Luminous ‘mother-of-pearl’ clouds explain why climate models miss so much Arctic and Antarctic warming

YanaBu, Shutterstock

Katrin Meissner, UNSW Sydney; Deepashree Dutta, University of Cambridge, and Martin Jucker, UNSW Sydney

Our planet has warmed by about 1.2°C since 1850. But this warming is not uniform. Warming at the poles, especially the Arctic, has been three to four times faster than the rest of the globe. It’s a phenomenon known as “polar amplification”.

Climate models simulate this effect, but when tested against the past 40 years of warming, these models fall short. The situation is even worse when it comes to modelling past climates with very high levels of greenhouse gases.

This is a problem because these are the same models used to project into the future and forecast how the climate will change. They are likely to underestimate what will happen later this century, including risks such as ice sheet melting or permafrost thawing.

In our new research published today in Nature Geoscience we used a high-resolution model of the atmosphere that includes the stratosphere. We found a special type of cloud appears over polar regions when greenhouse gas concentrations are very high. The role of this type of cloud has been overlooked so far. This is one of the reasons why our models are too cold at the poles.

Polar Stratospheric Clouds over Norway (Night Lights Films - Adrien Mauduit)

Back to the future

Looking into past climates can give us glimpses of possible futures for a range of extreme conditions. For us, this means we can use Earth’s history to find out how well our climate models perform. We can test our models by simulating episodes in the past when Earth was much warmer. The advantage of this is that we have temperature reconstructions for these episodes to evaluate the models, as opposed to the future, for which measurements are not available.

If we go back 50 million years or so, our planet was very hot. Carbon dioxide (CO₂) concentrations ranged between 900 and 1,900 parts per million (ppm), compared with 415 ppm today. Methane (CH₄) concentrations were likely also much higher.

Canada’s arctic archipelago was covered in lush rainforests inhabited by alligators, turtles, lizards and mammals.

For these plants and animals to survive, conditions must have been warm and ice-free year-round. Indeed, surface ocean temperatures exceeded 20°C near the north pole (at about 87°N) and 25°C in the Southern Ocean (at about 67°S).

This period called the early Eocene is a perfect test bed for our models, because it was globally very warm, and the poles were even warmer, meaning it was a climate with extreme polar amplification. In addition, the Eocene is recent enough for temperature reconstructions to be available.

But as it turns out, the models fail again. They are much too cold at high latitudes. What are our models missing?

Alligators, turtles, lizards and mammals lived in the Arctic about 50 million years ago, when it was much warmer than today. Bradley GT, Shutterstock

Polar stratospheric clouds

In 1992 American paleoclimatologist Lisa Sloan suggested polar stratospheric clouds might have caused extreme warming at high latitudes in the past.

These clouds are a rare and beautiful sight today. They are also called nacreous or mother-of-pearl clouds for their vivid and sometimes luminous colours.

They form at very high altitudes (in the stratosphere) and at very low temperatures (over the poles). In the present day climate, they appear mainly over Antarctica, but have also been observed during winter months over Scotland, Scandinavia and Alaska, at times when the stratosphere was particularly cold.

Just like greenhouse gases, they absorb infrared radiation emitted by the Earth’s surface and re-emit a portion of this energy back to the surface. This suggests polar stratospheric clouds could be one of the missing puzzle pieces.

They warm the surface. And their effect could be significant, especially in winter, when the sun does not rise. But they are difficult to simulate in a climate model, so most models ignore them. This omission could explain why climate models miss some of the polar warming, because they miss a process that warms the poles.

Three decades after Sloan’s paper, a few atmosphere models are finally complex enough to allow us to test her hypothesis. In our research we use one of them and find that under certain conditions, the additional warming due to these polar stratospheric clouds exceeds 7°C during the winter months. This significantly reduces the gap between climate models and temperature evidence from the early Eocene. Sloan was right.

Implications for future projections

Our research explains why climate models don’t work so well for past climates when greenhouse gas levels were much higher than they are today. But what about the future? Should we be concerned?

There is some good news. While polar stratospheric clouds do warm the poles, they won’t be as common in the future as they were in the distant past, even if both CO₂ and CH₄ reach very high levels.

This is due to another difference between the Eocene and today: the position of continents and mountains, which were different back then and which also influence the formation of polar stratospheric clouds. So even if we hit early Eocene levels of CH₄ and CO₂ in the future, we would expect less polar stratospheric cloud to be formed. This suggests the standard climate models are better at predicting the future than the past.

It’s therefore unlikely the Arctic and Antarctica will be covered by these beautiful clouds anytime soon. But our research shows evidence from past climates can reveal processes that only become important when greenhouse gas concentrations are high. Some of these processes are not included in our models because models are tested against present day observations and other processes simply seemed more important to include. Looking into the past is a way of broadening our horizon and learning for the future.

Katrin Meissner, Professor and Director of the Climate Change Research Centre, UNSW, UNSW Sydney; Deepashree Dutta, Postdoctoral Research Associate, University of Cambridge, and Martin Jucker, Lecturer in Atmospheric Dynamics, UNSW Sydney

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

Read More........→November 08, 2023

Polar bears may struggle to produce milk for their cubs as climate change melts sea ice

During their time onshore, polar bear mothers may risk their survival by continuing to nurse when food is not available. (Shutterstock) Louise Archer, University of Toronto

When sea ice melts, polar bears must move onto land for several months without access to food. This fasting period is challenging for all bears, but particularly for polar bear mothers who are nursing cubs.

Our research, published in Marine Ecology Progress Series, found that polar bear lactation is negatively affected by increased time spent on land when sea ice melts.

Impaired lactation has likely played a role in the recent decline of several polar bear populations. This research also indicates how polar bear families might be impacted in the future by continued sea-ice loss caused by climate warming.

Challenges of rearing cubs

While sea ice might appear as a vast and perhaps vacant ecosystem, the frozen Arctic waters provide an essential platform for polar bears to hunt energy-rich seals — the bread and butter of their diet.

Sea ice is a dynamic environment that can vary through time and in different regions of the Arctic. Polar bears in Canada’s western Hudson Bay area experience seasonal sea ice, which melts in the warmer summer months, forcing the polar bears to move onto land until cooler winter temperatures cause the sea ice to refreeze.

On shore, polar bears often remain in a fasting state, using their body stores of fat for fuel. (Shutterstock)

While on shore, hunting opportunities are rare and polar bears generally spend their time in a fasting state. Polar bears rely on their immense body fat stores to fuel them during these leaner months, with some individuals measuring almost 50 per cent body fat when they come onshore in early summer.

While on land, polar bears can lose around a kilogram of body mass per day, so making it to the end of the ice-free season requires them to carefully manage their energy. For most polar bears, this means reducing activity levels and conserving energy until the sea ice returns and seal hunting can resume.

Females with cubs must also factor in the additional burden of lactation. Polar bears produce high-energy milk, which — at up to 35 per cent fat — is like whipping cream. This high-fat milk allows cubs to grow quickly, increasing from just 600 grams at birth to well over 100 kilograms by the time they are around two-and-a-half years old and leave their mothers to become independent.

During the onshore fasting period, polar bear mothers face a difficult trade-off: Stop lactating and risk the health of her growing cubs or continue nursing and risk her own survival as her energy reserves are depleted.

Polar bear cubs remain with their mothers for up to two-and-a-half years. (Shutterstock)

Moderating lactation

Although lactation is important to both mothers and cubs, studies on polar bear lactation are relatively rare.

To better understand how females manage their lactation investment, our research team revisited a data set of polar bear milk samples collected in the late 1980s and early 1990s from polar bears on land during the ice-free period.

We estimated how long each polar bear mom had been fasting based on annual sea-ice breakup dates and found that the energy content of their milk declined the more days spent onshore. Some bears had stopped producing milk entirely. Both milk energy content and lactation probability were negatively related to the mother’s body condition, meaning females in poor body condition had to prioritize their own energetic needs over their cubs.

The bears who reduced their investment in lactation benefited by using up less of their body reserves, meaning they could fast for longer. Yet the cubs who received lower energy milk grew more slowly than offspring of females that maintained their lactation effort. In the long term, this may reduce cub survival and, ultimately, negatively affect population dynamics.

Climate change and population declines

After around three months on land, the probability of a female with cubs lactating was 53 per cent. This dropped to 35 per cent for a female with yearlings (older cubs from the previous year).

The data in our study were collected around three decades ago. Since then, climate warming has meant that the ice-free season in western Hudson Bay has been extending by around seven days per decade. Polar bears are now regularly forced to spend more than four months on land.

As the ice-free season has increased and polar bears must go for longer without food, their average body condition has declined. The ability of female polar bears to nurse their cubs has probably also become increasingly impaired.

This may have contributed to the 50 per cent decline in the population size of the western Hudson Bay population over the last four decades, and is likely to contribute to further declines if climate warming and sea-ice declines continue as projected without mitigation.

This research adds another piece to our understanding of polar bear resilience to climate change. Without action to halt climate warming and sea-ice loss, survival of cubs will be at risk across the Arctic.

Louise Archer, Postdoctoral Fellow, Biological Sciences, University of Toronto

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

Read More........→October 09, 2023

We are poised to pass 1.5℃ of global warming – world leaders offer 4 ways to manage this dangerous time

Marcus E Jones, Shutterstock Jonathan Symons, Macquarie University

For three decades, the goal of international climate negotiations has been to avoid “dangerous” warming above 1.5℃. With warming to date standing at around 1.2℃, we haven’t quite reached the zone we labelled dangerous and pledged to avoid.

But recent scientific assessments suggest we’re on the brink of passing that milestone. Within this decade, global annual temperatures will likely exceed 1.5°C above the pre-industrial average for at least one year. This threshold was already briefly passed for the month of July 2023 during the Northern summer. The question is, how do we manage this period of “overshoot” and bring temperatures back down? The goal will be to restore a more habitable climate, as fast as possible. Today an independent group of global leaders released a major report. The Climate Overshoot Commission offers guidance at this crucial time. So far the report’s call for an immediate moratorium on “solar radiation management” (deflecting the sun’s rays to reduce warming) has attracted the most attention. But the details of other recommendations deserve closer inspection.  How can we respond to climate overshoot? Historically, climate policies have focused on mitigation (reducing greenhouse gas emissions). More recently, adaptation has gained prominence. But the climate overshoot report identifies at least four different kinds of responses to warming above 1.5℃, 

• 1. cut emissions to mitigate warming
• 2. adapt to the changing climate 
• 4. remove carbon that is already in the atmosphere or ocean, 
• 5. explore intervening to limit warming by intentionally reflecting a fraction of sunlight into space. 

The commission’s task was to examine how all possible responses might best be combined. Their report was written by 12 global leaders – including former presidents of Niger, Kiribati and Mexico – who worked alongside a youth panel and a team of scientific advisers. The four-step plan to reining in warming Not surprisingly, the commission argues our central task is mitigation. Transitioning away from fossil fuels remains the first priority. But reaching net zero emissions is just the first step. The commission argues developed countries like Australia should go further and aim for net-negative emissions. Why net-negative? In the short term, drawing down carbon can create space for the least industrialised countries to fight poverty while transitioning to clean energy. In the longer term, the whole global economy must achieve net-negative emissions if the planet is to return to our current “safe” climatic zone. The second step is adaptation. Only a few decades ago former United States Vice President Al Gore branded adapting to climate change a “lazy cop-out”. Today we have no choice but to adapt to changing conditions. However, adaptation is expensive – whether it is developing new crop varieties or rebuilding coastal infrastructure. Since the poorest communities who are most vulnerable to climate harms have the least capacity to adapt, the commission recommends international assistance for locally controlled, context-specific strategies. As a third step, the commission agrees with scientific assessments that carbon dioxide “will need to be removed from the air on a significant scale and stored securely” if we are to avoid permanent overshoot beyond 1.5℃ warming. But how to achieve large-scale permanent, carbon removal? Some environmental activists support natural solutions such as planting trees but oppose industrial methods that seek to store carbon in inorganic form such as carbon capture and storage underground. The commission agrees the organic/inorganic distinction is important. However, it points out while forests bring many benefits, carbon stored in ecosystems is often re-released – for example, in forest fires. The commission worries many carbon removal approaches are phoney, impermanent or have adverse social and environmental impacts. However, instead of ruling out technologies on ideological grounds, it recommends research and regulation to ensure only socially beneficial and high-integrity forms of carbon removal are scaled up. The fourth step – “solar radiation management” – refers to techniques that aim to reduce climate harms caused by reflecting some of the Sun’s energy into space. No-one likes the idea of solar radiation management. But no-one likes getting vaccinated either – our gut reactions don’t provide a fool-proof guide to whether an intervention is a worth considering. Should we trust our guts on this one? While climate models suggest solar radiation management could reduce climate harms, we don’t yet properly understand associated risks. The commission approaches this topic with caution. On the one hand, it recommends an immediate “moratorium on the deployment of solar radiation modification and large-scale outdoor experiments” and rejects the idea that deployment is now inevitable. On the other hand, it recommends increased support for research, international dialogue on governance, and periodic global scientific reviews. Time to examine intervention in the climate system? The idea we can avoid dangerous warming completely seems increasingly quaint. Like baggy jeans, the boy band NSYNC and the iPod shuffle, it reminds us of a more innocent era. Yet, Australia’s climate debate often seems stuck in this era. The widespread hope we “still have time” means we are not yet discussing the merits of more interventionist responses to the climate crisis. However, there’s increasing reason to be sceptical incremental measures will be sufficient. We may soon be forced to move beyond the non-interventionist, conservation paradigm. Whether or not its recommendations are taken up, the Climate Overshoot Commission’s work shows how the international community has failed to avert dangerous climate change. Reckoning with the consequences of this failure will dominate public policy for decades to come. This new report takes us a step forward. Jonathan Symons, Senior Lecturer, Macquarie School of Social Sciences, Macquarie University This article is republished from The Conversation under a Creative Commons license. Read the original article.

Read More........→September 18, 2023

Earthquake footage shows Turkey’s buildings collapsing like pancakes. An expert explains why

 

Mustafa Karali / AP Mark Quigley, The University of Melbourne

A pair of huge earthquakes have struck in Turkey, leaving more than 3,000 people dead and unknown numbers injured or displaced.

The first quake, near Gaziantep close to the Syrian border, measured 7.8 in magnitude and was felt as far away as the UK. The second occurred nine hours later, on what appears to be an intersecting fault, registering a magnitude of 7.5.

Adding to the devastation, some 3,450 buildings have collapsed, according to the Turkish government. Many of the modern buildings have failed in a “pancake mode” of structural collapse.

Why did this happen? Was it simply the enormous magnitude and violence of the quake, or is the problem with the buildings?

Thousands of years of earthquakes

Earthquakes are common in Turkey, which sits in a very seismically active region where three tectonic plates constantly grind against one another beneath Earth’s surface. Historical records of earthquakes in the region go back at least 2,000 years, to a quake in 17 CE that levelled a dozen towns.

The East Anatolian Fault zone that hosted these earthquakes is at the boundary between the Arabian and Anatolian tectonic plates, which move past each other at approximately 6 to 10 mm per year. The elastic strain that accumulates in this plate boundary zone is released by intermittent earthquakes, which have occurred for millions of years. The recent earthquakes are thus not a surprise.

Despite this well-known seismic hazard, the region contains a lot of vulnerable infrastructure.

Over the past 2,000 years we have learnt a lot about how to construct buildings that can withstand the shaking from even severe earthquakes. However, in reality, there are many factors that influence building construction practices in this region and others worldwide.

Poor construction is a known problem

Many of the collapsed buildings appear to have been built from concrete without adequate seismic reinforcement. Seismic building codes in this region suggest these buildings should be able to sustain strong earthquakes (where the ground accelerates by 30% to 40% of the normal gravity) without incurring this type of complete failure.

The 7.8 and 7.5 earthquakes appear to have caused shaking in the range of 20 to 50% of gravity. A proportion of these buildings thus failed at shaking intensities lower than the “design code”.

There are well-known problems in Turkey and elsewhere with ensuring safe building construction and adherence to seismic building codes. Similar building collapses have been seen in past earthquakes in Turkey.   

A known problem: a collapsed apartment building after the 1999 earthquake in Izmit, Turkey. Hurriyet / AP

In 1999, a huge quake near Izmit saw some 17,000 people dead and as many as 20,000 buildings collapse.

After a quake in 2011 in which hundreds of people died, Turkey’s then prime minister, Recep Tayyip Erdogan, blamed shoddy construction for the high death toll, saying: “Municipalities, constructors and supervisors should now see that their negligence amounts to murder.”

Reconstruction

Even though Turkish authorities know many buildings are unsafe in earthquakes, it is still a difficult problem to solve. Many of the buildings are already built, and seismic retrofitting may be expensive or not considered a priority compared to other socio-economic challenges.

However, reconstruction after the quake may present an opportunity to rebuild more safely. In 2019, Turkey adopted new regulations to ensure buildings are better equipped to handle shaking.

While the new rules are welcome, it remains to be seen whether they will lead to genuine improvements in building quality.

In addition to substantive loss of life and infrastructure damage, both earthquakes are likely to have caused a myriad of environmental effects, such as ruptured ground surfaces, liquified soil, and landslides. These effects may render many areas unsafe to rebuild on – so reconstruction efforts should also include planning decisions about what can be built where, to lower future risks.

For now, aftershocks continue to shake the region, and search and rescue efforts continue. Once the dust settles, reconstruction will begin – but will we see stronger buildings, able to withstand the next quake, or more of the same?

Mark Quigley, Associate Professor of Earthquake Science, The University of Melbourne

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

Read More........→February 08, 2023

Indian outfit wins UN award for efforts to combat climate change amid COVID-19

SPORTS LIFESTYLE ENTERTAINMENT SPECIALS FEEDS UPCLOSE GALLERY CITIZEN REPORTER DOGRI CORNER Home World Indian outfit wins UN award for efforts to combat climate change amid COVID-19 OCT 28, 2020 UNITED NATIONS: An Indian organisation that leverages tourism and technology to help remote communities access solar energy has won a prestigious UN award for its efforts to combat climate change amid the Covid-19 pandemic. The Global Himalayan Expedition (GHE) is among the winners of the 2020 UN Global Climate Action Award. GHE is one of the world's first organisations using tourism and technology to bring solar energy to remote communities. The recipients of the 2020 United Nations Global Climate Action Awards, announced Tuesday, bring focus to the best examples of what people across the globe are doing "to combat climate change in a year that has cast darkness upon so many." According to a statement on the United Nations Framework Convention on Climate Change (UNFCCC) website, GHE is the one of the world's first outfit using tourism and technology to bring solar energy to remote communities as recognised by the World Travel and Tourism Council (WTTC) and the United Nations World Tourism Organisation (UNWTO). In the Hindu Kush Region, there are more than 16 million people without access to basic energy mainly due to their geographic remoteness. GHE conducts "Impact Expeditions" to remote Himalayan villages and uses a portion of the expedition fee to fund the capital cost of the hardware, transportation, installation and training of village-scale solar micro-grids. The micro-grid infrastructure set up by GHE is owned and operated by the community. To date, the GHE has solar electrified more than 131 villages in three regions of India, directly impacting the lives of more than 60,000 villagers. More than 1,300 travellers from 60 different countries have been a part of these expeditions. Enabling livelihood through homestay tourism has generated over USD 114,000 in income for the villages, which represents a 45 per cent increase in the annual household income, the statement said. UNFCCC said this year's award-winning projects demonstrate leadership on climate change by nations, businesses, investors, cities, regions and civil societies as a whole. They range from the Caribbean's only carbon-neutral hotel to the world's first platform fully dedicated to green bonds to the first all-women solar team in Lebanon. Congratulating the winners of the 2020 UN Global Climate Action Awards, UN Secretary-General António Guterres said the winners provide tangible proof that climate action is underway around the world. "It is exciting to see these climate solutions, which reinforce my call for decisive leadership on climate change by governments, businesses and cities, and for a green recovery from the Covid-19 pandemic. Let us keep pressing ahead to build a more sustainable and equitable future for all," he said. UN Climate Change Executive Secretary Patricia Espinosa said the last eight months have been a nightmare for many throughout the world. "Covid-19 has altered lives, economies and the nature of business on every continent -- from the largest cities to the smallest villages. It is the most urgent threat facing humanity today, but we cannot forget that climate change is the biggest threat facing humanity over the long term," said Espinosa. Espinosa said the convergence of these two crises has opened a window of opportunity to build forward, to build cities and communities that are safe, healthy, green and sustainable. "Nothing exemplifies this better than the efforts of our 2020 award-winning activities to address climate change." The award announcement is part of the wider effort to mobilise action and ambition as national governments work toward implementing the Paris Climate Change Agreement and the Sustainable Development Goals. The UN Global Climate Action Awards are spearheaded by the Momentum for Change initiative at UN Climate Change. The projects are recognised as innovative solutions that not only address climate change but also help drive progress on many other sustainable development goals. The 2020 winning activities were selected by an international advisory panel as part of the UN Climate Change's Momentum for Change initiative. "It is crucial we celebrate all actors who are leading the way," said Gabrielle Ginér, Chair of the Advisory Panel. "The recipients of the UN Global Climate Action Awards send a strong political signal to all nations, and through their leadership and creativity, we see essential change." Copyright © Jammu Links News, Source: Jammu Links News

Read More........→October 30, 2020