lee wrote on Dec 6^th, 2018 at 2:52pm:


You keep trotting out this claim that the GRACE data "has a problem" ... but now the data has been corroborated by other data (ice core data) which - together with laser and ice penetrating radar confirm that the melt rate is bad and getting worse.

So your claim is now redundant. 


Further:

"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.

"A lot of our understanding of how [the Greenland ice sheet] is changing today comes from satellite observations, which are excellent but give only a limited view," he said.

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."

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.

"It will be responding to what we do now and in the next few decades for centuries and millenia."

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."

https://www.abc.net.au/news/science/2018-12-06/greenland-ice-sheet-melting-accel...

Captain Nemo wrote on Dec 6^th, 2018 at 4:04pm:


From the Nature article -

"Here we analyse refrozen melt layer stratigraphy in ice cores from central west Greenland (CWG) drilled between 2003 and 2015 to quantify annual melting over the last several centuries."

Same paper you referred to earlier. Just a different reporting agency.

Captain Nemo wrote on Dec 6^th, 2018 at 4:14pm:



Really? How did you infer that?

You repeat the same paper and it makes something else redundant?

Captain Nemo wrote on Dec 6^th, 2018 at 4:22pm:


Despite the GRACE data error?

Captain Nemo wrote on Dec 6^th, 2018 at 4:22pm:


You do understand "accelerating" means it is still going faster despite this study ending over 3 years ago?

GRACE data relies, in part, on a model predicting the depth of the bedrock. therefore the depth of the snow.

And the over  last two years the ice has been stable. An increase in 2017 and the current year about zero; that doesn't show the any ice loss accelerating.

Captain Nemo wrote on Dec 6^th, 2018 at 4:22pm:


Oh WERE? Not ARE?

Captain Nemo wrote on Dec 6^th, 2018 at 5:31pm:



So you don't think ice is dynamic? That the melting that occurred up to 2015 has continued unabated?

2015 doesn't corroborate any thing later.

"For this year, we calculated a total SMB of 517bn tonnes, which is almost 150bn tonnes above the average for 1981-2010, ranking just behind the 2016-17 season as sixth highest on record.

By contrast, the lowest SMB in the record was 2011-2012 with just 38bn tonnes, which shows how variable SMB can be from one year to another."

"However, it is likely that the relatively high end of season SMB will mean a zero or close-to-zero total mass budget this year, as last year."

http://sciencenordic.com/how-greenland-ice-sheet-fared-2018

No sign of accelerating ice loss there.

Of course you could add a third report of the same paper and say it provides definitive proof of years post 2015.

TheFunPolice wrote on Dec 6^th, 2018 at 8:06pm:

That's what non-linear means.

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.

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.

Captain Nemo wrote on Dec 6^th, 2018 at 11:08pm:



Ohh only the 1970's?    You know "during" is not the same as "since"?

Captain Nemo wrote on Dec 7^th, 2018 at 6:44pm:


You notice that didn't say that was " that melting occurred on a scale beyond what could possibly be explained by a fluctuation around a stable average of ice cover".


What about 2018 you were talking how well yesterday?