Why drought-busting rain depends on the tropical oceans


Andrew King, University of Melbourne; Andy Pitman, UNSW; Anna Ukkola, Australian National University; Ben Henley, University of Melbourne, and Josephine Brown, University of Melbourne

Recent helpful rains dampened fire grounds and gave many farmers a reason to cheer. But much of southeast Australia remains in severe drought.

Australia is no stranger to drought, but the current one stands out when looking at rainfall records over the past 120 years. This drought has been marked by three consecutive extremely dry winters in the Murray-Darling basin, which rank in the driest 10% of winters since 1900.

Despite recent rainfall the southeast of Australia remains in the grip of a multi-year drought.
Bureau of Meteorology

So what’s going on?

There has been much discussion on whether human-caused climate change is to blame. Our new study explores Australian droughts through a different lens.




Read more:
Rain has eased the dry, but more is needed to break the drought


Rather than focusing on what’s causing the dry conditions, we investigated why it’s been such a long time since we had widespread drought-breaking rain. And it’s got a lot to do with how the temperature varies in the Pacific and Indian Ocean.

Our findings suggest that while climate change does contribute to drought, blame can predominately be pointed at the absence of the Pacific Ocean’s La Niña and the negative Indian Ocean Dipole – climate drivers responsible for bringing wetter weather.

Understanding the Indian Ocean Dipole.

What’s the Indian Ocean Dipole?

As you may already know, the Pacific Ocean influences eastern Australia’s climate through El Niño conditions (associated with drier weather) and La Niña conditions (associated with wetter weather).

The lesser known cousin of El Niño and La Niña across the Indian Ocean is called the Indian Ocean Dipole. This refers to the difference in ocean temperature between the eastern and western sides of the Indian Ocean. It modulates winter and springtime rainfall in southeastern Australia.




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Dipole: the ‘Indian Niño’ that has brought devastating drought to East Africa


When the Indian Ocean Dipole is “negative”, there are warmer ocean temperatures in the east Indian Ocean, and we see more rain over much of Australia. The opposite is true for “positive” Indian Ocean Dipole events, which bring less rain.

The Murray-Darling Basin experiences high rainfall variability, with decade-long droughts common since observations began. The graph shows seasonal rainfall anomalies from a 1961-1990 average with major droughts marked.
Author provided

What does it mean for the drought?

When the drought started to take hold in 2017 and 2018, we didn’t experience an El Niño or strongly positive Indian Ocean Dipole event. These are two dry-weather conditions we might expect to see at the start of a drought.

Rather, conditions in the Pacific and Indian Oceans were near neutral, with little to suggest a drought would develop.

So why are we in severe, prolonged drought?

The problem is we haven’t had either a La Niña or a negative Indian Ocean Dipole event since winter 2016. Our study shows the lack of these events helps explain why eastern Australia is in drought.

For the southeast of Australia in particular, La Niña or negative Indian Ocean Dipole events provide the atmosphere with suitable conditions for persistent and widespread rainfall to occur. So while neither La Niña or a negative Indian Ocean Dipole guarantee heavy rainfall, they do increase the chances.

What about climate change?

While climate drivers are predominately causing this drought, climate change also contributes, though more work is needed to understand what role it specifically plays.

Drought is more complicated and multidimensional than simply “not much rain for a long time”. It can be measured with a raft of metrics beyond rainfall patterns, including metrics that look at humidity levels and evaporation rates.

What we do know is that climate change can exacerbate some of these metrics, which, in turn, can affect drought.




Read more:
Is Australia’s current drought caused by climate change? It’s complicated


Climate change might also influence climate drivers, though right now it’s hard to tell how. A 2015 study suggests that under climate change, La Niña events will become more extreme. Another study from earlier this month suggests climate change is driving more positive Indian Ocean Dipole events, bringing even more drought.

Unfortunately, regional-scale projections from climate models aren’t perfect and we can’t be sure how the ocean patterns that increase the chances of drought-breaking rains will change under global warming. What is clear is there’s a risk they will change, and strongly affect our rainfall.

Putting the drought in context

Long periods when a La Niña or a negative Indian Ocean Dipole event were absent characterised Australia’s past droughts. This includes two periods of more than three years that brought us the Second World War drought and the Millennium drought.

The longer the time without a La Niña or negative Indian Ocean Dipole event, the more likely the Murray-Darling Basin is in drought.

In the above graph, the longer each line continues before stopping, the longer the time since a La Niña or negative Indian Ocean Dipole event occurred. The lower the lines travel, the less rainfall was received in the Murray Darling basin during this period. This lets us compare the current drought to previous droughts.

During the current drought (black line) we see how the rainfall deficit continues for several years, almost identically to how the Millennium drought played out.

But then the deficit increases strongly in late 2019, when we had a strongly positive Indian Ocean Dipole.

So when will this drought break?

This is a hard question to answer. While recent rains have been helpful, we’ve developed a long-term rainfall deficit in the Murray-Darling Basin and elsewhere that will be hard to recover from without either a La Niña or negative Indian Ocean Dipole event.




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The most recent seasonal forecasts don’t predict either a negative Indian Ocean Dipole or La Niña event forming in the next three months. However, accurate forecasts are difficult at this time of year as we approach the “autumn predictability barrier”.

This means, for the coming months, the drought probably won’t break. After that, it’s anyone’s guess. We can only hope conditions improve.The Conversation

Andrew King, ARC DECRA fellow, University of Melbourne; Andy Pitman, Director of the ARC Centre of Excellence for Climate System Science, UNSW; Anna Ukkola, Research Fellow, Australian National University; Ben Henley, Research Fellow in Climate and Water Resources, University of Melbourne, and Josephine Brown, Lecturer, University of Melbourne

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

Might the bushfire crisis be the turning point on climate politics Australian needs?



The bushfire crisis is big enough to change the government’s emissions policy, but it swill need more.
Shutterstock

John Daley, Grattan Institute and Emily Millane, Grattan Institute

Countries have long periods in which policies change little, and only by increments.

Occasionally there are turning points, when previously intractable policy problems are suddenly resolved, recasting policy for the long term.

Many are asking whether this summer’s environmental catastrophe might be such a turning point – a Port Arthur moment or Australia’s Sandy Hook, Chernobyl or Pearl Harbour.

The short answer is: it is too soon to tell, but the early signals from the federal government are not good.

Crises can provide a window for big policy changes. In such times, the normal political constraints are relaxed, although not for long.

Crisis can beget change

The need for revenue during World War I opened the way for the federal government to levy a national income tax. The terrorist attacks of September 11, 2001 stimulated many changes concerned with national security.

Typically, a crisis only leads to substantial policy changes if there is also a broader understanding about the need to act, and the shape of the change needed.

The economic theories of John Maynard Keynes provided the basis for policies that ensured full employment during and after World War II.

The monetarist theories of Milton Friedman provided the means to limit inflation in the 1970s and 1980s.

A library of pre-existing publications on national security directed policy in the wake of 9/11.

Theory is needed as well

Crisis and economic theory were essential to some of the big reforms under the Hawke and Keating governments, including a new approach to Australian retirement incomes.

Superannuation had been a patchwork of individual employer arrangements since before federation.

The stagflation crisis of simultaneous unemployment and inflation in the 1970s created the conditions for a new approach. Inflation rose to 15%, unemployment to 6%. It led to government-union Accords and deferred wage increases that were the basis for Australia’s universal employee superannuation scheme.




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Australian politics explainer: the Prices and Incomes Accord


Many see the 1986 Chernobyl disaster as a turning point in ending the cold war and dismantling the Soviet Union. Mikhail Gorbachev acted decisively in the midst of a disaster that created a groundswell of support for change bringing in an system (capitalism) which had deep theoretical underpinnings.

Not every crisis leads to change

US President Obama hugs Mark Barden, whose seven year old son Daniel was shot and killed in the Sandy Hook Elementary School attack in 2012.
MICHAEL REYNOLDS/EPA

For decades, gun control has been contentious in the United States, where gun-related homicides are ten times the rates elsewhere. 26 people, including 20 children aged 6 and 7, in a gun massacre at Sandy Hook Elementary School in 2012.

President Obama was personally committed to, and moved fast after the crisis to call for, tighter gun control. But change was stymied by powerful stakeholders.

By contrast, John Howard was successful in moving quickly after the 1996 Port Arthur massacre to tighten gun controls.

The Australian gun lobby lacked the political sophistication of America’s National Rifle Association, and Australia’s political system has fewer veto points than in the US.

The attack on Pearl Harbour in 1941 brought World War II to America, mobilising huge levels of public support for American involvement. Within days, Roosevelt declared war on Japan.

The nation might not be ready

There are high levels of public support for action climate change in Australia, but can we say it is the same as “war fever”?

Australia’s emissions policy has been stuck for a long time. Australia was recently ranked as having the worst climate policy in the world, and some of the worst outcomes.

Australia’s annual emissions are not expected to change much between 2020 and 2030 – which doesn’t give Australia much chance of getting to near zero emissions by 2050, which is generally regarded as what’s needed to avoid runaway climate change.

Many in public policy have spent years developing credible policy responses to climate change. But Australia has repealed or failed to implement five versions of climate policy since 2007.




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The good, the bad and the ugly: the nations leading and failing on climate action


There are reasons to believe the summer bushfire crisis won’t be any different.

No-one has accused the Prime Minister of moving too fast or too far in responding to the fires. In his interview with ABC at the weekend, he did not commit to tightening, or even reviewing, Australia’s carbon emissions targets in light of the fires.

Powerful stakeholders continue to deny the need for significant policy change: last month the federal resources minister, Matt Canavan, referred to the “bogeyman of climate change” as a distraction from “shortcomings in managing our land.”

Fake news on social media and in some sections of the mainstream media about an arson emergency has blunted the chance of a broad-based popular groundswell.

There’s hope, but not much

The proposed royal commission might be a means to find a way forward on climate change. But by the time it reports, the fires will be out, and the moment of crisis will have passed.

For now, the fires smoulder on. It’s not too late for the federal government to seize the opportunity for substantial change. State governments may well use the aftermath of the fires to coordinate their responses to climate change – possibly without the Commonwealth. For the moment, they are understandably preoccupied with responding to an ongoing emergency.




Read more:
Bushfires won’t change climate policy overnight. But Morrison can shift the Coalition without losing face


There is a real possibility that Australia will have to wait for another crisis – with different leadership, and more public consensus – before there is significant change on emissions policy.

The bushfire smoke that chokes 10 million people in Sydney, Melbourne, Canberra, and elsewhere will no doubt contribute to changing attitudes, and it might even shift the media’s coverage of climate change, but there’s no guarantee that it will be the policy turning point we need.The Conversation

John Daley, Chief Executive Officer, Grattan Institute and Emily Millane, Senior Associate, Grattan Institute

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

Bushfires won’t change climate policy overnight. But Morrison can shift the Coalition without losing face



When polling resumes after the summer, Scott Morrison may be surprised by the public’s assessment of his government’s handling of the bushfires.
Mick Tsikas/AAP

Chris Wallace, Australian National University

The hope of many people enduring this summer’s firestorms is that better climate policy will arise phoenix-like from the ashes.

It is expressed loudly, fervently, sometimes abusively by people directly affected and those feeling solidarity with them.

It is also expressed secretly, whispered to like-minded confidants, by others who are part of or allied with the Liberal-National (LNP) coalition government of Prime Minister Scott Morrison.

On Sunday, Morrison indicated that he would take a proposal to establish a royal commission into the bushfires to his Cabinet.

But when it comes to climate policy, there are three possible scenarios in the aftermath of the crisis: everything magically changes for the better, everything stays the same or something different happens.

What these three scenarios look like

Everything magically changes for the better would look like this: Morrison announces the crisis has transformed his previous token admission of a link between bushfires and climate change into a revelation of the reality of global warming, with consequential policy change.

As logical and desirable as this seems, it is unlikely, not least because of Morrison’s character and personal beliefs.

Everything stays the same has a powerful impetus behind it. Morrison does not want policy change any more than his likely successor in the event of leadership change, Peter Dutton.




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Government-friendly journalists and commentators at News Corp and 2GB show no sign of changing tack either, so even if the government wanted to shift its policy, the media environment makes it difficult to do so. The forces of inertia are powerful.

Then there is the slim hope that something different happens. This scenario relies on all three of Australia’s main political groupings – the LNP, Labor and the Greens – realising they each face their own distinct climate policy challenge and rising to it.

As Australian burns, its politicians squabble over who’s to blame and how to prevent future disasters.
David Mariuz/AAP

Avoiding the appearance of a backflip

Opinion polls are not done over the summer holiday period, meaning the LNP has yet to see the impact of the bushfires on their public standing.

When polling resumes, Liberal and National MPs will understand the impact, and they won’t like it. Morrison and others will likely urge party members to hold their course since the next election is years away and a dozen other issues could distract attention from climate policy between now and then.

This tactic can prevail for some time but is not strategically sustainable: firestorms like those in the summer of 2020 will not be the last.




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Grattan on Friday: When the firies call him out on climate change, Scott Morrison should listen


The emerging LNP argument that inadequate hazard reduction burns are to blame for the current crisis is risible. The Australian who has emerged with the most credibility from the bushfires – NSW Rural Fire Service Commissioner Shane Fitzsimmons – rejects it out of hand.

The LNP’s challenge, then, is to realise its current position won’t hold strategically and to transition to better policy ahead of that becoming obvious, managing the optics to avoid the appearance of a backflip.

The challenge for Labor and the Greens

Labor is benefiting from leader Anthony Albanese’s call for “an adult conversation” in Australia about climate policy. He is astutely citing British Tories like the late Margaret Thatcher and current Prime Minister Boris Johnson, who long ago accepted and acted upon the climate science the Morrison government viscerally rejects.

Labor’s homework now is to reconcile the views and interests of members and supporters prioritising climate policy over mining jobs, and vice versa.

This can and must be done if Labor is to build a coalition of support big enough to win office and then enact the climate and other policies the current firestorms make so urgent.




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It’s the 10-year anniversary of our climate policy abyss. But don’t blame the Greens


The Greens, meanwhile, need to have an internal conversation about whether they want to continue making perfect policy the enemy of the good – leaving Australia with no emissions trading system (ETS) at all, for example, because they would not vote for one that did not meet their every demand – or join in efforts to begin on the path to better policy.

Central to that conversation must be a realisation their current strategy isn’t working – the LNP keeps returning to power.

Greens leader Richard Di Natale has said the bushfires should be a
David Crosling/AAP

A possible way forward

There is an obvious point the LNP, Labor and Greens might momentarily agree upon to move policy forward. It is the ETS proposed by Liberal Prime Minister John Howard in 2007.

Howard saw climate change coming. In late 2006, he established a prime ministerial task group on emissions trading chaired by the secretary of his Department of Prime Minister and Cabinet, Peter Shergold.

The Shergold Report, released in May 2007, said “emissions trading should be preferred to a carbon tax” and among the various kinds possible, a national “cap and trade” ETS was best.

In an address to the Liberal Party Federal Council in October 2007, Howard promised to establish a national ETS starting no later than 2012.

This will be a world-class emissions trading system more comprehensive, more rigorously grounded in economics and with better governance than anything in Europe.

Implementing an emissions trading scheme and setting a long-term goal for reducing emissions will be the most momentous economic decisions Australia will take in the next decade.

This emissions trading system must be built to last. It needs to last not five or 10 years, it needs to last the whole of the 21st century if Australia is to meet our global responsibilities and further build our economic prosperity.

Howard positioned the LNP as the party Australians could trust to implement an ETS in a way that gives “firms and families” the ability to “plan for the future with confidence”.

His authorship – and his framing of his ETS as an act of economic responsibility –provides a fig leaf Morrison can now use to move the LNP to a credible, sustainable and politically viable climate policy position.

“Something different” has to start somewhere. If Morrison can deploy the cunning he showed winning the 2019 election by drawing on Howard’s deep well of credibility within the LNP to implement the plan himself and then inviting – daring – Labor and the Greens to back him, it would be a signal political achievement.

And if Morrison doesn’t want to, Labor, the Greens, independent MPs and conscientious LNP MPs should vote together to turn Howard’s ETS into law right away. With political will, “something different” can start now.


Updates to add that the latest Newspoll, released late Sunday, shows Morrison’s standing has taken a massive hit over the bushfires, dropping nine percentage points as preferred prime minister from 48% to 39% since the last poll in early December. Opposition leader Anthony Albanese stood at 43% – a massive reversal of Morrison’s 14 percentage point lead over the Labor leader in early December.The Conversation

Chris Wallace, ARC DECRA Fellow, Australian National University

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

Listen to your people Scott Morrison: the bushfires demand a climate policy reboot



Scott Morrison’s response to the bushfires has been roundly criticised as being too slow and out of touch.
James Ross/AAP

Tony Walker, La Trobe University

Frank Jotzo, the director of the Centre for Climate and Energy Policy at Australian National University, has some constructive advice for Prime Minister Scott Morrison in a column today for the ABC: do not waste an opportunity to recalibrate his government’s approach on climate change.

Morrison should heed Jotzo’s suggestion that he and his cabinet need to “drop the old anti-climate change stance”. As Jotzo writes,

You’ve been politically locked into a no-action position, but the bushfires give you the reason to change […] You can make it your mission to protect the country from harm, an essential conservative cause.

Jotzo speaks with authority as one of the country’s foremost experts on climate reduction policies. He has a global reputation.




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Whether Morrison is capable of a course correction on climate change and, in the process, yield on an issue he has used to wedge his political opponents remains to be seen. However, he would be unwise to pretend that once the immediate bushfire danger passes and the smoke clears, the country will return to normal politically.

The nation will expect – indeed it will demand – that any government, conservative or Labor, face up to what is the new normal of a drying continent rendering human settlement increasingly vulnerable to extreme weather. Failure to do so will exact a heavy political price.

Scott Morrison’s holiday trip to Hawaii immediately came under fire from those who accused him of being out of touch with fire victims.
Steven Saphore/AAP

Morrison’s fallback positions are less defensible

The prime minister insists he has not denied there is a link between climate change and bushfires, but at best his responses on the subject have been evasive and self-serving politically.

Pressed on the issue, his fallback position is to say

I am sure you would also agree that no response by any one government anywhere in the world can be linked to one fire event.

That might be true, but it is hardly the point in the wider scheme of what measures might be adopted to address problems of a sluggish response to the bushfire emergency.

Morrison and others in his government might also go easy on claims that local opposition to hazard reduction burning in native forests contributed to the fires. This is a coded attacked on the Greens and is not supported by the evidence.

When in doubt, politically you might say, blame the Greens.




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Memo to Scott Morrison: people are fed up with politics proving to be a constraint on the development of a credible and sustainable climate policy that involves reasonable transitional steps to a low-carbon economy over time.

As such, he might also drop his claim that calls to reduce carbon emissions are “reckless”.

Where the prime minister is particularly vulnerable – this will be subject studied closely by any future commission of inquiry – lies in his refusal to meet a group of former emergency services leaders calling itself Emergency Leaders for Climate Change.

In April, the leader of the group, Greg Mullins, a former commissioner of NSW Fire and Rescue, wrote to Morrison warning him of the threat of “increasingly catastrophic extreme weather events”.

In September, this expert group wrote again to the prime minister asking for a meeting.

They received no constructive response.

Likewise, academic warnings about risks of climate-induced extreme weather events have been ignored.

In a March 2019 report for the Australian Strategic Policy Institute, ANU professor Robert Glasser called specifically for a national strategy to deal with climate disaster preparedness.

More than 500 Australians, about the same number who died in the Vietnam War, die each year from heat stress alone. The annual economic costs of natural disasters are projected to increase to A$39 billion by 2050, which is roughly equivalent to what the Australian government spends annually on defence.

Bear in mind Glasser’s report was written before these Christmas-New Year bushfire disasters.

We need to begin preparing now for this changing climate, by developing a national strategy that outlines exactly how we move on from business as usual and adopt a more responsible approach to climate disaster preparedness.

Demonstrating empathy, not political calculations

This bring us to issues surrounding the PM’s own leadership during the crisis.

Rosemary Williamson of the University of New England concluded a useful survey of Australian prime ministers’ responses to natural disasters last year with these words:

Australians will expect prime ministers to come and see for themselves, to demonstrate empathy and to instil confidence in recovery.

If these are the benchmarks for prime ministerial behaviour during a crisis brought on by disaster whether it is flood, fire or cyclone, Morrison has not lived up to these expectations.

First, he was – inexplicably – out of the country on holiday while uncontrollable fires began ravaging his home state of New South Wales.

Second, he has had trouble demonstrating reasonable empathy for victims of the fires.

And third, he has had difficulty accepting the Commonwealth had a shared responsibility for assisting the states in coping with the fallout from arguably the worst natural disaster in Australian history.

What has been most surprising is the time it has taken for Canberra to understand that such are the dimensions of this disaster that military assistance was necessary.

Weeks passed without the Australian Defence Force (ADF) being called out. The explanation for this delay is that states had not asked for military involvement, as if the out-of-control bushfires themselves respected state boundaries – or Commonwealth-state relations.

Coordination between Canberra and the states has improved in recent days, but in the early stages such cooperation left much to be desired.

In all of this, it is clear Morrison has laboured under a constraint of not wanting to antagonise the climate-sceptic right of his party by immediately conceding that global warming and bushfires are linked.

This would explain his tardiness in acknowledging the extent of the disaster.

Politically, he may well believe that climate remains an important point of difference between parties of left and right.




Read more:
Mr Morrison, I lost my home to bushfire. Your thoughts and prayers are not enough


Debate over climate – whether it is changing, and if so what to do about it – has become a culture wars issue over the years to the point where it has proved to be a useful political device for parties of the right.

As a politician of the right, Morrison would be reluctant to yield ground on issues to do with electricity prices that might benefit him politically in the future.

These are the political considerations that would be weighing in his calculations.

Morrison tours a scorched farm in Victoria last week.
James Ross/AAP

Charting a new course

However, the ground is shifting politically.

Polls indicate the environment is assuming greater importance among Australians. It is not far behind the economy and health in people’s concerns, according to an exhaustive poll conducted by the ANU’s 2019 Australian Election Study.

Among issues that will burden governments – both federal and state – over the next months will be the heavy costs associated with cleaning up the mess. All up, costs will run into the billions given the dimensions of destruction.

Inevitably, the bushfires will have an impact on economic activity in the December and March quarters. Growth is anaemic in any case, and may well become weaker as a consequence of reduced economic activity during the bushfire season.

Whatever economic fallout ensues, the political costs for the prime minister will continue to weigh heavily.

He would do himself a favour by advancing a credible climate and land management policy that ensures the country is better prepared when the next disaster strikes, as it surely will.The Conversation

Tony Walker, Adjunct Professor, School of Communications, La Trobe University

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

Climate explained: why Mars is cold despite an atmosphere of mostly carbon dioxide



The atmosphere of Mars is thin and very dry.
NASA’s Mars Reconnaissance Orbiter, CC BY-ND

Paulo de Souza, Griffith University


CC BY-ND

Climate Explained is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.

If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz

If tiny concentrations of carbon dioxide can hold enough heat to create a global warming impact on Earth, why is Mars cold? Its atmosphere is 95% carbon dioxide.

The recipe for the temperature of a planet’s surface has four major ingredients: atmospheric composition, atmospheric density, water content (from oceans, rivers and air humidity) and distance from the Sun. There are other ingredients, including seasonal effects or the presence of a magnetosphere, but these work more like adding flavour to a cake.

When we look at Earth, the balance of these ingredients makes our planet habitable. Changes in this balance can result in effects that can be felt on a planetary scale. This is exactly what is happening with the increase of greenhouse gases in the atmosphere of our planet.

Increased concentrations of carbon dioxide, methane, sulphur hexafluoride and other gases in the atmosphere have been raising the temperature of our planet’s surface gradually and will continue to do so for many years to come.




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As a consequence, places covered in ice start melting and extreme weather events become more frequent. This poses a growing challenge for us to adapt to this new reality.

Small concentration, big effect

It is surprising to realise how little the concentration of carbon dioxide (CO₂) and other greenhouse gases has to change to cause such a shift in our climate. Since the 1950s, we have raised CO₂ levels in the atmosphere by a fraction of a percent, but this is already causing several changes in our climate.

This is because CO₂ represents a tiny part of Earth’s atmosphere. It is measured in parts per million (ppm) which means that for every carbon dioxide molecule there are a million others. Its concentration is just 0.041%, but even a small percentage change represents a big change in concentration.

We can tell what Earth’s atmosphere and climate were like in the distant past by analysing bubbles of ancient air trapped in ice. During Earth’s ice ages, the concentration of carbon dioxide was around 200ppm. During the warmer interglacial periods, it hovered around 280ppm, but since the 1950s, it has continued to rise relentlessly. By 2013, CO₂ levels surpassed 400ppm for the first time in recorded history.

This graph, based on samples of air bubbles fro ice cores and direct measurements of carbon dioxide, shows the rise of atmospheric carbon dioxide since the industrial revolution.
NASA, CC BY-ND

This rise represents almost a doubling in concentration, and it clear that, in the recipe for Earth’s surface temperature, carbon dioxide and other greenhouse gases are to be used in moderation.

The role of water

Like flour for a cake, water is an important ingredient of the Earth’s surface. Water makes temperature move slowly. That’s why the temperatures in tropical rainforests does not change much, but the Sahara desert is cold at night. Earth is rich in water.

Let’s have a look at our solid planets. Mercury is the closest planet to the Sun, but it has a very thin atmosphere and is not the warmest planet. Venus is very, very hot. Its atmosphere is rich in carbon dioxide (over 96%) and it is very dense.

The atmosphere of Mars is also rich in carbon dioxide (above 96%), but it is extremely thin (1% of Earth’s atmosphere), very dry and located further away from the Sun. This combination makes the planet an incredibly cold place.

The absence of water makes the temperature on Mars change a lot. The Mars exploration rovers (Spirit at Gusev Crater and Opportunity at Meridiani Planun) experienced temperatures ranging from a few degrees Celsius above zero to minus 80℃ at night: every single Martian day, known as sol.




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Terraforming or terra fixing

One of the interesting challenges we face while building space payloads, like we do at Griffith University, is to build instruments that can withstand such a wide temperature range.

I love conversations about terraforming. This is the idea that we could fly to a planet with an unbreathable atmosphere and fix it by using some sort of machine to filter nasty gases and release good ones we need to survive, at the correct amount. That is a recurrent theme in many science fiction films, including Aliens, Total Recall and Red Planet.

I hope we can fix our own atmosphere on Earth and reduce our planet’s fever.The Conversation

Paulo de Souza, Professor, Griffith University

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

Hot as shell: birds in cooler climates lay darker eggs to keep their embryos warm


The colour and brightness of birds’ eggs plays a key role in keeping them at the right temperature.
Anne Kitzman / Shutterstock

Phill Cassey, University of Adelaide and Daniel Hanley, Long Island University Post

Birds lay eggs with a huge variety of colours and patterns, from immaculate white to a range of blue-greens and reddish browns.

The need to conceal eggs from predators is one factor that gives rise to all kinds of camouflaged and hard-to-spot appearances.

Yet our research, published today in Nature Ecology & Evolution, shows that climate is even more important.

Dark colours play a crucial role in regulating temperatures in many biological systems. This is particularly common for animals like reptiles, which rely on environmental sources of heat to keep themselves warm.




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Darker colours absorb more heat from sunlight, and animals with these colours are more commonly found in colder climates with less sunlight. This broad pattern is known as Bogert’s rule.

Birds’ eggs are useful for studying this pattern because the developing embryo can only survive in a narrow range of temperatures. But eggs cannot regulate their own temperature and, in most cases, the parent does it by sitting atop the clutch of eggs.

In colder environments, where the risk of predators is lower and the risk of chilling in cold temperatures is greater, parents spend less time away from the nest.

We predicted that if eggshell colour does play an important role in regulating the temperature of the embryo, birds living in colder environments should have darker eggs.

The average colour of eggshells in different areas around the world.
Wisocki et al. 2019 ‘The global distribution of avian eggshell colours suggests a thermoregulatory benefit of darker pigmentation’, Nature Ecology & Evolution, Author provided

To test the prediction, we measured eggshell brightness and colour for 634 species of birds. That’s more than 5% of all bird species, representing 36 of the 40 large groups of species called orders.

We mapped these within each species’ breeding range and found that eggs in the coldest environments (those with the least sunlight) were significantly darker. This was true for all nest types.

We also conducted experiments using domestic chicken eggs to confirm that darker eggshells heated up more rapidly and maintained their incubation temperatures for longer than white eggshells.




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It isn’t easy being blue – the cost of colour in fairy wrens


Our results show that darker eggshells are found in places with less sunlight and lower temperatures, and that these darker colours may help keep the developing embryo warm.

How future climate change will affect eggshell appearance, as well as the timing of reproduction and incubation behaviour, will be an important and fruitful avenue for future research.The Conversation

Phill Cassey, Assoc Prof in Invasion Biogeography and Biosecurity, University of Adelaide and Daniel Hanley, Assistant Professor, Long Island University Post

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

Climate explained: how volcanoes influence climate and how their emissions compare to what we produce



Rapid and voluminous volcanic eruptions around 252 million years ago can be linked with a mass extinction event.
from http://www.shutterstock.com, CC BY-ND

Michael Petterson, Auckland University of Technology


CC BY-ND

Climate Explained is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.

If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz

Everyone is going on about reducing our carbon footprint, zero emissions, planting sustainable crops for biodiesel etc. Is it true what the internet posts say that a volcano eruption for a few weeks will make all our efforts null and void?

The pretext to this question is understandable. The forces of nature are so powerful and operate at such a magnitude that human efforts to influence our planet may seem pointless.

If one volcanic eruption could alter our climate to such a degree that our world rapidly becomes an “icehouse” or a “hothouse”, then perhaps our efforts to mitigate anthropogenic climate change are a waste of time?

To answer this question we need to examine how our atmosphere formed and what geological evidence there is for volcanically induced climate change. We also need to look at recent data comparing volcanic and human greenhouse gas emissions.

There is evidence for catastrophic climate change from very large, protracted volcanic eruptions in the geological record. But in more recent times we have learned that volcanic emissions can lead to shorter-term cooling and longer-term warming. And the killer-punch evidence is that human-induced greenhouse gas emissions far exceed those of volcanic activity, particularly since 1950.

Forging Earth’s atmosphere

Let’s go back to first principles and look at where our atmosphere came from. Earth is 4.56 billion years old. The common consensus is that Earth’s atmosphere results from three main processes:

1. remnants of primordial solar nebula gases from the time of earliest planet formation

2. outgassing of the Earth’s interior from volcanic and related events

3. the production of oxygen from photosynthesis.

There have also been contributions over time from comets and asteroid collisions. Of these processes, internal planetary degassing is the most important atmosphere-generating process, particularly during the first of four aeons of Earth’s history, the hot Hadean.

Volcanic eruptions have contributed to this process ever since and provided the bulk of our atmosphere and, therefore, the climate within our atmosphere.

Next is the question of volcanic eruptions and their influence on climate. Earth’s climate has changed over geological time. There have been periods of an ice-free “hothouse Earth”. Some argue that sea levels were 200 to 400 metres higher than today and a significant proportion of Earth’s continents were submerged beneath sea level.

At other times, during a “snowball Earth”, our planet was covered in ice even at the equator.




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Climate explained: why we won’t be heading into an ice age any time soon


What contribution have volcanic eruptions made to this variation in climate? As an example of a major influence, some scientists link mass extinctions to major volcanic eruption events.

The most famous such association is that of the eruption of volcanoes that produced the Siberian Traps. This is a large region of thick volcanic rock sequences, some 2.5 to 4 million square kilometres, in an area in Russia’s eastern provinces. Rapid and voluminous volcanic eruptions around 252 million years ago released sufficient quantities of sulphate aerosols and carbon dioxide to trigger short-duration volcanic winters, and long-duration climate warming, over a period of 10s of thousands of years.

The Siberian Trap eruptions were a causal factor in Earth’s largest mass extinction event (at the end of the Permian period), when 96% of Earth’s marine species and 70% of terrestrial life ceased to exist.

Natural climate change over past 100 million years

Geological evidence indicates that natural processes can indeed radically change Earth’s climate. Most recently (in geological terms), over the past 100 million years ocean bottom waters have cooled, sea levels fallen and ice has advanced. Within this period there have also been spells of a hotter Earth, most likely caused by (natural) rapid releases in greenhouse gases.

Homo sapiens has evolved during the past few million years largely during an ice age when up to two-kilometre-thick ice sheets covered large areas of the northern continents and sea levels were over 100 metres lower than today. This period ended 10,000 years ago when our modern interglacial warmer period began.

Astronomical cycles that lead to climate variations are well understood – for example, the Milankovitch cycles, which explain variations in Earth’s orbit around the sun, and the periodic nodding/swaying of our Earth’s axis. All of the geological and tectonic causes for this general longer-term Earth cooling are less well understood. Hypotheses include contributions from volcanoes and processes linked to the rise of the Himalayas and Tibet (from 55 million years ago).




Read more:
Climate explained: why we need to cut emissions as well as prepare for impacts


Specific volcanic eruptions and climate impacts

Researchers have studied specific volcanic eruptions and climate change. Mount Pinatubo (Philippines) produced one of the larger eruptions of recent times in 1991, releasing 20 million tonnes of sulphur dioxide and ash particles into the stratosphere.

These larger eruptions reduce solar radiation reaching the Earth’s surface, lower temperatures in the lower troposphere, and change atmospheric circulation patterns. In the case of Pinatubo, global tropospheric temperatures fell by up to 4°C, but northern hemisphere winters warmed.

Volcanoes erupt a mix of gases, including greenhouse gases, aerosols and gases that can react with other atmospheric constituents. Atmospheric reactions with volcanic gases can rapidly produce substances such as sulphuric acid (and related sulphates) that act as aerosols, cooling the atmosphere.

Longer-term additions of carbon dioxide have warming impacts. Larger-scale volcanic eruptions, whose ash clouds reach stratospheric levels, have the biggest climatic impacts: the larger and more prolonged the eruption period, the larger the impacts.

These types of eruptions are thought to have been a partial cause for the Little Ice Age period, a global cooling event of about 0.5°C that lasted from the 15th to the late 19th century. Super volcanoes such as Yellowstone (USA), Toba (Indonesia) and Taupo (New Zealand) can, theoretically, produce very large-volume eruptions that have significant climate impacts, but there is uncertainty over how long these eruptions influence climate.

Perhaps the strongest evidence for answering whether our (human) emissions or volcanoes have a stronger influence on climate lies in the scale of greenhouse gas production. Since 2015, global anthropogenic carbon dioxide emissions have been around 35 to 37 billion tonnes per year. Annual volcanic CO₂ emissions are around 200 million tonnes.

In 2018, anthropogenic CO₂ emissions were 185 times higher than volcanic emissions. This is an astounding statistic and one of the factors persuading some geologists and natural scientists to propose a new geological epoch called the Anthropocene in recognition that humans are exceeding the impacts of many natural global processes, particularly since the 1950s.

There is evidence that volcanoes have strongly influenced climate on geological time scales, but, since 1950 in particular, it is Homo sapiens who has had by far the largest impact on climate. Let us not give up our CO₂ emission-reduction aspirations. Volcanoes may not save the day.The Conversation

Michael Petterson, Professor of Geology, Auckland University of Technology

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