Re-adjusting our relationship with the planet
An alarming new study* shows that cutting greenhouse gases is not
enough: there are risks of a 'Hothouse
Earth' even if CO2 emissions are slashed.
Says
co-author Katherine Richardson from the University of Copenhagen: “So not only are we going to have to
stop burning fossil fuels by the middle of this century, we are going to
have to get very busy with
planting trees, protecting forests, working out how to block the Sun's rays and
developing machines to suck carbon out of the air.
The
authors conclude that a total
re-orientation of human values, equity, behaviour and technologies is required. We must
all become stewards of the Earth.
This
was also Naomi Klein’s understanding, in her ground-breaking book about the
Climate Change data: This Changes
Everything – a book that is a beacon for any one of us willing to live on a
beautiful and safe planet, and protect us humans as well for times to
come.
Global map of potential tipping cascades. The
individual tipping elements are color-coded according to estimatd thresholds in
global average surface temperature (tipping points; 18,43). Arrows show the
potential interactions among the tipping elements, based on expert elicitation,
which could generate cascades. Note that although the risk for tipping (loss
of) the East Antarctic Ice Sheet is proposed at >5 degrees Celsius, some
marine-based sectors in East Antarctica may be vulnerable at lower
temperatures.
Climate change:
'Hothouse Earth' risks even if CO2 emissions slashed
Researchers
believe we could soon cross a threshold leading to boiling hot temperatures and
towering seas in the centuries to come. Even if countries succeed in meeting
their CO2 targets, we could still lurch on to this "irreversible pathway."
Their study shows (see ref. * below) it could happen if
global temperatures rise by 2C.
An
international team of climate researchers, writing in the journal Proceedings of the National Academy of
Sciences (USA), says the warming expected in the next few decades could
turn some of the Earth's natural forces - that currently protect us - into our
enemies.
Each year the Earth's forests, oceans
and land soak up about 4.5 billion tonnes of carbon that would otherwise end up
in our atmosphere adding to temperatures. But as the world experiences warming,
these carbon sinks could become sources of carbon and make the problems of
climate change significantly worse.
So
whether it is the permafrost in northern latitudes that now holds millions of
tonnes of warming gases, or the Amazon rainforest, the fear is that the closer
we get to 2 degrees of warming above pre-industrial levels, the greater the
chances that these natural allies will spew out more carbon than they currently
now take in.
Back
in 2015, governments of the world committed themselves to keeping temperature
rises well below 2 degrees, and to strive to keep them under 1.5. According to
the authors, the current plans to cut carbon may not be enough if their
analysis is correct.
"What
we are saying is that when we reach 2 degrees of warming, we may be at a point
where we hand over the control mechanism to Planet Earth herself," co-author
Prof Johan Rockström, from the Stockholm Resilience Centre, told BBC News.
"We are the ones in control right
now, but once we go past 2 degrees, we see that the Earth system tips over from
being a friend to a foe. We totally hand over our fate to an Earth system that
starts rolling out of equilibrium."
Currently,
global temperatures have risen about 1 degree above pre-industrial levels and
they are rising by around 0.17C per decade.
In
their new study the authors looked at 10 natural systems, which they term
"feedback processes". Right now, these help humanity to avoid the
worst impacts of carbon and temperature rises, and include forests,
Arctic sea-ice, and methane hydrates on the ocean floor.
The
worry is that if one of these systems tips over and starts pushing large
amounts of CO2 into the atmosphere, the rest could follow like a row of
dominoes.
What exactly is a Hothouse Earth scenario?
In
short, it's not good. According to the research paper, crossing into a Hothouse
Earth period would see a higher global temperature than at any time in the past
1.2 million years.
The
climate might stabilise with 4-5 degrees C of warming above the pre-industrial
age. Thanks to the melting of ice sheets, the seas could be 10-60 metres higher
than now. Essentially, this would mean that some parts of the Earth would
become uninhabitable. The impacts would be "massive, sometimes abrupt and
undoubtedly disruptive," say the authors.
The
only upside, if you can call it that, is that the worst impacts may not be felt
for a century or two. The downside is that we wouldn't really be able to do
anything about it, once it starts.
Are the current heatwaves in the UK and Europe evidence of a Hothouse Earth?
The
authors say the extreme weather events we are seeing right now around the world
cannot be immediately associated with the risk of passing 2 degrees C.
However,
they argue that it may be evidence that the Earth is more sensitive to warming
than previously thought.
"One
should learn from these extreme events and take these as a piece of evidence
that we should be even more cautious," said Prof Rockström.
"It
may support the conclusion that if this can happen at one degree, then we
should at least not be surprised or too dismissive of conclusions that things
can happen more abruptly than we previously thought."
Surely we've known about these risks before?
What
these authors are saying is that up to now, we've underestimated the power and
sensitivity of natural systems.
People
have been thinking that climate change would be a global emergency for everyone
if temperatures rose 3-4 degrees by the end of this century.
But this paper argues that beyond 2
degrees, there is a significant risk of turning natural systems - that
presently help keep temperatures down - into massive sources of carbon that
would put us on an "irreversible pathway" to a world that is 4-5
degrees warmer than before the industrial revolution.
Any good news here at all?
Surprisingly,
yes!
We can avoid the hothouse scenario but
it's going to take a fundamental re-adjustment of our relationship with the
planet.
"Climate
and other global changes show us that we humans are impacting the Earth system
at the global level. This means that we as a global community can also manage
our relationship with the system to influence future planetary conditions.
"This
study identifies some of the levers that can be used to do so," says co-author Katherine Richardson from the
University of Copenhagen.
So
not only are we going to
have to stop burning fossil fuels by the middle of this century, we are
going to have to get very busy
with planting trees, protecting forests, working out how to block the Sun's
rays and developing machines to suck carbon out of the air.
Carbon Engineering: Removing
carbon dioxide from the atmosphere, as in this model, will be necessary, say
the authors
The
authors say
a total re-orientation of human
values, equity, behaviour and technologies is required. We must
all become stewards of the Earth.
What do other scientists say?
Some
say the authors of this paper are too extreme. Many others say their
conclusions are sound.
"As
a result of human impacts on climate, the new paper argues that we've gone
beyond any chance of the Earth cooling 'of its own accord'," said Dr Phil
Williamson from the University of East Anglia, UK.
"Together
these effects could add an extra half a degree Celsius by the end of the
century to the warming that we are directly responsible for ‒ thereby crossing
thresholds and tipping points that seem likely to occur around 2 degrees C, and
committing the planet to irreversible further change, as Hothouse Earth."
Others
are concerned that the authors' faith in humanity to grasp the serious nature
of the problem is misplaced.
"Given
the evidence of human history, this would seem a naive hope," said Prof
Chris Rapley, from University College London.
"At
a time of the widespread rise of right-wing populism, with its associated
rejection of the messages of those perceived as 'cosmopolitan elites' and
specific denial of climate change as an issue, the likelihood that the
combination of factors necessary to allow humanity to navigate the planet to an
acceptable 'intermediate state' must surely be close to zero."
http://www.stockholmresilience.org/research/research-news/2018-08-06-planet-at-risk-of-heading-towards-hothouse-earth-state.html
Steffen, W., Rockström, J., Richardson, K., et al.
(2018) Trajectories of the Earth System in the Anthropocene. Proceedings of
the National Academy of Sciences (USA), DOI: 10.1073/pnas.1810141115
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