Holocene Cooling Trend


My previous article here was about the NH Summer energy driving the changes in the Earth’s climate.  I used ice core data to show that Greenland and Antarctica both warmed after the NH summer energy started increasing 18,000 years ago.  I have also discussed that ice cores give more of a regional temperature indicator than a local indicator here.

If both of those are correct, then the temperature of the Northern Hemisphere (NH) should be shown to be warmer in the past than it is now.  A recent paper (Sundqvist, Zhang, Moberg 2010) says just this.  It focuses on the two time periods of 6,000 and 1,500 years ago and uses 104 temperature reconstructions from around the Arctic region to determine the temperature at those two times.  It also provides some results for the differences between 6,000 years and 500 years ago.  Due to limitations in the data the overall results are for the 6,000 and 1,500 years ago.

Here are the results for 6,000 and 500 years ago.

The Inconvenient Skeptic

The temperature scale indicates how much warmer each location was 6,000 years ago compared to 500 years ago

The overall conclusion is:

A large majority of the here investigated temperature
reconstructions indicate that temperatures were warmer at
the mid-Holocene (6000 BP ± 500 yrs) compared to the pre-
industrial period (1500 AD ± 500 yrs), both in summer, win-
ter and the annual mean. By taking simple arithmetic aver-
ages over the available data, the reconstructions indicate that
the northern high latitudes were 0.9 ◦ C warmer in summer,
0.5 ◦ C in winter and 1.7 ◦ C warmer in the annual mean tem-
perature at the mid-Holocene (6 ka) compared to the recent
pre-industrial.

This study supports the overall idea that the long-term trend for the NH has been cooling for the past several thousand years.  It does not go into the variability in temperature, but it is a good indicator that cooling has been occurring.  This also supports that the Arctic region and the animals that live there are fully capable of surviving the current temperature.

As I have stated many times before.  The Earth is always changing.  The biggest adjustment that is needed is to our perspective.  We must understand that the Earth does not stay the same.  Ignoring the natural changes of the Earth makes it impossible to understand it.

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Posted in Climate by inconvenientskeptic on November 4th, 2010 at 5:14 am.

6 comments

This post has 6 comments

  1. Glenn Tamblyn Nov 5th 2010

    John

    2 points to make about this study wrt your conclusions on it. The average warming around th Arctic they are reporting is 1.7 DegC relative to Pre Industrial. Current warming up there is around 4-5 DegC warmer than pre industrial so the present warming is more than twice that reported.

    And the study covers 5500 years where as modern warming has happened in more like 50 years. So the current RATE of warming is over 200 times faster than the warming from the Holocene

    And it is the rate of warming (or change in other environmental factors) that is often the most important. Ecosystems and species need time to adapt to changes either by changing their species mix, range or behaviour. If they don’t have the time to adapt then they fail to adapt – which means decline or extinction. Saying that the environment adapted to changes at one rate thousands of years ago does not mean that they can adapt at 200 times that rate today.

    Give Polar Bears a couple of 1000 years to change their range and behaviour and I am sure they will abandon hunting seals and end up standing in northern rivers salmon fishing next to the Grizzlies. But ask them to achieve that in 50 years. Probably they wont.

    Failure to look at rate of change is a common feature of many flawed sceptic arguments. This general type of argument, often put forward by sceptics on a range of subjects along the lines that something has changed this much before so what is the problem, its just ‘natural variation’, is wrong. Because it fails to take account of the rate of change. And also, just because climate was like X in the past doesn’t mean that 9 Billion humans could have survived in that climate. We aren’t concerned with what the past was like. We are interested in whether it was a climate that could support humanity en masse.

    For example, “CO2 has been much higher in the past without ocean acidifiction devestating ocean species so it can’t happen” is a flawed argument because it doesn’t take into account the RATE of CO2 increase. CO2 increase at current rates means that mixing processes in the ocean, which take 100’s and 1000’s of years are not able mix the surface water, which is accumulating CO2 and changing ph, with the rest of the ocean.

    So changes in the surface layer are unprecedented compared to most of past history because of the rate at which they are occurring. If we stop emitting CO2 and wait a few 1000 years then the changes wont look very significant at all. But over the next century or so, oh boy, are they significant.

    And one key impact of ocean acidification changes is on the food supply we can draw from the ocean; an ocean that is already substantially depleted due to over-fishing.

    The key to deconstructing many sceptic claims is not looking at what is said, but at what is not said.

    Glenn

  2. inconvenientskeptic Nov 5th 2010

    Glenn,

    4-5 °C? Where does that come from? I have seen nothing to support that. Not station data or anything. I have looked at raw station data from all over the Arctic and there is nothing to support that.

    Certainly since 1900 there has not been a 4-5 °C increase in temperatures. Maybe a little over 1°C, but not 4-5°C.

    I am also pretty sure that the 6,000 years ago is a composite average. Comparing a decade average to a multi-century average isn’t valid. The average of the past 100 years is about 0.4 °C for the arctic.

    The polar bears will be fine. They survived the transition from glacial to Holocene. Anything now is trivial in comparison.

    http://data.giss.nasa.gov/gistemp/graphs/Fig.B.lrg.gif

  3. Richard111 Nov 6th 2010

    No sign of 4-5 °C Arctic warming here:

    http://ocean.dmi.dk/arctic/meant80n.uk.php

  4. Warming in the Canadian High Arctic is about 3 C, substantially above the global mean, in agreement with GCM predictions, which have Arctic warming well above 7 C by the end of the century under business-as-usual scenarios. More important to the polar bears is the loss of sea ice. See, for example: http://www.usgs.gov/newsroom/article.asp?ID=1773

    Very substantial ecological impacts of warmer winter temperatures, via increased insect predation, are already occurring in Canadian forests. See Bentz et al., (2010) “Climate Change and Bark Beetles of the Western United States and Canada: Direct and Indirect Effects”.

  5. inconvenientskeptic Nov 8th 2010

    Dan,

    According to the UAH 2010 will be the hottest year in the Arctic. It will be under 2 °C anomaly. Most of that took place earlier in the year when El Nino was strong. The warmest 5 year average is barely 1 °C.

    Projections are just that. They are predictions for the future. As for Polar Bears. In my article about NH summer energy I cite an article that showed the early Holocene was likely ice free during the summer at times. It was Jakobsson, 2010. Polar bears survived that just fine.

    All of this has happened before. All of this will happen again. The Earth is always changing. The trick is to understand why it does. CO2 doesn’t cut it.

  6. A. Semczyszak Nov 10th 2010

    “…6,000 years ago …”

    “Evidence of 6 000-Year Periodicity in Reconstructed Sunspot Numbers”, M. A. Xapsos and A. Burke, 2009, Solar Physics, Volume 257, Number 2, 363-369:
    “We have examined these data using Hurst analysis, a moving average filter, and Fourier analysis. All of the procedures indicate the presence of a long term (≈6 000 year) cycle not previously reported.”

    “We do not know whether the Arctic Ocean was completely devoid of ice, but the areas north of Greenland, it was more open water than today … ” – says geologist and researcher Astrid Lysa …” (NGU, 2008).

    “Late Pleistocene-Holocene Marine Geology of Nares Strait Region“, Mudie et al., 2004.:
    “Palaeoceanographic reconstructions from dinocyst assemblages show that from ~6.5 to 3.3 ka BP, there were large oscillations in summer sea surface temperature (SST) from 3 °C cooler than now to 6 °C warmer, and that variations in SIC ranged from two months more to four months less of heavy ice compared to now.”

    “So the current RATE of warming is over 200 times faster than the warming from the Holocene”

    Hundreds of scientific studies say otherwise.
    To imagine the old rate of temperature change (in comparison to current) quote a phrase from Richard Seager’s presentation to the New York Academy of Sciences – The Gulf Stream, European climate and Abrupt Change: “These abrupt changes – the Dansgaard-Oeschger events of the last ice age and the Younger Dryas cold reversal of the last deglaciation – are well recorded in the Greenland ice core and Europe and involved changes in winter temperature of as much as thirty degrees C!”

    “Sudden climate transitions during the Quaternary” by Jonathan Adams, Mark Maslin & Ellen Thomas:
    “All the evidence indicates that most long-term climate change occurs in sudden jumps rather than incremental changes.”
    “Smaller [the event at 8200 ka], but also sudden and widespread, changes to drier or moister conditions have also been noted for many parts of the world for the second half of the Holocene, since about 5,000 years ago (e.g., Dorale et al., 1992).”

    5.9 kiloyear event meant that within a single generation, the Sahara has increased its area by 60 – 75% – from the savannah changed to desert in the period certainly less than one hundred years.

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