take the question of how we are going to generate power. The green solution is renewable technologies - wind, solar and wave power.

No-one questions the need for these technologies to be part of the mix. But here's a checklist of other leading low carbon technologies: nuclear power, genetic engineering, nano-technology, carbon capture and storage.

Each one offers the potential for revolutionary new ways of generating power yet many greens oppose all of them. Quite a number say even research into these technologies is wrong.

So why do Greens take such a radical position? The reason is that most Greens are profoundly risk averse when it comes to technology. That should be no surprise. The key preoccupation for most Greens is the conservation of nature. That can make them very - well - conservative.

A key strand of green thought is the "precautionary principle". That's the idea that if you can't predict what all the risks of a new technology are then it is probably best not to use it.

Sounds like good sense, doesn't it? But don't forget how urgent the climate issue is. The green consensus is that carbon emissions have to peak by around 2015 if we are to stay within the crucial 2 degree temperature rise after which global warming could become uncontrolled.

That gives us just six years.

My question for the Greens is this: if time is so short surely we are going to have to take a few risks.

Watching our film it is easy to forget just how private and closed Amish communities usually are. Many Amish refuse to be photographed, let alone filmed for television, so it was a real privilege to be invited to stay and work on an Amish farm.

In keeping with the Ethical Man ethos we were travelling by train from Washington DC down to Texas. And, if you want a non-ethical argument for taking the train rather than a plane, this trip is it.

As the train drew out of Washington station we discovered that the actress and eco-activist Daryl Hannah was sharing our carriage. She, very kindly, agreed to be interviewed for our programme.

The Amish boarded when we changed trains at Chicago. The producer and I couldn't believe our luck. Are there two more extreme examples of the American experience than a Hollywood star and the Amish?

Since you are wondering train travel is permitted in Amish communities. They are just not allowed to actually drive trains - or cars.

I asked them what they were playing and they invited me to join their game. In the end Elam and I ended up chatting into the night. The next morning - completely unprompted - he and Rachel separately invited us to stay.

It would have been rude not to.

And what a fascinating couple of days it was. Even though - as our film shows - the Amish community is becoming much more open it is still a remarkable and unique part of American life.

They did make me work hard though. Feeding and watering 79 horses was even more effort than cleaning up the mess I made a week earlier at the Vegas pig farm.

I suppose it is evidence of just how much work living a low impact lifestyle can be. Elam told me that lots of people say they want to join the Amish and some even spend time living amongst them, but almost all give up.

"A lot of people that didn't grow up with it couldn't live this way. If they had been born and raised like we were they could live with it," he told me.

"The hardest thing is what causes global warming, the vehicle" Elam believes. "They can't put that vehicle away, the television away and electricity away and live an old-fashioned life."

The fact that the Amish are finding it hard to sustain their traditional lifestyles gives a sense of the challenge we all face. The ease of energy-intensive lifestyles is clearly hard to resist.