Natural climate processes overshadow recent human-induced Walker circulation trends

Posted: April 2, 2019 by oldbrew in Analysis, atmosphere, climate, modelling, Natural Variation, wind
Tags: , ,

Credit: PAR @ Wikipedia


If you think you saw something about this a few days ago, you’re right. This article is a sort of follow-up that has appeared in Nature Climate Change on 1st April [sic] – abstract here. The ‘recent human-induced Walker circulation trends’ in the headline seem to be an artefact of some of the climate models, judging by the report. The authors make a telling point: ‘In contrast to the observed strengthening, the majority of climate computer models simulate a gradual weakening of the Walker Circulation when forced by increasing greenhouse gas concentrations’. So they got it exactly backwards? How unfortunate.

A new study, published this week in the journal Nature Climate Change, shows that the recent intensification of the equatorial Pacific wind system, known as Walker Circulation, is unrelated to human influences and can be explained by natural processes, reports Phys.org.

This result ends a longstanding debate on the drivers of an unprecedented atmospheric trend, which contributed to a three-fold acceleration of sea level rise in the western tropical Pacific, as well as to the global warming hiatus.

Driven by the east-west sea surface temperature difference across the equatorial Pacific, the Walker circulation is one of the key features of global atmospheric circulation. It is characterized by ascending motion over the Western Pacific and descending motion in the eastern equatorial Pacific.

At the surface, trade winds blow from east to west, causing upwelling of cold water along the equator. From the early 1990s to about 2013, this circulation has intensified dramatically, cooling the eastern equatorial Pacific and triggering shifts in global winds and rainfall (see Figure 1).

These conditions further contributed to drying in California, exacerbating mega-drought conditions and impacting agriculture, water resources and wildfires. Given these widespread impacts on ecosystems and society, the recent Walker circulation trends have become a subject of intense research.

In contrast to the observed strengthening, the majority of climate computer models simulate a gradual weakening of the Walker Circulation when forced by increasing greenhouse gas concentrations (see Figure 1).

“The discrepancy between climate model projections and observed trends has led to speculations about the fidelity of the current generation of climate models and their representation of tropical climate processes,” said Eui-Seok Chung, researcher from the Center for Climate Physics, Institute for Basic Science, South Korea, and lead author of the study.

To determine whether the observed changes in the tropical atmospheric circulation are due to natural climate processes or caused by human-induced climate change, scientists from South Korea, the United States and Germany came together to conduct one of the most comprehensive big-data analyses of recent atmospheric trends to date.

“Using satellite data, improved surface observations and a large ensemble of climate model simulations, our results demonstrate that natural variability, rather than anthropogenic effects, were responsible for the recent strengthening of the Walker circulation,” said Prof. Axel Timmermann, Director of the IBS Center for Climate Physics at Pusan National University and co-author of this study.

Full report here.

Comments
  1. BoyfromTottenham says:

    “The discrepancy between climate model projections and observed trends has led to speculations about the fidelity of the current generation of climate models and their representation of tropical climate processes,”

    “Using satellite data, improved surface observations and a large ensemble of climate model simulations, our results demonstrate that natural variability, rather than anthropogenic effects, were responsible for the recent strengthening of the Walker circulation,”

    Err, so did they use computer models to show that … computer models…to get this result?

  2. ivan says:

    natural climate processes or caused by human-induced climate change

    Err, what are these ‘human-inducements’ they are talking about?

    Is it the hot air rising from all the ‘climate scientists’ running around in panic because they are afraid the gravy train might hit the buffers?

  3. Does anyone know the effects of undersea heat vents and the volcanic activity along the ring of fire? I haven’t found anything but surely they are significant?

  4. oldbrew says:

    The discrepancy between climate model projections and observed trends
    This gives the lie to the ‘settled science’ myth.

    Claims of human-induced climate change have no substance to date, being based on models that clearly can and do contradict and/or fail to match observations.

  5. ren says:

    El Niño is weakening.

  6. oldbrew says:

    BY PIERRE GOSSELIN ON APRIL 3, 2019.
    Another New Study Shows Early 21st-Century Global Warming Hiatus Was Real

    The new study states that many published analyses show that lightning activity is responsive to temperature on time scales ranging from the diurnal to the decadal and that the hiatus in global warming earlier this century can be seen in several global datasets.

    Scientists found that the statistically flat behavior of the global lightning record from the NASA Lightning Imaging Sensor over the same decadal period is consistent with this hiatus in global warming.

    https://climatechangedispatch.com/new-study-global-warming-hiatus-real/

  7. oldbrew says:

    ren – BOM says (2 April):

    The ENSO Outlook remains at El Niño ALERT. This means the chance of El Niño forming from autumn is around 70%; triple the normal likelihood. The surface of the tropical Pacific Ocean has warmed since late January 2019 and has been touching on El Niño thresholds for five consecutive weeks.

    http://www.bom.gov.au/climate/enso/outlook/
    Next issue 16 April 2019
    – – –
    NOAA says: Madden-Julian Oscillation: Recent Evolution, Current Status and Predictions

    The MJO, which was consistently active throughout the fall and winter, became inactive during mid-March

    https://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjoupdate.pdf

  8. oldbrew says:

    Thanks Ren.

    The BoM video for April-June still says 70% chance of El Niño developing, ‘3x normal risk’ (graphic at 2m.20s.)

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