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anthropogenic
global warming,
and ocean acidity

 

 

 

a briefing document

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click to see all the indexanthropogenic global warming, and ocean acidity is one in a series of briefing documents investigating the indicators, science, analysis and argument surrounding global warming.
One of a grouping of documents on global concerns at abelard.org.
on energy on global warming
On housing and making living systems ecological
sustainable futures briefing documents
Tectonics: tectonic plates - floating on the surface of a cauldron
click to see all the indexIndex
butterfly wings
flat earthers
the case against the accused
looking at the evidence
present road transport highest climate forcer, industry lowest - allegedly
ice and sediment cores
other considerations
february 2007 UN IPCC report 4 part 1 - links
medieval warming, the atlantic conveyor and “the maunder minimum”
explanatory notes on global temperature variation graphs
cloud effects
on paleoclimate
atmospheric CO2
milankovitch cycles
tectonic plates
variations in sun energy output
ocean acidity
table: atmospheric carbon dioxide
bibliography and brief reviews
end notes
 


 



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butterfly wings

Humans love patterns. They seek to simplify the world, which allows them to manage without doing too much thinking or counting. Their simple machines are manufactured to go round and round and round on fixed tracks, like the motor in a car. Humans have tried to apply simple models to the universe in order to simplify, thus the sun goes around the Earth in 365 days. But, of course, it doesn’t, it goes around the sun in 365¼ days and a little bit, and a little bit of that. And then, of course, that timing varies ever so slightly over the millennia; and that little bit of variation starts to mount up over a billion years.

Then, as humans learn more, they learn about variations within variations, as you will see in the Milankovitch cycles section. They look at a few ice ages and think maybe the Milankovitch cycles caused them, so for a century or two they struggle valiantly to make these two things fit together. Every time, a bit more information makes the fit not quite so tidy. Month by month and year by year, our understanding of ice age data increases. The more data we gather, the more untidy the real world looks.

Very small changes in the path of a Mars shot will expand to millions of miles by the time rocket reaches its destination. Very tiny (accidental) differences to where a seed falls in a forest can determine whether the seed becomes a 200-foot giant, or is eaten by a squirrel. Small differences can determine whether a species survives and thrives, or is never heard of again. Small changes can determine whether a tornado gathers and accumulates, finding a path to New Orleans, or whether it peters out in mid-ocean, or takes a slightly different route to a less annoying landfall. Neither do we know much at all what starts or stops an ‘ice age’. Very possibly some trivial or accidental process goes into positive feedback, this leaves plenty of work for the future.

We still struggle to forecast weather a few days ahead, let alone understand a world of hundreds of thousands of years ago - or billions of years - from a few ice or sediment core samples. This is the real world, and the real world of advancing modern science. It is not a world of certainties or a few easy patterns. But despite all these uncertainties, we do expect the sun to rise in the morning and we do believe that we have a reasonable grasp on anthropogenic global warming. Do not become confused between areas of knowledge where we are not completely blind and areas where much that is written is bordering on hubris and speculation.

Human knowledge comes on a scale of knowing rather a lot about rather a little, to knowing very little about rather a lot. It is sane to keep constant awareness of whether you are in the shallow end of a heated swimming pool, or in the middle of the North Atlantic during a raging storm.

flat earthers

Flat earthers make up all sorts of speculative reasons why “there is no anthropomorphic global warming” [AGW]. Many of these ‘reasons’ are based on poorly grasped comments from sloppy fossil media and web sources. The purpose of this subsidiary briefing document is to provide the means for you to follow up these specious claims in more detail, should you wish. There is a great mass of discussion in books and appropriate journals, and increasingly upon the Net.

In a sense, this subsidiary document is a review of the elements that are not primarily emphasised as being relevant to modern anthropogenic global warming concerns!

There is most definitely anthropogenic warming.

  • Empirical statement 1: Greenhouse gases [GHGs] cause global warming.
  • Empirical statement 2: Humans are increasing GHGs considerably.

But we still do not know many of the details. While the consensus is strongly that AGW is a reality, it should be kept in mind that a limited amount of global warming may prove to be a net benefit.

So, moonbats write all sorts of nonsense attempting to ‘be different’ and suggest all manner of mechanisms whereby AGW is not happening,
or it is not significant,
or it’s not faaaair,
or it wasn’t invented here.

Here is an example from the Cato Institute, which is often dubiously supported by all sorts of industrial interests that would rather not change (or pay for) their filthy externalisation of costs.

But there is still that awkward problem - reality!!

There is real global warming with considerable empiric evidence -

the world is getting hotter.

So the moonbats must make all manner of claims that it is really about the sun’s output changing or 101 other excuse-me’s.

Now, every adequate scientist knows full well that, with complicated systems, establishing causal links is no cake-walk.

But when sane scientists see two phenomena tracking each other, they tend to try to work out if there is a linkage.

Meanwhile special interests, for instance the cigarette industry, struggle for decades to dismiss the ever-growing links between illnesses and tobacco.

Or the media industry tries to deny a link between violence on film and violence in the playground.

Or the filthy fossil fuel companies struggle to dismiss any links between their filth and global warming.

But, back to that pesky reality again. The filth also kills millions right now.

Meanwhile, the West is increasingly dependent on a backward area of the world for energy, an area which is also a source of considerable current aggravation.

Among other lies spread by the nay-sayers is the claim that global warming scientists claim more than they know. This is a good way to pretend that there really is ‘no problem’.

But, in fact, serious climate scientists make no such claims.click to return to the index

 

the case against the accused

It has taken decades to bring responsibility home to the tobacco drug pushers, and it ain’t over yet.

We have still a way to go before bringing responsibility home to the media corporations.

How long before sufficient causal evidence is deemed enough to force responsibility on the filthy dangerous fossil fuel industry?

Meanwhile, back in the real world again, planetary temperatures are rising.
Meanwhile, back in the real world, we do know some about the effects of GHGs.
Meanwhile, back in the real world, we do know we are adding considerably to such gases.

But of course, we can’t really be certainly sure, can we? Maybe it’s all to do with university grants, or mickey mouse!

    While the general consensus is that global warming is occurring and is in great part caused by human activity [anthropogenic], anyone who tells you that global warming is easily understood and proven (or disproven), followed by some trite reason, simply does not understand the situation.

    “The most prevalent reasonably scientific question about current climate changes is ‘how do we know that this isn’t natural variability?’.
    [The best answer given was: ]”

    • “[...] the causes of ‘natural variability’ - whether the sun, volcanoes or ocean changes - should be detectable (but haven’t been),

    • and that the anthropogenic ‘hypothesis’ should have consequences that are also detectable (which have been).

    • Add in the modelling studies which indicate that current conditions can’t be explained without including greenhouse gases and you have a pretty solid case that what is happening is in large part anthropogenic.”

Quoted, with enhancements, from realclimate.org. The realclimate.org site is very useful, and well worth visiting.


looking at the evidence

“Natural and anthropogenic substances and processes that alter the Earth's energy budget are drivers of climate change.
Radiative forcing (RF) quantifies the change in energy fluxes caused by changes in these drivers for 2011 relative to 1750, unless otherwise indicated.
Positive RF leads to surface warming, negative RF leads to surface cooling.” [Quoted from IPCC Fifth Assessment Report 2013, p.8]

radiativz forcing factors 2013
From Working Group I Contribution to the IPCC Fifth Assessment Report Climate Change 2013:
The Physical Science Basis Summary for Policymakers [.pdf]

  • Greenhouses gases are by far the most important factor in global warming. This is also the factor for which we have, by far, the highest understanding. See LOSU [Level Of Scientific Understanding] column in diagram above.

  • The second most important is ozone (O3). It is also the second-best understood factor.

  • Next is a group of ‘aerosols’. As a group, these are well understood to have a cooling effect. The cooling effects of each, as components, is not well understood but there is strong empiric evidence of the group effect. See also raising more questions than it answers - on brown clouds over asia.

  • That leaves a couple of factors whose effects are not well understood, but those effects are thought to be minor. These are aviation-induced and solar effects.

present road transport highest climate forcer, industry lowest - allegedly

“The new analysis shows that emissions from the power, biomass burning, and industrial sectors of the economy promote aerosol-cloud interactions that exert a powerful cooling effect, while on-road transportation and household biofuels exacerbate cloud-related warming.”

But this is expected to change:

“The differences are because the impacts of greenhouse gases accumulate and intensify over time, and because they persist in the atmosphere for such long periods," said Unger. "In contrast, aerosols rain out after a few days and can only have a short-term impact." ”

See chart:

Road transport radiative forcing; Image: physorg.com

Associated notes:

  • Sun energy increases by approximately 5% every billion years.
  • Pre-industrial carbon levels historically were on the very low side.
  • Carbon is absorbed by lowering of ocean temperatures.
  • Carbon was absorbed and buried during the carboniferous era, forming fossil fuels.
  • Fairly small changes in energy balance can push the climate towards ice ages, or towards warming.
  • Tectonic movements can move land masses to the poles, which in turn can increase cooling/ice formation build-up and changing oceanic currents. The land balances are presently toward the poles.
  • Upthrust land (by tectonic action) also allows ice formation.
  • Less land is exposed during warming periods as water levels rise.
  • Milankovich cycles and tectonic movement are regarded as long-term climate drivers. Short-term drivers include dust, as in the ‘year with no summer’ and positive feedback effecting albedo.
  • There are also large releases of methane from permafrost peat areas and from clathrates. As it decomposes, methane is a major contributor to increasing carbon dioxide in the atmosphere.

It remains that we do not know well how all these effects will pan out in the long-term regarding cloud cover and so on. However, we do still know the planet is warming, and we do still believe the main effect is identified.

Nobody sane denies that there are uncertainties, there are uncertainties in virtually all human endeavours. However, of the elements listed, the view is that GHGs have the greatest effect.

click to return to the index

pressing reasons for action

There are other pressing reasons for controlling fossil fuel filth. There are pressing reasons for reducing dependence. The probability/consensus is that the greenhouse gases are highly relevant.

And we have a batch of better alternatives. Why not just get on with improving the situation? Unless, of course, you are involved in the filthy fossil fuel industry.

The arguments for greenhouse gases are far from ‘weak’. They are the most understood effects by a long march.

Perhaps doubters are confusing the level of knowledge of GHG warming contributed to heavily by human activities, with the smaller uncertainties elsewhere.

ice and sediment coresIce core. Image credit: newscientist.com

Increasing quantities of ice-core samples are being obtained. The diagram to the right shows a composite.

The first ice cores were extracted in 1956 to 1957, with techniques that have been steadily advancing since then. Early cores only went back less than 100,000 years, which is less than one glaciation cycle. Ice cores now go back 10 to 20 times further, back to 750,000 years (Vostok). However, their latest cores have not been fully analysed back to the beginning.

Ice core samples provide historic data of the earth’s temperature and its atmospheric composition. There are also (interrupted) sediment core samples that go back as far as 200 million years. Earlier cores were about 3-400 metres long, and the latest are over three kms long. For more on dating.

The atmospheric load for both carbon and methane is now much higher than has been seen during the last 650,000 years, as determined through examining ice cores.

A major part of the analysis of ice cores is checking the 16O/18O ratio. This gives an estimate of how much water is tied up in ice at any time.

“As ocean water evaporates, preferentially more 16O is released, but in non-glacial times is returned almost immediately to the ocean as runoff from the land. In glacial times this excess 16O is stored in ice masses, leading to enrichment of 18O in the oceans.”[1]

According to the analyses, twenty thousand years ago, the sea-level is estimated as being 120 metres below the present sea-level. Today, the equivalent of another 80 metres is still being held in ice sheets, most of that being in the Antarctic.

 

other considerations

There is constant talk of a medieval cooling period and suggestions that this does not fit the overall data. Evidence has now been found - by looking at marine fossils in sediment cores - that that cooling was probably only local to Northern Europe and may be related to a weakening of the Atlantic Conveyor. It could even be argued that the growth of the industrial revolution has offset cooling.

marker at abelard.org

There was also, probably, some cooling in the three decades from 1950 to 1980. General acceptance is this was a cooling affect from dust/aerosols halted by multiple clean air acts in the West, when faced with deteriorating air quality (smogs).

marker at abelard.org

I have seen recent claims from probably unreliable sources that ice core analysis shows a lag of several hundred years between the warming or cooling, and the changes of carbon dioxide trapped in the ice. For the moment, I believe that this is an error in understanding among those making the claim. The general view, in the more academic sources, appears to be that the carbon dioxide and temperatures track each other very closely, so closely that no such distinction can yet be made.

However, ice is laid down and slowly compacts as, year by year, more snow is precipitated on the top of the ice sheet (or glacier). There are minute spaces between snowflakes and within the firn, prior to the mass being so compressed that air communication with the outside world ceases. This process can take several hundred to a thousand years. Thus the air (including the CO2) analysed in the ice can be several hundred years younger than the ice in which it is entrapped. My guess is that those making a claim concerning time lags are, in fact, confused by this anomaly.

marker at abelard.org

This excellent slide presentation [71-page .pdf file - 3.9 Mb] provides more detail on the general discussion than does this current briefing document, which focuses more on particular aspects. The .pdf document comes from one of the world’s premier weather research units.

marker at abelard.org

Warming and sea-level rises are projected to continue increasing for at least another century, due to present levels of anthropogenic greenhouse gases [AGHGs]. Warming is not expected to the same level all around the planet. While average temperatures are rising and expected to rise further, there may still be highly variant local temperatures that are not directly related to AGHGs.

“However, for various reasons, the exact timing and abruptness of the changes are difficult to ascertain in these records, and records of older abrupt changes are even less secure.”
[Quoted from pnas.org]

Keep this constantly in mind when you hear confident assertions and sound bites.J

Do you expect to find loss of ice?

“We actually know from people who have measured our stakes that we have already lost two to three meters of ice from the surface since 2000.

“To me, it's very telling that nothing is accumulating in today's world. If you look at the tropical region in general -- from the Andes to the Himalayas -- many of those glaciers will disappear within 50 years if current rates of mass loss continue. Unfortunately, people in surrounding villages depend on these ice fields for water resources.

“What do you plan to do, ultimately, with the data you've collected?

“My dream is ultimately to piece together a global map of past climate patterns. Right now we have piecemeal evidence reflecting different regional patterns -- we know that some areas are the warmest they've been in 40,000 years, while some are the warmest they've been in 6,000 years. I think it's safe to say that worldwide, the warming trends of today are more dramatic than they have been in at least 5,000 years -- but we must have a more comprehensive map to see how all these trends fit together.”
[Quoted from grist.org]

Here is a none-too-clear description of temperature measurement in ice-cores.
It is, however, recommended reading.

“Methane is of particular interest in studying abrupt changes. It was primarily "swamp gas" in preindustrial times and thus gives an indication of global wetland area (22). Methane destruction occurs globally, but sources may be localized. The residence time in the atmosphere is short enough that when methane sources are predominantly in the Northern Hemisphere, Greenland ice shows significantly higher methane concentrations than similar-age samples from the Antarctic; hence, changes in the concentration difference between Greenland and Antarctica record changes in the latitudinal distribution of methane sources.”

“The Greenland records show that climate changes have been very large, rapid, and widespread. Coolings were achieved in a series of steep ramps or steps and warmings in single steps. The more dramatic of the warmings have involved 8C warming (8, 25) and 2 increases in snow accumulation (9), several-fold or larger drops in wind-blown materials (17), and 50% increase in methane, indicating large changes in global wetland area (5, 24).

“For the best-characterized warming, the end of the Younger Dryas cold interval 11,500 years ago, the transition in many ice-core variables was achieved in three steps, each spanning 5 years and in total covering 40 years (26). However, most of the change occurred in the middle of these steps. The warming as recorded in gas isotopes occurred in decades or less (8). The most direct interpretation of the accumulation-rate record is that snowfall doubled over 3 years and nearly doubled in 1 year (9). Several records show enhanced variability near this.”
[Quoted from pnas.org]

Note: methane is adjudged to remain in the atmosphere for much less time than CO2, that is approximately 14 years against an ‘indeterminate’ time.

“[...] The more dramatic of the warmings have involved 8C warming and 2X increases in snow accumulation, several-fold or larger drops in windblown materials , and 50% increase in methane, indicating large changes in global wetland area. Between 80,000 and 20,000 yr BP, some 20 interstadial events are recorded. These so-called Dansgaard-Oeschger events lasted for about 500-2000 years and therefore cannot be explained by orbital forcing mechanisms. Instead, they are interpreted to reflect feedback mechanisms involving ice sheet/glacier fluctuations, variations in the ocean system and atmospheric circulation fluctuation." ... "The mechanisms of the [many and complex] relationships are poorly understood (7), and it is not known with any certainty which is the drag force of a climate change, especially when talking about an abrupt climate change as testified by the ice cores.”
[Quoted from www.hi.is - 5 page .pdf]


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