Chapter 2
Future climate for Australia's key agricultural production zones
Introduction
2.1
This chapter discusses one aspect of the inquiry's first term of
reference: the scientific evidence available on the likely future climate of Australia's
key agricultural production zones. The committee was referred to two main
reports in relation to this term of reference: the Intergovernmental Panel on
Climate Change's (IPCC) Fourth Assessment Report[1]
and the joint Commonwealth Scientific and Industrial Research Organisation
(CSIRO) – Bureau of Meteorology (BoM) Climate Change in Australia report.[2]
2.2
This chapter begins with a brief overview of some factors influencing climate
projections. The chapter then goes on to discuss the predictions made in the
IPCC Fourth Assessment Report and the CSIRO-BoM Climate Change in Australia report
(Climate Change in Australia) of the likely future climate of Australia's
key agricultural production zones. The chapter also discusses the need for
further work to downscale climate projections and better communicate
projections to those in the agricultural sector.
2.3
The implications of likely future climate on current farm enterprises
and possible future industries will be considered in the final report.
Climate projections
2.4
The complexity of the climate system means that forecasting likely
future climate is not simply a matter of extrapolating from past trends. Instead,
climate models, which are mathematical representations of the Earth's climate
system, are used to forecast weather and climate.[3]
2.5
However, as Climate Change in Australia notes projections of
global and regional climate change contain a large number of uncertainties.[4]
2.6
The IPCC Fourth Assessment Report states that 'significant factors'
contribute to uncertainty in projected climate change for the Australia-New
Zealand region. This uncertainty reduces confidence in projections:
The El Niño-Southern Oscillation significantly influences rainfall, drought and tropical cyclone behaviour in
the region and it is uncertain how [the El Niño-Southern Oscillation] will
change in the future. Monsoon rainfall simulations and projections vary
substantially from model to model, thus we have little confidence in model
precipitation projections for northern Australia. More broadly, across the
continent summer rainfall projections vary substantially from model to model,
reducing confidence in their reliability. In addition, no detailed assessment
of [model performance] over Australia or New Zealand is available, which
hinders efforts to establish the reliability of projections from these models.[5]
2.7
Human activities also impact on climate through increasing the
concentrations of greenhouse gases, such as carbon dioxide and methane, in the
Earth's atmosphere. One of the key difficulties in making long-term climate
projections, and consequently assessing future climate change, is determining
future greenhouse gas emissions due to human activities. This is explained in Climate
Change in Australia:
near-term changes in climate are strongly affected by inertia in
the climate system due to past greenhouse gas emissions, whereas climate
changes later in the century are more dependent on the particular pattern of
greenhouse gas emissions that occur through the century.[6]
2.8
In order to overcome this problem the IPCC has developed a range of
emissions scenarios.[7]
The IPCC describes these scenarios as 'images of the future, or alternative
futures', and emphasises that the scenarios are not predictions or forecasts.[8]
Importantly, the scenarios do not include additional climate policies for
reducing or mitigating greenhouse gas emissions above current policies.[9]
Further, the IPCC does not assign any probability that a particular scenario
will occur.[10]
2.9
The scenarios are grouped into four 'storylines':[11]
- The A1 storyline describes a world of very rapid economic growth,
a global population that peaks in mid-century and rapid introduction of new and
more efficient technologies. A1 is divided into three groups that describe
alternative directions of technological change: fossil intensive (A1FI),
non-fossil energy resources (A1T) and a balance across all sources (A1B).
- Storyline A2 describes a very heterogeneous world with high
population growth, slow economic development and slow technological change.
- Storyline B1 describes a convergent world, with the same global
population as A1, but with more rapid changes in economic structures toward a
service and information economy.
- Storyline B2 describes a world with intermediate population and
economic growth, emphasising local solutions to economic, social, and
environmental sustainability.
2.10
Dr Mark Howden of CSIRO acknowledged the difficulties that uncertainty
in climate change projections could cause for those in the agricultural sector,
but believes that this uncertainty should not stop decision-making:
To some extent there is a bit of irreducible uncertainty
associated with this. In terms of climate change, yes, there is uncertainty
associated with that, but uncertainty does not stop people making decisions. Uncertainty
is just an integral part of making decisions on an everyday basis. It is part
of how governments make decisions.[12]
2.11
Ms Nicolette Boele of the Agricultural Alliance for Climate Change
indicated to the committee that, while there may be barriers to scientific
understanding, what is really missing is the political will to stand behind
policies and promote market confidence:
No question, there would be more money and more focus on the
science. But the political will and the political statements around the role
that science can play is just as important as getting farmers paid to change
their land management.[13]
2.12
In contrast, the NSW Irrigators Council argued that the scientific
evidence presented offered 'far too wide a range' of impacts upon which to base
long term policy.[14]
Future climate projections
2.13
This section of the report outlines the projections for future climate,
starting with general global predictions, and then setting out specific
predictions for Australia. The information is drawn from the IPCC's Fourth
Assessment Report and Climate Change in Australia.
2.14
These are not the only climate projections studies relevant to Australia.[15]
However, the committee also notes that the IPCC Fourth Assessment Report and Climate
Change in Australia are regarded as the most comprehensive studies using the
most extensive and refined modelling techniques, and so the committee has
limited its consideration to these reports.[16]
Global climate
2.15
One of the significant observations in the IPCC's Fourth Assessment
Report is that:
[w]arming of the climate system is unequivocal, as is now
evident from observations of increases in global average air and ocean
temperatures, widespread melting of snow and ice and rising global average sea
level... [17]
2.16
The IPCC makes the following projections of future changes in climate:
[f]or the next two decades a warming of about 0.2°C per decade is
projected for a range of [emissions scenarios]. Even if the concentrations of
all [greenhouse gases] and aerosols had been kept constant at year 2000 levels,
a further warming of about 0.1°C per decade would be expected. Afterwards,
temperature projections increasingly depend on specific emissions scenarios...[18]
Australian climate
2.17
Climate Change in Australia makes climate projections for the
years 2030, 2050 and 2070 for a wide range of climate variables.[19]
This section of the report details the projections for temperature,
precipitation and drought, and then provides a summary of some of the other
climate variables.
Temperature[20]
2.18
Temperature projections for 2030 do not vary much among the emissions
scenarios, so the results presented in Climate Change in Australia are
for a mid-range emissions scenario, the A1B scenario. Those projections were
that, compared to 1990:[21]
for most locations the mean warming is 0.7-0.9ºC in coastal
areas and 1-1.2ºC inland. In winter, warming is projected to be a little
smaller than in the other seasons, as low as 0.5ºC in the far south. Warming is
usually smaller near the coasts than further inland, an exception being in the
northwest, where the warming exceeds 1.3ºC in spring. The annual result has a
similar pattern to the seasons, with the warming being largest in the interior
and the north-west.[22]
2.19
By 2050, the best estimate for annual warming is 1.2°C
for the B1 (low emission) scenario to 2.2°C for the A1F1 (high emission)
scenario. By 2070 the best estimate of annual warming is 1.8°C for the B1
scenario and around 3.4°C for the A1F1 scenario.[23]
The pattern of warming in 2050 and 2070 is similar to the 2030 projections –
with less warming in the south and north-east and more inland.
2.20
There is also a projected increase in the frequency of hot days and warm
nights, and a decrease in the frequency of frosts.
Precipitation[24]
2.21
Climate Change in Australia notes that there is a disparity in
rainfall projections by the different climate models, and as a result it is not
possible to make definitive statements about the direction of precipitation
changes.[25]
Projections of precipitation changes are presented here as a percentage change
relative to the 1990 baseline.
2.22
The best estimate projections of precipitation for 2030 for the A1B
emissions scenario were for little change in precipitation in the far north of Australia
and decreases of 2-5% elsewhere. In terms of seasonal forecasts:
[i]n summer and autumn decreases [in precipitation] are smaller
and there are slight increases in the east. Decreases of around 5% prevail in
winter and spring, particularly in the south-west where they reach 10%. These
are still smaller, however, than the decreases that were observed there in
previous decades ...[26]
2.23
By 2050, under a low emissions scenario (B1), best estimates of annual
precipitation were for little change in the far north grading southwards to a decrease
of 5%, relative to the 1990 baseline. Under the high emissions scenario (A1F1),
the best estimate is for little change in the far north, grading to a 7.5%
decrease in precipitation elsewhere.
2.24
By 2070, the best estimates for a low emissions scenario are similar to
those seen in the 2050 high emissions scenario projections. For the high emissions
scenario, the projections are for little change in the far north grading to
around a 10% decrease in the south-west.
2.25
The seasonal changes in precipitation for 2050 and 2070 follow the same
trend as those seen in the 2030 projections, but are larger.
2.26
Some of the other key findings in Climate Change in Australia in
relation to precipitation are:
- models show an increase in daily precipitation intensity, that is
the amount of rain on a rain day, and an increase in the number of dry days;
- snow cover, average snow season lengths and snow depth is likely
to decline.
2.27
Climate Change in Australia projected the changes in
'agricultural drought', meaning a period of extremely low soil moisture. The
projections were made only for the low (B1) and high (A1F1) emissions scenarios
for the years 2030 and 2070. The results of the projections were summarised as:
up to 20% more drought-months over most of Australia by 2030, with
up to 40% more droughts by 2070 in eastern Australia, and up to 80% more
droughts in south-western Australia.[28]
Other climate variables[29]
2.28
As noted above Climate Change in Australia sets out projections
for a range of climate variables. This section of the report briefly summarises
the projections for some of those variables:
- Small decreases in humidity are projected over most of Australia,
with largest decreases in the south and west, and little change along the east
coast and in Tasmania.[30]
- Annual potential evapotranspiration is projected to increase over
Australia, with the largest increases being in the north and east.
- In south-eastern Australia there is a substantial increase in
fire weather risk likely at most sites.[31]
- There is the potential for significant increases in inundations
from storm surges, resulting in flooding and erosion, due to higher mean sea
level and more intense weather systems.
- Studies indicate a likely increase in the proportion of tropical cyclones
in the more intense categories, but a possible decrease in the total number of
cyclones.
- There are indications that hail risk may increase over the
south-east coast of Australia.
Utility of climate projections
2.29
During the course of the inquiry, the committee received evidence and
submissions relating to the utility of the projections of future climate for
the agricultural sector. Of particular importance was the need for a
downscaling of projections to a regional level. A further issue raised with the
committee was the communication of climate projections in a manner that is
meaningful to farmers and others in the agricultural sector. These issues are
discussed below.
Downscaling of projections
2.30
Throughout the inquiry the committee was told of the need to downscale
climate projections in terms of time and space.[32]
2.31
Apple and Pear Limited stated that the climate models were better at
capturing the 'broad-global scale' than the more localised national or regional
scale.[33]
Growcom highlighted the need for accurate, downscaled climate projections to
the horticultural sector:
[f]or the industry to effectively respond to climate challenges,
accurate and detailed information on regional-scale climate changes and how
they will affect production and marketing is required. This information is
critical to inform the development of management strategies at enterprise,
regional and industry scales to effectively manage future climate change
impacts.[34]
2.32
Dr Beverly Henry, of Meat and Livestock Australia, indicated that downscaling
climate projections was only part of the issue:
The issues for us, though, are how we get downscaled projections
from those models at a scale that we can give to farmers to make decisions. We
have to get the regional scale outlooks on the same time frame that farmers
make decisions on, but then link them also to the biophysical-type models that
will tell us what the impacts will be on pasture growth and on animal
production. So there are two steps to do with getting better projections: the
regional scale models and then the linking to the impacts at farm level.[35]
2.33
Dr Michael Robinson, of Land and Water Australia, also noted the desire
in the agricultural sector for better climate projections on a finer scale with
greater certainty.[36]
2.34
Climate Change in Australia stated that while climate models are
continuing to improve, confidence in climate model projections varies with
spatial and temporal scale:
[h]ighest confidence is attached to results analysed at the
coarsest spatial and temporal scales, such as global or hemispheric annual
means, and decreases with finer scales, such as sub-continental or regional daily
variability. This is partly because the magnitude of natural variability increases
as scales decrease, so that regional climate change signals are more easily
masked by climate variability. Furthermore, local influences on climate (such
as regional topography or processes) become more important at finer spatial
scales.[37]
2.35
BoM's submission indicated that the development of improved climate
models is an area of research priority in its organisation:
... continued research and improvements of
climate models and in methods used to produce projections are essential. In
late 2006 senior researchers from the Bureau of Meteorology and CSIRO defined
Australia’s climate change knowledge gaps and research priorities. Of
particular note was the need to improve the simulations of the earth's climate
system by advancing to new generation climate models, which not only contain
the physics of the atmosphere, oceans and cryosphere (as done in earlier
generation models), but also the physics and/or chemistry of interrelated
aspects such as the biosphere and radiatively active gases. Such improvements
would also include a full carbon cycle, covering the terrestrial (including
full vegetation model), ocean and atmosphere systems.[38]
Communication
2.36
The committee's attention was also drawn to the need to communicate
climate projections in a manner that assists farmers in their decisions making.
2.37
The Primary Industries & Natural Resources Curriculum Centre, TAFE
NSW, believes that existing scientific evidence is not readily available to the
population generally and recommended that all available data be presented in
Plain English, which should be easily understood.[39]
2.38
The Australian Landcare Council called for:
regional, national and international communication of scientific
information about climate change, that is all inclusive, meaningful and useful.[40]
2.39
In evidence to the committee Ms Nicolette Boele, representing the
Agricultural Alliance on Climate Change, highlighted the difficulty of choosing
the best means to communicate with those in the agricultural sector:
We have done a little bit of research on how to communicate
climate science to the agricultural sector and the regional and rural
communities that support it. We did find that generally farm sizes are getting
larger and that the population is ageing, which raises a whole lot of questions
about which medium you can reach the sector with.
...These people are very busy; they are running businesses. It is
only really the big end of town that has the time, resources and intentions to
go and actively find more data about climate change and what it might do for
their businesses
... it is probably the content and quality of the data but also
how that extension happens, how you actually make climate information not an
added thing but included in existing paths of communication for those people.[41]
2.40
Ms Boele was also supportive of using those who were well-respected in
the farming industry as communicators of scientific information:
...this is a particular community that really listens to its
peers. Instead of having CSIRO type science communicators talking at, down and
across to farmers, if you can actually somehow have champions within
communities that are esteemed by their peers, that is going to go a hell of a
lot faster.[42]
2.41
BoM set out in its submission some of the programs it has in place for
communicating climate information, including:[43]
- the seasonal outlook service for rainfall and temperature;
- commentary on the state of the El Niño-Southern Oscillation; and
- the Water and Land website providing meteorological information specifically
tailored for primary industry and natural resource management.
Committee view
2.42
The evidence before the committee is that there is general acceptance by
those in the agricultural sector that climate change is occurring.[44]
2.43
The changes in climate projected in the IPCC's Fourth Report and Climate
Change in Australia would have significant impacts on the Australian
agricultural sector, and these impacts will be discussed in the committee's
final report. However, the committee is concerned that climate projections may
be underestimating the amount of warming which may occur in future:
There is a significant possibility that warming may occur in
excess of these values, particularly later in the century, although the
likelihood of this occurrence is impossible to estimate at this stage.[45]
2.44
The committee appreciates that significant work has, and continues, to
occur on producing long-term climate projections on a global and national
scale. The committee recognises the need for more work to be done to downscale
climate change projections to a local level to be of greater use to farmers in
decision-making. The committee notes that there is already work in progress on
improving and downscaling climate models and projections.[46]
2.45
The committee believes that there is an urgent need for improved
communication of climate projections to farmers and others in the agricultural
sector. The committee understands the uncertainties and limitations inherent in
climate projections cause frustration for those in the agricultural sector
trying to plan for a changing future climate. It is the committee's view that
better communication of climate projections is required in order for this
information to be of use to farmers and others in the agricultural sector. The
committee encourages CSIRO, BoM and other research groups involved in climate
projections to give consideration to the manner and mode in which climate
projections are presented to the agricultural sector.
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