Category: Climate Change Impacts

Drought and heat together menace American West

Drought and heat together menace American West

By Tim Radford

Climate change really is a burning issue. Simultaneous drought and heat are increasingly likely for more of the American West.

LONDON, 13 October, 2020 − The American West is about to get hotter. It is also about to get drier. To make things worse, extremes of heat and of drought will happen more often at the same time.

And to compound the damage, such simultaneous assaults are likely to extend over larger areas and become more intense and more frequent, thanks to climate change driven by profligate use of fossil fuels and other human decisions.

This is not a prediction based on computer simulations of the future. It is already happening, and the story can be traced − according to the journal Science Advances − in the narrative of hot spells and dry weather over the entire contiguous United States for the last 122 years.

Not only have combined hot and dry episodes increased in frequency, they have also grown in size in geographic terms. Where once they happened in confined localities, they now extend over whole regions, such as the entire West Coast, and parts too of the Northeast and the Southeast.

Another Dust Bowl?

“Dry-hot events can cause large fires. Add wind and a source of ignition, and this results in ‘megafires’ like the 2020 fires across the west coast of the United States. Drought and record-breaking heatwaves, coupled with a storm that brought strong winds and 12,000 lightning events in a span of 72 hours, caused more than 500 wildfires,” said Mohammad Reza Alizadeh, of McGill University in Canada, who led the research.

Heat extremes can be damaging or even devastating. So can drought. When the two coincide, their compound impact can be tragic. The study also suggested that in some way such double jeopardy events could be self-propagating: they could spread downwind, seriously bad news for the American West and other areas at risk.

Long before any fears of the climate emergency, the US Midwest was scarred by drought, and in the 1930s Oklahoma and Kansas in particular became a “Dust Bowl” and inspired the classic novel The Grapes of Wrath by the American writer John Steinbeck.

“We observed that concurrent dry and hot events of similar intensity are becoming more frequent,” said Mojtaba Sadegh, an engineer at Boise State University in Idaho, and the senior author.

“Our results point to an urgent need to take action to enhance resilience to compound hot and dry events”

“The difference is that, in the 1930s, lack of precipitation led to the local atmosphere becoming hotter, whereas in recent decades increased temperatures are driving aridity. The triggering mechanism for compound dry-hot events is changing from lack of precipitation to excess heat.”

The warning of worse to come coincides with news that California’s fires have become so bad that they warrant a new classification: the “gigafire”, with so much smoke emitted from the combined fires of California and Oregon that fumes have been detected in New York, in northern Europe, and far into the Pacific.

Researchers have repeatedly warned of the double hazard of heat and drought and the combined impact on the US, as a consequence of climate change driven by greenhouse gas emissions from power station chimneys and automobile exhausts, as well as destruction of the natural wilderness.

“This research raises an alarm about increasing frequency and intensity of compound hot and dry events,” said Dr Sadegh. “Three such events between 2011-2013 in the US caused $60bn (£46bn) in damages. Our results point to an urgent need to take action to enhance resilience to compound hot and dry events.” − Climate News Network


Cover photo by Madu Shesharam on Unsplash.
Climate migration: what the research shows is very different from the alarmist headlines

Climate migration: what the research shows is very different from the alarmist headlines

By David Durand-Delacre, Carol Farbotko, Christiane Fröhlich, Ingrid Boas

Predictions of mass climate migration make for attention-grabbing headlines. For more than two decades, commentators have predicted “waves” and “rising tides” of people forced to move by climate change. Recently, a think-tank report warned the climate crisis could displace 1.2 billion people by 2050. Some commentators now even argue that, as the New York Times noted in a recent headline “The Great Climate Migration Has Begun”, and that the climate refugees we’ve been warned about are, in fact, already here.

These alarming statements are often well-intentioned. Their aim is to raise awareness of the plight of people vulnerable to climate change and motivate humanitarian action on their behalf. But such headlines aren’t always accurate – and rarely achieve their intended effect.

Our main concern is that alarming headlines about mass climate migrations risk leading to more walls, not fewer. Indeed, many on the right and far right are now setting aside their climate denialism and linking climate action to ideas of territory and ethnic purity. In this context of growing climate nationalism, even the most well-intentioned narratives risk feeding fear-based stories of invasion when they present climate migration as unprecedented and massive, urgent and destabilising.

The risk is only made worse when headlines point to racialised populations from the global south as on their way to the European Union, the US or Australia: places already in the grips of moral panics about migration.

Nigel Farage stood in front of 'breaking point' anti-immigration poster.
A moral panic. Facundo Arrizabalaga/EPA

We do not deny that climate change influences migration. We cannot ignore the damage done to communities around the world by rising sea levels, worsening droughts and catastrophic forest fires. These raise new and serious challenges we must contend with. Yet the above narratives are misleading and damaging, when the concept of human mobility requires a deeper and more nuanced approach. It’s important we take these harsh realities seriously but avoid being too alarmist or seeing everything as being determined by the climate.

In general, we are concerned by the inaccurate portrayal of migration. People have always moved under the combined influences of changing environments, economies and sociopolitical dynamics. Climate migration is neither new nor extraordinary. It is not even that different from other forms of migration – climate migrants still tend to move to places they know or have connections to through their social networks.

These are key aspects of the idea of “climate mobilities”, which we developed in a Nature Climate Change commentary with 31 co-authors including anthropologists, geographers and political scientists. We point to how mobility in the context of climate change is highly diverse – what the vast body of empirical research on the subject has shown is far different from the image of mass movements of people moving abroad.

Instead, we see highly varied and fragmented climate-related journeys. For instance, climate mobility can take the form of short-term, short-distance movements, rural-to-urban migration, or voluntary immobility. Contrary to the alarmist rhetoric of mass international migration, most movements do not involve crossing a border. For instance a million Somalians were internally displaced by a drought in 2016-17 – this dwarfs the numbers involved in any international climate migration.

Two women and their babies walk across a dry desert.
The 2016 drought also displaced hundreds of thousands of people in Ethiopia – but again, almost all stayed within the country. UNICEF EthiopiaCC BY-NC-SA

Fully understanding climate mobilities requires a broader evidence base than is typically used. Many problematic narratives rely mainly on quantitative modelling, reading peoples’ experiences only through that lens. More research collaboration with the social sciences and humanities would improve our understanding, as these disciplines can provide a sensitivity to context that models alone will never achieve.

Affected people are telling their own stories

As we turn to a more diverse set of perspectives, affected people must themselves be included. They are already telling their own stories, in their own words. It’s crucial that we listen, especially when they contradict our research findings and personal intuitions. Listening to Pacific Islanders, for example, tells us that easy tales of “sinking islands” aren’t the whole story. Activists throughout the region have distilled their message of themselves as powerful actors in the fight for climate justice (and against climate migration) in the catchcry: “We are not drowning, we are fighting”.

Protesters hold up signs
‘We are not drowning, we are fighting’ Carol Farbotko, Author provided

Halfway across the world, interviews with young farmers in Senegal living in precarious situations found that, while climate change does threaten their livelihoods, it is not their key concern, and they do not see migration as a problem. They want stronger local government, more local economic opportunities and the choice to migrate regardless of cause, if it can mean a better life for them and their families.

Finally, research and reporting on climate migration needs to better consider destination areas. Policymakers throughout the global north are notoriously incapable and reluctant to take the complex realities of migration into account, to the point of sometimes disregarding the research they fund. Instead they justify anti-immigration policies such as the UK’s “hostile environment” by presenting the interests and desires of “native” populations as competing with those of new arrivals.

These narratives of inevitable economic and cultural conflict need to be challenged. For this, we can draw on a large body of work that shows migrants aren’t all rich and successful, or poor and excluded, and that successful projects take these differences into account, listen to migrants themselves and promote open dialogue with established populations.

Building an open, diverse, and accepting society in times of crisis and change is a difficult task. We should take care not to make it harder by promoting fear-based stories of climate migration.


This article was originally posted on The Conversation.
River deltas become even riskier as climate warms

River deltas become even riskier as climate warms

By Tim Radford

River deltas are among the world’s richest habitats. They are also, increasingly, home to the most vulnerable people.

LONDON, 8 October, 2020 − Already, more than 30 million people worldwide are in danger of catastrophic floods − and now they face further danger from the river deltas which are their homes.

Ocean storm surges which are one threat could wash away their homes, their livelihoods, and even their lives. Another, rising tide levels, could turn their gardens to salt and sap the foundations of their lives. With many more, tropical cyclones could sweep in and literally rain their houses into the sea

What all these vulnerable people − in New Orleans, in Bangkok, in Shanghai, in the mouths of the Ganges-Brahmaputra, in any of more than 2,000 settlements − have in common is that they live on a river delta: that vital, ever-shifting zone where a great river spills its silt into the ocean.

And climate change driven by ever-rising ratios of greenhouse gases in the atmosphere − a consequence of ever-greater reliance on fossil fuels − can only make such hazards ever more dangerous. But the first challenge is: who, exactly, is most at risk? And where?

“To date, no-one has successfully quantified the global population in river deltas and assessed the cumulative impacts from climate change,” said Douglas Edmonds, of the University of Indiana in the US.

Costly endowment

“Since river deltas have long been recognised as hotspots of population growth, and with increasing impacts from climate change, we realised we needed to properly quantify what the cumulative risks are in river deltas.”

Dr Edmonds and his colleagues report in Nature Communications that they assembled a global database of 2,174 delta locations, to identity the populations settled on and around them in 2017, and the topography most at risk.

River deltas add up to perhaps 0.5% of the planet’s land surface, but they are home to 4.5% of the world’s population. Humans have settled on river deltas for at least 7,000 years: the rivers deliver nutrient-rich silts for new farmland, and the river estuaries have provided a focus for regional and international transport, to become some of the world’s greatest cities.

But such riches come at a cost: as the rivers have been contained and engineered, the land cover has changed and the land surface subsided. So as sea levels rise with climate change, deltaic areas could become 50% more vulnerable to coastal flood.

“No-one has successfully quantified the global population in river deltas and assessed the cumulative impacts from climate change”

Precisely because river deltas form at or even below sea level, they are highly prone to storm surges driven by tropical cyclones. And by 2100, these could become from 2% to 11% more intense.

The researchers found that in 2017, around 339m people had made their homes on 710,000 square kilometres of habitable land around river deltas: in this century alone, the population on deltas had grown by 34%.

Of these, 31m lived on floodplains vulnerable to the kind of storm surges that happen once a century. And of this 31m, 92% lived in developing or least-developed economies, often breathing polluted air, with poor housing and limited access to public services such as drainage. So, as usual, the poorest were also the most at risk from climate change.

In fact, as scientists have been warning for a decade or more, coastal flooding is a hazard inevitably on the increase, and an increasingly costly one, worldwide.

Even in the US, floods will become a serial nuisance in many cities and an estimated 13m Americans could eventually become climate refugees.

Very cautious estimates

Climate change is likely to deliver a hotter, wetter world with more soil erosion that could trigger catastrophic delta flooding. Hurricanes and typhoons driven by rising sea temperatures are likely to exact an ever-greater toll on human life and wealth.

The Indiana scientists warn that their estimates of those most at risk and the costs they face are likely to be highly conservative. They did not, for instance, consider the special case of what they call “compound interaction.”

This is sociological shorthand for what could happen when climate-related disaster overtakes those who are poorest, crowded into the least protected and unhealthiest zones of the cities. Altogether, 105m people have settled on the Ganges-Brahmaputra delta, half of them on low-lying farmland. The second most crowded is the Nile delta, with 45m people.

“To effectively prepare for more intense future coastal flooding,” Dr Edmonds said, “we need to reframe it as a problem that disproportionately impacts people on river deltas in developing and least developed economies.” − Climate News Network


This article was originally posted on The Climate News Network.
Cover image by Pinakpani on Wikimedia Commons.
How many people will migrate due to rising sea levels? Our best guesses aren’t good enough

How many people will migrate due to rising sea levels? Our best guesses aren’t good enough

By Sonja Ayeb-Karlsson, Celia McMichael, Ilan Kelman, Shouro Dasgupta

An article in 2011 shocked many by suggesting that up to 187 million people could be forced to leave their homes as a result of two metres of sea level rise by 2100. Almost a decade on, some of the latest estimates suggest that as many as 630 million people may live on land below projected annual flood levels by the end of the century.

The idea that rising seas will force millions to move, unleashing a refugee crisis like no other, has now become commonplace. It’s a narrative that the media are fond of, but that does not mean it is based on evidence.

The potential scale of sea level rise is becoming clearer, but this does not necessarily translate into population movements. Everything we have learned so far suggests that decisions to migrate are far more complex than a simple flight response.

In our new review article, we looked at 33 different studies that have estimated how sea level rise will affect migration patterns. Reliable estimates are important to help support vulnerable populations, but there is deep uncertainty around the amount of people who will be exposed to rising seas, and how they will respond.

Trapped populations

We looked carefully at the methods and data sets of these studies to try and tease out uncertainties. One issue plaguing their estimates is assumptions about the number of people who will be living in vulnerable low-lying areas in the future.

Most of the studies we reviewed did note that the connections between migration and sea level rise are incredibly complex. Every person directly affected isn’t guaranteed to move away as a result. People may be just as likely to try and protect their homes against the water, by building sea walls or elevating their houses.

It’s impossible to predict how each person will respond, and there are countless reasons why someone might choose to stay in the place they call home rather than move or seek shelter elsewhere. Those who may be forced to migrate and resettle due to climate change receive far more attention than those left behind. These so-called “trapped” populations can be just as vulnerable as those on the move, if not more so.

A wooden sailboat rests on a green bank next to a palm tree which has been overwhelmed by the rising water.
Despite flooding and erosion, many of the Bangladeshis we interviewed said they cannot or do not want to leave their home villages. Sonja Ayeb-Karlsson, Author provided

Research suggests that the decision to stay or leave will have as much to do with emotional and social pressures as financial or practical reasons. People may feel afraid or find it unbearable to leave, while others lack the necessary support. Many may feel obliged to stay due to binding social ties and reponsibilities.

How the health and wellbeing of those staying behind will be affected by rising seas is poorly investigated. More research is needed to understand the realities of staying put, for those who choose to stay and those who are unable to leave.

Where do we go from here?

Research on sea level rise and migration has often tried to obtain global estimates of those likely to be affected. These are useful for drawing attention to the potential scale of future impacts, but they lack local insights that could help make the picture clearer for different areas.

Rising sea levels are just one of the many ways climate change is remaking our world. Understanding how sea level rise interacts with other environmental changes, such as increased temperatures and changing rainfall patterns will be important, but this stretches the ability to predict exact migration numbers.

A young girl stands on a concrete bank as a red, wooden boat returns from fishing.
A young girl watches as a group of men return home from a fishing trip. Sonja Ayeb-Karlsson, Author provided

Despite all the unknowns, we do know that coastal changes wrought by climate change will be significant, and they require action now. That means devising measures to prevent or reduce inundation, figuring out how to live with the water, and planning for successful ways to migrate and resettle. Evaluating options, developing scenarios, and making decisions around this must happen now, rather than waiting for the issue to become more urgent.

It is just as important to avoid repeating myths around climate change triggering vast flows of people from the so-called “Global South” seeking refuge in the so-called “Global North”. We do know that people will not inevitably flee across borders in a warming world. Where migration does happen, movements within countries are often neglected on the likely flawed assumption that most migrants are crossing borders.

The narratives create unnecessary concern while shifting focus away from what really matters – helping vulnerable people. Not only do these myths reproduce xenophobic and outdated colonial power relations based on unfounded arguments, but they also create unnecessary fear and hostile environments for migrant populations around the world.


This article was originally posted on The Conversation.
Cover photo by Artiom Vallat on Unsplash.
Svalbard glaciers lost their protective buffer in the mid-1980s and have been melting ever since

Svalbard glaciers lost their protective buffer in the mid-1980s and have been melting ever since

By Brice Noël andMichiel van den Broeke

The archipelago of Svalbard, a land of ice and polar bears, is found midway between mainland Norway and the North Pole. Its capital Longyearbyen on the main island of Spitsbergen is the world’s most northerly city, some 800 miles inside the Arctic Circle.

Svalbard is also home to some of the Earth’s northernmost glaciers, which bury most of the archipelago’s surface under no less than 200 metres of thick ice. Taken together, Svalbard glaciers represent 6% of the worldwide glacier area outside the large ice sheets of Greenland and Antarctica – if they totally melted, they would raise the sea level by 1.7cm.

Satellite map of mountainous islands largely covered in ice.
Svalbard is roughly the size of Ireland or Sri Lanka, but largely covered in ice. Google Maps

Because they are so far north, these glaciers are found at relatively low elevations, mostly below 450 metres above sea level compared to 800 metres or more elsewhere in the Arctic. Moreover, they are shaped like domes with steep sides and extensive flat interiors. These peculiar features make Svalbard glaciers highly vulnerable to climate warming, as we discovered in our research now published in Nature Communications.

Firn, the ultimate meltwater buffer

Svalbard has a relatively dry climate, and each year the amount of meltwater exceeds the amount of snowfall that nourishes the glaciers. This was the case even before the climate started to warm in earnest. So how do these glaciers survive such unfavourable conditions?

Polar bear warning sign, text beneath says
Polar bear warning: ‘applies to all of Svalbard’ Kaca Skokanova / shutterstock

Their secret is hidden below the surface, in a mantle of cold, compressed snow – called “firn” – that covers the glaciers’ interior. The porous firn layer can be up to 40 metres deep, and acts as a sponge that can store massive amounts of meltwater in its air pockets.

About half of all meltwater produced on Svalbard in the Arctic summer is stored and refrozen in the firn layer, preserving glacial mass by preventing the water from flowing into the ocean. When the glaciers stop melting in winter, the buffer capacity of the firn layer is replenished by the accumulation of fresh, fluffy snow, prepping it to store next summer’s wave of meltwater.

Global warming reaches the far north

Being located at the margin of the rapidly declining sea ice cover in the Arctic Ocean, Svalbard is among the fastest warming regions on Earth. And this warming is testing the limits of the firn layer’s capacity to store meltwater.

Rising air temperature in the mid-1980s considerably increased the amount of water that was melting across the glaciers and rapidly filled the air pockets in the firn, progressively weakening its buffer capacity. To make matters worse, the firn layer retreated fast inland to reach the elevation of 450 metres – a critical point that left more than half of the archipelago’s glacier area unprotected.

The disappearance of firn leaves glaciers without their protective buffer, exposing the underlying dark bare ice at the surface. As dark ice absorbs more sunlight than the brighter firn, melt increased even further.

Large glacier flows into the sea. White in background and grey in the foreground.
A Svalbard glacier transitions from firn-covered ice in the background to bare ice in the foreground. Willem Jan van de Berg, Utrecht University, Author provided

The rapid retreat of firn in the mid-1980s triggered a period of sustained mass loss, which has been confirmed by satellite observations. The loss of the meltwater buffer makes Svalbard glaciers highly vulnerable to a further temperature rise. In the warm summer of 2013, water reached the ocean from three-quarters of the glacier area, and mass loss more than doubled compared to previous years. In July 2020, Svalbard experienced record high temperatures once again. Some climatologists predict increases of up to 10℃ by the end of this century – if that happens, the archipelago’s glaciers could completely disappear in the next 400 years.

A climate crisis leads to an identity crisis

Further warming will completely reshape Svalbard’s climate, its landscape and its fragile ecosystems. Rain will progressively replace snowfall. Glaciers will trade their white firn mantle for dark ice. Open waters will invade fjords as sea ice and floating glacier tongues retreat. On land, receding glaciers will leave behind moraines and lakes as a reminiscence of a bygone glacial era. The landscape will start to resemble that of Iceland today, with bare rocks surrounded by grass, mosses and shrubs.

Large mountains with glaciers, grassy hills in foreground.
Iceland… or Svalbard in a few centuries? daniel.t.johansson / shutterstock

The retreating ice will allow increased human activity, including mining, farming and tourism, and further increase the pressure on the wildlife, including the iconic polar bears. Already, polar bears are more frequently sighted on land as the rapid decline in sea ice has forced them to adapt and look for new hunting grounds, endangering both humans and polar bears themselves.

Being located among the fastest warming regions on Earth, Svalbard glaciers are the canary in the coal mine. They can be seen as thermometers monitoring the devastating impacts of the climate crisis. It may not be too late to save part of Svalbard’s glacial landscape and the fragile ecosystems it supports, but time is quickly running out.


This article was originally posted on The Conversation.
Cover photo by AWeith / Wikimedia Commons.
Stanford researchers identify ‘landfalling droughts’ that originate over ocean

Stanford researchers identify ‘landfalling droughts’ that originate over ocean

By Danielle Torrent Tucker

Meteorologists track hurricanes over the oceans, forecasting where and when landfall might occur so residents can prepare for a disaster before it strikes. What if they could do the same thing for droughts?

Stanford scientists have now shown that may be possible in some instances – the researchers have identified a new kind of “landfalling drought” that can potentially be predicted before it impacts people and ecosystems on land. They found that these droughts, which form over the ocean and then migrate landward, can cause larger and drier conditions than droughts that occur solely over the land. Of all the droughts affecting land areas worldwide from 1981 to 2018, roughly one in six were landfalling droughts, according to the study published Sept. 21 in Water Resources Research.

“We normally don’t think about droughts over the ocean – it may even sound counterintuitive. But just as overland, there can be times where large regions in the ocean experience less rainfall than normal,” said lead author Julio Herrera-Estrada, a research collaborator with Water in the West who conducted research for the study while he was a postdoctoral researcher at Stanford’s School of Earth, Energy & Environmental Sciences (Stanford Earth). “Finding that some droughts start offshore will hopefully motivate conversations about the benefits of monitoring and forecasting droughts beyond the continents.”

Droughts can harm or destroy crops, as well as impact water supplies, electricity generation, trade and ecosystem health. Historically, droughts have displaced millions of people and cost billions of dollars. Yet the climate processes that lead to drought are not fully understood, making accurate predictions difficult.

In order to pinpoint the large-scale landfalling droughts that originated over the ocean, the researchers used an object tracking algorithm to identify and follow clusters of moisture deficits all over the world, going back decades in time. They found that the landfalling droughts grew about three times as fast as land-only droughts, and usually took several months to reach a continent.

“Not all of the droughts that cause damage to humans and ecosystems are going to be these landfalling droughts,” said study senior author and climate scientist Noah Diffenbaugh, the Kara J. Foundation Professor at Stanford Earth. “But there is something about the droughts that start over the ocean that makes them more likely to turn into large, intense events.”

The researchers analyzed the physical processes of landfalling droughts in western North America, where a high frequency of them occur. They found that droughts that make landfall in the region have been associated with certain atmospheric pressure patterns that reduce moisture, similar to the “Ridiculously Resilient Ridge” pattern that was one of the primary causes of the 2012-2017 California Drought.

The authors state that further analyses may reveal similar or new explanations for the landfalling droughts that they identified in other areas of the world, including Chile, Argentina, New Zealand and Eastern Australia.

“Our paper shows that landfalling droughts are a global phenomenon that affects every continent,” Herrera-Estrada said. “There will definitely be a need for other studies to focus more on the physical processes relevant for each individual region.”

Because of the large humanitarian and economic impacts of severe droughts, the potential for forecasting landfalling droughts may warrant further investigation, according to the researchers.

“This is an important finding because these landfalling droughts are statistically likely to be larger and more severe relative to non-landfalling droughts,” said Diffenbaugh, who is also the Kimmelman Family Senior Fellow at the Stanford Woods Institute for the Environment. “Because they usually take a number of months to migrate onto land, there is a potential that tracking moisture deficits over the ocean could provide advance warning to help protect against at least some of the most severe droughts.”


Read the original press release here.
Cover photo by Anton Ivanchenko on Unsplash
Wilder shores of science yield new ideas on climate

Wilder shores of science yield new ideas on climate

By Tim Radford

New ideas on climate mean earthquake scientists know more about global heating and astronomers worry over rising warmth.

Science has extended research into the global heating crisis, thanks to new ideas on climate. And, conversely, climate change has extended science in unexpected ways.

Seismologists believe they may have a new way to take the temperature of the world’s oceans. And astronomers focused on distant galaxies have unwittingly amassed a 30-year record of climate change in the Earth’s own atmosphere.

Both discoveries, in the same week, start with the simple physics of sight and sound. US and Chinese researchers report in the journal Science that records from submarine earthquakes could now deliver an unexpected way of measuring the warmth of the water.

Submarine earthquakes create a pattern of sound that can be transmitted immense distances through the ocean without much weakening. And, since the speed of sound in water increases as the temperature of the water rises, the length of time the sound takes to reach detector equipment is itself an indicator of ocean temperature.

Seismologists know – from waves travelling through the Earth’s crust and its deep interior – when and where the earthquakes happen. Seismic waves sprint through rock at rates measured in kilometres per second. Sound waves propagate through oceans at rates measured in kilometres per hour.

“It is of prime importance that astronomy uses its unique perspective to claim this simple fact: there is no planet B”

Just as the differences between the speed of lightning and the speed of thunder can establish the distance of an electrical storm, so if researchers know the time and distance of the sea floor event, they have a way of taking the temperature of the water. The constant rumbling of a living planet could offer a new set of easily assembled readings.

“The key is that we use repeating earthquakes – earthquakes that happen again and again in the same place,” said Wenbo Wu, of the California Institute of Technology, who led the Science study.

“We’re looking at earthquakes that occur off Sumatra in Indonesia, and we measure when they arrive in the central Indian Ocean. It takes about half an hour for them to travel that distance, with water temperature causing about one tenth of a second difference. It’s a very small fractional change, but we can measure it.”

The finding matters because – although humans have been recording local ground and air temperatures for at least 300 years, and worldwide for more than a century – it is much harder to be sure about ocean temperatures: the seas cover 70% of the planet, to an average depth of more than 3 kms, and the temperatures vary with both depth and latitude.

Sound goes deep

Oceanographic research is costly, technically challenging, and uneven. Researchers know that the oceans are responding to climate change driven by global heating as a consequence of greenhouse gas emissions: they do not, however, yet have an assured measure of how much heat the oceans have absorbed, and will go on absorbing.

“The ocean plays a role in the rate that the climate is changing,” said Jörn Callies of Caltech, a co-author. “The ocean is the main reservoir of energy in the climate system, and the deep ocean in particular is important to monitor. One advantage of our method is that the sound waves sample depths below 2,000 metres where there are very few conventional measurements.”

Paradoxically, astronomers need to know a great deal about the first few thousand metres of planet Earth as they peer into the furthest reaches of the universe: what they see and how well they see it is affected by atmospheric temperature, turbulence and moisture.

As ground-based telescopes become bigger and more sensitive – the Extremely Large Telescope now under construction at Paranal in northern Chile will collect light with a mirror 39 metres across – so do the challenges of eliminating the atmospheric turbulence that puts the twinkle in the stars of the night sky: cold air and warm air refract light differently, to create a blur. The bigger the telescope, the greater will be the problem of blur.

For three decades, scientists in the highest and driest part of Chile have been recording subtle and not so subtle atmospheric change. And according to the journal Nature Astronomy, climate change is already beginning to affect astronomical research, and will go on creating problems.

Terrestrial disturbances

“The data showed a 1.5°C increase in near-ground temperature over the last four decades at the Paranal Observatory,” said Susanne Crewell of the University of Cologne. “This is slightly higher than the worldwide average of 1°C since the pre-industrial age.”

Average wind speeds – wind also affects the precision of observations – have increased by 3 or 4 metres per second in the same period. Humidity, too, is expected to change as the world moves to what could be a 4°C average rise in temperature by the century’s end.

The message is that conditions on Earth can disturb the observations and mask the understanding of events billions of light years away and billions of years ago. Astronomers, too, need to sound the alarm about climate change, she and her colleagues write.

“To do so, a massive cultural shift is needed,” they conclude, “and it is of prime importance that astronomy uses its unique perspective to claim this simple fact: there is no planet B.” – Climate News Network


This article was originally posted on The Climate News Network.
Image: By Y. Beletsky (LCO)/ESO, via Wikimedia Commons
Arctic warming: are record temperatures and fires arriving earlier than scientists predicted?

Arctic warming: are record temperatures and fires arriving earlier than scientists predicted?

By Christopher J White

It was a grim record. On June 20 2020, the mercury reached 38°C in Verkhoyansk, Siberia – the hottest it’s ever been in the Arctic in recorded history. With the heatwaves came fire, and by the start of August around 600 individual fires were being detected every day. By early September, parts of the Siberian Arctic had been burning since the second week of June.

CO₂ emissions from these fires increased by more than a third compared to 2019, according to scientists at the Copernicus Atmosphere Monitoring Service. The wildfires produced an estimated 244 megatons of CO₂ between January and August, releasing thousands of years’ worth of stored carbon.

The summer of 2019 was already a record breaker for temperatures and fires across the Arctic. Seeing these events unfold again in 2020 – on an even larger scale – has the scientific community worried. What does it all mean for the Arctic, climate change and the rest of the world?

A satellite image shows smoke and clouds swirling over Russia.
A blanket of smoke stretches more than 4.5 million square kilometres across central and northern Asia. July 24 2019. EPA-EFE/NASA EARTH OBSERVATORY

Sooner than predicted?

Even with climate change, the severe summer heatwave of 2020 was expected to occur, on average, less than once every 130 years. Wildfire observations in the Arctic are fairly limited prior to the mid-1990s, but there is no evidence of similarly extreme fires in the years before routine monitoring started.

Higher temperatures globally are likely to be driving the increase in wildfire frequency and duration. But modelling wildfires is difficult. Climate models don’t predict wildfires, and they cannot indicate when future extreme events will occur year-on-year. Instead, climate modellers focus on whether they are able to predict the right conditions for events like wildfires, such as high temperatures and strong winds.

And these climate model projections show that the kind of extreme summer temperatures we’ve seen in the Arctic in 2020 weren’t likely to occur until the mid-21st century, exceeding predictions by decades.

So even though an increasing trend of high temperatures and conditions suitable for wildfires are predicted in climate models, it’s alarming that these fires are so severe, have occurred in the same region two years in a row, and were caused by conditions which weren’t expected until further in the future.

Fire burns the understory of a boreal woodland.
The Arctic is warming at a faster rate than the global average. Yelantsevv/Shutterstock

Climate feedback loops

So what is causing this rapid change? Over recent decades, temperatures in the most northerly reaches of Earth have been increasing at a faster rate than the rest of the world, with the polar region heating at more than twice the rate of the global average.

The fires caused by these hot, dry conditions are occurring in remote and sparsely populated forests, tundra and peat bogs, where there is ample fuel.

But these extreme events are also providing worrying evidence of climate “feedback loops”, which were predicted to happen as the climate warms. This is where increasing concentrations of greenhouse gases in the atmosphere contribute to further warming by promoting events – like wildfires – which release even more greenhouse gas, creating a self-perpetuating process that accelerates climate change.

Record CO₂ emissions released from burning Arctic forests during the summer of 2020 will make future conditions even warmer. But ash and other particulates from the wildfires will eventually settle on the ice and snow, making them darker and accelerating their melting by reducing how easily their surface reflects sunlight.

Climate change is not the direct cause of this summer’s fires, but it is helping to create the right conditions for them. The extreme temperatures and wildfires seen throughout the Arctic in 2020 would have been almost impossible without the influence of human-induced climate change – and they are feeding themselves.

Ice surface with black stain from soot.
Soot-stained ice absorbs more of the sun’s heat and melts more quickly. Trifonov Aleksey/Shutterstock

What about the rest of the world?

When we think of the Arctic, we don’t tend to picture wildfires and heatwaves – we think of snow and ice and long, brutal winters. Yet the region is changing before our eyes. It’s too early to say whether the last two summers represent a permanent step-change, or new “fire regime”, for the Arctic. Only observations over a much longer timescale could confirm this.

But these record-breaking events in the Arctic are being fuelled by human influences that are changing our world’s climate sooner than many expected. With climate models predicting a future where already hot and fire-prone areas are likely to become more so, 2020’s record temperatures paint a worrying trend towards more of the same.

The Arctic is at the frontline of climate change. What we are witnessing here first are some of the most rapid and intense effects of climate change. While the impact is devastating – record CO₂ emissions, damaged forests and soils, melting permafrost – these events may prove to be a portent of things to come for the rest of the world.


This article was originally published on The Conversation.
Cover photo by Roxanne Desgagnés on Wikimedia Commons.
Mass migration set to increase as world warms

Mass migration set to increase as world warms

By Paul Brown

Climate change is now driving mass migration, which will only worsen unless governments take global heating seriously.

There is strong evidence that deteriorating environments caused by climate change are driving millions of people to resort to mass migration in their search for a better life, both within countries and across borders.

As temperatures rise these migrations will only increase, particularly in Latin America and India, which is predicted to overtake China as the country with the largest population by 2025.

An analysis of environment and migration, published in Nature Climate Change, of 30 studies of individual countries across the world shows that there is no one single factor that drives migration.

But most research has found that environmental hazards have a major influence. Rising temperature levels, changes in rainfall and single sudden events like hurricanes are all triggers.

Policies for improvement

The analysis, by the International Institute for Applied Systems Analysis (IIASA) in Austria and research partners across Europe, was undertaken to try to inform policy makers about how to avert mass human migration.

It points out that two of the most high-profile mass migration episodes in recent times – the Syrian refugee crisis in 2015 and the “migrant caravan” from Central America to the United States in 2018 – have been partly attributed to severe droughts in the countries concerned.

While some studies conclude that environmental factors were not the main driver of migration, most thought it was one of the primary causes. The analysis says governments should expect significantly higher migration flows in the future.

Perhaps surprisingly, given the publicity surrounding the issue, migrations were not centred on poor people trying to enter rich nations in Europe or North America. Instead, most movements were from the countryside to urban areas in the same country, particularly in agriculturally dependent countries, or from one middle-income country to another.

“The best way to protect those affected is to stabilise the global climate by rapidly reducing greenhouse gas emissions from burning fossil fuels”

People with particularly low incomes normally stayed where they were,  despite environmental pressures, because they had no way of financing a move, while richer people had the means to adapt to new circumstances and so they also stayed put.

“Environmental factors can drive migration, but the size of the effects depends on the particular economic and socio-political conditions in the countries,” explains the lead author Roman Hoffmann, from Germany’s Potsdam Institute for Climate Impact Research (PIK).

“In both low and high income countries, environmental impacts on migration are weaker – presumably because either people are too poor to leave and therefore essentially become trapped or, in wealthy countries, they have enough financial means to absorb the consequences. It is mainly in middle-income regions and those with a dependency on agriculture that we see strong effects.”

IIASA predicts future higher levels of environmental migration for countries in Central America, the Caribbean, Brazil and Argentina. In Africa it is the Sahel region south of the Sahara that is already drying out, and East Africa that has the highest potential for people migrating because of climate change.

Eyes on India

Perhaps the most disturbing prediction is that India, with 1.3 billion people and soon to be the most populous country in the world, is likely to see large migrations. The heat and floods in the country are already killing hundreds of people a year, and many millions who are still dependent on subsistence agriculture are struggling with changing climate conditions.

“Our research suggests that populations in Latin America and the Caribbean, several countries in sub-Saharan Africa – especially in the Sahel region and East Africa – as well as western, southern and south-east Asia, are particularly at risk,” says co-author Anna Dimitrova from the Vienna Institute of Demography of the Austrian Academy of Sciences.

While the report is aimed at preparing governments for migrations that will inevitably happen in the future, with difficult consequences for both the migrants and the host country, the research suggests the best way of averting the coming crisis is to tackle climate change and reduce further rises in temperatures.

“The best way to protect those affected is to stabilise the global climate by rapidly reducing greenhouse gas emissions from burning fossil fuels as well as simultaneously to enhance adaptive capacity, such as through improving human capital,” says Jesus Crespo Cuaresma, a researcher with the IIASA World Population Program and professor of economics at the Vienna University of Economics and Business. − Climate News Network


This article was originally posted on the Climate News Network.
Cover photo from Pikist.
Rivers flood, seas rise – and land faces erosion

Rivers flood, seas rise – and land faces erosion

By Tim Radford

Polar melting cannot be separated from farmland soil erosion and estuarine flooding. All are part of climate change.

Climate heating often ensures that calamities don’t come singly: so don’t forget what erosion can do.

In a warmer world the glaciers will melt ever faster to raise global sea levels ever higher. In a wetter world, more and more topsoil will be swept off the farmlands and downriver into the ever-rising seas.

And the pay-off of silt-laden rivers and rising sea levels could be catastrophic floods, as swollen rivers suddenly change course. Since many of the world’s greatest cities are built on river estuaries, lives and economies will be at risk.

Three new studies in two journals deliver a sharp reminder that the consequences of global heating are not straightforward: the world responds to change in unpredictable ways.

First: the melting of the ice sheets and the mountain glaciers. Researchers warn in the journal Nature Climate Change that if the loss of ice from Antarctica, Greenland and the frozen rivers continues, then climate forecasters and government agencies will have to think again: sea levels could rise to at least 17cms higher than the worst predictions so far.

“Avulsions are the earthquakes of rivers. They are sudden and sometimes catastrophic. We are trying to understand where and when the next avulsions will occur”

That means an additional 16 million people at hazard from estuarine floods and storm surges.

In the last 30 years, the flow from the Antarctic ice cap has raised sea levels by 7.2mm, and from Greenland by 10.6mm. Every year, the world’s oceans are 4mm higher than they were the year before.

“Although we anticipated the ice sheets would lose increasing amounts of ice in response to the warming of the oceans and the atmosphere, the rate at which they are melting has accelerated faster than we could have imagined,” said Tom Slater of the University of Leeds, in the UK, who led the research.

“The melting is overtaking the climate models we use to guide us, and we are in danger of being unprepared for the risks posed by sea level rise.”

Dr Slater and his colleagues are the third team to warn in the last month that observations of climate already match the worst-case scenarios dreamed up by forecasters preparing for a range of possible climate outcomes.

Erosion risk rises

The latest reading of glacial melt rates suggests that the risk of storm surges for many of the world’s greatest cities will double by the close of the century. But coastal cities – and the farmers who already work 38% of the terrestrial surface to feed almost 8bn people – have another more immediate problem.

In a warmer world, more water evaporates. In a warmer atmosphere, the capacity of the air to hold moisture also increases, so along with more intense droughts, heavier rainfall is on the way for much of the world. And the heavier the rain, or the more prolonged the drought, the higher the risk of soil erosion.

In 2015 the world’s farmers and foresters watched 43 billion tonnes of topsoil wash away from hillsides or blow away from tilled land and into the sea. By 2070, this burden of silt swept away by water or blown by wind will have risen by between 30% and 66%: probably more than 28 bn tons of additional loss.

This could only impoverish the farmland, according to a study by Swiss scientists in the Proceedings of the National Academy of Sciences. It could also impoverish people, communities and countries. The worst hit could be in the less developed nations of the tropics and subtropics.

But the flow of ever-higher silt levels into ever-rising seas also raises a new hazard: hydrologists call it river avulsion. It’s a simple and natural process. As conditions change, so rivers will naturally change their flow to spill over new floodplains and extend coastal lands.

Survival in question

But river avulsions can also be helped along by rising sea levels. Since 10% of humanity is crowded into rich, fertile delta lands, and since some of the deadliest floods in human history – two in China in 1887 and 1931 claimed six million lives – have been caused by river avulsions, the question becomes a matter of life and death.

US scientists report, also in the Proceedings of the National Academy of Sciences, that rising sea levels alone could make abrupt river avulsion more probable, especially as delta lands could be subsiding, because of groundwater and other extraction.

The dangers of avulsion are affected by the rate of sediment deposit in the river channels, and this is likely to rise with sea levels. This in turn raises the level of the river and eventually a breach of a levee or other flood defence will force the river to find a swifter, steeper path to the sea.

Cities such as New Orleans and the coastal communities of the Mississippi delta are already vulnerable. “Avulsions are the earthquakes of rivers,” said Michael Lamb, of California Institute of Technology, one of the authors.

“They are sudden and sometimes catastrophic natural events that occur with statistical regularity, shifting the direction of major rivers. We are trying to understand where and when the next avulsions will occur.” – Climate News Network


This article was originally posted on The Climate News Network.