Is Greenland close to a climate tipping point?

Recent findings suggest climate change in Greenland may be approaching a tipping point, beyond which amplifying feedbacks could lead (probably over centuries) to complete melting of the ice sheet, raising sea level by about 7 meters.

In June, a team of glaciologists led by Jason Box predicted that we would see melting across 100% of the ice sheet’s surface area in summer within a decade (Box et al., in press). They drew that conclusion from data on the Greenland ice sheet’s surface reflectivity, or “albedo”, showing the surface has gotten darker over the last 12 years. A darker surface absorbs more heat, leading to more melting, causing albedo to decrease further, and so on in a vicious circle.

The ice naturally gets less reflective in summer because the shape of the snowflakes changes and meltwater reveals impurities beneath the surface, but in 2012 Greenland has become much darker than in previous summers. This is occurring particularly at high elevations, which were previously too cold to melt and indeed had gained ice from increasing snowfall. This month, at the height of the melt season, Greenland’s albedo has fallen far off the charts:


Figure 1: Surface albedo of the Greenland ice sheet (average of all elevations) between March and October in each year from 2000 to 2012. (Source: Ohio State University, 2012)

Then NASA satellites recorded a startling abrupt acceleration of melting over just four days. On 8 July, about 40% of the ice sheet’s area had surface melt. By 12 July, surface melt had spread to no less than 97% of the area, penetrating all the way to the centre of Greenland, three kilometers above sea level:


Figure 2: Map of Greenland showing the area experiencing surface melt on 8 July (left) and on 12 July (right). (Source: NASA, 2012)

“This was so extraordinary that at first I questioned the result: was this real or was it due to a data error?” said Son Nghiem of NASA’s Jet Propulsion Laboratory. The melting has been confirmed by independent measurements, and attributed to a warm air mass sitting over Greenland during that week. Ice cores show this to be a 1-in-150-year event.

It is not yet clear whether this single occurence is indicative of a trend; a year with greater snowfall could return the albedo to a more normal state. Nevertheless, the extraordinary events of recent weeks are cause for concern when considered in the context of Greenland’s ice melting at an accelerating rate for the last decade, losing more than 2 trillion tonnes in total:


Figure 3: Greenland ice sheet mass relative to the 2002-2011 average.

According to recent modeling (Robinson et al, 2012), the tipping point for eventual total melting of the Greenland ice sheet could be a global temperature of around 1.6°C above preindustrial. Worse, the lower end of the range of possibilities is only 0.8°C, equal to today’s global temperature.

There is broader evidence that no significant cushion remains between today’s climate and a dangerous level of warming. In the last interglacial age 125,000 years ago, called the Eemian, global temperature was only ~1°C warmer than preindustrial, ie. only a couple of tenths of a degree warmer than today (Hansen et al., in press). Yet the poles were several degrees warmer, there was no summer sea ice in the Arctic, and multiple studies using different methodologies (Kopp et al., 2009; Dutton & Lambeck, 2012) say sea level was 6-9 meters higher (meaning at least partial melting of the Greenland and/or West Antarctic ice sheets).

All this points to the conclusion we may already be getting close to a dangerous level of global warming. If humanity rapidly cuts global CO2 emissions to zero or near-zero, it might be possible to return the Earth to energy balance and prevent much further warming (Hansen et al., in press). If business-as-usual emissions continue for much longer, there is a risk that eventual melting of the Greenland ice sheet could become irreversible.

namnugenot wrote on Aug 4^th, 2012 at 2:47pm:


Why are you talking about Iceland?  It has a relatively temperate climate, or it did.

namnugenot wrote on Aug 4^th, 2012 at 2:47pm:


Which negative feedbacks are going to stop the climate from shifting beyond our comfort zone.

MOTR wrote on Aug 5^th, 2012 at 9:38am:


God 

MOTR wrote on Aug 5^th, 2012 at 9:41am:


Well...I didn't finish High School and failed subjects regularly when I attended. I was a great disappointment to my mother and my teachers but otherwise my formative years were quite a lot of fun.

Since then however I have managed to scrape up two university degrees without failing a unit... So thank you for your concern as to my intellectual shortcomings.

As for quantifying our comfort zone, I'd say we are just starting to breach it. We are heading into unknown territory with additional warming still in the system and with more CO2 generating another cycle of warming. We can't stop the warming already in the system but we can limit the amount of additional warming by reducing our emmissions of CO2.

http://www.columbia.edu/%7Ejeh1/mailings/2011/20110118_MilankovicPaper.pdf

MOTR wrote on Aug 5^th, 2012 at 6:59pm:


Sorry I took you literally.

But I don't know everything but I like to learn as much as I can.
Not sure of what point you are trying to make. Is this analogous to I don't know if there is a God, or in fact many Gods, or if there is a hell, if I am wrong as to the existence or identity of any deity I could burn in hell. That would be a consequence of my intellectual position.
What point I was trying to make is that it does not matter if I or you are wrong or right the decisions that are made, are made regardless and the consequences of those decisions will occur irrespective of whatever position we align ourselves to. The harm or otherwise I suffer is independent of my, or your, level of knowledge. Hence it is futile for me to care one way or another.
It is my choice to not bow low to your God no matter how fervent your evangelistic belief.
I am not a denier because you apply a standard of proof that pulls up short.

MOTR still not sure of what you mean by "comfort zone" and whether this is quantifiable? An Inuit may have a different idea of comfort to say a Dogon tribesman.

MOTR wrote on Aug 5^th, 2012 at 10:44pm:

Except, even your beloved IPCC says 'Climate models are unable to predict extreme events because they lack spatial and temporal resolution. In addition, there is no clear evidence that sustained or worldwide changes in extreme events have occurred in the past few decades'

But of course then go on to say the same ol BS

http://www.ipcc.ch/ipccreports/sres/regional/index.php?idp=232

There is no link to extreme weather event ans CO2. Do you have the data that says extreme weather events are more common now, are greater in intensity now or do you just have lives lost and cost and trying to use that as a "more = worse"?

^ I see you still think you're on top of everything.

Watch out for the next report.

http://www.columbia.edu/~jeh1/mailings/2011/20111110_NewClimateDice.pdf

"Our analysis shows that it is no longer enough to say that global warming will increase the likelihood of extreme weather and to repeat the caveat that no individual weather event can be directly linked to climate change. To the contrary, our analysis shows that, for the extreme hot weather of the recent past, there is virtually no explanation other than climate change."

The study, which was published by the Proceedings of the National Academy of Sciences, looks at the past six decades of global temperatures and finds what Hansen described as a "stunning" rise in the frequency of extremely hot summers.
It compared what is happening now to what was happening between 1951-1980. In those years, extremely hot temperatures covered less than 0.2% of the planet. Now, those temperatures cover about 10% of the land area, the study said.

It dismissed the idea that specific weather patterns are by themselves sufficient to explain today's extreme anomalies. Phenomena like La Nina have always been around, but large areas of extreme warming have only come about with climate change, the study said.

"The odds that natural variability created these extremes are minuscule, vanishingly small. To count on those odds would be like quitting your job and playing the lottery every morning to pay the bills," wrote Hansen.

Hansen directs research at the NASA Goddard Institute for Space Studies.

It comes from a peer reviewed paper, progs. Just because their conclusions dont fit with your smug view of the world doesn't mean the rest of us are going to ignore them.

Are you talking about the US dust bowl drought of the 1930s, an environmental disaster that was as much about poor land use practices as the meteorological conditions that precipitated it.

progressiveslol wrote on Aug 6^th, 2012 at 6:45am:


Going back to the 1930s wouldn't make any difference to a global study such as this. How about you read the paper first, progs.

It's about rare weather events becoming more common. Pointing to similar events in the past does not counter this argument. We all know these things happened, but why are they happening more frequently today.

Are these events actually more common?
They are certainly much better covered by the now global media where in the past it would get little coverage if at all or even ever known about.
Example we would have probably never heard of the 1976 Tangshan Earthquake that initially reportedly killed 1 million and later revised down to about 250,000, had our then former PM not been there in China at the time judging from the coverage at the time.

MOTR wrote on Aug 6^th, 2012 at 7:43pm:

Where is the data to that scientific method. Hansoms head.

progressiveslol wrote on Aug 5^th, 2012 at 11:05pm:


Except what MOTR cited isn't a climate model predicting the future, it's a statistical model of observed change, so you're entire premise is deeply flawed. Apples and oranges.

Quote:


The report was written between 1998 - 2005. Believe it or not, science progresses and evolves and known unknowns soon become knowns. The final submissions to the 2013 IPCC AR5 have just been taken, the Copenhagen Diagnosis was a precursor to the AR5, and the sorts of things that the AR4 couldn't quantify, such sea level changes from ice melt and the ability to attribute extreme weather events to the changing climate. A number of significant papers have been published since 2005 that have done exactly that, most notably with the Russian heatwave of 2010. Because while you guys were obsessing about blog posts and 15 year old hockey-sticks, the real scientific debate has progressed significantly. You know, the OTHER climate debate that you hguys do not participate in?

Ice loss from Greenland's vast sheet may happen mainly in short bursts, research by Danish scientists suggests.

They used aerial photos dating back to the 1980s to plot shrinking of glaciers around the island's northwest coast.

In the journal Science, they show that most of the ice loss happened in two periods - 1985-1993 and 2005-10 - with relative stability in between.

They say it will be hard to project sea level changes from Greenland ice melt until these patterns are deciphered.

A complete melt of the ice sheet would raise sea levels globally by about 7m, but it could take centuries for this to occur.

Last month, Nasa released evidence showing that ice melting had been observed across virtually the whole extent of the Greenland ice sheet, unprecedented in the satellite era.

Days earlier, an iceberg twice the size of Manhattan broke away from the Petermann glacier in northwest Greenland.

Dramatic though those events were, neither means much on its own for the long-term picture.

Hansen failed in 1988 with his failed predictions, so he up the cherry picking and political spin. Temps now are actually less than hansens lowest estimate/prediction which is of zero emmisions.

namnugenot wrote on Aug 7^th, 2012 at 11:05am:


Well, at least you got ONE thing right in that post. All I can really say is you should probably give up on the wild speculation and do some really quite cursory research into how climate science actually works. You might find it quite a revelation to, oh I don't know, pick up a text book and try reading it? .

Let's just say that at this stage you're doing it wrong and leave it at that.

Upton Sinclair wrote on Aug 7^th, 2012 at 6:40pm:

Things have progressed, like data manipulation. I seeno 1930's real observations in your graphs.

namnugenot wrote on Aug 7^th, 2012 at 7:07pm:


Great. Then pick one up from the geophysical section of your expansive library and read it. Then you won't have to base your views on wild speculation 

Upton Sinclair wrote on Aug 7^th, 2012 at 7:16pm:


I've read all my textbooks thank you.
But why the new found aversion to speculation it seems to be good enough for yourself and virtually everyone you quote?

Upton Sinclair wrote on Aug 7^th, 2012 at 7:39pm:


Sorry fore the delay, some of us have to earn a crust.
For someone as knowledgeable as yourself you don't actually put up much do you?, happy as you are to regurgitate parrot fashion with little or no understanding of applied knowledge.
However the textbooks that I have read seem to be in error so maybe you can help me out.
You have stated before that CO2 and temperature are well coorellated and there are no negative feedbacks and currently no possible other cause for global temperature change to explain any warming that may (or may not) be happening at present, at least you have responded with ridicule when other causes or feedbacks have been proposed. 

So here is a question for you for a change.
What was the temperature consistent with your coorellation and lack of negative feedback when the atmospheric CO2 was 7000ppm or even 2000ppm? Someone with a brain the size of your can no doubt come up with a ballpark figure plus or minus 10. If there are reasons for a temperature range lower then possibly you can state what these are?

namnugenot wrote on Aug 9^th, 2012 at 8:35am:


No one is saying there are no negative feedbacks, no one is saying CO2 is the only driver. You surely accept the output of the sun has an impact on temperatures and so too ocean currents. Both of these were very different back in the day.

You can't keep on putting up the same straw man all over the place and expect people to take you seriously.

I haven't come across anything in my reading that does anything remotely close to this. It would surely have to be a fairly broad estimate at best.

We could start with the luminosity of the sun and it's effect on temperatures. The sensitivity of temperature to CO2 would be less as the albedo effect would be negligible. And still we would have to consider currents.

You really have set a massive task. I'd say it would be hotter but by how much would be guess work on my part.

Another Ian Plimer

Quote:


Now that tells me that you really don't follow the basic atmospheric physics.

Nobody can answer your question, but this site can provide you with a  a quick and nasty understanding of planetary temperatures.

Try substituting 956 Wm-2  (70% of current Solar Constant). I've no idea what the Albedo factor would be for that period or the Earth's Keplerian elements for that matter ( and neither doess anybody else) but  just play with the variables and see if you can understand what's going on.

A Solar constant of 70% would be like placing the Earth halfway between its current orbit and that of Mars in terms of solar input alone.

Also look at the Tau values for water and carbon dioxide for the Earth and Mars while you're at it. He doesn't even touch on the tau for atmospheric dust on Mars, which has an enormous effect on the Martian climate.

http://bartonpaullevenson.com/NewPlanetTemps.html

Then there's the question of atmospheric density. At least on one occasion, the atmosphere of the Earth was severely ablated by factors such as the solar wind and major impacts. We can speculate on these things, and such articles even make our resident denialist Soren, come up with sarcastic remarks, but nobody really knows for sure very much about the planetary climatology of the Paleozoic. .

muso wrote on Aug 12^th, 2012 at 7:50pm:






You are coming around to what I have been saying all along.

Sorry just read the post further down.
Alluvial deposits...actual.
Greenhouse for that time...speculation.

namnugenot wrote on Aug 13^th, 2012 at 8:33am:


Mate, I cut my teeth on Geology. I studied it at University some 34 years ago, albeit just up to second year level and I have been following developments since then.  I even worked in the geochemical field for about 10 years.

Paleoclimatology is not hairbrained, but once you get back as far as the Mesozoic, it becomes very speculative. The plethora of varying theories on the paleoclimate of the Mesozoic alone should be enough to convince you of that.

I'd love to see your calculations. What atmospheric concentration of carbonyl sulphide do you use to come to that (highlighted) conclusion?   (I have of course heard of the faint sun paradox, but there has been a fair bit of work carried out on sulphur isotopes in the last decade.)