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Climate Change Science
Update
Building Farmer & Advisor Knowlege in Carbon Farming
Written for the Carbon Farming Knowledge Project by
Mike Roberts Communications, Research and Consulting
According to Darren Ray, Senior
Meteorologist and Climatologist with the
South Australian Regional Climate Services
Centre of the Bureau of Meteorology,
climate change is happening, human
influence is undeniable and there is
still a window of opportunity to make a
difference we can live with.
Darren gave a presentation at the first Adviser
Workshop of the Carbon Farming Knowledge
Project. This is a project supported by funding from the Australian Government whose aims are
increasing knowledge and understanding of reducing green house gas emissions, carbon in
farming systems and participation in the Carbon Farming Initiative.
It was appropriate to begin with the iconic graph showing CO2 measurements in atmosphere taken
at Mauna Loa Observatory in Hawaii since the 1950s. There is a strong annual cycle of CO2 that
reflects the strong uptake by vegetation in the atmosphere in the Northern spring. This is more
noticeable in the Northern Hemisphere because of a greater land mass. There is a corresponding
increase in annual levels as CO2 is released in the northern winter through vegetation die off. The
graph also notes a steadily increasing trend of CO2 in the atmosphere, which has increased in rate
over last few decades.
Atmospheric measuring stations set up around the world show the same rises with very clear
upward trends. This year we hit 400 ppm of CO2 in the atmosphere for the first time in 3 million
years.
Scientists know that the CO2 is coming from human activity because they can break down the
isotopes in the gases and work out where they come from. This shows the source of the CO2 is a
combination of fossil fuels being burned and from deforestation.
The three main gases contributed to directly by human activity include carbon dioxide, methane
and nitrous oxide. All three have spiked in the last couple of hundred years along with the spike in
human population.
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from the Australian Government
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Climate Change Science Update
The basic greenhouse gas principle has been well understood since the 1850s. Greenhouse
gases have a particular shape that allows them to interact with infrared energy in the atmosphere.
As the sun shines on the atmosphere, much of its energy would be reflected out into space. As
greenhouse gases increase it prevents some of that energy from escaping and traps heat within.
Water vapour is another major greenhouse gas but human activity doesn’t directly influence its
level. However, as the planet warms due to the influence of increases in the other gases produced
by our activity, then water vapour also increases more rapidly in the atmosphere. This is a form of
positive feedback.
Using satellites, scientists measure changes in the amount of heat and infrared energy going into
space over time. These measurements show less infrared going out into space and more infrared
energy coming back to the surface. Darren made the point that, “two different data sets are giving
us the same answer about this. That cuts through all the debate about whether or not this is actually
happening.”
The amount of extra heat is only about 2 watts per square metre. “If you add it up that equals the
energy from about four atom bombs per second going into the earth’s atmosphere compared to
50-100 years ago. The influence of greenhouse gases depend on their warming potential and the
amount in the atmosphere. Twenty percent of the CO2 we put out now will still be there in 1000
years. It is that long-term effect which is the problem. Methane is more potent as a greenhouse gas
but it doesn’t persist as long.
A huge amount of CO2 is stored in the oceans and in soil. Skeptics will say that humans only put
out a small amount of the total CO2. The problem is that we are influencing a system previously in
a state of approximate equilibrium. “Increasing the greenhouse gases is like slowly turning up the
tap into a full bath of water until it overflows.”
Going back 400,000 years shows a close correlation between temperature and CO2 levels. There
have always been cycles because of the earth’s orbit and the melting and freezing of icecaps. When
greenhouse gas levels increase very rapidly, as they are doing now, the trigger for the temperature
increase is not astronomical cycles.
We are not expecting another ice age
for thousands of years. The trigger is
human induced greenhouse gas. Ice
core samples are used to verify this with
other overlapping instrument records.
The Global Financial Crisis slightly
reduced the output of greenhouse
gases. There are also some signs that
rates of increases are reducing due to
abatement efforts. In South Australia
about half of our greenhouse gas
emissions occur through electricity
Forestry and land use change can be sink or sources
depending on the land clearing and land use practices
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from the Australian Government
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Climate Change Science Update
generation. Other sources are shown in the graph.
Global temperatures are measured by various international centres. 2010 is the warmest year on
record. There are other influences on the climate but greenhouse gases are starting to dominate.
The oceans have warmed, accounting for more than 90% of the extra energy stored by the earth’s
system since 1971. More La Nina events since 2000 are pushing more of the heat from the surface
into the ocean depths. This has slowed slightly the rises in surface air temperatures since 2000
compared to the 1980’s and 1990’s.
Some farmers find it difficult to reconcile this recent reduction in temperature rise with the warnings
about climate change. Farmers are used to cycles like El Nino but because of volcanic events and
relatively quiet solar activity things haven’t warmed as strongly as they did during 80s and 90s. But
the only thing that explains the long-term trend is the greenhouse gas increase. There is a lag of
30-100 years between the CO2 level increase and the warming it produces. The changes we see
now are a reflection of 70s and 80s CO2 emissions. It will be beyond 2100 before we see the full
effect of what we are emitting now.
“Multiple lines of robust and compelling evidence support the conclusion that many aspects of the
climate system have changed. We have already altered the planet.”
• Warming is unequivocal. Many observed changes are unprecedented on timescales of
decades to millennia.
• It is extremely likely that human influence has been the dominant cause of the observed
warming since the mid-20th century.
• The human influence on climate is already clear.
• Climate will continue to change long into the future.
• Limiting future climate change will require substantial and sustained reductions in emissions.
2013 was the warmest year on record for Australia. There was strong warming and increased
maximum temperatures, particularly in spring. There was some cooling in the north because of
increased cloud from aerosol influences
originating in Asia.
As the planet warms, the tropics are
expanding towards the poles pushing
rain bearing weather systems away
from South Australia at about ½ degree
latitude per decade. This is causing an
April to June drying in Southern Australia.
In South Australia and Victoria we live
with a lot of drier country to the north
of us. Stronger high-pressure systems
over SA prevent us getting cold fronts
bringing winter rain. We are seeing earlier
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Climate Change Science Update
flowering of crops and more frosts. We live on a narrowing wet fringe on the bottom of the continent.
Expect to see stronger El Nino and La Nina events. We will see a drying trend from weaker cold
frontal systems but experience more variability such as flooding during La Nina events.
The 10 years up until 2010 saw dramatically reduced inflows to the Lower Murray Darling Basin.
There was a 44% decline from a 14% rainfall decrease.
This is a function of both reduced rainfall, and the timing of the rainfall decline.
The loss of autumn rainfall has been significant in the lower Basin, since it ‘primes’ the catchment
for runoff during the remaining wet season.
Agricultural/ Ecological impacts of climate change:
• Plant fertilisation by increased CO2 gets offset by hotter and drier conditions, decreases
protein in wheat.
• Increased temperatures decrease fruit chilling and impact on grape varieties.
• Increases in weed species
• Eucalypt species like narrow temperature regimes not extremes
• Mis-matches are starting to occur between co-dependent species under temperature rises
and seasonal shifts
• Increasing eutrophication of streams, rivers and lakes with rainfall declines and warmer
temperatures. This results in waters becoming rich in mineral and organic nutrients that
promote a proliferation of plant life, especially algae.
New scenarios: Representative Concentration Pathways
RCP2.6
Peak and decline
RCP4.5
Stabilization after 2100
RCP6.0
Stabilization after 2100
RCP8.5
Rising
RCPs encompass a wide range
of plausible futures. The warming
effect from greenhouse gases is
now at 2.3 Watts/metre squared.
RCP2.6 means a scenario where it
reaches 2.6 Watts/metre squared.
This requires much reduced
emissions. RCP8.5 is a scenario
where much of the fossil fuels
available are burnt and warming
reaches 8.5Watts/metre squared.
This is the scenario we are currently
following. The point of this is that we
have a lot of choice about whether
we allow a temperature rise to go
beyond 2oC!
From IPCC AR5 report
We can adapt to a 2oC temperature rise but adapting to 4oC rise would be difficult.
“If we keep going the way we are we will end up with a world that farmers will struggle to adapt to.”
So the name of the game is keeping total warming below 2oC. The earth has warmed by 0.9oC
already. A 2oC target limits ‘positive feedbacks’ like Greenland ice sheet melt, Arctic ice melt,
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permafrost melt releasing carbon, warming
of soils releasing carbon and increasing
water vapour. There is international
agreement to keep below 2oC including
from Australia, China and the US.
Temperature changes at the end of the 21st C are dependent
on scenario
Low emissions choice
Burn all fossil fuels choice
Although there are multiple lines of evidence
showing that global warming continues and
human activities are mainly responsible,
the gap between public perception and the
science is staggering and is a real concern.
In closing, Darren Ray made the following
points:
• Human activity is already impacting
the planet and Australia
• Farming management and practices
can be big contributors either as
emissions or sinks
• Minimising future climate change is a
really good idea
• To do this, optimising sinks of carbon
will be an important part of the picture
Which future do we want?
From IPCC AR5 report
3 to 5 degrees C
warming for
Australia
The contrast between wet and dry regions and wet and dry
seasons will increase
Low emissions choice
Burn all fossil fuels choice
For more information contact Darren Ray:
[email protected]
Which future do we want?
From IPCC AR5 report
Strong rainfall declines and
decreased water availability
in southern Australia
From repeated studies of scientific papers, 97% of scientists working with
climate change agree that climate change is real and serious.
This is a project supported by funding
from the Australian Government
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