A guideline for engineers about earth limitations
In 2009, former director of the Stockholm Resilience Center Johan Rockström led a group of 28 internationally renowned scientists to identify the nine processes that regulate the stability and resilience of the Earth system. The scientists proposed 9 quantitative planetary boundaries:
Crossing these boundaries increases the risk of generating large-scale abrupt or irreversible environmental changes. Since then the planetary boundaries framework has generated enormous interest within science, policy, and practice. Over the course of 10 lectures, international experts will introduce the audience to the concept of the 9 planetary boundaries within which humanity can continue to develop and thrive for generations to come.
Sarah Cornell from the Stockholm Resilience Centre
On 12 October 2021, the online lecture series dedicated to the topic “Planetary Boundaries” was kicked off by the introductory lecture of Sarah Cornell, Associate Professor in sustainability science at Stockholm University. Sarah Cornell works as a Principal Researcher in the Stockholm Resilience Centre, an internationally influential research centre that seeks to advance the scientific understanding of the complex, dynamic interactions of people and nature in the biosphere. Her research background is originally in global biogeochemistry, extending over the years to also address the study of human dimensions of global environmental change. Sarah Cornell is part of the researchers’ group of international interdisciplinary scientists, who have developed the Planetary Boundaries framework in 2009 and continuously work on improving it. Laying the framework for the lecture, Professor Cornell explains that she sees the world as earth system, as interaction between land, ocean, atmosphere and life and how human life perturbates this system. As she points out, planetary boundaries describe different features of earth system change as it departs from these relatively stable conditions. The planetary boundaries framework identifies nine processes of the earth system, which are interlinked. The nine planetary boundaries are:
The Resilience Centre, where Professor Cornell works, sees the world in terms of interconnected systems, taking a look at processes of change but also processes of resilience – ways in which to deal with these changes. Explaining the lecture’s starting point, Professor Cornell says that it is already a known fact, that people are changing the environment intentionally, but sometimes these changes have unwanted consequences. The more humans change the climate, the more unpredictable it becomes. Similarly, we reduce the biodiversity or, as Professor Cornell calls it, ‘the livingness’ of the planet. According to the planetary boundaries framework, within these boundaries, humanity can operate safely. While crossing them leads into the zone of uncertainty and increased risk, transgressing them further will lead beyond the zone of uncertainty into the zone of high risk. Transgressing one or more planetary boundaries may trigger irreversible and unstoppable environmental changes. The related social message transmitted by Sarah Cornell is, the more we undermine the living processes of the earth, the less resilient the planet becomes to the changes we impose upon it. Her inspiring lecture gave an overview over the background of the framework as well as an outlook, what its message means for today’s and tomorrow’s life.
Arnulf Grübler from the International Institute for Applied Systems Analysis
On 19 October 2021, the online lecture on the first planetary boundary, Climate Change, was held by Professor Arnulf Grübler from the International Institute for Applied Systems Analysis (IIASA).
Arnulf Grübler is Emeritus Research Scholar and former Program Director of the Transitions to New Technologies Program at the International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria. From 2002 to 2017 he also held a part time appointment as Professor in the Field of Energy and Technology at the School of Management and the School of Forestry and Environmental Studies at Yale University, USA. Since 2020 he is Honorary Professor at Montanuniversität Leoben, Austria. He is also foreign member elect of the Russian Academy of Natural Sciences. Prof. Grübler’s research and teaching focuses on the long-term history and future of technology and the environment with emphasis on energy, transport, and communication systems, as well as climate change and sustainable development. Professor Grübler started off his lecture discussing the question why there is a planetary boundary on climate. He stated that humanity blossomed during a period of very stable climate – the Holocene. Human activities have been significantly changing the climate, however the consequences of those changes are not immediately noticeable but unfold over several decades, even centuries into the future. He also pointed out, that the rate of change is unprecedented. On that ground, science aims to define quantitatively a ‘ceiling’ for climate change in response to the policy objective agreed in the Framework Convention on Climate Change in 1992: “to avoid dangerous anthropogenic interference with the climate system”. This is the context in which the climate planetary boundary has been developed. Professor Grübler went on discussing the question of why does climate matter? The natural greenhouse effect makes life possible at all on earth, which Professor Grübler illustrated by comparing Earth to Mars and Venus. Significant changes in the Earth’s climate thus risk to undermine the basic life support capability of the planet. After a detailed technical part on how data is collected reconstructing historical climate records from air bubbles enclosed in ice cores, atmospheric CO2 concentration measurements on Hawaii and radiative forcing change, as evidence of human induced climate change, Professor Grübler went on to illustrate the history of the Climate Planetary Boundary: A first climate change ceiling (or boundary) formulation (below 2 °C change over pre-industrial times) dates back to the 1978 Villach UN Climate Conference. In 1992 a traffic light system evaluating sea level rise and temperature change was introduced, followed in 2001 by the Burning Embers concept of IPCC with an update in 2009, outlining 5 risk categories. In 2009 the planetary boundaries concept was introduced, where the climate boundary is defined by two variables: maximum CO2 concentration (now 350-450 ppm, originally 350-550 ppm) and changes in radiative forcing since ca. 1900 of maximum 1-1.5 W/m2. Professor Grübler closed his presentation by reflecting on the remaining CO2-budget to stay within the climate planetary boundary, possible mitigation options, and their actors and sustainability benefits.His presentation sparked vivid discussions in the Q&A part, among other topics on the effect of coal-related emission
Gretchen Daily from Stanford University
On 27 October the series continued with the lecture on Change in Biosphere Integrity. Gretchen C. Daily is co-founder and Faculty Director of the Stanford Natural Capital Project. Founded in 2005, the Natural Capital Project (NatCap) is a global partnership whose goal is to integrate the values of nature into planning, policy, finance, and management. Its tools and approaches are now applied in 185 nations through NatCap’s free, open-source InVEST Software Platform. Daily is the Bing Professor of Environmental Science in the Department of Biology at Stanford University, the Director of the Center for Conservation Biology at Stanford, and a senior fellow at the Stanford Woods Institute for the Environment. Daily’s work is focused on understanding human dependence and impacts on nature and the deep societal transformations needed to secure people and Earth’s life support systems. Her work spans fundamental research and policy-oriented initiatives to open inclusive and green development pathways. She co-develops pragmatic approaches, engaging with governments, multilateral development banks, investors, businesses, farmers and ranchers, communities, and NGOs. Professor Daily opened her lecture by stating that humanity has been deeply embedded in the biosphere throughout history. “We are utmost dependent on nature. In modern life this dependence has become partly hidden”. The aim of her work is to shine a light on it, transforming the way how we actually make decisions from a narrow cost-framework to considering nature’s vital benefits. The central term of her work/lecture is ‘natural capital’, which is lands, waters and biodiversity. Professor Daily’s lecture revolved around practical case examples on ‘natural capital’. One of those stories was the history of Costa Rica. In the 1990s, Costa Rica had the highest deforestation rate on the planet. Then the government pioneered the world’s first-ever national Payment for Ecosystem Services, paying people to protect and restore forest, considering its values for climate security, water security, pharmaceutical development, and eco-tourism. Since then, the country is a model for the world, with net reforestation. It continues today to move towards policies that harmonize people and nature – securing natural capital in the country. Staying in Costa Rica, she gave another practical case of how natural capital was translated into concrete values, this time the value of biodiversity to farmers through productivity of coffee plants in different proximities to rainforest. Results showed that coffee plants close to forest had higher bee diversity, abundance, and pollination services – and higher yields. The value of biodiversity in this case could be translated into concrete amounts of dollars per year. She also told about another experiment in a very different setting on the impact of nature experience on mental health. In that experiment, people took tests, were sent to take a walk either on a street with heavy car traffic or on a forest road, and then took the tests again. The people who had been walking in the forest did significantly better in the test – with higher cognitive functioning and emotional well-being – while people who had been walking on the street didn’t improve. The experiment demonstrated how small doses of nature can improve working memory and mood and decrease anxiety and rumination. The closing Q&A session showed how this topic is important and current to many people from all parts of the world.
Robert Jandl from the Austrian Forest Research Center
The third module of the Planetary Boundaries series regarding Land-System Change was held on November 3rd by Robert Jandl, who is a forest ecologist from the Austrian Forest Research Center. His interests are carbon storage in Austrian forest ecosystems, and appropriation of land at the expense of agricultural and forest land. Currently, he is co-chairing an Assessment Report on Climate and Land Use in Austria. Robert Jandl dedicated his lecture to the topics land use and land use change in context of climate change. He opened up with the IPCC report on climate change and land of 2019, the key message being that there are many land related climate change mitigation options. Diving deeper into the topic, he explained that there is a triple challenge of land use: land is under growing human pressure, generating significant amounts of greenhouse gases by the way land is used. Having said that, he stated that land is part of the solution. Land use has climate change mitigation power, but is only one factor out of many. As climate warming continues, farmers and foresters have to adapt to the consequences of the warming trend. In order to prepare, different climate change scenarios are used.´Robert Jandl then went over to analyze the current situation of global land use: 75% of the ice-free land are under some form of land-use. On one quarter of used land, land cover change has been taking place, e.g. deforestation. The largest land use category is grazing land, followed by forestland and cropland. Taking a closer look at land use in Austria, it can be noted that Austria is one of the European countries with most forest cover. An important topic to be discussed in this context is soil protection, or in other words, the avoidance of soil sealing. Austria has the reputation of being the European champion of soil sealing. Considerable land development has been going on. The conversion of productive land to sealed land leads to a loss of soil functions and among those the climate change mitigation function. Soil has also to be looked at as a limited resource in the context of food production. Partly, valuable potential cropland is used as sealed ground. Another trend to be observed in Austria is the increase of forest area. This increase is largely due to agricultural policy, the decision of land owners to discontinue agricultural land use. Robert Jandl continues to discuss a further trend in Austria. As he explains, the expansion of settlements is reflection of a prosperous society being expressed in a higher demand for living space and partly higher population. Regarding soil appropriation in AUT, soil sealing has been decreasing and is a recognized political problem, but far from being resolved. Looking at global trends of land use change, Robert Jandl points out high deforestation rates in e.g. Brazil, parts of western Africa, Indonesia while in e.g. China the results of afforestation programs are to be observed. Robert Jandl closed his lecture with a statement on emissions of greenhouse gases. Land use und deforestation are causing CO2 emissions, but the emissions deriving from fossil fuel burning are the far bigger problem.
Jonas Bunsen from Technische Universität Berlin
The fifth lecture of our Planetary Boundary series took place on November 9th and was dedicated to the topic Freshwater Use. The lecture was held by Jonas Bunsen, who is a scientist at the Chair of Sustainable Engineering at the Technical University of Berlin where he works on environmental impact assessment with a particular focus on water. He previously worked in public policy consulting at the think tank “adelphi” and in Life Cycle Assessment consulting at “Greendelta”, both located in Berlin, as well as for short term assignments at the KWR Watercycle Research Institute in the Netherlands and a branch of the International Water Management Institute in India. Jonas Bunsen holds a MSc in Water Science and Management from the University of Utrecht in the Netherlands and a BSc from the University of Innsbruck in Austria. Jonas Bunsen started his lecture by pointing out that fresh water on planet Earth is not as abundant as one might think and particularly not evenly distributed. He continued with a general introduction to the planetary boundary Freshwater Use. The defined control variable is blue water consumption (fresh ground and surface water), which was considered by the authors of the planetary boundary Freshwater Use to potentially affect regional climate patterns, biomass production and consequently carbon uptake. Therefore, these processes are potential corresponding response variables. As Jonas Bunsen points out, the planetary boundary Freshwater Use has been criticized from early on for comparing a local resource with global thresholds. On a global scale, this boundary is declared as not yet exceeded, but locally there are regions where water is already extremely scarce and people are suffering from water shortages. Moreover, blue water is also just one type of water consumption (disregarding e.g. indirect water consumption through land-use change and corresponding changes in evapotranspiration or water pollution), which has also been criticized to be one of the shortcomings of the planetary boundary concept, as well as dynamic thresholds and local tipping points. He gave an example for the latter: The Aral Sea shrank to 10% of its size, which has been called the “largest man-made water related catastrophe”, and still consequences have largely materialized on a regional scale. Jonas Bunsen went on to show how a planetary boundary Freshwater Use has been put into practice, giving two examples of assessment methods: Life Cycle Assessment (LCA) and Input-Output Analysis (IOA). LCA aims at mapping all production steps and corresponding inputs and outputs flows of a product life cycle, in order to evaluate potential environmental impacts. For the LCA, all flows which enter (inputs) and leave (outputs) the product system are listed and then grouped per respective impact category (e.g. climate change, water consumption). He explained the method IOA by a case study example regarding Germany’s (in)direct water consumption. The study’s aim was to determine national German water consumption and then allocate the national water consumption to watersheds worldwide and benchmark against local water consumption boundaries. Bunsen and his colleagues calculated that, for Germany, 86% of the whole yearly water consumption is consumed abroad, considering consumers supply chains. As Jonas Bunsen pointed out, it is a model with approximate numbers, but an effective tool to identify local hotspots, where measures would have most leverage power. He closed his presentation with a recent proposal on the water planetary boundary, which argued that water fulfills various functions in the earth system. Based on those core functions, six subboundaries (e.g. frozen water or soil moisture) with different response variables were proposed. Apart from frozen water, all are assigned to different spatial scales. As Jonas Bunsen finally concluded, the scientific community has moved to sub-global (regional) thresholds for assessing the impact of water consumptions as it can be questioned, if a planetary boundary for water really makes sense.
Thomas Prohaska from Montanuniversität Leoben
Module 5 of the Planetary Boundaries series regarding Biochemical Flows was held on November 16th by Prof. Thomas Prohaska, who has been Chair for General and Analytical Chemistry at Montanuniversität Leoben since 2018. He studied technical chemistry at the Vienna University of Technology and received his PhD with summa cum laude in 1995. In the same year, he became a scientific researcher at the University of Natural Resources and Life Sciences (BOKU), Vienna and was in charge of setting up a laboratory for elemental and isotopic analysis. From 1998 to 2000, he was a researcher at the EC joint research center IRMM in Geel, Belgium. He was an associate professor at BOKU until 2018 before moving to Leoben. His current research focus is based on elemental and isotopic analysis using mass spectrometry, chemical imaging techniques and metrology with applications in geo-, environmental and life sciences. He is the author of more than 150 peer-reviewed publications. He opened his lecture by indicating that the biochemical or biogeochemical cycles are a critical topic within the planetary boundaries. As he explained, aside from biodiversity, it is one of the major problems with a massive impact on our planetary system. He started to dive into the topic by explaining what stands behind the topic and argued that it is also necessary to understand that planetary boundaries are interlinked: Elements like nitrogen influence land system change, fresh water use, etc. Talking now about biogeochemical flows, we always refer to cycles. Within cycles, there are various flows, circulation of chemicals, within different spheres of our planet. All of those spheres are interlinked and chemicals transform in the cycles permanently. Professor Prohaska explained this process using the example of nitrogen, which when in the atmosphere is different from nitrate, for example, which still contains nitrogen but in a different molecular composition with different chemical properties. Biogeochemical cycles connect energy and chemicals on the planet into continuous loops, which happen on different scales, from global to regional to microbial. In the biochemical cycles, the major focus is on “basic building blocks of life”: hydrogen, oxygen, carbon, sulphur, nitrogen and phosphorus. Professor Prohaska pointed out that a significant and increasing number of elements is to be considered. Professor Prohaska continued explaining the cycles of specific elements (nitrogen, phosphorus, silicon, oxygen and the hydrological cycle) in more detail, concluding how interlinked the cycles are, giving an idea of how fragile and vulnerable they are. If one cycle for a specific element is changed, other cycles are impacted as well. The major anthropogenic impact is excluded in the cycle studies, but when the reality of the cycles is considered, this impact has to be taken into account. In the lecture, the participants were given the opportunity to discuss the anthropogenic impact in the context of biochemical flows on carbon, phosphorus, nitrogen, water and rare earth elements in breakout rooms. An example of some of the findings of the discussions is that the production of fertilizer leads to over-nitrification in some parts, meaning that too much nitrogen is released into the environment. Also concerning phosphorus, he called attention to the fact that humans break the natural phosphorus cycle, mining phosphor to bring phosphate as fertilizer to the field, causing a significant run-off and losing a lot of phosphorus in waste. Recycling of phosphor has received significant attention recently, so technology can be part of the solution. We currently find ourselves in the red zone of the planetary boundary for nitrogen and phosphorus, largely due to agriculture. Professor Prohaska ended his lecture with a call to the audience: “Trying to find a safe operating space for humanity, it is up to us – with the right tools and the right attitude. We need to rethink and commit ourselves to taking over responsibility.”
Marinella Passarella from the Resources Innovation Center Leoben
The 6th Module of the Planetary Boundaries series to the topic Ocean Acidification took place on November 23rd and was held by Dr. Marinella Passarella, who is the Climate Portfolio Manager and Researcher at Montanuniversität Resources Innovation Center, where she coordinates the Climate Actions team and agendas as well as the EIT Climate-KIC partnership of the university. Her work consists of the expansion and management of projects portfolio for tackling climate change through innovation and education. She has a background in Physical Oceanography and Meteorology. On this topic, she obtained an Honours Bachelor of Science at the University of Naples Parthenope (Italy) and attended several oceanographic research campaigns. Sustainability and climate change mitigation have been always important to her as she specialized in renewable energy achieving a Master of Science with merit in Marine Renewable Energy at the University of Plymouth (UK). She worked as a member of the steering group of the non-profit organization INORE (International Network on Offshore Renewable Energy). During her research career, she obtained an International PhD in Innovation Science and Technology devoted to Systems and Methods for Environmental Protection at the University of Cagliari (Italy). She opened her lecture by raising the question of why the ocean is important. She continued to give the answer, that marine organisms (e.g. seaweed) produce over 50% of the oxygen, that land animals currently need to breath. As she points out, oceans also provide other highly important ecosystem services e.g. carbon capture or climate regulation. Elaborating on the ocean’s climate regulation role, she explains that ocean and atmosphere circulations work to equilibrate Earth´s temperature gradient. The redistribution of heat is crucial in climate regulation, vice versa the climate warming also affects these processes, as the oceans temperatures also increases and CO2 dissolves better in cold water. This argument brings us to the next important function, which oceans fulfil: the carbon capture role of oceans. As the attentive audience learned, a rise in atmospheric CO2 leads to decreasing ocean pH – ocean acidification. Oceans absorbed around one third of CO2 emitted by fossil fuel burning, deforestation since industrial revolution etc. The absorbed atmospheric gases change the chemistry of sea water. She continues to explain the consequences of ocean acidification on sea life: many marine organisms need aragonite or calcite to build their shells, and the acidification of the ocean leads to undersaturation of those elements. Further biological impacts would be e.g. loss of phytoplankton affecting also bigger animals, stressed corals etc. Some of these consequences were considered by the planetary boundary framework. According to Rockström et al. (2009;2015), we are approaching the uncertainty zone (80%-70% of pre-industrial saturation state of aragonite of surface water). It is also to be noted, that there is a close interlink between this boundary and the climate change boundary, whose control variable is atmospheric CO2 concentration. Dr. Passarella took the audience on a dive into an acidifying ocean by means of a google art experiment, which again illustrated the consequences of the changes imposed by humanity. She followed up with the question of what we can do, outlining the several engineering approaches to mitigate ocean pH change, which can be divided in two main categories: preventing CO2 emissions in the first place or mitigating the emitted CO2. The latter can be done either via carbon capture storage or addition of alkalinity to the oceans, approaches which however have been assessed by the existing research literature, to be only partially effective and with potential critical negative environmental effects. Concluding then, that the first option of CO2 emission prevention is the recommended one. In order to show the reality to the theory, Dr. Passarella presented three case studies, among them one on marine renewable energy (e.g. offshore winds, wave energy), ending on the positive note of what can be done for our oceans.
Mihalis Lazaridis from the Technical University of Crete
The 7th Module regarding Atmospheric Aerosol Loading was held by Prof. Mihalis Lazaridis on Novemer 30th. He is professor of air pollution at the Technical University of Crete. He studied Physics at the Aristotle University of Thessaloniki and got his PhD from the University of Helsinki. He worked in the Joint Research Centre of EU, the University of Rutgers and Harvard, and the Norwegian Institute for Air Research. He has management experience in various national and international research projects and extensive work experience in modelling of physico-chemical processes in the atmosphere, modelling of human exposure and dose from air pollutants, indoor air quality and measurements of air pollutants. Prof. Lazaridis started his lecture by giving a definition of what aerosols are: Suspensions of solid or liquid particles in a gas. As he continues to explain, in order to characterize aerosols, one has to take a look at parameters such as size, shape, density. Size ranges from nanometer scale to several hundreds of micrometers – if they are bigger, they would not be characterized as aerosols anymore. These two categories have different origins, while fine particles come from gaseous to particulate phase reactions, coarse particles result from sources like sea spray or suspended dust from roads. When studying particles, the concentration (which depends on size) is of main interest, although it is interesting to note, that EU regulations only look at mass as a regulatory parameter. Another topic to be looked at is the aerosol chemistry. As Prof. Lazaridis explains, aerosols consist of different chemical compounds. When looking at atmospheric aerosols, it is important to understand that particles can be emitted primarily as aerosols, or be formed secondary from gaseous phase. Particles are “a whole world not visible to us”: the biggest particle is close to one tenth of the diameter of our hair. He went over to discuss aerosol sources, which can be either natural (e.g. soil dust, volcano eruptions, sea salt etc.) or anthropogenic (industrial or vehicular emissions etc.). The latter count for approx. 10 % of all aerosols. As he explains, aerosols can have an effect on climate, e.g. in case of a volcano eruption. The aerosols caused a mid-temperature decrease, showing that aerosols have an opposite effect compared to gases like methane. Mineral dust decreases temperature while black carbon increases it. Aerosols also may lead to limited visibility (e.g. looking at Sahara dust). The dust has a radiative effect on climate and can also have a negative effect on humans’ health. Another important point to consider when looking at how aerosols affect climate is their lifespan. Life time of aerosols is short in the atmosphere (max. some weeks), while carbon dioxide lifetime expands to many years in the atmosphere. The above described considerations are put into practical use through different applications. Tools and mathematic models make it possible to evaluate and demonstrate the probability of exceedance of air quality limits for a specific pollutant (e.g. PM10, which are particles that have 50% cutoff at 10 microns). Prof. Lazaridis presented a case study, where fine particle number size distribution and PM10 concentration at Chania and the impact from local and regional sources were measured. The study showed higher particle concentrations in winter related to heating emissions and peaks during the day in rush hour and enforced heating periods in the evening. It could also be observed, that wind direction and meteorology as well as wind speed have an impact. Another interesting point to note was the transboundary emissions. Dust originated in Africa can significantly influence air quality, thus demonstrating that air pollution is not only a local topic.
Ulrike Langematz from Freie Universität Berlin
Module 8 of the Planetary Boundaries series concerning Stratospheric Ozone Depletion took place on December 7th and was held by Ulrike Langematz. She is University Professor for Atmospheric Dynamics at Institute of Meteorology at Freie Universität Berlin, where she also studied Meteorology herself. She had various visiting professorships at University of Arizona (2002) and University of Melbourne (2016/17) and spent research periods at NIWA New Zealand (2009), University of Kyoto and Meteorological Research Institute of Japan. Her research areas are physics, dynamics and chemistry of the middle atmosphere, stratospheric ozone, atmospheric impact of solar variability, chemistry-climate modelling and paleoclimate. Her publication record encompasses about 90 peer-reviewed publications. She also is Lead Author of the WMO/UNEP Scientific Assessment of Ozone Depletion 2018 and Co- Author, Contributing Author and Review Editor of the WMO/UNEP Scientific Assessment of Ozone Depletion 2003, 2007, 2011, 2014, 2022. Prof. Langematz started by locating the Stratospheric Ozone Depletion boundary within the planetary boundary framework in the safe zone, while pointing out at the same time that this was not the case some decades ago. In order to create the foundation/base for this lecture, Prof. Langematz explained that ozone is a form of oxygen (3 oxygen atoms). 90% of the ozone are to be found in the stratosphere and only 10% in the troposphere. As the overall number of ozone molecules in the atmosphere is not high, Prof. Langematz raised the question of why is it important then? As she continued to explain, it is necessary to distinguish between “good” and “bad” ozone. Ozone is a toxic gas, which should not be found in big amounts close to earth’s surface. The good ozone absorbs the harmful solar radiation in the ozone layer. There are different methods to measure ozone, most used are ozone sondes, further important methods use remote sensing via satellites or high-altitude aircrafts, or ground-based remote sensing like spectrophotometers or lidars, which work by looking upwards and measuring reflected radiation. When studying the distribution of ozone in the stratosphere, two major processes have to be looked at: The first is the photochemical production and destruction cycle (Chapman Cycle). Three oxygen molecules are converted into two ozone molecules, but then interact with sunlight and are reconverted in oxygen molecules. A second destruction process occurs when there are additional chemicals in the atmosphere (e.g. chlorine) which also react with ozone molecules and lead to its destruction. One chlorine atom can destroy thousands of ozone molecules – the ozone layer depletion is a result of both the Chapman cycle and catalytic ozone destruction by reactions with ODS (ozone depleting substances). Another important aspect regarding the ozone distribution is the circulation. Ozone is usually produced in low latitudes, where there is a lot of sunlight, but by circulation ozone is transported to high latitudes in winter. Prof. Langematz continued to explain the evolution of the ozone layer over the past decades. Stratospheric ozone has decreased in the 1980s and 1990s, which is measured in the unit of total ozone (describing the ozone column above a certain point, expressed in Dobson Units, the global average being 300 DU). The global total ozone changes show, that decrease has stopped in 1990s, but the current value is still below the average of 1960-1980. Why did it decrease? Catalytic ozone destruction has become stronger, because large amounts of halogen gases have been emitted in the atmosphere by anthropogenic activities. The industry has produced CFCs since the 1950s, which were then transported into the stratosphere where the chlorine and bromine containing source gases are converted to reactive halogen gases by solar radiation and act as ODS. The Antarctic ozone hole is the most dramatic manifestation of ozone depletion. All described above refers to the whole earth, but over Antarctica there is a special situation. The ozone hole is not a real hole, but an ozone minimum which occurs every spring time over Antarctica (total ozone in this area is below 220 DU), as discovered first by three British scientists in 1985. This situation is due to special meteorological conditions in Antarctic winter, where it is very cold in the stratosphere, much colder than in the Arctic. In those low temperatures polar stratospheric clouds can be produced, being the prerequisite for additional ozone depletion. Heterogenous chemical reactions then take place, releasing chlorine which in spring reacts with the solar radiation causing catalytic ozone destruction. Only in Antarctic winter temperatures are low enough for sustained heterogenous ozone destruction, there is no similar ozone hole in the Arctic. Talking about future ozone recovery and the evolution of ODS, Prof. Langematz pointed out, that it is a success story. After the first publications on the effect of ODS were published in the 1970s and 1980s, it didn’t take long until action was taken to avoid further decrease of the ozone layer. It was not only the Montreal Protocol 1987 (international agreement to reduce the abundances of ODS in the stratosphere), that led to this success. The initial protocol was easily and quickly amended, as it was soon clear, that it was not sufficient. For tendency surveillance, there is a report published every four years, which evaluates if the ODS goes down. A special type of model (chemistry-climate models) is needed, to predict ozone increase or decrease. According to these predictions, ozone is projected to reach 1980-baseline values again at about middle of this century. Satellite measurements, aiming to detect ozone recovery, show a positive trend in total column ozone locally, but it is not significant yet. These trends are difficult to observe, because of the factors (ODS effect and the year-to year variation determined by dynamical activity) controlling the polar zone. Another region, requiring special attention of atmospheric researchers like Prof. Langematz concerns the tropical ozone. Here an increase until the 2060s and then a decrease are projected, which is due to increasing upwelling in the Brewer-Dobson circulation because of climate change. This has consequences for the UV radiation as well, which will then increase and probably suppose health risks in the tropics. Another consequence of the climate change and increased dynamics is that more ozone will be transported from the stratosphere to the troposphere, which might also become a problem in the future, if ozone gets too close to the surface. At the end of her presentation, Prof. Langematz touched on current ozone topics, such as the recent non-compliant CFC11 production coming from China, which only went over a limited period, and will not lead to a substantial delay in Antarctic ozone recovery, proofing the importance of ozone monitoring. She also mentioned potential new threats for the polar ozone layer: Supersonic and hypersonic transport in commercial use are expected to release substantial amounts of water vapor and nitrogen oxide into the stratosphere which would cause a significant ozone decrease. Summary: the emission of anthropogenic ODS has led to severe global depletion of stratospheric ozone since about the 1980s by chemical processes. In combination with the specific dynamical conditions (cold, stable polar vortex), the Antarctic ozone hole regularly develops since the 1980s. In a resolute and joint action of politicians, scientists and industry world wide the production and consumption of ODSs was banned by the Montreal Protocol in 1987 and its amendments and adjustments. First signs of ozone increases are detectable since about 2000. Models project a recovery of global and polar ozone to 1980 baseline values during the 21st century. No complete future tropical ozone recovery is expected in the lower stratosphere due to an increase in the Brewer-Dobson circulation. If you will be in a position one day to take decisions – do it. The montreal protocol example and success story of the ozone recovery was such a success because of resolute acting and could not be repeated yet for the climate change problem. So if you have the possibility, be resolute and take the decisions that are necessary.
Vivian Feng from Augsburg University, MN
On January 18th the last lecture of the Planetary Boundaries series with the topic Introduction of Novel Entities took place. The lecture was held by Vivian Feng, professor of Chemistry, and an affiliated faculty of the Environmental Studies program at Augsburg University in Minneapolis, MN. She received her B.A. degree in Chemistry from Linfield College (OR), and her PhD in Analytical Chemistry from the University of Illinois. After initiating her career as an Assistant Professor at the University of Puget Sound (WA), followed by a Research Educator position at the University of Texas, she started her current position at Augsburg University in 2008. Besides teaching analytical chemistry and general chemistry, Vivian enjoys teaching the highly interdisciplinary courses in Materials Chemistry, and Environmental Sciences. She leads an active undergraduate research lab at the interface of bioanalytical and materials chemistry. She applies analytical tools to probe the interactions at the nano-bio interface to better understand the environmental fates of novel nanomaterials. Her lab, a part of the NSF Center for Sustainable Nanotechnology, investigates the impact of nanomaterials to biological models, such as bacteria or model membranes. Introducing the abstract topic of novel entities, Prof. Feng began her lecture by showing how nanomaterials are part of various areas of our lives. The aim of her lecture was to show the two sides of novel technology, how it can help to improve environmental sustainability but at the same time may create new challenges. Pursuing that goal, she dedicated her lecture to the topics of Nano EHS (environmental health and safety research related to nanotechnology), analytical detection and characterization, monitoring transformation, assessing biological impacts and current applications to address environmental issues. As she went through those topics, she also went from molecular to bigger organisms to model systems (mesocosm model studies). As Prof. Feng explained, nanomaterial has been used in a variety of commercial products, whether we are aware or not. Some examples: Titanium oxide in food coloring, silver or copper nanoparticles in antimicrobial fabric like socks, zinc oxide in sunscreen, metal oxides in lithium-ion batteries). Nanomaterials have impacts in modern lives: agricultural uses, consumer electronics, water purification and energy storage, biomedical applications, etc. She put the topic of novel entities in perspective, explaining that we have been here before: A new product with new properties is being developed. This imposes the challenge of how to make sure that the applied test methods evaluate these new materials appropriately. There are lessons we should have already learned from introduction of new materials to the world, e.g. of some formerly new materials we know now harm either humans or fauna and flora. Nano particles are a broad category and the experimental design depends on questions, which shall be answered. In the multidisciplinary field of nano-EHS two approaches are important: the chemists’ bottom-up approach from molecular level and the top-down approach from biosphere level of engineers. There are various challenges Nano EHS research faces and aims to tackle: Detecting ENMs in biological and environmental matrices, predicting the environmental fate of nanomaterials, assessing the hazard of these materials in organisms, developing quantitative risk assessments. Prof. Feng went on to discuss the classification of toxicity-inducing nanomaterials, rounding up the topic of the scope of Nano EHS and continued with environmental transformations and biological impact before she came to discuss mesocosm model studies. She showed a case study, where a mesocosm model of wetlands etc. was built to mimic environmental reactions. As she points out, those models are important because nobody would want to dump unstudied materials in the real environment. The goal of this type of research is to look at low dose and long-term effects. In the given case study, they looked at the effects of Kocide (a copper-based nano fungicide, used in agriculture) and a gold containing nanomaterial in this mesocosm system. They learnt in their study, which was conducted over a year, that the copper oxide, being quickly soluble and mobile, was transferred to deeper aquatic sediments and existed in natural chelated forms. In the gold case, as gold doesn’t dissolve easily, which is why over time it was transferred either in the plant of the surfical sediment and reduced. Prof. Feng continued to give an overview over the state of the field. For detection of nanomaterials, an orchestra of instruments which allow in-situ measurements of in-situ conditions exists. Over the last 20 years, a deeper understanding of environmental nanomaterial transformation was developed, but as she explains, there still is a lack information on those dynamic transformation processes. Furthermore, in assessing hazard, there is also a need to focus more on molecular level changes to evaluate dosage levels which are environmentally relevant, in order to be able to fill the gap on sublethal endpoint studies. Before going into a lively discussion, Prof. Feng dedicated the last part of her presentation to some highlights of nanomaterial applications, which don’t harm but enhance environmental conditions, benefitting the environment and solving environmental issues. The three fields she gave an overlook about were food production, water treatment and energy. Looking at nano agriculture: copper oxide as fungicide was mentioned earlier as example, nano materials in agriculture are a booming field, being implemented as fertilizers, pesticides, battling diseases etc. Also, nanosensors are being developed, so that the plants can tell you, when they are ill. Modern agriculture is dependent strongly on fertilizers. The idea of some fields of nanomaterial research here is to reduce the chemical load in agriculture and consecutively in food. Nanomaterials are also beneficially and actively used in water treatment e.g. to selectively and efficiently remove unwanted components or to capture moisture in air to provide very dry areas with drinkable water or in air filters using electrospray polymer nanofibers, resulting in high airflow and efficient removal of particles PM10 and PM2.5. She went on to look at the energy sector, discussing the example of lithium ion batteries and posing the question of their after-life at the end of the life-cycle in the topic of electric car vehicles. As she laid out, currently the regeneration of some of these materials is being studied, but currently we also lack of the necessary infrastructure for regeneration. At the end of her insightful lecture, Prof. Feng recapped: Humanity in different epochs were labelled by the materials they used (e.g. stone age, iron age…), which led to the question of how do we define today’s age? Are we in a polymer or nano age? We live with and rely on novel entities and there is no way to go back to the iron age. But scientists are working on and will need to continue working on closing the loop, the life cycle of these materials, in order to lead us in a more sustainable future.