Ice mass the size of Greenland overlooked in climate models

http://www.latimes.com/news/science/sciencenow/la-sci-sn-climate-melt-20130624,0,4448493.story

by fraqed • 13 years ago

46 50 13 years ago

yread2• 13 years ago

The highly accurate dating and long time span of those fossils have allowed scientists to estimate fluctuations in sea level, and thus ice content, by extrapolating from variations in the ratio of oxygen isotopes

How do they estimate sea level from the ratio of oxygen isotopes? I've found just this http://en.wikipedia.org/wiki/Δ18O but it talks only about temperature, salinity and amount of evaporation

ovis• 13 years ago

Lighter isotopes preferentially get deposited on and form the ice sheets, so increases in ocean d18O correlate with glaciations.

kaybe• 13 years ago

The Rayleigh process describes the continous depletion of a reservoir through a fractionationing process - evaporation. It comes from the fact that heavier isotopes need slightly more energy for a phase change and thus get enriched in the fluid phase. In the case of water, it is mainly the stable O18 (as opposed to the abundant O16).

- Lighter isotopes evaporate easier and precipitate down on land. If they don't return to the ocean for a long time due to freezing and glaciation, the ocean has a higher ratio of heavy to light isotopes. More ice means lower ocean level, and since the ratio in the ocean is dependent on the missing water mass, calculations directly give the sea level.

Now how do we know what the isotope ratio was in the past?

In the oceans, there are those small animals (foraminifera) that build the oxigen from water into their shells. The Wikipedia article you found discusses this. (Another fractionation process, add more calculations here. Additional temperature dependance.) When they die, they float to the ocean floor and, in time, form sediments and eventually lime rock, which can be drilled for probes.

Furthermore, different kinds live in different depths, giving us even more information. This can be used for the past 70 million years, since that's the age of the oldest ocean floors. Almost (!) everything older has been subducted again. However, it is not easy to disentangle the temperature effect from the ice volume effect.

You can check those out, if you're interested, they explain more thoroughly than the wikipedia article:

shorter lecture script: http://www.iup.uni-heidelberg.de/institut/studium/lehre/Aqua...

long looooong version (read this and become a hydroscientist long): http://www-naweb.iaea.org/napc/ih/IHS_resources_publication_...

yread2• 13 years ago

Thanks for this comprehensive response (I didn't expect any less from HN ;)

I understood the part about O18 ending up less in the glaciers but I couldn't really grasp that if the water is in glaciers it isn't in the sea. I also thought it would be impossible to get rid of influence of the temperature (gradient with depth, latitude, ocean currents, ...) but it's probably not impossible, just difficult.

Also for anybody who doesn't click in the "loooooong" version has 6 volumes...

brittohalloran• 13 years ago

TLDR; Since the historical ice models, driven by fossil based sea level readings in Barbados, failed to account for the way the Earth's crust bends under the weight of a massive ice sheet on top of it, there was actually much more ice than previously thought. The exact implications aren't given, but it is implied that global warming is worse than we thought (has melted more ice).

tezza• 13 years ago

Not sure I get the same conclusion you do from the same article.

Worse than we thought?:

"It allows for the possibility that there is significant melting of the East Antarctic Ice Sheet," Rowley said. "Or it allows for a simple interpretation of no melting."

There is a simple interpretation of no melting.

Also, previously in the article they show that the models used to predict melting are suspect. The historical link of 'melt' being caused by CO2, may in fact be flattening caused by crust flexing.

Retric• 13 years ago

The crust flexes in response to freasing or melting but it don't not significantly buldge without reason.

rjknight• 13 years ago

The big melt was the end of the last ice age. That's far larger than anything that has yet happened due to climate change, so they're not really talking about ice that has been melted by global warming in the sense of post-industrial climate change.

However I think your basic assumption is right - this evidence would seem to suggest that, for a given amount of warming, we get more ice melt than we previously assumed.

TausAmmer2• 13 years ago

Change happens, all we can do is adopt, for now. Clear coastlines, clean low river banks.

If anything, extremes are going to ramp up in count, adopt and build infrastructure around it.

Paying gigantic amount of money to members that come together few times a year do not solves anything.

AutoCorrect• 13 years ago

I already have all the children I can comfortably support, and we plan on ADAPTING ;)

gizmo6862• 13 years ago

all we can do is adopt, for now.

You do realize that we are the first species to be the cause of a mass extinction event. We are also the only species to seriously consider how to terraform another planet [1]. What we need is the environmental movement to stop saying that we are actively destroying the world and the only thing we can do is stop, to one that says we have the ability to control the environment of our own world, and we should do so intelligently.

Keep in mind that we are not the first mass extinction event (the Permian–Triassic extinction event killed 96% of all species), but we are the first species to be able to exercise intelligent control over the climate. Also, while the environment will flourish after just like after every other extinction, it won't happen quickly enough for our scientist to be able to study life in the same way that they can with our pre-extintion bio-diversity.

[1] http://www.users.globalnet.co.uk/~mfogg/zubrin.htm

zdw• 13 years ago

Most people have a distorted idea of how big Greenland is - it's actually about the size of Saudi Arabia (http://en.wikipedia.org/wiki/List_of_countries_and_dependenc...) and gets distorted by most map projections to outlandish sizes (larger than South America in some).

lquist• 13 years ago

Most likely a result of the flaws of the Mercator projection (https://en.wikipedia.org/wiki/Mercator_projection#Mathematic...).

yellowbkpk• 13 years ago

Saying it's a result of a flaw in the Mercator projection is like saying zero being undefined is a flaw of the logarithm scale: it's not a flaw, it's a property.

If the projection doesn't work for your usecase, don't use it.

gverri• 13 years ago

I love how you can learn many things from Hacker News comments. Thank you very much sir.

codfrantic• 13 years ago

Found this useful site / app / tool on HN a couple weeks ago: http://mapfight.appspot.com/gl-vs-texas/greenland-texas-us-s...

shawndumas• 13 years ago

relevant xkcd : http://xkcd.com/977/

mtdewcmu2• 13 years ago

You mean most people that have actually looked at a map. How ironic that even a map can fill you with bad information.

snowwrestler3• 13 years ago

I think this headline (which comes from the article) is a bit misleading.

The total mass of the overlooked historical ice is about the mass of the Greenland ice sheet, but it was not all in one place like Greenland is. The article says's it's actually about a 10% error in a global historical reconstruction.

In addition, when I see the phrase "climate models", I think of the global simulations that scientists use to try to predict the future effect of climate change. This article seems to instead be about an historical reconstruction of a past climate.

prawks• 13 years ago

I think you're right, this article is concerned with determining how much ice has melted since the last glacial maximum, not how much more will melt.

lftl• 13 years ago

But aren't the two extremely tightly coupled? I know nothing of climatology, but it's hard for me to imagine how you would construct a future model that didn't rely massively on our picture of how the Earth reacted historically to different pressures. It would seem to me that adding a rather large chunk of ice, and changing past sea level measurements would have a large effect on the predicted future response of the system.

snowwrestler3• 13 years ago

Not as much as you might think. Models simulate a small range of time centered around the present, and are constructed by combining measurable physical quantities with physics equations. Basically, they attempt to simulate "the truth" starting from first principles.

Historical reconstruction is about really advanced ways of observing, estimating, and proxying data. The end product is a story of past climates, not a simulation or prediction.

It's sort of like the difference between an evolutionary biologist experimenting on fruit flies, and a paleontologist. You need both to get a complete picture of life, but neither's work depends much on the other.

In this case I'd be surprised if there is much impact on near-term climate predictions, because isostatic rebound is really slow at century timescales.

pmorici2• 13 years ago

I don't understand the emphasis on 'global warming' / 'climate change' as a marquee issue to drive action on environmental protection. The science behind it seems complex and because it relies so heavily on modeling leaves significant uncertainty in the mind of any lay person that reads about this stuff. I would think a much better way to promote environmental protection would be from the human health angle. Things like Erin Broncovich, Gas Land, (or whatever the air pollution equivalent is) etc... where there is clear documented proof about how environmental contamination is literally killing people. Seems like those would be more compelling reasons to act than some uncertain doom a century from now.

eli• 13 years ago

But they're different issues, right? The actions I would take to ensure my drinking water doesn't give me cancer are often different from those I'd take to prevent rising sea levels.

pmorici2• 13 years ago

Sorry those might have been bad examples. It's well documented that air pollution also causes human health issues. I'm saying that might be a better thing to highlight than the fact that that same air pollution might cause the tide to rise some unknown amount at some uncertain date in the future.

pyre4• 13 years ago

- Air pollution causes acid rain.

- Nobody likes "smog alert" days in large cities (LA, NYC, Toronto, etc). Everyone agrees that breathing in smog is bad.

- Burning coal releases radioactive isotopes into the atmosphere.

- Air pollution causes ocean acidification. This has the potential to wipe out entire species / aquatic ecosystems.

- Ocean dead zones are bad. Stop producing

- Significant amounts of methane come from 'cow farts.' Farming livestock for food makes less sense than farming plants. It takes more farmland to support livestock (e.g. something like 1000 lbs plants to produce 100 lbs of meat). [Not to mention all of the freshwater issues with irrigating all of the extra land used to feed the livestock.]

- Deforestation of topic rain forests in Indonesia need to stop because they are destroying Orangutan habitat, causing a possible extinction (except for those in captivity / zoos).

- Deforestation of the Amazon to make way for farmland / livestock grazing area needs to stop. It contributes a signification portion of the oxygen that we breath to the atmosphere.

DanBC2• 13 years ago

leaves significant uncertainty in the mind of any lay person that reads about this stuff.

Unfortunately that uncertainty is almost entirely created FUD from paid staff - the same people who worked for years to protect tobacco from science.

pyre4• 13 years ago

Like how all of our models of the universe were confirmed by probes like Voyager 1, and we learned nothing new. You're right. Models have no uncertainty (and scientists are always expert statisticians, while we're at it ;).

I'll at least say that the politicization of the issue hasn't helped the media to accurately report things about global warming.

talmand• 13 years ago

I would say both sides have had their hand in manipulating things to their own advantage.

saalweachter• 13 years ago

There's a closely related issue which is much more concrete: ocean acidification.

While you can argue that the effects of CO2 on global temperature are hard to understand and model correctly, CO2 leading to ocean acidification is straight forward high school chemistry (not that most of us did that great in high school chemistry). As the concentration of CO2 in the atmosphere goes up, so must the concentration of CO2 in the oceans. As the concentration of CO2 goes up in the oceans, the oceans become more acidic. You can calculate the exact increase using a couple of formulas from high school chemistry. No computer models or anything.

akjj• 13 years ago

The science behind it seems complex and because it relies so heavily on modeling

The thing is that you don't require complex modeling to get global warming. Energy comes to the earth from the sun. Energy's radiated out to space as infrared. Carbon dioxide blocks infrared and so increases the temperature.

As with everything, you can construct more accurate and more complicated models, but it's a myth that global warming only shows up as a consequence of the complexity. People had to start studying climate change for some reason, right? They did back of the envelope calculations first and then brought in the complicated models to try to quantify exactly the amount of climate change and what its effects would be.

Don't get me wrong, climate change has two big things working against it: the effects will not be observed directly for decades, and there's a lot of money from oil and gas which is fighting any attempts to take action. The former means that the evidence is based on modeling and the latter does everything it can to cast doubt on the models.

gizmo6862• 13 years ago

But what happens as a result of the increased heat and CO2? Does it lead to improved conditions for some plankton that causes the ocean to become more reflective of heat? Does it lead to some other gas being released that makes the atmosphere more reflactive? Does it accelerate the water cycle leading to increased cloud coverage, making Earth more reflective? Does it lead to the ice sheets melting causing the surface of the Earth to be less reflective. Does it free methane trapped withing the melting ice, increasing the greenhouse effect?

Has the politicization nature of the environmental movement made finding good science difficult and a skeptical public justified?

But, even given that the average temperature is increasing, what are the effects of that?

benjamincburns• 13 years ago

Yes. Although sadly I think we live in a world where you might get more effect by promoting the financial angle. I think the simplest argument anyone can make is that if you can do X or produce Y while consuming less energy than your competition, you'll come out ahead. If the entire world focused on this as a primary basis for long term competitive strategy, I think a ton of environmental issues would fall in line.

Either way, you're absolutely right. From a marketing standpoint, global warming is such a bad angle from which to promote environmental action.

clarkmoody• 13 years ago

I believe the President has already pivoted to "carbon pollution" in his latest speeches.

I do believe that we need much more scientific inquiry before making radical economic policy shifts. In just 40 years (since the 70s), the environmental lobby has been pushing:

  global cooling
  global warming
  climate change

And now it's "carbon pollution."

I'm definitely a skeptic when it comes to extrapolating historical record findings into the future, especially when politics is involved.

But the most compelling figure for me, concerning environmental protection, is the annual consumption of grain by livestock. A 1997 article[1] quotes a figure of 800 million people fed with the grain we are feeding livestock in America. So reducing meat consumption would save the energy used to produce the cattle but also the energy used to grow the grain to feed them.

It might also make us healthier, saving healthcare costs, but that is less settled than the figures for cattle grain consumption.

[1] http://news.cornell.edu/stories/1997/08/us-could-feed-800-mi...

mtdewcmu2• 13 years ago

I find peak oil to be the most chilling prospect of all. Global warming, even in the worst scenarios, doesn't predict anything dramatic in the next 50 years.

redwood• 13 years ago

Absolutely but keep in mind that CO2 has no direct detriment to health and as such has never been the focus of environmental movements...

In deciding "do we move from coal to natural gas" power plants: it's clear the immediate health benefits are immense. But the CO2 benefits are less significant... and as a result we should evaluate other options... or view natural gas as a sort of bridge tech.

Anyway you're right tho: the focus on CO2 can be a distraction ESPECIALLY in the developing world where toxic pollution is released into children's air/water constantly. We have a luxury, in the developed world, to see CO2 as the more significant threat.

Having spent the last year in Bangladesh (and admittedly a country that will be significantly impacted by climate change) I felt the focus on CO2 was completely misplaced. That country is toxic to its citizens in a number of ways and those problems should absolutely be higher priority to fix.

The greatest hypocrisy of all is when the wealthy western nations argue that the developing countries should develop green.

Sure, they should try to be green where it makes sense. But IF getting themselves out of the toxic rut they're in fastest requires fossil fuels (as we ourselves did) then it's complete insanity to suggest they not use the best tool at their disposal to do so.

binderbizingdos• 13 years ago

temperatures of the last 12'000 years: http://en.wikipedia.org/wiki/File:Holocene_Temperature_Varia...

josephlord• 13 years ago

At a plain reading this seems worthy science but not that newsworthy. Scientists do more (presumably good) work and adjust estimate of ice last ice-age by 10%, climate models may need minor tweak (direction not stated).

Did I miss something?

Ice mass the size of Greenland overlooked in climate models

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