The world endured 2 extra heatwave days per decade since 1950 – but the worst is yet to come



Shutterstock

Sarah Perkins-Kirkpatrick, UNSW

The term “heatwave” is no stranger to Australians. Defined as when conditions are excessively hot for at least three days in a row, these extreme temperature events have always punctuated our climate.

With many of us in the thick of winter dreaming of warmer days, it’s important to remember how damaging heatwaves can be.

In 2009, the heatwave that preceded Black Saturday killed 374 people. The economic impact on Australia’s workforce from heatwaves is US$6.2 billion a year (almost AU$9 billion). And just last summer, extreme temperature records tumbled, contributing to Australia’s unprecedented bushfire season.

What are heatwaves?

Our new study – the first worldwide assessment of heatwaves at the regional scale – found heatwaves have become longer and more frequent since 1950. And worryingly, we found this trend has accelerated.

We also examined a new metric: “cumulative heat”. This measures how much extra heat a heatwave can contribute, and the new perspective is eye-opening.

What is ‘extra heat’?

In southeast Australia’s worst heatwave season in 2009, we endured an extra heat of 80℃. Let’s explore what that means.

For a day to qualify as being part of a heatwave, a recorded temperature should exceed an officially declared “heatwave threshold”.

And cumulative heat is generally when the temperature above that threshold across all heatwave days are added up.

Let’s say, for example, a particular location had a heatwave threshold of around 30℃. The “extra heat” on a day where temperatures reach 35℃ would be 5℃. If the heatwave lasted for three days, and all days reached 35℃, then the cumulative heat for that event would be 15℃.

Another decade, another heatwave day

We found almost every global region has experienced a significant increase in heatwave frequency since 1950. For example, southern Australia has experienced, on average, one extra heatwave day per decade since 1950.




Read more:
Anatomy of a heatwave: how Antarctica recorded a 20.75°C day last month


However, other regions have experienced much more rapid increases. The Mediterranean has seen approximately 2.5 more heatwave days per decade, while the Amazon rainforest has seen an extra 5.5 more heatwave days per decade since 1950.

The global average sits at approximately two extra heatwave days per decade.

The last 20 years saw the worst heatwave seasons

Since the 1950s, almost all regions experienced significant increases in the extra heat generated by heatwaves.

Over northern and southern Australia, the excess heat from heatwaves has increased by 2-3℃ per decade. This is similar to other regions, such as western North America, the Amazon and the global average.

Alaska, Brazil and West Asia, however, have cumulative heat trends of a massive 4-5℃ per decade. And, for the vast majority of the world, the worst seasons occurred in the last 20 years.

In the heatwave before Black Saturday, 374 people died.
Shutterstock

We also examined whether heatwaves were changing at a constant rate, or were speeding up or slowing down. With the exception of average intensity, we found heatwave trends have not only increased, but have accelerated since the 1950s.

Don’t be fooled by the maths

Interestingly, average heatwave intensity showed little – if any – changes since 1950. But before we all breathe a sigh of relief, this is not because climate change has stopped, or because heatwaves aren’t getting any warmer. It’s the result of a mathematical quirk.




Read more:
Climate change: 40°C summer temperatures could be common in UK by 2100


Since we’re seeing more heatwaves – which we found are also generally getting longer – there are more days to underpin the average intensity. While all heatwave days must exceed a relative extreme threshold, some days will exceed this threshold to a lesser extent than others. This brings the overall average down.

When we look at changes in cumulative heat, however, there’s just no denying it. Extra heat – not the average – experienced in almost all regions, is what can have adverse impacts on our health, infrastructure and ecosystems.

The Amazon has endured 5.5 more heatwave days per decade since 1950.
Shutterstock

Like nothing we’ve experienced before

While the devastating impacts of heatwaves are clear, it has been difficult to consistently measure changes in heatwaves across the globe. Previous studies have assessed regional heatwave trends, but data constraints and the spectrum of different heatwave metrics available have made it hard to compare regional changes in heatwaves.

Our study has closed this gap, and clearly shows heatwaves are on the rise. We are seeing more of them and they are generating more heat at an increasing pace.




Read more:
We’ve learned a lot about heatwaves, but we’re still just warming up


While Australia may be no stranger to heatwaves in the past, those we see in the future under these accelerating trends will certainly be foreign.

For example, a 2014 study found that depending on where you are in Australia, anywhere between 15 and 50 extra heatwave days will occur by 2100 compared to the second half of the 20th century.

We can still abate those trends if we work collectively, effectively and urgently to reduce our greenhouse gas emissions.The Conversation

Sarah Perkins-Kirkpatrick, ARC Future Fellow, UNSW

This article is republished from The Conversation under a Creative Commons license. Read the original article.

The bushfires are horrendous, but expect cyclones, floods and heatwaves too



Bushfires are not the only weather and climate events set to ravage Australia in coming months.
Dave Hunt/AAP

Neville Nicholls, Monash University

Public attention on the disastrous bushfire crisis in Australia will rightly continue for weeks to come. But as we direct resources to coping and recovery, we should not forget other weather and climate challenges looming this summer.

The peak time for heatwaves in southern Australia has not yet arrived. Many parts of Australia can expect heavy rains and flooding. And northern Australia’s cyclone season is just gearing up.

The events will stretch the ability of emergency services and the broader community to cope. The best way to prepare for these events is to keep an eye on Bureau of Meteorology forecasts.

Fires and other extreme events will test emergency services this summer.
Darren Pateman/AAP

Let it rain

2019 was Australia’s driest year on record. Since early winter the Bureau of Meteorology has correctly predicted the development of these widespread dry conditions.

But relief may be coming. The latest bureau outlooks suggest more normal summer conditions from February to April. If it eventuates, this would include more rain.




Read more:
How to monitor the bushfires raging across Australia


The arrival of drought-breaking rains is notoriously hard to predict – in the past, they have come any time between January and May. Global warming is also complicating seasonal climate predictions.

We all hope the rain arrives sooner rather than later, and eases the fire situation. But rain will bring other risks.

Continental-scale droughts such as that experienced over the past few years are often broken by widespread heavy rains, leading to an increased risk of flooding including potentially lethal flash floods. The decade-long Millenium drought that ended in 2009 was followed by two extremely wet years with serious flooding.

A similar situation was seen in Indonesia in recent days when very heavy rains after a prolonged drought produced disastrous floods and landslides.

Indonesian rescuers searching for missing people after a landslide in West Java, Indonesia, triggered by heavy rain.
EPA

The flood risk is exacerbated by the bare soil and lack of vegetation caused by drought, and by bushfires that destroy forest and grassland.

Australia’s north may be particularly hard hit. The onset of the tropical wet season has been very much delayed, as the bureau predicted. Over the last three months, some parts of the Australian tropics had their lowest ever October-December rainfall. But there are some suggestions widespread rain may be on its way.

Further south, drought-breaking rains can also be heavy and widespread, leading to increased flood risk. So even when the drought breaks and rains quell the fires, there will likely still be bouts of extreme weather, and high demand for emergency services.

Cyclones and heatwaves

The tropical cyclone season has been much delayed, as predicted by the bureau, although there are now signs of cyclonic activity in the near future.

Cyclones often bring welcome rains to drought-affected communities. But we should not overlook the serious damage these systems may bring such as coastal flooding and wind damage – again requiring intervention from emergency services.




Read more:
‘I can still picture the faces’: Black Saturday firefighters want you to listen to them, not call them ‘heroes’


And we are still a month away from the riskiest time for heatwaves in southern Australia. We’ve already had some severe heatwaves this summer. However they usually peak in the middle and end of summer, so the worst may be yet to come.

Lives have undoubtedly been saved this summer by improved forecasting of high temperatures and better dissemination of heatwave information by state and local governments. But after an already devastating early summer of fires and heat, warning fatigue may set in amongst both warning providers and the public. We must ensure heatwave warnings continue to be disseminated to populations at risk, and are acted on.

Shop staff clean up storm waters after Cyclone Debbie hit iQueensland in 2017.
AAP

Be thankful for weather forecasters

The recent experience of farmers, fire fighters, water resource managers and communities illustrate the value of the service provided by the Bureau of Meteorology. Greatly improved weather and climate forecasting developed over the past few decades means communities can plan for and deal with our highly variable weather and climate far better than in the past.




Read more:
It’s only October, so what’s with all these bushfires? New research explains it


Recent drought, fires and heatwaves – exacerbated by global warming – have been devastating. But imagine if we only had the limited weather forecast capabilities of even a few decades ago, without today’s high-speed computers to run weather forecast models, and satellites to feed in enormous amounts of data. How much worse would the impacts have been?

These forecasts have allowed heat alerts to be disseminated to vulnerable communities. Detailed information on weather conducive to fire spread has helped fire agencies provide more targeted warnings and direct resources appropriately.

An air tanker makes a pass to drop fire retardant on a bushfire in North Nowra, NSW, as fires spread rapidly.
Mick Tsikas/AAP

Never before have weather forecasts been so readily available to the public. Here are ways you can use them to reduce risks to life and property during an extreme event:

  • Listen to ABC local radio for emergency updates and detailed Bureau of Meteorology forecasts
  • load your state fire service emergency app onto your phone and check it regularly. Or check out the information online, such as at the NSW Rural Fire Service’s Fires Near Me website
  • check the bureau’s website for climate and weather forecasts
  • download a short-range rainfall forecast app such as Rain Parrot onto your phone. These apps use the bureau’s radar data to make short-range forecasts of rainfall for your location, and notify you if rain is coming.

Global warming is already lengthening the fire season and making heatwaves more intense, more frequent, and longer. It is also increasing the likelihood of heavy rains, and making droughts worse.

We must keep adapting to these changing threats, and further improve our ability to forecast them. And the community must stay aware of the many weather and climate extremes that threaten lives and property.The Conversation

Neville Nicholls, Professor emeritus, School of Earth, Atmosphere and Environment, Monash University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Heatwaves and flash floods: yes, this is Britain’s ‘new normal’


Hayley J. Fowler, Newcastle University

“It’s hard to believe, isn’t it, that we had a heatwave just last week?”

Those words were spoken by a BBC news presenter, in front of graphic images of fire service rescues, as heavy rain caused floods and landslides which closed many roads and railway lines. In recent days there have dramatic floods across the north of England, particularly around Manchester, the Peak District and Yorkshire.

For me, this is personal, as I am from the worst affected area. I went to high school where people spent the night in their Civic Hall. Three miles away from where I grew up, a dam holding back Toddbrook Reservoir has been at risk of collapse and the town of Whaley Bridge was evacuated. But I’m not surprised that we are seeing flash flooding and I expect it to get worse in the future.

I am a professor at Newcastle University, where I lead a large research group focused on understanding changes to intense rainfall events and flash floods. Over the past eight years we’ve been working closely with colleagues at the UK Met Office to develop new very high-resolution climate models that can simulate these very intense summer storms and therefore predict what might happen in a warming climate.

Our models tell us that by 2080 summers in the UK will be much hotter and drier. Heatwaves will be more common. In fact a report released by the Met Office on the same day as the latest flash floods tells us that heatwaves are already happening more often. When Cambridge recently hit 38.7℃, the UK became one of 12 countries to break its national temperature record this year.

The world is warming. But although UK average summer rainfall is predicted to decrease, our models tell us that when it does rain it will be more intense than has been the case. Flash flooding in the UK is generally caused by intense rainstorms, where more than 30mm falls in an hour. Climate models predict these will happen five times more often by 2080.

Part of the reason for this is the simple fact that warmer air can hold more moisture. But that’s too simple: the availability of moisture also increases in areas close to warm oceans – warmer sea surface temperatures cause more moisture to be evaporated into the atmosphere, providing additional fuel for these intense storms. And here’s the scary bit: the Atlantic Ocean provides a vast source of moisture for storms in the UK.

But that’s not the whole story. Heavy, short rain storms are intensifying more rapidly than would be expected with global warming (what we call the Clausius-Clapeyron relationship). Research also suggests that more intense storms can themselves grow bigger, and with both the intensity of the rainfall and the spatial footprint of the storm increasing, the total rainfall in an “event” could double.

What’s more, the larger storms seem to have an ability to draw in more moisture from the surrounding area and become even more intense: the additional energy (heating) fuelling the uplift of air within the storm’s core draws in even more moisture from the surface, allowing them to grow even larger, with more potential for flooding. These also provide the perfect ingredients for large hail storms.

So, it is entirely consistent that we might expect both more heatwaves and more intense summer thunderstorms in a warmer climate. We also know which areas of the country are already susceptible to these flash floods from our analysis of historical records of flooding. Newspapers have reported on the dramatic impacts of these floods for centuries and this has allowed my team to reconstruct a flash-flooding history of the UK.

Certain parts of the country are highly vulnerable as their rivers respond quickly to rainstorms. These rivers tend to be found in steep, upland catchments underlain by non-permeable rocks, mainly in the north and west of the UK. High-risk catchments also include urban areas where the ground is also non-permeable, for entirely different reasons.

Many of the towns reported to have suffered “biblical” flooding recently have suffered repeated flooding through history, but perhaps not within living memory. For example, Whaley Bridge is mentioned twice in the flood chronologies for events in June 1872 and July 1881:

On 19th [June 1872] the Goyt was 12 to 14 feet above its normal level. At Whaley Bridge houses near the river were completely flooded and people were taken into the chapel and inns … in Macclesfield a woman and child were drowned when the river Bollin overflowed. Two reservoirs burst in the vicinity.

This rich archive of knowledge, including the prevalence of flooding in certain towns, even specific roads, is something we should draw upon in planning both the emergency response to these flash floods and for reducing their future impact. We can learn a lot from the past in how to manage the greater risks of flooding the future will bring.The Conversation

Hayley J. Fowler, Professor of Climate Change Impacts, Newcastle University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Suffering in the heat: the rise in marine heatwaves is harming ocean species



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Recent marine heatwaves have devastated crucial coastal habitats, including kelp forests, seagrass meadows and coral reefs.
Dan Smale, Author provided

Dan Smale, Marine Biological Association and Thomas Wernberg, University of Western Australia

In the midst of a raging heatwave, most people think of the ocean as a nice place to cool down. But heatwaves can strike in the ocean as well as on land. And when they do, marine organisms of all kinds – plankton, seaweed, corals, snails, fish, birds and mammals – also feel the wrath of soaring temperatures.

Our new research, published today in Nature Climate Change, makes abundantly clear the destructive force of marine heatwaves. We compared the effects on ecosystems of eight marine heatwaves from around the world, including four El Niño events (1982-83, 1986-87, 1991-92, 1997-98), three extreme heat events in the Mediterranean Sea (1999, 2003, 2006) and one in Western Australia in 2011. We found that these events can significantly damage the health of corals, kelps and seagrasses.

This is concerning, because these species form the foundation of many ecosystems, from the tropics to polar waters. Thousands of other species – not to mention a wealth of human activities – depend on them.

We identified southeastern Australia, southeast Asia, northwestern Africa, Europe and eastern Canada as the places where marine species are most at risk of extreme heat in the future.




Read more:
Marine heatwaves are getting hotter, lasting longer and doing more damage


Marine heatwaves are defined as periods of five days or more during which ocean temperatures are unusually high, compared with the long-term average for any given place. Just like their counterparts on land, marine heatwaves have been getting more frequent, hotter and longer in recent decades. Globally, there were 54% more heatwave days per year between 1987 and 2016 than in 1925–54.

Although the heatwaves we studied varied widely in their maximum intensity and duration, we found that all of them had negative impacts on a broad range of different types of marine species.

Marine heatwaves in tropical regions have caused widespread coral bleaching.

Humans also depend on these species, either directly or indirectly, because they underpin a wealth of ecological goods and services. For example, many marine ecosystems support commercial and recreational fisheries, contribute to carbon storage and nutrient cycling, offer venues for tourism and recreation, or are culturally or scientifically significant.




Read more:
Australia’s ‘other’ reef is worth more than $10 billion a year – but have you heard of it?


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Marine heatwaves have had negative impacts on virtually all these “ecosystem services”. For example, seagrass meadows in the Mediterranean Sea, which store significant amounts of carbon, are harmed by extreme temperatures recorded during marine heatwaves. In the summers of both 2003 and 2006, marine heatwaves led to widespread seagrass deaths.




Read more:
Seagrass, protector of shipwrecks and buried treasure


The marine heatwaves off the west coast of Australia in 2011 and northeast America in 2012 led to dramatic changes in the regionally important abalone and lobster fisheries, respectively. Several marine heatwaves associated with El Niño events caused widespread coral bleaching with consequences for biodiversity, fisheries, coastal erosion and tourism.

Mass die-offs of finfish and shellfish have been recorded during marine heatwaves, with major consequences for regional fishing industries.

All evidence suggests that marine heatwaves are linked to human mediated climate change and will continue to intensify with ongoing global warming. The impacts can only be minimised by combining rapid, meaningful reductions in greenhouse emissions with a more adaptable and pragmatic approach to the management of marine ecosystems.The Conversation

Dan Smale, Research Fellow in Marine Ecology, Marine Biological Association and Thomas Wernberg, Associate professor, University of Western Australia

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Heatwaves threaten Australians’ health, and our politicians aren’t doing enough about it


Paul Beggs, Macquarie University; Helen Louise Berry, University of Sydney; Martina Linnenluecke, Macquarie University, and Ying Zhang, University of Sydney

Extreme heat affects the mental health of Australians to the same degree as unemployment, yet Australia’s policy action on climate change lags behind other high-income countries such as Germany and the United Kingdom.

As Australia approaches another summer, we face the inevitability of deadly heatwaves. Our report published today in the Medical Journal of Australia concludes that policy inaction, particularly at the federal level, is putting Australian lives at risk.

The report, The MJA–Lancet Countdown on health and climate change: Australian policy inaction threatens lives, builds on an earlier publication in The Lancet medical journal, which concluded climate change is the biggest global health threat of the 21st century.




Read more:
Climate mitigation – the greatest public health opportunity of our time


Australia is the first to prepare its own country-level report. Developed in partnership with the Lancet Countdown – which tracks the global connections between health and climate change – it adopts the structure and methods of the global assessment but with an Australian focus.

How Australians’ health suffers

Australians are already facing climate change-related exposures that come from increasing annual average temperatures, heatwaves and weather-related disasters. Australian deaths during the 2014 Adelaide heatwave and Melbourne’s 2016 thunderstorm asthma event are examples of the risk climate poses to our health.




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Keeping one step ahead of pollen triggers for thunderstorm asthma


Our report was produced by a team of 19 experts from 13 universities and research institutes. We aimed to answer what we know about climate change and human health in Australia and how we are responding to this threat, if at all.

To do this, our team examined more than 40 indicators that enable us to track progress on the broad and complex climate change and human health issue. Health impact indicators included the health effects of temperature change and heatwaves, change in labour capacity, trends in climate-sensitive diseases, lethality of weather-related disasters and food insecurity and malnutrition.

We also developed an indicator for the impacts of climate change on mental health. This involved examining the association between mean annual maximum temperatures and suicide rates for all states and territories over the last ten years.

We found that, in most jurisdictions, the suicide rate increased with increasing maximum temperature. In Australia’s changing climate, we urgently need to seek ways to break the link between extreme temperature and suicide.

Across other indicators, we found workers’ compensation claims in Adelaide increased by 6.2% during heatwaves, mainly among outdoor male workers and tradespeople over 55 years.

And we found the length of heatwaves increased in 2016 and 2017 in Australia’s three largest cities – Sydney, Melbourne and Brisbane. Heatwave length varied from year to year, but between 2000 and 2017, the mean number of heatwave days increased by more than two days across the country.

Policy action we need

Australia’s slow transition to renewables and low-carbon electricity generation is problematic, and not only from a climate change perspective. Our report shows that pollutants from fossil fuel combustion cause thousands of premature deaths nationwide every year. We argue even one premature death is one too many when there is so much that we can do to address this.

Australia is one of the world’s wealthiest countries with the resources and technical expertise to act on climate change and health. Yet Australia’s carbon intensity is the highest among the countries we included in our comparison – Germany, United States, China, India and Brazil.

A carbon-intensive energy system is one of the main drivers behind climate change. Australia was once a leader in the uptake of renewables but other nations have since streaked ahead and are reaping the benefits for their economies, energy security and health.

Despite some progress increasing renewable generation, it’s time we truly pull our weight in the global effort to prevent acceleration towards dangerous climate change.

Policy leaders must take steps to protect human health and lives. These include strong political and financial commitments to accelerate transition to renewables and low-carbon electricity generation. The government lacks detailed planning for a clean future with a secure energy supply.




Read more:
What would a fair energy transition look like?


Our MJA-Lancet Countdown report will be updated annually. Now that Australia has begun systematically tracking the effects of climate change on health – and given its poor performance compared with comparable economies globally – further inaction would be reckless.The Conversation

Paul Beggs, Associate Professor and Environmental Health Scientist, Macquarie University; Helen Louise Berry, Professor of Climate Change and Mental Health, University of Sydney; Martina Linnenluecke, Professor of Environmental Finance; Director of the Centre for Corporate Sustainability and Environmental Finance, Macquarie University, and Ying Zhang, Associate Director, Teaching and Learning, Sydney School of Public Health, University of Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Melbourne and Adelaide have been Australia’s most vulnerable major cities to killer heatwaves


Thomas Longden, University of Technology Sydney

Melbourne and Adelaide have been most prone to deadly heatwave conditions among Australia’s five largest cities, according to my new research published in Climatic Change.

My study shows that between 2001 and 2015, Melbourne and Adelaide suffered the most exposure to temperatures beyond a crucial threshold of 7.26℃ above the average. Above this threshold, deaths are more likely because people are not acclimatised to the extreme weather.

I estimated that there were 151 deaths in Melbourne and 144 in Adelaide due to extreme heatwaves – those above this 7.26℃ threshold – between 2001 and 2015.

Heatwaves can cause significant numbers of deaths, especially among vulnerable groups of people who are not prepared for or acclimatised to extreme hot temperatures.

Even though Melbourne and Adelaide are located in more temperate areas (in comparison with more northerly cities such as Brisbane), they have been periodically hit by severe heatwaves.




Read more:
We’ve learned a lot about heatwaves, but we’re still just warming up


In my research, I looked at the “Excess Heat Factor”, a measure used by the Bureau of Meteorology as part of its heatwave forecasts. It is the difference between the 3-day average temperature and the 30-day average, and is therefore a measure of how “unusually hot” it is during a heatwave. It captures how much residents are likely to struggle to cope with the heat.

The graphs below show the frequency of excessively hot or cold weather for each of Australia’s major cities from 2001 to 2015. These charts show that most days had temperatures where the 3-day average was 2℃ higher or lower than the 30-day average.

A grey dashed line shows the extreme heat threshold that my study found was associated with higher deaths, relative to moderately warm and cool days.
I then estimated the threshold at which there is a significantly increased risk of deaths.

The death rate (per 100,000 people) that coincides with the extreme heat acclimatisation measure is shown as a black line on each of the graphs. This is an average impact of temperature on death rates, adjusted for different cities’ population sizes and baseline death rates.

Between 2001 and 2015, most of the events above the 7.26℃ extreme heat threshold occurred in Adelaide, Melbourne and Perth. Brisbane and Sydney had fewer days above this threshold.

Figure 1 – Histograms of the Excess Heat Index for major Australian cities between 2001 and 2015.

The importance of acclimatisation

Several previous studies have linked excessive heat to adverse events such as deaths (see here, here and here), and emergency department visits and ambulance call-outs (see here, here and here). But my study is the first to solely focus on the extreme heat index acclimatisation measure, and to identify a temperature threshold in this way. This measure is important, as it identifies the times when residents of cities with different background climates begin to struggle with the heat.

The Bureau of Meteorology does not currently use the 7.26℃ threshold identified in my paper. Doing so may improve predictions of which heatwaves are most likely to turn deadly for significant numbers of people living in our major cities.

Implications for policy

Since the severe heatwaves of 2009, many states and territories have implemented or revised their heatwave response plans, or conducted awareness campaigns to educate people about the health risks. But more can be done to make vulnerable people aware of upcoming heatwave events.

A 2016 review proposed that heatwave response plans and early warning systems should be evaluated and updated at least every five years, to ensure that they remain effective, and to incorporate up-to-date knowledge about population-level vulnerability to heat stress.

While my research has focused on Australia’s five largest cities, this does not mean that extreme heat is any less dangerous in other areas. Nor is the danger limited to prolonged heatwaves – individual hot days can catch people out too. A NSW study found that emergency hospital admissions due to dehydration and other heat-related injuries rose significantly on individual hot days, as well as during hot spells lasting at least three days.

This suggests that we need to develop more complex heat risk management plans, with targeted responses for different health issues based on the longevity of extreme heat events.

Implications for the future

We also need to consider the patterns of extremely hot temperatures that we are likely to encounter in the future. Recent research found that changes in the frequency and duration of heatwaves will be larger in the north of Australia than the south. But the same study also found that “heatwave amplitude” – the intensity of the hottest day of the hottest heatwave – will increase more in southern parts of Australia.

The ConversationThis research suggests that cities south of Brisbane will experience the most severe temperature spikes beyond what their residents are used to dealing with.

Thomas Longden, Senior Research Fellow, University of Technology Sydney

This article was originally published on The Conversation. Read the original article.

It’s a savage summer in the Northern Hemisphere – and climate change is slashing the odds of more heatwaves


Andrew King, University of Melbourne and Ben Henley, University of Melbourne

In Australia we know about sweltering summer heat. We all remember the images of burned koala paws, collapsing tennis players and, far more seriously, the tragic events of Black Saturday.

Aussies may scoff at Britain’s idea of a heatwave, but this time it’s the real deal and it’s no laughing matter.

Extreme heat has hit locations throughout the Northern Hemisphere, in places as far apart as Montreal, Glasgow, Tokyo and Lapland. In the past few weeks heat records have tumbled in a wide range of places, most notably:




Read more:
Why hot weather records continue to tumble worldwide


Heat has not been the only problem. Much of northern Europe is experiencing a very persistent drought, with little to no measurable rainfall in months. This has caused the normally lush green fields of England and other European countries to turn brown and even reveal previously hidden archaeological monuments.

There have also been major wildfires in northern England, Sweden and, most recently and devastatingly, Greece. The Greek wildfires came off the back of a very dry winter and spring.

What’s behind the widespread extreme heat?

The jet stream, a high-altitude band of air that pushes weather systems around at lower altitudes, has been weaker than normal. It has also been positioned unusually far to the north, particularly over Europe. This has kept the low-pressure systems that often drive wind and rain over northern Europe at bay.

The jet stream has remained locked in roughly the same position over the Atlantic Ocean and northern Europe for the past couple of months. This has meant that the same weather types have remained over the same locations most of the time.

Weather is typically more transient than it has been recently. Even when we do have blocking high-pressure systems associated with high temperatures in northern Europe, they don’t normally linger as long as this.

Is it driven by climate change?

Although climatologists have made great strides in recent years in the field of event attribution – identifying the human climate fingerprint on particular extreme weather events – it is hard to quantify the role of climate change in an event that is still unfolding.

Until the final numbers are in we won’t be able to tell just how much climate change has altered the likelihood or intensity of these particular heat extremes.

Having said that, we can use past analyses of extreme heat events, together with future climate change projections, to infer whether climate change is playing a role in these events.

We also know that increasing numbers of hot temperature records are being set, and that the increased probability of hot temperature records can indeed be attributed to the human influence on the climate.

In Europe especially, there is already a large body of literature that has looked at the role of human-caused climate change in heat extremes. In fact, the very first event attribution study, led by Peter Stott from the UK Met Office, found that human-caused climate change had at least doubled the likelihood of the infamous European heatwave of 2003.

For all manner of heat extremes in Europe and elsewhere, including in Japan, a clear and discernible link with climate change has been made.

Research has also shown that heat extremes similar to those witnessed over the past month or two are expected to become more common as global temperatures continue to climb. The world has so far had around 1℃ of global warming above pre-industrial levels, but at the global warming limits proposed in the Paris climate agreement, hot summers like that of 2003 in central Europe would be a common occurrence.

At 2℃ of global warming, the higher of the two Paris targets, 2003-like hot summers would very likely happen in most years.

Similarly, we know that heat exposure and heat-induced deaths in Europe will increase with global warming, even if we can limit this warming to the levels agreed in Paris.




Read more:
Yes, the Arctic’s freakishly warm winter is due to humans’ climate influence


But summers have always been hot, haven’t they?

For most parts of the world summers have got warmer, and the hottest summer on record is relatively recent – such as 2003 in parts of central Europe and 2010 in much of eastern Europe. One exception is central England, where the hottest summer remains 1976, although it may be challenged this year.

While extreme hot summers and heatwaves did happen in the past, they were less common. One big difference as far as England is concerned is that its extreme 1976 heatwave was a global outlier, whereas this year’s isn’t.

In 1976 northwestern Europe had higher temperature anomalies than almost anywhere else on the globe. In June 2018 the same region was unusually warm, but so was most of the rest of the Northern Hemisphere.

The ConversationSo while the persistent weather patterns are driving much of the extreme heat we’re seeing across the Northern Hemisphere, we know that human-caused climate change is nudging the temperatures up and increasing the odds of new heat extremes.

Andrew King, ARC DECRA fellow, University of Melbourne and Ben Henley, Research Fellow in Climate and Water Resources, University of Melbourne

This article was originally published on The Conversation. Read the original article.

Full response from the Climate Council for an article on heatwaves and hot days in Australia



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Climate Council CEO Amanda McKenzie, speaking on Q&A.
Q&A

Lucinda Beaman, The Conversation and Michael Courts, The Conversation

In relation to this article responding to Climate Council CEO Amanda McKenzie’s claim that heatwaves are “worsening” and “hot days” have doubled in Australia in the last 50 years, a spokesperson for the Climate Council gave the following responses. Questions from The Conversation are in bold.

Could you please provide a source, or sources, to support Ms McKenzie’s statement that heatwaves are “worsening” and hot days have doubled in the last 50 years?

Climate change is making hot days and heatwaves more frequent and more severe. Since 1950 the annual number of record hot days across Australia has more than doubled and the mean temperature has increased by about 1°C from 1910.

Specifically, there has been an increase of 0.2 days/year since 1957 which means, on average, that there are almost 12 more days per year over 35°C.

What did Ms McKenzie mean by the terms “heatwaves” and “hot days”?

Hot days – the number of hot days, defined as days with maximum temperatures greater than 35°C.

Heatwaves – three days or more of high maximum and minimum temperatures that is unusual for that location.

Furthermore, heatwaves have several significant characteristics. These include (i) frequency characteristics, such as the number of heatwave days and the annual number of summer heatwave events; (ii) duration characteristics, such as the length of the longest heatwave in a season; (iii) intensity characteristics, such as the average excess temperature expected during a heatwave and the hottest day of a heatwave; and (iv) timing characteristics, including the occurrence of the first heatwave event in a season.

Is there any other comment you would like us to include in the article?

Climate change – driven largely by rising atmospheric carbon dioxide concentrations from the burning of coal, oil and gas – is increasing temperatures and cranking up the intensity of extreme weather events globally and in Australia.

The accumulating energy in the atmosphere is affecting all extreme weather events. Climate change is driving global warming at a rate 170 times faster than the baseline rate over the past 7,000 years.

Temperature records tumbled yet again during Australia’s ‘Angry Summer’ of 2016/17. In just 90 days, more than 205 records were broken around Australia.

Heatwaves and hot days scorched the major population centres of Adelaide, Brisbane, Canberra, Melbourne and Sydney, as well as the rural and regional heartlands of eastern Australia. The most severe heatwave of this Angry Summer began around January 31 and continued until February 12, with the highest temperatures recorded from February 9-12.

This heatwave was made twice as likely to occur because of climate change, while the extreme heat in New South Wales over the entire summer season was at least 50 times as likely to occur because of climate change.

The severe heatwave of February 2017 that spread across much of Australia’s south, east and interior caused issues for the South Australian and New South Wales energy systems. In New South Wales around 3,000MW of coal and gas capacity was not available when needed in the heatwave (roughly the equivalent of two Hazelwood Power Stations).

In South Australia, 40,000 people were left without power for about half an hour in the early evening while temperatures were over 40°C. This heatwave highlights the vulnerability of our energy systems to extreme weather.

The ConversationRead the article here.

Lucinda Beaman, FactCheck Editor, The Conversation and Michael Courts, Editor, The Conversation

This article was originally published on The Conversation. Read the original article.

Are heatwaves ‘worsening’ and have ‘hot days’ doubled in Australia in the last 50 years?


Andrew King, University of Melbourne

The release of the Finkel report has refocused national attention on climate change, and how we know it’s happening.

On a Q&A episode following the report’s release, Climate Council CEO Amanda McKenzie said we’ve seen:

… worsening heatwaves, hot days doubling in Australia in the last 50 years.

Excerpt from Q&A, June 12, 2017. Quote begins at 2:12.

Her comment provides the perfect opportunity to revisit exactly what the research says on heatwaves and hot days as Australia’s climate warms.

Examining the evidence

When asked for sources to support McKenzie’s assertion, a Climate Council spokesperson said:

Climate change is making hot days and heatwaves more frequent and more severe. Since 1950 the annual number of record hot days across Australia has more than doubled and the mean temperature has increased by about 1°C from 1910.

Specifically, there has been an increase of 0.2 days/year since 1957 which means, on average, that there are almost 12 more days per year over 35°C.

You can read full response from the Climate Council here.

How do we define ‘heatwaves’?

Internationally, organisations use different definitions for
heatwaves.

In Australia, the most commonly used definition (and the one used by the Climate Council) is from the Bureau of Meteorology (BOM). It provided the first national definition of a heatwave in January 2014, describing it as:

A period of at least three days where the combined effect of excess heat and heat stress is unusual with respect to the local climate. Both maximum and minimum temperatures are used in this assessment.

The BOM uses a metric called the “excess heat factor” to decide what heat is “unusual”. It combines the average temperature over three days with the average temperature for a given location and time of year; and how the three day average temperature compares to temperatures over the last 30 days.

We can also characterise heatwaves by looking at their their intensity, frequency and duration.

Researchers, including Australian climate scientist Dr Sarah Perkins-Kirkpatrick, are trying to standardise the definitions of “heatwaves” and “hot days” and create a framework that allows for more in-depth studies of these events.

Are heatwaves ‘worsening’?

There’s not a large body of research against which to test this claim. But the research we do have suggests there has been an observable increase in the frequency and intensity of heatwaves in Australia. Research published in 2013 found a trend towards more heat waves in Australia between 1951 and 2008.

A review paper published in 2016 assessed evidence from multiple studies and found that heatwaves are becoming more intense and more frequent for the majority of Australia.

The following chart shows heatwave days per decade from 1950 to 2013, highlighting a trend toward more heatwave days in Australia over time:

We’ve seen a trend towards more heatwave days over Australia. Trends are shown for 1950-2013 in units of heatwave days per decade. Stippling indicates statistical significance at the 5% level.
Adapted from Perkins-Kirkpatrick et al. (2017)

Have hot days ‘doubled’ in the last 50 years?

While the number of “hot days” (as defined by the BOM) has not doubled over the last 50 years, as McKenzie said, the number of “record hot days” certainly has. “Record hot days” are days when the maximum temperature sets a new record high.

Given that McKenzie made her statement on a fast paced live TV show, it’s reasonable to assume she was referring to the latter. Let’s look at both figures.

The BOM defines “hot days” as days with a maximum temperature higher than 35°C. The BOM data show there were more hot days in Australia in 2013, 2014, 2015 and 2016 than in any of the 50 years from 1966 to 2016 (the last year for which data are available).

In fact, there were more hot days in the years 2013-2016 than in any other year as far back as 1910. If we compare the decades 1966-76 and 2006-16, we see a 27% increase in the number of hot days.

https://datawrapper.dwcdn.net/wsR9Z/1/

The following map shows the trend in the number of days per year above 35 °C from 1957–2015:


Bureau of Meteorology

A 2010 Bureau of Meteorology/CSIRO report found record hot days had more than doubled between 1960 and 2010. That data was collected from the highest-quality weather stations across Australia.

Number of record hot day maximums at Australian climate reference stations, 1960-2010.
Bureau of Meteorology 2010
Number of days in 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 1910-2015.
Bureau of Meteorology

Why are heatwaves worsening, and record hot days doubling?

The trend in rising average temperatures in Australia in the second half of the 20th century is likely to have been largely caused by human-induced climate change.

Recent record hot summers and significant heatwaves were also made much more likely by humans’ effect on the climate.

The ConversationThe human influence on Australian summer temperatures has increased and we can expect more frequent hot summers and heatwaves as the Earth continues to warm.

Andrew King, Climate Extremes Research Fellow, University of Melbourne

This article was originally published on The Conversation. Read the original article.

Severe heatwaves show the need to adapt livestock management for climate



Image 20170227 27378 u8yry6
Cows don’t do well in the heat.
Shutterstock

Elisabeth Vogel, University of Melbourne; Christin Meyer, Potsdam Institute for Climate Impact Research, and Richard Eckard, University of Melbourne

Climate change and extreme weather events are already impacting our food, from meat and vegetables, right through to wine. In our series on the Climate and Food, we’re looking at what this means for the food chain. The Conversation


During the recent heatwave in New South Wales, which saw record-breaking temperatures for two days in a row, 40 dairy cows died in Shoalhaven, a city just south of Sydney.

Climate change doubled the likelihood of this kind of record-breaking heatwave. And even the higher minimum temperatures we’ve recently experienced may soon be the “new normal” for this time of the year.

Farmers that already find it difficult to make a profit will need to adapt to these changing conditions, ensuring they mitigate the effects on their livestock. This could take the form of more shade and shelter, but also the selection of different breeds to suit the conditions.

What’s happening?

Cattle are vulnerable to changes in rainfall patterns (variability and extremes), temperature (average and extremes), humidity, and evaporation. These climactic changes can affect livestock directly, and also indirectly through pasture growth, forage crop quantity and quality, the production and price of feed-grain as well as spatial changes in disease and pest distribution.

The greatest risks stem from extreme events such as heatwaves and droughts, as they are less predictable and much more difficult to adapt to than gradual changes.

Dairy cows are particularly affected by heatwaves, which can not only reduce milk production, but, as the NSW heatwave illustrated, cause illness or death. Further, the effects on milk production and the protein content of the milk can last for several weeks.

Similar to humans, instances of high relative air humidity and little wind worsen the negative effects of high temperatures on livestock. When this occurs, the animals cannot easily offload excess heat through transpiration. This is compounded when there is little or no cloud cover, as the cattle are exposed to more solar radiation.

Milk production is also impacted by night-time temperatures and the timing of the heatwave. When night-time temperatures are high, cows cannot offload excess heat. If a heatwave occurs after the cows’ peak of lactation, milk production is less likely to recover and the impact is even worse.

The response of cattle to heat stress also depends on the breed. This can differ as a result of, among other things, differences in metabolic rate, sweating rate, coat texture and colour. Researchers have even identified a “slick hair gene”, responsible for producing cattle with shorter, slicker hair that reduces their vulnerability to direct radiative heat. The full benefits of the slick gene still require more research as a strategy for animals to cope in future climates.

Sheep are generally less affected by high temperatures than dairy cows. However, heatwaves with temperatures beyond 40℃ can cause heat stress. Hot days may have short-term impacts on rams’ fertility, and recently shorn sheep are at risk of sunburn if they are exposed to direct sunlight.

Factors that are unique to each individual animal, such as previous heat exposure and overall health and age, also play a role in how vulnerable they are to heat.

Mitigation

In the short run, farmers can mitigate the worst of these issues by providing high-quality water and shade (such as from trees, buildings, and shade cloth) in the heat, warm shelter in the cold, and by adjusting feed. During heatwaves, farmers can also adjust milking procedures and milk their cows very early in the morning or late at night. To provide immediate cooling they can also use sprinklers or misting systems. But care is needed to avoid simply increasing humidity around the animals.

Mitigation can be as simple as providing a bit of shade.
Shutterstock

A more long-term option is to selectively choose breeds that are better adapted to higher temperatures (such as breeds with lighter coat colour or Bos indicus types or crosses). Unfortunately, breeds adapted to warmer climates, such as the Brahman, tend not to be high milk producers or to do as well in feedlots as the traditional British beef breeds, so there will be a hit to productivity.

As the impact of climate change isn’t solely on the animals themselves, farmers will also have to adjust their work patterns and other aspects of their operations. To cope with heat, farmers themselves may need to consider working more during the cooler hours of the day. Farming both crops and livestock together can also provide a buffer against the impact of an extreme event. The combined production of wheat and wool is a typical example of spreading of risk on farm.

But for these strategies to really be effective, farmers need more information.

This includes accurate and timely forecasts of weather (temperature, rainfall, solar radiation) and heat (such as the temperature humidity index, THI) at daily, weekly and seasonal scales. Armed with this data, farmers and livestock managers can effectively plan and implement protection measures ahead of time.

A wide range of agricultural, climate and weather services exist. For example, the Bureau of Meteorology weather forecasts, seasonal outlooks of rainfall and temperature, and the current water balance and soil moisture information. There’s also the the Cool Cows website, the Dairy Forecast Service and the Cattle heat load toolbox.

We also need more research into improving our understanding of the climate system, to develop risk management plans for industries by regions, and more accurate and reliable forecasts, so that farmers and livestock managers can make management decisions and ensure the wellbeing of themselves and their animals.

Elisabeth Vogel, PhD Student, University of Melbourne; Christin Meyer, PhD student, Potsdam Institute for Climate Impact Research, and Richard Eckard, Professor & Director, Primary Industries Climate Challenges Centre, University of Melbourne

This article was originally published on The Conversation. Read the original article.