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The Hockey Stick Lives: New Study Confirms Unprecedented Recent Warming Reverses 2,000 Years Of Cooling

By Joe Romm  

"The Hockey Stick Lives: New Study Confirms Unprecedented Recent Warming Reverses 2,000 Years Of Cooling"


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Last month, we reported on the umpteenth study that confirmed the Hockey Stick. It made clear the rate of global warming since 1900 is 50 times greater than the rate of cooling in the previous 5000 years.

That study, Marcott et al, is the most the most comprehensive “Reconstruction of Regional and Global Temperature for the Past 11,300 Years” ever done. It’s the source of most of the data (in blue) in the jaw-dropping graph at the right (click to enlarge). Projected warming this century (in red) on humanity’s current emissions path comes from the recent literature.

Now a team of 78 researchers (from 60 institutions) in the international network PAGES (PAst Global Changes) has “published the most comprehensive reconstruction of past temperature changes at the continental scale” over the past 2000 years. Their Nature Geoscience article (subs. req’d) concludes:

The most coherent feature in nearly all of the regional temperature reconstructions is a long-term cooling trend, which ended late in the nineteenth century. At multi-decadal to centennial scales, temperature variability shows distinctly different regional patterns, with more similarity within each hemisphere than between them. There were no globally synchronous multi-decadal warm or cold intervals that define a worldwide Medieval Warm Period or Little Ice Age, but all reconstructions show generally cold conditions between AD 1580 and 1880, punctuated in some regions by warm decades during the eighteenth century. The transition to these colder conditions occurred earlier in the Arctic, Europe and Asia than in North America or the Southern Hemisphere regions. Recent warming reversed the long-term cooling; during the period AD 1971–2000, the area-weighted average reconstructed temperature was higher than any other time in nearly 1,400 years.

No “worldwide Medieval Warm Period or Little Ice Age.” Another denier myth bites the dust.

Here is a key figure from the new study:

Standardized 30-year-mean temperatures averaged across all seven continental-scale regions. Blue symbols are area-weighted averages, and bars show 25th and 75th unweighted percentiles to illustrate the variability among regions; open black boxes are medians. The red line is the 30-year-average annual global temperature from the HadCRUT4 instrumental time series relative to 1961–1990, and scaled visually to match the standardized values over the instrumental period.

As you can see, the 30-year mean temperature is already at the highest level in almost 1400 years, and this is just the 1971-2000 average. The 1982-2010 average is higher yet again on this scale.

And so we have the hockey stick, which countless studies have now vindicated — though as the top chart makes clear, within a few decades the hockey stick will soon look more (and feel more) like a brick wall.

You can find everything you could want to know about the new study, “Continental-scale temperature variability during the last two millennia,” at the PAGES website. Here are the “primary conclusions” from the FAQ:

(1) The most coherent feature in nearly all of the regional temperature reconstructions is a long-term cooling trend, which ended late in the 19th century.

- The regional rate of cooling varied between about 0.1 and 0.3°C per 1000 years.

- A preliminary analysis using a climate model indicates that the overall cooling was caused by a combination of decreased solar irradiance and increased volcanic activity, as well as changes in land cover and slow changes in the Earth’s orbit. The simulations show that the relative importance of each factor differs between regions.

(2) Temperatures did not fluctuate uniformly among all regions at multi-decadal to centennial scales. For example, there were no globally synchronous multi-decadal warm or cold intervals that define a worldwide Medieval Warm Period or Little Ice Age.

- The period from around 830 to 1100 CE generally encompassed a sustained warm interval in all four Northern Hemisphere regions. In contrast, in South America and Australasia, a sustained warm period occurred later, from around 1160 to 1370 CE.

- The transition to colder regional climates between 1200 and 1500 CE is evident earlier in the Arctic, Europe and Asia than in North America or the Southern Hemisphere.

- By around 1580 CE all regions except Antarctica entered a protracted, multi-centennial cold period, which prevailed until late in the 19th century.

- Cooler 30-year periods between the years 830 and 1910 CE were particularly pronounced during times of weak solar activity and strong tropical volcanic eruptions. Both phenomena often occurred simultaneously. This demonstrates how temperature changes over large regions are related to changes in climate-forcing mechanisms. Future climate can be expected to respond to such forcings in similar ways.

(3) The 20th century ranked as the warmest or nearly the warmest century in all regions except Antarctica. During the last 30-year period in the reconstructions (1971-2000 CE), the average reconstructed temperature among all of the regions was likely higher than anytime in nearly 1400 years. However, some regions experienced 30-year intervals that were warmer than 1971-2000. In Europe, for example, the average temperature between 21 and 80 CE was warmer than during 1971-2000.

Skeptical Science has a good post on the study here.

Related Post:

  • NOAA (2013): ‘Robust, Unambiguous’ Independent Evidence Confirms The Recent Global Warming Measured By Thermometers.

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10 Responses to The Hockey Stick Lives: New Study Confirms Unprecedented Recent Warming Reverses 2,000 Years Of Cooling

  1. Ed Leaver says:

    Nice succinct article:

    There were no globally synchronous multi-decadal warm or cold intervals that define a worldwide Medieval Warm Period or Little Ice Age…

    As I recall, this possibility was in fact suggested by Mann et al. in their seminal 1998 paper that started this whole hockey puck. And they had some evidence, it just wasn’t conclusive given the uniqueness of the suggestion. Glad to see more confirming results. Michael Mann and his colleagues sure deserve it. Note the emphasis on “global” and “worldwide”. No one has ever suggested the European historical record was in doubt, although the precise temperatures certainly were. It now appears certain the Little Ice Age was triggered by volcanism, as “Estimates of the sun’s variability over time are getting smaller; it’s now thought by some scientists to have varied little more in the last millennium than during a standard 11-year solar cycle.” (approx. 0.25 W/m^2)

  2. Jack Burton says:

    As if this will do anything but spur the Fossil Fuel industry into setting loose it’s Public Relations hired guns to get out their and spread the news that the Hockey Stick is long proven fabrication of liberal scientists looking to impose a carbon tax on the American people. We have reached peak science, peak data, peak models and peak confirmation of warming. None of this will register with the 30% radical right wingers. And it will register very little with the bottom 50% who now struggle daily just to survive in our new globalized economy. This leaves at best 30% of Americans who even care about climate change, of them probably 10% actively care and make any effort at all to influence politicians or alter their daily life to reduce carbon footprints.
    The deniers and the Fossil Fuel industry, in loose alliance with the uninterested are a clear majority.
    I just heard again that new evidence shows the seas are becoming more highly stressed by being the world’s carbon sink, acidification grows. Trust me, when the basic life cycles in the ocean start to shut down, we end up like that old 70′s movie ‘Soylent Green”. Oddly enough, that old movie was bang on the money.

  3. mulp says:

    Forget trying to reason with the conservatives and Republicans and the industries whose business model is pillage and plunder – they do not care about facts or science, but only in ensuring they have no limits to their pillage and plunder.

    “You can’t take it with you”, and they will be dead before they finish the job of pillage and plunder and leave only wasteland. But they will have left more than their mark, more like a huge scar on the face of the earth.

    The constant collection of climate history data serves science which still can’t predict the future with sufficient certainty for me to know how long I need to hang on before a great glacier slides into the seas and raises sea level by 20 cm.

    • Mulga Mumblebrain says:

      It is really strange that the science is so well established, yet the denialist lunatics still screech that the hockey-stick is a ‘fraud’. The fact that there are scores and more hockey-sticks now, seems beyond their comprehension. If they were told that there were so many undoubtedly they would reflexively declare them all fraudulent, such is the unbending fanaticism of the tiny mind, that cannot handle being proved wrong.

  4. Raul M. says:

    Not to be confused,
    Many people’s rejection of climate science is the rejection of any assumption that they have the mental ability to understand the complex interrelationships of natural forcing + anthropogenic forcing. It’s not so much that they are saying that the science is wrong, it’s that saying that that they can understand it enough to take a stand is wrong. Sort so like are they going to enroll in a college course where they would be lost and failing, the result screams of no, no, no is the resulting reply.

    • Raul M. says:

      To ease further confusion,
      Natural forcing accepts anthropogenic forcing into the big picture, and natural forcing will prevail. Hence, no evidence of anthropogenic forcing may exist in 5 million years.
      Could natural forcing be explained through the history of the Earth to show any possibility of higher life form involvement in initiating forcing? Personally, I couldn’t aspire to show any previous higher life form involvements in natural forcing before anthropogenic involvements.

      • Raul M. says:

        Cooking pots could be improved by having a silicone pad imbedded into the side walls and lids of the pots. Such would require less heat to cook as the cooking heat wouldn’t be lost to the surrounds. Less heat loss would mean less cooling needed to keep a comfortable kitchen. It could be especially appreciated in commercial kitchens with the lowered elec. fees.

      • Raul M. says:

        How does the heat produced by burning coal with the associated release of co2 compare with the heat produced if all of the carbon of the coal is in the form af atmospheric carbon? Does the carbon represent the relative same in heating whether all at once by burning + co2 warming or the slower accumulation of heating through the various acculumations of forcings through the variety of ways carbon resides in the atmosphere?
        How does the all at once heating of burning carbon compare with the slow heating of atmospheric carbon?
        Is it just broken down into the release of stored energy and the capacity to accept solar energy without the carbon being changed to some other element in the processes of the changes in the residence times of the carbon in the various forms in various interaction capacities?

  5. fj says:

    The graph clearly demonstrates divergence and that the mechanics of progress is no longer defined; in other words the machine is starting to fail.

    It is only humans that make machines.

  6. Global Green Hu says:

    The hockey stick graph has been confirmed again and again. There’s also plenty of other evidence to show us the Earth is warming. http://clmtr.lt/cb/rBi03m