Sea Levels 81,000 Years Ago

Climate scientists have used sea levels past and present to help predict those of the future. Temperature affects land ice; increased land ice will lower sea levels while the melting of this ice will raise these levels. Thus increased sea levels (secondary to ice melting) reflect a warmer global temperature. The scientific debate about what is actually happening to our climate has become super heated by politics, much of the warmth coming from scientists themselves.

To know the direction towards which the earth’s temperature is headed we have to know what it was in the past. Let’s pick 81,000 years ago. I picked this time for reasons that will be obvious as we progress. The temperature in the past is fixed and immutable though our ability to read it is always subject to amendment. To say as some do that there’s a consensus about climate change that is not debatable is to have no understanding whatsoever about how science works. Any consensus can be upended by new data or a new insight into existing data. Scientific disputes are not resolvable by a vote, their resolution depends on facts. Scientists are human, worse I can say about no man, thus they frequently get carried away with their beliefs and depart from scientific rigor just like anyone else.

Back to 81,000 years ago. According to commonplace wisdom, the earth should have been cooler then, it was well into the last glacial period, and the sea level supposedly 15 to 20 meters below today’s level. A paper in the February 12, 2010 issue of Science by geoscientists Dorale, et al challenges this view. “A speleothem that has been intermittently submerged in a cave on the island of Mallorca was dated to show that, historically, sea level was more than a meter above its present height. This data implies that temperatures were as high as or higher than now, even though the concentration of CO2 in the atmosphere was much lower.” Quotation from Science page 757.

An accompanying perspective piece by geologist R Lawrence Edwards from the University of Minnesota shows that estimating what the climate was 81,000 years ago is not a simple issue. “Dorale et al. provide evidence for high sea level at ~81,000 years ago, in the middle of the most recent 100,000-year cycle. This result challenges the observational basis for much of the discussion over recent decades… Dorale et al. dated layers of the mineral calcite, which were deposited like bathtub rings from pools of water in Mallorca caves, in the western Mediterranean. Because the pools are connected to the sea through underground passages, the layers record sea level at the time they formed. Using this approach, Dorale et al. inferred sea levels similar to modern values ~81,000 years ago. They estimated maximum rates of sea level rise of ~2 m per century. This rate is high, but not unprecedented in the geologic record. It exceeds by several times those predicted for the next century… A number of previous studies have estimated sea level ~81,000 years ago. Some of these estimates appear to agree with Dorale et al.’s findings, whereas others appear to disagree… Regardless of the ultimate verdict on sea level ~81,000 years ago, Dorale et al’s findings will stimulate ideas, discussion, and new studies of ice age history and causes.”

Note the conclusion by Edwards that new studies are needed. In assessing the current debate about climate change several questions must be answered as best we can. If the planet is warming is it doing so at historically unprecedented rates? Do we know why the change is occurring? If so, can we do anything about it? If we can, is the result worth the cost? The answers to all these questions are still uncertain.

The lay press and our politicians have failed miserably in informing the public of the facts and uncertainties of climate change. The subject is difficult and not close to being definitively settled.  People who are skeptical of man made global warning have been vilified. They have even been compared to holocaust deniers. Scientific disagreements are not resolved by ad hominem attacks.  Likening global warming skeptics to holocaust deniers is itself so anti-scientific as to be like holocaust denial. The proper response to this subject is to gather more information before changing the entire world’s economy in an effort to save the planet – a task that may prove unnecessary or impossible.

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10 Responses to Sea Levels 81,000 Years Ago

  1. Dan says:

    What the temperatures were in the past is not the issue. Nor is the fact that there are natural fluctuations of climates and natural forcings of those fluctuations. And while there are uncertainties, there is also a lot that we know fairly well about those forcings. And yes, there is a very strong consensus indeed that (1) long-lived greenhouse gases are an anthropogenic forcing, and that (2) the currently shifting climate correlates very well indeed with increasing atmospheric concentrations of CO2 and CH4 and not well at all with natural forcings such as solar irradiance.

    • The temperature in the past is very much an issue. If the rise of sea levels in the past (when greenhouse gasses were not in play) was greater than predicted for the next century then a rise in temperature in the future might have nothing to do with CO2 and methane. The rise in these gasses might be correlated but the correlation fortuitous the one having nothing to do with the other. An association does not prove causality.

      As for a strong consensus – and it’s really not that strong – you can fill volumes with scientific consensuses that proved wrong. Just start with the consensus among physicists at the end of the 19th century that physics was essentially complete.

      • Dan says:

        “If the rise of sea levels in the past (when greenhouse gasses were not in play)…”

        I’m not 100% sure because I can only at the moment read the paper’s abstract (don’t have my university journal subscription right now), but I’m pretty sure the paper in question does not say that LLGHGs weren’t in play. In fact, temp/CO2 reconstructions pretty clearly show that CO2 correlates strongly with climate ups and downs. And that’s on top of the understanding that CO2 is a greenhouse gas at all, which has been fairly clear since the 1890s.

        The consensus is actually borne out by statistical significance measures, and the IPCC-4AR is pretty clear where data only meets p = 0.95 confidence levels and not p = 0.99+.

      • All the climate research on global temperature and greenhouse gasses rests on an association between the two. An association does not prove causality hence the importance of work like that cited above which shows an event when the two were dissociated. The only way to prove that the association is question is causal would be to lower greenhouse gasses while keeping all other variables constant. Which if possible, which it isn’t, would be the most expensive experiment in world history. Thus my point about whether the anticpated benefits are worth the cost. Here we get to the domain of politics and economics where the scientist has no special claim to expertise. Thus far the developed world’s leaders, despite a lot of rhetoric, have been unwilling to degrade their economies to the point where meaningful decreases in greenhouse gasses might occur – a decision that seems prudent to me based on the evidence that is currently available. Should newer data appear that would change the cost benefit calculus then a reassessment should be made.

      • Dan says:

        Actually if you read that link carefully, it clearly talks about reconstructions of sea level rise and fall, not temperatures. It only suggests that higher sea level means higher temperatures. However, the poles were in very different places then, and I don’t think the ice caps would have been propped up on Antarctica then (perhaps parts of the northern landsheets though). Remembering Archimedes, it would make sense that the world could be colder with just as much ice, but higher sea levels. I don’t know for sure that that’s the case, but it makes sense.

        Moreover, in what I linked to above there was a very clearly demonstrated link between deuterium (used as a proxy for local/polar temperatures) and CO2 from ice cores (as well as CH4 & NO2 also from ice cores).

        But I’m not interested in politics or economics. Personally, I leave that up to other people. I’m just here for the science. And what we know from the science is simple: (1) CO2 & CH4 are LLGHGs; (2) We’re releasing them into the atmosphere and their concentrations are increasing; ergo (3) we’re adding a positive radiative forcing into the climates processes. It’s not rocket science you know.

      • If your points 1-3 were all that was at issue we could debate their implications at leisure until their importance was clear, but that’s not what’s happening. You’re right it’s nor rocket science So we should react appropriately not hysterically. What humans are doing to our climate is obviously an important issue that deserves serious study. So study away, but the evidence thus far advanced does not seem to many to be sufficient to drastically reorder the world’s economy which is how it’s being used.

        As far as the poles being different from now, your argument would require that the ice be in the sea rather than on land. Yet all the available data suggest that much of the earth’s land mass was densely covered with ice 81,000 years ago.

        A big point of the Science study is that estimates of sea levels circa 81,000 years ago vary dramatically, irrespective of cause. At least one set of estimates is wrong. The same is almost certainly true of predictions of global climate over the next century. If a consensus is correct it will withstand attack. Usually these attacks result in modification of the consensus and occasionally overthrows it.

  2. Operafilly says:

    “The lay press and our politicians have failed miserably in informing the public of the facts and uncertainties of climate change.”

    And by choice!!! Any excuse for more power and taxes. They don’t care if its true or not. Our state attorney general has the missionary zeal….already sending businesses out of state on the basis of co2 emmissions (as if eliminating them here will eliminate them elsewhere). He (Jerry Brown) had also been governor who gave us the legacy of gridlock (he had stopped freeway construction) and unionizing state workers whose bloated salaries and pensions are much of the source of CA’s tremendous, increasing debt. All the forsight of a snail.

    CO2 is only the excuse. These sort care not for coherent thought, only for what enhances their agenda.

  3. kirk Morgan, M.D. says:

    Every major paper in the world has an astrology section. consensus???

  4. Operafilly says:

    “But I’m not interested in politics or economics. Personally, I leave that up to other people.”

    So Dan,you would sell us all into economic slavery for the sake of you ivory tower isolation??? There are far too many variables to make solid conclusions about whether what warming (or cooling) there is bad, second, condemning CO2 as a problem. If anything, more CO2 could be very beneficial for growing enough food to feed the world’s expanding population. But negative postulates seem to be the only ones to get attention. Because those are the ones politicans can use to scare people. These guys drip with hypocrisy. Not to mention the scientists who tailor their studies to get the most grant money. How a true scientist could expect and want the earth to be static is strange. Change is the way of the earth. We should welcome it as a challenge. Yet it horrifies so many people. For me science is a great adventure in discipline, logic, knowledge and imagination. I hate seeing it perverted.

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