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'It's likely we'll have to reduce greenhouse gases'
DR MYLES ALLEN
Head of the climate dynamics group at Oxford University's physics department
THERE is no evidence that we have passed any tipping point already.
That said, today's levels of greenhouse gases could already be dangerously high if we kept them at today's level.
But, on the other hand, as the climate changes we'll learn more about the impact and be in a position to do something about it.
I think it is likely that we'll have to reduce greenhouse gases below today's level, in the very long term it is likely to be necessary to do that.
But, if we move beyond fossil fuels, that will eventually happen: we are not doomed to emit greenhouse gases forever.
There's a lot of confusion about whether greenhouse gas levels going above a certain level might result in a dangerous level of warming and if that is "a point of no return".
Of course, it isn't. We could raise carbon dioxide levels to 600 parts per million and we'd have a very dry year, but, providing we brought them down again, as far as temperature is concerned, you would barely notice it.
There's no magic about greenhouse gas levels going above a certain level. It's the amount of time they spend beyond a certain level that is important.
However, if it was to happen on a large scale - and there are worrying trends in methane - that's the sort of thing that could cause problems.
If the Arctic was to start releasing vast amounts of methane, that would be a concern, but, at the same time, methane has a relatively short lifetime. It wouldn't necessarily be a planet-destroying event.
I am less worried by the prospect [of James Lovelock's forecast of billions of deaths by the year 2100] than the prospect of us leaving it so late to do something about climate change that, when we eventually do do something about it, it has to be incredibly traumatic and results in a lot of people suffering completely unnecessarily because we have to turn the world economy around in a hurry when we could have done it in a reasonably calm and orderly manner now.
That said, people will be killed by climate change this century. I'd be reasonably confident in that statement.
Arguably, this has started already with the 2003 heatwave in Europe which killed 20,000 to 35,000 people, including 4,000 people in the UK.
'This is meant as a wake-up call'
PROFESSOR JOHN SCHELLNHUBER
Director of the Potsdam Institute for Climate Change Research
I KNOW James Lovelock and respect him tremendously. He's been one of the most influential scientists on the environment for many years now.
Everything he's writing has to be taken very seriously. It's not just some 'Doomsday' prediction.
I think this is really meant as a wake-up call - among the many scenarios about the future of the planet. If we do not really fight global warming, then this is certainly in the upper range of catastrophe, the worst-case scenario.
The probability of the scenario is pretty low, but it cannot be completely ruled out.
Many human lives are at stake if we don't do anything about global warming.
If there was five or six degrees Celsius of warming over the century, that would be a different world.
It is a very extreme scenario he is using, but we are at least on the road towards disaster.
'We have maybe got 20 years'
PROFESSOR JAMES CURRAN
Head of environmental strategy, Scottish Environmental Protection Agency (SEPA)
I'M not as pessimistic as James Lovelock, but I have been sounding these kind of warnings for a few years now.
My own view is we have maybe got 20 years to make drastic cuts to our carbon emissions before the feedback effect on global warming becomes sufficiently strong that it gets out of control.
There are certain global carbon cycles that run the risk of increasing carbon dioxide emissions because of climate change. And one such cycle close to home is that we have enormous peat deposits in Scotland: we have 5,000 million tons of carbon in our peat deposits.
We have peat because we have a cold, wet climate. But, under climate change, Scotland is going to get warmer and drier. The peat begins to crack and air gets inside. In winter, when climate change is going to bring rainstorms, the rain begins to erode the peat and the structure starts to collapse.
There is evidence this is happening and it would only take 0.4 per cent of that peat to erode each year and be released into the atmosphere to double Scotland's total carbon emissions.
'The "tipping point" is probably around 2025'
IT'S too early to start saying 'It's too late...' but it's only just too early.
I am currently working on a book on how we could cut carbon emissions by 90 per cent by 2030.
It is just within the realms of possibility that we could do that. I think that is what we have to do to avoid increasing temperatures by two degrees Celsius above pre-industrial levels [1.3 or 1.4 degrees more than current levels] that would trigger off ecosystem collapses such as the Amazon drying out and releasing its carbon.
That would take you to three degrees, triggering a further collapse that gets you to four or five degrees.
The most painful things we have to do to reduce carbon emissions by 90 per cent include:
• A complete moratorium on further flights and a great reduction in the number of current flights.
• Much tougher building regulations every time we refurbish our houses, making energy-efficient lights and stuff like that part of the building regulations. It's hopeless leaving it all to the market.
• And to start to go up to using the maximum wind resources [for electricity] we can put on the national grid, which is probably about 30 per cent. That could be done very quickly.
The "tipping point" is probably around 2025, but it could happen earlier than that, it depends on feedback responses - there are a lot of unknowns here.
Just last year there was a new study saying British soil has become a source of carbon. Things can happen very quickly and far sooner than we are expecting.
Last year there was a big conference in Exeter and what came out of that is we have only ten years in which we can take some meaningful action.
If we do not do anything in that, we might as well forget about it. Once we get to a certain point with global warming, it's out of our hands.
'Things will get worse'
RICHARD DIXON Worldwide Fund for Nature (WWF), Scotland
IT'S helpful every so often to have a 'Cassandra' who sounds a really extreme warning.
It contributes to the debate about how far climate change will go and how bad it will get. If Lovelock is right and we are too late, then we are in deep trouble. But the middle-ground predictions say it is not too late. Things will get worse, but we can stop it at a stage where human life is still possible, human society continues to exist and life isn't too bad. That's the view most environmental groups take.
There are many people who say this is very, very urgent and we really need to act in 20, ten or five years. I've heard people saying we might be beyond the point of no return. Lovelock could be right, but let's hope not.
There are a series of crucial systems that support life as it is at the moment and if they go wrong they will start very serious changes.
For Scotland, the chief one is the circulation of the oceans. If the Gulf Stream was to shut off, that would reduce the temperature by about 10 per cent.
'It is bad news as it stands'
DR DAVID VINER
Senior research scientist, Climatic Research Unit, University of East Anglia
CLIMATE change poses a big threat. I think Professor Lovelock is over-cooking it slightly, but even if you look at the scientific consensus, the rate of warming is going to cause significant problems. It's bad news as it stands and it is going to cause major problems.
We may get a runaway greenhouse effect, but, at the moment, we just don't know. It would be unwise for governments to throw in the towel now.
We do need to make sure we reduce carbon dioxide emissions. We have a responsibility to stabilise greenhouse gases in the atmosphere and, in the very long term, reduce them.
The scientific community have been telling the government to wake up to this for a while.
We may instigate feedback responses [in the environment] that may enhance the warming, but I'm not a big advocate of the Gulf Stream switching off. That will take a lot more warming than is probably happening. That's way over the top.