Climate Change - Present Status & Future Prospects: Talk at WES (Scotland)

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 It was a pleasure to talk to the Scottish branch of the Women's Engineering Society on Sunday 31st August about Climate Change - where we are just now and what might be happening in the coming decades?  In the following, I am publishing the slides used for the talk with some minor additions.  Virtual meetings provide welcome break from the isolation created by Covid-19; I believe that this is a great way to communicate science in the community and I hope to use this medium much more in the future. 

The slides form the complete talk.  Commentary between the slides provides further explanation and the links are generally to websites where more detailed discussion of the topic is available.

Please click on a slide to see its full page image

 Slides:

Often people are confused about the difference between weather and climate.  Weather at a particular location describes atmospheric conditions at an instant in time and is highly changeable, while climate is the mean conditions over a long period of time and refers to an extended region.  For details click here. 

The indicators point to a warming world. For example, water expands when heated.  An increase in the sea surface temperature will result in increased volume of water, and sea levels will rise. Similarly global warming will result in a loss of ice in the Arctic Ocean and from the ice caps on mountains where ice will melt due to higher temperatures. Note that mountain ice-melt provides fresh water for drinking and irrigation to a large fraction of the world population and if these glaciers eventually disappear then it will be catastrophic for people downstream - it is expected that by the year 2100, the glaciers in the Himalayas will be reduced to one third of their present size - 2 billion people depend on the fresh water from the glaciers. 

For a detailed discussion of the loss of biodiversity, please click here.

The rate of population increase has dropped considerably in recent years, and it is expected to fall to 0.1% annual increase by the year 2100.  That still means that the population will double every 700 years and could reach more than 20 billion by the year 3000. One has also to deal with all the problems created by inverted population pyramids etc!

While the rich countries caused most of the emissions, the fast developing economies of China, India, Brazil and others are consuming resources at a higher rate than before - these countries represent a much larger population block and it seems unlikely that consumption and hence emissions will start to go down anytime soon.

While solar and wind are the most promising alternative energy technologies just now, and they have helped to cover the additional global energy demand of the past decade, it is difficult to see how they can replace fossil fuels to meet the full global  energy use.  Both solar and wind are excellent for producing electricity - but technologies need to be developed for electrification of transport, manufacturing etc. 

C-14 is the radioactive isotope of carbon that has a half-life (half of the amount present decays) of 5730 years. Plants and animals buried under soil/mud or under water, 200 to 300 million years ago, got converted into fossil fuels.  Obviously, because of the long elapsed time, fossil fuels are totally depleted in C-14, and CO2 produced by burning them has no C-14 in it.  On mixing with the CO2 already present in the atmosphere, the amount of C-14 in a given volume of CO2 will be reduced.  Please click here for a detailed discussion of this topic.

The above three slides are adapted from a recent 2019 study published in nature.com. Please click here to access the full paper. 

The following slides briefly describe the new technologies that are being considered for removing CO2 from the atmosphere - CO2 that is already there.

More details may be found here, here and here.

Post Script: 

Climate change has never been taken seriously by most world governments, and suitable actions were not taken in time to control climate change and mitigate its worst effects.  Even now, when it is obvious that the effects of global warming are seen in frequent weather events, loss of ice sheets in Greenland, sea level rise etc., there is no indication that climate change is being taken seriously - one needs to consider the situation as climate crisis, and treated as such.  The example of the ongoing Covid-19 pandemic stands out when the world governments quickly found 10 to 15% GDP to fight the pandemic.  Twenty years ago, spending 1% of GDP would have been sufficient to control and mitigate the effects of climate change.

Similarly, good education about climate change would create much needed awareness among the general populations, and they will be more motivated to change their lifestyles and consumption habits.  No serious action by the people in power has been apparent and valuable time is being lost.  The longer we wait for sensible actions to start, the more extreme and costly measures will be needed.  There is no sign that things are going to change soon.

One might feel that technology will help to solve any difficulties that climate change might present in the future.  After all technology has always come to rescue in the past. I hope things turns out to be this way - although it would be far better if one could approach the looming threat of climate crisis in a rational way. There is too much at stake.

Biodiversity Loss in the Anthropocene; Impact on Human Welfare

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Humans are fundamentally, and to a significant extent irreversibly, changing the diversity of life on Earth, and most of these changes represent a loss of biodiversity    

Humans are but a small part of living organisms on Earth which supports a huge variety of organic life almost exclusively based on compounds of carbon. Over billions of years, natural selection (evolution) has fine-tuned the living ecosystem and maintains it in some sort of quasi-equilibrium. In ancient times, no living organism had the power and means to disturb the evolutionary processes.  Homo sapiens, since the agricultural revolution 10,000 years ago but more notably in the past 50 years, have increasingly been able to affect natural processes that support the large biodiversity on the planet. Such changes have been rapid and largely unplanned, driven by the demands of exponentially increasing human population and consumption.  We are now living in the new epoch; the Anthropocene.  

Much of the human activity has been detrimental to the health of the ecosystem - the loss in biodiversity is one of the many indicators of the damage being done to the Earth's ecosystem.  This has serious implications for the future well-being of the human race.  The present publication deals with the continuing loss of biodiversity that has been happening over the past few centuries.

There seems to be much misunderstanding about the relevance of biodiversity in our lives; an oft asked question is - why should we worry about loss of biodiversity?  I shall address this in the following but let me first explain what biodiversity is:

What is Biodiversity? - Biodiversity is the amazing variety of life at all levels, from microscopic to very large.  All organic life on Earth is based on carbon which is ~12% of the biomass.  To make sense of the variety of life, organisms are classified in different groups (taxonomy).  The following slides detail the global distribution of biomass with particular emphasis on human taxonomy: (Click on a slide to see full page image)

Humans (homo sapiens) belong to the animal kingdom. Animal kingdom (2 giga tons carbon) is a tiny part of the global biomass (550 giga tons carbon); and again humans (0.06 giga tons carbon) are a very small part  of the animal kingdom - in fact, humans are a mere 0.011% of the global biomass (see next slide).

Biodiversity Loss - Due to natural selection some species go extinct while new ones appear -  biodiversity is forever changing - but this is an extremely slow process. Human activity, particularly since the agricultural revolution (~ 10,000 years ago) has adversely impacted on global biodiversity.  While 1.9 million species have been catalogued to date, many are not, and it is estimated that there could be as many as 18 million species in total.  From fossil records, it is estimated that in prehistoric times, for every thousand species less than one went extinct every millennium.  Current extinction rate is already a thousand times greater than rates from fossil records, and is expected to increase in future. The situation is beginning to look like a major extinction event in play.

Serious biodiversity loss events (called major extinctions) have happened periodically with up to 90% of all living beings perishing.  Five major events have been identified by fossil records:

The Living Planet Report (2018) observes that over the past 40 years, there has been a 60% decline in the population of mammals, birds, fish, reptiles and amphibians. The top threats to species are identified as human activities including habitat loss, land degradation and over-exploitation of resources. 

The case of mammals is a good example in the way humans have modified biodiversity to suit their needs.  In prehistoric times, wild animals outnumbered humans by a factor of 100.  At present (see slide 3) wild animals are a small fraction of the humans numbers; surprisingly, livestock have become the main biomass of the mammal class. 

What Human Activities Cause Biodiversity Loss?  

The fundamental drivers causing biodiversity loss are human population increase (demographics) and quest for more affluent lifestyle (economics).  To feed the growing numbers, natural habitats are being converted to croplands (habitat loss), and forests are cleared for agriculture (deforestation).  50 million ha forests are cleared every year (100 ha = 1 km^2).  Since 80% of terrestrial species live in forests, deforestation is one of the biggest risks for biodiversity loss. 

Overfishing is capture of fish faster than they can replenish.  Fishing at the current levels is totally unsustainable and a big threat to the marine ecosystems.  Overfishing distorts the entire food chain in the oceans and has been responsible for catastrophic decline of many species like blue-fin tuna and Grand Banks cod. Of the world's major fisheries, 30% are overfished, while 60% are fully fished. 

Human activity has been responsible for serious rise in air (transport, industry, space heating etc.) and water pollution (fertilizer, pesticides, untreated sewage etc. contaminating ground water, rivers, lakes and oceans).  Outdoor air pollution kills 5 million people every year. Generally, lower life forms are more seriously affected than higher forms by polluted environment. 

Burning of fossil fuels (coal, oil & gas) sends massive amounts of greenhouse gases into the atmosphere which trap heat energy escaping from the earth. This has caused earth temperature to rise - climate change - with some dire consequences for biodiversity projected for the coming decades. The review is an in-depth study of climate change and biodiversity loss, and states: "The majority of models indicate alarming consequences for biodiversity, with the worst case scenarios leading to extinction rates that would qualify as the sixth mass extinction in the history of the earth"   

Why is biodiversity important? 

On the most fundamental level, each species should have a right to exist, whether or not it is useful to humans. 

On a more practical level, humans rely on the ecosystem for many valuable services without cost.  Biodiversity loss affects the resilience of ecosystems to provide the benefits worth over $33 trillion - a more recent (2018) estimate puts the value at $125 trillion.  These are huge sums - the global GDP in 2018 was $135 trillion! Even for economic reasons, it is in our interest to invest and maintain ecosystem services in the most efficient state of health - something that human societies have sadly failed to do.  

Let us look at some of the services that biodiversity is responsible for:

Provisioning Services: are biological resources like photosynthesis, food, timber, fuel, fibres for textiles, medicinal plants & pharmaceutical drugs, breeding stocks, genetic and species diversity and more.

Regulatory Services: keep different elements of the natural world running smoothly - soil formation and protection, sequester and store carbon (climate stability), recycle waste and dead organic matter, natural control of agricultural pests and disease vectors, breakdown of pollutants etc.

Cultural Services:  Aesthetic, spiritual & psychological benefits accrue from culturally important or recreational activities such as bird watching, fishing, hunting, gardening, tourism, growing ornamental plants etc. These services provide tangible health benefits.

Interdependency of Organisms: The entire earth may be viewed as a massive living system due to the interdependent nature of species - The Gaia theory. Ecological balance and biodiversity are crucial for all of earth, not just humans. 

Food Chains and Food Webs:  In order to function, all ecosystems on earth require a constant flow of energy - the energy flow can be traced through food chains and food webs.  The source of all energy is the Sun.  Sun's energy is metabolised by a primary producer (plants on land and phytoplankton in the oceans).  These are then eaten by other organisms through a hierarchical structure of consumers/predators. 

Some Examples: I give a few examples of how organisms depend on each other for their welfare and survival. Biodiversity loss disturbs the delicate balance within the ecosystem and harms species affected.  

Example 1: Bees

One third of our food (fruits and vegetables) would not exist without pollinators like bees, wasps etc. Honeybees, the primary species that fertilizes food-producing plants, have suffered dramatic declines in recent years.  2019 study has found that one in six species of bees have gone regionally extinct.  The study finds that 40% of insect species are threatened with extinction.  Habitat loss by conversion to intensive agriculture is the main driver of the declining populations, with agro-chemical pollutants, invasive species and climate change as addition causes. 

There is need to act urgently to ensure that the crucial link between plants, bees and human agriculture stays in good health - this will safeguard our food supply and protect the environment.  

Example 2:  Large Carnivores

Due to declining habitats the number of large animals - lions, leopards, wolves & bears - is declining.  Large carnivores are an integral part of the ecosystem biodiversity and play an important role in maintaining equilibrium among different species. 

For example, the loss of a large carnivore may mean that in the short term the population of herbivores,  they prey on, might increase.  But largely unchecked, the herbivores will graze more leading to a deterioration of the environment.

Example 3: Biodiversity and Human Health (The Inner Ecosystem)

Humans have a large number of microbes in their gut, skin and other organs.  The human gut alone has 100 trillion microbes - essential for processing food.  The microbiota and brain communicate with each other via the Vegas nerve, the enteric nervous system and also the immune system. Your gut microbiota regulates and impacts nearly every hormone in the body, including the thyroid hormones, estrogen, and melatonin.

During the past 50 years, there has been a sharp increase in non-communicable diseases like asthma, IBS, obesity, diabetes, and other chronic conditions.  Much of this increase is correlated to the changes in our lifestyles and excessive calories of poor sugar-rich, high fat diet.  There has been a serious migration towards cities with 70% of the world population expected to live in cities by 2050.  These factors can be damaging to maintaining a healthy biodiversity of the gut microbiota.  A recent article in The Conversation (also see) suggests that the friendly microbes found in the gut regulate the immune system and its response to inflammatory processes.  Unfortunately, modern living habits in big cities are harmful to such microbes.

Final Word:  Biodiversity loss has serious implications for the health of the global ecosystem and it ability to continue to provide valuable services that humans depend on.  Biodiversity is deeply relevant for our health not only on a global scale  but on an individual level as well.  Any loss in biodiversity must be avoided - the prevention is much better than the treatment that will be needed, and is much cheaper as well.  The first step is education - we need to appreciate what is happening and understand the issues.  Solutions are available - I have deliberately not discussed these here.  In my view, all solutions point to a change in the way we live with serious reduction in the use the earth's resources - it is a matter of sustainable development - to learn more about it you can look at my course on Sustainability.  

I do not think that at this point in time we are receptive to such changes - the world runs on the mantra of growth and increasing consumption - megatrends are difficult to change. 

Thanks for reading.

Appendix:  The following two slides explain taxonomy categories in more detail with the difficult Latin/Greek terms written in plain English.

What is Light? All You Need to Know - A Community Education Feature

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Light is fundamental to human existence.  It delivers the Sun's energy to us without which life on Earth will be impossible. We use light to explore and understand our environment  - vision is the only sense that comprehensively connects us to the outside world and is our main way of interacting with our surroundings.  We rely on light to guide our behaviour and perceive the external world.  The human brain uses 30-50% of its resources in processing vision related information 

For 2000 years or more, wise men struggled to explain what light is.  Historical attempts were interesting but generally wide off the mark - I refer you to 1, 2, 3, 4 for details. It is only in the past 400 years that good empirical evidence about light has been obtained. Detailed understanding of the nature of light has only been possible due to the pioneering work of many brilliant scientists like Newton, Maxwell, Einstein and others.

Dual Nature of Light - Funnily, sometimes light behaves like a beam of particles while at other times it behaves like a wave - this does not fit in the way we are used to making sense of objects in the world.  Objects are either particles or spread out waves - they are never both. The enigmatic behaviour of light had caused untold confusion among scientists who were at a loss to understand if light is a stream of minute particles or is a wave travelling through the space between the emitter and the receiver.  Within the framework of complex mathematical theories, we now can rationalise the dual nature of light - in fact, not only light but all matter (electrons, protons, neutrons, helium etc.) express this duality that has given us capabilities like electron microscopes etc. 

Light is Energy - Light is transmission of energy.  A source of light emits energy that travels to the receiver.  The light energy may be transmitted as a wave (all waves carry energy) or as a stream of particles (called photons).  Photons are little bundles of energy - the energy of a photon is determined by the frequency or wavelength of light (discussed in more detail later).  Light energy interacts with electrons in the atoms and molecules of the receiver.  Many possible things may happen in the interaction - for example, light may be absorbed or reflected or it may cause a chemical change etc.  We shall look at some of these later. 

     

Speed of Light - How fast light travels is a question that is now properly settled.  If you open your eyes then you can see distant stars instantly - only possible if light travelled at an infinite speed, a view that most people held in the past.  Clever experiments by Romer, Foucault and Fizeau determined that light travels with a finite speed - the modern agreed value of the speed of light (c) in vacuum is 299,792.458 km/sec.  It is quick - covering the distance from the Sun to the Earth (~150 million km) in a mere 8 minutes and 20 seconds.  Not only that - Einstein claims that this is the fastest that any object can possibly travel.  Speed of light in vacuum (empty space) is the maximum speed possible.  Prove Einstein wrong and you would cause a collapse of the modern science base! 

By the way, when you look at a star, you are receiving light from it that left the star in the distant past - the light you receive now could have been travelling for a million years or ten billion years, depending on the distance of the star from the earth.  

Colours - Light from the Sun appears white but pass it through a glass prism or a rain drop and one obtains a spectrum of colours (dispersion of light).  Most credit for explaining the nature of colours goes to Newton and Maxwell.

The speed of light (v) in a transparent medium like glass or water is less than its speed in vacuum (c) . The relative change in speed defines a useful property of the medium   -   the refractive index (n = c/v).  

When light travels from one medium to another, it encounters a change in refrative index - this causes a change in the direction of travel (bending of light or refraction).  The speed and hence the bending depends on the wavelength of light - resulting in a separation of colours (dispersion).   The slide explains how a spectrum is formed.

Dispersion of white light from the Sun by water drops in the atmosphere is responsible for the formation of one of the most beautiful phenomenon in nature - the rainbow.  You can read all you need to know about rainbows in my blog by clicking here.

Theories of Light - While Newton (1643-1727) did most to measure the properties of light experimentally - his book Optiks  published in 1704 provides details of his original and beautifully executed measurements, it was Maxwell (1831-1879) who explained the fundamental nature of light as electromagnetic waves (oscillating electric and magnetic fields; EM waves) through his four equations. Maxwell equations not only describe light waves that we perceive with our eyes, but also tell us that light is a tiny part of a whole spectrum of waves extending from nuclear gamma rays to radio waves.  The EM wave spectrum is explained in the following slides. 

(Click on a slide to see its full page image)

(You can skip the slides without loss of continuity)

Okay, so Maxwell accurately described all observations like reflection, refraction, difraction, interference, polarisation, dispersion etc. of light waves, but what about observations, such as the atomic spectral lines or the photoelectric effect, which just could not be understood if we consider light as waves (Maxwell's equations). Einstein (1879-1955) showed that to understand these, one has to consider that light is made up of a stream of particles (photons).  But photons, as particles, could not bend round corners (diffraction) - only waves can do that.  This seems all very confusing.  Is light a wave or a stream of particles?

We need the complex theories of Schrodinger and Heisenberg to make sense of the situation - suffice to say that such confusing behaviour appears to be a fundamental feature of nature applicable to all matter.

How is Light Generated? - There are two main categories of light. 

(a) Light that has a wide range of wavelength distribution - a good example is white light from the Sun or from a light bulb.  Bodies at about 5000oC are the most efficient in radiating energy in the visible region.  Such radiation is called the black body radiation and contains a large range of wavelengths - in the case of the solar radiation the wavelength spread (full width at half maximum - FWHM) is ~700 nm.

The second type of light has an extremely narrow FWHM (for atoms it is typically of the order of 0.01 nm) - it essentially appears as a line on the spectral graph - the width of the line generally represents the resolution of the spectrometer. Such light is emitted by excited  atoms and molecules - we can excite atoms in solids by heating the sample; in gases an electric discharge is very effective.  An example of the line spectrum of hydrogen is shown below:

If white light is passed through an element in gaseous form, then it absorbs the same wavelengths that it would emit in its emission spectrum - this results in a white light spectrum with narrow dark lines (absorption spectrum).

Elements and molecules have unique line spectra. Such line spectra are very useful in elemental analysis of samples - we use absorption spctra to determine what elements are present in stars and space in general (see slide above for the Sun), in forensic work etc.

A fascinating example of how bodies radiate and absorb light energy is discussed, with detailed examples, in my publication on the science of climate change.

Lasers - A laser is an unusual light source - it produces a beam of light which has an extremely narrow spread of wavelengths (can be much lower than 0.0000001 nm). 

Laser beams do not spread out much as they travel large distances - a laser used in measuring Earth-Moon distance (384,400 km) directs a laser beam to the Moon, and the spot at the Moon only grows to 10 km in size. The time it takes for the laser light to return back to Earth allows the Earth-Moon distance to be measured to millimeter precision!

It has been determined that the Moon is drifting away from the earth at a rate of 3.8 cm per year.

A laser beam may be focused to very small size and the energy density in the laser spot can be billion of times larger than the solar light intensity on Earth.  The ability to deliver such large power to small areas makes lasers very useful in industrial context.

In fact lasers play essential roles in many aspects of our lives.  Without going in detail, I shall list some applications of lasers; a detailed account of laser applications may be found by clicking here.  Some of the applications are also described in a very readable form here.

How Do Lasers Work? - I shall use a heuristic approach for this section. (See the slide below) 

Let us consider a water bucket with a big hole at the base - the hole has a plug to avoid leaks.  

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Water trickles into the bucket and fills it up - let us say in one hour.  When the bucket is full, the plug at the base is removed and the bucket-full of water gushes out in a couple of seconds.  What we have done is changed the trickle of water into a strong pulse of flowing water. 

Lasers work on a similar principle.  In order to keep it simple, I shall describe a 3-level laser system in a non-rigorous way.  Normally, all atoms in a material are in their lowest energy state - the ground state.  By supplying external energy (for example from an arc lamp), some of the atoms can be moved to excited states.  Atoms in the excited states shed their extra energy by emitting a photon after a short period of time - typically of the order of a few nanosecnds (a billionth of a second).  If we choose our material carefully, then the atoms might also have a long-lived excited state (a meta-stable state) with a lifetime of a few milliseconds or longer.

An atom in a short-lived excited state could decay to this meta-stable state.  After a few microseconds, there will be a lot of atoms in this state (see slide below).

When an atom in the meta-stable state decays, it will emit a photon with an energy equal to the excitation energy of the meta-stable state. According to Einstein, this photon (or the wave packet) will stimulate, almost instantaneously, the de-excitation of all the other atoms in the excited meta-stable state.  The result will be a pulse of light in which all the wave packets are in phase and are travelling in the same direction.  Essentially, the energy that the arc lamp had produced has been concentrated into an orderly, almost non-diverging, light pulse of a very short duration. This is a laser.

Thanks for reading.  Please pass the link to your friends and family. Comments are welcomed.