Wednesday, February 26, 2014
Australia should cut emissions by 19 per cent to play fair role: Climate Change Authority report
Monday, February 17, 2014
Climate Council: heatwaves are getting hotter and more frequent
18 February 2014
Will Steffen, Adjunct Professor, Fenner School of Environment and Society at Australian National University
Lesley Hughes, Head of the Department of Biological Sciences at Macquarie University
Sarah Perkins, Post Doctoral Research Fellow at University of New South Wales
Heatwaves are one of the most important climate-related risks for Australians. Sometimes called the "silent killers", they cause the greatest number of deaths of any natural disaster type in Australia, and have significant impacts on infrastructure, agriculture and biodiversity. As the climate continues to warm, heatwaves are becoming hotter, longer and more frequent.
The extreme heat in Melbourne that frazzled the Australian Open tennis tournament and the record-breaking heat in large areas of Queensland this summer remind us of the risks that heatwaves pose. Hot on the heels of the "angry summer" of 2012/2013, this summer's heat is part of a longer-term trend towards hotter weather.
Heatwaves on the rise
The Climate Council's latest report – "Heatwaves: Hotter, Longer, More Often", which we co-authored – delivers four key findings.
First, climate change is already increasing the likelihood and severity of heatwaves across Australia. Second, heatwaves have widespread impacts including increased deaths, reduced workplace productivity, damage to infrastructure such as transport and electricity systems, mortality of heat-sensitive plants and animals, and stress on agricultural systems. Third, record hot days and heatwaves are expected to increase further in the future. And finally, limiting future increase in heatwave activity requires urgent and deep cuts to greenhouse-gas emissions.
Since 1950, the annual number of record hot days across Australia has more than doubled, and both maximum and minimum temperatures have increased by around 0.9°C. Over the past decade, the frequency of record hot days has been more than three times the frequency of record cold days. The hottest area-averaged national maximum temperature ever recorded was 40.3°C on 7 January 2013, and extreme temperature records were broken in every state and territory throughout the course of the 2012/2013 summer.
Almost all of Australia has experienced a lengthening of the heatwave season, with the first heatwave event occurringmuch earlier than it did 60 years ago. The intensity of heatwaves, as measured by the temperature of the hottest day (the peak of the heatwave), is also increasing.
This summer, Australians again endured record-breaking, extreme heatwaves and hot weather. On 3 January, Queensland experienced its hottest area-averaged day on recordand for the week ending 4 January, average maximum temperatures were a staggering 8°C or more above normal in the southern inland part of the state.
Record high maximum temperatures occurred over 8.8% of Australia during the first four days of January, including 17% of New South Wales, 17% of the Northern Territory, 16% of Queensland and 8% of South Australia. On 2 February, Adelaide reached a new February record of 44.7°C, some 15°C above average.
The global picture
Heatwaves are also on the increase worldwide, with severe heatwaves affecting many countries and regions in the last 10-15 years. One of the most severe was the European heatwave of July and August 2003, with France and Switzerland particularly affected. This heatwave was followed in 2010 by an even more intense and widespread heatwave, which scorched large swathes of Eastern Europe, including western Russia, Belarus, Estonia, Latvia, and Lithuania.
Long-term temperature reconstructions show that these were the hottest summers that Europe has experienced for at least 500 years. North America has also experienced several recent heatwaves, with a major heatwave affecting the state of Texas in July 2011 and a heatwave covering a greater area of the country in 2012.
Diverse impacts
The impacts of heatwaves are surprisingly large and diverse. The Bureau of Meteorology has dubbed heatwaves "the most under-rated weather hazard in Australia". While heatwaves do not result in obvious violent effects on the landscape, unlike many other weather-related disasters such as high-intensity storms and bushfires, their impacts on health, the workplace, infrastructure, agriculture, and the environment are serious, costly and long-lasting.
Plants and animals are also susceptible to extreme heat events, with flying foxes, birds and rainforest marsupials being particularly vulnerable. Marine heatwaves can trigger coral bleaching events, affecting large areas of reefs. Bleaching events on the Great Barrier Reef have occurred repeatedly since the late 1970s, with none reported before then. These bleaching events have contributed to the observed 50% loss of coral cover in the Great Barrier Reef over the past 30 years.
The case for decarbonisation
As greenhouse gases continue to rise in the atmosphere, heatwaves will continue to worsen.
According to the Intergovernmental Panel on Climate Change's 2012 Special Report on Extremes and last year's release of the first part of the IPCC Fifth Assessment Report, it is virtually certain that hot extremes will increase and cold extremes will decrease through the century compared to the current climate. It is also very likely that the length, frequency and/or intensity of heat waves will increase over most land areas around the globe.
This is the critical decade for action. Global emissions are still rising and Australian emissions are yet to make a decisive turn downwards. Despite the promising developments in low-carbon technologies and energy-efficiency measures, there is not yet widespread acceptance in Australia of the urgent need to decarbonise our economy and implement policies to facilitate a decarbonised future. This challenge must be met if we are to minimise the risk of worsening heatwaves and other extreme events for ourselves, our children and grandchildren. It's time to get on with the job.
The Climate Council is a crowdfunded body that advises the Australian public on climate change. You can read its Heatwave Report here.
Thursday, January 16, 2014
Australian heatwaves getting hotter and longer, says Climate Council
Council releases 1971-2008 climate findings as Adelaide and Melbourne brace for historic heat
Oliver Milman,
theguardian.com, Thursday 16 January 2014
Heatwaves in Australia are becoming more frequent, are increasing in intensity and are lasting longer, according to an interim report by the Climate Council.
The report, which will be released in full in February, finds that climate change is having a key influence on a trend that has seen the number of hot days in Australia double and the duration and frequency of heatwaves increase in the period between 1971 and 2008.
South-eastern Australia has baked in extreme temperatures this week, with Melbourne set for four consecutive days over 40C – a run not replicated since 1908. Adelaide is due to go one further and have five days over 40C, with Thursday's forecast of 46C threatening to break city's record temperature of 46.1C.
The Climate Council, a privately run group of climate scientists and economists who previously formed the government-funded Climate Commission, defines a heatwave to be at least three consecutive days at a temperature in the top 10% for that time of year.
Its interim report states there will still be record cold events but that these events are being eclipsed by record hot events by a ratio of three to one. Heatwave frequency in Australia will "increase significantly" in the future, the report warns.
"As greenhouse gases continue to accumulate in the atmosphere from the burning of fossil fuels, more heat is trapped in the lower atmosphere," the report states. "This increases the likelihood that hot weather will occur and that heatwaves will become longer and more intense.
"It is crucial that communities, emergency services, health and medical services and other authorities prepare for the increases that are already occurring in the severity and frequency of many types of extreme weather.
"The south-east of Australia, including many of our largest population centres, stands out as being at increased risk from many extreme weather events – including heatwaves."
Dr Sarah Perkins, report co-author and research fellow at the UNSW, told Guardian Australia that the current heatwave was happening during a "neutral" period of climatic variability.
Before the 2009 Black Saturday fires, there was a decade-long drought, which produced some climatic variability reasons behind it," she said.
"This year, we aren't in an El Niño, we're in a neutral pattern, so we might expect some extreme weather but not this hot scorching weather. Last year was a neutral year too, on the back of a strong La Niña, and we still got extreme weather.
"I'm not discounting natural variability, but there is still the background signal of climate change. The high-pressure system probably would've happened anyway, but climate change is exacerbating these events.
"While we can't blame climate change for any one event, we can certainly see its fingerprint. This is another link in the chain."
Perkins said her latest work had analysed heatwave trends up to 2013. She said the trend "just gets worse – it's a bit scary really".
"We are experiencing between one to three extra heatwave days a year, compared to the long term average, which doesn't sound a lot but it doesn't need many of these days to kill people or cause damage," she said.
"And this is with background warming of 1C. If current trends continue and we get to 4C warming, it will be a whole lot worse than now."
Perkins' fellow report author Will Steffen said the increase in heatwaves would have a wide range of impacts on the way Australians live.
"Heatwaves have significant impacts on our health, our infrastructure, our agriculture and our ecosystems," he said.
"It is essential that we understand the influence of climate change on heatwaves to ensure that health services, transport providers, farmers and the community are prepared for what is happening now and what will happen increasingly in the future.
"Australia has always had hot weather. However, climate change is loading the dice toward more extreme hot weather."
The Greens have cited the heatwave in an attack on Tony Abbott's climate change policies, calling for him to abandon plans to dismantle the carbon pricing system.
"The Climate Council has warned that global warming will bring more extreme weather and heatwaves and we can't pretend it's not going to happen," said the Greens senator Lee Rhiannon. "We must prepare for it and stop it getting worse by reducing greenhouse pollution.
"The clean energy laws are already reducing greenhouse pollution and creating jobs. It really is time for Tony Abbott to abandon his ideological rejection of the climate science and put the Australian community first."
The Department of Environment has been contacted for its response to the report.
Wednesday, January 15, 2014
Old-growth forests seen more valuable as carbon sinks: study
Sunday, January 12, 2014
Climate change set to give us a home without the gumtrees
Monday, January 6, 2014
Australia’s hottest year was no freak event: humans caused it
The Conversation, 6 January 2014
Sophie Lewis, Postdoctoral Research Fellow at University of Melbourne,
David Karoly, Professor of Atmospheric Science at University of Melbourne
The Bureau of Meteorology has confirmed that 2013 was the hottest year in Australia since records began in 1910.
Unusual heat was a persistent feature throughout the year. For the continent as a whole, we experienced our hottest day on record on January 7. Then January was the hottest month on record, and the 2012-13 summer was the hottest recorded for the nation.
The nation-wide temperature record set for the month of September exceeded the previous record by more than a degree. This was the largest temperature anomaly for any month yet recorded.
Averaged across all of Australia, the temperature for 2013 was 1.2C above the 1961-1990 average, and well above the previous record hot year of 2005 of 1.03C above average.
What caused these extreme temperatures? Climate scientists have a problem: because climate deals with averages and trends, we can't attribute specific records to a particular cause.
But our research has made significant headway in identifying the causes of climate events, by calculating how much various factors increase the risk of extreme climate events occurring. And we have found sobering results.
We previously analysed the role human-caused climate change played in recent extremes across Australia.
For various record-breaking 2013 Australian temperatures, we investigated the contributing factors to temperature extremes using a suite of state-of-the-art global climate models. The models simulated well the natural variability of Australian temperatures.
Using this approach, we calculated the probability of hot Australian temperatures in model experiments. These incorporated human (changes in greenhouse gases, aerosols and ozone) and natural (solar radiation changes and volcanic) factors. We compared these probabilities to those calculated for a parallel set of experiments that include only natural factors. In this way, natural and human climate influences can be separated.
In our previous studies, we then applied an approach (known as Fraction of Attributable Risk) widely used in health and population studies to quantify the contribution of a risk factor to the occurrence of a disease. Health studies, for example, can quantify how much smoking increases the risk of lung cancer.
Using the climate models, the Fraction of Attributable Risk (FAR) shows how much the risk of extreme temperatures increases thanks to human influences.
In our earlier study of our record hot Australian summer of 2012-13, we found that it was very likely (with 90% confidence) that human influences increased the odds of extreme summers such as 2012-13 by at least five times.
In August 2013, Australia broke the record for the hottest 12-month period. The odds of this occurring increased again from the hottest summer. We found that human influence increased the odds of setting this new record by at least 100 times.
Recent extreme temperatures are exceeding previous records by increasingly large margins. The chance of reaching these extreme temperatures from natural climate variations alone is becoming increasingly unlikely. When we considered the 12-month record at the end of August, it was nearly impossible for this temperature extreme to occur from natural climate variations alone in these model experiments.
We have just completed a preliminary investigation of contributing factors for the record Australian temperature in the 2013 calendar year.
In the model experiments, it is impossible to reach such a temperature record due to natural climate variations alone. In climate model simulations with only natural factors, none of the nearly 13,000 model years analysed exceed the previous hottest year recorded back in 2005.
In contrast, in model simulations including both natural and human factors, such as increasing greenhouse gases, record temperatures occur approximately once in every ten years during the period 2006 to 2020. (On a mathematical note, as there is no instance in which the record hot yearly temperature occurred without human contributions, the FAR value is one.)Our extensive catalogue of 2013 record-breaking events in Australia occurred in a global context of increasing temperatures that must be considered. Globally, 2013 will likely rank as the 6th hottest year recorded.
So to return to our question, what caused the 2013 record hot year across Australia? Simply put, our climate has changed due to human activities. Recent extremes, such as this hot year, are occurring well outside the bounds of natural climate variations alone.