Figure 7.1.1
The projected temperature range [for Australia] by 2090 shows larger differences between RCPs, withMedian projected temperature increases [for RCP8.5] are typically 4°C by 2090, while those in the north-east and far south are 3°C or less.
- 0.6 to 1.7 °C for RCP2.6,
- 1.4 to 2.7 °C for RCP4.5 and
- 2.8 to 5.1 °C for RCP8.5. …
(CCIA Technical Report, 2015, p 91-2)
Table 7.1.2 (Adapted): Projected number of days over 35°C in Australian capital cities(CCIA Technical Report, 2015, p 98) | ||||
| 1995 | 2030 | 2090 | ||
|---|---|---|---|---|
| RCP4.5 | RCP4.5 | RCP8.5 | ||
| Perth | 28.0 | 36.0 | 43.0 | 63.0 |
| Adelaide | 20.0 | 26.0 | 32.0 | 47.0 |
| Brisbane (Amberley) | 12.0 | 18.0 | 27.0 | 55.0 |
| Darwin | 11.0 | 43.0 | 111.0 | 265.0 |
| Melbourne | 11.0 | 13.0 | 16.0 | 24.0 |
| Canberra | 7.1 | 12.0 | 17.0 | 29.0 |
| Sydney | 3.1 | 4.3 | 6.0 | 11.0 |
| Hobart | 1.6 | 2.0 | 2.6 | 4.2 |
Australian Climate Variability and Change
By 2030, Australian annual average temperature is projected to increase by 0.6-1.3°C above the climate of 1986–2005 under RCP4.5 with little difference between RCPs.
The projected temperature range by 2090 shows larger differences between RCPs, with
- 0.6 to 1.7°C for RCP2.6,
- 1.4 to 2.7°C for RCP4.5 and
- 2.8 to 5.1°C for RCP8.5.
Extreme fire weather days have increased at 24 out of 38 Australian sites from 1973-2010, due to warmer and drier conditions.
(p 8)
A recent analysis of northern hemisphere heatwaves has shown
- that very hot summers have increased in frequency approximately 10 fold since the 1950s, and
- that a number of recent summer heatwaves (such as the European 2003 and Moscow 2010 heatwaves) have been so extreme that their probability of occurrence without global warming would be close to zero.
[Greenhouse] gas concentrations [may] end up being larger than those assumed under the RCP8.5 scenario [+2.6 to 4.8 °C relative to 1986–2005].
Higher values might arise through the release of carbon dioxide or methane to the atmosphere from, for example, thawing permafrost from Arctic and sub-Arctic peat bogs over the 21st century.
Some thawing has already occurred over Alaska, Canada and northern Russia and further thawing is expected.
However, the magnitude of the increase in emissions from thawing over the 21st century is very uncertain.
(p 34)
Australia will warm substantially during the 21st century
There is very high confidence in continued increases of mean, daily minimum and daily maximum temperatures throughout this century for all regions in Australia.
The magnitude of the warming later in the century is strongly dependent on the emission scenario.
Warming will be
- large compared to natural variability in the near future (2030) (high confidence), and
- very large compared to natural variability late in the century (2090) under RCP8.5 (very high confidence). …
Mean warming is projected to be greater than average in inland Australia, and less in coastal areas, particularly in southern coastal areas in winter.
(p 91)
More frequent and hotter hot days and fewer frost days are projected
Projected warming will result in
- more frequent and hotter hot days and warmer cold extremes (very high confidence) and
- reduced frost (high confidence).
Hot days are projected to occur more frequently.
For example, in Perth, the average number of days per year above 35°C or above 40°C by 2090 is projected to be 50% greater than present under RCP4.5.
The number of days above 35°C in Adelaide also increases by about 50% by late in the century, while the number of days above 40°C more than doubles.
Locations where frost occurs only a few times a year under current conditions are projected to become nearly frost-free by 2030.
Under RCP8.5 coastal areas are projected to be free of frost by 2090 while frost is still projected to occur inland.
(p 95)
Cool-season rainfall is projected to decline in southern Australia; changes are uncertain elsewhere
Southern Australia
Cool season (winter and spring) rainfall is projected to decrease (high confidence), though little change or increases in Tasmania in winter are projected (medium confidence).
The winter decline may be as great as 50% in south-western Australia in the highest emission scenario (RCP8.5) by 2090.
The direction of change in summer and autumn rainfall in southern Australia cannot be reliably projected, but there is medium confidence in a decrease in south-western Victoria in autumn and in western Tasmania in summer.
Eastern Australia
There is high confidence that in the near future (2030), natural variability will predominate over trends due to greenhouse gas emissions.
For late in the century (2090), there is medium confidence in a winter rainfall decrease.
Northern Australia and northern inland areas
There is high confidence that in the near future (2030) natural variability will predominate over trends due to greenhouse gas emissions.
There is low confidence in the direction of future rainfall change for late in the century (2090), but substantial changes to wet-season and annual rainfall cannot be ruled out.
(p 99)
Extreme rain events are projected to become more intense
Extreme rainfall events (wettest day of the year and wettest day in 20 years) are projected to increase in intensity with high confidence.
Confidence is reduced to medium confidence for south-western Western Australia, where the reduction in mean rainfall may be so strong as to significantly weaken this tendency.
(p 115)
In a warming climate, the atmosphere can hold more water vapour, around 7% more for every degree of global warming.
(p 33)
Time in drought is projected to increase in southern Australia, with a greater frequency of severe droughts
The time in drought is projected to increase over southern Australia with high confidence, consistent with the projected decline in mean rainfall.
Time in drought is projected to increase with medium or low confidence in other regions.
The nature of droughts is also projected to change with a greater frequency of extreme droughts, and less frequent moderate to severe drought projected for all regions (medium confidence).
(p 119)
Snowfall in the australian alps is projected to decrease, especially at low elevations
There is very high confidence that as warming progresses there will be a decrease in snowfall, an increase in snowmelt and thus reduced snow cover.
These trends will be large compared to natural variability and most evident at low elevations.
(p 123)
Mean wind speeds are projected to decrease in southern mainland Australia in winter and increase in Tasmania
By 2030, changes in near-surface wind speeds are projected to be small compared to natural variability (high confidence).
By 2090,
- wind speeds are projected to decrease in southern mainland Australia in winter (high confidence) and south-eastern mainland Australia in autumn and spring.
Winter decreases are not expected to exceed 10 % under RCP8.5. - Wind speed is projected to increase in winter in Tasmania.
Projected changes in extreme wind speeds are generally similar to those for mean wind.
(p 125)
Tropical cyclones may occur less often, become more intense, and may reach further south
Tropical cyclones are projected to become less frequent with a greater proportion of high intensity storms (stronger winds and greater rainfall) (medium confidence).
A greater proportion of storms may reach south of 25 degrees South (low confidence).
Mid-latitude weather systems are projected to shift south in winter and the tropics to expand southward
The observed intensification of the subtropical ridge and expansion of the Hadley Cell circulation are projected to continue in the 21st century (high confidence).
Both represent an expansion of the tropics.
(p 129)
More sunshine is projected in winter and spring
There is high confidence in little change in solar radiation over Australia in the near future (2030).
Late in the century (2090), there is medium confidence in an increase in winter and spring in southern Australia.
The increases in southern Australia may exceed 10% by 2090 under RCP8.5.
(p 131)
Lower relative humidity
Relative humidity is projected to decline in inland regions and where rainfall is projected to decline.
By 2030, the decreases are relatively small (high confidence).
By 2090,there is high confidence that humidity will decrease in winter and spring as well as annually, and there is medium confidence in declining relative humidity in summer and autumn.
(p 133)
Higher evaporation rates
There is high confidence in increasing potential evapotranspiration (atmospheric moisture demand) closely related to local warming, although there is only medium confidence in the magnitude of change.
(p 134)
Soil moisture is projected to decrease and future runoff will decrease where rainfall is projected to decrease
There is high confidence in decreasing soil moisture in the southern regions (particularly in winter and spring) driven by the projected decrease in rainfall and higher evaporative demand.
There is medium confidence in decreasing soil moisture elsewhere in Australia where evaporative demand is projected to increase but the direction of rainfall change is uncertain.
Decreases in runoff are projected with high confidence in south-western Western Australia and southern South Australia, and with medium confidence in far south-eastern Australia, where future rainfall is projected to decrease.
The direction of change in future runoff in the northern half of Australia cannot be confidently projected because of the uncertainty in the direction of rainfall change.
(p 136)
In Southern Australia practically all models show a decrease [in annual runoff] by 2090, ranging from around zero to −30% and zero to −60% under RCP4.5 and RCP8.5, respectively.
(p 138)
Southern and eastern Australia are projected to experience harsher fire weather; changes elsewhere are less certain
Projected warming and drying in southern and eastern Australia will lead to fuels that are drier and more ready-to-burn, with
- increases in the average forest fire danger index and
- a greater number of days with severe fire danger
There is medium confidence that there will be little change in fire frequency in tropical and monsoonal northern Australia.
There is low confidence in projections of fire risk in the arid inland areas where fire risk is dependent on availability of fuel, which is driven by episodic rainfall.
(p 139)
Sea levels will continue to rise throughout the 21st century and beyond
In line with global mean sea level, Australian sea levels are projected to rise through the 21st century (very high confidence), and are very likely to rise at a faster rate during the 21st century than over the past four decades, or the 20th century as a whole, for the range of RCPs considered (high confidence).
Sea level projections for the Australian coastline by 2090 (the average of 2080 to 2100) are comparable to, or slightly larger than (by up to about 6 cm) the global mean sea level projections of
- 26-55 cm for RCP2.6 and
- 45-82 cm in RCP8.5 (medium confidence).
Regional projections for 2100 (a single year) are not given because of the effect of interannual to decadal variability on regional sea levels.
However, for all scenarios, global averaged sea level in 2100 will be higher than in 2090 and sea level is projected to continue to rise beyond 2100.
(p 148)
Extreme sea levels will rise
Taking into account uncertainty in sea level rise projections and nature of extreme sea levels along the Australian coastline, an indicative extreme sea level ‘allowance’ is calculated.
This allowance is the minimum distance required to raise an asset to maintain current frequency of breaches under projected sea level rise. Along the Australian coast, these allowances are comparable to the upper end of the range of the respective sea level projections (medium confidence).
The main contribution to increasing extreme sea levels is from the rise in mean sea level (medium confidence).
Contributions to extreme sea levels from changes in weather events are projected to be small or negative (low confidence).
(p 153)
Oceans around Australia will warm
There is very high confidence that sea surface temperatures around Australia will rise, with the magnitude of the warming dependent on the RCP.
Near-coastal sea surface temperature rise around Australia is typically around 0.4-1.0°C by 2030 and around 2-4°C by 2090 under RCP8.5 compared to current (1986–2005). …
[Sea surface warming] off the east of Australia and Tasmania … has been 2 to 3 times faster than the global mean.
(p 157)
Ocean salinity may change
Changes in sea surface salinity reflect changes in rainfall and may affect ocean circulation and mixing.
A net reduction in the salinity of Australian coastal waters is projected, but this projection is of low confidence.
For some southern regions, models indicate an increase in sea surface salinity, particularly under higher emissions.
(p 160)
Oceans around Australia will become more acidic
There is very high confidence that around Australia the ocean will become more acidic, with a net reduction in pH.
There is also high confidence that the rate of ocean acidification will be proportional to the carbon dioxide emissions.
There is medium confidence
- that long-term viability of corals will be impacted under RCP8.5 and RCP4.5, and
- that there will be harm to marine ecosystems from the large reduction in pH under RCP8.5.
(Technical Report, Climate Change in Australia: Projections for Australia's National Resource Management Regions, 2015, emphasis added)
State of the Climate 2016
- Australia’s climate has warmed … by around 1 °C since 1910.
- The duration, frequency and intensity of extreme heat events have increased across large parts of Australia.
- There has been an increase in extreme fire weather, and a longer fire season, across large parts of Australia since the 1970s.
- May–July rainfall has reduced by around 19% since 1970 in the southwest of Australia. …
- Global average annual carbon dioxide levels are … likely the highest in the past two million years.
- 2015 was the warmest year on record for the globe since … 1880.
The last 15 years are among the 16 warmest years on record. - Globally-averaged ocean temperatures and heat content are increasing.
Observations reveal this warming extends to at least [2 km] below the surface. - Globally-averaged sea level has risen over 20 cm since the late 19th century, with about one third of this rise due to ocean warming and the rest from melting land ice and changes in the amount of water stored on the land.
The recent drying across southern Australia is the strongest recorded large-scale change in rainfall since national records began in 1900.
(p 10)
The impact of all greenhouse gases in the atmosphere combined can be expressed as an ‘equivalent CO2’ atmospheric concentration, which reached 487 ppm in 2015.
(p 19)
The global annual CO2 increase in 2015 was 3.0 ppm, the largest ever observed. …
During 2015 the rate of increase in fossil fuel emissions slowed.
However, the strong El Niño, which led to increased fires and associated greenhouse gas emissions, as well as a weakening of natural CO2 sinks through drought and reduced rainfall over large regions led to increased emissions from natural sources in 2015.
(p 20)
State of the Climate 2014
- {2013 was Australia’s warmest year on record …}
- Australia’s climate has warmed by 0.9°C since 1910 …
- Global mean temperature has risen by 0.85°C from 1880 to 2012. …
Limiting the magnitude of future climate change requires large and sustained net global reductions in greenhouse gases.
(p 3-4)
Australian Climate
Seven of the ten warmest years on record have occurred since 1998.
Over the past 15 years,
- the frequency of very warm months has increased five-fold and
- the frequency of very cool months has declined by around a third,
Since 2001, the number of extreme heat records in Australia has outnumbered extreme cool records by
- almost 3 to 1 for daytime maximum temperatures, and
- almost 5 to 1 for night-time minimum temperatures.
[Overall,] Australian average annual rainfall has increased since national records began in 1900, largely due to increases in rainfall from October to April, and most markedly across the northwest. …
[However, since] 1970 there has been a 17% decline in average winter rainfall in the southwest of Australia.
{In the far southwest, streamflow has declined by more than 50% since the mid-1970s.}
The southeast has experienced a 15% decline in late autumn and early winter rainfall since the mid-1990s, with a 25% reduction in average rainfall across April and May. …
[And in] the far southeast, streamflow during the 1997–2009 Millennium Drought was around half the long-term average.
(p 6)
Number of days each year where the Australian area-averaged daily mean temperature is above the 99th percentile for the period 1910–2013. …
This metric reflects the spatial extent of extreme heat across the continent and its frequency.
Half of these events have occurred in the past twenty years.
Recent studies examining heavy monthly to seasonal rainfall events that occurred in eastern Australia between 2010 and 2012 have shown that the magnitude of extreme rainfall is mostly explained by natural variability, with potentially a small additional contribution from global warming. …
The research on cyclone frequency in the Australian region is equivocal, with some studies suggesting no change and others a decrease in numbers since the 1970s.
(p 8-9)
Global Atmosphere and Cryosphere
- Ice-mass loss from the Antarctic and Greenland ice sheets has accelerated over the past two decades.
- Arctic summer minimum sea-ice extent has declined by between 9.4 and 13.6% per decade since 1979, a rate that is likely unprecedented in at least the past 1,450 years.
- Antarctic sea-ice extent has slightly increased by between 1.2% and 1.8% per decade since 1979.
- from an estimated mean of 30 gigatonnes per year (Gt/yr) for the period from 1992 to 2001,
- to 147 Gt/yr for the period 2002 to 2011.
The average rate of ice loss from glaciers around the world, excluding glaciers on the periphery of the ice sheets, was
- very likely 226 Gt/yr over the period 1971 to 2009, and
- very likely 275 Gt/yr over the period 1993 to 2009. …
The [slight] increase in Antarctic sea-ice extent has been linked to several possible drivers, including
- freshening of surface waters due to increased precipitation and the enhanced melting of ice shelves, and
- changes in atmospheric circulation resulting in greater sea-ice dispersion.
Oceans
- Global mean sea level … in 2012 was 225 mm higher than in 1880. …
- Ocean acidity levels have increased [by 26% since 1750.]
The ocean today is warmer, and sea levels higher, than at any time since the instrumental record began.
- The upper layer of the ocean, from the surface to a depth of 700 metres, has increased its heat content by around 17 × 10^22 joules since 1971, accounting for around 63% of additional energy accumulated by the climate system.
- Warming below 700 metres over the same period accounts for approximately 30% of additional energy.
- The remaining 7% has been added to the cryosphere, atmosphere and land surface.
Change in ocean heat content (in joules) from the full ocean depth, from 1960 to present.(p 11)
Shading provides an indication of the confidence range of the estimate.
Global sea level fell during the intense La Niña event of 2010–2011.
This was ascribed partly to the exceptionally high rainfall over land which resulted in floods in Australia, northern South America, and Southeast Asia.
[And] was compounded by the long residence time of water over inland Australia.
Recent observations show that sea levels have rebounded in line with the long-term trend.
(p 12)
Greenhouse Gases
- The increase in atmospheric CO2 concentrations from 2011 to 2013 is the largest two-year increase ever observed.
Global CO2 emissions from the use of fossil fuel are estimated to have increased in 2013 by 2.1% compared with the average of 3.1% per year from 2000 to 2012.
(p 13)
Global atmospheric CH4 … and N2O [concentrations] are at their highest levels for at least 800 000 years.
[The combined] ‘equivalent CO2’ atmospheric concentration [of all GHGs] reached 480 ppm in 2013.
(p 14)
Future climate scenarios for Australia
- [An up to 3-fold] increase in the number of extreme fire-weather days is expected in southern and eastern Australia [by 2015,] with a longer fire season in these regions. …
- The frequency and intensity of extreme daily rainfall is projected to increase. …
- Projected sea-level rise will increase the frequency of extreme sea-level events.
Warming by 2070, compared to 1980 to 1999, is projected to be
- 1.0 to 2.5°C for low greenhouse gas emissions and
- 2.2 to 5.0°C for high emissions [ie business as usual. …]
Further decreases in average rainfall are expected over southern Australia …
[Consequently, droughts] are expected to become more frequent and severe in southern Australia. …
Reductions in global greenhouse gas emissions would increase the chance of constraining future global warming.
Nonetheless adaptation is required because some warming and associated changes are unavoidable.
(p 15)
State of the Climate 2012
Australian average temperatures over land
Each decade has been warmer than the previous decade since the 1950s. …
[Daily] maximum temperatures have increased by 0.75 °C [and] overnight minimum temperatures have warmed by more than 1.1 °C …
2010 and 2011 were Australia’s coolest years recorded since 2001 due to two consecutive La Niña events. … (p 3)
Oceans
Global-average mean sea level for 2011 was 210 mm above the level in 1880.
Global-average mean sea level rose faster between 1993 and 2011 [3 mm/year] than during the 20th century as a whole [1.7 mm/year.]
(p 6)
State of the Climate 2010
Since 1960 the mean temperature in Australia has increased by about 0.7°C. …
Some areas have experienced warming since 1960 of up to 0.4 °C per decade [3 times the global average] resulting in total warming over the five decades of 1.5 to 2ºC.
(p 1)
Contents
No profit in climate change research
Australian attitudes to climate change and adaptation: 2010-14
State of the Climate 2016
State of the Climate 2014
State of the Climate 2012
Climate Science and Solutions
Would you like to know more?
The Commonwealth Science and Industrial Research Organisation (CSIRO)
- Australian attitudes to climate change and adaptation: 2010-2014, 2015.
Leviston, Greenhill & Walker.
Do you think that climate change is happening?
(Adapted from Figure 1, p 3)Yes 78% No 22%
What best describes your thoughts about climate change?
(Adapted from Figure 2, p 4)Happening 84.5% Human induced 45.9% Natural fluctuation 38.6% Not happening / Don't know 15.6% [Of those who thought climate change was happening 54.3% attributed it to human activity and 45.7% to natural variation.]
Percentage agreeing that human-induced climate change is happening
(Adapted from Figure 42, p 45)Voting behaviour at the last federal election
N = 3789 (100%)
Liberal 28% 1616 (43%) Labor 59% 1406 (37%) Green 76% 437 (12%) Independent 46% 172 (5%) National 22% 158 (4%) On average, participants with more left-wing orientations were more likely to be sure climate change was happening, were more worried about it, and thought it more important.
However, the strength of the relationship between political orientation and individual climate-relevant behaviours was very small.
[Of the 269 people who responded to all five surveys, nearly] half (48.5%) changed their selection at least once [between 2010 and 2014.]
Between 2013 and 2014, the percentage of repeat respondents changing their selection was 29%.
(p 11)
The most common shift [between 2010 and 2014] was to move from the opinion that climate change was human-induced to the opinion that it was happening, but natural (11.2% of respondents).
[By contrast, 5.6% switched from natural to human induced.
There was, therefore, a net reduction of 5.8% in the human induced cohort (48.0% to 42.4%).] (p 12)
Those who thought climate change was not happening (7.9% of respondents from Figure 2) strongly overestimated the prevalence of their own opinion (49.1%) [among the broader community.
Whereas, those] who thought that climate change was [happening slightly underestimated] the broader prevalence of their own opinions.
Every group overestimated the percentage of people who denied climate change was happening.
(p 6, emphasis added)
Overall, respondents estimated that 61.5% of climate change was attributable to human activity.
[Remarkably,] even those who thought climate change was not happening at all thought [that] roughly a third of climate change was attributable to human activity.
(p 7)
[This] suggests that people's basic opinions do not represent a static belief, but rather might best be viewed as a 'positioning statement' that gives a broad indication of the perceived threat posed by climate change, and the urgency and magnitude with which a person feels it should be addressed.
(p 64)
Those who think climate change is human-induced were more likely to say ‘scientific research’ was the main basis for their opinion.
Those who thought climate change was not happening, or caused by natural processes, were more likely to select ‘common sense’, ‘the weather’, or ‘historical events’ as their basis.
Very few selected ‘politicians and government’ or ‘news and media’.
(p viii)
People’s engagement in individual climate-relevant behaviour has reduced in 2014. …
(p ix)
Between 2010 and 2014,- 48% of repeat respondents’ pro-environmental behaviour scores decreased,
- 19.3% remained steady, and
- 32.7% increased.
People tend to overestimate how much they do compared to others.
More than 90% of respondents estimated they engaged in the same or more behaviours than other Australians.
Less than 7% thought they did less than other Australians. …
(p ix)
More than half of respondents reported experiencing at least some [personal] injury, loss, or damage as a result of- extreme high temperatures (61%),
- heatwaves (61%),
- heavy rain (59%),
- drought and water scarcity (57%), or
- hailstorms (51%).
There is little familiarity with climate change terminology, but this is improving.
[In 2014, roughly] one in five respondents had heard of ‘climate mitigation’ [21% vs 18% in 2013] while nearly one in three had heard of ‘climate adaptation’ [31% vs 19% in 2012].
(p ix)
There is broad support for a wide range of adaptation initiatives.
Most support was given to- investment in renewable energy resources,
- protection from invasive species,
- increased investment in public transport, and
- restrictions on development in vulnerable areas.
- investment in nuclear power stations and
- increased aid to overseas countries impacted by climate change. …
Anger, fear, and powerlessness were rated as the most commonly felt emotion in response to climate change.
(p x)
- State of the Climate 2012, CSIRO / Australian Bureau of Meteorology, 13 March 2012.
Temperature
Australian average temperatures over land
The average temperature [over the last decade] has been more than 0.5 °C warmer than the … 1961-1990 long-term average.
(p 3)
The rate of very hot (greater than 40 °C) daytime temperatures has been increasing since the 1990s.
(p 4)
Rainfall
A very strong La Niña event in 2010, followed by another La Niña event in 2011, brought the highest two-year Australian-average rainfall total on record. …
[Despite this] Southwest Western Australia experienced its lowest rainfall on record in 2010 and only average rainfall during 2011 …
(p 5)
Oceans
Rising global-average mean sea level
The observed global-average mean sea-level rise since 1990 is near the high end of [the IPCC AR4] projections …
Rising sea level around Australia
Since 1993, the rates of sea-level rise to the north and northwest of Australia have been 7 to 11 mm per year, two to three times the global average, [while] rates of sea-level rise on the central east and southern coasts of the continent are mostly similar to the global average.
These variations are at least [partly due to] natural variability …
(p 6)
Greenhouse Gases
Carbon dioxide emissions
Australia [which represents 0.3% of global population] contributes about 1.3% of the global CO2 emissions.
Energy generation continues to climb and is dominated by fossil fuels …
The amount of … long-lived greenhouse gases [C02, Ch4 and N20] in the atmosphere reached a new high in 2011.
The concentration of CO2 … was 390 parts per million (ppm) - much higher than the natural range of 170 to 300 ppm during the past 800,000 years. …
The relative contributions to the enhanced greenhouse effect from pre-industrial times to 2011 … are:- CO2 (64%),
- CH4 (18%),
- synthetics (12%) and
- N2O (6%).
Observations of total CO2 emissions … are tracking along the higher end of expected emissions.
(p 8)
Sources of carbon dioxide
About 50% of the amount of CO2 emitted from fossil fuels, industry, and changes in land-use, stays in the atmosphere.
The remainder is taken up by the ocean and land vegetation, in roughly equal parts.
The extra carbon dioxide absorbed by the oceans is estimated to have caused about a 30% increase in the level of ocean acidity …
The observed trends in the isotopic (13C, 14C) composition of CO2 in the atmosphere and the decrease in the concentration of atmospheric O2 confirm that the dominant cause of the observed CO2 increase is the combustion of fossil fuels.
(p 9)
Understanding Global Warming
Australia in the context of global warming
Global-average surface temperatures were the warmest on record in 2010 …
2011 was the world’s … warmest year on record during a La Niña event. …
[There is at least a 90% likelihood] that most of the observed global warming since the mid-20th century is due to increases in greenhouse gases from human activities [and a less than 10% likelihood] that [it is due to] natural variability alone.
Changes in extreme weather events
Extreme events are relatively rare and identifying changes in intensity or frequency is more difficult than for changes in averages. …
Weather associated with high fire danger has shown a rapid increase in the late 1990s to early 2000s at many locations in south-eastern Australia. …
No significant trends in the total numbers of tropical cyclones or in the occurrence of the most intense tropical cyclones have been found in the Australian region.
(p 10)
Future Changes
Future Australian temperature, rainfall and extreme weather events
Australian average temperatures are projected to rise by [a further] 0.6 to 1.5 °C by 2030 when compared with the climate of 1980 to 1999.
The warming is projected to be in the range of 1.0 to 5.0 °C by 2070 …
For Australia as a whole, an increase in the number of dry days is expected, but it is also likely that rainfall will be heavier during wet periods.
{Droughts are expected to become more frequent in southern Australia …
[The] direction of projected changes to average rainfall over northern Australia is unclear as there is a lack of consensus among the models.}
[There is a more than 66% probability] that there will be [on average] fewer tropical cyclones in the Australian region … but [that] the proportion of intense cyclones [will] increase.
(p 11)
Climate change is continuing
Multiple lines of evidence show that global warming continues and that human activities are mainly responsible.
The fundamental physical and chemical processes leading to climate change are well understood. …
Uncertainties remain regarding- future levels of greenhouse gas concentrations …
- the precise timing and magnitude of changes, particularly at regional scales [and]
- tipping points in the climate system, such as the break-up of ice-sheets, which [could] lead to rapid climate change.
Unless greenhouse gas emissions decrease, we expect to see the temperature of the atmosphere and the oceans continue to warm and sea levels continue to rise at current or even higher rates than reported here.
(p 12)