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  1. #13041
    owedtojoy owedtojoy is offline
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    Kevin Trenberth interviewed about the unusual weather on US TV.



    And an admission by an administration official:

    “We’ve had record fires in 10 states in the last decade, most of them in the West,” said Agriculture Department Undersecretary Harris Sherman, who oversees the Forest Service. Over the past 10 years, the wildfire season that normally runs from June to September expanded to include May and October. Once, it was rare to see 5 million cumulative acres burn in a year, but some recent seasons have recorded twice that.

    “The climate is changing, and these fires are a very strong indicator of that,” Sherman said
    .
    Agriculture Undersecretary On Wildfires: 'The Climate Is Changing, And These Fires Are A Very Strong Indicator Of That' | ThinkProgress
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  2. #13042
    kront999 kront999 is offline
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    On the Observed Trends and Changes in Global Sea Surface
    Temperature and Air-Sea Heat Fluxes (1984-2006)

    W. G. Large* and S. G. Yeager

    AMS Journals Online - On the Observed Trends and Changes in Global Sea Surface Temperature and Air-Sea Heat Fluxes (1984-2006)


    Abstract

    Global satellite observations show the sea surface temperature (SST) increasing since the 1970s in all ocean basins, while the net air-sea heat flux, Q, decreases. Over the period 1984-2006 the global changes are 0.28°C in SST and -9.1 W/m2 in Q, giving an effective air-sea coupling coefficient of -32 W/m2/°C. The global response in Q expected from SST alone is determined to be -12.9 W/m2, and the global distribution of the associated coupling coefficient is shown.

    Typically, about one-half (6.8 W/m2) of this SST effect on heat flux is compensated by changes in the overlying near surface atmosphere. Slab Ocean Models (SOMs) assume that ocean heating processes do not change from year to year, so that a constant annual heat flux would maintain a linear trend in annual SST. However, the necessary 6.1 W/m2 increase is not found in the downwelling longwave and shortwave fluxes, which combined show a -3 W/m2 decrease.

    The SOM assumptions are revisited to determine the most likely source of the inconsistency with observations. The indirect inference is that diminished ocean cooling due to vertical ocean processes played an important role in sustaining the observed positive trend in global SST from 1984 through 2006, despite the decrease in global surface heat flux.
    A similar situation is found in the individual basins, though magnitudes differ.

    A conclusion is that natural variability, rather than long term climate change, dominates the SST and heat flux changes over this 23 year period. On shorter time scales the relationship between SST and heat flux exhibits a variety of behaviors.

    From the Discussion and Conclusions:

    .

    A strong conclusion is that from 1984 through 2006 the upper ocean did not behave as a slab ocean model, because increasing SST and decreasing heat flux are inconsistent with SOM behavior. The most likely way for this to happen is if the warming strengthened the upper ocean stratification, so that the cooling by vertical ocean processes became less, perhaps with some shallowing of the mixing depth. Indeed, heat flux anomalies would be expected to warm SST faster than subsurface temperatures, increasing the stratification and inhibiting entrainment mixing of cold water to the surface. Although consistent, there are also other factors at work, such asthe wind and freshwater forcing, including sea-ice melt, not considered here. The inference for a dominant role for vertical ocean processes is indirect, because their time evolution is not known. However, it is supported by the data, by their dominant role in ENSO variability, and by arguments that lateral processes must be small globally and seem to be so on basin scales too, and that changes in mixing depth would need to be too large to play an important role on their own.


    .

    The implication is that natural variability dominates the SST and the order 10 W/m2 heat flux signals over 1984-2006 time period, with a significant contribution from the 1995-1996 shift from positive to negative NAO index. Also supportive of this possibility are the different ways SST and the various heat flux anomalies behave on decadal and shorter time scales. Although incomplete, the apparent much more steady behavior of SST and heat flux through the 1950s and 1960s is also consistent.





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  3. #13043
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    Tracking the Atlantic Multidecadal Oscillation through the last 8,000 years : Nature Communications : Nature Publishing Group


    Absract

    Understanding the internal ocean variability and its influence on climate is imperative for society. A key aspect concerns the enigmatic Atlantic Multidecadal Oscillation (AMO), a feature defined by a 60- to 90-year variability in North Atlantic sea-surface temperatures. The nature and origin of the AMO is uncertain, and it remains unknown whether it represents a persistent periodic driver in the climate system, or merely a transient feature. Here, we show that distinct, ~55- to 70-year oscillations characterized the North Atlantic ocean-atmosphere variability over the past 8,000 years. We test and reject the hypothesis that this climate oscillation was directly forced by periodic changes in solar activity. We therefore conjecture that a quasi-persistent ~55- to 70-year AMO, linked to internal ocean-atmosphere variability, existed during large parts of the Holocene. Our analyses further suggest that the coupling from the AMO to regional climate conditions was modulated by orbitally induced shifts in large-scale ocean-atmosphere circulation.


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  4. #13044
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    Quote Originally Posted by kront999 View Post
    On the Observed Trends and Changes in Global Sea Surface
    Temperature and Air-Sea Heat Fluxes (1984-2006)

    W. G. Large* and S. G. Yeager

    AMS Journals Online - On the Observed Trends and Changes in Global Sea Surface Temperature and Air-Sea Heat Fluxes (1984-2006)
    Old research, data from before 2006, and looking at 23 years only. This paper looks at trends over many decades.

    http://www.nature.com/nclimate/journ...imate1553.html


    Recent observed ∆T estimates from Domingues et al. 2008 (blue), Ishii et al. 2009 (red) and Levitus et al. 2009 (green) compared with the 20th Century (20CEN) multimodel response (MMR) of phase 3 of the Coupled Model Intercomparison Project (CMIP3) for the subsets of models including volcanic (VOL, black) and no volcanic (NoV, gray) forcings. MMR results are also shown for the CMIP3 SRES A1B scenarios (dashed black and gray), constructed from the same VOL and NoV subsets defined by the 20CEN models. Figure 1c from Gleckler et al. 2012.
    Last edited by owedtojoy; 3rd July 2012 at 11:08 AM.
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  5. #13045
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    A recommended paper by Neven of the Arctic Ice Blog on Arctic Oceanography:

    24-3 Beszczynska-Möller et al.

    In recent decades, the Arctic Ocean has changed dramatically. Exchanges through the main oceanic gateways indicate two main processes of global climatic importance—poleward oceanic heat flux into the Arctic Ocean and export of freshwater toward the North Atlantic. Since the 1990s, in particular during the International Polar Year (2007–2009), extensive observational efforts were undertaken to monitor volume, heat, and freshwater fluxes between the Arctic Ocean and the subpolar seas on scales from daily to multiyear. This paper reviews present-day estimates of oceanic fluxes and reports on technological advances and existing challenges in measuring exchanges through the main oceanic gateways to the Arctic.
    Not paywalled.
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  6. #13046
    kront999 kront999 is offline
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    A Hemispheric Mechanism for the Atlantic Multidecadal Oscillation
    AMS Journals Online - A Hemispheric Mechanism for the Atlantic Multidecadal Oscillation

    Abstract
    The physical processes associated with the 70-yr period climate mode, known as the Atlantic multidecadal oscillation (AMO), are examined. Based on analyses of observational data, a deterministic mechanism relying on atmosphere–ocean–sea ice interactions is proposed for the AMO. Variations in the thermohaline circulation are reflected as uniform sea surface temperature anomalies in the North Atlantic. These anomalies are associated with a hemispheric wavenumber-1 sea level pressure (SLP) structure in the atmosphere that is amplified through atmosphere–ocean interactions in the North Pacific. The SLP pattern and its associated wind field affect the sea ice export through Fram Strait, the freshwater balance in the northern North Atlantic, and consequently the strength of the large-scale ocean circulation. It generates sea surface temperature anomalies with opposite signs in the North Atlantic and completes a negative feedback. The authors find that the time scale of the cycle is associated with the thermohaline circulation adjustment to freshwater forcing, the SST response to it, the oceanic adjustment in the North Pacific, and the sea ice response to the wind forcing. Finally, it is argued that the Great Salinity Anomaly in the late 1960s and 1970s is part of AMO.

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  7. #13047
    kront999 kront999 is offline
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    Causes(?) of ocean warming | Climate Etc.



    I suspect that the reasoning behind the Gleckler et al. Nature Climate Change article will carry the day in the forthcoming IPCC AR5. However, in light of these other papers, climate models have documented deficiencies in simulating the relevant surface fluxes. Multi-decadal natural internal variability (which is poorly simulated by the climate models) may be the dominant cause of the recent ocean warming (in terms of changes in ocean mixed layer depth and changes in sensible/latent heat fluxes).

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  8. #13048
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    The Impact of AMOC on Arctic Sea-ice Variability

    Salil Mahajan1, Rong Zhang2, Thomas L. Delworth2, Shaoqing Zhang2,
    Anthony J. Rosati2 and You-Soon Chang2

    1Oak Ridge National Laboratory, Oak Ridge, Tennessee

    2Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
    http://curryja.files.wordpress.com/2...moc_arctic.pdf

    Conclusions and Caveats

    ! GFDL CM2.1 unforced simulation shows that AMOC can significantly
    modulate Arctic sea-ice on decadal/multi-decadal scales.

    The spatial pattern of AMOC associated Arctic variability in GFDL CM2.1 is
    similar to the observed trend in the Winter season.

    AMOC seems to have little impact on Pacific sector of the Arctic in GFDL
    CM2.1, where the observed decline is the strongest in the summer.

    AMOC fingerprints suggest that the AMOC has been strengthening in the
    past few decades.

    A strengthening AMOC could have contributed to the observed decline in the
    Arctic Sea-ice in the Winter, but not in the summer based on GFDL CM2.1
    results.

    AR2 model of AMOC fingerprints predicts a decline of the AMOC in the
    coming years, suggesting a weakening of the decrease in Arctic sea-ice.

    The above results are based on GFDL CM2.1 and 50 years of observational
    data.
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  9. #13049
    owedtojoy owedtojoy is offline
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    Quote Originally Posted by kront999 View Post
    Oh, poor old Judy, still plowing a lone furrow. I hear the BEST team (of which she is a member) is about to confirm anthropogenic origins for the current warming. Wonder how she will live with that in front of her purely denialist buddies.

    You might say she's covering her ass on this one.

    Incidentally, the papers assigning a dominant role to global warming are not saying there is no natural variability, and the papers on natural variability are not saying there is no global warming.

    There is clearly both, and no paper disagrees with that. Those type of papers just do not get written any more.

    Given the precipitate drop in sea ice extent after 2006 to levels lower than predicted by models, natural variability as the dominant forcing is looking less and less likely.
    Last edited by owedtojoy; 3rd July 2012 at 03:56 PM.
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  10. #13050
    kront999 kront999 is offline
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    Atmospheric Blocking and Atlantic Multidecadal Ocean Variability

    Abstract
    Atmospheric blocking over the northern North Atlantic, which involves isolation of large regions of air from the westerly circulation for 5 days or more, influences fundamentally the ocean circulation and upper ocean properties by affecting wind patterns. Winters with clusters of more frequent blocking between Greenland and western Europe correspond to a warmer, more saline subpolar ocean. The correspondence between blocked westerly winds and warm ocean holds in recent decadal episodes (especially 1996 to 2010). It also describes much longer time scale Atlantic multidecadal ocean variability (AMV), including the extreme pre–greenhouse-gas northern warming of the 1930s to 1960s. The space-time structure of the wind forcing associated with a blocked regime leads to weaker ocean gyres and weaker heat exchange, both of which contribute to the warm phase of AMV.

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