21/12/2018

Australia Experiencing More Heat, Longer Fire Seasons And Rising Oceans

The Guardian - 

State of the climate report points to a long-term increase in the frequency of extreme heat events, fire weather and drought
Australia’s fire seasons are longer and more severe, the Bureau of Meteorology and CSIRO’s state of the climate report has found. Photograph: Qfes Media/PR image
Australia is experiencing more extreme heat, longer fire seasons, rising oceans and more marine heatwaves consistent with a changing climate, according to the Bureau of Meteorology and CSIRO’s state of the climate report.
The report, published every two years, measures the long-term variability and trends observed in Australia’s climate.
The 2018 report shows that Australia’s long-term warming trend is continuing, with the climate warming by just over 1C since 1910 when records began.
That warming is contributing to a long-term increase in the frequency of extreme heat events, fire weather and drought.
“Australia is already experiencing climate change now and there are impacts being experienced or felt across many communities and across many sectors,” said Helen Cleugh, the director of the CSIRO’s climate science centre.
The report’s key findings include:
  1. Australia’s fire seasons have lengthened and become more severe. In some parts of the country, the season has been extended by months.
  2. The number of extreme heat days continues to trend upward.
  3. There has been a shift to drier conditions in south-eastern and south-western Australia in the months from April to October.
  4. Rainfall across northern Australia has increased since the 1970s, particularly during the tropical wet season in north-western Australia.
  5. Oceans around Australia have warmed by about 1C since 1910, which is leading to longer and more frequent marine heatwaves that affect marine life such as corals.
  6. Sea levels around Australia have risen by more than 20cm since records began and the rate of sea level rise is accelerating.
  7. There has been a 30% increase in the acidity of Australian oceans since the 1800s and the current rate of change “is ten times faster than at any time in the past 300 million years”.
Karl Braganza, the bureau of meteorology’s manager of climate monitoring, said the increase in average temperature was having an impact on the frequency or amount of extremes Australia experienced in any given year.
“In general there’s been around a five-fold increase in extreme heat and that is consistent whether you look at monthly temperatures, day time temperatures or night time temperatures,” he said.
Annual mean temperature anomaly, Australia
Temperature anomaly is the difference between the average temperature from 1961–1990 and the average temperature in a given year. Guardian graphic | Source: Bureau of Meteorology
He said there had been a reduction in rainfall of 20% in south-western Australia and in some places that was as high as 26%. In south-eastern Australia, April to October rainfall had fallen by 11%.
The report also highlights an increase in the number of extreme fire danger days in many parts of Australia, particularly in southern and eastern Australia.
Extreme heat days per year in Australia
Number of days each year where the Australian area-averaged daily mean temperature is extreme. Extreme days are those above the 99th percentile of each month from the years 1910–2017 Source: State of the Climate report
Braganza said there was a “clear shift” towards a lengthened fire season, more fire weather during that season and an increase in its severity.
“Often the worst fire weather occurs when you’ve had long-term drought, long-term above-average temperatures, maybe a short-term heatwave and then the meteorology that’s consistent with severe fire weather and the ability for fire to spread,” he said.
“It’s those types of compound events that are going to be most challenging going forward in terms of adapting to climate change in Australia.”
Change in fire weather conditions
Trends from 1978 to 2017 in the annual (July to June) sum of the daily Forest Fire Danger Index — an indicator of the severity of fire weather conditions. Positive trends, shown in the yellow to red colours, are indicative of an increasing length and intensity of the fire weather season. Source: State of the Climate report
David Cazzulino, the Great Barrier Reef campaigner for the Australian Marine Conservation Society, said the report confirmed what many Australians already knew about the rising risks of climate change.
“The big line around oceans warming one degree since 1910 is a huge wake-up call,” he said.
“It’s undeniable that warming oceans lead to more marine heatwaves, coral bleaching and coral mortality.”
He said the impact of climate change on the Great Barrier Reef, and climate change policy generally, would be a key campaign issue ahead of the 2019 federal election.
“We are running out of time to keep warming to a safe degree for the reef to have a future,” Cazzulino said.

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State Of The Climate 2018: Bureau Of Meteorology And CSIRO

The Conversation -  | 

The Australian Bureau of Meteorology and CSIRO have released their fifth biennial State of the Climate report.
Fire danger conditions are worsening in many areas of Australia. AAP Image/David Crosling
State of the Climate 2018 is the latest biennial snapshot of climate change in Australia. It focuses on observed long-term trends that are happening now and are likely to continue into the near future, as well as significant climate events that have occurred over the past two years. These changes are described through the latest observations from CSIRO and Bureau of Meteorology marine, atmospheric and terrestrial monitoring programs.
The report also summarises the latest climate research from Australia and around the world. This will help inform a range of economic, environmental and social risk assessments and responses by government, industry and communities.
Multiple lines of evidence show the climate system changing in ways that are discernible from natural variability, and consistent with a human influence on climate. These changes are having an impact on our natural and built environment.
In particular, climate change is being felt through an increase in the frequency and severity of high-impact weather events such as heatwaves, extreme fire weather conditions, coastal inundation and marine heatwaves. These trends are projected to continue.



Some of the report’s major findings are described below.

Passing major milestones
Australia’s average air temperature has warmed by just over 1℃ since national records began in 1910. Oceans around Australia have also warmed by around 1℃ since 1910.
Annual mean temperature over Australia and the seas surrounding Australia. Bureau of Meteorology. Author provided
Atmospheric concentrations of carbon dioxide are rising globally. Emissions from the burning of fossil fuels continue to increase, and are the main contributor to the rise in CO₂, with some contribution from changes in land use.
Atmospheric CO₂ concentrations measured at Cape Grim, Tasmania (one of three main global measuring stations, alongside Mauna Loa, Hawaii, and Nunavut, Canada), have persisted at levels above 400 parts per million (ppm) since 2016. What’s more, the combined concentration of all greenhouse gases exceeded the equivalent of 500 ppm CO₂ in mid-2018. These milestones haven’t been crossed for at least 800,000 years, and likely 2 million years.

Changes in the atmosphere and land
Australia’s warming trend has led to an increase in the frequency of extreme heat events. For example, very high monthly maximum temperatures that used to occur around 2% of the time (based on the average for 1951–80) now happen about 12% of the time (2003–17).
Other elements of Australia’s climate have also shown long-term changes. New analysis techniques now provide a more detailed picture of changes to fire weather through time. The annual total of daily values of the Forest Fire Danger Index is increasing over large areas of Australia. Most regions also saw an increase in the most extreme 10% of fire weather days, and fire seasons have lengthened.
Rainfall in April–October has been steadily decreasing in Western Australia’s Southwest, and has decreased since the 1990s in southeast Australia. In contrast, rainfall has increased in parts of northern Australia since the 1970s.
The observed long-term reduction in rainfall across southern Australia has led to even greater reductions in streamflow. Long-term average streamflow has decreased in most regions of southern Australia, and increased in regions of northern Australia.
A warmer atmosphere can hold more moisture, and this is an important driver of the observed increase in the intensity of short-duration rainfall, sometimes linked to flash flooding. Southern Australia is projected to experience decreases in average rainfall and more time spent in drought. Meanwhile, most of the country can expect an increase in rainfall intensity.
Historically, significant weather and climate events are often the result of the combined influence of several extreme factors at once. Higher temperatures during periods of below-average rainfall, for instance, can exacerbate drought conditions. Temperature, dryness and wind come together to create dangerous bushfire conditions.
Trend in the annual sum of Forest Fire Danger Index, 1978–2017. Bureau of Meteorology, Author provided
Changes in the ocean
The warming in Australia’s oceans has contributed to longer and more frequent marine heatwaves – defined as periods when sea surface temperatures are much warmer than average. The world’s oceans are a crucial moderator of the climate, taking up more than 90% of the extra heat in the system – most of it is absorbed by the Southern Ocean.
Sea levels continue to rise through the combined effects of warming oceans and melting ice from land-based glaciers and ice sheets. Global average sea level has risen by more than 20cm since 1880, but the rate varies from place to place. About 25% of the CO₂ emitted by human activity diffuses into the oceans, making them more acidic in the process.
The past two years, 2016 and 2017, have seen back-to-back bleaching events in parts of the Great Barrier Reef, linked to marine heatwave events. These changes are very likely linked to warming oceans, and primarily driven by the human influence on the climate.
Global sea level change from 1880 estimated from tide gauges and satellites. CSIRO, Author provided
Well-established scientific theory and climate model studies both show that the warming would largely not have occurred without the increase in greenhouse gas concentrations. In addition, the current increase in temperatures accords with projections made nearly 30 years ago. Warming is projected to continue into the future as the effect of past emissions continue, and more greenhouse gases are emitted. Australia is projected to experience increases in sea and air temperatures, with more hot days and marine heatwaves, and fewer cool extremes.
It takes time for the climate system to warm in response to increases in greenhouse gases, and the historical emissions over the past century have locked in some warming over the next two decades, regardless of any changes we might make to global emissions in that period. However, by the mid-21st century, higher ongoing emissions of greenhouse gases will lead to greater warming and associated impacts, and reducing emissions will lead to less warming and fewer associated impacts.
Australian average annual temperature 1861-1900 period in observations and global climate models. CSIRO, Author provided
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