Climate explained: when Antarctica melts, will gravity changes lift up land and lower sea levels?


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Robert McLachlan, Massey University


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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


I’ve heard the gravity changes when Antarctica melts will lower the seas around New Zealand. Will that save us from sea level rise?

The gravitational changes when Antarctica melts do indeed affect sea levels all over the world — but not enough to save New Zealand from rising seas.

The ice ages and their effects on sea level, geology, flora and fauna were topics of intense scientific and public interest all through the 19th century. Here’s how James Croll explained the “gravity effect” of melting ice in his 1875 book Climate and Time in their Geologic Relations:

Let us now consider the effect that this condition of things would have upon the level of the sea. It would evidently tend to produce an elevation of the sea-level on the northern hemisphere in two ways. First, the addition to the sea occasioned by the melting of the ice from off the Antarctic land would tend to raise the general level of the sea. Secondly, the removal of the ice would also tend to shift the earth’s centre of gravity to the north of its present position – and as the sea must shift along with the centre, a rise of the sea on the northern hemisphere would necessarily take place.

His back-of-the-envelope calculation suggested the effect on sea level from ice melting in Antarctica would be about a third bigger than average in the northern hemisphere and a third smaller in the south.

A more detailed mathematical study by Robert Woodward in 1888 has falling sea level as far as 2000km from Antarctica, but still rising by a third more than average in the north.




Read more:
Ancient Antarctic ice melt caused extreme sea level rise 129,000 years ago – and it could happen again


Sea-level fingerprints

Woodward’s method is the basis of determining what is now called the “sea-level fingerprint” of melting ice. Two other factors also come into play.

  1. The elasticity of the earth’s surface means the land will bounce up when it has less ice weighing it down. This pushes water away.
  2. If the ice is not at the pole, its melting shifts the south pole (the axis of rotation), redistributing water.

Combining these effects gives the sea-level fingerprints of one metre of sea-level rise from either the West Antarctic Ice Sheet (WAIS) and Greenland (GIS), as shown here:

Red areas get more than the average sea level rise, blue areas get less.
Fingerprints of sea-level change following melting of ice from West Antartica (WAIS) and Greenland (GIS) equivalent to one metre of sea-level rise on average. Red areas get up to 40% more than the average sea-level rise, blue areas get less.
Author provided, CC BY-SA

Woodward’s method from 1888 holds up pretty well – some locations in the northern hemisphere can get a third more than the average sea level rise. New Zealand gets a little bit below the average effect from Antarctica, and a little more than average from Greenland. Overall, New Zealand can expect slightly higher than average sea level rise.

Combining the sea-level fingerprints of all known sources of melting ice, together with other known changes of local land level such as subsidence and uplift, gives a good fit to the observed pattern of sea level rise around the world. For example, sea level has been falling near West Antarctica, due to the gravity effect.

Changes in sea level around the world, 1993-2019

NOAA

Sea-level rise is accelerating, but the future rate is uncertain

The global average rise in sea level is 110mm for 1900-1993 and 100mm for 1993–2020. The recent acceleration is mostly due to increased thermal expansion of the top two kilometres of the oceans (warm water is less dense and expands) and increased melting of Greenland.

But the Gravity Recovery and Climate Experiment satellite has revealed the melting of Antarctica has accelerated by a factor of five in recent decades. Future changes in Antarctica represent a major source of uncertainty when trying to forecast sea levels.

Much of West Antarctica lies below sea level and is potentially subject to an instability in which warming ocean water melts the ice front from below. This would cause the ice sheet to peel off the ocean floor, accelerating the flow of the glacier towards the sea.

In fact, this has been directly observed, both in the location of glacial “grounding lines”, some of which have retreated by tens of kilometres in recent decades, and most recently by the Icefin submersible robot which visited the grounding line of the Thwaites Glacier, 2000km east of Scott Base, and found the water temperature to be 2℃ above the local freezing point.




Read more:
If warming exceeds 2°C, Antarctica’s melting ice sheets could raise seas 20 metres in coming centuries


The big question is whether this instability has been irreversibly set into motion. Some glaciologists say it has, but the balance of opinion, summarised by the IPCC’s report on the cryosphere, is that:

Observed grounding line retreat … is not definitive proof that Marine Ice Sheet Instability is underway. Whether unstable West Antarctic Ice Sheet retreat has begun or is imminent remains a critical uncertainty.

The IPCC special report on 1.5℃ concluded that “these instabilities could be triggered at around 1.5℃ to 2℃ of global warming”.

What’s in store for New Zealand

Predictions for New Zealand range from a further 0.46 metres of sea-level rise by 2100 (under a low-emission scenario, with warming kept under 2℃) to 1.05 metres (under a high-emission scenario).

A continued rise in sea levels over future centuries may be inevitable — there are 66m of sea level rise locked up in ice at present — but the rate will depend on how fast we can reduce emissions.

A five-year, NZ$7m research project, NZ SeaRise, is now underway, seeking to improve predictions of sea-level rise out to 2100 and beyond and their implications for local planning.The Conversation

Robert McLachlan, Professor in Applied Mathematics, Massey University

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

Paying Australia’s coal-fired power stations to stay open longer is bad for consumers and the planet


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Daniel J Cass, University of Sydney; Joel Gilmore, Griffith University, and Tim Nelson, Griffith UniversityAustralian governments are busy designing the nation’s transition to a clean energy future. Unfortunately, in a misguided effort to ensure electricity supplies remain affordable and reliable, governments are considering a move that would effectively pay Australia’s old, polluting coal-fired power stations to stay open longer.

The measure is one of several options proposed by the Energy Security Board (ESB), the chief energy advisor to Australian governments on electricity market reform. The board on Friday released a vision to redesign the National Electricity Market as it transitions to clean energy.

The key challenges of the transition are ensuring it is smooth (without blackouts) and affordable, as coal and gas generators close and are replaced by renewable energy.

The redesign has been two years in the making. The ESB has done a very good job of identifying key issues, and most of its recommendations are sound. But its option to change the way electricity generators and retailers strike contracts for electricity, if adopted, would be highly counterproductive – bad both for consumers and for climate action.

Electricity lines at sunset
One proposed reform to Australia’s electricity market would be bad for consumers and climate action.
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The energy market dilemma

The National Electricity Market (NEM) covers every Australian jurisdiction except Western Australia and the Northern Territory. It comprises electricity generators, transmission and distribution networks, electricity retailers, customers and a financial market where electricity is traded.

Electricity generators in the NEM comprise older, polluting technology such as gas- and coal-fired power, and newer, clean forms of generation such as wind and solar. Renewable energy, which makes up about 23% of our electricity mix, is now cheaper than energy from coal and gas.

Wind and solar energy is “variable” – only produced when the sun is shining and the wind is blowing. Technology such as battery storage is needed to smooth out renewable energy supplies and make it “dispatchable”, meaning it can be delivered on demand.

Some say coal generators, which supply dispatchable electricity, are the best way to ensure reliable and affordable electricity. But Australia’s coal-fired power stations, some of which are more than 40 years old, are becoming more prone to breakdowns – and so less reliable and more expensive – as they age. This has led to some closing suddenly.

Without a clear national approach to emissions targets, there’s a risk these sudden closures will occur again.




Read more:
Explainer: what is the electricity transmission system, and why does it need fixing?


Wind farm near coast
Wind and solar energy is variable.
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So what’s proposed?

To address reliability concerns, the ESB has proposed an option known as the “physical retailer reliability obligation”.

In a nutshell, the change would require electricity retailers to negotiate contracts for a certain amount of “dispatchable” electricity from specific generators for times of the year when reliability is a concern, such as the peak weeks of summer when lots of people use air conditioning.

Currently, the Australian Energy Market Operator has reserve electricity measures it can deploy when market supply falls short.

But under the new obligation, all retailers would also have to enter contracts for dispatchable supply. This would likely require buying electricity from the coal generators that dominate the market. This provides a revenue source enabling these coal plants to remain open even when cheaper renewable energy makes them unprofitable.

The ESB says without the change, the closure of coal generators will be unpredictable or “disorderly”, creating price shocks and reliability risks.

hand turns off light switch in bedroom
The ESWB says the recommendation would address concerns over electricity reliability.
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A big risk

Even the ESB concedes the recommendation comes with considerable risks. In particular, the board says it may:

  • impose increased barriers to retail competition and product innovation
  • lead to possible overcompensation of existing coal and gas generators.

In short, the policy could potentially lock in increasingly unreliable, ageing coal assets, stall new investment in new renewable energy storage such as batteries and pumped hydro and increase market concentration.

It could also push up electricity prices. Electricity retailers are likely to pass on the cost of these new electricity contracts to consumers, no matter how much energy that household or business actually used.

The existing market already encourages generators to provide reliable supply – and applies strong penalties if they don’t. And in fact, the NEM experiences reliability issues for an average of just one minute per year. It would appear little could be added to the existing market design to make generators more reliable than they are.

Finally, the market is dominated by three large “gentailers” – AGL, Energy Australia and Origin – which own both generators and the retail companies that sell electricity. The proposed change would disadvantage smaller electricity retailers, which in many cases would be forced to buy electricity from generators owned by their competitors.

Australia’s gentailers are heavily invested in coal power stations. The proposed change would further concentrate their market power while propping up coal.




Read more:
‘Failure is not an option’: after a lost decade on climate action, the 2020s offer one last chance


warning sign on fence
The proposed change brings a raft of risks to the electricity market.
Kelly Barnes/AAP

What governments should do

If coal-fired power stations are protected from competition, it will deter investment in cleaner alternatives. The recommendation, if adopted, would delay decarbonisation and put Australia further at odds with our international peers on climate policy.

The federal and state governments must work together to develop a plan for electricity that facilitates clean energy investment while controlling costs for consumers.

The plan should be coordinated across the states. Without this, we risk creating a sharper shock later, when climate diplomacy requires the planned retirement of coal plants. Other nations have acknowledged the likely demise of coal, and it’s time Australia caught up.




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The Conversation


Daniel J Cass, Research Affiliate, Sydney Business School, University of Sydney; Joel Gilmore, Associate Professor, Griffith University, and Tim Nelson, Associate Professor of Economics, Griffith University

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

The 1.5℃ global warming limit is not impossible – but without political action it soon will be


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Bill Hare, Potsdam Institute for Climate Impact Research; Carl-Friedrich Schleussner, Humboldt University of Berlin; Joeri Rogelj, Imperial College London, and Piers Forster, University of LeedsLimiting global warming to 1.5℃ this century is a central goal of the Paris Agreement. In recent months, climate experts and others, including in Australia, have suggested the target is now impossible.

Whether Earth can stay within 1.5℃ warming involves two distinct questions. First, is it physically, technically and economically feasible, considering the physics of the Earth system and possible rates of societal change? Science indicates the answer is “yes” – although it will be very difficult and the best opportunities for success lie in the past.

The second question is whether governments will take sufficient action to reduce greenhouse gas emissions. This answer depends on the ambition of governments, and the effectiveness of campaigning by non-government organisations and others.

So scientifically speaking, humanity can still limit global warming to 1.5°C this century. But political action will determine whether it actually does. Conflating the two questions amounts to misplaced punditry, and is dangerous.

Women holds sign at climate march
Staying within 1.5℃ is scientifically possible, but requires government ambition.
Erik Anderson/AAP

1.5℃ wasn’t plucked from thin air

The Paris Agreement was adopted by 195 countries in 2015. The inclusion of the 1.5℃ warming limit came after a long push by vulnerable, small-island and least developed countries for whom reaching that goal is their best chance for survival. The were backed by other climate-vulnerable nations and a coalition of high-ambition countries.

The 1.5℃ limit wasn’t plucked from thin air – it was informed by the best available science. Between 2013 and 2015, an extensive United Nations review process determined that limiting warming to 2℃ this century cannot avoid dangerous climate change.

Since Paris, the science on 1.5℃ has expanded rapidly. An Intergovernmental Panel on Climate Change (IPCC) report in 2018 synthesised hundreds of studies and found rapidly escalating risks in global warming between 1.5℃ and 2℃.

The landmark report also changed the climate risk narrative away from a somewhat unimaginable hothouse world in 2100, to a very real threat within most of our lifetimes – one which climate action now could help avoid.

The message was not lost on a world experiencing ever more climate impacts firsthand. It galvanised an unprecedented global youth and activist movement demanding action compatible with the 1.5℃ limit.

The near-term benefits of stringent emissions reduction are becoming ever clearer. It can significantly reduce near-term warming rates and increase the prospects for climate resilient development.

Firefighter battles blaze
The urgency of climate action is not lost on those who’ve experienced its effects firsthand.
Evan Collins/AAP

A matter of probabilities

The IPCC looked extensively at emission reductions required to pursue the 1.5℃ limit. It found getting on a 1.5℃ track is feasible but would require halving global emissions by 2030 compared to 2010 and reaching net-zero emissions by mid-century.

It found no published emission reduction pathways giving the world a likely (more than 66%) chance of limiting peak warming this century to 1.5℃. But it identified a range of pathways with about a one-in-two chance of achieving this, with no or limited overshoot.

Having about a one-in-two chance of limiting warming to 1.5℃ is not ideal. But these pathways typically have a greater than 90% chance of limiting warming to well below 2℃, and so are fully compatible with the overall Paris goal.




Read more:
Spot the difference: as world leaders rose to the occasion at the Biden climate summit, Morrison faltered


Scott Morrison holding a lump of coal in Parliament
Staying under 1.5℃ warming requires political will.
Lukas Coch/AAP

Don’t rely on carbon budgets

Carbon budgets show the amount of carbon dioxide that can be emitted for a given level of global warming. Some point to carbon budgets to argue the 1.5℃ goal is now impossible.

But carbon budget estimates are nuanced, and not a suitable way to conclude a temperature level is no longer possible.

The carbon budget for 1.5℃ depends on several factors, including:

  • the likelihood with which warming will be be halted at 1.5℃
  • the extent to which non-CO₂ greenhouse emissions such as methane are reduced
  • uncertainties in how the climate responds these emissions.

These uncertainties mean strong conclusions cannot be drawn based on single carbon budget estimate. And, at present, carbon budgets and other estimates do not support any argument that limiting warming to 1.5℃ is impossible.

Keeping temperature rises below 1.5℃ cannot be guaranteed, given the history of action to date, but the goal is certainly not impossible. As any doctor embarking on a critical surgery would say about a one-in-two survival chance is certainly no reason not to do their utmost.

Wind farm
Staying below 1.5°C is a difficult, but not impossible, task.
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Closer than we’ve ever been

It’s important to remember the special role the 1.5℃ goal plays in how governments respond to climate change. Five years on from Paris, and the gains of including that upper ambition in the agreement are showing.

Some 127 countries aim to achieve net-zero emissions by mid-century at the latest – something considered unrealistic just a few years ago. If achieved globally and accompanied by stringent near-term reductions, the actions could be in line with 1.5℃.

If all these countries were to deliver on these targets in line with the best-available science on net zero, we may have a one-in-two chance of limiting warming this century to 2.1℃ (but a meagre one-in-ten that it is kept to 1.5°C). Much more work is needed and more countries need to step up. But for the first time, current ambition brings the 1.5℃ limit within striking distance.

The next ten years are crucial, and the focus now must be on governments’ 2030 targets for emissions reduction. If these are not set close enough to a 1.5℃-compatible emissions pathway, it will be increasingly difficult to reach net-zero by 2050.

The United Kingdom and European Union are getting close to this pathway. The United States’ new climate targets are a major step forward, and China is moving in the right direction. Australia is now under heavy scrutiny as it prepares to update its inadequate 2030 target.

The UN wants a 1.5℃ pathway to be the focus at this year’s COP26 climate summit in Glasgow. The stakes could not be higher.




Read more:
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The Conversation


Bill Hare, Director, Climate Analytics, Adjunct Professor, Murdoch University (Perth), Visiting scientist, Potsdam Institute for Climate Impact Research; Carl-Friedrich Schleussner, Research Group Leader, Humboldt University of Berlin; Joeri Rogelj, Director of Research and Lecturer – Grantham Institute Climate Change & the Environment, Imperial College London, and Piers Forster, Professor of Physical Climate Change; Director of the Priestley International Centre for Climate, University of Leeds

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

Watching a coral reef die as climate change devastates one of the most pristine tropical island areas on Earth


Sam Purkis, University of MiamiThe Chagos Archipelago is one of the most remote, seemingly idyllic places on Earth. Coconut-covered sandy beaches with incredible bird life rim tropical islands in the Indian Ocean, hundreds of miles from any continent. Just below the waves, coral reefs stretch for miles along an underwater mountain chain.

It’s a paradise. At least it was before the heat wave.

When I first explored the Chagos Archipelago 15 years ago, the underwater view was incredible. Schools of brilliantly colored fish in blues, yellows and oranges darted among the corals of a vast, healthy reef system. Sharks and other large predators swam overhead. Because the archipelago is so remote and sits in one of the largest marine protected areas on the planet, it has been sheltered from industrial fishing fleets and other activities that can harm the coastal environment.

But it can’t be protected from climate change.

A diver carries a plastic pipe for measuring while swimming over a variety of corals
A diver documents the coral reefs in the Chagos Archipelago.
Khaled bin Sultan Living Oceans Foundation

In 2015, a marine heat wave struck, harming coral reefs worldwide. I’m a marine biologist at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science, and I was with a team of researchers on a 10-year global expedition to map the world’s reefs, led by the Khaled bin Sultan Living Oceans Foundation. We were wrapping up our work in the Chagos Archipelago at the time. Our report on the state of the reefs there was just published in spring 2021.

As the water temperature rose, the corals began to bleach. To the untrained eye, the scene would have looked fantastic. When the water heats up, corals become stressed and they expel the tiny algae called dinoflagellates that live in their tissue. Bleaching isn’t as simple as going from a living coral to a bleached white one, though. After they expel the algae, the corals turn fluorescent pinks and blues and yellows as they produce chemicals to protect themselves from the Sun’s harmful rays. The entire reef was turning psychedelic colors.

Two bright pink coral mounds
Just before they turned white, the corals turned abnormally bright shades.
Phil Renaud/Khaled bin Sultan Living Oceans Foundation

That explosion of color is rare, and it doesn’t last long. Over the following week, we watched the corals turn white and start to die. It wasn’t just small pieces of the reef that were bleaching – it was happening across hundreds of square miles.

What most people think of as a coral is actually many tiny colonial polyps that build calcium carbonate skeletons. With their algae gone, the coral polyps could still feed by plucking morsels out of the water, but their metabolism slows without the algae, which provide more nutrients through photosynthesis. They were left desperately weakened and more vulnerable to diseases. We could see diseases taking hold, and that’s what finished them off.

We were witnessing the death of a reef.

Rising temperatures increase the heat wave risk

The devastation of the Chagos Reef wasn’t happening in isolation.

Over the past century, sea surface temperatures have risen by an average of about 0.13 degrees Celsius (0.23 F) per decade as the oceans absorb the vast majority of greenhouse gas emissions from human activities, largely from the burning of fossil fuels. The temperature increase and changing ocean chemistry affects sea life of all kinds, from deteriorating the shells of oysters and tiny pteropods, an essential part of the food chain, to causing fish populations to migrate to cooler water.

Corals can become stressed when temperatures around them rise just 1 C (1.8 F) above their tolerance level. With water temperature elevated from global warming, even a minor heat wave can become devastating.

In 2015, the ocean heat from a strong El Niño event triggered the mass bleaching in the Chagos reefs and around the world. It was the third global bleaching on record, following events in 1998 and 2010.

Bleaching doesn’t just affect the corals – entire reef systems and the fish that feed, spawn and live among the coral branches suffer. One study of reefs around Papua New Guinea in the southwest Pacific found that about 75% of the reef fish species declined after the 1998 bleaching, and many of those species declined by more than half.

Research shows marine heat waves are now about 20 times more likely than they were just four decades ago, and they tend to be hotter and last longer. We’re at the point now that some places in the world are anticipating coral bleaching every couple of years.

That increasing frequency of heat waves is a death knell for reefs. They don’t have time to recover before they get hit again.

Where we saw signs of hope

During the Global Reef Expedition, we visited over 1,000 reefs around the world. Our mission was to conduct standardized surveys to assess the state of the reefs and map the reefs in detail so scientists could document and hopefully respond to changes in the future. With that knowledge, countries can plan more effectively to protect the reefs, important national resources, providing hundreds of billions of dollars a year in economic value while also protecting coastlines from waves and storms.

We saw damage almost everywhere, from the Bahamas to the Great Barrier Reef.

Some reefs are able to survive heat waves better than others. Cooler, stronger currents, and even storms and cloudier areas can help prevent heat building up. But the global trend is not promising. The world has already lost 30% to 50% of its reefs in the last 40 years, and scientists have warned that most of the remaining reefs could be gone within decades.

Diver with large sea turtle swimming over corals.
The author, Sam Purkis, dives near a hawksbill turtle in the Chagos Archipelago.
Derek Manzello/Khaled bin Sultan Living Oceans Foundation

While we see some evidence that certain marine species are moving to cooler waters as the planet warms, a reef takes thousands of years to establish and grow, and it is limited by geography.

In the areas where we saw glimmers of hope, it was mostly due to good management. When a region can control other harmful human factors – such as overfishing, extensive coastal development, pollution and runoff – the reefs are healthier and better able to handle the global pressures from climate change.

Establishing large marine protected areas is one of the most effective ways I’ve seen to protect coral reefs because it limits those other harms.

The Chagos marine protected area covers 640,000 square kilometers (250,000 square miles) with only one island currently inhabited – Diego Garcia, which houses a U.S. military base. The British government, which created the marine protected area in 2010, has been under pressure to turn over control of the region to the country of Mauritius, where former Chagos residents now live and which won a challenge over it in the International Court of Justice in 2020. Whatever happens with jurisdiction, the region would benefit from maintaining a high level of marine protection.

A warning for other ecosystems

The Chagos reefs could potentially recover – if they are spared from more heat waves. Even a 10% recovery would make the reefs stronger for when the next bleaching occurs. But recovery of a reef is measured in decades, not years.

So far, research missions that have returned to the Chagos reefs have found only meager recovery, if any at all.

We knew the reefs weren’t doing well under the insidious march of climate change in 2011, when the global reef expedition started. But it’s nothing like the intensity of worry we have now in 2021.

Coral reefs are the canary in the coal mine. Humans have collapsed other ecosystems before through overfishing, overhunting and development, but this is the first unequivocally tied to climate change. It’s a harbinger of what can happen to other ecosystems as they reach their survival thresholds.

This story is part of Oceans 21

Our series on the global ocean opened with five in-depth profiles. Look for new articles on the state of our oceans in the lead-up to the U.N.‘s next climate conference, COP26. The series is brought to you by The Conversation’s international network.The Conversation

Sam Purkis, Professor and Chair of the Department of Marine Sciences, University of Miami

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

More people die in winter than summer, but climate change may see this reverse


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Ivan Charles Hanigan, University of Sydney; Alistair Woodward, University of Auckland, and Keith DearClimate change not only poses enormous dangers to the planet, but also harms human health. In our study published today, we show some of the first evidence climate change has had observable impacts on Australians’ health between 1968 and 2018.

We found long-term heating is associated with changed seasonal balance of deaths in Australia, with relatively more deaths in summer months and relatively fewer deaths in winter months over recent decades.

Our findings can be explained by the gradual global warming associated with climate change. Over the 51 years of our study, annual average temperatures increased by more than 1°C in Australia. The last decade (2011 to 2020) was the hottest in the country’s recorded history.

If we continue on this trajectory, we’re likely to see many more climate-related deaths in the years to come.

What we did and found

Using the Australian Institute of Health and Welfare, the Australian Bureau of Statistics and other sources, we gathered mortality data for people aged 55 and over between 1968 and 2018. We then looked at deaths in summer compared to winter in each year.

We found that in 1968 there were approximately 73 deaths in summer for every 100 deaths in winter. By 2018, this had risen to roughly 83 deaths in summer for every 100 deaths in winter.

The same trend, albeit of varying strength, was evident in all states of Australia, among all age groups over 55, in females and males, and in the three broad causes of death we looked at (respiratory, heart and renal diseases).

Elderly woman coughing with blanket over her
Historically, winter death rates have tended to be higher than in summer. But this is changing as our planet warms.
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Hot and cold weather can have a variety of direct and indirect effects on our health. Winter death rates generally exceed those in summer months because infectious diseases, like influenza, tend to circulate more in winter. Meanwhile, heat stress can exacerbate chronic health conditions including heart disease and kidney disease, particularly for older adults.

But the gap between cold-related deaths and heat-related deaths appears to be narrowing. And when we compared deaths in the hottest summers with the coldest winters, we found particularly warm years increase the likelihood of seasonal mortality ratios approaching 1 to 1 (meaning equal deaths in summer and winter).

With summers expected to become hotter, we believe this is an early indication of the effects of climate change in the future.




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Our research is unique

Globally, our study is one of very few that directly shows the health impacts of climate change. Most other studies examine the effects of past weather or climate conditions on health and extrapolate these into the future based on projected climate change scenarios, with associated uncertainties. For example, demographic characteristics of the population are likely to change over time.

Climate change occurs slowly, so typically, we need at least 30–50 years of records to accurately show how climate change is affecting health. Suitable health information is seldom available for such periods due to a variety of challenges in collecting electronic health data (especially in low- and middle-income countries).

Further, long-term health trends can be influenced by numerous non-climate related factors, such as improvements in health care.

In our study, we used Australian mortality records that have been collected with remarkable consistency of detail and quality over the last half century. And by focusing on the ratio of summer to winter deaths within each year, we avoid possible confounding associated with, say, improvements to health care.




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However, we were unable to consider some issues such as the different climate trends in small areas within each state/territory, or the effects of changing temperatures on different occupation groups, such as construction workers.

Our data also don’t allow us to account for the possible effects of people’s adaptation to warmer temperatures in the future.

Dry, cracked riverbed
Summer deaths will almost certainly increase in the years to come.
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Looking ahead

The changing ratio of summer to winter deaths has previously been identified as a possible warning sign of the impact of climate change on human health.

In one study on the topic, the authors found Australia may initially experience a net reduction in temperature-related deaths. That is, increased deaths from heat during summer would be offset by fewer deaths in winter, as winters become more mild.

However, they predict this pattern would reverse by mid-century under the business-as-usual emissions scenario, with increases in heat-related deaths outweighing decreases in cold-related deaths over the long term.

Our findings support these worrying predictions. If warming trends continue, it’s almost certain summer deaths will increase, and come to dominate the burden of temperature-related deaths in Australia.

We found the speed of change in the ratio of summer to winter deaths was fastest in the hottest years within each decade. This strengthens our conclusion we’re observing an effect of long-term climate change.




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Besides helping to answer the question, “does climate change affect human health?”, we believe our findings should inform planning for climate change mitigation and adaptation. The implications are considerable for the planning of hospital services and provision of health care, as well as for emergency services, housing, energy supply, holiday periods and bushfire disaster preparedness.The Conversation

Ivan Charles Hanigan, Data Scientist (Epidemiology), University of Sydney; Alistair Woodward, Professor, School of Population Health, University of Auckland, and Keith Dear, Adjunct Professor of Public Health

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

Spot the difference: as world leaders rose to the occasion at the Biden climate summit, Morrison faltered


Lesley Hughes, Macquarie University and Will Steffen, Australian National UniversityPrime Minister Scott Morrison overnight addressed a much anticipated virtual climate summit convened by US President Joe Biden, claiming future generations “will thank us not for what we have promised, but what we deliver”.

But what will his government actually deliver?

Morrison’s speech was notable for its stark lack of ambition and a defensive tone at odds with the urgent, front-footed approach of other world leaders. He resisted the peer pressure to enter the global fold on climate action by setting clear goals, saying Australia made only “bankable” emissions-reduction commitments.

Morrison instead pointed to Australia’s “transformative technology targets”. As we will explain below, those targets are small, vague and certainly not “bankable”. And the spending commitments pale in comparison to the past and future cost of extreme weather in Australia.

Expectations of Australia heading into the summit were low – a fact perhaps reflected in the summit’s agenda. Morrison’s address was way down in the running order – he was 21st of 27 speakers. Biden was reportedly not in the room when Morrison spoke. And in an unfortunate glitch, Morrison’s microphone was on mute at the start of his speech.

The summit did deliver some major gains. There was palpable relief as Biden brought the US back to the table on global climate efforts, committing to an emissions-reduction target twice the ambition of Australia’s. Other nations including Japan, Canada and Britain also outlined major new commitments.

But sadly for Australians, the summit revealed the stark contrast in climate policy leadership between Morrison and his international peers.

Scott Morrison in front of Sydney harbour backdrop and Australian flags
The contrast on climate policy leadership between Scott Morrison and Joe Biden was on display at the summit.
Mick Tsikas/AAP

The world steps up

Biden opened the summit by emphasising the urgent need to keep global warming below 1.5℃ This century. Failing to do so, he said, would bring:

More frequent and intense fires, floods, droughts, heat waves, and hurricanes tearing through communities, ripping away lives and livelihoods, increasingly dire impacts to our public health […] We can’t resign ourselves to that future. We have to take action, all of us.

Biden committed the US to a 50-52% emissions reduction by 2030 compared with 2005 levels. Other notable emissions-reduction pledges included:

There were hopes Morrison would use the summit to announce Australia would finally join more than 100 countries to set an emissions target of net-zero by 2050. (Australia’s current emissions trajectory has us on track to get to net-zero in the year 2167).

But Morrison dashed those hopes early, telling world leaders: “For Australia, it is not a question of if or even by when for net-zero, but importantly how”.

He pointed to the government’s Technology Investment Roadmap, including A$20 billion to bring down the cost of clean hydrogen, green steel, energy storage and carbon capture. He also spoke of a goal to produce clean hydrogen for A$2 a kilogram, and his dream that Australia’s hydrogen industry would one day rival the scale of California’s Silicon Valley.




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Homes with solar panels on roof
Morrison spruiked Australia’s high uptake of rooftop solar.
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Will technology save us? Not likely

Earlier this week, Morrison set the scene for his address by announcing a suite of technology funding commitments. Let’s take a closer look at them.

On Wednesday Morrison announced A$540 million for regional hydrogen hubs and carbon-capture and storage (CCS) projects. Some A$275 million will be committed to seven hydrogen hubs in regional areas over five years – that’s about A$7.8 million per hub each year.

It’s hard to see this buying much more than a plan on a piece of paper. Further, there’s little detail on how much will be spent on clean vs dirty hydrogen – that is, hydrogen generated from renewables vs fossil fuels. However the proposed location of some of these hubs in fossil-fuel rich areas, such as the Latrobe Valley and Hunter Valley, does not bode well.

A further A$263.7 million over ten years will fund CCS projects. Since 2003, the Australian government has spent more than A$1 billion on CCS projects, with very little to show for it.

Globally, CCS has been criticised as unproven and expensive, simply designed to extend the life of fossil fuel industries.




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trucks carry coal through mine
CCS critics say it is simply a move to prop up fossil fuel industries.
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The third tranche of funding, announced on Thursday, is A$566 million for research partnerships with other countries for new technology such as green steel, small modular nuclear reactors and soil carbon storage. There was little detail in the announcement, so for now it remains rather hypothetical.

In sum, the government will spend a relatively small amount on hydrogen production and CCS, spread wafer thin in various regional areas (and at least some of it subsidising fossil fuels), plus hypothetical funding for research.

Compare this to the A$35 billion cost of extreme weather disasters in Australia between 2010 and 2019, as detailed in this Climate Council report.

More recently, the New South Wales government estimated the potential cost of last month’s devastating floods at A$2 billion. A report by the NSW Treasury estimated by 2061, future economic costs of climate impacts in four key risk areas (bushfires, sea level rise, heatwaves and agricultural production) could reach up to A$17.2 billion a year – and this is just for NSW.




Read more:
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Debris washed up against bridge
The recent NSW floods caused $2 billion in damage, the state government says.
James Gourley/AAP

A tale of two leaders

Morrison told world leaders Australia would update its emissions-reduction target ahead of the Glasgow climate summit later this year. The current target – a 26-28% cut by 2030, based on 2005 levels – is broadly viewed as woefully inadequate.

Any increased ambition would be long overdue. However, more broadly, the contrast on climate policy between Morrison and Biden could not be clearer. Biden used the summit to tell world leaders:

Your leadership on this issue is a statement to the people of your nation and to the people of every nation, especially our young people, that we’re ready to meet this moment […] We really have no choice. We have to get this done.

Morrison, depressingly, showed little sign of hearing that message.The Conversation

Lesley Hughes, Professor, Department of Biological Sciences, Macquarie University and Will Steffen, Emeritus Professor, Fenner School of Environment & Society, Australian National University

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