US withdrawal from the COP21 Paris Climate Change Agreement, and its possible implications.

Published in the journal, Science Progress  Volume 100 Number 4 2017

Background.

The global media have reacted with a combination of disappointment and dumbfoundedness, in the wake of the decision by the United States of America to abrogate its curbing of carbon emissions¹, as set forth in the Paris Agreement, at the COP21 United Nations Climate Change Conference² in December 2015. Thus, the US joins a rather exclusive club, consisting of Syria (whose energies and considerations have been more pressingly occupied by the civil war which has raged there for the past 6 years) and Nicaragua, a nation so successful in providing its energy from low-carbon sources that it does not need to sign up for any further amelioration of its emissions, but rather sets a pristine example to much of the rest of the world¹. China, now at overcapacity against demand for coal-fired power production³, has emphasised to the US that fighting climate change is a global responsibility⁴, and around 40 other independent nations⁵, along with the United Nations, the European Union and the African Union, have expressed their concern, disappointment or outrage, and reaffirmed their own commitments⁵ to abide by the treaty. Even major oil companies such as ExxonMobil and Chevron, are against the US decision, and have vowed to hold to the agreement, irrespective of it⁶. It is indeed true that the agreement is not legally binding, but more a citizens’ charter of individual nations, who will receive no further retribution than to be named and shamed² should they ultimately fail to comply, as the US may profoundly demonstrate.

The purpose of the Paris Agreement⁷ is to limit “the increase in the global average temperature to well below 2 °C above pre-industrial levels and [pursue] efforts to limit the temperature increase to 1.5 °C above pre-industrial levels", primarily through limiting greenhouse gas emissions (Figure 1), to which the US became a signatory in April 2016, and accepted it by executive order in September of the same year. Donald Trump, of the Republican Party, was elected into office as President of the United States on November 8^th 2016, just 4 days after the Paris Agreement entered into force in the US: during his election campaign, Trump had voiced his intention to revamp the US coal industry, which in his opinion has been disadvantaged by environmental regulations⁸. Trump issued an executive order to reverse the Clean Power Plan (which was inaugurated by his predecessor President Obama), and other environmental regulations, during the early stages of his presidency⁹.  Obama had also committed the US to providing $3 billion for the Green Climate Fund (intended to assist developing countries in coping with the effects of climate change, by means of raising an annual $100 billion by 2020) which Trump has criticised as a scheme to redistribute wealth from rich to poor countries¹⁰. Prior to his announcement, President Trump had been urged to revoke the U.S. commitment to the Paris Agreement, in a letter¹¹ signed by 20 Members of the European Parliament, 10 from the UK Independence (UKIP) Party¹², on the grounds that:

“We believe that the Paris agreement is potentially damaging, especially to developed western economies.  We also believe that an early decision by your Administration to pull out of the Paris agreement will effectively neuter it, to the benefit of us all. 

At the same time, we would urge you to take action to withdraw the carbon dioxide endangerment finding, which has no sound basis in science, but which provides a pretext for damaging and extreme environmental policies.”

Trump had similarly been exhorted by 22 US Republican senators, to pull out of the Paris Agreement, although it has been stressed that most of the signatories on the letter are from states with an economic reliance on the combustion of fossil fuels¹³, and claimed¹⁴ that the group of 22 senators had, between them, benefitted from contributions to their election campaigns to the tune of over $10 million from companies dealing in oil, gas and coal, during the past three elections. However, a group of 40 senators¹³ from the Democrats had also written to the President counselling him to abide by the Agreement, emphasising that, "a withdrawal would hurt America's credibility and influence on the world stage."

The Announcement itself.

As a prelude to the announcement, at the G7 summit in late May 2017, President Trump stood alone in refusing to confirm commitment by the United States to the Paris Agreement, and a communication was issued at the end of the conference stating that the US "is not in a position to join the consensus" of other G7 countries regarding policies on climate change and the Paris Agreement¹⁵. Then, on June 1st, 2017, he announced that the US would cease all participation^1,16 in the 2015 Paris Agreement, but that he was prepared to negotiate for "a better deal". However, European and UN leaders made the point that the pact "cannot be renegotiated at the request of a single party"¹⁷. In his announcement, Trump affirmed that "In order to fulfil my solemn duty to protect the United States and its citizens, the United States will withdraw from the Paris climate accord." He averred that implementation of the agreement would lose the United States $3 trillion worth of GDP and result in the loss of 6.5 million jobs¹⁸. He further remarked that it would "undermine our economy, hamstring our workers," and "effectively decapitate our coal industry"¹⁹.

According to its Article 28, the United States cannot depart from the Agreement before November 4th, 2020, and until then, it may be obligated to maintain its agreed commitments, including that it continues to report its emissions figures to the United Nations. However, since the agreement has not been ratified by the Senate, it has been speculated that this may not prove binding²⁰.

Global reactions.

As already noted, the reactions from the world’s governments have been almost universally hostile⁵ to the prospect of the US withdrawing from the Paris Agreement. Similarly, the overall reaction from the scientific community is one of great disappointment, if not outright appal, as was reported²¹ in the journal Nature. However, in the journal Nature Climate Change, Luke Kemp of the Australian National University has written a commentary²² in which he concludes that, “Continued US membership in the Paris Agreement on climate would be symbolic and have no effect on US emissions. Instead, it would reveal the weaknesses of the agreement, prevent new opportunities from emerging, and gift greater leverage to a recalcitrant administration.” In part, the basis of this argument is that, “the greenhouse gas emissions of the US are divorced from international legal obligations." Kemp does, nonetheless, conclude that should the US abandon contributing to the Green Climate Fund, it would make it more difficult to maintain activities globally to ameliorate climate change and to cope with its consequences. Kemp also noted that, "a rogue US can cause more damage inside rather than outside of the agreement." He concludes by saying²², "A withdrawal could also make the US into a climate pariah and provide a unique opportunity for China and the EU to take control of the climate regime and significantly boost their international reputations and soft power.”

In an interview by the Washington Post²³, a colleague of Kemp, Frank Jotzo, accords with his view that it could be more damaging for the US to remain, or in any case that the consequences of its withdrawal will be less severe than has been feared by some, saying, “The US leaving the Paris agreement is unlikely to have a domino effect. And it is a long game: the next president might decide to rejoin the agreement, or join a successor agreement.” Indeed, should the US desist from its participation in the Agreement at this stage, it could reunite at some future point; as was remarked upon by Kemp²³, “A future president could rejoin Paris at the flick of a pen.” In accord with this option, in Trump’s written statement²⁴, is the phrase “…the United States will withdraw from the Paris Climate Accord but begin negotiations to re-enter either the Paris Accord or a really entirely new transaction on terms that are fair to the United States…” So, the US divorce from the Paris Agreement is not yet “absolute”; however, Senator John Kerry is highly sceptical²⁵ that the president has any intention of acceding to any such agreement. An independent report has warned of the likely adverse consequences should the international community delay in its actions to combat climate change²⁶.

The reaction from the commercial world is mixed, but a number of large organisations⁶ have expressed their opposition to Trump’s decision, and confirmed their intention to pursue low-carbon policies, including Apple, General Electric, Google, Facebook, Goldman Sachs, Tesla, Morgan Stanley, PepsiCo, Walmart and Walt Disney, ExxonMobil and Chevron, along with ConocoPhillips²⁷ and Microsoft²⁷. A bipartisan group of US states formed the “US Climate Alliance”²⁸, and this was followed rapidly by the “We Are Still In” (WASI)²⁹ campaign, created by a group which includes 125 cities, 9 states, 902 businesses and investors, and 183 colleges and universities, all motivated by a collective support for the Paris Agreement, on the basis that taking action against climate change is both good for America and is the nation’s obligation to the world²⁸. Meanwhile, the state of California has signed a climate agreement²⁹ with China.

Possible consequences.

Of concern is the prospect that other nations could follow the US example, and similarly withdraw from the Paris Agreement. Indeed, one analysis²⁶ suggests that should the rest of the world delay taking action by 8 years, the result would be a doubling of cumulative CO₂ emissions over the next century, rendering the 2 ^oC target unattainable. As an example from history, we may note that although the US signed the Kyoto Protocol, it did not formally ratify the agreement: this led to the adoption of the Marrakech Accords by the international community, but further actions stalled. In 2007, the Bali Road Map was introduced, so marking the abandonment of Kyoto, and the inauguration of a new treaty which involved the US, i.e. the Paris Agreement²². It seems unlikely that the Paris Agreement will be derailed by a US withdrawal, in the short term at least, since the international community has emphasised almost universal commitment to it. However, even if the US remains as a club member, given its economic power and significance as a principal global CO₂-emitter (Figure 1), should it fail to deliver on its agreed targets, other parties might feel less inclined to honour their own.

Leading climate change scientists, James Hansen and Michael Schellenberger have co-authored an article³⁰, in which they make a case that it is necessary to build more nuclear power stations, since solar and wind energy cannot replace fossil fuels entirely. The US is the world’s second largest CO₂ emitter, meaning that its promised carbon reductions would have accounted for over one fifth of the Agreement’s total emissions cuts by 2030³¹. A truly “worst case” scenario of the effects of climate change has been presented in an article published in New York Magazine , with the self-explanatory title “The Uninhabitable Earth”, which has evoked mixed responses³².

Global Trends in Carbon Emissions.

Part of the increase in CO₂ emissions from developing countries such as China and India is a result of richer Western nations “outsourcing” their manufacture to these Eastern nations, effectively exporting the emissions and importing the goods. While, during the early 2000s, such transfers were increasing at 11% per year, it is now domestic growth that is the cause of rising emissions in Asia: 97% of the steel and 99% of the concrete made in China is actually used in China³³. Moreover, there is now a trend in outsourcing emissions within Chinese borders, since the richer coastal provinces consume more than the poorer hinterlands, where the manufacturing is done³⁴. There has been a “flattening” in global CO₂ emissions, over the past few years³⁵, which is attributed by the International Energy Agency (IEA) to “growing renewable power generation, switches from coal to natural gas, improvements in energy efficiency, as well as structural changes in the global economy.” The United States experienced a 1.6% decrease in its energy-related emissions in 2016, as a result of substituting natural gas for coal, and an expansion of wind and solar energy production. CO₂ emissions in Europe remained flat in 2016, while in China, the effect of moving away from heavy industry has apparently led to a smaller consumption of coal, though one commentator has raised a question mark over the reliability of the statistics for this³⁵.

The BP Statistical Review of World Energy 2017 was published in June 2017, and reckons the actual quantities of fossil and other energy resources for the year 2016. In summary, the following picture emerges³⁶:

·                     The use of Oil (Crude oil + Condensate +Natural Gas Liquids) was static.

·                     The use of gas was static.

·                     The use of nuclear energy continues to recover.

·                     The installation of hydroelectric power continues to rise.

·                     The installation of wind, solar and other renewable energy sources are all increasing.

·                     The use of coal continues to decline.

How can we best deal with the “changing climate”?

It is worth asking the question, that irrespective of a US withdrawal from the Paris Agreement, what strategies might be best adopted for dealing with a “changing climate”³⁷, of which “climate change” is merely one symptom? Indeed, it has been argued³⁸ that the emissions pledges outlined in the Agreement are insufficient to restrain the further global temperature rise to below the ceiling of “well below 2 ^oC above pre-industrial levels” that it stipulates. Indeed, if we are to address the manifold changes that are occurring, in terms of the depletion and deterioration of natural resources - fossil, mineral, water, soil, biodiversity – and the products of their use, e.g. CO₂, it is probably necessary to adapt away from traditional models of economic growth³⁹. It has been argued that various methods of geoengineering might offset the continued emission of CO₂ by human civilization, but these would need to be implemented on a gargantuan scale, e.g. “bio-energy with carbon capture and storage” (beccs), which would necessitate planting tree plantations with a total acreage equal to three times the area of India, and occupy one-third of the arable land on the Earth’s surface, seriously compromising food production. It has been estimated⁴⁰ that achieving a 50% probability of keeping to within the 2 ^oC limit, will require the industrialised nations to reduce their carbon emissions by 8-10% per year, from 2015, reaching a net zero in 2050; in contrast, by the combined effect of increased renewable energy installation, and improved energy efficiency technologies, a mere 4% per year is likely to be possible. It is concluded that this deficit can be dealt with by reduced economic activity, also known as “degrowth”^39,40, with the industrialised countries curbing their economies by 4-6% per year, beginning in 2015, while the poorer nations begin scaling down their economies, in 2025, by close to 3% per year. In short, it implies the end of global capitalism, which depends implicitly on relentless growth.

In a recently published book, Dieter Helm argues that technological adaptations, including the internet of things (IoT) will drive an unabated decline in our use of oil, gas and renewables, and which will be more effective than current efforts to avert climate change⁴¹, as has been reviewed in this journal⁴².The Drawdown project has identified 80 different “solutions”, and more than 20 potential innovations, all with the ability to either reduce carbon emissions or to sequester CO₂ that is already in the atmosphere, and a book has been published about it⁴³. The methods are highly various, and include clean (low-carbon) energy production (including nuclear fission and hydrogen-boron fusion), a kind of seaweed which when fed to cattle reduces their methane emissions, providing education to girls and encouraging family planning, green roofs, high-speed/high-efficiency transportation methods (with reduced energy demands compared with driving or flying), industries based on using recycled feedstocks, ocean farming, farmland regeneration, forest protection, managed grazing and conservation agriculture. Some of the latter concepts are also described in a paper previously published in this journal entitled⁴⁴ “The Imperative for Regenerative Agriculture”, which also emphasises the need for waste minimisation via methods of permaculture and the circular economy. Dealing with the changing climate will involve a climate resilience model which incorporates the inter-connected elements of climate resilience, climate change, adaptability, and vulnerability, as is summarised by the graphic shown in Figure 2. If we define resilience to mean the ability to recover from an adverse circumstance (in the present context, climate change), then it is vital to prepare in advance of the event, and to plan strategies (adaptations) that will enable recovery to be made, and also to identify vulnerable populations that are less capable of devising and putting into action a strategy of resilience. In the above, it is taken implicitly that the impacts of climate change will be detrimental to ecosystems and ecosystem services.⁴⁵

  

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Captions to Figures.

Figure 1. Global CO2 gas emissions in the year 2015 by country.. Credit: Árni Dagur https://upload.wikimedia.org/wikipedia/commons/c/ca/CO2_emission_pie_chart.svg

Figure 2. A graphic displaying the interconnectivity between climate change, adaptability, vulnerability, and resilience; for climate resilience. Credit: Quokka-roo.

https://upload.wikimedia.org/wikipedia/commons/a/ad/Climate_Resilience_Model.PNG

Global Greenhouse Gas Concentrations Highest in 800,000 Years: World Meteorological Organisation (WMO) Report.

Published in the journal, Science Progress  Volume 100 Number 4 2017

The World Meteorological Organisation (WMO) has published its annual Greenhouse Gas Bulletin which reports that in 2016, the global concentration of CO2 had attained its greatest level in 800,000 years (Figure), reaching 403.3 ± 0.1 parts per million (ppm), from 400.0 ± 0.1 ppm in the previous year, which is 145% of pre-industrial levels (i.e. prior to the year 1750,when it stood at 278 ppm). The Bulletin cites data from the US National Oceanic and Atmospheric Administration, which show that there has been an increase in the combined radiative forcing (global heating effect) from all long-lived greenhouse gases by 40% since 1990, which rose by 2.5% in the space of just one year (2015-2016). The report states that [such] “rapidly increasing atmospheric levels of CO2 and other greenhouse gases (GHGs) have the potential to initiate unpredictable changes in the climate system, because of strong positive feedbacks, leading to severe ecological and economic disruptions.” The numbers quoted in the WMO Bulletin are provided by the WMO Global Atmosphere Watch Programme, whose function is to monitor levels of greenhouse gases and provide an “early warning system” for significant changes in these atmospheric gases which are critical agents of climate change.

Ice-core measurements show that the rate at which the atmospheric level of CO2 has grown over the past 70 years is 100 times greater than that which prevailed at the end of the previous ice age. The WMO further notes that, “the steady increase in GHG concentrations in the atmosphere over the observation period from 1970 until present is consistent with the observed increase of global average temperatures in the same period with a record measured in 2016, as reported in the WMO statement on the state of the global climate.”

Combined with a strong El Niño event in 2015 and 2016, emissions from human activities (mainly burning fossil fuels, and changes in land use) have given rise to the observed record increase in atmospheric CO2 concentration, which will urge a yet greater increase in climate forcing. The Secretary-General of the WMO, Petteri Taalas, is quoted as saying:

“CO2 remains in the atmosphere for hundreds of years and in the oceans for even longer. The laws of physics mean that we face a much hotter, more extreme climate in the future. There is currently no magic wand to remove this CO2 from the atmosphere.”

Such high atmospheric CO2 concentrations have not existed since 3-5 million years ago, when the mean global temperature was 2-3 oC warmer than it is presently, with sea levels 20-30 metres greater than now, due to the melting of the Greenland and West Antarctic ice sheets, and part of the East Antarctic ice. Atmospheric greenhouse gas concentrations are a result of the complex interplay between various components of the Earth system, namely the atmosphere, biosphere, cryosphere and the oceans. About a quarter of all greenhouse gases are absorbed by the biosphere and another quarter by the oceans, which therefore act as a buffer to the amounts of them that remain in the atmosphere. Of the other greenhouse gases, both nitrous oxide (N2O) and methane (CH4), reached new record concentrations of 328.9 ± 0.1 ppb and 1,853 ± 2 ppb respectively. Thus, the concentrations of CO2, and N2O have increased to 145% and 122% of pre-industrial levels, with methane showing the most substantial increase, to 257% of its level before 1750. As Mr Taalas has summarised the situation:

“Without rapid cuts in CO2 and other greenhouse gas emissions, we will be heading for dangerous temperature increases by the end of this century, well above the target set by the Paris climate change agreement. Future generations will inherit a much more inhospitable planet.”

This view is reinforced by provisional figures from the WMO which indicate that 2017 is “very likely” one of the 3 warmest years on record, and is likely to be the hottest year in the absence of an El Niño event. The WMO has stated that the average global temperature during January-September 2017 was 1.1 oC higher than in pre-industrial times, and is perilously close to the 1.5 oC threshold believed to be essential to the survival of many island states that are vulnerable to rising sea-levels. The indication is that 2017 is likely to prove 0.47 oC warmer than the average during the period 1981-2010. While it will be necessary for WMO scientists to perform attribution studies to make definite links between the extreme weather events in 2017 and rising temperatures, they believe that the influence of climate change can be seen in such phenomena as temperatures exceeding 50 oC in Asia and the train of hurricanes witnessed in the Caribbean and the Atlantic, earlier in the year. Warmer waters can provide larger amounts of energy to storms, while rising sea levels make the consequent flooding more devastating. 2017 was the first year on record during which two category 4 storms hit the U.S. mainland, while Hurricane Irma was the longest running Category 5 storm on record, where rain gauges in Texas recorded 1,539 mm - another record for a single weather event on the U.S. mainland. In contrast, Africa and South America were severely impacted by droughts and heatwaves. As a consequence, more than 11 million people are currently experiencing extreme food insecurity in Ethiopia, Kenya and Somalia.

The 2016 Nobel Prize for Chemistry, Awarded for: “The Design and Synthesis of Molecular Machines.”

The following commentary will appear in the next volume of the journal Science Progress of which I am an editor. Meanwhile, here is a preview of it.

Jean-Pierre Sauvage, Sir J. Fraser Stoddart and Bernard L. Feringa share the 2016 Nobel Prize for Chemistry¹, awarded jointly to them "for the design and synthesis of molecular machines". A molecular machine, or nanomachine, is any discrete number of molecular components that produce quasi-mechanical movements (output) in response to specific stimuli (input).² This was demonstrated³ in 1983, when Jean-Paul Sauvage managed to synthesise a catenane (Figure 1), which is formed by linking together two ring-shaped molecules by a mechanical bond, a recently coined term to describe the connection between the components of a mechanically-interlocked  molecular architecture such as a catenane or a rotaxane. In order that the molecular machine can perform a specific task, its components must be able to move in relation to one another, as is the case for the two interlocked rings in the catenane.

It was Fraser Stoddart, who in 1991 synthesised a rotaxane⁴, which has a molecular axle threaded through a molecular ring (Figure 2a,b), and demonstrated that the ring could move up and down the axle, leading to such devices as a molecular elevator, a molecular muscle and a molecule-based computer chip. In 1999, Bernard Feringa managed to demonstrate a molecular motor⁵, in which the rotor blade spins continually in the same direction. Using a molecular motor, he managed to rotate a glass cylinder that was 10,000 times bigger than the motor itself. The concept of a “nanocar” has emerged, a version of which was developed at Rice University by the research group of James Tour⁶, and consisted of a molecule with an H-shaped 'chassis' with fullerene groups attached at the four corners to act as wheels (Figure 3). However, since the original device did not have a molecular motor, it might not be regarded as an actual “car”. Feringa and his co-workers have synthesised a molecule with four motorized "wheels" , which they deposited onto a copper surface and used electrons from a scanning tunnelling microscope (STM) to provide sufficient energy that they could drive some of the molecules in a specific direction, in similar fashion to steering a car. As a result of inelastic electron tunnelling, conformational changes are induced in the rotors which propels the molecule over the surface. Since it is possible to change, individually, the direction of the rotary motion in the motor units, either random or preferentially linear trajectories can be attained for the self-propelling molecular 'four-wheel' device. It is believed that it might be possible to produce more sophisticated molecular “cars”, in which a more complete control of the direction of motion can be achieved.⁷

Jean-Francois Morin et al.⁸ are working on a nanocar of the future, fitted with carborane wheels and a light powered helicene molecular motor. However, although a unidirectional rotation was observed for the motor in solution, it has not yet proved possible to drive it on a surface by means of light-energy. A nanocar race event, initially scheduled for October 2016 and described as “The First Ever Race of Molecule-Cars”, has been postponed⁹ “in order to give enough time for the teams to prepare and for the microscope to be optimized. This postponement is essential to make the event a true « sports-science » challenge.”


As yet, the real future for molecular machines is unknown and probably unknowable, but we may note the following, taken from the 2016 Nobel Prize for Chemistry website¹⁰. “The groundbreaking steps taken by Jean-Pierre Sauvage, Fraser Stoddart and Ben Feringa in developing molecular machinery have resulted in a toolbox of chemical structures that are used by researchers around the world to build increasingly advanced creations. One of the most striking examples is a molecular robot that can grasp and connect amino acids. This was built in 2013 with a rotaxane as its foundation.

Other researchers have connected molecular motors to long polymers, so they form an intricate web. When the molecular motors are exposed to light, they wind the polymers up into a messy bundle. In this way, light energy is stored in the molecules and, if researchers find a technique for retrieving this energy, a new kind of battery could be developed. The material also shrinks when the motors tangle the polymers, which could be used to develop sensors that react to light.” Thus, the promise of real-world applications surely glisters.

References.

(1) https://www.nobelprize.org/nobel_prizes/chemistry/laureates/2016/press.html

(2) Ballardini R. et al (2001) Acc. Chem. Res. 34, 445.

(3) Dietrich-Buchecker, C. O., Sauvage, J. P. and Kintzinger, J. P. (1983) Tet. Lett. 24, 5095.

(4) Anelli, P. L.; Spencer, N.; Stoddart, J. F. (1991)  J. Am. Chem. Soc., 113, 5131.

(5) Feringa, B. L. et al. (1999) Nature. 401, 152.

(6) Shirai, Y. et al. (2005) Nano Lett. 5, 2330.

(7) Kudernac, T. et al. (2011) Nature. 479, 208.

(8) Morin, J-F., Shirai, Y. and Tour,  J. M. (2006). Org. Lett. 8, 1713.

(9) http://nanocar-race.cnrs.fr/indexEnglish.php

(10) https://www.nobelprize.org/nobel_prizes/chemistry/laureates/2016/popular-chemistryprize2016.pdf

Captions to figures.

Figure 1. Picture of a catenane, generated from crystal structure data reported by M. Cesario, C. O. Dietrich-Buchecker, J. Guilhem, C. Pascard and J. P. Sauvage in the Journal of the Chemical Society, Chemical Communications, Year 1985, Pages 244-247. Credit: M Stone. https://upload.wikimedia.org/wikipedia/commons/a/ac/Catenane_ChemComm_244_1985.jpg

Figure 2. (a) Graphical representation of a rotaxane https://upload.wikimedia.org/wikipedia/commons/c/cd/Rotaxane_cartoon.jpg Credit: M Stone. (b) Crystal structure of rotaxane with a cyclobis(paraquat-p-phenylene) macrocycle. This  picture was generated from crystal structure data reported by Jose A. Bravo, Francisco M. Raymo, J. Fraser Stoddart, Andrew J. P. White, and David J. Williams in the European Journal of Organic Chemistry 1998, 2565-2571. It shows a rotaxane with a cyclobis(paraquat-p-phenylene) macrocyle. https://upload.wikimedia.org/wikipedia/commons/0/01/Rotaxane_Crystal_Structure_EurJOrgChem_page2565_year1998.jpg Credit: M Stone.

Figure 3. Chemical structure of a nanocar, in which the “wheels” are C₆₀ fullerene molecules.

Attribution: Materialscientist at en.wikipedia https://upload.wikimedia.org/wikipedia/commons/e/ea/Nanocar2.png

Atomic Level Data Storage.

This brief commentary will appear in the next issue of the journal Science Progress of which I am an editor. Meanwhile here is a preview of a fascinating development in computing technology.

There is a growing trend to store more of our data in large data centres using cloud computing resources. Indeed, the amount of data produced by humans increases by more than one billion gigabytes per day. Thus, it is necessary to construct continually more data centres, the running of which consumes large amounts of energy. In order to maintain the capacity of storage media in pace with demand, it is necessary to reduce the amount of space that each piece of information occupies. However, there are limits to how small we can go, due to the roughness of the materials used for data storage, meaning that thousands of atoms are necessary to specify each piece of information. However, if the smoothness of the material could be honed down to the level of individual atoms, it might be possible for each data element to consist of just a single atom. Researchers at Delft University of Technology have achieved precisely this, by placing chlorine atoms on a copper surface, which form a perfect square grid. At particular locations on the grid, there is a chlorine atom missing, leaving a hole. Using the tip of a scanning tunnelling electron microscope (STEM), it is possible to move another chlorine atom into the hole from elsewhere in the grid. A good analogy is with a sliding puzzle, in which small square elements are moved around with a finger, so that the hole is effectively moved around the grid.

Multiple holes can be moved around in precise arrangements to form “bits” (101010, etc), “letters” (ABC, etc), then “words”, to describe eventually an entire text. The Delft researchers have managed to construct an entire one kilobyte, containing 8,000 atomic bits, where each bit is represented by the position of a single chlorine atom. Although there have been previous reports of simple logos, e.g. “IBM” and “2000”, being “written” by towing around atoms molecules on surfaces, this is by far the largest atomically assembled architecture so constructed to date. In addition, the memory also contains atomic-scale markers which render it possible to steer the STM tip through the large array of bits. These markers are of particular importance, since they both mark the start and end of each line, and can furthermore identify the presence of contamination or a crystal defect in a sector of the grid which impede its facility for data storage. Such features are essential if the technology is to be scaled-up further.

The areal storage density of the memory is 502 Terabits per square inch, which exceeds existing state-of-the-art hard-disk drives by a factor of three orders of magnitude. To place this storage density in context, the text of all the books ever written by humans could be written on the surface the area of a postage stamp. In its present form, the memory needs to be kept in an ultra-clean, vacuum-environment and at low temperatures (< 77 K). It is hoped that the relative robustness of the material will enable it to be used outside the laboratory and in practical applications.

Kalff, F.E. et al. (2016) Nature Nanotechnology, Published online 18 July 2016.  doi:10.1038/nnano.2016.131