Climate engineering

From Wikipedia, the free encyclopedia

An oceanic phytoplankton bloom in the South Atlantic Ocean, off the coast of Argentina. The aim of ocean iron fertilization in theory is to increase such blooms by adding some iron, which would then draw carbon from the atmosphere and fix it on the seabed.

Climate engineering, also referred to as geoengineering, is the deliberate and large-scale intervention in the Earth’s climatic system with the aim of reducing global warming.^[1][2][3] Climate engineering has two categories of technologies- carbon dioxide removal and solar radiation management. Carbon dioxide removal addresses a cause of climate change by removing one of the greenhouse gases from the atmosphere. Solar radiation management attempts to offset effects of greenhouse gases by causing the Earth to absorb less solar radiation.

Geoengineering has been proposed as a potential third option for tackling global warming, alongside mitigation and adaptation.^[4] Scientists do not typically suggest geoengineering the climate as an alternative to emissions control, but rather an accompanying strategy.^[5] Reviews of geoengineering techniques for climate control have emphasised that they are not substitutes for emission controls and have identified potentially stronger and weaker schemes.^[6][7][8] The costs, benefits, and risks of many geoengineering approaches to climate change are not well understood.^[9][10]

No known large-scale climate engineering projects have taken place to date. Almost all research has consisted of computer modelling or laboratory tests, and attempts to move to real-world experimentation have proved controversial. Some limited tree planting^[11] and cool roof^[12] projects are already underway. Ocean iron fertilization has been given small-scale research trials.^[13]

Most experts and major reports advise against relying on geoengineering techniques as a simple solution to climate change, in part due to the large uncertainties over effectiveness and side effects. However most experts also argue though that the risks of such interventions must be seen in the context of risks of dangerous climate change.^[14] As a rule of thumb it would appear that the scale of risks and costs of each climate engineering option appear to be somewhat inverse: The lower the costs, the greater the risks.^{[14][unbalanced opinion]} Some have suggested that the concept of geoengineering the climate presents a moral hazard because it could reduce political and public pressure for emissions reduction.^[15] Groups such as ETC Group^[16] and individuals such as Raymond Pierrehumbert have called for a moratorium on deployment and out-of-doors testing of geoengineering techniques for climate control.^[17][18]

§Background

Several organizations have investigated geoengineering with a view to evaluating its potential, including the US Congress,^[19] NASA,^[20] the Royal Society,^[21] and the UK Parliament.^[22] The Asilomar International Conference on Climate Intervention Technologies was convened to identify and develop risk reduction guidelines for climate intervention experimentation.^[23]

Environmental organisations such as Friends of the Earth^[24] and Greenpeace^[25] have typically been reluctant to endorse solar radiation management, but are often more supportive of some carbon dioxide removal projects, such as afforestation and peatland restoration. Some authors have argued that any public support for geoengineering may weaken the fragile political consensus to reduce greenhouse gas emissions.^[26]

§Proposed strategies

Several geoengineering strategies have been proposed. IPCC documents detail several notable proposals.^[27] These fall into two main categories: solar radiation management and carbon dioxide removal. However, other proposals exist.
The Geoengineering Climate: Technical Evaluation and Discussion of Impacts project of the National Academy of Sciences funded by United States agencies, including NOAA, NASA, and the CIA,^[28] commenced in March 2013, is expected to issue a report in fall 2014.

"An ad hoc committee will conduct a technical evaluation of a limited number of proposed geoengineering techniques, including examples of both solar radiation management (SRM) and carbon dioxide removal (CDR) techniques, and comment generally on the potential impacts of deploying these technologies, including possible environmental, economic, and national security concerns. The study will:

1. Evaluate what is currently known about the science of several (3-4) selected example techniques, including potential risks and consequences (both intended and unintended), such as impacts, or lack thereof, on ocean acidification,
2. Describe what is known about the viability for implementation of the proposed techniques including technological and cost considerations,
3. Briefly explain other geoengineering technologies that have been proposed (beyond the selected examples), and
4. Identify future research needed to provide a credible scientific underpinning for future discussions.

The study will also discuss historical examples of related technologies (e.g., cloud seeding and other weather modification) for lessons that might be learned about societal reactions, examine what international agreements exist which may be relevant to the experimental testing or deployment of geoengineering technologies, and briefly explore potential societal and ethical considerations related to geoengineering. This study is intended to provide a careful, clear scientific foundation that informs ethical, legal, and political discussions surrounding geoengineering.

The project has support from the National Academy of Sciences, the U.S. intelligence community, the National Oceanic and Atmospheric Administration, and the National Aeronautics and Space Administration. The approximate start date for the project is March 2013; a report is expected be issued in fall 2014."^[29]

§Solar radiation management

Solar radiation management (SRM)^[2][30] techniques would seek to reduce sunlight absorbed (ultra-violet, near infra-red and visible). This would be achieved by deflecting sunlight away from the Earth, or by increasing the reflectivity (albedo) of the atmosphere or the Earth's surface. These methods would not reduce greenhouse gas concentrations in the atmosphere, and thus would not seek to address problems such as the ocean acidification caused by CO₂. In general solar radiation management projects would have the advantage of speedy deployment and effect when compared to other climate policies of mitigation or carbon dioxide removal. While greenhouse gas remediation offers a more comprehensive possible solution to climate change, it does not give instantaneous results; for that, solar radiation management is required.^{[dubious – discuss]}
Solar radiation management methods^[2] may include:

• Surface-based (land or ocean albedo modification); e.g. cool roof—using pale-coloured roofing and paving materials.
• Troposphere-based, for example cloud whitening – using fine sea water spray to whiten clouds and thus increase cloud reflectivity.
• Upper atmosphere-based: creating reflective aerosols, such as stratospheric sulfate aerosols, aluminium oxide particles, even specifically designed self-levitating aerosols.^[31]
• Space-based: space sunshade—obstructing solar radiation with space-based mirrors, asteroid dust,^[32] etc.

§Carbon dioxide removal

Carbon dioxide removal projects seek to remove greenhouse gases from the atmosphere. Proposed methods include those that directly remove such gases from the atmosphere, as well as indirect methods that seek to promote natural processes that draw down and sequester CO2 (e.g. tree planting). Many projects overlap with carbon capture and storage and carbon sequestration projects, and may not be considered to be geoengineering by all commentators. Techniques in this category include:

• Creating biochar and mixing it with soil to create terra preta
• Bio-energy with carbon capture and storage to sequester carbon and simultaneously provide energy
• Carbon air capture to remove carbon dioxide from ambient air
• Planting trees to offset carbon emissions
• Ocean nourishment including iron fertilisation of the oceans

Significant reduction in ice volume in the Arctic Ocean in the range between 1979 and 2007 years

§Justification

§Tipping points and positive feedback

Climate change during the last 65 million years. The Paleocene–Eocene Thermal Maximum is labelled PETM.

It is argued that climate change may cross tipping points^[33] where elements of the climate system may 'tip' from one stable state to another stable state, much like a glass tipping over. When the new state is reached, further warming may be caused by positive feedback effects,.^[34] An example of a proposed causal chain leading to runaway global warming is the collapse of Arctic sea ice triggering subsequent release of methane.^[35]

The precise identity of such "tipping points" is not clear, with scientists taking differing views on whether specific systems are capable of "tipping" and the point at which this "tipping" will occur.^[36] An example of a previous tipping point is that which preceded the rapid warming leading up to the Paleocene–Eocene Thermal Maximum. Once a tipping point is crossed, cuts in anthropogenic greenhouse gas emissions will not be able to reverse the change. Conservation of resources and reduction of greenhouse emissions, used in conjunction with geoengineering, are therefore considered a viable option by some commentators.^[37][38][39] Geoengineering offers the hope of temporarily reversing some aspects of climate change and allowing the natural climate to be substantially preserved whilst greenhouse gas emissions are brought under control and removed from the atmosphere by natural or artificial processes.

§Costs

Some geoengineering techniques, such as cool roof techniques, can be achieved at little or no cost, and may even offer a financial payback.^[40] IPCC (2007) concluded that reliable cost estimates for geoengineering options had not been published.^[41] More recently, early research into costs of solar radiation management have been published.^[42]
This suggests that "well designed systems" might be available for costs in the order of a few hundred million dollars per year.^[43] These are much lower than costs to achieve comprehensive reductions in CO₂ emissions.^{[citation needed]} Such costs would be within the budget of most nations, and even a handful of rich individuals.^[44]

In their 2009 report Geoengineering the climate the Royal Society adjudged afforestation and stratospheric aerosols as the methods with the "highest affordability" (meaning lowest costs). Furthermore stratospheric aerosol injection, having the highest effectiveness and affordability, would be the nearest approximation to the "ideal method", with the (significant) disadvantage of high uncertainties considering safety and unwanted side effects. While afforestation scored highly for safety, it was found to be of limited effectiveness for treating climate change^.

§Ethics and responsibility

Climate engineering would represent a large-scale, intentional effort to modify the environment, which differ from inadvertent climate change through activities such as burning fossil fuels. Intentional climate change is viewed very differently from a moral standpoint.^[45] This raises questions of whether we as humans have the right to change the climate, and under what conditions this right obtains. Furthermore, ethical arguments often confront larger considerations of worldview, including individual and social religious commitments. For many, religious beliefs are pivotal in defining the role of human beings in the wider world. Some religious communities might claim that humans have no responsibility in managing the climate, instead seeing such world systems as the exclusive domain of a Creator. In contrast, other religious communities might see the human role as one of "stewardship" or benevolent management of the world.^[46] The question of ethics also relates to issues of policy decision-making. For example, the selection of a globally agreed target temperature is a significant problem in any geoengineering governance regime, as different countries or interest groups may seek different global temperatures.^[47]

What most ethicists, policy-makers, and scientists agree on is this: Solar radiation management is an incomplete solution to global warming.^[48] The possible option of geoengineering may reduce incentives to reduce emissions of greenhouse gases. It is argued that geoengineering could be used to 'buy time' before drastic climate change happens, allowing mitigation and adaptation measures more time to be implemented and work.^[49] But the opposition points out that the resources spent on geoengineering could be used for mitigation and efforts to reduce emissions of greenhouse gases. Geoengineering also does not resolve other issues related to increasing levels of carbon dioxide.

§Political viability

It has been argued that regardless of the economic, scientific and technical aspects, the difficulty of achieving concerted political action on climate change requires other approaches.^[50] Those arguing political expediency say the difficulty of achieving meaningful emissions cuts^[51] and the effective failure of the Kyoto Protocol demonstrate the practical difficulties of achieving carbon dioxide emissions reduction by the agreement of the international community.^[52] However, others point to support for geoengineering proposals among think tanks with a history of climate change skepticism and opposition to emissions reductions as evidence that the prospect of geoengineering is itself already politicized and being promoted as part of an argument against the need for (and viability of) emissions reductions; that, rather than geoengineering being a solution to the difficulties of emissions reductions, the prospect of geoengineering is being used as part of an argument to stall emissions reductions in the first place.^[53]

Geoenginering poses several challenges in the context of governance because of issues of power and jurisdiction.^[43] Geoengineering as a climate change solution differs from other mitigation and adaptation strategies. Unlike a carbon trading system that would be focused on participation from multiple parties along with transparency, monitoring measures and compliance procedures; this is not necessarily required by geoengineering. Bengtsson^[54] (2006) argues that "the artificial release of sulphate aerosols is a commitment of at least several hundred years". This highlights the importance for a political framework that is sustainable enough to contain a multilateral commitment over such a long period and yet is flexible as the techniques innovate through time. There are many controversies surrounding this topic and hence, geoengineering has been made into a very political issue. Most discussions and debates are not about which geoengineering technique is better than the other, or which one is more economically and socially feasible. Discussions are broadly on who will have control over the deployment of geoengineering and under what governance regime the deployment can be monitored and supervised. This is especially important due to the regional variability of the effects of many geoengineering techniques, benefiting some countries while damaging others. The challenge posed by geoengineering is not how to get countries to do it. It is to address the fundamental question of who should decide whether and how geoengineering should be attempted – a problem of governance.^[55]

§Risks and criticisms

Change in sea surface pH caused by anthropogenic CO₂ between the 1700s and the 1990s. This ocean acidification will still be a major problem unless atmospheric CO₂ is reduced.

Various criticisms have been made of geoengineering,^[56] particularly Solar Radiaton Management (SRM) methods.^[57] Decision making suffers from intransitivity of policy choice.^[58] Some commentators appear fundamentally opposed. Groups such as ETC Group^[16] and individuals such as Raymond Pierrehumbert have called for a moratorium on geoengineering techniques.^[17][18]

§Ineffectiveness

The effectiveness of the schemes proposed may fall short of predictions. In ocean iron fertilization, for example, the amount of carbon dioxide removed from the atmosphere may be much lower than predicted, as carbon taken up by plankton may be released back into the atmosphere from dead plankton, rather than being carried to the bottom of the sea and sequestered.^[59]

§Incomplete solution to CO₂ emissions

Techniques that do not remove greenhouse gases from the atmosphere may control global warming, but do not reduce other effects from these gases, such as ocean acidification.^[60] While not an argument against geoengineering per se, this is an argument against reliance on geoengineering to the exclusion of greenhouse gas reduction.

§Control and predictability problems

The full effects of various geoengineering schemes are not well understood.^[10] Matthews et al.^[61] compared geoengineering to a number of previous environmental interventions and concluded that "Given our current level of understanding of the climate system, it is likely that the result of at least some geoengineering efforts would follow previous ecological examples where increased human intervention has led to an overall increase in negative environmental consequences."

Performance of the systems may become ineffective, unpredictable or unstable as a result of external events, such as volcanic eruptions, phytoplankton blooms, El Niño, solar flares, etc., potentially leading to profound and unpredictable disruption to the climate system.

It may be difficult to predict the effectiveness of projects,^[62] with models of techniques giving widely varying results.^[63] In the instances of systems which involve tipping points, this may result in irreversible effects. Climate modelling is far from an exact science even when applied to comparatively well-understood natural climate systems, and it is made more complex by the need to understand novel and unnatural processes which by definition lack relevant observation data.^[64]

§Side effects

The techniques themselves may cause significant foreseen or unforeseen harm. For example, the use of reflective balloons may result in significant litter,^[65] which may be harmful to wildlife.

Ozone depletion is a risk of some geoengineering techniques, notably those involving sulfur delivery into the stratosphere.^[66]

The active nature of geoengineering may in some cases create a clear division between winners and losers. Most of the proposed interventions are regional, such as albedo modification in the Arctic.^[67]

There may be unintended climatic consequences, such as changes to the hydrological cycle^[68] including droughts^[69] or floods, caused by the geoengineering techniques, but possibly not predicted by the models used to plan them.^[70] Such effects may be cumulative or chaotic in nature, making prediction and control very difficult.^[71]

Not all side effects are negative, and an increase in agricultural productivity has been predicted by some studies.^[72]

§Unreliable systems

The performance of the interventions may be inconsistent due to mechanical failure, non-availability of consumables or funding problems.

The geoengineering techniques would, in many instances, be vulnerable to being switched off or deliberately destroyed. As examples, cloud making ships could be switched off or sunk and space mirrors could be tilted to make them useless. Anyone capable of exerting such power may seek to abuse it for commercial gain, military advantage or simple terrorism.

§Termination shock

If solar radiation management were masking a significant amount of warming and then were to abruptly stop, the climate would rapidly warm.^[73] This would cause a sudden rise in global temperatures towards levels which would have existed without the use of the geoengineering technique. The rapid rise in temperature may lead to more severe consequences than a gradual rise of the same magnitude.^[73]

§Weaponisation

In 1976, 85 countries signed the U.N. Convention on the Prohibition of Military or Any Other Hostile Use of Environmental Modification Techniques.^[43] The Environmental Modification Convention generally prohibits weaponising geoengineering techniques. However, this does not eliminate the risk. If perfected to a degree of controllability and accuracy that is not considered possible at the moment, geoengineering techniques could theoretically be used by militaries to droughts or famines.^[74] Theoretically they could also be used simply to make battlefield conditions more favourable to one side or the other in a war.^[75]

Carnegie's Ken Caldeira said, "It will make it harder to achieve broad consensus on developing and governing these technologies if there is suspicion that gaining military advantage is an underlying motivation for its development..."^[76]

§Effect on sunlight, sky and clouds

Managing solar radiation using aerosols or cloud cover would involve changing the ratio between direct and indirect solar radiation. This would affect plant life^[77] and solar energy.^[78] It is believed that there would be a significant effect on the appearance of the sky from stratospheric aerosol injection projects, notably a hazing of blue skies and a change in the appearance of sunsets.^[79] Aerosols are affecting the formation of clouds, especially cirrus clouds.^[80]

§Moral hazard

The existence of such techniques may reduce the political and social impetus to reduce carbon emissions.^[81]
However, this issue has been researched in an in-depth study by Ipsos MORI for NERC,^[82] which does not support the Moral Hazard argument. Other modelling work suggests that the threat of geoengineering by a rogue state may in fact increase the likelihood of emissions reduction.^[83] The issue of moral hazard means that many environmental groups and campaigners are reluctant to advocate geoengineering for fear of reducing the imperative to cut greenhouse gas emissions.^[84]

§Governance

Geoengineering opens up various political and economic issues. David Keith argues that the cost of geoengineering the Earth is within the realm of small countries, large corporations, or even very wealthy individuals.^[85] Steve Rayner agrees that not all geoengineering possibilities are expensive, and that some, such as ocean iron fertilisation, are within the reach of very wealthy individuals, calling them a "Greenfinger" (after the fictional Goldfinger).^[86][87] David Victor suggests that geoengineering is within the reach of any individual who has a small fraction of the bank account of Bill Gates, who takes it upon him or her self to be the "self-appointed protector of the planet".^[88] However, it has been argued that a rogue state threatening geoengineering may strengthen action on mitigation.^[83]

This may seem to eliminates any control over who gets to decide when to cool the Earth and how this should be done.^[85] The resulting power would be enormous, and could not necessarily be readily controlled by legal, political or regulatory systems.^[86] The legal and regulatory systems may face a significant challenge in effectively regulating the use of these technologies in a manner that allows for an acceptable result for society. There are however significant incentives for states to cooperate in choosing a specific geoengineering policy, which make unilateral deployment a rather unlikely event.^[89]

A small number carbon offsetting firms have in the past attempted to set up unregulated and unsupervised geoengineering projects. In the long-run such firms may aim to sell carbon credits to individuals, firms or countries.

Geoengineering has the potential to cause significant environmental damage, and could even end up releasing further greenhouse gases into the atmosphere.^[90] Opposition to some early schemes has been intense, with respected environmental groups campaigning against them.^[91] Some researchers have suggested that building a global agreement on geoengineering deployment will be very difficult, and instead power blocs are likely to emerge.^[92]

There is presently a lack of a universally agreed framework for the regulation of either geoengineering activity or research. The London Convention addresses some aspects of the law in relation to biomass ocean storage and ocean fertilization. Scientists at the Oxford Martin School at Oxford University have proposed a set of voluntary principles, which may guide geoengineering research. The short version of the 'Oxford Principles'^[93] is:

• Principle 1: Geoengineering to be regulated as a public good.
• Principle 2: Public participation in geoengineering decision-making
• Principle 3: Disclosure of geoengineering research and open publication of results
• Principle 4: Independent assessment of impacts
• Principle 5: Governance before deployment

These principles have been endorsed by the House of Commons of the United Kingdom Science and Technology Select Committee on “The Regulation of Geoengineering”,^[94] and have been referred to by authors discussing the issue of governance.^[95]

The Asilomar conference was replicated to deal with the issue of geoengineering governance,^[95] and covered in a TV documentary, broadcast in Canada.

§Implementation issues

There is general consensus that no geoengineering technique is currently sufficiently safe or effective to solve the problem of climate change, for the reasons listed above. Some environmentalists see some of the calls for geoengineering to be researched as part of an explicit strategy to delay emissions reductions on the part of those with connections to coal and oil industries.^{[96][improper synthesis?]}

All proposed geoengineering techniques require implementation on a relatively large scale, in order to make a significant difference to the Earth's climate. The least costly schemes are budgeted at a cost of millions,^[97] with many more complex schemes such as space sunshade costing far more.

Many techniques, again such as space sunshade, would require a complex technical development process before they are ready to be implemented. There is no clear institutional mechanism for handling this research and development process. As a result, many promising techniques do not have the engineering development or experimental evidence to determine their feasibility or efficacy at present.

Once a technique has been developed and tested, its implementation may still be difficult. Climate change is by nature a global problem, and therefore no one institution, company or government is responsible for it. Who was to bear the substantial costs of some geoengineering techniques (especially CDR methods) therefore would be hard to agree. Roll-out of such technologies is therefore likely to be delayed until these issues can be resolved.

Due to the potentially uneven changes caused by geoengineering interventions, legal issues may also be an impediment to implementation. The changes resulting from some geoengineering techniques (particularly SRM methods) may benefit some people and disadvantage others (although modelling studies have indicated that the effects would be much less unequal than the effects of climate change that the geoengineering would be masking). There may therefore be legal challenges to the implementation of geoengineering techniques by those who perceive that they are adversely affected by them.^[98]

§Evaluation of geoengineering

Most of what is known about the suggested techniques is based on laboratory experiments, observations of natural phenomena and on computer modelling techniques. Some geoengineering schemes employ methods that have analogues in natural phenomena such as stratospheric sulfur aerosols and cloud condensation nuclei. As such, studies about the efficacy of these schemes can draw on information already available from other research, such as that following the 1991 eruption of Mount Pinatubo. However, comparative evaluation of the relative merits of each technology is complicated, especially given modelling uncertainties and the early stage of engineering development of many geoengineering schemes.^[99]

Reports into geoengineering have also been published in the United Kingdom by the Institution of Mechanical Engineers^[7] and the Royal Society.^[8] The IMechE report examined a small subset of proposed schemes (air capture, urban albedo and algal-based CO₂ capture schemes), and its main conclusions were that geoengineering should be researched and trialled at the small scale alongside a wider decarbonisation of the economy.^[7]

The Royal Society review examined a wide range of geoengineering schemes and evaluated them in terms of effectiveness, affordability, timeliness and safety (assigning qualitative estimates in each assessment). The report divided schemes into "carbon dioxide removal" (CDR) and "solar radiation management" (SRM) approaches that respectively address longwave and shortwave radiation. The key recommendations of the report were that "Parties to the UNFCCC should make increased efforts towards mitigating and adapting to climate change, and in particular to agreeing to global emissions reductions", and that "[nothing] now known about geoengineering options gives any reason to diminish these efforts".^[8] Nonetheless, the report also recommended that "research and development of geoengineering options should be undertaken to investigate whether low risk methods can be made available if it becomes necessary to reduce the rate of warming this century".^[8]

In a 2009 review study, Lenton and Vaughan evaluated a range of geoengineering schemes from those that sequester CO₂ from the atmosphere and decrease longwave radiation trapping, to those that decrease the Earth's receipt of shortwave radiation.^[6] In order to permit a comparison of disparate techniques, they used a common evaluation for each scheme based on its effect on net radiative forcing. As such, the review examined the scientific plausibility of schemes rather than the practical considerations such as engineering feasibility or economic cost. Lenton and Vaughan found that "[air] capture and storage shows the greatest potential, combined with afforestation, reforestation and bio-char production", and noted that "other suggestions that have received considerable media attention, in particular "ocean pipes" appear to be ineffective".^[6] They concluded that "[climate] geoengineering is best considered as a potential complement to the mitigation of CO₂ emissions, rather than as an alternative to it".^[6]

In October 2011, a Bipartisan Policy Center panel issued a report urging immediate researching and testing in case "the climate system reaches a 'tipping point' and swift remedial action is required".^[100]

§National Academy of Sciences

The National Academy of Sciences ran a 21-month project which studied how humans might influence weather patterns, assessed dangers and investigated possible national security implications of geoengineering attempts. The project was funded by the CIA, the National Oceanic and Atmospheric Administration, and NASA.^[101]

According to the two-volume study released in February 2015:

There is no substitute for dramatic reductions in greenhouse gas emissions to mitigate the negative consequences of climate change, a National Research Council committee concluded in a two-volume evaluation of proposed climate-intervention techniques. Strategies to remove carbon dioxide from the atmosphere are limited by cost and technological immaturity, but they could contribute to a broader portfolio of climate change responses with further research and development. Albedo-modification technologies, which aim to increase the ability of Earth or clouds to reflect incoming sunlight, pose considerable risks and should not be deployed at this time.^[102]

§Intergovernmental Panel on Climate Change

The Intergovernmental Panel on Climate Change (IPCC) has assessed the scientific literature on climate engineering (referred to as "geoengineering" in its reports). The IPCC's Fourth Assessment Report was published in 2007. It states:^[41]

Geo-engineering options, such as ocean fertilization to remove CO₂ directly from the atmosphere, or blocking sunlight by bringing material into the upper atmosphere, remain largely speculative and unproven, and with the risk of unknown side-effects. Reliable cost estimates for these options have not been published

Working Group I's contribution to the IPCC's Fifth Assessment Report was published in 2013. It states:^[103]

Models suggest that if SRM methods were realizable they would be effective in countering increasing temperatures, and would be less, but still, effective in countering some other climate changes. SRM would not counter all effects of climate change, and all proposed geoengineering methods also carry risks and side effects. Additional consequences cannot yet be anticipated as the level of scientific understanding about both SRM and CDR is low. There are also many (political, ethical, and practical) issues involving geoengineering that are beyond the scope of this report.

Climatology

From Wikipedia, the free encyclopedia

Climatology (from Greek κλίμα, klima, "place, zone"; and -λογία, -logia) is the study of climate, scientifically defined as weather conditions averaged over a period of time.^[1] This modern field of study is regarded as a branch of the atmospheric sciences and a subfield of physical geography, which is one of the Earth sciences. Climatology now includes aspects of oceanography and biogeochemistry. Basic knowledge of climate can be used within shorter term weather forecasting using analog techniques such as the El Niño – Southern Oscillation (ENSO), the Madden-Julian Oscillation (MJO), the North Atlantic Oscillation (NAO), the Northern Annualar Mode (NAM) which is also known as the Arctic oscillation (AO), the Northern Pacific (NP) Index, the Pacific Decadal Oscillation (PDO), and the Interdecadal Pacific Oscillation (IPO). Climate models are used for a variety of purposes from study of the dynamics of the weather and climate system to projections of future climate.

§History

Chinese scientist Shen Kuo (1031–1095) inferred that climates naturally shifted over an enormous span of time, after observing petrified bamboos found underground near Yanzhou (modern day Yan'an, Shaanxi province), a dry-climate area unsuitable for the growth of bamboo.^[2]

Early climate researchers include Edmund Halley, who published a map of the trade winds in 1686 after a voyage to the southern hemisphere. Benjamin Franklin (1706-1790) first mapped the course of the Gulf Stream for use in sending mail from the United States to Europe. Francis Galton (1822-1911) invented the term anticyclone.^[3] Helmut Landsberg (1906-1985) fostered the use of statistical analysis in climatology, which led to its evolution into a physical science.

§Different approaches

Map of the average temperature over 30 years. Data sets formed from the long-term average of historical weather parameters are sometimes called a "climatology".

Climatology is approached in a variety of ways. Paleoclimatology seeks to reconstruct past climates by examining records such as ice cores and tree rings (dendroclimatology). Paleotempestology uses these same records to help determine hurricane frequency over millennia. The study of contemporary climates incorporates meteorological data accumulated over many years, such as records of rainfall, temperature and atmospheric composition. Knowledge of the atmosphere and its dynamics is also embodied in models, either statistical or mathematical, which help by integrating different observations and testing how they fit together. Modeling is used for understanding past, present and potential future climates. Historical climatology is the study of climate as related to human history and thus focuses only on the last few thousand years.

Climate research is made difficult by the large scale, long time periods, and complex processes which govern climate. Climate is governed by physical laws which can be expressed as differential equations. These equations are coupled and nonlinear, so that approximate solutions are obtained by using numerical methods to create global climate models. Climate is sometimes modeled as a stochastic process but this is generally accepted as an approximation to processes that are otherwise too complicated to analyze.

§Indices

Scientists use climate indices based on several climate patterns (known as modes of variability) in their attempt to characterize and understand the various climate mechanisms that culminate in our daily weather. Much in the way the Dow Jones Industrial Average, which is based on the stock prices of 30 companies, is used to represent the fluctuations in the stock market as a whole, climate indices are used to represent the essential elements of climate. 

Climate indices are generally devised with the twin objectives of simplicity and completeness, and each index typically represents the status and timing of the climate factor it represents. By their very nature, indices are simple, and combine many details into a generalized, overall description of the atmosphere or ocean which can be used to characterize the factors which impact the global climate system.

§El Niño – Southern Oscillation[edit]

El Niño impacts

La Niña impacts

El Niño-Southern Oscillation (ENSO) is a global coupled ocean-atmosphere phenomenon. The Pacific ocean signatures, El Niño and La Niña are important temperature fluctuations in surface waters of the tropical Eastern Pacific Ocean. The name El Niño, from the Spanish for "the little boy", refers to the Christ child, because the phenomenon is usually noticed around Christmas time in the Pacific Ocean off the west coast of South America.^[4] La Niña means "the little girl".^[5] Their effect on climate in the subtropics and the tropics are profound. The atmospheric signature, the Southern Oscillation (SO) reflects the monthly or seasonal fluctuations in the air pressure difference between Tahiti and Darwin. The most recent occurrence of El Niño started in September 2006^[6] and lasted until early 2007.^[7]

ENSO is a set of interacting parts of a single global system of coupled ocean-atmosphere climate fluctuations that come about as a consequence of oceanic and atmospheric circulation. ENSO is the most prominent known source of inter-annual variability in weather and climate around the world. The cycle occurs every two to seven years, with El Niño lasting nine months to two years within the longer term cycle,^[8] though not all areas globally are affected. ENSO has signatures in the Pacific, Atlantic and Indian Oceans.

In the Pacific, during major warm events, El Niño warming extends over much of the tropical Pacific and becomes clearly linked to the SO intensity. While ENSO events are basically in phase between the Pacific and Indian Oceans, ENSO events in the Atlantic Ocean lag behind those in the Pacific by 12–18 months. Many of the countries most affected by ENSO events are developing countries within tropical sections of continents with economies that are largely dependent upon their agricultural and fishery sectors as a major source of food supply, employment, and foreign exchange.^[9] New capabilities to predict the onset of ENSO events in the three oceans can have global socio-economic impacts. While ENSO is a global and natural part of the Earth's climate, whether its intensity or frequency may change as a result of global warming is an important concern. Low-frequency variability has been evidenced: the quasi-decadal oscillation (QDO). Inter-decadal (ID) modulation of ENSO (from PDO or IPO) might exist. This could explain the so-called protracted ENSO of the early 1990s.

§Madden–Julian Oscillation

Note how the MJO moves eastward with time.

The Madden–Julian Oscillation (MJO) is an equatorial traveling pattern of anomalous rainfall that is planetary in scale. It is characterized by an eastward progression of large regions of both enhanced and suppressed tropical rainfall, observed mainly over the Indian and Pacific Oceans. The anomalous rainfall is usually first evident over the western Indian Ocean, and remains evident as it propagates over the very warm ocean waters of the western and central tropical Pacific. This pattern of tropical rainfall then generally becomes very nondescript as it moves over the cooler ocean waters of the eastern Pacific but reappears over the tropical Atlantic and Indian Oceans. The wet phase of enhanced convection and precipitation is followed by a dry phase where convection is suppressed. Each cycle lasts approximately 30–60 days. The MJO is also known as the 30–60 day oscillation, 30–60 day wave, or the intraseasonal oscillation.

§North Atlantic Oscillation (NAO)

Indices of the NAO are based on the difference of normalized sea level pressure (SLP) between Ponta Delgada, Azores and Stykkisholmur/Reykjavik, Iceland. The SLP anomalies at each station were normalized by division of each seasonal mean pressure by the long-term mean (1865–1984) standard deviation. Normalization is done to avoid the series of being dominated by the greater variability of the northern of the two stations. Positive values of the index indicate stronger-than-average westerlies over the middle latitudes.^[10]

§Northern Annular Mode (NAM) or Arctic Oscillation (AO)

The NAM, or AO, is defined as the first EOF of northern hemisphere winter SLP data from the tropics and subtropics. It explains 23% of the average winter (December–March) variance, and it is dominated by the NAO structure in the Atlantic. Although there are some subtle differences from the regional pattern over the Atlantic and Arctic, the main difference is larger amplitude anomalies over the North Pacific of the same sign as those over the Atlantic. This feature gives the NAM a more annular (or zonally symmetric) structure.^[10]

§Northern Pacific (NP) Index

The NP Index is the area-weighted sea level pressure over the region 30N–65N, 160E–140W.^[10]

§Pacific Decadal Oscillation (PDO)

The PDO is a pattern of Pacific climate variability that shifts phases on at least inter-decadal time scale, usually about 20 to 30 years. The PDO is detected as warm or cool surface waters in the Pacific Ocean, north of 20° N.
During a "warm", or "positive", phase, the west Pacific becomes cool and part of the eastern ocean warms; during a "cool" or "negative" phase, the opposite pattern occurs. The mechanism by which the pattern lasts over several years has not been identified; one suggestion is that a thin layer of warm water during summer may shield deeper cold waters. A PDO signal has been reconstructed to 1661 through tree-ring chronologies in the Baja California area.

§Interdecadal Pacific Oscillation (IPO)

The Interdecadal Pacific Oscillation (IPO or ID) display similar sea surface temperature (SST) and sea level pressure patterns to the PDO, with a cycle of 15–30 years, but affects both the north and south Pacific. In the tropical Pacific, maximum SST anomalies are found away from the equator. This is quite different from the quasi-decadal oscillation (QDO) with a period of 8–12 years and maximum SST anomalies straddling the equator, thus resembling ENSO.

§Models

Climate models use quantitative methods to simulate the interactions of the atmosphere, oceans, land surface, and ice. They are used for a variety of purposes from study of the dynamics of the weather and climate system to projections of future climate. All climate models balance, or very nearly balance, incoming energy as short wave (including visible) electromagnetic radiation to the earth with outgoing energy as long wave (infrared) electromagnetic radiation from the earth. Any unbalance results in a change in the average temperature of the earth.
The most talked-about models of recent years have been those relating temperature to emissions of carbon dioxide (see greenhouse gas). These models predict an upward trend in the surface temperature record, as well as a more rapid increase in temperature at higher latitudes.

Models can range from relatively simple to quite complex:

• A simple radiant heat transfer model that treats the earth as a single point and averages outgoing energy
• this can be expanded vertically (radiative-convective models), or horizontally
• finally, (coupled) atmosphere–ocean–sea ice global climate models discretise and solve the full equations for mass and energy transfer and radiant exchange.

§Differences with meteorology

In contrast to meteorology, which focuses on short term weather systems lasting up to a few weeks, climatology studies the frequency and trends of those systems. It studies the periodicity of weather events over years to millennia, as well as changes in long-term average weather patterns, in relation to atmospheric conditions. Climatologists study both the nature of climates – local, regional or global – and the natural or human-induced factors that cause climates to change. Climatology considers the past and can help predict future climate change.
Phenomena of climatological interest include the atmospheric boundary layer, circulation patterns, heat transfer (radiative, convective and latent), interactions between the atmosphere and the oceans and land surface (particularly vegetation, land use and topography), and the chemical and physical composition of the atmosphere.

§Use in weather forecasting

A more complicated way of making a forecast, the analog technique requires remembering a previous weather event which is expected to be mimicked by an upcoming event. What makes it a difficult technique to use is that there is rarely a perfect analog for an event in the future.^[11] Some call this type of forecasting pattern recognition, which remains a useful method of observing rainfall over data voids such as oceans with knowledge of how satellite imagery relates to precipitation rates over land,^[12] as well as the forecasting of precipitation amounts and distribution in the future. A variation on this theme is used in Medium Range forecasting, which is known as teleconnections, when you use systems in other locations to help pin down the location of another system within the surrounding regime.^[13] One method of using teleconnections are by using climate indices such as ENSO-related phenomena.^[14]

Environmental technology

From Wikipedia, the free encyclopedia

CleanTech

Sustainable urban design and innovation: Photovoltaic ombrière SUDI is an autonomous and mobile station that replenishes energy for electric vehicles using solar energy.

Environmental technology (envirotech), green technology (greentech) or clean technology (cleantech) is the application of one or more of environmental science, green chemistry, environmental monitoring and electronic devices to monitor, model and conserve the natural environment and resources, and to curb the negative impacts of human involvement. The term is also used to describe sustainable energy generation technologies such as photovoltaics, wind turbines, bioreactors, etc. Sustainable development is the core of environmental technologies. The term environmental technologies is also used to describe a class of electronic devices that can promote sustainable management of resources.

§Examples

• Biofiltration
• Bioreactor
• Bioremediation
• Desalination
• Doubly fed electric machine
• Energy conservation
• Energy saving modules
• Electric vehicles
• Wave energy
• Green computing
• Hydroelectricity
• Wind power
• Wind turbine
• Hydrogen fuel cell
• Ocean thermal energy conversion
• Solar power
• Photovoltaic
• Thermal depolymerization
• Composting toilet
• Pyrolysis

§Renewable energy

A view across a reverse osmosis desalination plant in Nepal.

Renewable energy is energy that can be replenished easily. For years we have been using sources like wood, sun, water, etc. for means for producing energy. Energy that can be produced by natural objects like wood, sun, wind, etc. is considered to be renewable.^[1]

§Water purification

Water purification: The whole idea/concept of having dirt/germ/pollution free water flowing throughout the environment. Many other phenomena lead from this concept of purification of water. Water pollution is the main enemy of this concept, and various campaigns and activists have been organized around the world to help purify water.^[2]

§Air purification

Air purification: Basic and common green plants can be grown indoors to keep air fresh because all plants remove CO₂ and convert it into oxygen. The best examples are: Dypsis lutescens, Sansevieria trifasciata, and Epipremnum aureum.^[3]

§Sewage treatment

Sewage treatment is conceptually similar to water purification. Sewage treatments are very important as they purify water per levels of its pollution. The more polluted water is not used for anything, and the least polluted water is supplied to places where water is used affluently. It may lead to various other concepts of environmental protection, sustainability etc.^[4]

§Environmental remediation

Environmental remediation is the removal of pollutants or contaminants for the general protection of the environment. This is accomplished by various chemical, biological, and bulk movements. (encyclopedia of medical concepts)^[5]

§Solid waste management

Net Zero Court zero emissions office building prototype in St. Louis, Missouri

Solid waste management is the purification, consumption, reuse, disposal and treatment of solid waste that is undertaken by the government or the ruling bodies of a city/town.^[6]

§eGain forecasting

Egain forecasting is a method using forecasting technology to predict the future weather's impact on a building.^[7] By adjusting the heat based on the weather forecast, the system eliminates redundant use of heat, thus reducing the energy consumption and the emission of greenhouse gases.^[8]

§Energy conservation

Energy conservation is the utilization of devices that require smaller amounts of energy in order to reduce the consumption of electricity. Reducing the use of electricity causes less fossil fuels to be burned to provide that electricity.

§Alternative and clean power

The Tesla Roadster is the only all-electric sports car for sale and in serial production. It can be plugged into conventional outlets and can be charged fully or partially on renewable energy, including solar, hydroelectric, geothermal or wind power.

Principles:

• Green syndicalism
• Sustainability
• Sustainable design
• Sustainable engineering

Scientists continue to search for clean energy alternatives to our current power production methods. Some technologies such as anaerobic digestion produce renewable energy from waste materials. The global reduction of greenhouse gases is dependent on the adoption of energy conservation technologies at industrial level as well as this clean energy generation. That includes using unleaded gasoline, solar energy and alternative fuel vehicles, including plug-in hybrid and hybrid electric vehicles.

Since industrial use of energy accounts for 51% of worldwide energy usage^[9] improving energy efficiency in this field is a top priority for environmental technology companies around the globe. Advanced energy efficient electric motor (and electric generator) technology that are cost effective to encourage their application, such as the brushless wound-rotor doubly fed electric machine and energy saving module, can reduce the amount of carbon dioxide (CO₂) and sulfur dioxide (SO₂) that would otherwise be introduced to the atmosphere, if electricity is generated using fossil fuels. Greasestock is an event held yearly in Yorktown Heights, New York which is one of the largest showcases of environmental technology in the United States.^{[10][11][12][13][14]}

§Education

Courses aimed at developing graduates with specific skills in environmental systems or environmental technology are becoming more common and fall into three broads classes:

• Environmental Engineering or Environmental Systems courses oriented towards a civil engineering approach in which structures and the landscape are constructed to blend with or protect the environment;
• Environmental chemistry, sustainable chemistry or environmental chemical engineering courses oriented towards understanding the effects (good and bad) of chemicals in the environment. Such awards can focus on mining processes, pollutants and commonly also cover biochemical processes;
• Environmental technology courses oriented towards producing electronic, electrical or electrotechnology graduates capable of developing devices and artefacts able to monitor, measure, model and control environmental impact, including monitoring and managing energy generation from renewable sources, and developing novel energy generation technologies.

Dow Is Latest US Business To Throw Natural Gas Under The Bus

March 17th, 2015 by Tina Casey

Original link:  http://cleantechnica.com/2015/03/17/dow-latest-us-business-throw-natural-gas-bus/

The intertubes are abuzz with news of a major wind energy buy engineered by corporate giant Dow Chemical. The company has announced that it has sealed the deal on an agreement with a soon-to-be-built wind farm in South Texas. Once up and running, the wind farm will provide Dow’s facility in Freeport with 200 MW annually.

That’s gotta be a stab in the heart to Texas natural gas suppliers, which are already suffering the effects of a gas and oil boom turned bust. The big question is, why not gas? After all, until now natural gas has been the go-to choice as a replacement for coal power plants…

Wind Energy, Coal, And Natural Gas

When we think of major renewable energy buys, the first thing that comes to mind is the tech industry. Notably, Tesla, Google, and Apple have been all over wind and solar energy for the past few years, with multiple projects online or in the planning stages.

However, we’re also beginning to see major renewable energy investments amongst more traditional US industries, and Dow provides a good example of the reasoning behind that move.

Generally speaking a couple of things are beginning to undercut the conventional rationale for replacing coal with natural gas.

The oil and gas boom has lowered the price of natural gas and boosted it into a highly competitive position against coal for power generation, and in terms of carbon emissions natural gas is a much cleaner-burning fuel.

However, if we were Dow, we’d give the stinkeye to that cheap natural gas thing. With the oil and gas industry in a bust cycle, drill rigs are being idled, supplies will tighten, and prices will inevitably rise.

In that context, wind energy is a tidy hedge against future price increases. Once the turbines are humming along, the “fuel” is free.

As for carbon emissions, evidence has been piling up regarding the true lifecycle emissions of natural gas, and the picture looks even less pretty when you factor in the risks and impacts associated with fracking and fracking waste disposal (for those of you new to the topic, fracking is short for hydrofracturing, a method of oil and gas drilling that involves shooting fluid into shale formations at high pressure).

Also not helping the case for natural gas is a new coal and wind energy study demonstrating that in terms of reducing carbon emissions, it could make sense to maintain an energy profile that balances more coal power plants with renewable energy, rather than going for a mix that includes fewer coal plants and more natural gas plants.
(DJS -- this is misleading: if the natural gas replaces the coal, there is a net emissions reduction.)

Dow Chemical And Wind Energy

Dow’s wind energy announcement came during a rather interesting week for clean energy. We were just taking note of three new renewable energy studies with questionable pedigrees, one of which purported to show that wind energy is a money-loser, but that doesn’t seem to have taken the wind out of the company’s sails.

Here’s Dow’s VP of Business Operations Seth Roberts on the implications of the new wind energy buy for Dow’s bottom line:

Adding large scale renewable energy to Dow’s manufacturing process is just one smart move that we can make to secure a future of sustainability, growth, and long-term competitive advantage. This decision also serves as a systemic hedge against both energy and power price volatility, while improving our overall carbon footprint.

Okay, so it’s still Dow Chemical (yes, that Dow Chemical), but in addition to its clean tech buys the company’s sustainability goals include transitioning to a more sustainable chemistry platform, so there’s that.

Five Synthetic Materials With The Power To Change The World

February 4, 2015 | by Valeria Arrighi

Original link:  http://www.iflscience.com/chemistry/five-synthetic-materials-power-change-world

Photo credit: Inside Boeing’s Dreamliner: tomorrow’s polymers today. Jordan Tan 

 

The New York World’s Fair of 1939-40 was one of the greatest expos the world had ever seen. Visitors to Flushing Meadow Park in Queens were invited to see the “world of tomorrow” giving them a first glimpse of wonders such as the television, the videophone and the Ford Mustang.

It was also the first chance to see nylon, the world’s first fully synthetic man-made fibre. It was being sewn into pantyhose by a display of knitting machines as two models played tug of war to demonstrate the strength of the fabric. Nylon had been discovered by the Wallace Carothers’ group in DuPont’s research division four years earlier. It was introduced at the fair as the new hosiery “wholly fabricated from such common raw materials as coal, water and air” which could be made into filaments “as strong as steel”.

Nylon stockings went on to become a huge success, of course, selling 64m pairs for DuPont in their first year alone. Nylon had qualities that were superior to those of the natural product, silk, and it soon found many useful, if sometimes less fashionable, applications. Today it is still used very widely in fabrics, upholstery, sport articles, instrument strings and automotive parts.

Nylon: left the shelves like iPhones on steroids. Rebecca Abell

Since the dawning of this new era of fully synthetic materials, the advances have been unparallelled in the history of materials. Chemists have discovered new catalysts and developed new synthetic routes to join small molecules into long polymer chains with the right properties for a particular use – the polypropylene fibres that we use in carpets for example, or hard varieties of polyethylene for making plastic bottles.

Physicists, materials scientists and engineers have also designed new processing methods and new technologies to enhance performance to create substances like super-tough substances like kevlar.

Quite rightly, we are becoming more demanding at the same time. We expect products that will further enhance the quality of our lives, but we want materials and technologies that are increasingly energy efficient, sustainable and capable of reducing global pollution. It’s a challenge.

Here are five types of polymers that will shape the future.

1. Bioplastics
As we are often reminded, plastics do not degrade and are a very visible source of environmental pollution. To complicate things further, the building blocks of these materials, which we call monomers, are historically derived from crude oil, which is not renewable.

But this is changing. Thanks to innovations with the processes for using enzymes and catalysts, it is becoming increasingly possible to convert renewable resources such as biogas into the major building blocks for manufacturing plastics and synthetic rubbers.

These substances are sustainable because they save fossil resources. But of course this only partly solves the problem. Unless they are also biodegradable, they are still a problem for the environment.

Plastic cups that grow on trees! photokup

2. Plastic Composites/Nanocomposites
Plastic composites are the name for plastics which have been reinforced by different fibres to make them stronger or more elastic. For example you can make a polymer stronger by embedding carbon fibres, which creates a lightweight material which is ideal for modern fuel-efficient transport.

These kinds of fibre-reinforced plastics are being increasingly used, particularly in the aerospace industry (the Boeing 787 and the Airbus A360 are 50% composite). Were it not for the high costs, these materials would be used in all vehicles.

More recent additions to the field are nanocomposites, where plastics are instead reinforced with tiny particles of other substances – including graphene. These have any number of potential uses, ranging from lightweight sensors on wind turbine blades to more powerful batteries to internal body scaffolds that speed up the healing process for broken bones.

Nanocomposites will become particularly exciting if we succeed in producing them through processing methods that make it possible to design them in a very controlled manner. If we look at the structures of materials in nature, such as wood, you find they are incredibly complicated and intricate. Our current composites and nanocomposites are very unsophisticated by comparison.

3. Self-Healing Polymers
No matter how carefully we select materials for engineering applications based on their ability to withstand mechanical stresses and environmental conditions, they will inevitably fail. Ageing, degradation and loss of mechanical integrity due to impact or fatigue are all contributing factors. Not only is this very costly, it can be disastrous, as was the case with the Deepwater Horizon explosion in the Gulf of Mexico in 2010 for instance.
Inspired by biological systems, new materials are being developed which are able to heal in response to what would be traditionally considered irreversible damage. Polymers are not the only materials with the potential for self-healing, but they seem to be very good at it. Within a few years since their first discovery around the turn of the century, many innovative healing systems have been proposed.

What is still incredibly challenging is the idea of extending these concepts to large-volume applications, since self-healing polymers demand much more complicated design than previous generations of polymers. But this seems the ultimate route towards long-lasting, fault-tolerant materials that can be used for products including coatings, electronics and transport.

4. Plastic Electronics
Most polymers are insulators and therefore don’t conduct electricity. However an upsurge in this field of polymer research emerged in 2000 after the award of a Nobel Prize to Alan MacDiarmid, Alan Heeger and Hideki Shirakawa for work on discovering that a polymer named polyacetylene became conductive when impurities were introduced through a process known as doping.

Not only does the same process make other similar polymers conductive, some can even be converted into light-emitting diodes (LEDs), raising the prospect of flexible computer screens like the one below.

Flexible screen display by Plastic Logic Plastic Logic, CC BY-SA

This is an area where polymers still face considerable challenge and strong competition from incumbents like silicon and organic LEDs. Still, when looking for cheap flexible replacements to existing electronic devices, polymers have much to offer as they can be easily processed in solutions and can be 3D-printed.

There seems to be enormous research going on in this area, with polymers sometimes playing the role of the active component, such as in semiconductors, and sometimes acting as a vehicle for other substances, such as in conductive inks.

5. Smart And Reactive Polymers
Gels and synthetic rubbers can easily adjust their shape in response to external stimuli, which means they are able to respond to changes in their surroundings. The external stimulus would usually be a change in temperature or acidity/alkalinity but it could equally be light, ultrasound or chemical agents. This turns out to be incredibly useful in designing smart materials for sensors, drug delivery devices and many other applications.

You can greatly extend a polymer’s natural ability to respond to such stimuli by designing them with this purpose in mind. Mechanophores, for example, are molecular units that can alter the properties of a polymer when they are subjected to mechanical forces. These could have any number of industrial applications, especially if self-healing technology was incorporated too.

Other possibilities for smart polymers include things like window coatings that can wash the windows when they are dirty, and medical stitches that disappear when an injury has healed.