7.75 Billion and 415 ppm; 4C Warmer World is Really Bad News

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Summary: 
(Click on a slide to see full page image)

Atmospheric CO2 levels have reached 415 ppm 


World population is over 7.75 billion 

Mean global temperature is on trajectory for 4C rise over preindustrial levels by year 2100
(Some actually say that world will be +4C hotter much sooner)


Predictions are difficult as things might change but everything points to a miserable time for human civilisation.

Introduction:  One hears slogans like 'Save the World', 'We must protect the environment', 'Planet is burning'.  The fallacy in this thinking is to assume that it is the planet (mother Earth) that needs rescuing and we humans should do the right thing and help out.

What we must be saying is that human race is suffering, quality of life is on a declining path and we need to do something to rescue the human race from their self-inflicting foolishness.  The planet has been around for over 4500 million years and has hosted various forms of life - humans only arrived a few million years ago.  Nobody will notice if we disappear in a few hundred years - Earth will live on and, in a few thousand years, erase all traces of human existence. 

Humans have been waging a war on the natural world and there can be only one winner.  We need to take note.

It is not that we have not been warned - specially in the past 50 years, there have been scientifically sound advice about the need to take action. This has not been heeded and the negative effects of human activity on the earth are beginning to be felt in a serious way. 

Earth's resources have limits - there are planetary boundaries - stay within the boundaries and the planet will continue to provide the facilities for us to live here.  Current value of services nature provides us are estimated at 130 trillion dollars!  Humans need food, water and air to survive.  There are limits to how much food, freshwater, clean air our planet can give us.  We have crossed many of the planetary boundaries and, unfortunately,  there are few sign that humans are doing enough to improve matters in the future. 

In this blog, I shall discuss why the trajectory we are on is not a good one and threatens the survival of human civilisation as we know now. I do not believe that there is an existential threat - we are not facing extinction - what is on the cards is a lot of misery for a good fraction of human population.  In general, the wealthy OECD countries will manage to mitigate some of the effects of climate change, leaving the vast populations (and that is nearly 90% of the people) suffer miserably outside OECD.  Ironically, it is the extravagant lifestyle of unbridled consumption in the wealthy countries that has been responsible for most of the damage to the environment so far.  Even today, per capita, they are the biggest consumers of planetary resources. 

Why can't Something be Done about it?

There are two factors at play that have serious effect on global warming and climate change:  Fossil Fuels and Population.  Let us look at some numbers first:

1. Fossil Fuels: We need fuel to generate energy.  Fossil fules have been the driver of industrial growth for over 250 years (see slide).  They emit CO2 that is responsible, in addition to boosting ocean acidity, for increasing global mean land and sea temperatures. The concentration of CO2 in the atmosphere has been increasing since year 1800 with USA and EU being responsible for 50% cumulative emissions even though only about 11% of the population lives there.

Notice that Coal, oil and gas provide most of the energy.  Renewables like solar and wind are barely able to supply the increase in energy demand.

Recently, much economic progress has been taking place in developing countries like China and India.  These countries have large populations and people there aspire to reach living standards long enjoyed in USA and EU.  This is a megatrend and unstoppable, and will largely be achieved by burning more fossil fuels.  They also burn more of the highly polluting coal because it is cheaper and supplies are more reliable.  The result is increasing emissions - in fact it is already happening with China now emitting 25% of global emissions - as much as USA and EU together.  India too is catching up.  
The CO2 emissions from fossil fuel use are actually increasing faster than in the past.

On the current trajectory, emissions will continue to increase over the next few decades and the atmospheric CO2 levels will continue to go up as well. Most experts are talking about global mean temperature rising by >3C by 2100 - a far cry from the 1.5C 'target' of the 2015 Paris accord.

 Scientists and activists like Greta Thunberg and David Attenborough make good points but they are up against formidable reality - for the next two to three decades, there is no energy source available that can replace the energy generated by fossil fuels. CO2 levels and global warming will continue to increase as in the past decades because the world leaders just can't move too far away from the global growth model - particularly in the developing countries where the people's expectations are at an all time high.  It is interesting to note that fossil fuel industries receive an annual subsidy of $5000 billion.

Under current policies, temperature rise of nearly 4C by the year 2100 with all its consequences is projected. An interesting question is, whether we shall end up with a 5 or 6C rise! 

2. Human Population: Our numbers have been rising exponentially.  The slide shows some details:

There are several things about this slide that are worrying.  Even with an extremely low rate of 0.1% annual increase (it is currently about 1% per year), the population will grow to 11 billion by 2100 and to 25 billion by year 3000.  Mortality rates will be lower than today and the world will be overwhelmed by the number of 60+ years old people with hardly any young children around.  The function of societies socially, economically, housing and healthwise will be very different.
More relevant for our discussion is the provision of basic necessities - feeding 11 billion population is difficult to imagine with the type of diet and waste that we indulge in these days. Massive changes to what we eat and how food is produced will have to be brought in. Much research is underway and new ideas about making more efficiently produced plant food diet are being talked about.  Freshwater supply is a big worry too. 

For the increasing populations, we shall need houses and factories - increased cement production will add  massively to CO2 emissions.  Huge area of land are currently cleared to grow food for livestocks and agriculture.  Deforestation removes trees that then results in reduced absorption of CO2 from the atmosphere.  Habitats for wildlife are lost and there is already a serious loss of bio-diversity throughout the globe.  

Already, with 7.5 billion people, the earth's resources are extremely stretched.  We live on a planet that has finite resources in terms of land, food, water and fresh air.  These planetary boundaries are at breaking point - once broken the planet does not replenish itself efficiently and a vicious chain of decline sets in.  

Many scientists feel that we are at that point already.  Controlling population is a sensitive subject and nobody has a good answer as to how this aspect of the problem can be tackled. The current policy is not to talk about it!

In the wealthy countries, humans have treated the world resources inefficiently with total disregard for conservation.  Globally, a third of the food produced is wasted.  Obesity has been a problem of the rich countries but over the past 30 years, people in developing countries are also becoming obese and suffer with all the health related problems created by obesity. 

Pollution has been a big problem in the throw away society where vast amounts of packaging (lot of it plastic) is used unnecessarily. Recycling is being encouraged and many people are talking about circular economy with the aim to achieve zero waste. 
All efforts to control pollution, diet, waste etc. are not going to deliver the required climate mitigation as long as population keeps on increasing - even at 0.1% per annum - while each of us continues to consume more.
Many experts claim that population will plateau in response to better educated and more financially independent female population.  To some extent this seems reasonable but I think that culturally humans will wish to have more children (the extent to which chinese couples tried to bypass the countries one-child policy) and under the weight of increasing number of over 60 year olds, govermnments will start encouraging higher birth rates - this is already evident in many countries. In any case, a projected population of 11 billion by year 2100 stands in sharp contrast to the much reduced carrying capacity of the earth of a few billion under a +4C scenario. Interesting times ahead...  
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Have you read: 

Making sense of Our Climate Change - Parts 1 to 6

Over-population is 'Elephant in the Room'; Why Do We Not Address the Real Problem?

Future of Food; How to feed 10 billion People? 

Will Future Water Crises Destroy Our Civilization?

Arctic Ocean - Soaring Temp., Loss of Ice Cover - How Much and Why? What is the Future?

‘The only uncertainty is how long we’ll last’: a worst case scenario for the climate in 2050 - A feature article in The Guardian 15 February 2020

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A 4C warmer world is Bad News

Scientific advice has been to act to limit global warming to 2C or less at the end of the century. The residence time of CO2 in the atmosphere is several hundred years and climate change will continue for centuries beyond year 2100.  Also, the climate of the earth is determined by a number of feedback loops - disrupt enough of these and the climate may irreversibly drift towards one extreme (hot or cold) - sometimes rapidly.  The 2C warmer world is considered a limiting situation, beyond which changes can take their own momentum and could be difficult to control/reverse - so called 'tipping points' are reached. Predicting the climate then becomes difficult - almost certainly the reality will be much worse than linear models would suggest.  Also, we lock-in adverse climate change with all its consequences for a much longer period - not good for human civilisation.

Specifically, let me consider what a 4C warmer world would look like. The mean global temperature increase is exactly what it says - it is an average increase in temperature - different parts of the globe will warm by different amounts.  The poles will be warmer by 10 to 12 degrees, land area will also be warmer than 4C generally with the tropics affected most seriously.  They will become sufficiently hot and humid to make them uninhabitable.

Warmer oceans will result in more water vapour in the atmosphere and hence we shall see more intense rainfalls and higher humidity.  For ambient temerature of 37C or more, higher humidity causes heat stress and almost certainly tropics will be uninhabitable during the summer months.  

The slide shows what the world will be like at +4C.

+4C world will not be a pleasant place for 11 billion people to live.  Most regions in Africa, India, Southern China, most of USA and Brazil will be too hot or dry for agriculture and survival.  Fresh water will be a problem and populations will have to migrate north.  Canada and Siberia will be ideal places to live - infrastructure in the form of high rise, high density cities will need to be developed.

All people will have to eat plant based diet with new technologies like hydroponics widely used to safeguard fresh water and economise on land area. 

According to Professor Hans Joachim Schellnhuber, one of Europe’s most eminent climate scientists, director of the Potsdam Institute: “At 4C Earth’s … carrying capacity estimates are below 1 billion people.”

It is expected that sufficient energy can be produced by using vast solar farms in Africa, Southern Europe, India,  China and USA. 

Arctic will be ice-free most of the year and new navigational routes will connect Europe to Asia.  Phytoplankton form the base of the marine food chain.  Currently, they are plentiful in coastal areas where lots of nutrients are available.  Ocean upwelling also brings nutrients to surface and most phytoplankton are found in the northern latitudes.  They will shift further north and vast areas of the ocean will not be able to support marine life higher up in the food chain.  

Most mountain glaciers will have melted and rivers they feed will dry out.  However, intensive rains will cause frequent flooding - life will be a nightmare.

Extreme weather events will be more intense and frequent with devastating consequences.  Stronger hurricanes and frequent extensive wildfires will make life unbearable.  More than 70,000 additional deaths occurred in Europe during the extreme heatwave of 2003 - earth was only +1C hotter then!

Things might get much worse:  The scenario I have described assumes a linear progression in the response of earth systems to a warming world.  Once we hit +2C tipping points, we will expect to see unexpected events whose effects on the climate have not been included.  

For example, permfrost that holds twice as much carbon as the atmosphere will start to melt (it is already showing many sign of melting at levels that are 70 years ahead of schedule).  Melting permafrost will put large amounts of greenhouse gases (GHGs) into the atmosphere - accelerating global warming.

Oceans currently absorb about 50% of the CO2 we put in the atmosphere and there are some indications that the oceans are getting saturated with worrying implications of increased global warming.

Are There Any Hopeful Signs? 

Historically, humans have always risen to the challenges.  Even though world leaders are unable to take action because they are tied to the growth models requiring continued burning of fossil fuels and stoking global warming, there are strong signs that there is much unease at the grassroot level.  Throughout the world, activist groups are protesting and asking for action to control climate change.  Sustainable investment is being talked about that will divert funding from fossil fuel companies to more environment friendly sources of energy.  Many new ideas about new sources of energy, new ways of growing food, switching to plant based diet on a big scale, increasing energy efficiency of products etc. are all welcome signs and may help delay the +4C world by a few years.  However, rising population and absence of alternative energy sources makes the arrival of a +4C world near certainty - one can argue if it will be 2075 or 2100 or 2125?  Societal Inertia also does not help - sustained action taken in 1970 or 1980 might have solved lot of the climate change threats in a sane fashion. 

Final Word:  It will not be out of place to address the apparent paradox: In year 2100, the world is expected to be +4C warmer with a carrying capacity of one billion people; what will happen to the remaining 10 billion?
First of all, it will be a gradual process - as parts of the world become uninhabitable and coastal cities start flooding, there will be a mass migration towards more northern latitudes.  Siberia is already part of Russia, USA will annex Canada and Greenland by force and China will occupy Mongolia -  the superpowers will accommodate their populations okay but the rest of the world - particularly 1.8 billion people of India will have no where to go.  Many deaths will occur in the conflicts between indigenous populations of the north and migrants (who, if accepted, will be subjected to subhuman treatment).  
With a large number of existential issues, World War 3 (WW3) is quite likely.  Barring natural catastrophies like an asteroid strike or a super-volcano, other events could cause millions to die - for example,  a virulent strain of a virus or widespread famines due to failure of monsoon rains and diseases due to polluted water supplies.

Going around is a crazy notion (by some eminent people) that somehow, when the earth becomes too crowded and polluted, we can colonize other planets and heavenly bodies in space.  This is a hopelessly poor suggestion - I have discussed the matter of 'hype about space colonization' here. 

However, I think the biggest threat will come from artificial intelligence that can prosper irrespective of the state of the climate. The super-artificial intelligence (SAI) might see no need of human existence.  As I have said before - interesting times ahead...

Thanks for reading.

Climate Change; Indecision at COP25 in Madrid; Fiddling as the Planet Burns

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COP25 in Madrid has ended and COP26 will happen in Glasgow next year to continue the discussions.  Everybody has been disappointed that COP25 did not achieve anything of value - I am surprised that people were disappointed.  COPs are talking shops where they say good words and express concerns but by their very structure, they are not supposed to achieve anything much of value.  This has been going on since Kyoto 1997.  Paris 2015 was important as it seemed that at least it was realised that global warming should be limited to below 2C in 2100 but ideally attempts would be made to keep it no more than 1.5C. I did not believe anything will happen, and I said that again before COP25 and I do not believe much will change in COP26.  The world will continue to aggravate global warming, and 3 to 4C rise by 2100 is well on the cards.

The situation is really very simple and there are  several flaws in the whole process:  
To start with, number one reason that has been driving global warming is never seriously on the agenda - population growth. More than 2.5 billion people in China and India have joined the over-consumption binge of the developed OECD countries in a big way.  Even on the assumption that global population might stabilise by year 2100, consumption from other Asian and African countries will continue to drive the need for more energy - burning more fossil fuels and aggravating global warming further.  

A second problem in meeting any global warming target is what I call the 'Coal Trap'. The world faces a dilemma about how to produce the energy required to maintain a decent functionality and meeting peoples' aspirations for better standard of living.  There is no technological solution in sight that will rid us of consuming fossil fuels by 2050 and probably much longer.  There are many projections about renewable energy that is supposed to replace fossil fuels over the next few decades.  But, look seriously and you can quickly convince yourselves that this is not for real - renewable energy, in due course, might stop the increase in the amounts of fossil fuel we use but it is not practical for them to meet the global energy demand on their own - certainly not by 2050.

And we have left it too late.  That global warming is an issue has been known for 50 years or more.  Many predictions that science made have come true but governments and business interests have tried their best to confuse the issues.  They claimed that no action was needed and no serious action was, therefore, taken.  Perversely, the intensity of action needed increases as every day goes by and there are few scientists who believe that global warming may be limited to 3C by 2100 even if nations make their best efforts from now.

Climate change control clashes head-on with Sustainability:  Our planet is able to support consumption up to a certain level - we use planetary resources that need to be replenished.  This has not been happening.  In the OECD countries, we delude ourselves by saying that we have controlled energy consumption - it is not going up.  This is dishonest - what we have done is transferred manufacturing to China, India and other developing countries and import finished goods.  Emissions from the manufactured goods elsewhere are due to our consumption - they are our emissions and we are not counting them.  Include these and OECD will be shown not to be doing so well. Net zero by 2050 as UK and EU claim for their targets will be unachievable.

Who will pay and who will make sacrifices?  Rich countries caused the global warming by their extravagant, overconsumption lifestyle over the past 200 years.  Even today, USA consumes more than 2 times energy per capita than China and 8 times more than India, and EU is not far behind.  Standard of living in OECD will have to come down substantially to reduce emissions - will it happen? Definitely not.
The cost of climate mitigation is enormous - there is no extra money in the kitty.  Central banks and poor financial judgements at government level have ensured that most economies are just ticking over - there is no slack and I can't see much enthusiasm for funding climate control measures.

Poor will suffer most, and the rich have the means to do something: 
Look at the projections of the area of the world that will be most severely affected by Climate Change.  They are the poorest areas just now and have little or no political or economic power to do anything significant.  The other group to suffer more will be the poor people in the rich countries - again they will be sidelined by the government policies that will favour the rich (they generally do anyway). Serious migration from poorer countries will happen. The question I would like to ask is whether the poor of the world will be effectively enslaved by the few rich in each country - inequality has been rising and is expected to continue on that trajectory.  With new digital technology, a kind of cyber dystopia appears the most probable outcome over the next 80 years or so.  

Making Sense of our Climate Change: 6. Carbon Isotope Studies Prove That Human are Responsible for Global Warming

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Parts 1, 2, 3, 4 and 5 may be accessed here.

This post (Part 6) deals with a couple of complex concepts and may be more challenging.

Human activity is responsible for almost all the rise in atmospheric concentration of CO2 since 1990, and hence for the observed global warming.  How we can make such a firm statement is the subject of a great scientific detective story.  Essentially, from a sample of atmospheric air, we can tell what fraction of CO2 in it originated by burning fossil fuels and how much is due to plant and animal respiration.  Amazing!

The slide shows the history of global carbon emissions by burning of fossil fuels. Currently we are sending 10 gigatons of carbon per year into the atmosphere and this is causing an increase in the atmospheric CO2 levels.  Because we know how much fuel of each type is being burnt each year, it is possible to give a breakdown of contribution from different fossil fuel types.  Coal is the most polluting fuel and the recent sharp increase in its use does not bode well for future carbon emissions.

Actual measurements of atmospheric CO2 have been carried out at various laboratories since 1958.  Historic levels are derived from gases trapped in ice cores in Greenland and Antarctica.  These observations suggest that 46% of the CO2 put into the atmosphere by human activity stays in the atmosphere, increasing its concentration.  The rest is absorbed by the oceans and terrestrial biosphere.

The remaining CO2 will increase its atmospheric concentration by 2.1 ppm per year. (This can be  calculated easily and the method is shown in the slide at the end of this blog). 

In this part, I shall describe how we can actually identify the increase in atmospheric CO2 as due to the burning of fossil fuels.
    Much of the following discussion is based on the work published by NOAA.  I acknowledge Professor Jocelyn Turnbull's help for introducing me to NOAA publications on this subject.

Isotopes of Carbon:  Carbon isotope studies can tell us where the atmospheric carbon originated from and the results point unequivocally to fossil fuels as the main source of increased CO2.  
There are three isotopes of carbon that are found in nature - all isotopes of an element have the same chemical properties.  
C-12 has a mass equal to 12 atomic mass units (1 amu = 1.66 x 10-27 kg).  
C-13 has a mass equal to 13 amu, and
C-14 (also called radiocarbon) has a mass equal to 14 amu.

C-12 and C-13 are stable, but C-14 is radioactive and decays with a half-life of 5730 years (on decay, C-14 is converted into nitrogen; the amount of C-14 in a sample is reduced by half over 5730 years).

A sample of carbon nominally contains 98.93% C-12 and 1.07% C-13.  C-14 makes up about 1 to 1.5 atoms per trillion (1012) carbon atoms. C-14 is being continually produced from N-14 in the atmosphere by cosmic rays at a more or less steady rate that determines its background concentration.  The number of C-12 and C-13 atoms remains constant in time.   

Different carbon reservoirs 'like' different isotopes; each reservoir contains different proportions of carbon isotopes - has its own isotopic fingerprint.  By examining the isotopic mixture in the atmosphere, we can determine how much CO2 is coming from and going to each reservoir.  

There are three main carbon reservoir that actively exchange CO2 (see Part 5 about Carbon Cycle).  
The terrestrial reservoir consists mainly of plants, animals and soil.  Most CO2 is exchanged between the atmosphere and the plants.  CO2 diffuses through the stomata of the leaves and then photosynthesised by plants into carbohydrates.  Both diffusion and photosynthesis prefer to uptake the lighter mass C-12 atoms in preference to the heavier C-13.  Plant material is eaten by animals and also transferred to soil - therefore, carbon in the terrestrial pool is has less C-13 than in the atmosphere.  It also has less C-14 incorporated due to the larger mass of C-14.

The top few hundred meters of ocean surface is actively involved in exchanging CO2 with the atmosphere.  The lower depths store organic carbon and dissolved CO2 and mix their contents with the upper layers on a much longer timescales of centuries or more. The upper layer of the ocean exchange carbon di-oxide with the atmosphere.  Ocean water has no preference for absorbing or outgassing C-12 over C-13.  Oceans tend to have similar carbon isotope ratios as the atmosphere.

Fossil fuels are reservoirs which have held prehistoric carbon from millions of years ago.  Human activity has brought fossil carbon in play and CO2 generated by burning fossil fuel is sent to the atmosphere in a one-way transaction.  When plants and sea creatures got buried millions of years ago, they had some C-14 present.  Dead plants do not uptake any fresh carbon. Over the long period since then, C-14 has decayed to almost zero levels (halving in amount every 5730 years) and is present in undetectable amounts in CO2 produced by burning them. Fossil fuels are derived from plants and they also have lower C-13 levels relative to C-12. 

Determining Relative Carbon Isotope Values in a Sample:

One uses an isotope mass spectrometer (MS) or an accelerated mass spectrometer (AMS) for determing C-13/C-12 or C-14/C-12 concentration ratios.  Spectrometers are good at telling us relative values but not so accurate for absolute values; and one makes a simultaneous measurement with a standard where the ratios are known accurately.  Comparison with the standard provides absolute isotopic ratios for the sample - these are expressed as delta values - as explained in the slide below. 
(The slide may be skipped without loss of continuity)

An Example:  We can now show how the ∆ value of the atmosphere will change by injection of CO2 produced by burning fossil fuels.  Suppose the CO2 level is 400 ppm and in a year there is net injection of 2.5 ppm CO2 from fossil fuels.  This will change the ∆ value of the atmosphere to 38.5‰ from 45‰.  From this example, we expect that         ∆ (C-14) value will decrease by about 2.6% for every 1 ppm CO2 added to the atmosphere by burning fossil fuels. 

Actual Measurements:  CO2 takes about one year to fully mix in the atmosphere with other gases.  In order to study the change in C-14 levels in the atmosphere, it is best to find a region where there is no local hot-spot of burning fossil fuels.  In a well isolated region, away from populated areas we can monitor ∆ (C-14) values over a period of time and study any changes taking place - the changes will indicate the role of fossil fuels in the changing concentration of CO2.

The next slide shows the change in ∆ (C-14) values in an isolated region of the Rocky Mountains in Colorado: 

If we make such measurements near a local industrial area then CO2 produced would not have time to mix in the atmosphere and measured ∆ (C-14) values will be lower than those obtained for an isolated region.  This is shown in the next slide:

The above discussion shows that we can not only prove conclusively that majority of the added CO2 in the atmocphere is due to human activity of burning fossil fuels but we can also determine the exact amount of the added CO2 from fossil fuels.  

δ(C-13) Values:  We can also measure changes in δ(C-13) values that can be measured with very high precision with a mass spectrometer.  Fossil fuels have a δ(C-13) of -28 ‰ while the atmosphere δ(C-13) = -8 ‰.  Therefore, carbon di-oxide produced by burning fossil fuels will reduce the δ(C-13) value of atmospheric CO2.  However, the terrestrial biosphere also exchanges CO2 with the atmosphere and will also decrease the δ(C-13) value.  The analysis is more complex but we can separate the contribution of different sources by studying changes in δ(C-13).  This discussion is outside the scope of this blog and I refer you to NOAA publication for a more detailed discussion.

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Making Sense of our Climate Change: 5. Carbon Cycle and the Keeling Curve

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Parts 1, 2, 3, 4 and 6 may be accessed here.

Until the industrial revolution 200 years ago, the balance of carbon was largely determined by natural processes.  At a level of about 280 ppm, atmospheric carbon di-oxide was in equilibrium with the rest of the carbon in the ecosystem.  A strong volcanic eruption or higher number of forest fires might disturb the equilibrium for a short while but things were fairly stable. In the past 200 years, human activity has not only changed the land profile through deforestation and extensive farming, but humans have been burning fossil fuels that converts historic carbon ( coal, petroleum and natural gas buried underground millions of years ago) into CO2 and releases it into the atmosphere.  

The increased concentration of CO2 in the atmosphere results in other parts of the ecosystem absorbing more CO2 to reach a balance between atmospheric and land & oceanic carbon di-oxide.  However, only half of the CO2 sent to the atmosphere by human activity is removed by rebalancing the carbon cycle - the other half mixes with atmospheric gases and results in an overall increase of long term CO2 concentration in the atmosphere.  This value has gone up from 280 ppm in year 1800 to 410+ ppm in 2019.  The inevitable global warming effect has been observed to have warmed the land mass of the Earth on average by 1.1C; the sea surface temperature has risen by about 0.13C per decade over the past 100 years.  

The exchange of carbon among different components of the ecosystem is described by the Carbon Cycle. Oceans and soils hold the major fraction of carbon at the Earth's surface - in the form of dissolved CO2 in the oceans and organic carbon in the soil.  Carbon inventory of the oceans is sensitive to the surface water  temperature - CO2 is less soluble in warmer waters (solubility decreases by about 3% per degree centigrade rise in temperature) and may reduce the ability of oceans to remove CO2 in future.  Deforestation and land clearance increase loss of carbon from the land. The two slides show a highly simplified view of the carbon cycle. - (Click here for a more detailed description) 

The slide provides a good summary of carbon exchange in the ecosystem.  Most exchange happens through CO2 in the atmosphere.  

Notice that the largest store of carbon is in the form of carbonate sedimentary rocks made up primarily from buried dead coral and shells of sea-creatures.  They are mostly carbonates of calcium and magnesium.  During cement manufacturing, calcium carbonate is heated and CO2 is released to the atmosphere - this provides an additional important contribution.  

In slide 2, the numbers in red give the rate of carbon release in gigatons per year (GTC/y).  For comparison, volcanic activity, on average, puts 0.1 GTC/y CO2 into the atmosphere.  The major recent addition is the burning of fossil fuels by humans at 10 GTC/y. 

The box on the right (Click on the box to expand) explains the confusing use of carbon and CO2 
interchangeably. Because carbon is in many different forms  in various inventories, it is more convenient to talk of carbon amount than of CO2.

The Keeling Curve:  In 1958, Charles Keeling (1928 - 2005) started measuring CO2 concentration in the atmosphere at the Mauna Loa Observatory (Hawaii).  Keeling curve provides a record of the progressive build-up of atmospheric CO2. Keeling first alerted the world of human activity driven greenhouse effect and global warming.
The slide shows the Keeling curve as of 2019.  Notice the ability of the measurements to pick up the variation of CO2 levels during the year.  In Northern hemisphere, plants use CO2 during the growth period from April to October and respire CO2 during the winter months.  This shows up as an oscillatory signature superimposed on the annual trend of atmospheric CO2 concentration.  The slide is adapted from Data from Dr. Pieter Tans, NOAA/ESRL and Dr. Ralph Keeling, Scripps Institution of Oceanography.

An important observation from the Keeling Curve is the change in slope of the curve from around 1995. The rise in CO2 concentration is more steep and it is going up at a faster rate now than previously.  This is worrying as this represents that global warming may have quickened.  The increasing slope simply reflects the situation on the ground where human activity is burning greater amounts of fossil fuels and enhancing atmospheric CO2 levels.

In Part 6, I shall explain how we can determine the contribution of human activity to the increasing amount of CO2 in the atmosphere.  In fact, as we shall see, almost all the increase in CO2 levels may be credited to human activity with natural variations playing an insignificant role.

Making Sense of our Climate Change: 4. Global Warming Indicators

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Parts 1, 2 and 3 may be accessed here.

Scientific evidence for warming of the climate system is unequivocal.                      

                                                                   - Intergovernmental Panel on Climate Change (IPCC)

In Part 3, I had discussed how greenhouse gases (GHGs) trap and send back some of the heat energy radiated from the earth.  The result is a warming of the earth's temperature.  In this part we shall look at some of our planet's vital signs that are affected and may even be used to quantify the warming.  

Concentration of GHGs in the earth's atmosphere has been increasing for the past 200 years resulting in a corresponding rise of earth's temperature. This is widely attributed to the much enhanced human activity since the first industrial revolution - for example, the phenomenal rise in the use of fossil fuels to power the manufacturing industries, internal combustion based road and air transport and mechanisation in agricultural (I shall discuss how we empirically identify human involvement/contribution in global warming in Part 6). 

Earth's temperature can also change due to natural causes such as variations in earth's orbit around the Sun affecting the amount of solar energy reaching the earth.  These variations, called the Melankovich Cycles have long time periods and have regularly affected earth's climate in the past.  Another natural cause might be changes in Solar energy output or changes in cosmic rays intensity.  Scientific studies have ruled out the possibility (as some claim) that changes in earth's climate since the year 1800 are wholly due to such natural variations; and have strongly (and convincingly) implicated human activity to be the major driving force behind recent global warming. 
Following three slides show the data:

The figure clearly establishes that temperature and atmospheric CO2 levels are highly correlated.  Also note that over the past 800,000 years, CO2 levels have been below 290 parts per million.  However, in the past 200 years CO2 concentration has shot up to 410+ ppm as the next two slides demonstrate.

The concentration of other greenhouse gases has also increased - the figure below shows an exponential increase (red panel) since the industrial revolution when both the human population and industrial activity burning fossil fuels really took off.

A credible model of what has been happening is described below:

The use of fossil fuels (coal, oil and natural gas) mainly releases carbon dioxide (CO2) into the atmosphere where it resides for a period of 200 years or more.  Some 50% CO2 is absorbed by the oceans and land plants, while the rest half mixes with the gases in the atmosphere.  Increased atmospheric CO2 concentrations return a larger fraction of earth's IR radiation back to the earth to be absorbed mostly by the oceans - oceans become a sink for this extra heat energy - and cause warming of its surface temperature.  The extra thermal energy is distributed throughout the globe by air circulation currents - increasing the land and atmospheric temperatures also.  The result is a general increase in global heat content and its temperature.

Besides burning fossil fuels, many human activities like deforestation, excessive use of nitrogen based fertilisers etc. are causing loss of forests, soil erosion, environmental pollution, habitat & bio-diversity loss and much more.  In tandem with climate change, the result of these human activities have serious deleterious effects on life on earth.

How Global Warming Affects Things on the Ground?

What are the Indicators?

I mention some of the indicators below

Global Warming leads to the melting of ice in the cryosphere - mountain glaciers melt faster, ice cover in the Arctic and Antarctica is reduced.  Mountain glaciers supply freshwater to almost 2 billion people - their disappearance will be catastrophic for the supply of drinking water and for irrigation to the communities affected.

The sea water volume expands due to increased temperatures. Also additional water is added to the oceans by melting ice sheets and glaciers.  Greenland ice is melting seven times faster than it was 25 years ago and is equivalent to a sea-level rise of 7 mm/decade.  The sea-level increase threatens to inundate coastal cities where large populations live.

The sea at a higher temperature holds more energy and engenders more powerful hurricanes.  
Wind patters are affected causing variations in rainfall and drought patterns throughout the globe.
  
Higher land temperatures evaporate more water from the land and trees in forests, making the wood drier.  This enhances the frequency and severity of wild fires. 

Absorbed CO2 in the oceans makes them more acidic leading to a decline in coral health and other sea-life.

Animal habitats are affected.  Many animal species move to the colder temperatures at higher latitudes because their traditional habitats have become too hot.  

Insects can now survive in many northern regions that were too cold for them in the past. Many of the  tropical diseases borne by these insects are beginning to spread to new regions - people in these regions have little or no immunity to such diseases.

Species living in year-round icy conditions have no where to migrate to and will eventually become extinct. 

It is concerning to note that all of these expectations (I have not listed all of them here) have transpired and the data available points to global warming as the underlying cause.  Ironically, over the past few decades, most data indicates globe warming is increasing at a faster rate - the situation is getting worse - and many scientists are very worried about the future catastrophes that out of control global warming might deliver to the human civilisation and even cause much irreversible damage. Concerned scientists and international bodies have been putting out warnings about the urgent need to control and reverse climate change. 

I end this part with some graphs showing the most  important trend.  Human population is the driving force behind increased consumption and is the most important parameter whose trend is strongly upwards.  The global population has to come down for the global warming and climate change to be reversed.  There are few sign of this happening as the next two slides show:

By UN projections, the annual growth rate will decrease from the peak of 2.1% in 1950 to 0.1% in 2100.  This is still an increase.  The exponential growth, even for this minuscule looking number, will double the population to 22 billion in year 2800 and to 44 billion in year 3500.  The population pyramid shown in the second slide is unnerving when one realises the age structure in year 2100 compared to 2018.  While there will be some increase of population in 0 to 35 age group, most numbers will be added to the older ageing population above 60 years. There will be about 800 million people of age 80+ years. How this will be managed is anybody's guess - certainly world leaders do not ever talk about these matters - it is a problem of the future - that is the tragedy of sustainable development.   

Along with human population, the number of the ruminant livestock (raised for their meat) has been increasing by almost 1% per year over the past 50 years; per capita meat consumption also increasing by this amount.  These animals require a lot of water, land, food and energy resources, and these have been increasing accordingly.  For example, Amazon rain-forest is being lost at 2.4% per year (to grow animal-feed and corn for bio-fuels) and the global tree cover loss (to create new farming land) has been a staggering 5% per year since the year 2000.  Forests are one of the most efficient sinks of CO2 - their loss translates into less CO2 absorbed from the atmosphere and hence more global warming.  Accelerated global warming is exactly what we have been observing over the past decades.  

The world business model is that of perpetual growth.  In absence of growth, the global monetary system will come crashing down and growth must be maintained at all costs.  Growth means higher energy consumption that in turn means higher GHG emissions leading to increased global warming.  It is a vicious cycle and some miraculous leap of technology is required to break it.  None is on the horizon and there is not much time left to act decisively.

In Part 5, I shall discuss the Carbon Cycle, and in Part 6 we shall look at the evidence that most of the recent global warming is caused by human activity.  The evidence is based on radiocarbon studies and we shall look at the science of radiocarbon and stable isotope analysis of climate indicators.