Understanding why our Earth system is warming


[Music plays] [Music plays] (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. [Music plays]

Comments 17

  • Careful speaking like that may get your funding cut. Luck you don't have many views.

  • Great video. Thanks CSIRO for keeping us in the know.

  • Excellent video guys. We will be linking to it.

  • Great Video! Keep it up!

  • Excellent work guys.

  • So are we cooling or warming? I wish we'd make up our minds. This is also just one of the reasons why I scoff at the mention of 'peer-review'

  • The latest IPCC Fifth Assessment Report (WGI AR5) presents finding that our Earth system is warming. A summary of results can be found online at climatechange2013 (dot) org

  • CSIRO
    do you have any existing distributors of your product in the united states?
    In California?

  • BS not supported by facts just politics!

  • No mention of the contribution to changes in surface temperatures made by the rotation between El Niño, La Niña, and neutral periods). This shift is the greatest cause of temporary temperature increases and decreases, which don't affect the long term global temperature rise created by CO2 emissions. It probably has a lot to do with the increased uptake of heat in the lower ocean levels, and a strong El Niño, as in 1998, should create a rise in temperatures above those of the last decade.

  • The science is overwhelming that humans have caused global warming and the climate chaos it will increasingly create. The climate scientists who actively research and publish results in peer-reviewed journals have grown ever more confident of this conclusion (97-8% of them) as research confirms earlier work. And action is urgently needed to prevent rising temperatures from transforming our world into one far less friendly to its inhabitants.

  • Great lesson .

  • Earth is eventually going to become another Venus…

  • Understanding why our Earth system is warming
    ***

  • Climate change explained.

  • A warmer earth will allow us to grown food in areas that  can't currently farm .  This planet was changing before man was here and will  continue to be here long after the human species is gone. What exactly is your goal and who are you to determine what the proper temp for this planet is? Like you said we will be unable to avoid climate change so start spending money on adapting rather than controlling the population.

  • 10beekeeper, The world is involved in coming up with renewable energy to lower the greenhouse effect. The analysis is necessary and so far mixed energy is helping. Research and see that there are literally countries the use 100 percent renewable energy (German). Food sustainability is extremely important as well.

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