Wednesday, June 3, 2015

New paper finds eastern equatorial Pacific Ocean was 2C warmer than present 10,000 years ago

A paper published today in Earth and Planetary Science Letters finds the Eastern equatorial Pacific Ocean was ~2°C warmer than the present during the early Holocene from 10,000 to 8,000 years ago.

According to the authors, 

"Temperature higher temperatures in the early Holocene, a cooling of ∼2° by [8,000 years before the present] and after relatively stable temperatures to the present."
and as demonstrated by graphs from the paper below:

Horizontal axis is thousands of years before the present. Graph A shows temperature proxy from Antarctic ice cores, graph B shows 0-150m depth ocean temperature in black

Contrary to popular belief, the global oceans have warmed only 0.09C (9 hundredths of one degree) over the past 55 years (Levitus et al 2012). The entirely natural warming of the Eastern Equatorial Pacific Ocean at the beginning of the Holocene ~10,000 years ago found by this paper is over 22 times greater by way of comparison. The IPCC claims irreversible, catastrophic 'tipping points' will occur from global warming of 1.5 - 2.0C, but hundreds of temperature proxy papers have demonstrated no such tipping points occurred with temperatures 1.5C up to 6C warmer many times in the past. 

Related: New paper finds the 18+ year 'pause' of global warming is not due to missing heat hiding in the deep oceans

Eastern equatorial Pacific ocean heat content is influenced by Southern Ocean dynamics.
Southern Ocean temperature signal reached the equatorial Pacific thermostad via SAMW.
Eastern Equatorial Pacific thermostad sequesters heat from the surface.


Temperature reconstructions from a shallow core (375 m) from the Peru Margin are used to test the influence of Subantarctic Mode Water (SAMW) on the eastern equatorial Pacific (EEP) thermostad and thus the effect of southern high latitude climate on interior ocean heat content (OHC). Temperature estimates, based on Mg/Ca measurements of planktonic and benthic foraminifera (Neogloboquadrina dutertrei and Uvigerina spp ., respectively) show higher temperatures in the early Holocene, a cooling of ∼2° by 8 kyr B.P. and after relatively stable temperatures to the present. The temperature signal is similar in direction and timing to a rather robust Holocene climate signal from the southern high latitudes suggesting it originated there and was advected to the core site in the EEP. Based on the N. dutertrei and Uvigerina Mg/Ca temperature and δ13C records we conclude that SAMW acted as a conduit transporting the southern high latitude climate to the interior of the equatorial Pacific. We propose that the early Holocene warmth is related to a southward migration of the Subtropical Front, which enhanced the influence of warm subtropical water in the region of SAMW formation and was then transported to the EEP thermostad. The early Holocene warmth recorded in the EEP thermostad has a muted sea surface temperature expression indicating this mechanism is important for sequestering heat in the ocean interior.

UPDATE: Coincidentally, another paper was published today showing sea surface temperature (SST) proxies of the Western North Atlantic Ocean and North Atlantic Ocean over the past 14,000 years, both of which demonstrate higher sea surface temperatures than the present during the early and mid-Holocene:

1 comment:

  1. In the southern hemisphere a southward migration of the Subtropical Front is a poleward migration and would have been mirrored in the northern hemisphere.

    This accords with my view that changes in the energy balance of the Earth system are countered by latitudinal climate zone shifting and changes in the zonality / meridionality of the jet stream tracks.

    Such changes happen all the time as a result of variability in sun and oceans and the solar influence is the primary forcing agent which works either via the Milankovitch cycles to move the Earth in and out of ice ages or via the mechanism I described here:

    for shorter climate cycling on time scales of 1000 to 1500 years or less.

    The question I have often asked of AGW proponents (to no avail) is how far they think our CO2 emissions might have shifted the climate zones if one accepts that CO2 has a net warming effect (I am doubtful that it has any but that is another matter).

    My guess would be that the effect would be too small to measure compared to natural variations.

    As for how I think the entire climate system works see here:

    especially steps 1 to 20 in the body of the text.