What is Climate Change? - Matthew Short

“[The unchecked burning of fossil fuels] would have a sort of greenhouse effect”, and “The net result is the greenhouse becomes a sort of hot-house.” Alexander Graham Bell, 1917

Bell went on to also advocate the use of alternate energy sources, such as solar energy.

Climate change is really the trigger that got me personally working towards sustainability, examining everything we do as a business. When the Intergovernmental Panel on Climate Change (IPCC) interim report landed in 2018 (3) and received wide scale publicity it was a real shock. Though I had heard of global warming and Climate Change, I wasn’t aware of just how severe and far reaching the effects were likely to be, and what little time we had to act.

The IPCC report said..

Limiting global warming to 1.5ºC would require rapid, far-reaching and unprecedented changes in all aspects of society assessment

It’s perhaps the far reaching nature of the changes needed to reach the 1.5 degrees goal that have produced such strong criticism from people such as US President Trump, or indeed in the comments section of newspapers such as The Times when they publish Climate Change stories. The media are partly to blame for this as they tend to latch on to certain stories or publish individual research papers out of context leading to confusion in the general public. It may also be a shock response or disbelief that what seemed to be 170 years of progress since the industrial revolution has taken us to the brink of ecological breakdown and the sixth mass extinction event.

But given that 97% of scientists around the world have no doubt that man-made Climate change is happening (and the other three percent’s evidence has been proven flawed when other scientists have tried to recreate their experiments), and the IPCC reports are the best peer reviewed evidence we have, business as usual isn’t an option.
The 1.5 degrees temperature rise mentioned in the IPCC report is important as the Paris accord set a limit of 2 degrees C. Now whilst that might not seem a lot of difference, in terms of impacts on our planet it is huge.
I’ve spent many months studying the science of Climate Change and have found the Future Learn courses run by the University of Exeter to be excellent (1). Not least because they give some hope that whilst it will be huge task, it’s not insurmountable if we work together and fast.

First let’s recap on what the UN Goal says….

“Climate change is now affecting every country on every continent. It is disrupting national economies and affecting lives, costing people, communities and countries dearly today and even more tomorrow. Weather patterns are changing, sea levels are rising, weather events are becoming more extreme and greenhouse gas emissions are now at their highest levels in history. Without action, the world’s average surface temperature is likely to surpass 3 degrees centigrade this century. The poorest and most vulnerable people are being affected the most.

Affordable, scalable solutions are now available to enable countries to leapfrog to cleaner, more resilient economies. The pace of change is quickening as more people are turning to renewable energy and a range of other measures that will reduce emissions and increase adaptation efforts. Climate change, however, is a global challenge that does not respect national borders. It is an issue that requires solutions that need to be coordinated at the international level to help developing countries move toward a low-carbon economy.

To strengthen the global response to the threat of climate change, countries adopted the Paris Agreement at the COP21 in Paris, which went into force in November of 2016. In the agreement, all countries agreed to work to limit global temperature rise to well below 2 degrees centigrade. As of April 2018, 175 parties had ratified the Paris Agreement and 10 developing countries had submitted their first iteration of their national adaptation plans for responding to climate change.”

Ok, so now we’ve got that let’s review the underlying science behind Climate Change such that as Businesses and human beings we can modify our actions to help. (Thank you to the University of Exeter for much of this information).

The Science of Climate Change

Climate Variation in the last two million years
The following information is derived from a short course by Professor Dan Charman – University of Exeter.
We’re all perhaps familiar with the concepts of Ice Ages and some of the dramatic climate variations that have occurred in the last two million years. The main changes over thousands of years such as Ice ages are predictable and are caused by variations in the shape of the Earth’s orbit and the angle and location of its axis.
Serbian scientist Milutin Milankovitch proposed that the changes in the intensity of solar radiation received by the Earth were affected by three fundamental factors. The first of these is called eccentricity, a period of about 100,000 years, in which the nearly circular orbit of the Earth, changes into a more elliptical orbit. When the orbit is circular, the distribution of energy is equal throughout the year. When it is fully elliptical, the Earth is slightly close to the sun sometimes, so it receives more energy at that time of the year.
The second factor is called obliquity, a period of about 41,000 years, when the Earth’s axis tilt varies between 21.5 and 24.5 degrees. This also changes the distribution of solar radiation on the planet.
The final factor is called precession, a period of approximately 23,000 years, where the Earth’s axis wobbles like a spinning top. As it wobbles, the timing of the seasons changes. For example, 11,000 years ago, the Northern Hemisphere was tilted toward the sun at the same time as the Earth is at its closest point to the sun.

This meant that there was a greater difference between summer and winter causing much more seasonal climates.
If the changes in the Earth’s orbit are totally predictable, why can’t we predict natural variability precisely? Well that’s due to the interaction of feedback mechanisms in the climate system we’ll explore next.

The Greenhouse Effect

You’ve probably heard of the greenhouse effect. However the greenhouse metaphor isn’t actually a very accurate one. When thinking of Climate Change a blanket is a much better metaphor. The presence of certain gases in the atmosphere absorb heat radiation and re-emit it back down to the surface. These gasses are known as greenhouse gases, but really these gases act more like a blanket wrapped around the planet.
A blanket traps heat and re-radiates it back to whoever is wrapped up in it.
Visible short wave radiation from the sun comes through the Earth’s atmosphere. Some is reflected by clouds, some scattered by particles in the atmosphere, and some absorbed by ozone and other gases. But the remainder reaches the Earth’s surface.
When it hits the Earth’s surface it can either be absorbed or reflected back through the atmosphere towards space. The fraction that is reflected depends on the nature of the Earth’s surface. A white surface such as an ice cap is very reflective. Dark oceans absorb a lot of radiation. This reflection is called the albedo. A very reflective surface such as snow has a high albedo, a surface that is dark and absorbs has a low albedo.

As you may have seen on nature programmes exploring the polar regions reducing sea ice cover exposing the dark ocean underneath causes the Earth to absorb a lot more heat radiation.

Overall, the Earth reflects about 30% of the sunlight that reaches it from space. In other words, it has an albedo of around 0.3. If it was just down to the absorption of the sunlight and heat that reaches the Earth, we would be very cold indeed, as our planet would have an average temperature of 18 degrees centigrade below zero!

But due to the blanket of gases in the Earth’s atmosphere the surface is warmed by 33 degrees to an average temperature of 15 degrees centigrade.
So we do need a certain amount of greenhouse gasses in the atmosphere.

So, the Earth emits radiation as heat. Some of that heat radiation is at the right wavelength to be absorbed by gases in the atmosphere. These gases, in turn, emit heat radiation, and some of it comes back to the Earth’s surface.

So what are these greenhouse gases?
Carbon dioxide is the gas that most of us think of as the most important gas in this blanket. But perhaps surprisingly it’s actually water vapour that plays the biggest role in keeping our planet warm. Other important gases are methane, ozone, and nitrous oxide.

Carbon Dioxide
Although carbon dioxide plays such an important role in climate change, it makes up only around 400 parts per million (ppm) in the atmosphere. This is frequently quoted by those that deny man made Climate Change is occuring. How can such a small percentage in the atmosphere cause such a problem?
It is released naturally through volcanoes and organisms breathing, but human (anthropogenic) activities with fossil fuel burning and deforestation are increasing CO2 levels at an unprecedented rate. It has increased in from 280 parts per million in the early 1800s and as it is very long-lived in the atmosphere, it makes it the most important greenhouse gas produced by human activities.

Water Vapour

Water vapour is a natural greenhouse gas, an important regulator of the climate system and the most abundant natural greenhouse gas. As the Earth’s atmosphere warms, water vapour evaporates from the oceans and enters the atmosphere and we have a so called positive feedback loop. Human activity doesn’t directly add water vapour to the atmosphere. As the concentration of greenhouse gases increases and so the temperature, the feedback indirectly adds water vapour to the atmosphere.

Methane
Methane is much scarcer than CO2, making up only 1.8 parts per million of the atmosphere. It is important however as each methane molecule contributes around 25 times more to warming than a CO2 molecule. The amount of methane in the atmosphere has increased nearly three times due to human activities. Methane is created by microorganisms, where the breakdown of organic material occurs in environments absent of oxygen – such as in rice fields or the guts of cattle. It’s also generated in landfill sites.

Nitrous Oxide
Nitrous oxide is around 300 times more potent per molecule than carbon dioxide. It makes up just (0.3ppm) part of the atmosphere. It is made by microorganisms that are fueled by the addition of nitrogen fertilisers to agricultural land. Though it makes up a small fraction of man-made greenhouse gases, human activities and its long life have increased the concentration by 15% so it is important to get under control.

Ozone
High in the atmosphere ozone protects human life by blocking ultra vioet radiation from the sun. At the surface each ozone molecule has approximately 1000 times the warming of carbon dioxide, but there is much less of it and it is very short lived. Vehicle emissions react in sunlight to form this ground-level ozone.

Tetraflouromethane (CF4)
A lesser known Greenhouse Gas is CF4.
CF4 is emitted into the atmosphere by three main industries:
– the aluminium industry;
– rare earth smelting;
– the semiconductor industry.
Tetrafluoromethane (CF4) is harming our atmosphere and increasing global warming 7,360 times more than CO2!
There are essentially two different ways that CF4 is emitted. In the case of the aluminium industry and the rare industry it is emitted during the electrolytic process, but in the case of the semiconductor industry it is bought and used for different purposes including etching and/or chamber cleaning.

Initially CF4 was thought to be less damaging than other gases. However, there wasn’t enough focus on it’s long life. CF4 has a half-life of 50,000 years, so even 50,000 years from now, the best we can hope for is that only half of it will be in the air. We currently know of nothing at all that can remove it out of the atmosphere once it is there.

What is Climate?
The following information comes from the UK Met Office.
Firstly let’s clarify the often asked question – What is the difference between weather and climate?
“Weather is the elements we see daily such as temperature, rain and wind. These can change by hour and day by day. Climate on the other hand looks at how the weather changes over long periods of time. Typically around 30 years. Scientists have been able to define climate zones around the world.

Here in the UK we have a temperate climate that is neither especially hot nor cold wet nor dry when compared to other climates. Ours is a very different climate to that in the Sahara for example which is known as arid because throughout the year the weather is dry and hot. Scientists have to look at how the atmosphere interacts with the oceans, ice sheets, land masses and vegetation. These different interactions create a climate system and these interactions as well as the composition of the atmosphere itself create a very complex system.”
So What are the Climate Systems?
Professor Tim Lenton of the University of Exeter gives an excellent explanation on this….
The Climate is conceptualised as a system that encompasses five key components
– The Atmosphere
– The Hydrosphere– primarily the oceans, but also fresh water, rivers, lakes, and groundwater
– The Biosphere – all the living things in soils
– The Cryosphere – ice sheets, sea ice, and mountain glaciers
– The Lithosphere – the surface of the Earth’s crust.

If we look closer there are a series of cycles that form the links and interactions between the components that form the climate system.
The water cycle.
Solar radiation causes water to evaporate from the surfaces of lakes, rivers, and the oceans. From the biosphere water evaporates and transpires from green plants. Water vapour condenses in the atmosphere to form clouds, and returns to the surface through precipitation, rain and snow fall. On reaching the surface, water returns to the hydrosphere. If it is frozen as snow, it can enter the cryosphere.

Sunlight on the cryosphere can melt snow and ice or transform it directly into vapour. The key take away is that the water cycle is influenced by a wide variety of factors that can be changed by human activity.

Feedback effects
There are a number of feedbacks that operate in the dynamics of the climate system. Cycles that connect components of the climate system create feedback loops, that is closed loops of cause and effect. As a former engineer I’m very familiar with feedback loops in electrical control systems, be it a simple thermostat to control temperature, or a more complex system to control the power transmission of a mobile phone mast.
The climate system has multiple feedbacks acting to regulate the climate towards a particular state.
There are three key Climate feedback mechanisms
– Water vapour feedback
– Ice albedo feedback
– Radiation feedback.

Water Vapour Feedback
Evaporation occurs when solar radiation heat the surface of water. Evaporating water is transformed from the liquid to the gas phase and stored in the atmosphere. The molecules of water vapour in the atmosphere absorb heat radiation coming from the earth below, causing them to vibrate. Then they re-emit heat radiation, some of which comes back down to the surface, resulting in further warming. This increased warming in turn increases the amount of evaporation in an amplifying process, which we call a positive feedback. Positive feedbacks in electrical systems can often cause systems to rapidly go out of control – think of Jimi Hendrix moving his guitar closer to the amplifier stack creating a howling distortion.
Positive here is refering to the mathematical sense, not in terms of a good outcome!

Ice albedo feedback.
An area of ocean that is covered by sea ice such as the Arctic will reflect back much of the solar radiation due to the highly reflective ice, which we say has a high albedo. The Dark ocean surface, on the other hand tends to absorb more than it reflects, because it has a low albedo. So as the ice melts we have a gradually less reflective surface and so we absorb more heat reinforcing the melting. Again a positive feedback loop.

Radiation Feedback
The final feedback loop is the most important for the functioning of the climate system. It a negative feedback loop. But we don’t mean negative in a bad way. All objects give off radiation, but the warmer a body is, the more radiation it gives off. And when a warm body gives off more heat radiation, that cools it down. An example might be in a Pizza oven when logs get so hot that the radiation is visible to us.
This phenomenon is known as the Stefan-Boltzmann effect or the Planck feedback after the physicists who first described it.

So climate can be thought of as a system. Through a combination of positive and negative feedbacks linking together it self regulates.

The Intergovernmental Panel on Climate Change (IPCC)
The IPCC are a scientific body that reviews and assesses scientific, technical and socio-economic information on climate change.
The work of the IPCC is contributed to by thousands of scientists from all over the world, including scientists from the University of Exeter who I owe much of this information to.

Headlines from the 2013 Climate Assessment Report

Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen, and the concentrations of greenhouse gases have increased.
Human influence on the climate system is clear. This is evident from the increasing greenhouse gas concentrations in the atmosphere, positive radiative forcing, observed warming, and understanding of the climate system.
Continued emissions of greenhouse gases will cause further warming and changes in all components of the climate system. Limiting climate change will require substantial and sustained reductions of greenhouse gas emissions.

Past Climate Change
One of the comments you might hear related to Climate change is ‘but the climate has always changed’. This of course is true. Again drawing on work from the University of Exeter it’s worth looking at how our Climate has varied in the past.
The Earth’s climate has self-regulated for 4.5 billion years, and the Earth has been a habitable place for life for almost all of that time. Explaining climate change over 4.5 billion years of earth history is a complex puzzle.
The solar system was born 4.5 billion years ago. At that time, our sun was 25% to 30% less bright than it is today. But If we took today’s blanket of gases surrounding our planet and turn the sun down by 25% to 30%, the Earth would be around 20 degrees centigrade colder – it would be frozen, and yet – it wasn’t? Evidence shows the Earth was covered in liquid water since around 4.2 billion years ago, and there’s been life on the planet, which needs liquid water, since as far back as 3.8 billion years ago.

Even more confusing evidence shows that the early Earth was actually warmer than it is today. We have evidence to suggest that there was a thick blanket of warming gases in the atmosphere particularly carbon dioxide and water vapour at a time when the sun was fainter than today. So, despite the sun being weaker, this thick air blanket of warming gases kept the Earth warm.
But if there was that much CO2 in the atmosphere – where did it go? The answer is underneath us in sedimentary rocks. As the continents developed, they weathered. Carbon dioxide and rain water forms a weak acid, carbonic acid, that dissolves silica rocks. The carbon in the form of bicarbonate ions washes into the ocean where it is used by many organisms to form their shells, which are then deposited on the ocean bed to form carbonate rocks (I looked at this when talking about ocean acidification). So our climate has self-regulated. Even though the sun is getting brighter, we haven’t seen a proportional increase in the Earth’s temperature due to negative feedback. As the Earth’s temperature began to increase, then so did the rate of chemical weathering.

400 Parts Per Million (PPM) Carbon Dioxide
Carbon Dioxide levels are now at 400ppm and warming is occuring at an unprecedented rate. In order to understand what could happen scientists have researched an event 50 million years ago known as the Paloecene-Eocene Thermal Maximum (PETM). In the past CO2 levels have been much higher than they are now, but the changes take millions of years to occur. On these timescales species can evolve.
During the PETM however temperatures rose by around 5 degrees C over 20,000 years – very rapid by geological standards. The oceans acidified and warmed by about 6 degrees C. This led to species extinction, movement of ecosystems, destruction of coral reefs and vegetation on Antartica and around the arctic. The PETM was caused by a rapid release of greenhouse gases possibly due to large volcanic events releasing CO2 over a short period of time. This triggered a series of positive feedback mechanisms that may have included the release of methane trapped in frozen sediments. It took around 100,000 years for global temperatures to recover as the silicate weathering mechanism is so slow.
During the PETM warming occurred at a rate of 0.025 degrees C per 100 years. But we’re on track for warming of 1 degrees C per 100 years! We haven’t yet tipped the methane hydrate reservoir into an ireversible positive feedback effect – but it could happen.

The rate of warming is such that species may not be able to adapt and we could be looking at the next mass Extinction event.
If you’d like to know more about the science behind Climate Change I highly recommend the University of Exeter’s Science of Climate Change course that explains how scientists use a variety of methods to analyse the recent and past climates, and model the future climate. You can even download and run your own climate model.

Effects of Climate Change

Until relatively recently the vast majority of us naively thought that ‘Global warming’ would simply lead to a gradual linear temperature rise and a slightly warmer climate. We are now all realising that this isn’t the case and that the changes are far reaching and often unpredictable. We could be close the next mass extinction, and indeed much of our biodiversity has declined so much that we could already be part the way through!
We have very close links with Madagascar and work with a charity Small Steps for Africa (SSFA). We asked Charlotte Baker of SSFA what some of the present challenges facing Madagascar are…

…there needs to be some serious thoughts around how Madagascar (and the Global South in general) will adapt to the negative impact of climate change. Already there has been severe drought in the south of the country for several years’ running, decreased yields from vanilla crops (as I’m sure you know) and increased violence as people attempt to protect what livelihood they do from thieves, often by carrying guns and knives. I’m sure there are some innovative technological solutions that could help look at how to grow vanilla more effectively with less reliable rainfall etc, and helping farmers diversify. Bits of it are happening in Mada, but it’s not really happening fast enough

Now whilst we should be careful not to attribute every extreme weather event to Climate Change there is a perception that extreme weather events are becoming more frequent.
Professor Matt Collins of Exeter University says…

For those of us living outside the Arctic, there has been a perception that the frequency of extreme weather events is on the increase– floods, hailstorms, heat waves, tornadoes, hurricanes to name but a few. But it’s difficult to say if these are part of a long-term climate change signal or are just natural fluctuations. Equally, as global population rises, we may become more vulnerable to natural variations in climate. Our ability to observe the environment of the Earth in terms of temperature change and sea level rise has given us some key indicators of climate change.

Certainties
There are some certain changes that we are already seeing from Climate Change.
Temperature
From 1880 to 2012, the Earth’s surface warmed by an average of 0.85°C. Every year since 2012 has been in the top 10 warmest years on instrumental record, the Earth is now around 1°C warmer than in pre-industrial times.
It is extremely likely that more than half of the observed increase in global average surface temperature from 1951 to 2010 was caused by the anthropogenic increase in greenhouse gas concentrations and other anthropogenic forcings together.

From the IPCC temperature it can be seen that temperature has risen by 1˚C over this time period, with most of the warming occurring after 1910.
Global temperatures do experience short-term variations on top of the long-term trend – leading to intervals of slower or faster warming. These can be attributed to normal, short-term variability in global climate from events such as El nino.

Precipitation
A warmer atmosphere holds more moisture and it appears that globally averaged precipitation may have increased over the last century. Extreme rainfall events have increased over many land areas. However the increase isn’t equally spread around the world and regions such as the Mediterranean, have been getting drier. Global average precipitation is projected to increase, with wet regions getting wetter and some dry regions becoming drier.
The IPCC 2013 summary says
Changes in the global water cycle in response to the warming over the 21st century will not be uniform. The contrast in precipitation between wet and dry regions and between wet and dry seasons will increase, although there may be regional exceptions.

Sea Ice

Arctic sea-ice extent has declined by 0.45-0.51 million km2 per decade, and the corresponding ice albedo feedback is a major reason why the Arctic is warming roughly twice as fast as the global average. In contrast, Antarctic sea-ice extent was increasing at 0.13-0.20 million km2 per decade, linked to changing wind patterns over the Southern Ocean. However, global sea-ice extent in 2016 was the lowest on record, with the November extent being 2 million km2 less than the November 2015 extent. – University of Exeter

Tipping Points
As we have evolved as humans (i’m assuming we’re all human reading this!) over the last 10,000 years we’ve tended to experience the world as a series of linear increments. This can lead us into the false sense of security that Climate change is a gradually incrementing change that we can offset by gradually decreasing our carbon dependency.
However the Climate is a complex system and is unlikely to act in this way.
Professor Tim Lenton – University of Exeter and the Potsdam Institute for Climate Impact Research (PIK) have been key in identifying potential Climate tipping points in the biosphere (2).
Here i’ll briefly look at Tim’s research on three potential Climate tipping points:-
– Arctic Sea-ice Loss
– Dieback of the Amazon Rainforest
– Ocean Current Circulation Systems
Artic Sea Ice Loss
The positive feedback effect around the melting of sea-ice in the Arctic means that this region is warming at more than twice the global average rate. This could lead to a tipping point that leads to the Arctic becoming free of sea-ice in summer. While this may have a positive effect of opening up shipping routes the impacts could have global consequences.
A transition to a system with much less sea-ice is already underway.

Greenland Ice Sheet

Ice sheets are much slower systems to the sea ice that take longer to melt. The majority of the Greenland ice sheet is resting on land and so is only affected by the ocean near the coasts. It could still pass a tipping point where it retreats completely on to land, leading to a 15% loss of the ice sheet – equivalent to 1m of global sea-level rise. Evidence from monitoring the retreat of glaciers around the coasts suggests this tipping point may already have been passed.
There is uncertainty as to where the tipping point lies for the irreversible melt of the whole ice sheet. Estimates range from a high probability of loss at 4°C to a much closer estimation of 0.7-1.7°C global warming.

Collapse of the West Antarctic Ice Sheet (WAIS)
Large parts of the WAIS are below sea-level. If a positive feedback is triggered resulting in retreat of the ice, it could result in the collapse of the ice sheet. Research shows this has happened before in past warm intervals. Major ice shelves are thought to need approximately 5˚C of warming to reach a critical threshold of melting, while the entire WAIS could require up to 8˚C.
“However, there is worrying evidence that part of the WAIS that drains into the Amundsen Sea is already in irreversible retreat and ultimately represents over 1m of sea level rise.
A further sign that the WAIS could be reaching an early tipping point would be the collapse of ice shelves. The most northerly of these are the Larsen ice shelves on the Antarctic Peninsula. Larsen A (the most northerly) collapsed in the mid-1990s. Larsen B – which has remained stable for the last 10,000 years – broke up rapidly in the summer of 2002. Larsen C is significantly larger than Larsen A and B, and in July 2017 an iceberg twice the size of Luxembourg calved from its front. This could be an early signal of much worse to come, but could also be part of a natural process of mass loss in this ice shelf.” -Professor Tim Lenton University of Exeter

Amazon Dieback
An astonishing 25% of global biodiversity is contained within the Amazon Rainforest making it one of the most ecologically important regions on Earth. The Amazon plays an important global role in carbon and nutrient cycling. It helps create local, regional and even global climate stability.
It’s pretty shocking therefore to think that a climate tipping point may be unfolding. Droughts in 2005, 2010 and 2015/6 could be a clue of impending Amazon dieback.
“Dieback is the process of death in trees or other vegetation. This can be due to a number of pressures, internal and external, including drought, disease or an unfavourable environment.”
The pressures on the Amazon and other tropical forests such as the Makira in Madagascar are many and could lead to dieback.
Human activity in the Amazon region is increasingand protective legislation is thin. Populist leaders are elected who’s priority is not to protect the rainforest. Deforestation and an increase in the number of forest fires across the region contribute to dieback.
Climate change is resulting in shifting rainfall patterns that could lead to the forest becoming Savannah.
Savannahs store less carbon than tropical rainforests, so the transition of the ecosystem to this new stable state would release carbon to the atmosphere and trigger extinctions. Savannah and seasonal forests cope better with dry conditions and more resillient to forest fires. This is what makes this new system a stable state.
“With fewer trees, there will be less forest transpiration, resulting in decreased surface cooling and higher regional air temperatures. Dieback of the Amazon rainforest would, therefore, exacerbate the impacts of climate change that are already being felt in this region.” – Professor Tim Lenton
A tipping point is predicted at temperature rises of 3-4˚C from pre-industrial levels (we’ve already reached 1˚C). However there are large uncertainties in the model predictions of rainfall changes across the basin, with models not fully capturing the complex microclimates that the rainforest produces.

Ocean Current Circulation Systems
“Circulation Systems control the movement of thermal energy (heat) around the world. This takes place in the atmosphere, through winds, and in the ocean.” – Tim Lenton University of Exeter

Atlantic Thermohaline Circulation (THC)
The deep, cold, salty water in the North Atlantic sinks as it becomes more dense, from the cooler temperatures and increased salinity. This is a delicate balance driving global ocean current circulation. Should an Ice sheets like the Greenland Ice Sheet melt it releases freshwater into the North Atlantic that has the potential to overturn circulation of this ocean current.

NASA Thermohaline circulation.
This current is important to us in the UK as it brings warmer water from the equator to the Northeast Atlantic giving the UK a mild climate for its latitude. If the circulation collapses it would bring much colder and harsher winters to Western Europe.
If we reach 4˚C of warming this century, the probability of THC collapse becomes “as likely as not” (1). While a full-scale transition may be a distant eventuality, the weakening of the THC has similar effects on a smaller scale.

El Nino Southern Oscillation (ENSO)
The El Niño / La Niña cycle is a natural cyclic phenomenon in the Pacific Ocean that occurs naturally roughly every 5 years. Climate change is amplifying the cycle. The 2015-16 El Niño was one of the strongest on record, following an exceptionally strong 1998 El Niño. It caused a global coral bleaching events including those witnessed by ourself in North-West Madagascar. It also caused droughts, hurricanes and significant flooding across the world. One of the controlling factors in the ENSO cycle is the thermocline of the ocean – a dividing layer that separates deep and surface oceans. As the surface oceans absorbs more heat due to climate change the thermocline gets sharper and steeper. Though there is some uncertainty the latest climate models predict more extreme El nino / La nina events as the century progresses.

Doesn’t this sound like science-fiction?
“The sensitivity of ocean circulation systems to climate change is poorly understood. We think that the rate at which change is occuring today will make tipping points more likely in the future. But those tipping points in the Earth’s circulation systems could still require another 3˚C of warming. Nevertheless, even modest changes to these enormous systems have global impacts that we are already seeing today.” – Professor Tim Lenton University of Exeter

Climate Change Summary

The evidence for man made Anthropogenic Climate change is overwhelming. We have a limited window of time for all of us – Governments, businesses and individuals to change the way we set policy, operate our businesses and live our lives.

As author David Wallace-Wells puts it in his book The Uninhabitable Earth –

“It is worse, much worse, than you think.

The slowness of climate change is a fairy tale, perhaps as pernicious as the one that says it isn’t happening at all, and if your anxiety about is dominated by fear of sea-level rise, you are barely scratching the surface of what terrors are possible, even within the lifetime of a teenager today.”

But before you get too depressed we do still have some time, and as individuals and businesses we can change things.

In the next post i’ll look at some of the things we have to do globally and collectively as businesses and individuals, as well as the more radical ‘panic button’ solutions that may become available. – Matthew

1. https://www.pnas.org/content/106/13/5041.full

2. Tipping Elements in the Earth’s Climate system – Professor Tim Lenton https://www.pnas.org/content/105/6/1786.full

3. Intergovernmental Panel on Climate Change report Global warming of 1.5 degrees C https://report.ipcc.ch/sr15/pdf/sr15_spm_final.pdf