extremes of heat
Over the past seven decades, heatwaves have become more frequent and have been lasting longer across much of the planet, including Australia, over the past and the trend is accelerating as the world warms. Cumulative heat has been increasing globally on average by 1-4.5 degrees each decade but in some places, like the Middle East, and parts of Africa and South America, the trend is up to 10 degrees a decade.
And looking forward, it is projected that as much as one-third of the world's population will be exposed to Sahara Desert-like heat within half a century if greenhouse gas emissions continue to rise at the pace of recent years, meaning that as many as 3.5 billion people will be exposed to "near-unliveable" temperatures averaging 29 degrees through the year by 2070, whereas less than 1 per cent of the Earth's surface now endures such heat.
That heat compares with the narrow 11- to 15-degree range that has supported civilisation over the past six millennia. Among the most exposed will be India, Nigeria and in Australia, areas of Western Australia and the Northern Territory that are home to about 200,000 people. The general trend over the past century is encapsulated below.
Compared with pre-industrial-era conditions, temperatures globally will be about 3 degrees hotter by 2070, but since land warms faster than the oceans, the rise for people on average will be about 7.5 degrees.
Look at what has happened in recent years.
In 2016 carbon dioxide levels rose globally by a record rate of more than 3 ppm raising temperatures from pre-industrial levels to beyond 1.5 degrees and 1.35 degrees above the norm for the 1951-1980 period[1].
March 2016 was the hottest on record globally with a 0.63 degree departure from the norm for the 1981-2010 period and Sydney, Australia posted its hottest April day on record. This continued into 2017 with a succession of heat waves moving from west to east across the continent in the first three months of the year, followed by weeks of incessant rain.
2018 was Australia's third warmest year on record.
"And, then,"the sun came out".[2] By month’s end, much of Australia was baking under torrid temperatures. Marble Bar in Western Australia reached 49.3 degrees - the third-highest December temperature recorded anywhere in the country.
These record-breaking events are outlined in the Bureau of Meteorology’s 2018 climate statement, which confirmed the nation experienced its third-warmest year on record in 2018. The bureau attributed the year of meteorological extremes to both climate change and natural variability. The national mean temperature in 2018 was 1.14 degrees above average. Nine of the 10 warmest years on record have occurred since 2005. 2013 was then Australia's hottest year on record, followed by 2005 and 2018. [3] And all these have since been eclipsed by 2019!
Look at what has happened in recent years.
In 2016 carbon dioxide levels rose globally by a record rate of more than 3 ppm raising temperatures from pre-industrial levels to beyond 1.5 degrees and 1.35 degrees above the norm for the 1951-1980 period[1].
March 2016 was the hottest on record globally with a 0.63 degree departure from the norm for the 1981-2010 period and Sydney, Australia posted its hottest April day on record. This continued into 2017 with a succession of heat waves moving from west to east across the continent in the first three months of the year, followed by weeks of incessant rain.
2018 was Australia's third warmest year on record.
- In early December 2018, Cyclone Owen unloaded 678 millimetres of rain in one day on the tiny North Queensland town of Halifax. It was a new December daily rainfall record.
- By mid-December, a month's worth of rain fell in parts of Victoria in 24 hours.
- On December 20 it was Sydney’s turn when a monster thunderstorm dropped giant hail stones - some the size of cricket balls. The insurance bill is nearing $675 million.
"And, then,"the sun came out".[2] By month’s end, much of Australia was baking under torrid temperatures. Marble Bar in Western Australia reached 49.3 degrees - the third-highest December temperature recorded anywhere in the country.
These record-breaking events are outlined in the Bureau of Meteorology’s 2018 climate statement, which confirmed the nation experienced its third-warmest year on record in 2018. The bureau attributed the year of meteorological extremes to both climate change and natural variability. The national mean temperature in 2018 was 1.14 degrees above average. Nine of the 10 warmest years on record have occurred since 2005. 2013 was then Australia's hottest year on record, followed by 2005 and 2018. [3] And all these have since been eclipsed by 2019!
Ruminating upon 2018, the BOM's senior climatologist, Lynette Bettio, said that every state and territory experienced above-average day and night temperatures that year: “The average maximum temperature for the country as a whole was particularly warm, sitting 1.55 degrees above the 1961–1990 average, making 2018 Australia's second warmest year on record for daily high temperatures.” Also:
In other significant weather events that year:
The bureau also noted that:
In July 2019, three studies published in Nature and Nature Geoscience utilising extensive historical data show there has never been a period in the last 2,000 years when temperature changes have been as fast and extensive as in recent decades.
What the research also shows is that other "peak warming and cooling events" over the past two millennia appear to have been localised, whereas the human-caused global warming observed over the past 150 years is unparalleled in its global scale (not to mention its absolute temperatures).
The scientific consensus that humans are causing global warming is likely to have passed 99%, according to the lead author of the most authoritative of these studies, and could rise even further after separate research that clears up some of the remaining doubts.[4]
Meanwhile, warming temperatures not only threaten lives directly, they also cause billions of hours of lost labour, enhance conditions for the spread of infectious diseases and reduce crop yields, threatening food security.[5] Between December 2018 and January 2019, there occurred three major fish kills near Menindee in NSW involving the collective death of thousands of fish. These were attributed to blue-green algal blooms amid stagnant water flows and heatwaves, the former being the product of insufficient environmental water upstream to maintain the basic health of the river in dry times, largely the result of water being withdrawn from the river for irrigation purposes. [6]
And globally over the past decade?
Globally, 2010 to 2019 was the hottest decade since record keeping began 140 years ago. A joint analysis by NASA and NOAA (the National Oceanic and Atmospheric Administration) has revealed that 2019 was the second hottest year ever recorded, trailing only 2016, and that ocean temperatures were the highest they’ve ever been:
One clear driver
Behind all of the change is one clear driver: atmospheric carbon dioxide. In 2009, atmospheric CO2 concentrations hovered around 390 parts per million. By 2014, the number blew past 400 parts per million. Today, we hover around 410 ppm. The planet hasn’t seen concentrations that high since at least 2.6 million years ago. And at that time, no ice sheet existed in the northern polar regions and forests grew on Antarctica, sea levels were likely more than 40 feet higher than today, and the planet as a whole operated under very different conditions.
And the cause?
The underlying force beneath the changes is indisputable. Steadily increasing greenhouse gas concentrations in the atmosphere, caused primarily by humans burning fossil fuels, are trapping extra heat near Earth’s surface. That warms Earth as a whole. The outcome is both straightforward—a hotter planet—and incredibly complex, as changes cascade through the oceans, atmosphere, soil, rocks, trees, and every living thing on the planet.
"Climate change is here, it’s happening now, and it could very easily get much, much worse".
What is the solution?
Under the Paris climate accord, Australia has vowed to reduce greenhouse emissions, based on 2005 levels, by 26 per cent before 2030. Most recently, figures released by the Department of Environment and Energy in December 2018 showed that on current trends Australia will reduce emissions by just 7 per cent on 2005 levels by 2030, "a massive 19 percentage points or two thirds of the way short of the Paris agreement".
A major report prepared by the United Nations body for climate change, the Intergovernmental Panel on Climate Change, in October that year said coal-generated electricity must be phased out globally by 2050 if the world is to avoid the most catastrophic impacts of global warming, including the total destruction of the Great Barrier Reef.
It said radical, swift efforts must be taken to curb greenhouse gas pollution and keep the global temperature increase below the critical 1.5 degree threshold.
[1] “True shocker’: February spike in global temperatures stuns scientists”, SMH, 14 March 2016.
[2] However, in 1896, Bourke, NSW, was recorded as hitting 48.9C three times in 1896, with a maximum temperature of 38C for over three weeks straight. But climate scientists say the methods used to record temperature in 1896 were flawed and heatwaves today are hotter. They say the high death toll of 435 in 1896 was due to the community being more vulnerable to heat events.
[3] "The stunning chart revealing Australia's record-breaking run of rising temperatures", SMH, 10 January 2019.
[4] These studies are also referred to on the myths page below under the myth heading "It was warmer during the Mediaeval Warm period".
[5] Report in the Lancet published December 2018, findings reproduced in Scientific American, March 2019, 8-10.
[6] Peter Hannam, "Massive fish kills should serve as urgent 'wake-up call'", SMH. 19 February 2019.
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- Australia's September rainfall was the lowest on record. Nationally, rainfall in 2018 was the lowest since 2005 and 11 per cent below average, while rainfall in some areas was significantly further below normal.
- “Large areas of southeastern Australia experienced rainfall totals in the lowest 10 per cent on record, which exacerbated the severe drought conditions.”
- “NSW had its sixth driest year on record, while the Murray-Darling Basin saw its seventh-driest year on record.
In other significant weather events that year:
- Broome broke its annual rainfall record just two months into the year and Tropical Cyclone Marcus was the strongest to affect Darwin since Tracy in 1974.
- In August and September, up to 100 bushfires were active across NSW, Queensland and Victoria when warm, dry conditions brought an early start to the bushfire season.
The bureau also noted that:
- Australia was strongly influenced by both natural variability and climate change in 2018.
- Natural drivers included sea surface temperatures in the southern Tasman Sea which rose to “exceptionally high levels” in late 2017 and early 2018, contributing to warm overland conditions.
- Australia's climate “is increasingly influenced by global warming” and the nation has warmed by just over one degree since 1910. Most warming has occurred since 1950.
- “The background warming trend can only be explained by human influence on the global climate.”
In July 2019, three studies published in Nature and Nature Geoscience utilising extensive historical data show there has never been a period in the last 2,000 years when temperature changes have been as fast and extensive as in recent decades.
What the research also shows is that other "peak warming and cooling events" over the past two millennia appear to have been localised, whereas the human-caused global warming observed over the past 150 years is unparalleled in its global scale (not to mention its absolute temperatures).
The scientific consensus that humans are causing global warming is likely to have passed 99%, according to the lead author of the most authoritative of these studies, and could rise even further after separate research that clears up some of the remaining doubts.[4]
Meanwhile, warming temperatures not only threaten lives directly, they also cause billions of hours of lost labour, enhance conditions for the spread of infectious diseases and reduce crop yields, threatening food security.[5] Between December 2018 and January 2019, there occurred three major fish kills near Menindee in NSW involving the collective death of thousands of fish. These were attributed to blue-green algal blooms amid stagnant water flows and heatwaves, the former being the product of insufficient environmental water upstream to maintain the basic health of the river in dry times, largely the result of water being withdrawn from the river for irrigation purposes. [6]
And globally over the past decade?
Globally, 2010 to 2019 was the hottest decade since record keeping began 140 years ago. A joint analysis by NASA and NOAA (the National Oceanic and Atmospheric Administration) has revealed that 2019 was the second hottest year ever recorded, trailing only 2016, and that ocean temperatures were the highest they’ve ever been:
- These 10 years were punctuated by a series of deadly, dramatic, devastating events. Hurricanes like Sandy, Maria, and Harvey.
- On average, the annual temperatures over the years hover a little less than 1.8 degrees Fahrenheit (1 degree Celsius) higher now than they did from 1950 to 1980; the last five years alone was the hottest stretch ever recorded.
- As the average shifts upward, the likelihood of the extremely hot moments grows. “Extreme” heat events have come with more frequency in the past decade, and that pattern is only expected to intensify.
- Moreover, the overall warming is not happening evenly over the year or over distances. Winters are warming up faster than summers. With milder winters come a whole host of unsettling, ecosystem-reshaping changes.
- Even more notable change is apparent in the oceans. While air temperatures tend to wobble around from year to year, responding to big patterns like El Niño—the periodic Pacific water-warming weather event--the ocean smooths out the signal, integrating all the warming that’s happened over past years. It responds more slowly and more steadily to changes happening above its surface, and what it’s telling us is clear.
- The ocean has sucked up over 90 percent of all the extra heat trapped by human-caused climate change, and that signal is already apparent in its surface temperatures.
One clear driver
Behind all of the change is one clear driver: atmospheric carbon dioxide. In 2009, atmospheric CO2 concentrations hovered around 390 parts per million. By 2014, the number blew past 400 parts per million. Today, we hover around 410 ppm. The planet hasn’t seen concentrations that high since at least 2.6 million years ago. And at that time, no ice sheet existed in the northern polar regions and forests grew on Antarctica, sea levels were likely more than 40 feet higher than today, and the planet as a whole operated under very different conditions.
And the cause?
The underlying force beneath the changes is indisputable. Steadily increasing greenhouse gas concentrations in the atmosphere, caused primarily by humans burning fossil fuels, are trapping extra heat near Earth’s surface. That warms Earth as a whole. The outcome is both straightforward—a hotter planet—and incredibly complex, as changes cascade through the oceans, atmosphere, soil, rocks, trees, and every living thing on the planet.
"Climate change is here, it’s happening now, and it could very easily get much, much worse".
What is the solution?
Under the Paris climate accord, Australia has vowed to reduce greenhouse emissions, based on 2005 levels, by 26 per cent before 2030. Most recently, figures released by the Department of Environment and Energy in December 2018 showed that on current trends Australia will reduce emissions by just 7 per cent on 2005 levels by 2030, "a massive 19 percentage points or two thirds of the way short of the Paris agreement".
A major report prepared by the United Nations body for climate change, the Intergovernmental Panel on Climate Change, in October that year said coal-generated electricity must be phased out globally by 2050 if the world is to avoid the most catastrophic impacts of global warming, including the total destruction of the Great Barrier Reef.
It said radical, swift efforts must be taken to curb greenhouse gas pollution and keep the global temperature increase below the critical 1.5 degree threshold.
[1] “True shocker’: February spike in global temperatures stuns scientists”, SMH, 14 March 2016.
[2] However, in 1896, Bourke, NSW, was recorded as hitting 48.9C three times in 1896, with a maximum temperature of 38C for over three weeks straight. But climate scientists say the methods used to record temperature in 1896 were flawed and heatwaves today are hotter. They say the high death toll of 435 in 1896 was due to the community being more vulnerable to heat events.
[3] "The stunning chart revealing Australia's record-breaking run of rising temperatures", SMH, 10 January 2019.
[4] These studies are also referred to on the myths page below under the myth heading "It was warmer during the Mediaeval Warm period".
[5] Report in the Lancet published December 2018, findings reproduced in Scientific American, March 2019, 8-10.
[6] Peter Hannam, "Massive fish kills should serve as urgent 'wake-up call'", SMH. 19 February 2019.
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