2018-19 was Australia’s hottest summer on record, with a warm autumn likely too


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Dirty water from Queensland’s historic flooding, triggered by weeks of exceptional monsoon rains earlier in the year.
NASA Worldview/EPA

David Jones, Australian Bureau of Meteorology; Lynette Bettio, Australian Bureau of Meteorology, and Skie Tobin, Australian Bureau of Meteorology

Australian summers are getting hotter. Today marks the end of our warmest summer on record, setting new national temperature records. Worsening drought, locally significant flooding, damaging bushfires, and heatwaves capped a summer of extremes.

As we look to autumn, warmer temperatures overall and below average rainfall – especially in eastern parts of the country – are likely.

Australian summer mean temperature anomalies against the 1961–1990 average.
Bureau of Meteorology



Read more:
The stubborn high-pressure system behind Australia’s record heatwaves


Very hot…

The starkest feature of this summer was the record warmth. The national average temperature is expected to be about 2.1℃ above average, and will easily beat the previous record high set in summer 2012-13 (which was 1.28℃ warmer than average).

Very low rainfall accompanied the record heat of summer. At the national scale, each month was notably dry, and total summer rainfall was around 30% below average; the lowest for summer since 1982–83. The monsoon onset was delayed in Darwin until the 23rd of January (the latest since 1972–73) and typical monsoonal weather was absent for most of summer.

Preliminary summer 2018–19 mean temperature deciles.
Bureau of Meteorology

In December 2018 Australia saw its highest mean, maximum and minimum temperatures on record (monthly averages, compared to all other Decembers). Notable heatwaves affected the north of Australia at the start of the month, spreading to the west and south during the second half of December. Temperatures peaked at 49.3℃ at Marble Bar in Western Australia on the 27th, with mid-to-high 40s extending over larger areas.

The heat continued into January, which set a national monthly mean temperature record at 2.91℃ above the 1961–1990 average. Heatwave conditions which had emerged in December persisted, with a prolonged warm spell and numerous records set. Eight of the ten hottest days for the nation occurred during the month, while a minimum temperature of 36.6℃ at Wanaaring (Borrona Downs) in western New South Wales on the 26th set a new national minimum temperature record.

Temperatures moderated a little in the east of the country for February, partly in response to flooding rainfall in tropical Queensland. Even so, the national mean temperature will come in around 1.4℃ above average, making this February likely to be the fourth or fifth warmest on record.

…and very dry

Australia has seen dry summers before and many of these have been notably hot. The summers of 1972–73 and 1982–83 – which featured mean temperatures 0.90℃ and 0.92℃ above average, respectively – both came during the latter stages of significant droughts, and were both records at the time.

As the State of the Climate 2018 report outlines, Australia has warmed by just over 1℃ since 1910, with most warming occurring since 1950. This warming means global and Australian climate variability sits on top of a higher average temperature, which explains why 2018-19 was warmer again.

A major rain event affected tropical Queensland during late January to early February, associated with a slow-moving monsoonal low. Some sites had a year’s worth of rain in a two-week period, including Townsville Airport which had 1,257mm in ten days. Many Queenslanders affected by this monsoonal low went from drought conditions to floods in a matter of days. Flooding was severe and continues to affect rivers near the Gulf of Carpentaria, as well as some inland rivers which flow towards Kati Thanda–Lake Eyre.

Preliminary summer 2018–19 rainfall deciles.
Bureau of Meteorology

The outlook for autumn

Spring 2018 saw a positive Indian Ocean Dipole which faded in early summer. At the start of summer sea surface temperature anomalies in the central Pacific exceeded 0.8℃, which is the typical threshold for El Niño affecting the oceans, but these declined as summer progressed. Combined with a lack of coupling between the atmosphere and ocean, the El Niño–Southern Oscillation remained neutral, though normal rainfall patterns shifted to oceans to the north and east, leaving Australia drier as a result.

As we move into autumn, the El Niño–Southern Oscillation and Indian Ocean Dipole tend to have less influence at this time of year. The onset of new Indian Ocean Dipole or El Niño/La Niña events typically happens in late autumn or winter/spring.

Over recent years, autumn rainfall has also become less reliable, with declines in cool season rainfall in the southeast and southwest. Temperatures are also rising, in a local expression of the global warming trend.




Read more:
Explainer: El Niño and La Niña


The Bureau’s outlook for autumn shows high probabilities that day and night-time temperatures will remain above average for most of the country. We expect to see continued below-average rainfall in much of the east, where drought is currently widespread.

Looking to the winter, the Bureau’s ENSO Wrap-Up suggests the Pacific Ocean is likely to remain warmer than average. The potential for an El Niño remains, with approximately a 50% chance of El Niño developing during the southern hemisphere autumn or winter, twice the normal likelihood.

Rainfall outlook for autumn 2019.
Bureau of Meteorology


For more information watch BOM’s March–May 2019 Climate and Water Outlook video and subscribe to receive Climate Information emails.The Conversation

David Jones, Climate Scientist, Australian Bureau of Meteorology; Lynette Bettio, Senior Climatologist, Australian Bureau of Meteorology, and Skie Tobin, Climatologist, Australian Bureau of Meteorology

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

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2017 is set to be among the three hottest years on record


Andrew King, University of Melbourne and David Karoly, University of Melbourne

The year isn’t over yet, but we can already be sure that 2017 will be among the hottest years on record for the globe. While the global average surface temperature won’t match what we saw in 2016, it is now very likely that it will be one of the three warmest years on record, according to a statement issued by the World Meteorological Organization.

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What is more remarkable is that this year’s warmth comes without a boost from El Niño. When an El Niño brings warm waters to the tropical east Pacific, we see a transfer of heat from the ocean to the lower atmosphere, which can raise the global average temperatures recorded at the surface by an extra 0.1-0.2℃. But this year’s temperatures have been high even in the absence of this phenomenon.


Read more: Why hot weather records continue to tumble worldwide


We can already say with confidence that 2017 will end up being the warmest non-El Niño year on record, and that it will be warmer than any year before 2015. The average global temperature between January to September this year was roughly 1.1℃ warmer than the pre-industrial average.

This trend is associated with increased greenhouse gas concentrations, and this year we have seen record high global atmospheric carbon dioxide concentrations and the biggest recorded surge in CO₂ levels.

A year of extremes

Of course, none of us experiences the global average temperature, so we also care about local extreme weather. This year has already seen plenty of extremes.

Global sea ice extent continues to decline.
NASA Earth Observatory

At the poles we’ve seen a continuation of the global trend towards reduced sea ice extent. On February 13, global sea ice extent reached its lowest point on record, amid a record low winter for Arctic ice. Since then the Arctic sea ice extent has become less unusual but it still remains well below the satellite-era average. Antarctic sea ice extent also remains low but is no longer at record low levels as it was in February and March of this year.

East Africa saw continued drought with failure of the long rains, coupled with political instability, leading to food insecurity and population displacement, particularly in Somalia.

Storms and fires

This year also saw a very active North Atlantic hurricane season. Parts of the southern United States and the Caribbean were struck by major hurricanes such as Harvey, Irma, and Maria, and are still recovering from the effects.

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Other parts of the globe have seen a quieter year for tropical cyclones.

There have also been several notable wildfire outbreaks around the world this year. In Western Europe, record June heat and very dry conditions gave rise to severe fires in Portugal. This was followed by more severe fires across Spain and Portugal in October.


Read more: Wildfires are raging in the Mediterranean. What can we learn?


Parts of California also experienced severe fires following a wet winter, which promoted plant growth, and then a hot dry summer.

Australia is now gearing up for what is forecast to be a worse-than-average fire season after record winter daytime temperatures. A potential La Niña forming in the Pacific and recent rains in eastern Australia may reduce some of the bushfire risk.

The overall message

So what conclusions can we draw from this year’s extreme weather? It’s certainly clear that humans are warming the climate and increasing the chances of some of the extreme weather we’ve seem in 2017. In particular, many of this year’s heatwaves and hot spells have already been linked to human-caused climate change.

For other events the human influence is harder to determine. For example, the human fingerprint on East Africa’s drought is uncertain. It is also hard to say exactly how climate change is influencing tropical cyclones, beyond the fact that their impact is likely to be made worse by rising sea levels.

The ConversationFor much of 2017’s extreme weather, however, we can say that it is an indicator of what’s to come.

Andrew King, Climate Extremes Research Fellow, University of Melbourne and David Karoly, Professor of Atmospheric Science, University of Melbourne

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

2016 crowned hottest year on record: Australia needs to get heat smart


Liz Hanna, Australian National University; Kathryn Bowen, Australian National University, and Mark Howden, Australian National University

It’s official, 2016 set another record for being the world’s hottest. Three international agencies have confirmed today that last year was the hottest on record.

NASA reported that 2016 was 0.99℃ hotter than the 20th-century average, while the US National Oceanographic and Atmospheric Administration (NOAA) called it at 0.94℃. NOAA also calculated that global land temperatures were 1.43℃ higher. The UK Met Office, using its own data, also reported that 2016 is one of the two hottest years on record.

The figures vary slightly, depending on the baseline reference period used.

Heat records don’t linger for long any more. 2016 surpassed the 2015 record, which surpassed the 2014 record. Three record hot years in a row sets yet another record in the 137-year history of modern accurate and standardised meteorological observation.

For Australia, the Bureau of Meteorology described 2016 as a “year of extreme events” and the fourth hottest at 0.87℃ above the 1961-1990 average. The warming trend is clear.

Australia is already on average 8℃ hotter than the average global land temperature, so further warming means our heat risk is far greater than for other industrialised countries.

This dangerous warming trend sends a dire warning, as average warming delivers many more extreme heat events, as we’re currently seeing in Queensland and New South Wales. These are the killers.

As Australia lurches from heatwave to heatwave, the message is clear: extreme heat is the new norm – so Australia needs to get “heat smart”.

Rising extremes

In Australia the number of days per year over 35℃ has increased and extreme temperatures have increased on average at 7% per decade.

Very warm monthly maximum temperatures used to occur around 2% of the time during the period 1951–1980. During 2001–2015, these happened more than 11% of the time.

This trajectory of increased temperature extremes raises questions of how much heat can humans tolerate and still go about their daily business of commuting, managing domestic chores, working and keeping fit.

We can’t just get used to the heat

Air-conditioning and acclimatisation are not the answer. Acclimatisation to heat has an upper limit, beyond which humans need to rest or risk overheating and potential death. And air-conditioning, if not powered by renewable electricity, increases greenhouse gas emissions, feeding into further climate changes.

We have two key tasks ahead. The first is to stop the warming by drastically reducing emissions – the 2015 Paris Agreement was a step along this path. Several studies have shown that Australia can achieve net zero emissions by 2050 and live within its recommended carbon budget, using technologies that exist today, while maintaining economic prosperity.

Our second task is to adapt to the trajectory of increasing frequency of dangerous heat events.

A heat-smart nation

We can prevent heat-related deaths and illnesses through public health mechanisms. Australia enjoys a strong international track record of world-leading public health prevention strategies, such as our campaign against smoking.

We can equally embrace the heat challenge, by adopting initiatives such as a National Climate, Health and Wellbeing Strategy, which has the support of Australia’s health sector. Its recommendations outline a pathway to becoming a heat-smart nation.

At a recent heat-health summit in Melbourne, experts declared Australia must adopt four key public health actions to reduce heatwave deaths.

These are:

• Prevent

• Prepare

• Respond

• Educate.

These fundamental public health strategies are interlinked and operate at the government, health sector, industry and community levels.

Prevention includes reducing greenhouse gas emissions, as well as reducing exposure. The Bureau of Meteorology provides superb heat warnings that allow us to prepare. Global organisations such as the Intergovernmental Panel on Climate Change (IPCC) provide reports that can underpin greater understanding.

The next challenge is for the populace broadly to act on that knowledge. This requires having options to protect ourselves and avoid hazardous heat exposures while commuting, working and at home.

The health sector must also prepare for demand surges. Tragic outcomes will become increasingly common when, for example, ambulance services cannot meet rising demand from a combination of population growth, urbanisation and forecast heat events.

The health sector will need the capacity to mobilise extra resources, and a workforce trained in identifying and managing heat illness. Such training remains limited.

Individuals and workplaces also need to prepare for heatwaves. In a heat-smart nation, we’ll need to reschedule tasks to avoid or limit exposure, including rest periods, and to ensure adequate hydration with cool fluids.

We’ll need to think about housing. Building houses without eaves or space for trees to provide shade forces residents to rely on air-conditioning. In such houses, power failures expose residents to unnecessary heat risks, and many air-con systems struggle when temperatures exceed 40℃.

Urban planners and architects have solutions. There are many options for safe housing design, and the government should consider supporting such schemes.

We’ll need to think about our own health. Active transport, such as walking and cycling, both reduces emissions and improves fitness. Promoting active transport throughout summer requires the provision of shade, rest zones with seats, and watering stations along commuting routes. High cardio-respiratory fitness also boosts heat resilience: a win-win.

Ultimately, Australia has two options: ignore the risks of increasing heat extremes and suffer the consequences, or step up to the challenge and become a heat-smart nation.


This article was co-authored by Clare de Castella Mackay, ANU.

The Conversation

Liz Hanna, Honorary Senior Fellow, Australian National University; Kathryn Bowen, Senior Research Fellow, Australian National University, and Mark Howden, Director, Climate Change Institute, Australian National University

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

Australia simmers through hottest autumn on record


Andrew King, University of Melbourne

It’s the same old story: with 2016 on track to become the hottest year on record globally, and record-breaking heat already evident around the world, Australia has just experienced its hottest autumn on record.

Figures from the Bureau of Meteorology indicate Australia has experienced its hottest autumn on record.
Bureau of Meteorology

The Bureau of Meteorology has reported that for average temperatures across Australia, this has been the hottest March-May period ever recorded – beating the previous record, set in 2005, by more than 0.2℃.

Within this period, March was also the hottest on record, while April and May were each the second-warmest in a series extending back to 1910.

Temperatures were well above average across much of the country, especially in the east.
Bureau of Meteorology

Why so hot?

El Niño events tend to cause warmer weather across the east and north of Australia and the major El Niño of 2015-16 undoubtedly contributed to the extreme temperatures experienced across these areas.

However, climate change also played a significant role in our warmest autumn. Previous work, led by ANU climatologist Sophie Lewis, indicates that the human influence on the climate has made a record-breakingly hot autumn roughly 20 times more likely.

In other words, without climate change we would be much less likely to experience autumns as warm as this one has been in Australia.

How we’ll remember autumn 2016

In the past few months, Australia has seen many extreme hot weather events. Melbourne experienced its warmest March night on record, while Sydney had a run of 39 days with daytime highs above 26℃, as the summer heat continued long into March.

But it’s the coral bleaching event on the Great Barrier Reef that will likely linger in our memories the longest. Some 93% of the reef was found to be affected by bleaching and recent surveys have revealed that more than one-third of coral in the northern and central parts of the reef have died.

Without climate change, a bleaching event like this would be virtually impossible.

The extreme heat over Australia this autumn and the associated damage to the reef are also having an effect on the election campaign. As public concern over the future of the reef grows, the parties are being asked to defend their climate change policies.

Both major parties have made election commitments to the reef, with the Coalition announcing an extra A$6 million to tackle crown-of-thorns starfish (adding to a further A$171 million committed under the 2016 budget), and Labor an extra A$377 million over five years (A$500 million in total). While both Labor and the Coalition aim to improve water quality in the reef through their policies, the coral bleaching and death this year is linked with warm seas.

Whether we’ll be able to save parts of the reef largely depends on whether we reduce our greenhouse gas emissions and manage to prevent the rising trend in temperatures from continuing.

The Conversation

Andrew King, Climate Extremes Research Fellow, University of Melbourne

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

2016 is likely to be the world’s hottest year: here’s why


Andrew King, University of Melbourne and Ed Hawkins, University of Reading

We’re not even halfway through the year but already you may have heard talk of 2016 being the hottest on record. But how can scientists be so sure we’re going to beat the previous record, set just last year?

Even before the end of 2015, the UK Met Office was forecasting with 95% confidence that 2016 would beat the record. Since then, that confidence has grown still further, as record after record has tumbled. April 2016 broke the record for the hottest April after we had experienced the hottest February and March on record already this year.

NASA climatologist Gavin Schmidt recently estimated at least a 99% likelihood of 2016 being hotter than 2015.

The role of El Niño

The main reason why scientists are so sure that 2016 will be the hottest year is El Niño, which is associated with warmer sea surface temperatures in the eastern Pacific Ocean. The 2015-16 El Niño was among the strongest on record and has increased global average temperatures.

Even though the El Niño is now decaying, the second year of a major El Niño event is often associated with much warmer than normal conditions and is typically warmer than the first.

For instance, the 1997-98 El Niño was by some measures the strongest on record, and contributed to 1998 becoming the hottest year on record globally at the time.

Since the start of this year, we have seen global temperature records smashed time and time again. This means that much colder temperatures for the second half of the year would be needed for 2016 not to surpass the 2015 record.

Even a strong La Niña event (the cooler opposite of El Niño), which some analysts are forecasting, is unlikely to produce cold enough temperatures.

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One thing that could prevent 2016 becoming a record-breaking hot year is a major volcanic eruption in the tropics. Volcanic eruptions at low latitudes can eject aerosols high into the atmosphere reducing the amount of energy from the sun reaching the Earth’s surface.

Previous eruptions such as Pinatubo in 1991 and Tambora in 1815 (which caused 1816 to be “the year without a summer”) reduced temperatures across much of the globe.

However, it is the year after the eruption that often experiences the most severe cooling, so an eruption would have to be pretty soon and very strong to scupper 2016’s chances of being the hottest year on record.

What about climate change?

The role of climate change is smaller because we’re comparing 2016 with last year (the previous record). Over such short periods of time, the contribution from global warming doesn’t change much.

However, scientists estimated that 2015 was about 1℃ hotter than it would have been without human-caused climate change. As the human influence on the climate has not increased greatly since last year this 1℃ estimate will also apply to 2016.

The highly likely record temperature of 2016 will join the previous 17 record-breaking hot years back to 1937 which were all made more likely due to human-caused climate change (the rising global temperatures were even noticed as far back as 1938).

So even if El Niño is driving the 2016 record, we can say that the temperatures of this year (and indeed the temperatures associated with all the records over the last few years) would be virtually impossible without climate change.

Climate change has been increasing the likelihood of global temperature records for many decades. The vertical red bars show the record-breaking hot years we can attribute to human-induced climate change. The shorter yellow bars show ranges of estimates for how much more likely a record hot year becomes each year.
Andrew King, Author provided

An omen for the future?

We expect 2016 to beat the 2015 record for global average temperature as the decaying El Niño event pushes up surface temperatures.

This year, we’ve already seen devastating events associated with unusually warm temperatures, like the mass coral bleaching in the Great Barrier Reef, which has been largely attributed to human-induced climate change.

In future, we can expect to see more extreme heat events, like we’ve already seen in 2016, impacting society and ecosystems across the world.

And even though 2016 is likely to be the hottest year by some margin, we wouldn’t bet on this record lasting too long. While 2017 is very likely to be cooler due to a possible La Niña, with the strong warming trend the world’s experiencing it’s only a matter of time before we have another record-breaking hot year.

Only if we substantially reduce our greenhouse gas emissions now will we see the benefit of fewer record heat events in the future.

The Conversation

Andrew King, Climate Extremes Research Fellow, University of Melbourne and Ed Hawkins, Associate professor of climate science , University of Reading

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

This summer’s sea temperatures were the hottest on record for Australia: here’s why


Elaine Miles, Australian Bureau of Meteorology; Claire Spillman, Australian Bureau of Meteorology; David Jones, Australian Bureau of Meteorology, and David Walland, Australian Bureau of Meteorology

The summer of 2015-2016 was one of the hottest on record in Australia. But it has also been hot in the waters surrounding the nation: the hottest summer on record, in fact.

Difference in summer sea surface temperatures for the Australian region relative to the average period 1961-1990.
Australian Bureau of Meteorology

While summer on land has been dominated by significant warm spells, bushfires, and dryness, there is a bigger problem looming in the oceans around Australia.

This summer has outstripped long-term sea surface temperature records that extend back to the 1950s. We have seen warm surface temperatures all around Australia and across most of the Pacific and Indian oceans, with particularly warm temperatures in the southeast and northern Australian regions.

Last summer’s sea surface temperature rankings for Australia.
Australian Bureau of Meteorology

In recent months, this warming has been boosted – just like land temperatures – by natural and human-caused climate factors.

Why so warm?

These record-breaking ocean temperatures around Australia are somewhat surprising. El Niño events, such as the one we’re currently experiencing, typically result in cooler than normal Australian waters during the second half of the year. So what is the cause?

The most likely culprit is a combination of local ocean and weather events, with a substantial contributor being human-caused climate change.

In the north, the recent weak monsoon season played a role in warming surface waters. Reduced cloud cover means more sunshine is able to pass through the atmosphere and heat the surface of the ocean. Trade winds that normally stir up the water and disperse the heat deeper into the ocean have also remained weak, leaving the warm water sitting at the surface.

In the south, the East Australian Current has extended further south over the summer. This warm current flows north to south down Australia’s east coast. Normally it takes a left turn and heads towards New Zealand, but this year it extended down to Tasmania, bringing warm waters to the south east.

This current is also getting stronger, transporting larger volumes of water southward over time. This is due to the southward movement of high pressure systems towards the pole.

High pressure systems are often associated with clear weather in Australia, and when they move south they prevent rain. This southward movement over time has also been linked to climate changes in our region, meaning that changes in both rainfall and ocean temperatures are responses to the same global factors.

We’ve also seen high ocean temperatures in the Indian Ocean. Around 2010, temperatures in the region suddenly jumped, likely because of the La Niña event in the Pacific Ocean. The strong events during this period transferred massive amounts of warmth from the Pacific Ocean into the Indian Ocean through the Indonesian region.

The warmer waters in the Indian Ocean have persisted since and have influenced land temperatures. The five years since the 2010 La Niña are the five hottest on record in southwest Western Australia (ranked 2011, 2015, 2014, 2013 and 2012).

What are the impacts?

The world’s oceans play a major role in global climate by absorbing surplus heat and energy. Oceans have absorbed 93% of the extra heat trapped by the Earth since 1970 as the greenhouse effect has increased. This has lowered the rate at which the atmosphere is warming – which is a good thing.

However, it also means the oceans are heating up, raising sea levels as well as leading to more indirect impacts, such as shifting rainfall patterns.

As a nation that likes to live by the coast as well as enjoy recreation activities and harvest produce from the sea, warmer-than-usual oceans can have significant impacts.

Australia derives a lot of its income from its oceans and while such impacts aren’t often seen immediately, they become apparent over time.

Warm sea temperatures this summer and in the past have seen declines in coral reef health, and strains on commercial fisheries and aquaculture. The Great Barrier Reef is currently experiencing coral bleaching amid very warm water temperatures.

Our neighbouring Pacific islands have also seen the impacts of these very high sea surface temperatures, with recent mass fish kills and coral bleaching episodes in Fiji.

The impacts of warmer ocean temperatures are also felt on land, as ocean temperatures drive climate and weather. Abnormally high sea surface temperatures may have contributed to the intensity of Cyclone Winston as cyclone potential intensity increases with ocean temperature.

What is the outlook?

The seasonal outlook from the Bureau of Meteorology shows El Niño weakening over the next few months. This typically means cooler weather and can mean more rain on land.

However, closer inspection shows surface temperatures over the entire Indian Ocean and coastal Australian waters will very likely continue to remain well above average for the next few months. There are currently signs that surface currents are moving warm El Niño waters from the eastern Pacific over to the western Pacific, towards Australia.

There is potential for the East Australian Current to continue to transport this warmth to southern waters as far as Tasmania. Warm water could also be transported through Indonesia and travel south along the Western Australian coast via the warm Leeuwin Current, potentially causing further warming of already record warm waters.

So for the near future, the waters are going to continue to be warm. That’s good news if you’re heading to the beach, but not so good for the environment.

The Conversation

Elaine Miles, Ocean Climatologist , Australian Bureau of Meteorology; Claire Spillman, Research Scientist, Australian Bureau of Meteorology; David Jones, Scientist, Australian Bureau of Meteorology, and David Walland, , Australian Bureau of Meteorology

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

It’s official: 2015 was the hottest year ever recorded


Janette Lindesay, Australian National University and Mark Howden, CSIRO

It’s official: 2015 was the hottest year on record. The US-based National Oceanic and Atmospheric Administration has confirmed overnight that 2015 saw the global average temperature climbing to 0.90°C above the 20th-century average of 13.9°C. The record has been confirmed by the UK Met Office.

It’s been only a year since the record was previously broken, but 2015 stands out as an extraordinarily hot year. 2014, the previous hottest year, was 0.74°C above the global average. December 2015 marks the first time in the NOAA record a global monthly temperature anomaly has exceeded 1°C – it reached 1.11°C.

Every month since February 1985 has been warmer than average, and 2015 is the 39th consecutive year with above-average annual temperatures in an uninterrupted run that began in the mid 1970s. Ten months in 2015 beat previous records for those months.

The evidence that the so-called “global warming hiatus” is over is compelling – if it ever existed.

https://charts.datawrapper.de/9RvfW/index.html

Air temperatures over the land rose markedly to a new record of 1.33°C above average, and ocean temperatures also reached a new record anomaly of 0.74°C in 2015. The global ocean has absorbed up to 90% of the excess heat retained or accumulated by human activities since the industrial revolution, and ocean temperatures show clear warming trends both at the surface and deep down.

In 2015/2016 a strong El Niño event is bringing some of that heat buried in the ocean back to the surface.

The “perfect storm”

Global temperatures are influenced by both natural and human factors.

2015 saw the development of an El Niño event classed as one of the three strongest on record, comparable to those of 1982/83 and 1997/98.

These events are linked to higher global air temperatures. Since 1850 many of the warmest years have also been El Niño years. El Niño events are driven by changes in the winds across the Pacific Ocean, which move warm water from the western Pacific to the east.

In 2015 central Pacific sea surface temperatures were more than 3°C above average over an area of approximately 5.5 million square kilometres, around 70% of the size of the Australian continent. Air temperatures increase during El Niño events as heat is transferred from the ocean to the atmosphere.

Sea surface temperature anomalies, Oct-Dec 2015 showing the characteristic El Niño pattern of increases across the central to eastern Pacific
NOAA

But a strong El Niño event alone is not sufficient to account for the 2015 record temperature anomaly.

In May 2015 carbon dioxide concentrations reached a monthly value of 403.9 parts per million (ppm) – the highest ever recorded. The average concentration of CO₂ in 2015 may exceed 400 pppm for the first time in human history. CO₂ is the one of the principal greenhouse gases responsible for human-induced global warming.

Since 2008 the CO₂ concentration has increased by an average of 2.1 ppm per year, largely due to fossil fuel and land-use emissions, emphasising the significant impact of human activity on the atmosphere.

CO₂ concentrations now exceed pre-industrial levels by more than 40%, and the likelihood of this increase and the associated warming being due only to natural factors is vanishingly small.

Carbon dioxide exceeded 400 ppm in 8 months in 2015.
NOAA

Climate extremes everywhere

Across the globe 2015 was characterised by weather and climate extremes from floods and severe storms to droughts and heatwaves.

In Australia climate conditions are being pushed beyond our historical experience of natural climate variability and into new territory. Global warming has increased the likelihood of record-breaking temperatures by up to 100 times.

In 2015 records were broken once again across Australia, in a series of high temperature events particularly in Western Australia (January), Queensland (March), and the south-eastern states (October, November and December).

The Bureau of Meteorology 2015 Annual Climate Statement highlights October as particularly noteworthy. October 2015 was 2.89℃ warmer than the average October inn Australia. While this doesn’t make October the hottest month overall (that title still belongs to the summer months), it is the largest margin by which a monthly record has ever been broken.

High temperatures broke the internet (literally); led to cancelled sporting events in Victoria and South Australia; and added to severe bushfire conditions in several states.

October 2015 warmest on record with largest temperature anomaly.
Australia Bureau of Meteorology

In response to concerns about this ongoing warming and the associated heat extremes, the wine industry is exploring adaptation options including changing grape varieties; cereal crop, fruit, vegetable and milk producers are trying to reduce the impact of heatwaves and droughts on yields; and we need to change our behaviour and infrastructure to deal with the health impacts of more extreme temperatures and more frequent heatwaves.

We are all affected by global warming.

The necessity of mitigation

The climate and weather impacts of 2015 in Australia are examples of what is happening around the globe, adding to the overwhelming body of evidence of the reality and impacts of global warming.

The combination of a strong El Niño event with ongoing human-induced warming of the ocean and atmosphere set up the conditions for 2015. It is unlikely to be the last such record.

El Niño events are part of natural climate variability and will continue to occur, and until greenhouse gas emissions are reduced at least in line with the Paris Climate Agreement global temperatures will continue to rise for the foreseeable future.

As agreed by the governments of the world at the Paris UNFCCC meeting, the need for effective and urgent local, national and global action to reduce emissions has never been more pointed.

The Conversation

Janette Lindesay, Professor of Climatology, Australian National University and Mark Howden, Research Scientist, Agriculture Flagship, CSIRO

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