Page last updated at 10:42 GMT, Wednesday, 4 March 2009

Big problems need big solutions

Tim Lenton
Tim Lenton

Ploughing biochar into the soil could help farmers and store carbon

Climate change is a massive problem that needs big and bold solutions, says Professor Tim Lenton. In this week's Green Room, he outlines the reasons why "geo-engineering" projects, such as reflecting sunlight back into space, could help win the battle against dangerous climate change.

The climate is undoubtedly changing, and it is changing faster than many scientists thought it would, especially in the Arctic.

Regardless of the ineffectual Kyoto Protocol, carbon dioxide emissions from human activities increased by 3% per year during 2000-2006.

Even if we can globally get our act together and reduce CO2 emissions by 80% by 2050, we are still heading for at least a 2C (3.6F) warmer world.

Artist's impression of space sunshield. Image: SPL
Who today is willing to commit future generations to collectively controlling the planetary thermostat?

This may be too much for elements of the climate system, including the Arctic sea ice and Greenland ice sheet, which could pass a tipping point on the way there.

The resulting climate change may well be "dangerous"; and if so, mitigation alone cannot avoid it.

But reducing CO2 emissions is not the only way. There are two "geo-engineering" approaches that could complement it: reflecting more sunlight back to space, or actively removing CO2 from the atmosphere.

Both aim to cool the planet; but one tackles the symptoms (higher temperatures) while the other, like mitigation, addresses the underlying cause (elevated CO2 concentrations).

But do these approaches really offer a silver bullet to solve the climate problem?

From mirrors in space to reflective roofs on our homes, reducing the amount of sunlight the Earth absorbs could counteract (to varying degrees) the extra heat radiation trapped by the increasing greenhouse effect.

For a given option, the strength of the cooling effect is determined by the change in reflectivity applied, the area it is applied over, and the altitude of application.


Among the most potent options is injecting tiny sulphur particles into the stratosphere to scatter more sunlight.

In principle, this could counteract the projected warming resulting from the future concentrations of atmospheric CO2 up to at least twice the pre-industrial level.

Volcanic eruption
Volcanoes show us what impacts some schemes might have

Such options might be developed within decades, and if they are deployed, their cooling effect would be very fast acting.

However, the cooling effect will also be short-lived, so if activities start on a global scale (which is necessary for them to be effective), there will need to be a commitment to maintain them for many centuries.

Stopping the activity would result in dangerously rapid climate warming, far worse than the steadier warming they were designed to counteract.

In effect, such technologies imply an unprecedented duration and level of international co-operation to maintain them.

Who today is willing to commit future generations to collectively controlling the planetary thermostat?

There are also undesirable side effects of this kind of medicine.

We know from past volcanic eruptions that reducing incoming sunlight weakens the water cycle, promoting drought in regions including India and the Sahel in northern Africa.

Growing attraction

So, what about the other geo-engineering approach?

There is no simple silver bullet among the geo-engineering options, but some could make an invaluable contribution

From planting trees or fertilising the ocean to chemical "scrubbing", there are several ways of creating carbon "sinks" to remove CO2 from the air.

In general, these options act more slowly and progressively than those that reflect sunlight.

CO2 removal activity has to be ramped up and maintained for several decades (and in some cases centuries) for it to have a significant effect on atmospheric CO2 and climate.

For it to be truly effective, the carbon must be transferred to a long-lived reservoir such as charcoal in soil, or geological storage for liquid CO2.

The proposals vary greatly in their potential effectiveness, which of course also depends on the area or scale of application.

Perhaps the most potent option, on the century timescale at least, is to grow plants to get CO2 out of the air and then convert their biomass to both charcoal and (bio)fuels.

BBC Green Room logo

The charcoal would be added to soil as "biochar" and the fuels used for combustion, but ideally with capture of the CO2 and transfer to geological reserves.

The attraction of such an approach is that it produces energy and heat as well as agricultural benefits, and might (according to some estimates) generate revenue.

Most, if not all, other geo-engineering schemes will cost money and thus rely on willingness to pay.

The climate side-effects of creating carbon sinks are generally less than for sunlight reflection options, but the socio-economic side effects may be considerable.

Follow the money

So where do we go next? Many fear that even discussing geo-engineering options undermines mitigation efforts.

But mitigation alone may not be able to avoid dangerous climate change, so we must consider what other activities could complement it.

There is no simple silver bullet among the geo-engineering options, but some could make an invaluable contribution.

Planktonic alga (SPL)
Adding iron to sea water could stimulate the growth of algae

Potent and rapidly deployable sunlight reflection options could be held in reserve as an emergency response should we get some early warning of approaching tipping points.

The creation of significant CO2 sinks is just as valid as reducing the sources of the greenhouse gas, because the atmosphere cannot tell the difference.

Together, they give the best chance to stabilise atmospheric CO2 and ultimately reduce it.

But economic assessment of the various geo-engineering options is badly needed, because cost will likely determine which, if any, are deployed.

Ultimately climate change is a problem of risk management. There is already a substantial risk of dangerous impacts, even if we do start meaningful global mitigation of CO2 emissions.

Given this context we must weigh up the balance of risks of using, or not using, geo-engineering.

Professor Tim Lenton is an Earth system scientist based in the School of Environmental Sciences, University of East Anglia, Norwich, UK

The Green Room is a series of opinion articles on environmental topics running weekly on the BBC News website

Do you agree with Professor Tim Lenton? Can geo-engineering help us prevent dangerous climate change? Do big problems need big solutions? Or will large scale projects run the risk of doing more harm than good?

Whilst there is little doubt that we have global warming and that it is a real issue. It seems to me that this is a huge available energy source that could be converted to a more useful product.

We have heat pumps that convert the heat into cool air, I'm sure we could come up with other more effective and efficient uses?
Chris, Weston, USA

My only logical contribution or possible solution would be to have world wide tree planting days every year. This should be able to eventually sink the co2. Who could possibly object? These trees could be managed or looked after by anyone who actually cares. Someone else can choose the dates and do something positive about it all instead of not agreeing on a simple plan, lets try most of 'spring' to start as a date.
M. Weeks, worcestershire uk

I think the problem with these solutions is that they will probably take many, many years to implement, and governements would be reluctant to pay the large amounts involved. In the meantime, the CO2 levels would keep increasing.

What is needed is to change people's mindset so that as many people as possible start to act now. Most people can reduce their carbon footprints quite easily, with little effort or cost (in fact, they would probably end up saving money). For instance, the Green Saving Expert website has lots of tips and ideas on how to reduce energy usage that anyone can follow. People Power can start helping to make a difference today, without having to wait for the slow juggernaut of bureaucracy to make a decision.
Philip Cooper, Felixstowe, UK

How about addressing the issue of where the CO2 is coming from? Mirrors in space seems a little far fetched. Reduce fosil fuel generation with solar arrays in the desert, wind farms across europe and a healthy supply of nuclear generation. We could fire nuclear waste into the sun or the outer reaches of the solar system easier than building giant mirrors in space. We could also bury it.

The majority of future power generation will be from nuclear fuel.
Mike Searle, Herne Bay

As a result of the law of unintended consequences, technological fixes worry me silly. We interfere with natural systems at our peril.

The problem is that those with the power and influence to create the necessary culture change have a vested interest in the status quo -- because they've done so well out of it.

Shortly the solutions will be thrust upon us. As we come out of this recession/depression the rocketing price of fossil fuels will return, forcing change. I hope the current events have made people stop to think about what really matters, and it's not too late.

Me? I've bought up unproductive farmland in the South West, and started planting trees -- 100 acres to date. I'm getting ready for a new world order. Only the very foolish (and the very rich and powerful)think we can carry on trashing our planet.
JR Woodman, Devon, UK

I'm sure geo-engineering would help if used in an internationally coordinated way, but its not going to matter if the number of human's on this planet continues to increase. The professor says the underlying cause of climate change is Carbon Dioxide in the atmosphere but you could argue that the underlying cause of the Carbon Dioxide in the atmosphere is the ever increasing human population.
Alex Betts, Slough

Well said -- Many people in the climate industry concentrate on creating a climate of fear to justify more oppression and taxes. Others earn a good living writing yet another 'binding' set of targets, which they then ignore.

Here we have an attempt at some solutions.

Personally I would like to see some 'binding agreements' on massive funding for alternatives to fossil fuels eg. 2nd generation bio-fuel, hydrogen etc. It's fossil fuels which are the big issue here and they are coming to the end of their era anyway. Even if people are not taken in by the climate of fear on clinate change, oil will not be sufficient in a few years: we need to find alternatives now.

But this basic point of people stopping the culture of hyping the problem and actually getting down to creating some solutions is well said.
John, England

As a layman, ideas such as seeding the ocean with iron to promote plankton bloom, or to introduce sulphur aerosols into the atmosphere fill me with alarm.

Having already polluted the atmosphere with so much additional CO2, it simply does not feel right to mitigate the consequences of this by yet more pollution. Surely the correct answer is to tackle the problem at source, i.e. reduce CO2 emissions on the one hand and on the other to promote such things as re-afforestation, particularly in the tropics and in marginal areas.

At least we can now make a pretty educated guess as to what problems we are likely to face in terms of future climate change and the extent to which we are committed to that change. To tinker with other mechanisms on a global scale could result in all manner of unforeseen consequences and getting it slightly wrong could lead to disaster beyond our imagination.
Richard, Montpon, France

I find this article very interesting, and your approach to the issue both pragmatic, and very well reasoned. I am however deeply concerned by discussions around injecting sulphur into our atmosphere. The Earth biosphere is such a dynamic, fragile and complex system, I cannot for a moment imagine this is a workable solution, putting aside the issues of the sustained international cooperation that would be required. I think that far more research into innovative means of removing CO2 from the atmosphere should be encouraged, however, and hope that a change in economic value systems around carbon and other ecosystem services would help drive efforts to both conserve and plant more trees - the best carbon sinks that exist, as well as encourage other innovative forms of addressing the problem. If the need can be expressed in a more tangible way, perhaps necessity can finally become the mother of invention.
Anna da Costa, Delhi, India

Large scale projects are simply not a good idea. Trying to correct human made problems with new inventions and technological solutions is what got us into this mess in the first place. Realistically, we screwed up and may just need to accept it. Earth will "suffer" for a few hundred thousand years or so, shake us off accordingly and start over. We have come to embody earths survival as "current ecological survival". We forget that every few million years the giant Reset button gets pressed. These new Tech solutions may act as a crutch for a few years but in the long run will only do more harm. Humans need to get over the God complex on a technological level and realize technology does not mean progress. If we really WANT to make a change, illegalize the use of fossil fuels, and give developing countries what they need to catch up with the new order of things. Of course that idea is about as unfeasible and criticism worthy as putting giant mirrors into orbit to deflect sunlight.
Evan Sztricsko, Vancouver Canada

I'm all for big ideas which mean I don't have to sit shivering in the dark and give up any travel beyond walking distance. There's always risk in life and big plans like these bring big risks. So far we can't even cap greenhouse gas emissions let alone decrease them by 80%+, so we have to look at more possible solutions.
Ian Nartowicz, Stockport, England

Interesting article, but I'm surprised Prof. Lenton made no mention, nor considered the effect of ocean acidification due to increased CO2. Reflecting sunlight would not address ocean acidification, this is a substatial drawback. The inability of marine oragnisms to form calcium carbonates structures in an acidic ocean has many frightening climatalogical and ecological implications. It is imperative that it be included and considered in these disscusions
Guy Hoffman, Victoria, BC, Canada

Oh dear, what twaddle, yet another 'Academic' keeping himself in a job.
Harry, Glasgow

These projects are essential along with reducing our production of greenhouse gases. One area that seems to be getting feeble attention is the idea of producing less animals for meat - which would reduce potent greenhouse gases...

Of course as long as we keep producing babies as if our planet had endless resources, we'll never truly solve this problem.
peter scargill, wark on tyne

Dangerous nonsence. The underlying assumption is that increased CO2 has caused, is causing and will continue to cause global warming. There is no real evidence that the 1975-2000 moderate warming was anything other than natural (with a SMALL man addition). Level temperatures 2000- 2007, and significant cooling since. The arctic ice effectively back to 'normal' It is NOT disappearing!! CO2 warming is based entirely upon computer simulations and ALL of them have failed to predict the current cooling. $50 billion spent in USA on Climate Change research. Result? NO hard evidence that CO2 is the 'culprit'. Propadanda which suits the politicians, research 'scientists (money) and the media.

BBC may I implore you to end this biased reporting and begin to give proper credence to alternative views. This would include that the sun is almost certainly the main driver (via ocean currents) of the Earth's climate. The sun has gone quiet/ long cycle 23/ last 30+ years of the sun's behaviour is eeriliy similar to that of the sun before the Dalton minimum (1795 - 1825) (Napoleon's retreat from Moscow and Charles Dickens childhood memories of cold & snowy winters as portayed in his novels).

BBC you can only flog a dead horse for so long.
Dr.T T Gough, Ballindalloch, Scotland

The cheapest and fastest option of reducing climate change would be to use much less fossil fuels. While I am sure that Tim Lenton plans would work I fear they cannot be done in time. They are simply a distraction and will give politicians another excuse to prevaricate on actually informing the public that thier lifestyles have to change either voluntarily or forced by climatic disasters. If we tax fossil fuels more and feed bact the tax revenues into insulation and renewable energy schemes we would significantly benefit the economy from the jobs made and oil imports reduced.
Nigel Williams, LEEk

Another load of "tripe" about anthropogenic climate change.

First - there is no proof that increasing levels of CO2 cause increased temperatur, a close examination of the Vostok data shows that CO2 levels lag temperature increase by sevaeral hundred years so it can't possibly be the cause.

Second - in the Earth's 4.5 billion year history ice ages account for less than 10% of this history so, therefore, by a factor of 9 - 1 the "normal" state of the climate is about 10C deg. warmer than at present with NO polar ice caps; so all the talk about "tipping" points is nonsense, the Earth has NEVER overheated to extinguish species at any time in the past despite sustantially higher levels of greenhouse gases in the atmosphere.

Two quotes "There are many reasons to conserve fossil fuels but climate change is not one of them" - Nigel Calder; "Forget about climate change, unless we gets to grips with the problem of overpopulation we are doomed" - Professor Abrey Manning.

So let's concentrate on the things tahat really matter.
Crowcatcher, Shropshire

What's being ignored is that these problems are systematic, which is to say symptomatic of social, political and economic systems founded upon, and motivated by ideology - as opposed to science. We use science as a tool in pursuit of ideological aims: capitalist profit and military domination, but ignore science as a rule for the conduct of our affairs. This is wrong because science is true to reality and ideology is not. Nation states are not real things - but invented by man. Money is not a real thing but an abstract representation of subjectively concieved value. Thus, acting on these fictions, realities are externalized - and global scale crises like climate/energy/overpopulation and environmental degradation occur as disparities between social reality and reality itself. Humankind must acknowledge the validity of science and act on that basis in order heal the disparity with reality created by centuries of action on the basis of fixed, false socio-political and economic!

ideologies - or else, become extinct.
Mark Black, London

Big solutions implies country's coming together to solve a common problem for the betterment of mankind, thats a good thing.

But tinkering with the climate on such a grande scale comes with the ultimate responsibility. Truth is we don't fully understand all the mechanism's and variables in the climate equation and so using a one stick solution like trying to tune in a radio chanel with a twiddly knob sounds scary. Tweak it too far the other way and we could be ice skating across the atlantic.

There may come a point where we simply have no choice but we first need to address our lifestyles and the way we live. Those things we can change fairly easily and we have all the technology and knowledge in place to do it, truth is our wonderful economic systems just don't see any value in it, yet.
Alastair, Drogheda, Ireland

Technology got us into this mess and, gosh-darnit, technology will get us out.

Why not, what have we got to lose!

Paul, Swansea, Wales

As we have found the earth's climate is an incredibly complex system geo engineering is likely to do more harm than good. It isn't as if we can carry out a controlled experiment first. We seem to want to go to extraordinary lengths to wish to continue our polluting ways instead of doing what we know is necessary. That is reducing our population and our demand for the earths resources.
doug stenson, doncaster

Man destroying and messing with natural systems and balancing feedbacks has gotten humans into this mess and Tim proposes that we can fix nature. Please dwell on your hubris, ignorance, arrogance, stupidity...........
John Forde, Galway City, Ireland

I think the examination on how much energy is wasted by shops that all the lights on through the night to act as an advertisement, when home owners are ask to turn lights off and equipment onto stand-by, why can shops leave the equivalent of 3 to 10 houses worth of lights, or even several TV's on all night?

How much of the reported 60% of energy used by home users, is actually down to businesses?
Robert Walker, Leeds

It is important to stop talking about "dangerous climate change" and use language that is relevant to the majority of people. We should be talking in terms of the collapse in agriculture throughout Africa, Asia and most of Europe by 2100, with the loss of billions of lives. That reality, for that is what it is if we carry on, should convince people to press for the switch to zero emission sources of energy - now!
Jon Fuller, Westcliff on Sea

Rather reluctantly I think we will have to engage in these types of geoengineering projects.

Given how slow human recognition of the scale of the problem has been, and how slow our responses are to climate change. I think we will have no choice but to engage in these projects. But I think there are a couple of other issues - we need to decide what the temperature should be and secondly we will have to be able to adjust it later.

It seems clear that these choices are not without costs - but we have to learn behave responsibly and accept our new levels of accountability.

Accountability not just through all aspects of society, personal, community, political and so - but rather obviously if we are to engage in saving our new societies using these types of projects, for the planet itself.

Personally I doubt that we will do it and instead billions of humans will die, liberal democracy and capitalism will probably cause more avoidable deaths than all previous human societies put together.

But ever hopeful.. this is a good place to start.
sdv, Chorleywood, UK

Surely the reason that the earth has styed in balance in the past is because of its cyclical nature. We must take part in these cycles and realise that using carbon is part of human nature, therfore we should concentrate on completing this cycle and returning the carbon to the ground. I would support managing forests with new trees grown to "suck up" carbon dioxide, cut down, used for our purposes and then returned to landfill to bio degrade rather than recycling paper. This would increase the overall amount of trees at work at anyone time.
Ben Harper, Chester, UK

The models can't even predict the present. Does anyone really believe they can predict the future. How come there are no articles on the lack of sunspots, or the ice coverage equalling 1980 this year. All we get is the 'alarmist' view.

Norm Milliard
Norm Milliard, Hampton, NH, USA

All geo-engineering projects contain great uncertainty and applying them risks compounding the many challenges facing humanity instead of alleviating them. To be effective such efforts will require great effort and international cooperation. If this effort were applied to mitigation, through for example, reducing damage to primary forests, reducing fossil fuel consumption, changing dietary habits, controlling population, etc, the effective change in CO2 levels might well be the same. Mitigation has the additional benefit that most methods result in positive 'risks' which may aid humanity, such as protecting biodiversity, reserving fossil fuels for alternative uses or alleviating poverty.
Chimed, Amsterdam

black soil and iron fertilizing are good ideas, but the 'could' mentality is killing us. Why not say we will have no envionmentally lethal products or activities from NOW on. Every uncompensated molecule of CO2 anywhere in the productive chain is one to much. Would life stop? I doubt it strongly. The choice is between having the blood of the comming climate genocide on our hands or not.
Frits Rincker, Den Haag

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