Global warming preceded by increasing carbon dioxide concentrations during the last deglaciation

Global warming preceded by increasing carbon dioxide concentrations during the last deglaciation

Journal name:
Nature
Volume:
484,
Pages:
49–54
Date published:
(05 April 2012)
DOI:
doi:10.1038/nature10915
Received
16 September 2011
Accepted
01 February 2012
Published online
04 April 2012

Abstract

The covariation of carbon dioxide (CO2) concentration and temperature in Antarctic ice-core records suggests a close link between CO2 and climate during the Pleistocene ice ages. The role and relative importance of CO2 in producing these climate changes remains unclear, however, in part because the ice-core deuterium record reflects local rather than global temperature. Here we construct a record of global surface temperature from 80 proxy records and show that temperature is correlated with and generally lags CO2 during the last (that is, the most recent) deglaciation. Differences between the respective temperature changes of the Northern Hemisphere and Southern Hemisphere parallel variations in the strength of the Atlantic meridional overturning circulation recorded in marine sediments. These observations, together with transient global climate model simulations, support the conclusion that an antiphased hemispheric temperature response to ocean circulation changes superimposed on globally in-phase warming driven by increasing CO2 concentrations is an explanation for much of the temperature change at the end of the most recent ice age.

Figures at a glance

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  1. Figure 1: Proxy temperature records.Proxy temperature records.

    a, Location map. CBT, cyclization ratio of branched tetraethers; MBT, methylation index of branched tetraethers; TEX86, tetraether index of tetraethers consisting of 86 carbon atoms; , alkenone unsaturation index. b, Distribution of the records by latitude (grey histogram) and areal fraction of the planet in 5° steps (blue line).

  2. Figure 2: CO2 concentration and temperature.CO2 concentration and temperature.

    a, The global proxy temperature stack (blue) as deviations from the early Holocene (11.5–6.5 kyr ago) mean, an Antarctic ice-core composite temperature record42 (red), and atmospheric CO2 concentration (refs 12, 13; yellow dots). The Holocene, Younger Dryas (YD), Bølling–Allerød (B–A), Oldest Dryas (OD) and Last Glacial Maximum (LGM) intervals are indicated. Error bars, 1σ (Methods); p.p.m.v., parts per million by volume. b, The phasing of CO2 concentration and temperature for the global (grey), Northern Hemisphere (NH; blue) and Southern Hemisphere (SH; red) proxy stacks based on lag correlations from 20–10 kyr ago in 1,000 Monte Carlo simulations (Methods). The mean and 1σ of the histograms are given. CO2 concentration leads the global temperature stack in 90% of the simulations and lags it in 6%.

  3. Figure 3: Global temperature and climate forcings.Global temperature and climate forcings.

    a, Relative sea level26 (diamonds). b, Northern Hemisphere ice-sheet area (line) derived from summing the extents of the Laurentide43, Cordilleran43 and Scandinavian (R. Gyllencreutz and J. Mangerud, personal communication) ice sheets through time. c, Atmospheric CO2 concentration. d, Global proxy temperature stack. e, Modelled global temperature stacks from the ALL (blue), CO2 (red) and ORB (green) simulations. Dashed lines show global mean temperatures in the simulations, using sea surface temperatures over ocean and surface air temperatures over land. f, Insolation forcing for latitudes 65° N (purple) and 65° S (orange) at the local summer solstice, and global mean annual insolation (dashed black)44. Error bars, 1σ.

  4. Figure 4: Hemispheric temperatures.Hemispheric temperatures.

    a, Atmospheric CO2 concentration. b, Northern Hemisphere (blue) and Southern Hemisphere (red) proxy temperature stacks. c, Modelled Northern Hemisphere (blue) and Southern Hemisphere (red) temperature stacks from the ALL simulation. d, Northern Hemisphere minus Southern Hemisphere proxy temperature stacks (dark purple). North Atlantic minus South Atlantic region proxy temperature stacks (light purple). e, Modelled Northern Hemisphere minus Southern Hemisphere temperature stacks in the ALL (blue), CO2 (red) and ORB (green) simulations. f, Modelled AMOC strength in the ALL (blue), CO2 (red) and ORB (green) simulations. g, North Atlantic sediment core OCE326-GGC5 231Pa/230Th (ref. 24). Temperatures are given as deviations from the early Holocene (11.5–6.5 kyr ago) mean. Error bars, 1σ.

  5. Figure 5: Temperature change before increase in CO2 concentration.Temperature change before increase in CO2 concentration.

    a, Linear temperature trends in the proxy records from 21.5–19 kyr ago (red) and 19–17.5 kyr ago (blue) averaged in 10° latitude bins with 1σ uncertainties. b, Proxy temperature stacks for 30° latitude bands with 1σ uncertainties. The stacks have been normalized by the glacial–interglacial (G–IG) range in each time series to facilitate comparison.

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Comments

  1. 2012-04-06 08:45 AM

    Report this comment #41044

    Arno Arrak said:

    When I read about “… potential physical explanations for the correlations between temperature, CO2 concentration and AMOC variability in three transient simulations of the last deglaciation…” I started wondering about the purpose of all this verbiage. Climate simulations as far as I go have been losers and I certainly can’t check any of this stuff myself. After more unnecessary verbiage about “Uncertainty analysis” and “Robustnes of results” I realized it was meant to ease us into a belief that they have discovered something big: carbon dioxide did not follow but preceded end-Pleistocene warming. I never would have guessed it from their graphs. It is clear that this paper, as all others emanating from the climate establishment, takes it for granted that any observed warming is caused by the enhanced greenhouse effect of carbon dioxide and attempts to prove it. There is just this one problem with this assumption: the chief greenhouse gas on earth is not carbon dioxide but water vapor. They both absorb outgoing infrared (long-wave) radiation and it is their combined absorption of radiant energy that causes the atmosphere to get warm. But now consider this: when we don’t change the amount of carbon dioxide in the air we have a stable climate. There are local temperature and humidity variations, to be sure, but long-term drift is absent. What guarantees this? To prevent a long term temperature drift the IR absorption by greenhouse gas concentration that determines IR transmittance of the atmosphere must respond to any such temperature drift. And water vapor is the only greenhouse gas that can easily do that. Starting from this qualitative picture Ferenc Miskolczi brought in radiation theory and showed that for a stable climate to exist the optical thickness of the atmosphere in the infrared had to have a value of 1.86 (15% transmittance). This transmittance is determined by the combined absorption of infrared radiation by all the greenhouse gases present, but the adjustment is maintained by water vapor, the only adjustable greenhouse gas in the lot. The blogosphere was hostile to the idea because it wiped out the sacrosanct Arrhenius law. But Miskolczi went on to test it using NOAA database of weather balloon observations that goes back to 1948. He found that the IR transmittance of the atmosphere had been constant for the previous 61 years as his theory predicted (E&E 21(4):243-262, 2010). During that same period of time the amount of carbon dioxide in air increased by 21.6 percent. This means that the addition of all this carbon dioxide to air had no effect whatsoever upon the absorption of IR by the atmosphere. And no absorption means no greenhouse effect, case closed. This is an empirical observation, not derived from any theory, and it overrides any theoretical calculations that do not agree with it. Specifically, it overrides any calculations based on climate models that use the greenhouse effect to predict warming. In accord with this, a close examination of the temperature history of the last 100 years reveals that there has been no greenhouse warming at all during this entire period. Starting with the twentieth century, the first part of the twentieth century warming started in 1910 and stopped in 1940. There was no corresponding increase of carbon dioxide at the beginning of this warming which means that according to the laws of physics it cannot be greenhouse warming. Bjorn Lomborg attributes this warming to solar influence and I agree with him. There was no warming in the fifties, sixties, and seventies while carbon dioxide relentlessly increased. There is no satisfactory explanation for this lack of warming, only various contorted excuses to explain it away. The true reason for this lack of warming is clear from Miskolczi’s work. There was no warming in the eighties and nineties either according to the satellite temperature measurements. There was only a short spurt of warming between 1998 and 2002 caused by the warm water that the super El Nino of 1998 had carried across the ocean. And there was no warming from that point on to the present while carbon dioxide just kept on going up on its merry way. And if you still think Arctic warming proves the existence of greenhouse warming think again: Arctic warming is not greenhouse warming either and is caused by Atlantic Ocean currents carrying warm Gulf Stream water into the Arctic (E&E 22(8):1067-1083, 2011). Taking all this history and Miskolczi’s theory into account the attempt of this Nature article to explain the end-Pleistocene warming as greenhouse warming is nothing more than hopelessly misguided global warming doctrine

     

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