Suffering in the heat: the rise in marine heatwaves is harming ocean species



File 20190303 110119 1w5b8am.jpg?ixlib=rb 1.1
Recent marine heatwaves have devastated crucial coastal habitats, including kelp forests, seagrass meadows and coral reefs.
Dan Smale, Author provided

Dan Smale, Marine Biological Association and Thomas Wernberg, University of Western Australia

In the midst of a raging heatwave, most people think of the ocean as a nice place to cool down. But heatwaves can strike in the ocean as well as on land. And when they do, marine organisms of all kinds – plankton, seaweed, corals, snails, fish, birds and mammals – also feel the wrath of soaring temperatures.

Our new research, published today in Nature Climate Change, makes abundantly clear the destructive force of marine heatwaves. We compared the effects on ecosystems of eight marine heatwaves from around the world, including four El Niño events (1982-83, 1986-87, 1991-92, 1997-98), three extreme heat events in the Mediterranean Sea (1999, 2003, 2006) and one in Western Australia in 2011. We found that these events can significantly damage the health of corals, kelps and seagrasses.

This is concerning, because these species form the foundation of many ecosystems, from the tropics to polar waters. Thousands of other species – not to mention a wealth of human activities – depend on them.

We identified southeastern Australia, southeast Asia, northwestern Africa, Europe and eastern Canada as the places where marine species are most at risk of extreme heat in the future.




Read more:
Marine heatwaves are getting hotter, lasting longer and doing more damage


Marine heatwaves are defined as periods of five days or more during which ocean temperatures are unusually high, compared with the long-term average for any given place. Just like their counterparts on land, marine heatwaves have been getting more frequent, hotter and longer in recent decades. Globally, there were 54% more heatwave days per year between 1987 and 2016 than in 1925–54.

Although the heatwaves we studied varied widely in their maximum intensity and duration, we found that all of them had negative impacts on a broad range of different types of marine species.

Marine heatwaves in tropical regions have caused widespread coral bleaching.

Humans also depend on these species, either directly or indirectly, because they underpin a wealth of ecological goods and services. For example, many marine ecosystems support commercial and recreational fisheries, contribute to carbon storage and nutrient cycling, offer venues for tourism and recreation, or are culturally or scientifically significant.




Read more:
Australia’s ‘other’ reef is worth more than $10 billion a year – but have you heard of it?


.

Marine heatwaves have had negative impacts on virtually all these “ecosystem services”. For example, seagrass meadows in the Mediterranean Sea, which store significant amounts of carbon, are harmed by extreme temperatures recorded during marine heatwaves. In the summers of both 2003 and 2006, marine heatwaves led to widespread seagrass deaths.




Read more:
Seagrass, protector of shipwrecks and buried treasure


The marine heatwaves off the west coast of Australia in 2011 and northeast America in 2012 led to dramatic changes in the regionally important abalone and lobster fisheries, respectively. Several marine heatwaves associated with El Niño events caused widespread coral bleaching with consequences for biodiversity, fisheries, coastal erosion and tourism.

Mass die-offs of finfish and shellfish have been recorded during marine heatwaves, with major consequences for regional fishing industries.

All evidence suggests that marine heatwaves are linked to human mediated climate change and will continue to intensify with ongoing global warming. The impacts can only be minimised by combining rapid, meaningful reductions in greenhouse emissions with a more adaptable and pragmatic approach to the management of marine ecosystems.The Conversation

Dan Smale, Research Fellow in Marine Ecology, Marine Biological Association and Thomas Wernberg, Associate professor, University of Western Australia

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

Explainer: the rise of naked tourism



File 20170505 21635 1685lzw
Some travellers may forget that where they travel is not their home, and that cultural sensitivities may differ greatly.
Naked At Monuments/Facebook

Freya Higgins-Desbiolles, University of South Australia

In my American youth, there was a rude phrase describing kids acting up: “showing your butt”. It seems some tourists are now taking this literally.

Recently, tourists have been stripping down and photographing themselves at the world’s iconic locations to the bewilderment of some and the disgust of others. Social media is abuzz as tourists get snaps of their uncovered backsides at national parks, on top of mountains, and at World Heritage sites.

The desire to reveal one’s naked glory is not a new thing, as streakers at sporting events and the devotees of nude beaches and nudist camps demonstrate. But this trend of “naked tourism” reveals something more than just bare bottoms – and it may call for some active interventions.

Exposing the reasons for baring it all

In 2010, a French-born exotic dancer filmed herself stripping on the sacred monolith Uluru in central Australia. Some labelled this a “publicity grab”.

In early 2015, three young Frenchmen were charged with public exposure and pornography, given suspended sentences, fined, deported and banned from visiting Cambodia for four years after stripping down at Angkor Wat.

Lest we think this is a French thing, North Americans and Australians have bared their backsides at Machu Picchu in Peru. This led CNN to warn tourists to “watch out for bare butts”.

In the selfie era, attention-seeking and shock value are clear individual motivations. But perhaps there is more to it.

Social media is certainly encouraging the practice. A good example of this is the Naked At Monuments Facebook page, which describes its purpose as “we get naked around the world”. There is also the My Naked Trip blog. Together, these indicate naked tourism may be an emerging trend rather than an oddity.

Insulting the host community

Some travellers may forget that where they travel is not their home, and that cultural sensitivities may differ greatly.

While some cultures view revealing the body and its parts as an act of appreciation, others have quite different views. When tourists insist on imposing their values against their hosts’ wishes, profound emotions can be sparked. These may included anger, dismay and hurt.

In response to the stripping performance on Uluru, Aboriginal performer Jimmy Little communicated the hurt such a disrespectful act can inflict:

We are a proud race like every race in the world. We have sacred sites and we have deep beliefs that if people cross that line, they’re really almost spitting in your face, or slapping you in the face and saying ‘I can live my life the way I want to’.

In the Angkor Wat case, local authorities acted with some anger at the insult to the ancient, sacred temple complex. A spokeswoman for the Apsara Authority, the agency that manages Angkor Wat, said:

The temple is a worship site and their behaviour is inappropriate. They were nude.

How to (ad)dress this issue

The first line of defence is regulations with penalties that are enforced.

In the Angkor Wat case, the governing authorities enforced strong penalties on the young men for their actions. But for countries dependent on tourism, it takes considerable will to go down this path. The ongoing tolerance of bikinis on beaches in Muslim countries – albeit sometimes on restricted sites such as gated resorts or islands – attests to this.

Tourism between cultures is a moral space as much as it is a commercial one. The question is: in a time of creeping commercialism, individualism and me-oriented cultures, how can we ensure the cross-cultural encounters of tourism are respectful of the host’s cultures and values?

Codes of conduct are one tool for consumer education of travellers. The authority governing Angkor Wat responded to the naked tourists by updating visitor protocols in multiple languages.

Few know a Global Code of Ethics for Tourism exists. It claims:

Tourists have the responsibility to acquaint themselves, even before their departure, with the characteristics of the countries they are preparing to visit.

Tourism is based on hospitality, and this requires respect for hosts. They want visitors to voluntarily display respect.

Climbing Uluru is a great example of this. The Anangu traditional owners do not want visitors to climb this sacred place, but still do not ban it outright. One reason is deeply spiritual: the Anangu want visitors to respect their values and choose not to climb.

Such an approach has much to teach us about the meaning of travel between cultures. While today’s tourists travel freely to enjoy the world’s treasures, it does not mean such travel should be completely uninhibited.

The ConversationDifferent cultures hold different values, and the joy of travel should come from engaging with these differences and learning from them. Responsible tourism built on respect ensures a warm welcome.

Freya Higgins-Desbiolles, Senior Lecturer in Tourism, University of South Australia

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

What does the science really say about sea-level rise?


John Church, CSIRO and Peter Clark, Oregon State University

A recent high-profile study led by US climatologist James Hansen has warned that sea levels could rise by several metres by the end of this century. How realistic is this scenario?

We can certainly say that sea levels are rising at an accelerating rate, after several millennia of relative stability. The question is how far and how fast they will go, compared with Earth’s previous history of major sea-level changes.

Seas have already risen by more than 20 cm since 1880, affecting coastal environments around the world. Since 1993, sea level has been rising faster still (see chapter 3 here), at about 3 mm per year (30 cm per century).

One key to understanding future sea levels is to look to the past. The prehistoric record clearly shows that sea level was higher in past warmer climates. The best evidence comes from the most recent interglacial period (129,000 to 116,000 years ago), when sea level was 5-10 m higher than today, and high-latitude temperatures were at least 2℃ warmer than at present.

The two largest contributions to the observed rise since 1900 are thermal expansion of the oceans, and the loss of ice from glaciers. Water stored on land (in lakes, reservoirs and aquifers) has also made a small contribution. Satellite observations and models suggest that the amount of sea-level rise due to the Greenland and Antarctic ice sheets has increased since the early 1990s.

Before then, their contributions are not well known but they are unlikely to have contributed more than 20% of the observed rise.

Together, these contributions provide a reasonable explanation of the observed 20th-century sea-level rise.

Future rise

The Intergovernmental Panel on Climate Change (IPCC) projections (see chapter 13 here) forecast a sea-level rise of 52-98 cm by 2100 if greenhouse emissions continue to grow, or of 28-61 cm if emissions are strongly curbed.

The majority of this rise is likely to come from three sources: increased ocean expansion; glacier melt; and surface melting from the Greenland ice sheet. These factors will probably be offset to an extent by a small increase in snowfall over Antarctica.

With continued emissions growth, it is entirely possible that the overall rate of sea-level rise could reach 1 m per century by 2100 – a rate not seen since the last global ice-sheet melting event, roughly 10,000 years ago.

Beyond 2100, seas will continue to rise for many centuries, perhaps even millennia. With continued growth in emissions, the IPCC has projected a rise of as much as 7 m by 2500, but also warned that the available ice-sheet models may underestimate Antarctica’s future contribution.

The joker in the pack is what could happen to the flow of ice from the Antarctic ice sheet directly into the ocean. The IPCC estimated that this could contribute about 20 cm of sea-level rise this century. But it also recognised the possibility of an additional rise of several tens of centimetres this century if the ice sheet became rapidly destabilised.

This could happen in West Antarctica and in parts of the East Antarctic ice sheets that are resting on ground below sea level, which gets deeper going inland from the coast. If relatively warm ocean water penetrates beneath the ice sheet and melts its base, this would cause the grounding line to move inland and ice to flow more rapidly into the ocean.

Several recently published studies have confirmed that parts of the West Antarctic ice sheet are already in potentially unstoppable retreat. But for these studies the additional rise above the IPCC projections of up to 98 cm by 2100 from marine ice sheet instability was more likely to be just one or two tenths of a metre by 2100, rather than several tenths of a metre allowed for in the IPCC report. This lower rise was a result of more rigorous ice-sheet modelling, compared with the results available at the time of the IPCC’s assessment.

How stable are ice sheets?

Ocean temperatures were thought to be the major control in triggering increased flow of the Antarctic ice sheet into the ocean. Now a new study published in Nature by US researchers Robert DeConto and David Pollard has modelled what would happen if you factor in increased surface melting of ice shelves due to warming air temperatures, as well as the marine melting.

Such an ice-shelf collapse has already been seen. In 2002, the Larsen-B Ice Shelf on the Antarctic Peninsula disintegrated into thousands of icebergs in a matter of weeks, allowing glaciers to flow more rapidly into the ocean. The IPCC’s predictions had considered such collapses unlikely to occur much before 2100, whereas the new study suggests that ice-sheet collapse could begin seriously affecting sea level as early as 2050.

With relatively high greenhouse emissions (a scenario referred to in the research literature as RCP8.5), the new study forecasts a rise of about 80 cm by 2100, although it also calculated that this eventuality could be almost totally averted with lower emissions. But when the model parameters were adjusted to simulate past climates, the Antarctic contribution was over 1 m by 2100 and as much as 15 m by 2500.

Greenland’s ice sheet is crucially important too. Above a certain threshold, warming air temperatures would cause surface melting to outstrip snow accumulation, leading to the ice sheet’s eventual collapse. That would add an extra 7 m to sea levels over a millennium or more.

The problem is that we don’t know where this threshold is. It could be as little as 1℃ above pre-industrial average temperatures or as high as 4℃. But given that present-day temperatures are already almost 1℃ above pre-industrial temperatures, it is possible we could cross this threshold this century, regardless of where exactly it is, particularly for high-emission scenarios.

Overall, then, it is clear that the seeds for a multi-metre sea-level rise could well be sown during this century. But in terms of the actual rises we will see in our lifetimes, the available literature suggests it will be much less than the 5 m by 2050 anticipated by Hansen and his colleagues.

The wider question is whether the ice-sheet disintegration modelled by DeConto and Pollard will indeed lead to rises of the order of 15 m over the coming four centuries, as their analysis and another recent paper suggest. Answering that question will require more studies, with a wider range of climate and ice-sheet models.


John will be on hand for an Author Q&A between 2 and 3pm AEDT on Thursday, March 31, 2016. Post your questions in the comments section below.

The Conversation

John Church, CSIRO Fellow, CSIRO and Peter Clark, Distinguished Professor of Earth, Ocean, and Atmospheric Sciences, Oregon State University

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

Climate and the rise and fall of civilizations: a lesson from the past


Andrew Glikson, Australian National University

2015 will likely be the hottest year on record, beating the previous record set only in 2014. It is also likely to be the first year the global average temperature reaches 1℃ above pre-industrial temperatures (measured from 1880-1899). Global warming is raising temperatures, and this year’s El Niño has pushed temperatures higher still.

Although 2015 is unusually hot, 1℃ symbolically marks the halfway point to 2℃, widely considered to be the threshold of “dangerous” climate change. In fact an additional 0.5-1℃ is actually masked by sulphur aerosols which we have added to the atmosphere alongside greenhouse gases.

A temperature level of 1℃ (above pre-industrial levels) is similar to or warmer than the peak temperatures of the early Holocene epoch approximately 8,000-7,200 years ago. Studies of the early Holocene provide clues to what was such a world like.

The climate roller-coaster

The last ice age (or Last Glacial Maximum) peaked around 26,000 years ago. The earth warmed over the coming millennia, driven by an increase in radiation from the sun due to changes in the earth’s orbit (the Milankovic cycles) amplified by CO₂ released from warming water, which further warmed the atmosphere.

But even as the earth warmed it was interrupted by cooler periods known as “stadials”. These were caused by melt water from melting ice sheets which cool large regions of the ocean.

Marked climate variability and extreme weather events during the early Holocene retarded development of sustainable agriculture.

Sparse human settlements existed about 12,000 – 11,000 years ago. The flourishing of human civilisation from about 10,000 years ago, and in particular from 7,000 years ago, critically depended on stabilisation of climate conditions which allowed planting and harvesting of seed and growing of crops, facilitating growth of villages and towns and thereby of civilisation.

Peak warming periods early in the Holocene were associated with prevalence of heavy monsoons and heavy floods, likely reflected by Noah’s ark story.

We can’t measure historical temperatures directly, so scientists use oxygen measurements instead. Human civilisation arose in a period of mostly settled climate.
Bruce Railback’s Geoscience Resources

Early civilisations

The climate stabilised about 7,000 – 5,000 years ago. This allowed the flourishing of civilisations along the Nile, Tigris, Euphrates, Indus and the Yellow River.

The ancient river valley civilisations cultivation depended on flow and ebb cycles, in turn dependent on seasonal rains and melting snows in the mountain sources of the rivers. These formed the conditions for production of excess food.

When such conditions declined due to droughts or floods, civilisations collapsed. Examples include the decline of the Egyptian, Mesopotamian and Indus civilisations about 4,200 years ago due to severe drought.

Throughout the Holocene relatively warm periods, such as the Medieval Warm Period (900-1200 AD), and cold periods, such as the Little Ice Age (around 1600 – 1700 AD), led to agricultural crises with consequent hunger, epidemics and wars. A classic account of the consequences of these events is presented in the book Collapse by Jared Diamond.

It’s not just Middle Eastern civilisations. Across the globe and throughout history the rise and fall of civilisations such as the Maya in Central America, the Tiwanaku in Peru, and the Khmer Empire in Cambodia, have been determined by the ebb and flow of droughts and floods.

Changing the game

Greenhouse gas levels were stable or declined between 8,000-6,000 years ago, but then began to rise slowly after 6,000 years ago. According to William Ruddiman at the University of Virginia, this rise in greenhouse gases was due to deforestation, burning and land clearing by people. This stopped the decline in greenhouse gases and ultimately prevented the next ice age. If so, human-caused climate change began much earlier than we usually think.

Rise and fall in solar radiation continued to shift the climate. The Medieval Warm Period was driven by an increase in solar radiation, while the Little Ice Age was caused at least in part by a decrease.

Now we’ve changed the game again by releasing over 600 billion tonnes of carbon into the atmosphere since the Industrial Revolution, raising CO₂ concentrations from around 270 parts per million to about 400 parts per million.

One of the consequences of this rise is an extraordinary decline in the North Atlantic Ocean Circulation as cold water from melting of Greenland ice enters the sea. This could potentially lead to a collapse of the Atlantic Meridional Ocean Circulation and a short, regional human-caused cold period, or “stadial”, mostly affecting Europe and North America, similar to those that occurred in the early Holocene.

CO2 concentrations in November 2015. The blue circle shows an area of reduced CO2 corresponding to cooler sea temperatures in the North Atlantic Ocean.
NASA, Author provided

While this may sound like “global cooling”, a cold period could have deleterious effects on agriculture and is bound to be succeeded by further warming due to the high atmospheric CO₂ concentrations.

The current shift in state of the atmosphere-ocean-ice system signifies a return to conditions such as existed at the early Holocene, which were less favourable for farming. But it doesn’t stop there.

A further rise in CO₂ and temperature would lead to conditions which existed in the Pliocene before 2.6 million years ago, including many metres of sea level rise (around 10-40 metres), posing an existential threat to the future of civilisation.


Andrew will be on hand for an Author Q&A between 2 and 3pm AEST on Friday, December 11, 2015. Post your questions in the comments section below.

The Conversation

Andrew Glikson, Earth and paleo-climate scientist, Australian National University

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

Climate Change: Temperatures to Rise


The link below is to an article that reports on possible temperature rises associated with climate change over the next century.

For more visit:
http://news.mongabay.com/2013/0530-hance-temperature-range.html

Artic: Massive Rise in Freshwater


The amount of freshwater in the Artic is growing. The following article reports on the issue and what is happening in the far north of the globe.

For more visit:
http://www.bbc.co.uk/news/science-environment-16657122