To say it's been a bad year for climate change news is an understatement.
Both the UN Environment and the Intergovernmental Panel on Climate Change (IPCC) sounded the alarm over the dire climate trajectory we're on, and the huge efforts needed to limit warming to 2 degrees Celsius above pre-industrial levels.
And in June, research published in Nature pointed to a tripling of the rate of melting of the Antarctic ice sheet over the last five years.
Now, new research published in Nature today has confirmed a similar trend is occurring in the Greenland ice sheet.
Researchers used ice cores to create a 350 year continuous analysis of the melting rate of ice in central west Greenland.
An ice core is a sample taken from an ice pack with a hollow drill, revealing a cross-section that effectively looks back in time, a bit like the rings of a tree.
They found that over the last 20 years, the rate of melting has been as much as five times as high as pre-industrial melt rates, and that the rate of melting is increasing, according to researcher Luke Trusel from Rowan University in the United States.
"The main conclusion that we found is that it's now melting more in recent decades than any time in the last four centuries, and probably more than any time in the last seven to eight thousand years," Dr Trusel said.
According to their ice core samples, 2012 was "unambiguously" the most intense melt year on record in Greenland.
An increased rate of melting was detected in the ice cores beginning in the mid-1800s, which was around the same time as the onset of industrial-era Arctic warming.
But it was only during the 1970s that the melting clearly breached the natural range of variability.
In other words, we expect to see some differences in melting between years, but during the 1970s that melting occurred on a scale beyond what could possibly be explained by a fluctuation around a stable average of ice cover.
The albedo effect describes the phenomenon where dark surfaces absorb more heat than reflective white surfaces like ice and snow.
As ice melts, the darker ground beneath absorbs more energy from the sun, which causes even more melting — creating a feedback loop.
"The response of the ice sheet to a warming climate is not linear," Dr Trusel said.
"What that means practically is that, say we have half a degree of warming today, that would produce twice as much or more melting than half a degree that occurred sometime in the past."
Most previous research has used satellite observations and computer modelling to calculate the rate of melting in Greenland.
This new research has allowed scientists to cross-reference their satellite observations against physical ice cores, according to Dr Trusel.
Being able to trace melting rates back 350 years is a particular strength of this latest research, according to Matt King from UTAS, who wasn't involved in this study.
"We haven't had a widespread assessment, certainly going back this far almost to the time of Shakespeare," Professor King said.
"From these type of measurements we can learn a lot about how fast things are changing in Greenland."
And understanding how fast the ice sheet is melting is crucial for us to prepare for the impact of rising sea levels in the future, according to Professor King.
According to this year's IPCC report, warming of between 1.5C and 2C locks in the eventual total deglaciation of Greenland.
This means that eventually, the Greenland ice sheet will cause oceans around the world to rise by an average of more than 7 metres.
"So there's two questions: Have we passed the threshold [and] secondly how fast is that [melting] going to occur," Professor King said.
"It could be thousands of years or it could be hundreds of years and that's the sort of question we're trying to answer."
In the Arctic and Greenland, signatures of warming have been detected beginning in the 18th century, and average summer temperatures have risen by around 2C since the 1990s.
It's a process called polar amplification, and it means that small increases in global average temperature will have the greatest affect in polar regions.
And there are other positive feedbacks to consider as well.
Most of us know that as we climb a mountain, the temperature drops, and vice versa.
The Greenland ice sheet is up to 3 kilometres thick in places, but as it melts, the surface layer altitude is reduced.
In turn the surface comes in contact with warmer air and melting is increased.
The complexity of ice melting, and the potential affects on the planet of the melting Greenland ice sheet mean that we need to seriously consider what impacts our actions today will have on the future, according to Dr Trusel.
"We may think of Greenland as being remote and not very important, but when Greenland changes it impacts coastlines across the globe," Dr Trusel said.
According to Professor King, this research is yet another wake-up call from a year of loud wake-up calls.
"This does remind everyone in the global community once again that very unusual things are happening on this planet."
Both the UN Environment and the Intergovernmental Panel on Climate Change (IPCC) sounded the alarm over the dire climate trajectory we're on, and the huge efforts needed to limit warming to 2 degrees Celsius above pre-industrial levels.
And in June, research published in Nature pointed to a tripling of the rate of melting of the Antarctic ice sheet over the last five years.
Now, new research published in Nature today has confirmed a similar trend is occurring in the Greenland ice sheet.
Researchers used ice cores to create a 350 year continuous analysis of the melting rate of ice in central west Greenland.
An ice core is a sample taken from an ice pack with a hollow drill, revealing a cross-section that effectively looks back in time, a bit like the rings of a tree.
They found that over the last 20 years, the rate of melting has been as much as five times as high as pre-industrial melt rates, and that the rate of melting is increasing, according to researcher Luke Trusel from Rowan University in the United States.
"The main conclusion that we found is that it's now melting more in recent decades than any time in the last four centuries, and probably more than any time in the last seven to eight thousand years," Dr Trusel said.
According to their ice core samples, 2012 was "unambiguously" the most intense melt year on record in Greenland.
An increased rate of melting was detected in the ice cores beginning in the mid-1800s, which was around the same time as the onset of industrial-era Arctic warming.
But it was only during the 1970s that the melting clearly breached the natural range of variability.
In other words, we expect to see some differences in melting between years, but during the 1970s that melting occurred on a scale beyond what could possibly be explained by a fluctuation around a stable average of ice cover.
Over 7 metres of sea-level rise locked in Greenland ice sheet
Significantly, they've confirmed that the increasing melting rate is following an exponential trajectory, caused by positive feedbacks like the albedo effect, according to Dr Trusel.The albedo effect describes the phenomenon where dark surfaces absorb more heat than reflective white surfaces like ice and snow.
As ice melts, the darker ground beneath absorbs more energy from the sun, which causes even more melting — creating a feedback loop.
"The response of the ice sheet to a warming climate is not linear," Dr Trusel said.
"What that means practically is that, say we have half a degree of warming today, that would produce twice as much or more melting than half a degree that occurred sometime in the past."
Most previous research has used satellite observations and computer modelling to calculate the rate of melting in Greenland.
This new research has allowed scientists to cross-reference their satellite observations against physical ice cores, according to Dr Trusel.
Being able to trace melting rates back 350 years is a particular strength of this latest research, according to Matt King from UTAS, who wasn't involved in this study.
"We haven't had a widespread assessment, certainly going back this far almost to the time of Shakespeare," Professor King said.
"From these type of measurements we can learn a lot about how fast things are changing in Greenland."
And understanding how fast the ice sheet is melting is crucial for us to prepare for the impact of rising sea levels in the future, according to Professor King.
According to this year's IPCC report, warming of between 1.5C and 2C locks in the eventual total deglaciation of Greenland.
This means that eventually, the Greenland ice sheet will cause oceans around the world to rise by an average of more than 7 metres.
"So there's two questions: Have we passed the threshold [and] secondly how fast is that [melting] going to occur," Professor King said.
"It could be thousands of years or it could be hundreds of years and that's the sort of question we're trying to answer."
'Very unusual things are happening on this planet'
Although climate change has so far resulted in warming of around 1C on average since pre-industrial levels, that warming has not been uniform.
In the Arctic and Greenland, signatures of warming have been detected beginning in the 18th century, and average summer temperatures have risen by around 2C since the 1990s.
It's a process called polar amplification, and it means that small increases in global average temperature will have the greatest affect in polar regions.
And there are other positive feedbacks to consider as well.
Most of us know that as we climb a mountain, the temperature drops, and vice versa.
The Greenland ice sheet is up to 3 kilometres thick in places, but as it melts, the surface layer altitude is reduced.
In turn the surface comes in contact with warmer air and melting is increased.
The complexity of ice melting, and the potential affects on the planet of the melting Greenland ice sheet mean that we need to seriously consider what impacts our actions today will have on the future, according to Dr Trusel.
"We may think of Greenland as being remote and not very important, but when Greenland changes it impacts coastlines across the globe," Dr Trusel said.
According to Professor King, this research is yet another wake-up call from a year of loud wake-up calls.
"This does remind everyone in the global community once again that very unusual things are happening on this planet."
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