Emergency on Planet Earth
Written by Dr Emily Grossman with the support
of the XR Scientists community. Fact-checked and reviewed by a wide range of experts in relevant fields - both from within the XR Scientists
community and external to it.
This guide is also available on the Extinction Rebellion UK website.
See here for a selection of key facts
from this guide. To save this guide as a PDF, select File -> Download ->
PDF Document.
Last updated 1st September 2020
***
The science
is clear
We are facing
an unprecedented global emergency
We must act
now
“We are in a
planetary emergency.”
Professor
James Hansen, Former Director NASA Goddard Institute for Space Studies
“This is an
emergency and for emergency situations we need emergency action.”
Ban Ki-Moon,
Former UN Secretary-General
"The
climate emergency is our third world war. Our lives and civilization as we know
it are at stake, just as they were in the Second World War."
Professor
Joseph Stiglitz, Economist, recipient of the Nobel Memorial Prize in Economic
Sciences
“Based on sober scientific analysis, we are deeply
within a climate emergency state but people are not aware of it.”
Professor
Hans Schellnhuber, Founding Director of the Potsdam Institute for Climate
Impact Research
“There is
sufficient evidence to draw the most fundamental of conclusions: now is the
time to declare a state of planetary emergency. The point is not to admit
defeat, but to match the risk with the necessary action to protect the global
commons for our own future.”
Professor
Johan Rockstrom, Director of the Potsdam Institute for Climate Impact Research
“Climate
change will lead to battles for food.”
Jim Yong Kim,
Former President of The World Bank
“Climate
change is the greatest security threat of the 21st century,”
Maj Gen Munir
Muniruzzaman (Retd.), chairman of the Global Military Advisory Council on
Climate Change
“You have to understand, this is also a crisis
for the world. The fact is that if the poor are suffering today, then the rich
will also suffer tomorrow.”
Dr Sunita Narain, Director General of the Centre
for Science and Environment
“Climate
change is moving faster than we are - and its speed has provoked a sonic boom
SOS across our world. We face a direct existential threat.”
António
Guterres, United Nations Secretary-General
"We have
all the resources we need to deal with this. There is nothing magical about
reducing carbon dioxide in the atmosphere. We just don’t have the political or
economic will to do this.”
Professor
Stephan Harrison, Professor of Climate and Environmental Change, University of
Exeter
“Listen to
the cry of the earth and the cry of the poor, who suffer the most. The urgent
need for interventions can no longer be postponed.”
Pope Francis
“The future
of the human race is now at stake.”
Rowan
Williams, Former Archbishop of Canterbury
Introduction
Humanity is
facing a crisis unprecedented in its history. A crisis that, unless immediately
addressed, threatens to catapult us towards the destruction of all we hold
dear, our planet’s ecosystems and the future of generations to come. This
crisis has been caused by human activities and we have to stop making it worse
or we will face catastrophe that we cannot think our way out of, invent our way
out of or buy our way out of. In one way or another, it will affect every one
of us and everything we love.
The science is clear: the world is heating and
the breakdown of our environment has begun. Even now, warmer temperatures are
wreaking havoc, causing an increase in extreme weather, floods, storms and
droughts - along with rising sea levels, heat stress in our oceans and
degradation of our soils. Extreme weather events are having devastating impacts
on agriculture and destroying homes, costing taxpayers billions of dollars and
leaving millions of people in need of humanitarian aid.
If we keep going as we are, the coming years will
bring more wildfires, unpredictable super storms and scorching heatwaves.
Rising sea levels and droughts could render vast tracts of land uninhabitable
through flooding and desertification, putting food supplies at risk. Receding
glaciers threaten to cut off fresh water supplies for millions. Mass migration
and famine are likely to take us towards civil unrest and ultimately war,
raising the terrifying possibility of societal collapse.
But that’s not all. Around the world,
biodiversity is being annihilated at a terrifying rate. Population sizes of
thousands of species of mammals, birds, fish and reptiles have fallen by 60%
since the 1970s. We are losing our crop-pollinating insects and soil-rejuvenating
earthworms. Species are going extinct 100 to 1,000 times faster than they would
be doing naturally. Many scientists say we are now entering the Earth’s Sixth
Mass Extinction event, with one million species threatened with extinction -
many within decades. Only this time it’s our fault. The consequences will be
catastrophic if we do not act swiftly.
Millions of our trees are being felled to feed
the ever-increasing demands for palm oil, clothes and meat. Our soils are being
degraded through deforestation and intensive agriculture. We are running out of
raw materials and using up our resources. Our rivers are being poisoned and our
seas are acidifying and filling up with plastic. The air is so toxic that it
kills millions each year.
As Sir David Attenborough
put it: “We are facing a man-made disaster on a global scale.”
These climate and ecological crises can no longer
be ignored or denied. Yet in spite of promises from governments, greenhouse gas
emissions continue to rise steeply and biodiversity loss shows no sign of
slowing.
In November 2019, a group of more than 13,000 scientists from 153 countries declared “clearly and unequivocally that the Earth is facing a climate emergency” and that without deep and lasting
changes, the world’s people face "untold human suffering".
The time has come to take radical action. The future
of our children, and our grandchildren, is at stake.
This horrifying narrative sounds
almost too unbelievable to be true. Can it really be as terrifying as all that?
We hear so many conflicting opinions and reports –
how do we know for sure what is true? Can we really be sure that the world is
warming any more than it has in the past? And even if it is, are we certain
that humans are to blame? Are species really going extinct at such high rates?
And even if they are, why does this matter to us? Are things really going to
get worse? If so, how much worse? And how soon? And what can we do about it?
Over the following sections, we, an expert group of science writers, climate scientists and ecologists, most of
whom are members of the Scientists for Extinction Rebellion community, explain
simply what’s really going on on our planet today. We present clear and
unequivocal evidence - backed up by the latest research - that we are indeed in
a state of planetary emergency, that human activities are to blame for this
crisis, and that the arguments often used by skeptics or deniers to contest
this fact are simply not true and are designed to avoid action.
We also provide clear evidence that our governments
are not doing nearly enough to address the crisis. And we explain why, without
bold and radical action within the next few years, the impacts of this
emergency will be catastrophic and irreversible, leading to incalculable
suffering and loss of life.
We show that the time has come to take radical action.
That the future of our planet is at stake. And that we cannot afford to wait
another second.
Contents
Part 1: Back to the start… How did we get into this climate mess and is it really that bad? 9
How can we be so sure that the Earth is heating? 9
Why should we care about a few degrees of heating? 12
Hasn’t the Earth been hotter in the past? 13
What exactly are greenhouse gases and what is the greenhouse effect? 15
Can we be certain that humans are causing global heating? 17
Haven’t natural fluctuations in carbon dioxide affected the Earth’s temperature? 19
What’s happened in the past few thousand years? 21
What’s happened in the past 150 years? 21
What are greenhouse gas emissions like today? 23
We have been warned over and over! 24
Part 2: It’s getting hot in here… What’s already happening to our planet as a result of global heating and why? 27
What is already happening to our weather? 27
Longer and more intense heatwaves 29
Longer and harsher droughts 31
More extreme storms and floods 33
What is global heating doing to our oceans, coastlines and wildlife? 38
Melting ice and rising seas 38
Loss of homes due to rising seas 41
Impacts of heating on ocean life 42
Impacts of carbon dioxide on ocean life 43
Impacts of heating on land-based wildlife 43
Part 3: The lie of the land… What other damage are we doing to our planet? 46
How are we damaging our land and our waters? 46
Loss of grasslands, mangroves, wetlands and peatlands 52
How are we polluting our waters? 53
How are we polluting our air? 54
How are we destroying our wildlife? 55
Why should we care about the loss of our wildlife? 55
Loss of fish, whales and dolphins 58
Part 4: Sick, thirsty, hungry and homeless… What knock-on effects are we already seeing? 64
Health threats from extreme weather 64
Increased spread of diseases 65
Health threats from air pollution 67
Health threats from intensive agriculture 68
Children and the elderly are especially vulnerable 68
Impacts on global food production 69
Impacts on water availability 71
Mass displacement and threats to safety, human rights and our global economy 72
Part 5: Too hot to handle… Where are we heading? 75
How hot is too hot? The promises of the Paris Agreement 75
How hot is it likely to get and when? 76
The additional risks of feedback loops 79
Drying soils and mega-heatwaves 82
How tipping points might make things even worse… 83
The compound risk of multiple tipping points 87
What will our world look like in 2050 if we don’t take radical action now? 89
2050: More intense heatwaves and forest fires 89
2050: More intense storms, floods and hurricanes 91
2050: Increased droughts and water shortages 91
2050: Rising seas and increased coastal flooding 93
2050: More devastating loss of wildlife on land and in the oceans 94
2050: Further reductions in food production 95
2050: More devastating impacts on human health 97
2050: Poverty and financial instability 98
2050: Social instability and conflict 98
What will our world look like by the end of the century? 99
2100: Flooding and mass migration 100
2100: Impacts on human health, food and water 101
What will our world look like by the end of the century if we reach 4°C of heating? 102
4°C of heating: Extreme heat 103
4°C of heating: Rising seas, flooding and mass displacement 105
4°C of heating: Wildlife loss 105
4°C of heating: Reductions in food production 106
Not worth the risk: why we need to apply the Precautionary Principle 106
Part 6: Enough is enough… How are our governments letting us down? 109
What are governments ‘supposed’ to be doing to address the ecological crisis? 109
What are governments ‘supposed’ to be doing to address the climate crisis? 110
It’s not just WHEN we get to net zero, it’s HOW 111
Why net zero by 2050 isn’t actually fast enough 112
Why richer countries need to get to net zero MUCH sooner than 2050 113
How our governments are making the climate crisis worse, not better! 114
Emissions from shipping and aviation are on course to reach dangerous levels 115
Governments are still subsidising fossil fuels 115
Governments are approving NEW fossil fuel projects 116
Banks are financing the fossil fuel industry 118
The way that governments invest money in emerging from the coronavirus crisis is crucial 118
Is the UK government doing enough? 118
UK emissions are falling - but only in some sectors 119
UK figures don’t account for aviation, shipping or embedded emissions 119
UK emissions are not falling nearly fast enough 120
The UK government is missing its own targets 121
The UK needs to be getting to net zero by 2025, not 2050 122
The UK government is making things worse, not better! 123
The UK government is subsidising fossil fuels 123
The UK government is approving NEW fossil fuel projects 124
UK banks are investing in fossil fuels 124
But the UK only emits 1.5% of the world’s carbon, shouldn’t we be focusing our efforts elsewhere? 125
Part 7: Act now… So what do we do? 127
How long do we have and is it already too late? 127
So what needs to happen now? 127
Why individual action isn’t enough 128
The urgent need for collective action 129
Testimonials: What other scientists, political voices and readers are saying about this guide 147
In the media: Talks, articles, interviews and short films about this guide 149
Part 1: Back to the start… How did we get into
this climate mess and is it really that bad?
How
can we be so sure that the Earth is heating?
“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, and sea level has
risen.”
Intergovernmental
Panel on Climate Change (IPCC) Fifth Assessment Report
“Join the
dots. It's happening. It's happening in your world, it's happening in my world.
And let's be very clear about this - it is going to get much worse.”
Dr Sunita
Narain, Director General of The Centre for Science and Environment
Independent temperature records from multiple official
sources confirm that there is absolutely no doubt whatsoever that the Earth is heating.
Each of the last three decades has been successively
hotter than the one before, 19 of the top
20 hottest years have occurred in the last 19 years, and the past four years have been the hottest on record. 2016 was the hottest year
ever recorded, whilst in 2019, nearly 400 temperature records were broken across 29 countries, June 2019
was the hottest on record, and July
2019 was
the
hottest
month
ever
recorded. As of July
2020, January 2020 was the warmest January ever recorded in Europe, we saw the hottest May ever
and we already have an 85% chance that 2020 will turn out to be the hottest year on record.
Some people argue that global heating can’t be
happening because the weather seems to be getting colder where they live. This
may indeed be true, but what’s important to remember is that when we talk about
global heating and climate change, we are talking about changes
in long-term average trends in atmospheric conditions - normally
measured over decades - whereas when we talk about the weather we
are referring to short-term and local variability around that average.
What this means is, whilst we are clearly seeing an
overall increase in average global temperatures, there can still be significant regional and yearly variations in the weather. In any one
year there may be some parts of the world that are colder than usual, and there
may be entire years that are colder than previous years. Indeed,
those wishing to confuse the public that global heating isn’t occurring
sometimes do so by pointing to misleading graphs that are based on false or misinterpreted data that refers to regional as opposed to global changes, or cherry-pick data that focus on short-term trends rather than looking at the bigger picture.
The key point is that long-term and global
trends show unequivocally that our planet is not only heating up, but that its
rate of heating is accelerating. In fact, it has even been proposed that it is
climate change itself that is causing some regions to experience more extreme,
colder
winters
due
to
the
disruption
to
weather
patterns.
It’s also worth noting that there is variation in how
fast the climate is changing in different parts of the world. For example continental regions (where most people live) heat up much faster than the oceans. An extreme example of this
is the Arctic, which is warming at more than twice the rate of the global average due to
a phenomenon called Arctic Amplification. In
contrast, there are areas of the globe that are warming a bit slower than the
average.
Why
should we care about a few degrees of heating?
"It is
generally foolish to bet against the judgments of science, and in this case,
where the planet is at stake, it is insane.”
Professor
Steven Weinberg, Nobel-Prize winning Theoretical Physicist, 2018
Over the past 12,000 years the Earth’s climate has
been remarkably stable. It was this stability that gave the predictability and
security that was needed for agriculture and human civilisation to develop,
without which we could not have flourished. However, the burning of fossil
fuels, large-scale deforestation and intensive farming practices that have been
taking place since the start of the Industrial Revolution are causing us to now
rapidly leave that period of climate stability behind and head into the
unknown. As a result, we risk disrupting our planet’s environmental conditions way
beyond that which we can adapt to. Indeed, we are already beginning to see
the consequences - see section on what’s already happening to our planet as a result of global heating.
The average surface temperature of our planet has now risen by around 1°C since pre-industrial times. One
degree may not sound like much, but the Earth is so massive that it takes a
colossal amount of energy to warm it by even a tiny amount. In fact, the
current rate of global heating is the equivalent energy of five nuclear bombs going off every second. Adding this
much energy to the Earth’s climate inevitably has huge knock-on effects,
causing extreme weather events
across the globe, melting ice caps
and disrupting life on land
and in our oceans,
which puts stress on agriculture
and endangers fresh water supplies.
The rise in global average temperature between the last ice age (over 17,000 years ago) and today is 4.5°C - yet we could see a similar amount
of heating by the end of this century, in a fraction of the time.
At just 1°C of global heating, climate change is already
here and is having devastating impacts
on people and ecosystems across the world. Every fraction of a degree of
further warming will not only exacerbate these impacts but also
increase the risk of triggering irreversible tipping points.
We are on course for things to get an awful lot worse over the coming decades
unless we act radically and act NOW.
Yet our governments continue to procrastinate
and delay meaningful action.
Hasn’t
the Earth been hotter in the past?
"You'd
have to go back to the last interglacial [warm period between ice ages] about
125,000 years ago to find temperatures significantly higher than temperatures
of today."
Dr Carrie
Morrill, paleoclimatologist at the National Climatic Data Centre
The planet is now very probably hotter than at any point in at least the last
125,000 years, long before human
civilisation began, when sea levels reached over 6 m higher than they are today.
But what’s even more concerning is how fast our
temperatures are rising. Over the past 45 years, our planet’s temperature has
been increasing a whopping 170 times faster than the baseline rate of cooling over the previous 7,000 years. Indeed, our current rate of warming is unprecedented over the last 10,000 years.
Global temperatures over the past 11,300 years
compared to the average between 1961 and 1990
Over the rest of this century, future temperature
rises are predicted to be taking place not just much faster than it did during
our recovery from the last ice age but hundreds of times faster than any extended period of warming in the last 65 million years. That’s when the dinosaurs
went extinct. Crucially, when temperatures rise this fast, it is impossible for
many living creatures and plants to have time to adapt to such changes.
Not to mention the fact that many places on Earth that creatures would have
previously used to take refuge from increasing temperatures have now been
degraded, fragmented or colonised by human activities.
To make matters worse, geological records show that
there have been some incidences of abrupt climate change in the past,
when just a small change in one element of the climate system led to rapid changes
in the whole system that have taken place over the course of centuries or even
decades. This suggests the terrifying possibility that if we push global
temperatures over a certain threshold today (which could happen at any time), we could trigger abrupt, unpredictable and potentially irreversible changes over the course of decades or even years - leading to
large-scale impacts and massive disruption.
The bottom line is that the changes in temperatures
that we’ve been seeing on our planet in recent years are truly unprecedented.
At a time when sunspot activity
is decreasing and when, according to the Earth’s natural orbital cycles, we
ought to be cooling down and heading slowly towards our next ice age (see section on the effects of natural fluctuations in carbon dioxide), instead, greenhouse gases (such as carbon dioxide) from
human activities are causing global temperatures to rise at a terrifying rate.
As our carbon dioxide levels reach concentrations not
observed for millions of years (see section on what greenhouse gas emissions are like today), we will inevitably soon
surpass any past climates experienced by humans.
What
exactly are greenhouse gases and what is the greenhouse effect?
"Everything
that is expected to result from global climate change driven by greenhouse
gases is not only happening, but it’s happening faster than anybody expected.”
Professor
John Holdren, Science and Technology advisor to President Barack Obama,
Director of the Woods Hole Research Center
The temperature at the Earth’s surface is controlled
primarily by the levels of certain gases in the atmosphere, such as water
vapour, carbon dioxide and methane. Although these gases only make up a tiny
fraction of our atmosphere (current carbon dioxide levels are around 410 parts
per million (ppm), which is just 0.041%), just like how a drop of ink can affect the colour of a huge volume of water, tiny amounts of these gases
can
have
enormous
impacts on our
atmosphere. Due to their special structure, these
molecules can absorb heat emitted from the Earth’s surface
as a result of it having been warmed by the Sun, preventing some of that heat
from escaping back out into Space. In this way, it can be said that the gases
provide an insulating ‘blanket’ around the Earth, which traps heat in our
atmosphere keeping us warm.
This heating effect has (somewhat wrongly) been
compared to how the glass roof of a greenhouse traps heat energy from the Sun,
keeping the inside of the greenhouse warmer than its surroundings. Hence this
phenomenon has become known as the greenhouse effect and the gases known
as greenhouse gases. We have known about the greenhouse effect for well over 150 years, and the science behind
it is well established.
The greenhouse effect, in its natural form, is
essential for life here on Earth; without greenhouse gases in our atmosphere,
the average temperature at the Earth’s surface would be around -18°C, dropping
to temperatures at night that would be far too cold for us to survive. However,
by burning fossil fuels (as well as by farming cattle, growing rice, burning trees, intensively ploughing soil and using chemical fertilisers) humans have
been adding huge quantities of additional greenhouse gases into the
atmosphere, ‘supercharging’ the greenhouse effect beyond anything that humans
have ever experienced.
How the Greenhouse Effect works
Carbon dioxide is by far the most important greenhouse
gas - responsible for approximately 75% of the Earth’s human caused heating -
because it is emitted in much larger quantities than any of the
other ‘long-lived’ greenhouse gases. It also has an extremely long lifetime:
any excess can stay in the atmosphere for hundreds or even thousands of years and therefore it accumulates
in our atmosphere, increasing its concentration. Concentrations of carbon
dioxide have now increased by over 40%, from around 280 ppm in preindustrial
times to over 414 ppm
in July 2020 and rising.
Other greenhouse gases are important too though. For
example, methane is a very potent greenhouse gas, being 86 times better than carbon dioxide at trapping
heat over a twenty-year time frame. However, on average, it breaks down in the
atmosphere in around 9 years, meaning that it can’t
accumulate in the atmosphere as much as carbon dioxide over long time periods.
Yet even over a 100-year time frame, methane is still approximately 34 times more potent than carbon dioxide. Plus, when
methane breaks down it actually turns into carbon dioxide. Methane concentrations
in the atmosphere have more than doubled since pre-industrial times, recently exceeding 1.8 ppm.
Per kilogram, nitrous oxide is an even more powerful greenhouse gas than methane, with nearly 300
times the global heating potential of carbon dioxide and a lifetime somewhere
between that of carbon dioxide and methane - roughly 120 years. Levels of nitrous oxide have
increased by around 22% since the preindustrial period.
Water vapour is also a greenhouse gas and occurs in
our atmosphere in higher concentrations than carbon dioxide. However, the
amount of water vapour in the atmosphere is controlled by the temperature of
the air (increasing by around 7% with every degree celsius of increase
in air temperature), rather than by human-caused emissions. For that reason, the amount of water vapour in the air is seen as an ‘amplifying feedback’ that increases global heating, rather than the initial cause
of such heating.
Can
we be certain that humans are causing global heating?
“Human influence on the climate system is
clear, and recent anthropogenic emissions of green-house gases are the highest
in history.”
Intergovernmental
Panel on Climate Change (IPCC) Fifth Assessment Report
There is now absolutely no doubt that the recent
increase in global temperatures is almost entirely due to human factors.
A vast body of peer-reviewed scientific evidence confirms that natural cycles,
volcanic activity, galactic cosmic rays and changes in solar activity from
sunspots have had a negligible effect on our current temperature rise. Instead, rises in global
temperature have followed the trajectory of increased greenhouse gas levels.
Indeed, scientists have been able to find an
unmistakable “human fingerprint” on climate
change. Firstly, the Earth’s atmosphere is reacting exactly as we would expect it to if it were being exposed to an increase in greenhouse gases (as opposed to, for
example, if it were experiencing increased solar activity). Secondly, detailed analysis of the carbon atoms in the carbon dioxide
accumulating in the atmosphere shows that they must have been released by the burning of fossil fuels. Thirdly, measurements taken
by satellites show that increases in greenhouse gases are trapping infra-red radiation from the Earth
and causing the atmosphere to heat up.
Such evidence confirms that the direct impact of
humans on our global climate is no longer a matter for debate. Indeed, an
analysis of 12,000 academic papers on the subject of
climate change published from 1991-2011 found that 97% of the papers that expressed a position agreed that humans are responsible for the exceptional levels of global heating
that we are seeing today. To be clear, this doesn't mean that the other 3% disagreed;
it just means that their work didn't meet the threshold to show that they
agreed. The consensus has only gotten stronger: more recently, analysis
of 11,602 peer-reviewed articles on “climate change” and “global warming”
published in 2019 found 100% agreement that it is human activity that is
responsible for this.
Whilst climate change deniers sometimes post articles
or comments from scientists that seem to refute the overwhelming evidence of
human-caused global heating, these articles often rely on inaccurate claims about climate science. The
scientists themselves tend not to have expertise in a climate-related field, or they have links to the fossil fuels industry -
or both.
The scientific community as a whole are overwhelmingly concerned about what
is going on on our planet. In the words of Professor Lonnie Thompson, director
of the Byrd Polar Research Centre: “Virtually all of us are now convinced that
global warming poses a clear and present danger to civilization.”
Haven’t
natural fluctuations in carbon dioxide affected the Earth’s temperature?
"At
present rates of human emissions, there will be more CO2 in Earth’s
atmosphere by 2025 than at any time in at least the last 3.3 million years."
Dr Elwyn De La Vega, University
of Southampton
In the absence of
human activities, the levels of carbon dioxide in our atmosphere tend to
remain fairly stable over time. Carbon dioxide is constantly being absorbed
into the oceans, and locked into carbon compounds in trees and plants by a
process called photosynthesis. Other living creatures feed off these
trees and plants, taking the carbon compounds into their own bodies. These
carbon compounds are then turned back into carbon dioxide through a process
called respiration, and the carbon dioxide is released back into the
atmosphere. Carbon dioxide is also released when dead matter decays and rots,
or is burnt. This process of the constant removal and replacement of carbon
dioxide in our atmosphere is known as the carbon cycle.
Whilst analysis of air bubbles trapped in Antarctic
ice sheets reveals that over the past 800,000 years there also have been periods in the Earth’s history where the carbon dioxide levels have naturally risen and fallen, this has taken place extremely
gradually. These changes are brought about by natural variations in the way in which the Earth travels around the Sun (known as Milankovitch
cycles), which lead to changes in the absorption of sunlight on Earth. For
example, a small increase in the amount of sunlight being absorbed causes the
oceans to warm slightly, which results in some of the carbon dioxide dissolved
within them being released back into the atmosphere. The increase in
atmospheric carbon dioxide leads to more ocean warming, which causes more
carbon dioxide to be released, which causes more warming... and so on and so
forth. The changes in temperature caused by this feedback loop, and others like
it, drive the transitions into ice ages (glacial periods) and back out of them
(interglacial periods). The last time this happened was around 17,000 years
ago, when we began to transition out of our most recent ice age.
The key point here is that these natural
changes in carbon dioxide levels, triggered by cycles in the Earth’s orbit and
modulated by feedback cycles within the Earth system, take place over tens
of thousands of years. In contrast, the extremely rapid increases in carbon
dioxide levels that we have been seeing over the past 60 years, due to human
actions, have been taking place about 100 times faster than any of these previous natural increases.
Carbon dioxide levels today are higher than they have been in more than 3 million years. Back
then, global average temperatures were 2-3°C higher than in pre-industrial
times and sea levels were a whopping 16 m higher. Studying these past changes has revealed to climate scientists
just how sensitive the Earth system is to changes in greenhouse gas
concentrations. This is one of the key reasons why scientists are so alarmed
about the current rapid rise in their concentrations.
What’s
happened in the past few thousand years?
Around 17,000 years ago the Earth began to come out of
its most recent ice age. As carbon dioxide levels
naturally rose, the planet warmed. Then, about 12,000 years ago, global temperatures reached a plateau and we entered a period of relative climatic stability known as the Holocene. It is this
stability that allowed humans to settle and farm. Then, around 5,000 years ago,
greenhouse gas levels started to naturally fall again and temperatures began a slow decline, which would
eventually have sent us towards our next ice age.
However, a few thousand years ago, human actions began to disrupt the Earth’s natural cycles. We started cutting down
trees to clear land for farming or to burn them to keep warm - reducing the
amount of carbon dioxide that could be removed from the atmosphere by
photosynthesis. At the same time, we planted paddy fields to grow rice, releasing methane into the atmosphere from microbes growing in waterlogged soils. For a long period of time the levels
of greenhouse gases in our atmosphere rose slowly and steadily. It has been proposed that this increasing greenhouse warming effect counteracted what should have been a period of natural cooling due to the Earth’s orbital cycles, leaving our global
temperatures to remain pretty constant.
That is, until the last couple of centuries. With the
start of the Industrial Revolution came mass burning of fossil fuels,
large-scale deforestation and intensive farming. As a result, the levels of
greenhouse gases began to shoot up astronomically. And with them, our temperatures.
What’s
happened in the past 150 years?
“In just 100
years, fossil fuel use has more than undone 5000 years of natural cooling. It's
hotter now than any time in the history of human civilisation. We are catapulting
ourselves out of the Holocene into uncharted territory. Current life on Earth
is not adapted to this.”
Stefan Rahmstorf, Professor
of Physics of the Oceans at Potsdam University
Since the Industrial Revolution, humans have been
pumping enormous additional quantities of carbon dioxide into the atmosphere
due to the burning of fossil fuels: coal, oil and natural gas. Fossil fuels are
naturally occurring substances that were formed millions of years ago from the
remains of dead plants and sea-creatures. When these fuels are burnt, the
carbon compounds that have remained trapped underground for millions of years
are converted into carbon dioxide and released, adding extra carbon dioxide
into the atmosphere that would not naturally be there.
In addition, deforestation on massive scales to clear land for agriculture and livestock has released huge amounts of carbon dioxide back into the atmosphere,
and has also meant that there are increasingly fewer trees to absorb excess
carbon dioxide from the air (see section on deforestation).
At the same time as humans have been burning fossil
fuels and clearing forests, they have also been churning up our planet’s soils
through intensive farming practices. Healthy soils hold around 70% of the planet’s land-based organic carbon. However, when soil is
repeatedly ploughed or compacted by heavy machinery or livestock, its ability
to store carbon is compromised and vast quantities are released back into the
atmosphere in the form of carbon dioxide (see section on soil degradation). The graph
below shows just how strikingly carbon dioxide levels have changed over the
past 1,000 years.
Carbon dioxide levels in the atmosphere over the
past 1,000 years
It’s not just carbon dioxide levels that are
increasing due to human actions. Methane levels have more than doubled in the last 150 years. Leaks from the oil
and
gas
industry contribute
heavily to the amount of methane in our atmosphere, but the
waste
sector
and
agriculture
are
also
major
sources. There has
also been a huge increase in the number of rice-producing paddy fields and in
the breeding of cattle for the meat and dairy industries. Microbes in the
waterlogged soils of flooded rice fields release large quantities of methane,
as do cows and sheep when they burp and fart due to the presence of similar
kinds of microbes in their stomachs that help them to digest grass. In
addition, fertilisers and animal waste produce large quantities of nitrous oxide, increasing its levels by around a third in the past 150 years. (See sections on intensive agriculture and livestock farming).
As our greenhouse gas emissions have risen, so too
have global temperatures.
What
are greenhouse gas emissions like today?
“More than
half of all industrial emissions of carbon dioxide since the dawn of the
Industrial Revolution will have been released since 1988”
Dr. Peter C.
Frumhoff, Director of science and policy at the Union of Concerned Scientists
Due to a deadly combination of burning fossil fuels
and changes in land use, we are currently pumping out a whopping great 110
million tonnes of carbon dioxide into the atmosphere every 24 hours. That’s over 40 billion tonnes a year! Over the past 60 years, the
annual rate of increase in atmospheric carbon dioxide has been about 100 times faster than any previous natural increase in at least
the last 800,000 years, such as those that occurred at the end of the last ice
age around 12,000 years ago - see graph in section on how natural fluctuations in carbon dioxide have affected the Earth’s temperature.
Carbon dioxide concentrations are now over 414 parts per million and rising, an increase of over 45% on pre-industrial levels. That’s
the highest level seen in at
least the last 3 million years.
The scary thing is that because carbon
dioxide stays in the atmosphere for such a long time, even if we completely stopped emitting it today we would not reverse
the warming that it has caused. It's like filling a bathtub with the plug in it: the water level will keep
going up as long as the tap is on, but once you turn the tap off it won’t go
down unless you remove water from the tub. Likewise the level of carbon
dioxide and the heating it causes depends on the total amount of carbon dioxide emitted over time, and temperatures will
not
go
back
down
even
once
we
stop
emitting
carbon
dioxide. If we want
to reduce global temperatures, we will have to actively remove carbon dioxide from the atmosphere,
something which might be impossible to do at the scale required.
This means that the only way we can definitely avoid
catastrophic and irreversible damage to our planet is if we reduce carbon
dioxide emissions to zero before we reach the level of heating that
would cause such changes. This leads to the concept of a “carbon budget” - the maximum amount of
carbon dioxide we can emit over the whole century if we want to stay below a
certain temperature.
The picture is slightly better for the shorter-lived
greenhouse gases, such as methane. Just like how in an unplugged bathtub
the water level will drop as soon as the tap is turned off, if we stopped
emitting methane today, the amount that it heats the atmosphere would drop almost immediately. This makes
reducing methane emissions a very effective way to slow the rate of global heating.
However, there is much more carbon dioxide in the air
than other greenhouse gases and it stays in the atmosphere for longer, so
reducing carbon dioxide emissions is still the most important factor in determining how much the
Earth heats up overall. So if we want to keep the global temperature
rise to below 1.5°C, it is essential that we rapidly reduce global emissions of both short- and long-lived greenhouse gases.
Yet despite all the policies and pledges from the
government, global greenhouse gas emissions continue to shoot up at an alarming rate. Whilst there has been a recent drop in emissions due to the COVID-19 pandemic, the short term effects on climate will be minimal, and unless
concerted effort is taken to stop fossil fuel development in the recovery
period it will only be a temporary dip in a long-term upward trend. If this is
a hole we need to get out of, we’re still digging.
Indeed, Fatih Birol, executive director of the
International Energy Agency and one of the world’s foremost energy experts has
warned that we have to act quickly if we want to change the course of the climate crisis and prevent a post-lockdown
rebound in greenhouse gas emissions that would overwhelm efforts to stave off
climate catastrophe. Birol said: “This year is the last time we have, if we are
not to see a carbon rebound.”
We
have been warned over and over!
"Future
generations are unlikely to condone our lack of prudent concern for the
integrity of the natural world that supports all life"
Rachel
Carson, SIlent Spring, 1962
The risks of climate change and ecosystem collapse as
a result of human action have been known about for many decades. Yet global
greenhouse gas emissions have continued to rise steeply.
In 1949, Professor Aldo Leopold, ecologist at the
University of Wisconsin, made clear the damage we were doing to our land:
"One of the penalties of an ecological education is that one lives alone
in a world of wounds. Much of the damage inflicted on land is quite invisible
to laymen. An ecologist must either harden his shell and make believe that the
consequences of science are none of his business, or he must be the doctor who
sees the marks of death in a community that believes itself well and does not
want to be told otherwise."
Global warming and its associated risks have been
known about for over 40 years. Back in the 1970s, American multinational oil
and gas corporation Exxon were aware of the likelihood and risks of human caused climate change.
In 1988, climate scientist James Hansen testified
before the US congress, provoking the New York Times headline: “Global Warming Has Begun, Expert Tells Senate”. That same year, the Intergovernmental Panel on Climate Change (IPCC) - a massive body of thousands of
scientists who volunteer their time to review the science relating to climate
change - was founded as part of the United Nations to inform international
negotiations. Since then the IPCC has published five massive reports, and many
more interim reports, detailing the science of climate change in ever-starker
detail.
Yet the warnings were ignored or down-played.
In 1992, the Union of Concerned Scientists, including
the world’s leading scientists and the majority of living science Nobel
laureates, published the “World Scientists’ Warning to Humanity”, calling on humankind to curtail
environmental destruction and warning that “a great change in our stewardship
of the Earth and the life on it is required, if vast human misery is to be
avoided.” The authors feared that humanity was pushing Earth’s ecosystems
beyond their capacities to support the web of life, and described how we are
fast approaching many of the limits of what the biosphere can tolerate without
substantial and irreversible harm. They implored that we cut greenhouse gas
emissions and phase out fossil fuels, reduce deforestation, and reverse the
trend of collapsing biodiversity. Indeed, a few years later, in 1995, the UN
Environment Programme also warned that the Earth’s biological resources were under serious threat.
The warnings were still not heeded. On the contrary,
the rate of greenhouse gas accumulation in the atmosphere between 1987-2019
(since when the dangers were first known) was four and a half times faster
than it was between 1955-1986. In fact, more than half of our total fossil fuel emissions have been emitted in the last three decades. The graph below shows just how rapidly
and how consistently our emissions have been rising, even since various
climate warnings have been issued and climate treaties negotiated.
In 2017 there followed a second, even more urgently
worded letter from the Union of Concerned Scientists: “World Scientists’ Warning to Humanity: A Second Notice”, which was signed by more than
15,000 scientists. A few years later, the urgency was made crystal clear by
more than 13,000 scientists from 156 countries who signed the “World Scientists’ Warning of a Climate Emergency”. In it they declared that “Scientists
have a moral obligation to clearly warn
humanity of any great existential threat … Based on this obligation and
the data presented below, we herein proclaim ... a clear and unequivocal
declaration that a climate emergency exists on planet Earth.”
Now, after almost 40 years of warnings and 30 years of
international climate negotiations, we have precious little to show for it. On
the contrary, carbon emissions from burning fossil fuels have increased by over 50% since 1990. If we are to prevent
disaster the time for action is now.
As Professor Sherwood Rowland, Nobel Prize Winner in
Chemistry for discovering how we were destroying the ozone layer said: “What’s
the use of having developed a science well enough to make predictions if, in
the end, all we’re willing to do is stand around and wait for them to come
true?”
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