19/09/2017

Global Ocean Circulation Appears To Be Collapsing Due To A Warming Planet

ForbesTrevor Nace

Global ocean circulation appears to be slowing. NASA
Scientists have long known about the anomalous "warming hole" in the North Atlantic Ocean, an area immune to warming of Earth's oceans. This cool zone in the North Atlantic Ocean appears to be associated with a slowdown in the Atlantic Meridional Overturning Circulation (AMOC), one of the key drivers in global ocean circulation.
A recent study published in Nature outlines research by a team of Yale University and University of Southhampton scientists. The team found evidence that Arctic ice loss is potentially negatively impacting the planet's largest ocean circulation system. While scientists do have some analogs as to how this may impact the world, we will be largely in uncharted territory.
AMOC is one of the largest current systems in the Atlantic Ocean and the world. Generally speaking, it transports warm and salty water northward from the tropics to South and East of Greenland. This warm water cools to ambient water temperature then sinks as it is saltier and thus denser than the relatively more fresh surrounding water. The dense mass of water sinks to the base of the North Atlantic Ocean and is pushed south along the abyss of the Atlantic Ocean.
Schematic of the Atlantic meridional overturning circulation. Wikipedia
This process whereby water is transported into the Northern Atlantic Ocean acts to distribute ocean water globally. What's more important, and the basis for concern of many scientists is this mechanism is one of the most efficient ways Earth transports heat from the tropics to the northern latitudes. The warm water transported from the tropics to the North Atlantic releases heat to the atmosphere, playing a key role in warming of western Europe. You likely have heard of one of the more popular components of the AMOC, the Gulf Stream which brings warm tropical water to the western coasts of Europe.
Evidence is growing that the comparatively cold zone within the Northern Atlantic could be due to a slowdown of this global ocean water circulation. Hence, a slowdown in the planet's ability to transfer heat from the tropics to the northern latitudes. The cold zone could be due to melting of ice in the Arctic and Greenland. This would cause a cold fresh water cap over the North Atlantic, inhibiting sinking of salty tropical waters. This would in effect slow down the global circulation and hinder the transport of warm tropical waters north.
Measured trend in temperature variations from 1900 to 2012. NOAA
Melting of the Arctic sea ice has rapidly increased in the recent decades. Satellite image records indicate that September Arctic sea ice is 30% less today than it was in 1979. This trend of increased sea ice melting during summer months does not appear to be slowing. Hence, indications are that we will see a continued weakening of the global ocean circulation system.
This scenario of a collapse in AMOC and global ocean circulation is the premise for the movie "The Day After Tomorrow." As a disclaimer, the plot line in which much of New England and Western Europe gets plunged into an ice age is significantly over exaggerated and unrealistic on human time scales.
While geologists have studied events in the past similar to what appears to be happening today, scientists are largely unsure of what lies ahead.

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Asia's Glaciers To Shrink By A Third By 2100, Threatening Water Supply Of Millions

The Guardian - Agence France-Presse

High mountains of Asia hold biggest store of frozen water outside the poles and feed many of the world’s great rivers, including the Ganges
The Asian high mountains are already warming more rapidly than the global average. Photograph: Alamy Stock Photo
Asia’s mountain glaciers will lose at least a third of their mass through global warming by the century’s end, with dire consequences for millions of people who rely on them for fresh water, researchers have said.
This is a best-case scenario, based on the assumption that the world manages to limit average global warming to 1.5C (2.7F) over pre-industrial levels, a team wrote in the journal Nature.
“To meet the 1.5C target will be a task of unprecedented difficulty,” the researchers said, “and even then, 36% (give or take 7%) of the ice mass in the high mountains of Asia is projected to be lost” by 2100.
With warming of 3.5C, 4C and 6C respectively, Asian glacier losses could amount to 49%, 51% or 65% by the end of the century, according to the team’s modelling study.
The high mountains of Asia comprise a geographical region surrounding the Tibetan plateau, holding the biggest store of frozen water outside the poles.
It feeds many of the world’s great rivers, including the Ganges, the Indus and the Brahmaputra, on which hundreds of millions of people depend.
Nearly 200 nations adopted the Paris agreement in 2015, which sets the goal of limiting warming to a level “well below” 2C, while “pursuing efforts” to achieve a lower ceiling of 1.5C.
Earth’s surface has already warmed by about 1C, according to scientists.
For high warming scenarios, experts predict land-gobbling sea-level rise, worsening storms, more frequent droughts and floods, species loss and disease spread.
The Asian high mountains, the new study said, were already warming more rapidly than the global average.
A global temperature rise of 1.5C would mean an average increase in the region of about 2.1C, with differences between mountain ranges – all of which will warm by more than 1.5C.
The Hindu Kush mountain range would warm by about 2.3C and the eastern Himalayas by 1.9C, the study forecast.
“Even if temperatures stabilise at their current level, [glacier] mass loss will continue for decades to come,” the researchers added.
For the high mountain glaciers to survive, “it is essential to minimise the global temperature increase”.
Swaths of south Asia and China depend on meltwater from Himalayan glaciers for drinking water, electricity generation and irrigation.
At the same time, the regions are also vulnerable to more intense flooding from accelerated glacier melt, combined with heavier rains and superstorms boosted by global warming.
A study in July in the journal Nature Climate Change said there was only a 5% chance of holding global warming under 2C. For 1.5C, the odds were about 1%.
On current trends, some experts project Earth is on track to warm by about 3C.

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How Did We Get Into This Energy Mess, And How Do We Get Out Of It?

Fairfax - Tony Walker

Let's start with the smelly, dead chicken the Turnbull government is seeking to hang around the Shorten opposition's neck.
In a variation of the children's party game, pass the parcel, or, should we say, pass the chicken, Malcolm Turnbull and his Energy Minister, Josh Frydenberg, are seeking to impose on their political opponents responsibility for an energy mess, including crippling power bills.
The public could care less about the source of power as long as the lights remain on. Photo: Liam Driver
This is self-serving politics.
Culpability for two decades of policy paralysis going back to the Howard government's failure to ratify the Kyoto Protocol – setting the tone for an aimless debate on climate and energy – rests with the political class of all stripes, including the hapless Greens.
In their failure back in 2009 to support reasonable proposals for an emissions trading scheme known as the Carbon Pollution Reduction Scheme (CPRS), the Greens scarred the Rudd prime ministership, contributed to Turnbull's demise as opposition leader and helped prolong a lost decade in energy policy.
Our purpose is not to argue the merits, or otherwise, of the case for sustaining AGL's Liddell power station in the Hunter Valley beyond a five-year shelf life, but to ask a simple question.
How did we get into this mess, and how do we get out of it?
In answering this question, history is important.
As far back as the 1990's the Coalition debated in its internal processes the merits of an emissions trading scheme as a means of setting a price on carbon, thereby constructing a rational energy policy for the 21st century. Several proposals were discussed in cabinet, one in 2000 and the other in 2003.
Neither made it past the opposition of cabinet climate sceptics, including then prime minister John Howard himself.
However, by 2007 with defeat in prospect, Howard capitulated.
On July 17, 2007 he said: "Implementing an emissions trading scheme and setting a long-term goal for reducing emissions will be the most momentous decision Australia will take in the next decade."
More than a decade later, Howard's forecast remains stillborn, ensnared by rancid politics in which Kevin Rudd squibbed an opportunity for a double dissolution election on the Senate's rejection of his CPRS.
To her great cost, Julia Gillard introduced a carbon tax after having pledged not do so. Then Tony Abbott replaced it with a Direct Action plan to compensate emitters who reduced their carbon footprint, or got out of the emitting business altogether.
In one of politics' ironies, the problematical Direct Action plan – described by Turnbull in 2009 as "bullshit" – is subject to an internal review by the government with a result due by the end of the year.
Perhaps nothing has confused Turnbull's credentials more as an environmentally-responsible small 'l' liberal centrist than his positions on energy and climate policy under a Coalition agreement struck with the Nationals after he deposed Abbott.
Basically, Turnbull fell into line with his predecessor's policies on climate change, carbon taxes and emissions reduction targets.
Implicit in all of this was support for the coal industry.
On occasions, Turnbull has sought to edge away from these commitments such as when his energy minister talked about an emissions intensity target.
Under fire from his right flank over this heresy, Turnbull quickly disavowed any such idea.
In this latest period, we are witnessing an intense bout of blame-shifting in light of the most politically sensitive of cost of living issues – power prices.
The Turnbull government is also seeking to shield itself from the fury that would surely follow a summer of power outages due to insufficient baseload power.
In the debate about baseload power provided by coal-fired power stations versus renewables, the public could care less about the source of power, as long as the lights remain on.
What all this points to is a failure by successive Federal governments, Labor and conservative, to develop a national energy policy that provides a reasonable balance between conventional coal and gas-fired sources and renewables within a framework that satisfies Australia's international emissions-reduction obligations.
Speaking of gas, one of the more surprising aspects of the current debate is the lack of focus on gas as a cleaner energy alternative to coal. According to chief scientist Alan Finkel's National Electricity Market report, gas accounts for just 10 per cent of the country's power generation.
That could be increased significantly using existing modified infrastructure at a much lower emissions cost than coal: gas emits around 400kg/MWh compared with 1272kg/MWh for the highest emitting coal-fired plants.
One might have thought the country's secure energy future lies in a mix of gas and renewables, with Australia's ageing coal-fired plants being phased out over time, leaving aside the government vacillation on a Clean Energy Target recommended by Finkel.
Turnbull might serve the national interest more effectively by putting aside politics for a moment and listening to expert advice – from Finkel and the power generation industry itself – about the best energy mix.
Bullying corporate representatives in the manner of an early NSW governor named Bligh may serve a political purpose, but it hardly solves the problem.

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