What can we do to save our planet?

Jim Lovelock, author of the Gaia theory

I never thought that the Kyoto agreement would lead to any useful cut back in greenhouse gas emissions so I am neither more nor less optimistic now about prospect of curbing CO2 compared to 10 years ago. I am, however, less optimistic now about the ability of the Earth's climate system to cope with expected increases in atmospheric carbon levels compared with 10 years ago. I disagree that geoengineering the climate is a dangerous distraction and I disagree that on no account should it ever be considered. I strongly agree that we now need a "plan B" where a geoengineering strategy is drawn up in parallel with other measures to curb CO2 emissions. However, climate change is an Earth system problem and the UN is not a suitable body to host or organise it.

Professor Chris Rapley, director of the Science Museum, London

I am not enthusiastic about geo-engineering, as to intervene on a massive scale in the Earth's climate system will certainly have unforeseen consequences, some of which could be as regrettable as the problem the intervention was designed to address in the first place. This is why Jim Lovelock and I have been encouraging thought and exploration of means to "help the Earth help itself"; i.e. by amplifying carbon sequestration processes that the Earth already practises – in the ocean and on land. I very much support the various tropical rainforest initiatives for this reason. My real concern is that the need to take action is now very urgent. Events in the Arctic suggest that we may already be passing through a significant "tipping point". The action taken in response to the credit crunch indicates the scale and speed of what is possible. Saving the ecosystem services upon which we all depend would seem to be at least as important as baling out the worldwide cartel of reckless and greedy bankers.

Professor John Shepherd, National Oceanography Centre, Southampton, and chair of Royal Society working party on geoengineering

Possible geoengineering options need to be explored, but must not be allowed to detract from efforts to reduce CO2 emissions directly.

Professor Kerry Emanuel, Massachusetts Institute of Technology, Cambridge

While a geoengineering solution is bound to be less than desirable, the probability of getting global agreement on emissions reductions before it is to late is very small.

Paul Crutzen, Nobel Laureate, Max Planck Institute for Chemistry, Mainz, Germany

I would agree with doing research to find out more about potential side effects. My answer to two of your [survey's] questions is 'don't know' as I cannot predict the future.

Professor John Latham, US National Centre for Atmospheric Research

Since CO2 levels seem certain to rise for a long time, we think it vital to examine geo-engineering schemes for stabilizing Earth's temperature for long enough to allow alternative, clean forms of energy to be developed. We are examining one scheme in collaborative research involving Universities of Manchester, Leeds, Edinburgh and (in USA) National Centre for Atmospheric Research, and Pacific Northwest National Laboratory: lead scientists at these institutions, Tom Choularton, Alan Gadian, Stephen Salter, John Latham, Phil Rasch, respectively.

Our idea is to increase the reflectivity of shallow oceanic clouds by seeding them with seawater particles to increase their droplet numbers: thereby producing global cooling. Provisional results (mainly modelling) suggest the technique could hold Earth's temperature constant for around 50 years, and that current values of Arctic ice cover could be maintained over this period. Much more work is required on technological questions and ramifications of possible deployment.

Professor Stephen Salter, school of engineering, University of Edinburgh

After many years trying to develop renewable energy I now believe that we are too late and so I am working on the engineering of John Latham's idea for enhancing cloud albedo.

Professor David Archer, Chicago University

Carbon dioxide released to the atmosphere will continue to affect climate for many millennia. Relying on geoengineering schemes such as sulphate aerosols would be analogous to putting the planet on life support. If future humanity failed to pay its 'climate bill' – a bill that we left them, thank you very much – they would bear the full brunt of climate change within a very short time.

Victor Smetacek, Alfred Wegener Institute for Polar and Marine Research, Germany

The Earth's carbon cycle, pushed way off balance by humankind, is teetering dangerously. The excess CO2 already in the atmosphere, equivalent to 200 billion tonnes of carbon - a third of the entire land vegetation - will stay for millennia and continue to shrink planetary ice stores: ways need to be devised and implemented to remove as much as possible, even while emissions add to the burden. Not considering CO2 removal now is tantamount to not bailing out water pouring into a sinking ship until the leak is stopped. In addition to sequestration on land, scientists need to explore the potential of the vast ocean volume and sea floor to take up more of the burden. This undertaking should be entrusted to peer-controlled, international academia and governmental research institutes, activated by massive R&D funds raised from carbon taxes, in lieu of the profit-oriented, carbon credit scheme favouring wanton commercialisation.

Professor Martin Parry, Imperial College London

The required cuts in greenhouse gas emissions are now so large and urgent that it seems unlikely we can avoid a global 2C warming. To achieve this would require cuts of 6% per year starting in 2010, and enabling a global cut of 80% by 2050. There is now a real danger of allowing temperature to rise beyond our capacity to adapt. Consequently, there need to be 3 parallel strategies: i) reduce emissions as much and as soon as possible, ii) prepare now for adaptation to at least 3 degrees warming, and iii) see what geo-engineering can do to close the 'damage gap' that otherwise risks being left between emissions reduction and adaptation.

Professor Corinne Le Quéré, University of East Anglia and British Antarctic Survey

I think that geoengineering options have little if any potential on the time scale in which actions are needed to stabilise atmospheric CO2 and climate (20-30 years). To stabilise climate, we need to focus on options that can be implemented right away. Geoengineering options could be useful to address the long-term stabilisation of CO2 in the atmosphere over a time scale of one century, or to reduce atmospheric CO2 back to its pre-industrial level if we find that such a measure is needed. Thus I am not against research on this topic, but I don't think it should be viewed as a substitute for immediate action. Rather it should viewed as an additional measure to be used if the climate starts to dangerously deviate from a semi-stable trajectory.

Petr Chylek, Los Alamos National Laboratory

Geoengineering should concentrate on preventing the Greenland ice sheet from melting, not on the whole climate change. This would cut the resources needed by a factor of about 10 to 100.

Professor Stephen Schneider, Stanford University

My disagreement with item 4 [need for a plan B] is because it is too vaguely worded. I do agree with research and development, and that should include social scientific research on how any such actions might be managed by international agreements. But it can't be agreements among only a few superpowers, but essentially the whole UN establishment, since the climate is a global commons. Until such a broad-based treaty is negotiated and accepted, I think any implementation of geoengineering by private parties or a few governments should be illegal – with severe sanctions for violations.

Professor James Shulmeister, University of Canterbury, New Zealand

There is NO prospect of getting cuts in emissions of the scale needed to have a large impact on the problem. We need all the cuts we can get but we also need to engineer ourselves out of the problem. However, geoengineering on its own is NOT the solution.

Ray Weiss, Scripps Institution of Oceanography

Nearly all geoengineering proposals I have read have appeared to me to be naïve or short-sighted in one way or another. It is hard to manage something that is not very well understood, but that doesn't mean we shouldn't work on the problem. I balked at that use of the word "need", but an intelligent "Plan B" would certainly be welcome.

Caspar Ammann, National Centre for Atmospheric Research

I believe that there is no clear geoengineering option around this far that appears viable, both from an implementation and effect perspective. All options produce not enough "winners" to encourage actual benefits from a very expensive action. Much preferred would be concentrating these resources into reducing emissions (capturing carbon in particular) and increasing efficiency. While geoengineering should be studied and not banned from discussion, any related solution would have to overcome the scientific and also moral thresholds to demonstrate benefits.

Frank Zeman, Director, Centre for Metropolitan Sustainability, New York Institute of Technology

Geoengineering is not an option because it is a self perpetuating problem. That is, geoengineering cannot be done in lieu of driving CO2 emissions to zero as the result is a perpetual cycle with ever higher atmospheric CO2 levels. It may be considered as an option to alleviate climate disruptions after CO2 emissions have begun trending towards zero for short term relief.

Kevin Walsh, University of Melbourne

The fundamental problem with geoengineering is that we are already undertaking our own geoengineering experiment, namely global warming due to man-made greenhouse gas production. This current experiment has already thrown up some nasty surprises. Why should we try another experiment when it could cause additional unintended consequences? Why not try to fix the fundamental problem instead?

Tony Del Genio, NASA Goddard Institute for Space Studies, New York

At this stage it would be unfortunate to consider geoengineering to limit climate change due to increasing greenhouse gases. Simply offsetting the global radiative imbalance does not offset the consequences. The spatial patterns of geoengineering forcing and greenhouse gas forcing will not match, causing regional weather and climate changes that may not be beneficial. At this stage such solutions should not be implemented. That having been said, if society does not within a decade address the climate problem seriously and we approach a tipping point of irreversible climate change, then we need to have a last resort geoengineering strategy in hand. Thus research on geoengineering impacts, as evaluated by climate models, should be undertaken in the interim to better characterize its benefits and problems. Implementation should be only a last resort, akin to actions currently being undertaken by governments to address the financial crisis that were unthinkable months ago.

Eric Wolff, British Antarctic Survey, Cambridge

The challenge of keeping greenhouse gas concentrations to reasonable levels is so big now (because we have left it so late to act) that we have to explore everything – including energy choices many of us find unpalatable, and the possibility of geoengineering solutions. However, many of the proposed geoengineering schemes are dangerous, either because we don't know what other effects they will have, or because they assume that we will be able to service the solution forever. Furthermore the potential of many of them has been greatly oversold. I don't think a geoengineering "strategy" will help, but sensible, sceptical research on the saner ideas should be pursued.

Professor Lewis Rothstein, University of Rhode Island Graduate School of Oceanography

It would be negligent if a geoengineering strategy were not established, so long as the research were fully scrutinized as is the case for any issue of scientific discovery. The argument that the earth system is too complex to predict the outcome of any geoengineering of our environment misses the central issue of the relationship between complexity and uncertainty, and actionable science. We have little choice but to trust the combined wisdom of the climate sciences community to help determine that uncertainty, what it would take observationally and computationally to narrow that uncertainty, and what mitigation activities are appropriate given that level of uncertainty and the consequences of inactivity. One is never 100% certain; because there is uncertainty does not mean that the results are wrong.

Mat Collins, Met Office Hadley Centre, Exeter

Ideas like injecting large amounts of aerosol into the stratosphere and the like may have unforeseen circumstances – this risk is just too high. While we, as climate scientists, agree on the fundamentals of climate change (i.e. the world is warming and greenhouse gases are to blame) we are still working out the detail. It is unlikely that there would be enough of a scientific consensus on the consequences and side-effects of any geoengineering options for us to be confident of their viability for many years, possibly decades. The exception is carbon capture and storage, which looks like a winner to me.

Andrew Yool, US National Centre for Atmospheric Research, Boulder, Colorado

Just as we shouldn't rule geoengineering out of hand, we shouldn't uncritically accept it as a component of efforts to combat climate change. Schemes should be assessed for efficacy, side-effects and verifiability both in small-scale field trials and by modelling studies before they are applied in large-scale operations. Modelling is particularly important since it allows us to both estimate global-scale and long-term efficacy/consequences, and to explore "what-if" questions such as "what are the consequences if we need to suddenly stop geoengineering?" Although verifiability is infrequently addressed, it's important for commercial reasons that success is properly attributed to schemes. Geoengineering is potentially extremely lucrative and, in marine biology at least, has already attracted questionable schemes, so it's crucial that unsuccessful ones are identified to avoid wasted effort. More generally, on biodiversity grounds, we should be wary of co-opting even more of the Earth's biological productivity just to clean up after ourselves.

Richard Lampitt, National Oceanography Centre, Southampton

There are several options available but at present the crucial issue is to gain the scientific insights so that appropriate decisions can be made in a rational manner. The efficacy of the various schemes needs to be assessed along with a careful analysis of the unintended consequences which might also occur. A cost-benefit-risk analysis must then be completed before the issue of commercial deployment is considered.

Roger Gifford, CSIRO Plant Industry, Australia

It is not a question of whether the climate system copes with increased greenhouse gas levels. It will cope by changing. The question is whether human organisation and well-being will cope from the manner in which climate responds.

Geo-engineering needs defining. It can include enhancing terrestrial C stocks by land fertilisation and land use change, as well as enhancing marine C stocks by ocean fertilisation, geosequestration by pumping liquid CO2 below ground, or global-scale purposeful atmospheric modification by releasing aerosols, or radiation modification by orbiting sunshades. It is my view that just as we cannot be sure exactly how the earth system will respond to continued global modification of atmospheric content of greenhouse gases, we also cannot be sure how it will respond to global modification of the aerosol content and radiation balance. Because the earth system is not amenable to controlled replicated experiments, we will never be sure enough to justify any such major global-scale attempts at amelioration to justify any one group of people imposing such change on everybody.

Professor Meric Srokosz, National Oceanography Centre, Southampton

The problem with talking about geo-engineering solutions to climate change is that realistically they are never going to solve the problem. They might be part (probably a small part) of the solution but fundamentally we need to cut greenhouse gas emissions.

The other issue is the risk (largely unknown) of the impact of the geo-engineering solutions. In trying to "fix" one problem you may create a worse one (law of unintended consequences).While I am happy with the thought that we should investigate geoengineering solutions to better understand their feasibility, costs and associated risks, there is a danger that people will think that they do not need to change their behaviour because there is a technological "fix" round the corner. This is a socio-political (or psychological) rather than science / engineering issue.

Kevin Trenberth, US National Centre for Atmospheric Research, Boulder, Colorado

Who makes the decision on behalf of all humanity and other residents of planet earth to change the climate deliberately?

Climate change is not necessarily bad. The climate has always varied to some degree, and changes have occurred over decades and millennia. Humans and other creatures have evolved and adapted to the changes, or perished. It is a part of evolution. Changes projected with increased greenhouse gases in the atmosphere may have some aspects that could be regarded as bad: increased heat waves and wild fires in summer, increased and more intense droughts, heavier rains and risk of flooding, stronger storms and hurricanes, decreases in air quality, increases in bugs and disease, and so on, are all likely threats. But in some areas climates improve, high latitude continents become more equable, growing seasons are longer, and so on.

There are winners and losers and it is possible to adapt to such changes – at least if the changes occur slowly enough to allow this to happen. In other words, a key issue is the rate of change, perhaps more so than the nature of the change? This obviously also depends of how long such changes continue for. In that sense, it is the "change" part of climate change that might be argued as being bad.

But given that there is no universal condemnation of the climate change, how can anyone justify deliberately acting to change the climate to benefit some group, and perhaps even a majority? It is argued here that the ethical questions arising from this loom so large that some forms of geo-engineering are simply unacceptable. The forms that are acceptable include those that reduce emissions and mitigate the rates of change, or reduce the amount of carbon dioxide in the atmosphere. Forms that propose to block the sun in some fashion, perhaps to emulate a volcanic eruption, change the hydrological cycle and weather patterns in ways that would be simply unacceptable, even if they were doable. The cost of any such proposals and their viability are other major issues, but, in my view, they are overwhelmed by the ethical considerations.

Nick Brooks, visiting research fellow, Tyndall Centre for Climate Change Research

It is almost certain that we will fail to stop the globe warming by more than 2C, and probably more than 3C. All potential options for addressing climate change risks should therefore be considered. However, it would be foolish to focus on geoengineering options as a substitute for reducing greenhouse gas emissions. Geoengineering solutions do not help us avoid changes in the behaviour of the global climate system, but simply replace one kind of interference with another. While geoengineering may help reduce warming at the global level, it may still cause changes in atmospheric and oceanic circulation, particularly if it is targeted at certain regions or certain internal climatic mechanisms. Geoengineering also raises difficult ethical issues. For example, a geoengineering solution may reduce warming while resulting in regional changes in climate that adversely affect some parts of the world. Countries likely to suffer most from global warming may lobby for engineering solutions with adverse impacts on other countries. In the end, agreement over engineering solutions may be as difficult to achieve as agreement of emissions reduction targets. Mitigation of climate change through large and rapid reductions in greenhouse gas emissions remains the most reliable way of confronting anthropogenic climate change.

Tao Wang, Tyndall Centre and Sussex Energy Group

The definition around geoengineering is very ambiguous at this moment so it is difficult to have an overall assessment to the various options that were discussed. Large scale geoengineering only aims at carbon reduction are very dangerous as it could introduce irreversible and catastrophic consequences to the natural system that we won't be able to foresee. It is also against the precautionary principle.

This would offer a false shelter to encourage people carry on with business as usual and weaken the will of commitment for sharp carbon emission reduction that we really need.It risks making the climate change agenda override others such as sustainable development, biodiversity conservation, water resource scarcity management, etc.

David Schnare, director of the Centre for Environmental Stewardship, Thomas Jefferson Institute for Public Policy

Geoengineering is inevitable if we observe unimpeachable evidence of catastrophic climate change, since it has been determined that it is very likely to be effective and is virtually costless in comparison with either the cost of suffering catastrophic climate impacts of the cost of massive carbon reduction efforts. In light of that, we should begin field testing of obvious candidates.The largest amount of research effort, however, should go into planetary scale carbon sequestration, to include both air capture and ocean water extraction - both now promising research opportunities.

Debora Iglesias-Rodriguez, National Oceanography Centre, Southampton

I believe much research testing ecological and biogeochemical consequences must take place in pilot small-scale studies as well as measurements of the actual carbon sequestration under different manipulations before society can embark on large initiatives.

Steve Siems, Monash University

I believe it is a dangerous distraction filled with many potential hazards. But I hate to say never under the circumstances. If it is a plan B, we need to try Plan A over and over and over again before even contemplating Plan B.

Anand Gnanadesikan, US National Oceanic and Atmospheric Administration

Categorically rejecting geoengineering corresponds to holding that we must maintain a particular climate (that of the early 20th century). Such a preservationist view is emotionally attractive but isn't particularly scientifically justifiable- climates have changed a lot in the past. On the other hand, commercial boosters of geoengineering schemes often fail to build in the uncertainties in how the impacts of such schemes would be measured, whether they would trigger negative consequences or indeed whether they would work at all given feedbacks in the climate system. We need a more rational way of choosing between our options.

Gabriele Hegerl, University of Edinburgh

My personal opinion is all options need to be considered carefully. No geoengineering solution I am aware of (maybe apart from carbon capture and storage) is free from risks and side effects. An example is the idea of injecting aerosols into the stratosphere – these, in combination with greenhouse gases, may impact rainfall in a way we cannot reliably predict at present. Given the poorly understood risks it is too early for a geoengineering strategy, but careful research into the benefits and risks of individual geoengineering options may be a good idea.

Andrew Gettelman, US National Centre for Atmospheric Research

Geoengineering is a distraction. It is also dangerous. Agreeing that we should consider geo-engineering is tacit admission that we really do need to do something more significant about carbon emissions. It is also tacit admission that if you trust simulations of geo-engineering effects you also should trust simulations of future climate impacts.

However, there may be cases where we might consider it in the context of a general CO2 reduction strategy to avoid severe impacts temporarily (e.g.: prevent loss of the Greenland ice sheet and catastrophic sea level rise).

I do not think geo-engineering will be necessary. I do not think that it should be 'part' of a mitigation strategy except in extreme cases. That means: getting 'carbon credit' for geo-engineering should not be part of a CO2 reduction strategy. I do not see a problem in continuing research into geo-engineering. It complements research into other aspects of the climate system and how it might change.

Steven Sherwood, Yale University, New Haven, Connecticut

At the present time, I do not know of any geoengineering strategy that I feel would ever be worth implementing. For example, the most popular idea (creation of stratospheric aerosols) would render us susceptible to a devastating climate whiplash if the program were ever halted. However, as a matter of principle I believe that such strategies should be carefully studied, their merits and defects weighed and discussed, and better alternatives sought. International agreements on how to decide on geoengineering need to be put in place before such actions are seriously contemplated, rather than after."

Neil Wells, National Oceanography Centre, Southampton

Ten years ago I was confident that we could globally control carbon dioxide. Since then I have seen evidence that the climate models are under-estimating the change in sea ice in the Arctic – changing faster than Hadley Centre's HADCM3 model predicted a few years ago.

Secondly, that it is one thing to persuade one country of the need to do something, but persuading the world is going to far more difficult.

Anthony Patt, International Institute for Applied Systems Analysis

Geoengineering only solves some of the problems of climate change (e.g. arctic sea ice loss), but not others (e.g. ocean acidification, reduced diurnal and annual temperature cycle), and so it can never replace complete decarbonisation, but only complement it. With that in mind, it is an option to be considered, in parallel with other adaptation options.

With respect to a treaty to reduce carbon dioxide emissions, we must be open to the possibility that international negotiations will likely fail to stipulate the necessary emissions cuts. At the same time, subsidized investments in particular technologies (off-shore wind, concentrating solar power, combined with electrification of transport) could, if pursued aggressively by the US and EU over the next 10 – 15 years, push the costs for these technologies down to levels below that of coal, gas, and oil, making a global treaty unnecessary. (Indeed, this is why I am more optimistic now than 10 years ago about achieving the necessary emissions reductions).

Steven Ghan, Pacific Northwest National Laboratory

Any geoengineering solution should focus on removing CO2. Any other solution is bound to introduce changes in the distribution of radiative heating that would change the climate in undesirable and perhaps unexpected ways.

LuAnne Thompson, School of Oceanography, University of Washington

We are rolling the dice in a very dangerous way by assuming that we can introduce modification to alleviate problems that human kind has introduced to our environment. While in total, we have good predictions for the globally averaged changes expected from the increase of greenhouse gases in the atmosphere, we still have great difficulty in predicted local and regional changes. Determining whether a geoengineering solution would introduce mitigating changes in the weather is hubris. In addition, geoengineering solutions do nothing for the increasing pH in the ocean caused by the uptake of carbon dioxide by sea-water. If we choose to go the route of geoengineering, we are destining our children with a vastly changed ocean ecosystem. This will inevitably lead to a collapse of the remaining wild fisheries. In addition, the ocean's ecosystem takes up carbon dioxide. By destroying the ocean's ecosystem we will likely be introducing an addition source of carbon dioxide that would also need to be mitigated. Geoengineering is just not acceptable. The costs are far too high.

Boris Kelly-Gerreyn, National Oceanography Centre, Southampton

Geoengineering offers very limited hope in avoiding dangerous climate change. The main focus of effort must be to reduce global greenhouse gas emissions, now. No other option gives us a realistic hope. Hence, it is crucial that public attention is not diverted from the urgent action necessary to achieve a contraction of CO2 emissions. Furthermore, because CO2 stays in the atmosphere for many 100s of years, this reduction must tackle our cumulative emissions (emissions today add to those of yesterday and to those of tomorrow) rather than some distant CO2 reductions target date. Hence, emission reduction pathways must enter any global agreement. Technological fixes like geoengineering require many years of research to understand their effectiveness in tackling the most important issue the human race has ever had to face, years that delay what must be really done.

Alan Robock, Rutgers University, New Jersey

We need to do research on geoengineering to find out its costs, efficacy, and problems. We need to study how to engineer delivery systems and the timing, amount, and location of sulfur injection into the stratosphere. Only then will we be able to evaluate whether it is a good idea or not to engage in temporary geoengineering.

Based on what I know right now, geoengineering is not a good idea. Its possibility will reduce public will toward mitigation. There are still governance issues and how it could affect the Asian monsoon and ozone, make skies less blue, but give us red sunsets, and provide less solar radiation for solar power, especially systems requiring direct solar radiation. In addition, it may be perceived that geoengineering technology could be used for military purposes. I am also concerned about commercial control of the technology.

Frank Schwing, National Atmospheric and Oceanic Administration, US Department of Commerce

I am more optimistic about global reduction efforts because the new Obama Administration in the US is poised to be a world leader in this effort, and because the public groundswell for such an effort is growing rapidly. Regarding geoengineering, we clearly will need some concerted and effective efforts to engineer our way to reduced greenhouse gas levels. However, I am concerned that the public, and governments, will see such efforts as a panacea, thereby eliminating the need for public action to reduce emissions.

Albert Kallio, Frozen Isthmuses' Protection Campaign of the Arctic and North Atlantic Oceans

There is much unnecessary fears in geo-engineering. It is true that it is no proper substitute for cutting down emissions and then reversing the damage, especially by re-planting forest cover that has been mowed down over the last few decades.

In principle, the carbon trading, mitigation, adaptation, and geo-engineering are at parity with each other. None of these schemes will work unless the infinite rise of CO2 and other greenhouse gases are curbed. The extension of road is short with geo-engineering.

Many geo-engineering schemes such as space shades may work, but they are uneconomic. Others represent vaguely understood technologies that probably fail to deliver or will remain as elusive solutions to as the fusion energy. The chemical acidification from CO2 cannot be helped by chemicals without even more pollution.

Cleanest efforts being mechanical procedures such as redirection of Siberian rivers, breaking and scattering sea ice, and various other forms.