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We could see early warning signs of the collapse of a key component of the global climate up to 250 years in advance, a new study has shown – ample time to either prevent or prepare for the consequences of abrupt climate change. The University of Exeter study analyzed the Atlantic Meridional Overturning Circulation (AMOC), sometimes referred to as the global ocean conveyor belt, in a highly-complex and realistic simulation model, and identified the likely mechanisms that would drive such a collapse.
The AMOC is crucial to Earth's climate. It transports heat from the tropics to the cooler North Atlantic and then up into the atmosphere, driven by differences in density in ocean layers that are caused by salinity and temperature variations. Without it, the surface air temperature of the North Atlantic region would cool by around 1-3 degrees Celsius, with isolated pockets cooling by up to 8°C.
As freshwater glacial ice melts or surface temperature increases, the density of surface waters in the North Atlantic shrinks. This appears to be happening now, and it's triggering a positive feedback loop that accelerates the process, though there's little evidence as yet of any impending collapse.
In the long run, though, the system could cross a threshold known as "critical slowing down," which would make it unstable and likely lead to relatively sudden collapse – on the scale of months. The researchers sought to identify the early warning signals that precede this phenomenon.
originally posted by: Metallicus
How do they even know what factors contribute to a collapse?
It sounds made up.
The fact that sea levels are rising probably won't come as a huge surprise. But we now have some much-needed historical context for the melting icecaps and rising waters...and there's zero doubt that, in geological history, higher sea levels meant higher temperatures.
An international team led by researchers at the University of Pennsylvania created the first ever reconstruction of the last 2,000 years worth of changing sea levels. They were able to do this thanks to tiny fossils known as foraminifera, which can be found in sediment cores in North Carolina's coastal marshes.
To make sure these fossils could be used as an accurate barometer of sea level at different points in history, they compared the last 80 years worth of foraminifera data with contemporaneous North Carolina tidal gauge records. Once they had created the reconstructive technique, they then compared that with 300 years of global sea level records.
Here's what they found. The sea level changed very little between 200 and 1,000 C.E., then it began to climb by about half a millimeter per year for 400 years. This fits well with a known climate spike that began in the 11th century, which is known as the Medieval Climate Anomaly. Sea levels drop again in the mid-17th century, which is right on time for the advent of the Little Ice Age, which lasted from 1645 to 1715.
That drop continues until the beginning of the late 19th century, when the industrial revolution was in full swing. At that point, sea levels start climbing at an average rate of two millimeters per year, and the seas have been rising that much ever since. The research confirms what has often been assumed, that there's a very strong link between sea levels and temperatures. More worryingly, it also seems to confirm just how uniquely pronounced the current climate change really is.
I think a good question to ask is what happened the last time the glaciers melted? This has all happened before. I know it's not PC to bring it up, but it is a fact.
Some even fear that global warming may be able to trigger the type of abrupt massive temperature shifts which occurred during the last glacial period: a series of Dansgaard-Oeschger events – rapid climate fluctuations – may be attributed to freshwater forcing at high latitude interrupting the THC. The Younger Dryas event may have been of this sort, too. (See the discussion of chaos theory for related ideas.) However, these events are believed[by whom?] to have been triggered by massive freshwater discharges from the Laurentide ice sheet, rather than from the melting of polar sea-ice and precipitation changes associated with the increased open water in global warming. Meltwater events aside, the climate deterioration into the last ice age appears to have taken about 5,000 years. Also, in coupled Atmosphere-Ocean General Circulation Models the THC tends to weaken somewhat rather than stop, and the warming effects outweigh the cooling, even locally: the IPCC Third Assessment Report notes that "even in models where the THC weakens, there is still a warming over Europe". Model runs in which the THC is forced to shut down do show cooling – locally up to 8 °C (14 °F)— although the largest anomalies occur over the North Atlantic, not over land. However, climate models are not sufficiently sophisticated at present to include climatic factors which give these predictions veracity; e.g., the recent return of deep convection to the subpolar gyre in both the Labrador and Irminger seas and the growing ice mass of Greenland. Studies of the Florida Current suggest that the Gulf Stream weakens with cooling, being weakest (by ~10%) during the Little Ice Age.
originally posted by: boymonkey74
When people are being swept into the sea because they live near the coast and thousands being displaced due to climate change their will still be ignorant fools still wanting to run their 4x4s proclaiming climate change is bunk.
Future generations if you read this iam sorry.
..I hope your generation are not as ignorant mine.
originally posted by: mcChoodles
A fellow bio student from college called me five years ago and said to prepare for a new ice age.
Somehow his research showed that there wa massive glacier melting at the north pole prior to the last mini ice age.
The freshwater influx drove the gulf stream much further south before it turned right and headed towards England.
Without the warmer currents, the north polar ice caps grew very quickly. The added ice reflected more infrared waves back into space and in short order, a mini ice age occurred.
At the time, I thought he was nuts. With the last few brutal winters in the Mid-Atlantic region and this past very cool summer, I think he was right.
Funny thing is his fellow professors didn't want to review his reaserch. It sucks being a iconoclast scientist who follows data instead of dogma, I guess.