Lethal Heating: 06/14/18

14/06/2018

Antarctica Loses Three Trillion Tonnes Of Ice In 25 Years

BBC - Jonathan Amos | Victoria Gill

Artwork: European satellites in particular have an unbroken record going back to 1992 ESA

Antarctica is shedding ice at an accelerating rate.

Satellites monitoring the state of the White Continent indicate some 200 billion tonnes a year are now being lost to the ocean as a result of melting.
This is pushing up global sea levels by 0.6mm annually - a three-fold increase since 2012 when the last such assessment was undertaken.
Scientists report the new numbers in the journal Nature.
Governments will need to take account of the information and its accelerating trend as they plan future defences to protect low-lying coastal communities.
The researchers say the losses are occurring predominantly in the West of the continent, where warm waters are getting under and melting the fronts of glaciers that terminate in the ocean.
"We can't say when it started - we didn't collect measurements in the sea back then," explained Prof Andrew Shepherd, who leads the Ice sheet Mass Balance Inter-comparison Exercise (Imbie).
"But what we can say is that it's too warm for Antarctica today. It's about half a degree Celsius warmer than the continent can withstand and it's melting about five metres of ice from its base each year, and that's what's triggering the sea-level contribution that we're seeing," he told BBC News.
Space agencies have been flying satellites over Antarctica since the early 1990s. Europe, in particular, has an unbroken observation record going back to 1992.
These spacecraft can tell how much ice is present by measuring changes in the height of the ice sheet and the speed at which it moves towards the sea. Specific missions also have the ability to weigh the ice sheet by sensing changes in the pull of gravity as they pass overhead.
Imbie's job has been to condense all this information into a single narrative that best describes what is happening on the White Continent.
Glaciologists usually talk of three distinct regions because they behave slightly differently from each other. In West Antarctica, which is dominated by those marine-terminating glaciers, the assessed losses have climbed from 53 billion to 159 billion tonnes per year over the full period from 1992 to 2017.
On the Antarctic Peninsula, the finger of land that points up to South America, the losses have risen from seven billion to 33 billion tonnes annually. This is largely, say scientists, because the floating ice platforms sitting in front of some glaciers have collapsed, allowing the ice behind to flow faster.
East Antarctica, the greater part of the continent, is the only region to have shown some growth. Much of this region essentially sits out of the ocean and collects its snows over time and is not subject to the same melting forces seen elsewhere. But the gains are likely quite small, running at about five billion tonnes per year.
And the Imbie team stresses that the growth cannot counterbalance what is happening in the West and on the Peninsula. Indeed, it is probable that an unusually big dump of snow in the East just before the last assessment in 2012 made Antarctica as a whole look less negative than the reality.
Globally, sea levels are rising by about 3mm a year. This figure is driven by several factors, including the expansion of the oceans as they warm. But what is clear from the latest Imbie assessment is that Antarctica is becoming a significant player.
"A three-fold increase now puts Antarctica in the frame as one of the largest contributors to sea-level rise," said Prof Shepherd, who is affiliated to Leeds University, UK.
"The last time we looked at the polar ice sheets, Greenland was the dominant contributor. That's no longer the case."
In total, Antarctica has shed some 2.7 trillion tonnes of ice since 1992, corresponding to an increase in global sea level of more than 7.5mm.
The latest edition of the journal Nature has a number of studies looking at the state of the continent and how it might change in a warming world.
One of these papers, led by US and German scientists, examines the possible reaction of the bedrock as the great mass of ice above it thins. It should lift up - something scientists call isostatic readjustment.
New evidence suggests where this process has occurred in the past, it can actually constrain ice losses - as the land rises, it snags on the floating fronts of marine-terminating glaciers.
"It's like applying the brakes on a bike," said Dr Pippa Whitehouse from Durham University. "Friction on the bottom of the ice, which was floating but has now grounded again, slows everything and changes the whole dynamic upstream. We do think the rebound (in the future) will be fast, but not fast enough to stop the retreat we've kicked off with today's warming.
"Ocean warming is going to make the ice too thin for this process to help."
In Imbie's last assessment, the contribution of Antarctica to global sea-levels was considered to be tracking at the lower end of the projections that computer simulations had made of the possible height of the oceans at the end of the century. The new assessment sees the contribution track the upper end of these projections.
"At the moment, we have projections going through to 2100, which is sort of on a lifetime of what we can envisage, and actually the sea-level rise we will see is 50/60cm," said Dr Whitehouse. "And that is not only going to impact people who live close to the coast, but actually when we have storms - the repeat time of major storms and flooding events is going to be exacerbated," she told BBC News.

Links

National Energy Guarantee 'Clumsy, Inefficient', Says VEPC's Mountain

Fairfax - Peter Hannam

The Turnbull government's proposed revamp of Australia's electricity sector has many unresolved issues just two months before states and territories are supposed to sign off on the plan, the head of the new Victorian Energy Policy Centre said.
Bruce Mountain, who will launch the new centre in Melbourne on Wednesday, said the National Energy Guarantee (NEG) as designed would not reduce coal generation and would "only slightly increase renewable capacity".
"It's clumsy and inefficient," and deliberately set up to hide a market price for emissions, Dr Mountain told Fairfax Media. The government's own forecasts say "it will move nothing in a meaningful sense".

Bayswater power station in the Hunter Valley: what role coal? Photo: Nick Moir

Among Dr Mountain's concerns - to be detailed in a speech at the launch - was the lack of a penalty for non-compliance, undermining the policy's credibility.
While retailers would be obligated to reduce the emissions intensity of the electricity they purchase, the reliance on a registry rather than a market to settle shortfalls would also hinder transparency. One consequence would be to hobble the development of financial instruments, potentially raising costs.
The overall approach was "without precedent [and is] projected to make effectively no difference to greenhouse gas emissions relative to business as usual", Dr Mountain will say in his speech.
By contrast, Australia had a readymade market for the Renewable Energy Target (RET), which would be much more effective than the NEG, he said.
The creation of the new policy centre - based at Victoria University and mostly funded by the Andrews Victorian government - is likely to increase scrutiny on the NEG in the final months of its development.
Josh Frydenburg, the federal environment and energy minister, wants states and territories to agree on the plan by August 10.
The scheme aims to reduce power prices while improving security of the grid as the share of renewable energy sources increase. It also intends to ensure the electricity sector - sources of about one-third of Australia's carbon emissions - meets Australia's Paris climate commitment of cutting 2005-level emissions 26-28 per cent by 2030.

Energy crunch time: Federal environment and energy minister Josh Frydenberg will be pressing for approval for the National Energy Guarantee in August. Photo: Janie Barrett

“There is an unprecedented cross section of support for the NEG," Mr Frydenberg said.
“The independent Energy Security Board’s (ESB) modelling found that the guarantee would add over 3200 megawatts of additional renewable capacity compared to business as usual and would result in lower prices," he said, adding that household power bill would fall by an average of $400 by 2020.

'Short timeframe'
Dr Mountain said the requirement of the electricity sector to meet only an average emissions reduction goal "would impose costs - probably large - elsewhere in the economy in order to deliver the Paris commitment".
The Australian Energy Council, which represents major generators, said the NEG had made major design advances since its conception late last year with the Energy Security Board set up to drive it.
Still, "the [board] are working to a remarkably short timeframe to deliver a largely completed reform", a council spokeswoman said.
Among the council's concerns, as detailed in its submission, the body would prefer only the high-level structure and legislation be set up now. The more complex details would then be set up within the National Electricity Rules over time.
"Whilst our cautious approach is preferred where feasible, we have to acknowledge that the ESB has a difficult juggling act to retain support across so many parties, and are therefore under pressure to deliver it in considerable detail before the next COAG meeting," the spokeswoman said.
Another concern for Dr Mountain was the current NEG design - unlike the RET - could provide a windfall for old hydro stations owned by Snowy Hydro and Hydro Tasmania. While the current low emissions ambition of the Turnbull government meant the transfers would be minimal, that would change if a future Labor government took over and significantly increased the electricity sector's emissions-reduction load.

High costs
Tackling the NEG issues will be only part of the new policy centre's priorities.
Tackling the high costs of electricity in general will be another, with Australian states now enduring the high power charges before tax in the world, according to data analysed by Dr Mountain.
The retailers charges amounted to about $423 of the almost $1400 typical residential bill in Victoria as of May 2017, Dr Mountain's data showed. That compared with $73 for state and federal environmental schemes, $415 for networks and $263 for the actual wholesale generation charge.

Typical retail electricity prices in 2017 at market rates

Source: Mountain (2017)

Of those retailers' charges, Victoria was the highest in Australia, followed by NSW, and considerably higher than other nations. The European Union's average retailer charge of about 2 Australian cents per kilowatt-hour compared was a fraction of Victoria's 12 cent charge, and more than 8 cents in NSW.

Retailers' charge for typical residential electricity user

Source: Mountain (2017)

Links

Antarctic Ice Melting Faster Than Ever, Studies Show

The Guardian - Matthew Taylor

Rate of melt has accelerated threefold in last five years and could contribute 25cm to sea-level rises without urgent action

Scientists warns time is running out to save the Antarctic and its unique ecosystem, with potentially dire consequences for the world. Photograph: Daniel Beltrá/Greenpeace

Ice in the Antarctic is melting at a record-breaking rate and the subsequent sea rises could have catastrophic consequences for cities around the world, according to two new studies.
A report led by scientists in the UK and US found the rate of melting from the Antarctic ice sheet has accelerated threefold in the last five years and is now vanishing faster than at any previously recorded time.
A separate study warns that unless urgent action is taken in the next decade the melting ice could contribute more than 25cm to a total global sea level rise of more than a metre by 2070. This could lead eventually to the collapse of the entire west Antarctic ice sheet, and around 3.5m of sea-level rise.
Prof Andrew Shepherd, a lead author of the study on accelerating ice loss, said: “We have long suspected that changes in Earth’s climate will affect the polar ice sheets. Thanks to our satellites our space agencies have launched, we can now track their ice losses and global sea level contribution with confidence.”
He said the rate of melting was “surprising.”
“This has to be a cause for concern for the governments we trust to protect our coastal cities and communities,” Shepherd added.
The study, published in Nature, involved 84 scientists from 44 international organisations and claims to be the most comprehensive account of the Antarctic ice sheet to date. It shows that before 2012, the Antarctic lost ice at a steady rate of 76bn tonnes per year - a 0.2mm per year contribution to sea-level rise. However since then there has been a sharp increase, resulting in the loss of 219bn tonnes of ice per year - a 0.6mm per year sea-level contribution.
The second study, also published in Nature, warns that time is running out to save the Antarctic and its unique ecosystem - with potentially dire consequences for the world.
The scientists assessed the probable state of Antarctica in 2070 under two scenarios. The first in which urgent action on greenhouse gas emissions and environmental protection is taken in the next few years, the second if emissions continue to rise unabated and the Antarctic is exploited for its natural resources.
The scenario which plays out largely depends on choices made over the next decade, on both climate-change and on environmental regulation, they conclude.
Co-author Profe Martin Siegert, from the Grantham Institute, said: “Some of the changes Antarctica will face are already irreversible, such as the loss of some ice shelves, but there is a lot we can prevent or reverse.
“To avoid the worst impacts, we will need strong international cooperation and effective regulation backed by rigorous science. This will rely on governments recognising that Antarctica is intimately coupled to the rest of the Earth system, and damage there will cause problems everywhere.”
As well as being a major cause of sea-level rise, scientists say the oceans around Antarctica are a key “carbon sink” - absorbing huge amounts of greenhouse gases helping to mitigate the impacts of climate change.
Siegert said: “If the political landscape of a future Antarctica is more concerned with rivalry, and how each country can get the most out of the continent and its oceans, then all protections could be overturned.
“However, if we recognise the importance of Antarctica in the global environment, then there is the potential for international co-operation that uses evidence to enact changes that avoid ‘tipping points’ – boundaries that once crossed, would cause runaway change, such as the collapse of the west Antarctic ice sheet.”

Links