Ocean Warming

[Robert Tulip]

From data in the links provided below, it appears that current temperature rise of the world ocean would be enough to raise a volume of water more than 100 times greater than Sydney Harbour from freezing to boiling point every day.

World Ocean Heat Content
Graph Credit: Adapted from S. Levitus et al., Geophys. Res. Letts.; © AGU 2012

For those who imagine that the stability of global air temperature at record high levels over the last decade means we can keep cooking the planet, think again - the heat is going into the oceans.

Science Magazine states

"Global warming contrarians remind the public that the world has not warmed all that much, if at all, during the past decade or so. But that's the atmosphere. Oceanographers with their thermometers in Earth's biggest reservoir of heat—the world's ocean—report in a paper to be published in Geophysical Research Letters that greenhouse warming has in fact been proceeding apace the past decade, not to mention the past half century. Ninety-three percent of the heat trapped by increasing greenhouse gases goes into warming the ocean, not the atmosphere. So taking the ocean's temperature is the most comprehensive way to monitor global warming. A group of National Oceanic and Atmospheric Administration scientists has revised and updated their decade-old compilation of temperature measurements from the upper 2000 meters of the world's ocean. Its store of heat (red line with error bars in graph above) steadily increased over the past 20 years. And the upper ocean has warmed so much in the past 50 years that its added heat would be enough to warm the lower atmosphere by about 36°C (thankfully a physically impossible feat).

This data is from an article since published in Geophysical Research Letters

GEOPHYSICAL RESEARCH LETTERS, VOL. 39, L10603, 5 PP., 2012

World ocean heat content and thermosteric sea level change (0–2000 m), 1955–2010 by S. Levitus National Oceanographic Data Center, NOAA, Silver Spring, Maryland, USA et al

Key Point: The rise in world ocean heat content since 1955 is due to the increase in atmospheric greenhouse gasses

- updated estimates of the change of ocean heat content and the thermosteric [heat induced] component of sea level change of the 0–700 and 0–2000 m layers of the World Ocean for 1955–2010.
- estimates are based on historical data not previously available, additional modern data, and bathythermograph data corrected for instrumental biases.
- heat content of the World Ocean for the 0–2000 m layer increased by ... 0.09°C.
- Ocean accounts for approximately 93% of the warming of the earth system since 1955.


A discussion of this material is at http://www.skepticalscience.com/Brea...ill_A_LOT.html

This post notes that the ocean is very big, and claims (with an apparent mathematical error) that the tiny temperature increase found by such studies has been enough to boil Sydney Harbour dry twice a day. Checking the numbers (see below) suggests the real magnitude is far worse.

From http://www.skepticalscience.com/pics/SydneyHarbour.png
To http://www.skepticalscience.com/pics...HarbourDry.png

How come? This massive heat increase is due to humans adding CO2 to the atmosphere, which lets light enter from the sun but does not let heat escape. CO2 is like a transparent blanket. "NOTHING ELSE FITS THE EVIDENCE... When the first analyses of Ocean Heat Content calculated from old temperature data from the oceans were first published in the early 2000's, they were described as the 'Smoking Gun'. Because they were. They are the primary observational evidence for Global Warming and the human nature of it."

The graph of World Ocean Heat Content above shows a very clear and obvious direction upwards. The average temperature of the ocean at any given time is hotter than at earlier times. The ocean is the main repository of heat on the earth surface, containing about 1.3 bilion teralitres of water, and is responsible for an estimated 93% of global warming. Unlike the atmosphere, which has been in a hot lull since the turn of the millennium, the ocean temperature has continued its remorseless increase. So showing that the "missing heat" from the last decade can in fact be seen in the main repository is correct analysis of the whole system.

0.1 degrees is small. But the ocean is very big. All of that extra heat, with its continued upward trend, has to have come from somewhere. Energy cannot be created or destroyed. As the scientific paper and summaries explain, the only plausible explanation for this obvious heating trend is the extra blanket we have added to the air through CO2 emissions.

The Sydney Harbour example is just a vivid way of showing how big this heat increase really is. The Harbour seems big, but it is tiny compared to the whole ocean. If all the extra heat measured in the whole ocean had been concentrated in a body of water the size of Sydney Harbour (known as a Sydharb in Australian water circles), 0.1 degrees over the whole ocean would reportedly be enough for 100 degrees every twelve hours.

Lets look at the calculations

0.1 Degrees for 1.3 billion teralitres over 50 years (world ocean)
= 100 Degrees for 1.3 million teralitres over 50 years
= 100 Degrees for 26,000 teralitres over 1 year
=~ 100 Degrees for 40 teralitres over 12 hours

In fact Sydney Harbour only contains 0.56 teralitres. So it seems there is a mathematical error in the Skeptical Science source I cited above, and the amount of measured ocean warming could bring to boiling point [edit to change - not boil dry] more than 100 Sydharbs every day, starting from freezing point [edit to change - not starting from ice]. While the GRL data only covers the top two km of the ocean, assuming no heat change for the deep ocean would only cut this estimate by half, to 50 Sydney Harbours per day.

Readers are welcome to check my calculations here. Once we understand the orders of magnitude, the steady continued rise in ocean temperature translates to a massive system heat increase, that has to go somewhere. We are accelerating the addition of the CO2 blanket, and now there are feedback loops from Arctic methane, etc. This illustration suggests we will hit climate tipping points faster than we realize.

[Ivan Viehoff]

From data in the links provided below, it appears that current temperature rise of the world ocean would be enough to raise a volume of water 1000 times greater than Sydney Harbour from freezing to boiling every day.

Sometimes physical measurements lack context, and comparisons of a nature such as this help people quantify and visualise them better. But on this occasion it is not useful at all. The amount of heat to boil a Sydney harbour is not a useful measure. Moreover, what really matters is that the heat is not all concentrated in Sydney harbour, it is spread across the ocean, and I do not offhand know how many Sydney Harbours fit into the ocean.

To me, much the most useful and helpful way of understanding how much heat the ocean has absorbed is "it has absorbed enough heat to raise its temperature by X degrees".

[HenrikOlsen]

Which is also a meaningless number when the temperature is kept llimited by ice melt-off so it doesn't rise even though heat is added.

Try how much ice melts every year instead.

[Robert Tulip]

Sometimes physical measurements lack context, and comparisons of a nature such as this help people quantify and visualise them better. But on this occasion it is not useful at all. The amount of heat to boil a Sydney harbour is not a useful measure. Moreover, what really matters is that the heat is not all concentrated in Sydney harbour, it is spread across the ocean, and I do not offhand know how many Sydney Harbours fit into the ocean.

To me, much the most useful and helpful way of understanding how much heat the ocean has absorbed is "it has absorbed enough heat to raise its temperature by X degrees".

Ivan, my post answered your questions already. The ocean temperature has risen by 0.1 degrees over the last fifty years. The volume of water in the world ocean is 2.3 billion times as big as Sydney Harbour.

The Sydney Harbour example is simply a way to say that if the measured diffuse heat increase, with its clear trend, was concentrated into a volume of water that people can imagine, then this is the quantum of increased heat.

[Ara Pacis]

Boiling Sydney Harbor may be a good example for Aussies, but not for anyone else who haven't any tangible experience with that locality. Perhaps hard-boiled eggs would be a better unit of measurement.

And HenrikOlsen's point is important. But I'd like to add that there needs to be a heat increase in ice from it's current temperature before it even gets to the melt temperature.

[Robert Tulip]

Boiling Sydney Harbor may be a good example for Aussies, but not for anyone else who haven't any tangible experience with that locality. Perhaps hard-boiled eggs would be a better unit of measurement.

And HenrikOlsen's point is important. But I'd like to add that there needs to be a heat increase in ice from it's current temperature before it even gets to the melt temperature.

This is about two issues

1. A peer reviewed report shows that the measurable upward trend of ocean warming has steadily continued over the last decade
2. Scale of this warming can be illustrated by rough order of magnitude comparisons.

The link I gave to Skeptical Science was the source for the Sydney Harbour comparison. Sydney Harbour contains just over half a cubic kilometer if that helps. A cubic kilometer or teralitre is a trillion litres.

The Skeptical Science article said the anthropogenic heating of the world ocean is enough to boil Sydney Harbour dry twice a day. This is an extraordinarily large amount of heat. However, my review of the numbers suggests that the level of heating is actually several orders of magnitude worse than this estimate.

Factors that could refine this estimate include the energy required to turn ice into water, whether the whole ocean is heating or just the top two kilometers as measured, and whether heating a litre by 100 degrees requires equal energy as heating 100 litres by one degree. I would be interested in comment on these points.

These refinements would be the difference between 100 Sydharbs or 1000, boiled from zero degrees every day, as a direct result of anthropogenic carbon emissions happening now. Either way it is a lot.

[danscope]

That heating certainly changed the jetstream this winter. We never had enough ice on the ponds and lakes to support a small cat. A skim coat that might form was gone durring the day. We had open water just about the whole winter.
There was a time when we had safe ice to skate on by Christmas. Not anymore. Jacques Clueseau

[ravens_cry]

And the scary thing is that gases are less soluble in warmer liquids, including dissolved carbon dioxide.

[geonuc]

I think perhaps Ivan was just making a general comment on the use of such oblique methods for presenting scientific conclusions.

...

In fact Sydney Harbour only contains 0.56 teralitres. So it seems there is a mathematical error in the source I used above, and the amount of measured ocean warming could boil dry more than 1000 Sydharbs every day, starting from ice. While the GRL data only covers the top two km of the ocean, assuming no heat change for the deep ocean would only cut this estimate by half, to 500 Sydney Harbours per day. ...

And as Henrik and Ara alluded, the bolded statement is not correct as the original premise does not seem to include the latent heat required to melt and boil water (I did not read the linked article - I'm only going off what you posted here). But yes, there does seem to be a mathematical error with respect to raising the volume of Sydney Harbour 100 degrees.

[HenrikOlsen]

My quibble is mainly that warming is the wrong thing to talk about when the issue really is heating.

[Robert Tulip]

Thanks for these points of detail. My purpose is to accurately illustrate the scale of global warming, by understanding the ocean as the main sink for terrestrial surface heat.

http://hypertextbook.com/facts/2007/LilyLi.shtml says the average ocean temperature is below 4° Celsius, while the average surface temperature is 17°. So lets disregard the question of melting ice. The analogy of boiling a quantum of ocean water should start from actual water temperature, not from ice.

Geonuc, I'm not sure why you think this illustration is oblique. The question is how to translate 0.1° warming over the entire world ocean to a scale that people can understand. What is slightly mind boggling here is the actual size of the ocean. Perhaps use of cubic kilometers would be a simpler measure. If we used megalitres/acre feet/swimming pools (50x10x2m) we could just multiply the teralitre figures by one million. Another measure is the actual volume and temperature of an Olympic swimming pool, 2.5 ML @ 27°. By that measure:

- The current global heat increase measured in the ocean due to CO2 emissions would be enough to boil 39 million Olympic swimming pools per day.

Henrik, I don't understand your distinction between warming and heating. Ocean heating is due to global warming.

The physics of this illustration may be too simplistic in some ways. Increase of 0.1° over the entire ocean over 50 years equates to increase of 100° per day for 70 cubic kilometers.* But I don't think this means that evaporation has increased that much. It assumes linear relation between heat and volume, and physicists could confirm in what respects this relation is actually linear. As I noted above, these figures are based on the assumption that total heat for 1° warming for 100 litres = 100° warming for 1 litre. So I pose the question, is this equation correct?

*I rechecked my calculations. It is not quite as bad as I thought - my figures in the OP would have meant 500 TL per day.

[geonuc]

Geonuc, I'm not sure why you think this illustration is oblique. The question is how to translate 0.1° warming over the entire world ocean to a scale that people can understand.

Using the amount of water contained in Sydney Harbour as a unit of volume to describe an effect on the world's oceans is oblique, not what you wrote. As Ivan said, without looking it up, who knows how many Sydney Harbours fit in the oceans? Better to use standard units.

[ravens_cry]

It's a bit of a conundrum for trying to reach the public consciousness.
On one hand, even if accurate, the Sydney harbour statement doesn't really help with the scale of the issue, while a 0.1 degree change doesn't sound like that much to a layman.

[Ara Pacis]

What's wrong with the standard unit of olympic-swimming-pools?

[ShinAce]

Thanks for these points of detail. My purpose is to accurately illustrate the scale of global warming, by understanding the ocean as the main sink for terrestrial surface heat.

Henrik, I don't understand your distinction between warming and heating. Ocean heating is due to global warming.

Terrestrial surface heat might be a set of words to avoid. Most will think you mean the increased temperature over land mass, which is what terrestrial means.

Warming = increase in temperature
Heating = increase in energy stored

I think Henrik is trying to say that global heating is the real problem, since global warming relies on the thermometer display.

Also note that you can make ice with a temperature of 0 Celsius, let it melt, and the whole time it's a mix of ice and water, you'll read 0 Celsius. It is heating, but not warming. It actually takes as much energy to melt a certain volume of ice as compared to raising its temperature by 100 degrees Celsius.

So that begs the question. In terms of energy, which takes more: heating the ocean surface by 0.09 degrees Celsius, or melting X tons of water?

Is the ocean the buffer for land temperature changes, or is it the ice caps, since they buffer the oceans?

I never gave it much thought, but it's a neat idea.

[HenrikOlsen]

Henrik, I don't understand your distinction between warming and heating. Ocean heating is due to global warming.

Heat has a specific meaning in thermodynamics which is very distinct from temperature.
Warming is about temperature, heating is about energy flows.
There are phase changes involved which means temperature is a meaningless measure for the heat involved.


Global warming is a misnomer as it's not about temperature (at the moment) but about an excess of energy entering the system.

Is the ocean the buffer for land temperature changes, or is it the ice caps, since they buffer the oceans?

I never gave it much thought, but it's a neat idea.

The thermohaline circulation means the temperature gets reset to around freezing each time it passes the North Atlantic and in that area ice is melting faster that it's generated.

[ravens_cry]

What's wrong with the standard unit of olympic-swimming-pools?

A bit too small scale I think.

[danscope]

The idea is to find a model which the public can wrap their head around. It's not easy.

[whimsyfree]

Boiling Sydney Harbor may be a good example for Aussies, but not for anyone else who haven't any tangible experience with that locality. Perhaps hard-boiled eggs would be a better unit of measurement.

The aussie media compare every volume of water with Sydney Harbor. I don't know why. I have seen Sydney Harbor and doing so gave me no idea of its volume. To look at it could be 20m deep or 2000m deep. I think it's a southern media conspiracy to mention that ugly city at every opportunity.

[Robert Tulip]

Sydney Harbour contains 560 gigalitres, or 0.56 cubic kilometres. The world ocean contains 1.3 billion cubic kilometers of water, or about 2.3 billion Sydney Harbours.

I used Sydney Harbour as a measure because it was the one used in the quite informative discussion source linked at the opening post, with the vivid pictures of the Harbour full and an imagined Harbour empty, although I think this imaginative canyon style picture is too deep. Sydney Harbour is a flooded estuary that was a river at the time of the last glacial maximum when the ocean was more than 100 meters lower. It is a well known tourist attraction that many people have sailed on or seen. Taking the Manly ferry - "7 Miles from Sydney and 1000 miles from care" - gives a rough sense of its size.

The overall point is to grapple with orders of magnitude for problems that most people are not used to dealing with. It is a bit like those astounding diagrams of the sun next to Arcturus and other giant stars, or how many atoms fit on the head of a pin, something to place our naive assumptions in a real framework by showing our human scale imagination does not easily comprehend real orders of magnitude. People do not think of Terra as 71% water covered, nor do they appreciate this water averages 4 kilometers in depth (that's 2.5 miles). So it should be helpful to put the tiny increase in ocean temperature into a scale people can relate to.

Swimming pools may not be the best measure, since some people assume an Olympic pool is one megalitre when in fact it is 2.5 megalitres. One cubic kilometer has enough water for 400,000 Olympic Pools. Measuring the world ocean in Opymic pools gives a number with 14 zeros. They say hunter gatherer communities had trouble imagining numbers bigger than anything they used. These days billions get used a lot, so a measure in the billions is probably best here.

Leaving aside any phase changes from ice to water to steam, the goal here is to find a vivid comprehensible way to show that the tiny ocean temperature rise of 0.1 degrees over fifty years actually represents a vast quantity of added heat.

It may be that the deep ocean has not warmed, but for purposes of simple explanation lets assume it has, unless anyone can suggest why not. If not, we should chop these numbers by 50% to factor in the proportion of the ocean deeper than 2 km.

Sticking to cubic kilometers or teralitres as a useful and comprehensible measure, we have

0.1 degrees warming over fifty years for 1.3 billion teralitres (average measured warming of top two km of world ocean)
= 100 degrees warming over fifty years for 1.3 million teralitres (same heat increase concentrated in 1/1000th the volume of water)
= 100 degrees warming over one year for 26000 teralitres (same heat increase divided by 50)
= 100 degrees warming over one day for 71 teralitres (same heat increase divided again by 365.25)

So, recognising the scale of the ocean, we see that in fact the average measured 0.1 degrees of anthropogenic warming is a lot, enough to raise 71 cubic kilometers of water from 0 to 100 degrees Celsius in a day.

The scientific paper attributes this entire heat quantum to anthropogenic emissions. Putting it in simple terms, it means that running our fossil fuel economy has the same heat impact on the planetary ocean as boiling 70 cubic kilometers of water from freezing point every single day. (That is 28 million Olympic size pools). As well, the ocean has not seen a temperature plateau like the atmosphere, but has kept on getting hotter.

We could also use other starting points, such as average ocean surface temperature of 17 degrees (boiling 85 teralitres per day) or stipulated Olympic Pool temperature of 28 degrees (boiling 39.5 million pools per day).

With emission growth rate accelerating, this measure can only increase. I hope this helps to put the scale of the emissions problem into some perspective.

[headrush]

So, recognising the scale of the ocean, we see that in fact the average measured 0.1 degrees of anthropogenic warming is a lot, enough to raise 71 cubic kilometers of water from 0 to 100 degrees Celsius in a day.

I don't think that is a useful or helpful comparison. The fact is that this warming has occurred over 50 years, not one day. If all the energy we get from the sun in a year were to hit us in one day, we would be toast. But as it doesn't, it presents no problem.
It is not really a shock that the oceans have been steadily warming. Water takes longer to warm and retains heat longer, well known to chemists and meteorologists the world over.

I don't disagree with the intention but making alarmist declarations often has the reverse effect to the one desired. The ocean is not boiling, anywhere. Adding an extra "if" to the statement just takes away from the more important point IMHO.

Perhaps a more apt analogy would be to calculate the number of average power plants it would take to generate the amount of extra heat that has been added to the ocean in its entirety ?

Alan

[Robert Tulip]

this warming has occurred over 50 years, not one day.

I think you misunderstood. 0.1° of ocean warming in 50 years is the heating equivalent of boiling 0.1% of the world ocean over that time, ie boiiling 1.3 million cubic kilometers of water from zero. That equates to boiling 71 cubic kilometers of water per day. It is just one day's worth of ocean warming, on average, that has the heat equivalent of boiling 71 cubic kilometers.

71 teralitres x 365.25 days x 50 years = 1,300,000 teralitres. 1,300,000 x 1000 = 1,300,000,000, the number of cubic kilometers of water in the sea.

It is not an inaccurate or alarmist claim, unless you see some error in the calculations?

[HenrikOlsen]

I think you misunderstood. 0.1° of ocean warming in 50 years is the heating equivalent of boiling 0.1% of the world ocean over that time

BZZZZZT!

Time to go back to your thermodynamics books.

Raising the temperature 0.1°C is the equivalent to raising the temperature of 0.1% to just below boiling.
Actually boiling that amount takes hellamuch more heat on top of that.

[Ara Pacis]

(That is 28 million Olympic size pools).

See, that image is perceptual and properly mind-boggling. You want large numbers of something that does seem large to the average human. Modern humans don't have to be able to wrap their head around the whole shebang, they just need to be able to wrap their heads around the smallest unit that you're using multiples of, something that Sydney Harbor is not good for to the majority of Earthlings.

[Robert Tulip]

BZZZZZT!

Time to go back to your thermodynamics books.

Raising the temperature 0.1°C is the equivalent to raising the temperature of 0.1% to just below boiling.
Actually boiling that amount takes hellamuch more heat on top of that.

Thanks Henrik. My last post included the caveat "leaving aside any phase changes from ice to water to steam", meaning raising the temperature to just below boiling. Sorry for the imprecision.

A useful physics assignment question could be: The rise in ocean temperature since 1955 contains the heat equivalent of boiling how much surface water?

ETA: Information on phase change energy input for water is at http://hyperphysics.phy-astr.gsu.edu...rmo/phase.html

[Ara Pacis]

It's not just ocean warming we need to be worried about. Now we've got record lake warming

From NOAA

AT THE SOUTH BUOY...WATER TEMPERATURES THIS PAST WEEK HAVE BEEN
CONSISTENTLY IN THE 50S...PEAKING AT 59.2 DEGREES LAST WEDNESDAY.
BASED ON DATA GOING BACK TO 1982...THE AVERAGE WATER TEMPERATURE
AT THE SOUTH BUOY FOR MAY 21ST THROUGH 25TH IS 41.0F...SO THE
SOUTHERN PORTIONS OF THE LAKE ARE RUNNING 10F TO ALMOST 20F ABOVE
THE 30 YEAR AVERAGES. ONLY ONCE BEFORE ON RECORD HAVE WATER
TEMPERATURES BEEN THIS WARM ANY EARLIER IN THE SEASON AND THAT WAS
BACK ON MAY 16 1991 WHEN WATER TEMPERATURES BRIEFLY REACHED 60F.

(Yelling not mine)

[headrush]

I think you misunderstood. 0.1° of ocean warming in 50 years is the heating equivalent of boiling 0.1% of the world ocean over that time, ie boiiling 1.3 million cubic kilometers of water from zero. That equates to boiling 71 cubic kilometers of water per day. It is just one day's worth of ocean warming, on average, that has the heat equivalent of boiling 71 cubic kilometers.

71 teralitres x 365.25 days x 50 years = 1,300,000 teralitres. 1,300,000 x 1000 = 1,300,000,000, the number of cubic kilometers of water in the sea.

It is not an inaccurate or alarmist claim, unless you see some error in the calculations?

I see no error in your calculations, leaving aside phase change, but ...
This is merely a thought exercise, no body of water has been raised to boiling point, so the scenario does not reflect reality. I understand the point you're making, I just think it would be better expressed in a different way. At present it sounds alarming, but as soon as the listener realises that this rise has occurred over 50 years and has only raised the average temperature by one tenth of one degree, they will see no urgency to the matter. They may even start to think that the whole problem has been inflated. That would be bad for all of us. The naysayers may be wrong but in the end we need to convince them.

[Tensor]

It's not just ocean warming we need to be worried about. Now we've got record lake warming

From NOAA
(Yelling not mine)

59?????? It never got to that in July and August. Back when I was living just north of Chicago in the sixties and seventies.

[Robert Tulip]

it sounds alarming, but as soon as the listener realises that this rise has occurred over 50 years and has only raised the average temperature by one tenth of one degree, they will see no urgency to the matter.

Thanks, your response reminds me of the comment that CO2 is only about 400 parts per million, or one part per 2500 of the atmosphere, so we should not worry about something so tiny.

My point here is to take this 'tiny' change and present its systemic effect as the energy equivalent within a more human scale.

Lets put it another way. If the amount of heat increase measured in the ocean every day as a result of human emissions was applied to the main London Olympic swimming pool, how long would it take to raise it to boiling point?

The answer is about two milliseconds. In the minute it takes the Olympians to swim one hundred metres, our emissions put enough extra heat into the world climate to bring more than 20,000 Olympic pools to boiling point.

That is a simple statement of fact. Yes it is alarming, but it is not an exaggeration.

Now that Olympic time clocks are measuring to the millisecond, it should be a simple matter to calculate precisely how long our global warming heat inputs would take to boil a pool. While many people are more interested in sporting contests than the fate of the planet, setting the scale of global warming against such human contexts helps to illustrate the size of the problem.

[profloater]

Since the oceans are a heat store, the amount of energy stored is related to the absolute temperature plus the latent heat effects and at that comparison 0.1 degree is not a huge percentage change in the total heat stored. It might be more interesting or alarming to note
the effect of evaporative heat loss from the surface of the oceans to the air which if I remember correctly in empirical terms (i.e. including increased wind speeds) goes with T^4. I remeber this figure from reservoirs, I am not sure about the factor for whole oceans. Maybe someone can improve.