Surviving C21 - Julian Cribb
Julian Cribb
Julian Cribb is a distinguished science writer with more than thirty
awards for journalism.
He was a newspaper editor, founder of the
influential ScienceAlert website and is the author of 10 books:
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In all the sound
and fury over climate change, too little public and media attention
has been devoted to the
‘methane gun’ – and yet this terrifying phenomenon could usher humans
unceremoniously off Earth’s stage for good.
Like CO2, methane
(CH4) is a greenhouse gas that helps trap the sun’s heat within the
Earth’s atmosphere. The big difference is that it is 25-84 times
more potent at doing so.
The planet has
massive stores of methane, locked as frozen ice in the seabed (the
world’s largest natural gas reserve), in the frozen soils of the
Canadian, US and Russian Arctic, and buried in the sediments of
tropical swamps and peatlands. Like the bubbles in a stagnant pond,
the gas is mostly the work of bacteria digesting organic matter over
millions of years.
How large these
reserves of methane are is still a matter for scientific debate –
but estimates fall between 1.5 and 5 trillion tonnes. Very, very
large indeed. If released suddenly, these are thought more than
capable of driving the Earth’s temperature up by another 7-10
degrees, on top of the 2-5 degrees likely to result from human
emissions from burning fossil fuels and clearing land (
currently
rising at record rates).
The worst-case
scenario – a large-scale, rapid release of trapped gas known as the
‘methane gun’ – could potentially render the Earth
uninhabitable by humans and other large animals. This is why we need
to pay attention. Now.
What has some
scientists concerned – and others frightened – is that
atmospheric levels of methane which have doubled since the Industrial
Revolution and have been rising for steadily for the past 30 years,
began to rise more steeply in the past five years, as the following
graph shows:
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| Atmospheric methane concentrations up to October 2019: Mauna Loa Observatory, USA. |
The source of the
new methane is debated. Is it mainly caused by the mining of natural
gas, petroleum and coal – as several lines of evidence suggest? Is
it released by expanding world cattle and rice production, the
draining of tropical swamps and burning of tropical forests? Is it
the frozen gas seeping out of the oceans and tundra as the planet
warms and its ice vanishes? Or is it all of the above?
The evidence
is starting to favour the latter view – but the scientific jury remains undecided.
We know that a
mass-release of methane can be catastrophic for life on Earth,
because that’s exactly what took place 55 million years ago in an
event known as PETM - the Palaeocene-Eocene Thermal Maximum - when
global temperatures shot up by 5-10 degrees,
wiping out a number of
species. There were no humans round then to release carbon, so it was probably
due to one or more of the natural sources rapidly giving up its gas.
Recently opinion has narrowed in favour of tropical swamps and
peatlands drying out and catching fire during a warming cycle, as the
main source. The frozen methane, apparently, remained largely
undisturbed in the ocean and tundra.
But that is not
the case today. Not only are tropical forests burning and swamps
being drained, but scientists have observed major escapes of methane
from the Arctic tundra in the form of exploding pingos – mounts of
frozen methane, mud and water – and the eruption of melted methane
ice from the seabed. In October 2019 veteran Russian researcher Igor
Semiletor, from Tomsk Polytechnic University, reported “the most
powerful seep I have ever been able to observe”
venting in a potent
eruption of gas bubbles in the East Siberian Sea.
Two years
earlier, in June 2017, Russian reindeer herders reported a violent
explosion that left a 50- metre deep crater in the tundra of the
Yamal Peninsula, Siberia, which scientists attributed to a methane
blast. In recent years researchers have reported numerous craters
left by explosions across Siberia, the Canadian and Alaskan tundra –
and even craters in the seabed. Many are recent – but some are up
to 12,000 years old, and still leaking gas. Therein lies the
uncertainty: are the methane explosions observed today part of a
process that occurs more or less constantly through Earth history –
or do they represent the start of a sudden release, ramping up to
runaway global warming? The scientific jury is at odds.
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| Methane hydrate, a frozen form of methane gas, at one of the many cold seeps off the U.S. Atlantic coast. Hydrate is widespread in the deep ocean and sequesters as much as 20% of all carbon on Earth. NOAA Office of Ocean Exploration and Research |
Pennsylvania
State climate scientist Prof Michael Mann, for instance,
characterises the methane bomb idea as “catastrophism” and claims
it is being exploited by the climate denial lobby to discredit
climate theory generally. He says the amount of methane released will
be
“small compared to human emissions” of carbon. Other scientists, like Gavin Schmidt of the NASA Goddard Institute,
argue that it is highly unlikely that a large volume of seabed
methane would be released suddenly, i.e. over a period less than
thousands of years, because it did not do so in past warming events.
Instead it will continue to trickle out.
Oceanography and
ice expert Prof Peter Wadhams disagrees. He says loss of Arctic sea
ice from the shallow continental margins could trigger such a release
which “could happen very suddenly and … is the greatest single
threat that we face”. He says that mainstream science, represented
by the Intergovernmental Panel on Climate Change (IPCC),
does not
generally recognise the threat.
Australian
National University earth scientist Prof. Andrew Glikson cites the
Global Carbon project finding that there are 1.4 trillion tonnes of
accumulated methane stored on land and 16 trillion tonnes in the
ocean, available for release if the planet grew warm enough, and this
‘could have catastrophic effects on the biosphere’. He points
out there is already clear evidence for the explosive release of
methane, on land and at sea. With Arctic temperatures already 3-8
degrees warmer due to global warming, the risks of a sudden methane
release
“have not yet been fully accounted for in climate projections.”
At temperatures
above +4 degrees, many scientists now consider the risk is increasing
of the planet becoming partly or wholly uninhabitable to humans and
large animals. Certainly, such heat and climate instability
would
destroy most of our current food production systems, spilling
billions of climate refugees across the planet and causing wars to
break out between and within nation states.
How many would
die in such an event is not knowable, because we cannot predict how
humans will respond, how many wars we will start, or how many nukes
we will unleash in the ensuing chaos. Potsdam Institute climatologist
John Schellnhuber has said: “At 4 C Earth’s... carrying capacity
estimates are below 1 billion people.” Prof Kevin Anderson of the
U.K.’s Tyndall Centre for Climate Change concurs: “Only about 10
per cent of the planet’s population would survive at 4 C.”
Several scientists have voiced the view that the human population
will be reduced
from 9-10 billion to around 1-3 billion in the long
run.
We already know
that our physical survival is in jeopardy in extended periods above
35 degrees Celsius – that is, where daytime temperatures constantly
reach 40-50 degrees C or more. Such temperatures will occur
frequently with +7 degrees of global warming and will render large
parts of the earth uninhabitable – including the most heavily
populated. Above +12 degrees of global warming,
human survival
becomes physically impossible. However long before our heat tolerance limits are reached, local and
global food and water supplies will collapse, prompting mass
migration and war. Without urgent worldwide action, the global
economy – and with it civilized society – are predicted to go
down as we approach +4 degrees. Such warnings come, not from ‘radical
greens’, but from authorities no less conservative than
Bank of
England governor Marc Carney,
who states that the global financial system is currently investing in
catastrophe by
backing new fossil fuel projects. These numbers represent the current most-informed estimates of the
impact of the unfolding climate crisis, should world efforts to halt
it fail and should the climate deniers triumph.
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| Methane bubbles out of the seafloor off the coast of Virginia, north of Washington Canyon. NOAA Office of Ocean Exploration and Research |
The risk for
humanity posed by the ‘methane gun’ is that rapid global
mass-release may be ‘locked and loaded’ and firing
before we
have sufficient scientific data to confirm it. It is, as they say, an
event of low probability – but very high impact. Is it a risk that
a rational person would take?
Once the gun has
begun to fire, there is practically nothing humans can do to stop it.
It will unleash other dangerous feedbacks, potentially leading to
runaway warming. It will shift the planet from its present warming
state to a
‘hothouse Earth’ state where human survival comes into question.
The only viable
strategy – possibly – is preventative: to move civilization far
faster towards total elimination of all fossil fuels and land
clearing worldwide – and plant billions of trees as quickly as
possible, to slow the global warming trend before it triggers the
methane gun.
This means that
countries like America, Australia, Brazil and Russia must cease their
dangerous do-nothing policies, and stop mining coal, oil and gas, and
clearing land. Countries like India and China need to cease building
coal-fired power stations immediately. And every country needs to
scale back carbon emissions on an accelerated time-scale from
transport, agriculture, concrete and industry.
While some
scientists urge geoengineering solutions, such as the artificial
release of sulphate aerosol particles to erect a giant sunshade over
the Earth, this represents a counsel of despair. It means allowing
the atmosphere to attain virtual temperatures that would cook humans,
then trying to chill them down with a planet-sized ‘air-conditioner’.
The consequences, should our air conditioner fail, would be terminal.
That really only leaves us with the option of trying to contain
global warming by eliminating human carbon emissions – before the
methane gun fires.
In the end, the
worst that can happen by banning fossil fuels and regreening the
planet is that we get a new clean energy system, cheaper energy,
renewed economic growth and a more sustainable Earth.
If the climate
deniers – fifty huge energy corporates and their political and
media cheer squad – get their way, the worst that can happen is
human extinction.
Which risk do you
prefer?
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