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(Dr Pep Canadell) Climate change it is like a
global problem in the sense that the atmosphere is a commons for society.
What we Australians do
or somebody else does at the other end of the world,
it actually all gets mixed within a year.
So we really need to develop strategies,
which are strategies working globally in partnership.
Both in the science to understand it,
but also in the way we address the mitigation ultimately.
(Dr John Church )Well the Earth is warming,
principally, because we're releasing
greenhouse gases into the atmosphere.
These trap the outgoing long wave radiation
and lead to a warming Earth.
The energy, total energy
in the Earth's system increases
and much of that energy is locked up in the oceans.
(Dr Steve Rintoul) I'm an oceanographer and the oceans are
important to climate because they store
huge amounts of heat and carbon dioxide.
And in fact about 93 per cent
of the extra heat that's been stored by the Earth over the last 50-years,
is found in the ocean.
So I we want to understand climate change and track how it's evolving
we really need to be measuring the ocean.
And that's relevant to current discussions about
the rate at which the Earth has warmed recently.
So, over the last decade or so the
speed at which the surface has been warming
has slowed a bit, it's still warming,
and the last decade is still the warmest decade in
the instrumental record.
But the rate of warming has slowed, even though
the amount of CO2 in the atmosphere has increased,
so that sounds like a surprise at first,
but we're beginning to understand exactly how that's happening.
(Dr John Church) We also see other changes;
Glaciers are continuing to lose mass.
The sea ice, particularly in the Arctic,
is continuing to retreat
and the ice sheets of Greenland and Antarctica
are contributing by losing mass contributing to sea level rise
which is continuing to rise
at a faster rate over the last 20 years
than over the 20th century as a whole.
(Dr Steve Rintoul) These pauses or periods
when the Earth warms more slowly than average
are not unusual. They happen in the climate system frequently.
The second point is that we now understand what's happening
and part of what's happening is that the
heat in the Earth's system is moving around and, in particular,
more of the heat that used to be near the surface of the ocean has moved
deeper in the ocean so if we look at the...
how the heat that's stored by the Earth
has changed over the last decade
and include the upper 2000 metres of the ocean
we see that the earth has continued to warm during this last decade
just like it has in the decades before.
The other factor that contributes is that the sun that goes through a cycle
of about a decade of energy output from the sun increasing
and then decreasing has been in a decreasing
phase over the last ten years
and that's now turning around.
And finally there have been a few small volcanoes and volcanoes put
small particles up into the atmosphere
and that tends to shield the Earth from some of the sun's energy
and that also causes the Earth to cool.
So the combination of those factors can explain
why the surface of the Earth
both on land and in the ocean has
warmed less rapidly over the last decade
than it did in the decade before.
(Dr Pep Canadell) So greenhouse gases are
gases which are naturally occurring in the atmosphere.
They trap some of the energy from the sun
and allows the Earth to be a very comfortable place
as a whole to live in,
so a lot of the human activities specifically
the combustion of fossil fuels,
coal, gas and oils
and also what we call land use change deforestation,
largely the burning of the forest,
are the main causes of greenhouse gases.
So we have now acceleration in the accumulation
of these greenhouse gases and that's why there is a warming
and warming actually leads to other changes in climate patterns
including precipitation and others.
(Dr John Church) To pedict future changes
just extrapolating the past is not sufficient.
What we have to do is build an understanding
of what's happened in the past,
put this understanding in climate models
which could then simulate the past,
test them against the past
and then use those climate models
with scenarios of how our society might behave in the future
in terms of emitting greenhouse gases
and run those models into the future
to predict future conditions.
(Dr Steve Rintoul) So to study the ocean
to actually measure how the ocean's changing
we use a variety of tools.
We use ships that we lower instruments from,
ships that scan the ocean, use satellites,
use instruments that we anchor to the sea floor for a year or two
and we use these days simple robots,
floats that drift through the ocean currents at a depth of 1 kilometre.
Every ten days they drop drown to 2 kilometres
and then rise up to the surface measuring temperature and salinity.
We transfer that data by satellite,
sink back down and do it all again and do that for five years or so
for each float.
There are about 3600 of these floats now
drifting around the world oceans and so in a real sense
we're measuring the oceans for the first time.
(Dr Pep Canadell) We put a huge amount of effort in
taking all these measurements
and expensive measurements and expensive development
of modelling capability
but also we're putting an increasing amount of time in
packaging this information in ways that can be readily used
and understood and make a difference
for the things that policy needs information on.
(Dr Steve Rintoul) The last decade has been the warmest
in the instrumental record
and each of the last few decades has been warmer than the last
and that's part of the signal of greenhouse warming.
The last 12 months for Australia has been the warmest on record
and that is the combination of the slow
continued warming due to greenhouse warming
and the variability of the climate system
and so we will get years that will be cooler than this last one
but that's what we expect to see. The climate...
the warming of the Earth and the warming over Australia
will not just be a steady trend, it'll go up and down a little bit.
But the trend over longer time periods which is what you need to look at
in order to detect a signal of climate change
has been up and will continue to be warming in the future.
(Dr John Church) Sea levels are continuing to rise.
The amount of rise depends on
future emissions of greenhouse gases.
Larger emissions lead to larger rises
both during the 21st century and beyond
so the amount of sea level rise
that Australia will have to deal with
is impacted by the
degree to which we mitigate ours and the world's
emissions of greenhouse gases.
We cannot stop all sea level rise.
We will have to adapt
but the amount of adaptation that we have to do
will depend on our future emissions.
(Dr Steve Rintoul) So the challenge for climate science in the future,
it's clear that the Earth is warming
and it's clear that human activities have contributed.
What is still more difficult to do
is to project regional changes of temperature
and, in particular, precipitation
and that's crucial because the decisions that
society will make to adapt to the climate change that we don't avoid
requires information at those scales,
at local and regional scales because that's where people make decisions.
And so a challenge for the climate science
is to deliver that sort of information, regional projections
of changes in climate
that can inform decision-makers
about both how hard we're going to work
to slow down the rate of climate change by mitigating,
by reducing greenhouse gas emissions
and how we can most effectively adapt
to the climate change that we're not going to avoid.
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