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Give me that!

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This really isn't about polar bears any more.

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At this very moment, the fate of
civilization itself hangs in the balance.

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The way we have been calculating the future
impacts of climate change up to now

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has been missing
a really important piece of the picture.

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We are now dangerously close to the
tipping point in the world's climate system

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this is the point of no return

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after which truly catastrophic changes
become inevitable.

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Think of it like this:

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For the past three million years,

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our planet's climate has always been in one
or the other of two stable states,

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small changes in solar incidence
pushed us from one to the other.

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When we are in this cooler dip,
the planet has an ice age.

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When we are in the warmer one, the planet's
climate is very much as it is now,

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and has been throughout
the whole of human history.

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The problem is that
our use of fossil fuels

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is pushing us further and further out
of our little stable dip

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and up the far slope of this hill.

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The tipping point is the point at which
we cross the peak of the hill,

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and we no longer need
to keep pushing

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to keep the planet moving
towards a much hotter place.

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It will just keep rolling onwards,
all on its own.

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This tipping point exists because of a set
of positive feedbacks in the climate systems

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mechanisms that can amplify the effects of
man-made warming and lead to runaway change.

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One of them is the Albedo Effect.

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White surfaces reflect more solar radiation
than dark surfaces,

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so as global warming from greenhouse gases
melts ice and snow,

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it leaves behind
dark ocean or land.

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these surfaces now absorb more solar radiation
than before - so adding to warming

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which melts more ice and snow,
and so on.

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Uncondensed water vapour is actually a more
important greenhouse gas than CO2.

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Although we aren't actually emitting
much water vapour directly,

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as the planet warms,
evaporation rates increase,

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raising humidity and thickening
the Earth's thermal blanket

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which in turn raises temperatures, which
further increases evaporation rates,and so on.

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Normally, about half the CO2 emitted
each year from human activities

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is re-absorbed by a combination of forests,
plankton, and the ocean itself.

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But the ocean surface is
becoming more and more acidic

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as concentrations of
CO2 dissolved in it rise.

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At the same time the water temperature
at the surface is also going up,

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forming a layer of warm, acidic water
that is spreading across the ocean surface,

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killing off the plankton
that locks CO2 out of the atmosphere.

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Worse, warm water
holds less CO2 than cold water

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so as it heats up, it starts releasing
some of the CO2 it had previously absorbed.

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Just like marine ecosystems, land-based
ecosystems normally act as carbon sinks,

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taking carbon from the atmosphere
and using it for growth.

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But as these eco-systems heat up,
they become unbalanced

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plants become less and less effective

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while micro-organisms in the soil become
more and more effective at putting it out,

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causing the ecosystem as a whole to go from
being a carbon sink to being a carbon source.

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As temperatures rise and rains fail,
forests dry out, and fires don't get put out.

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All of the forest's stored carbon
goes up in smoke,

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adding to the greenhouse gases in the
atmosphere, further increasing warming,

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which further degrades
the carbon sinks.

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In Siberia, a vast area of frozen peat bog
the size of France and Germany combined

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that we call the permafrost is melting,

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and as it melts, it releases
huge quantities of methane.

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Methane is a greenhouse gas with
a short lifespan in the atmosphere

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but while there it has a warming effect more
than 20 times as powerful as carbon dioxide.

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The more methane is released,
the more it adds to warming,

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the more the permafrost melts,
and the more methane is released.

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The arctic tundra is not the only place
with large stores of frozen methane.

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Lurking under the sea bed there may be
as much as 10 trillion tons of methane

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stored as frozen crystals
at sites around the world.

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If we raise ocean temperatures by enough
- and nobody knows how much is enough,

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we could trigger the sudden release
of this stored methane into the atmosphere.

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The last time this happened, global
temperatures rose abruptly by 10 degrees.

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So, these are some of the
feedback mechanisms

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that explain why our global
climate system has a tipping point.

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Each feedback in the system
has its own internal tipping point,

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and it is the relationships within this
complex, mutually reinforcing system,

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that have been missing
from our climate prediction models.

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So far we have only pushed up
global temperatures by around 0.8°C

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but because of the 40 or 50 year time lag
between emissions and temperature rise,

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the emissions already
in the atmosphere

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commit us to raising temperatures by around
another 0.6°C over the coming decades.

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which could easily be enough to place us
right at the peak of the hill

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or even over it.

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If we do pass this critical threshold, global
temperatures could soar by as much as 6°C.

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If this happens, the natural world will
suffer a mass extinction event

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which will wipe out the majority of the plants
and animals with which we share the planet.

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although there will be a lot more rats,
flies, cockroaches and mosquitoes

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as the world's ecosystems
go into meltdown.

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The first human impacts will come in the form
of steeply declining access to fresh water,

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as rainfall patterns change,
glacier-fed rivers dry up,

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and rising sea levels
contaminate reservoirs.

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As crops fail, forests burn, deserts spread
and coastal regions flood permanently,

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people will start to pack up
their things in their billions

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and move on in search of
a better life elsewhere.

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But where?

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Humanity might
survive this.

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But what will 'humanity' mean in a world
where countries which will remain habitable

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like Britain, spend most of our resources
fighting to keep out the starving millions

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who can no longer live in their own countries
because of what we have done?

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The world is awash with weapons.

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Enough firearms to arm one in every seven
human beings on the planet.

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As the world's ability to support the huge
numbers of people alive today dwindles,

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we will not die
peacefully in our sleep.

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OK,
here's the good news:

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None of this
is inevitable – yet.

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This is not the time to panic
or to despair.

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This is the time to act,
while we still can.

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We need to recognize that
there is a huge question mark

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over whether governments and
corporations are capable of responding

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to this threat
in the time we have left.

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They have had 20 years already and
still have less than nothing to show for it.

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This is because they remain
committed to a doctrine that prioritises

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short term profits and endless economic
growth over the survival of life on earth.

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There is no great mystery
about what we need to do

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to reduce emissions
in line with the science.

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we simply need
to consume less.

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But that is out of
the question in a society

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which is founded on the ever-increasing
consumption of material resources and energy.

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Nobody has all
of the answers

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but we do know that this
is not the only way to live,

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and given that it is almost
certainly going to kill us all,

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we'd better start looking urgently
at some of the alternatives.

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It's now very clear that in order to actually
win the fight against climate change,

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making big changes to the way we each live
our own lives is not going to be enough.

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we're also going to have to actively
confront powerful vested interests

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who will stop at nothing to prevent
the changes we need from taking place.

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We have to be more
than just consumers.

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These are extraordinary times.

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Preventing runaway global warming is the
most important task in all of human history.

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and it has fallen to us
to do it.

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If we don't, then everything else
we work to achieve in our lives

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will be destroyed,
or become meaningless.

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Those who came before us
didn't know about this problem,

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and those who come after
will be powerless to do anything about it.

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But for us,
there's still time!

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We'd better get
a move on though.

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