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Solar Cycle Triggers La Nina, El Nino-like Climate Shifts

Credit: National Center for Atmospheric Research

Credit: National Center for Atmospheric Research

Researchers have discovered a link between the 11-year solar cycle and tropical Pacific weather patterns that resemble La Niña and El Niño events.

When it comes to influencing Earth’s climate, the Sun’s variability pales in recent decades compared to greehouse gases — but the new research shows it still plays a distinguishable part.

The total energy reaching Earth from the sun varies by only 0.1 percent across the solar cycle. Scientists have sought for decades to link these ups and downs to natural weather and climate variations and distinguish their subtle effects from the larger pattern of human-caused global warming.

Co-authors Gerald Meehl and Julie Arblaster, both affiliated with the National Center for Atmospheric Research in Boulder, Colorado, analyzed computer models of global climate and more than a century of ocean temperature records. Arblaster is also affiliated with the Australian Bureau of Meteorology.

In the new paper and a previous one with additional colleagues, the researchers have been able to show that, as the sun’s output reaches a peak, the small amount of extra sunshine over several years causes a slight increase in local atmospheric heating, especially across parts of the tropical and subtropical Pacific where Sun-blocking clouds are normally scarce.

That small amount of extra heat leads to more evaporation, producing extra water vapor. In turn, the moisture is carried by trade winds to the normally rainy areas of the western tropical Pacific, fueling heavier rains.

As this climatic loop intensifies, the trade winds strengthen. That keeps the eastern Pacific even cooler and drier than usual, producing La Niña-like conditions.

“We have fleshed out the effects of a new mechanism to understand what happens in the tropical Pacific when there is a maximum of solar activity,” Meehl said. “When the sun’s output peaks, it has far-ranging and often subtle impacts on tropical precipitation and on weather systems around much of the world.”

The result of this chain of events is similar to a La Niña event, although the cooling of about 1-2 degrees Fahrenheit is focused further east and is only about half as strong as for a typical La Niña.

True La Niña and El Nino events are associated with changes in the temperatures of surface waters of the eastern Pacific Ocean. They can affect weather patterns worldwide.

Although the Pacific pattern in the new paper is produced by the solar maximum, the authors found that its switch to an El Niño-like state is likely triggered by the same kind of processes that normally lead from La Niña to El Niño.

The transition starts when the changes of the strength of the trade winds produce slow-moving off-equatorial pulses known as Rossby waves in the upper ocean, which take about a year to travel back west across the Pacific.

The energy then reflects from the western boundary of the tropical Pacific and ricochets eastward along the equator, deepening the upper layer of water and warming the ocean surface.

As a result, the Pacific experiences an El Niño-like event about two years after solar maximum — also about half as strong as a true El Niño. The event settles down after about a year, and the system returns to a neutral state.

“El Niño and La Niña seem to have their own separate mechanisms,” Meehl said, “but the solar maximum can come along and tilt the probabilities toward a weak La Niña. If the system was heading toward a La Niña anyway,” he adds, “it would presumably be a larger one.”

The study authors say the new research may pave the way toward predictions of temperature and precipitation patterns at certain times during the approximately 11-year solar cycle.

In an email, Meehl noted that previous work by his team and other research groups has shown that “most of the warming trend in the first half of the 20th Century was due to an increasing trend of solar output, while most of the warming trend in the last half of the 20th Century and ever since has been due to ever-increasing GHG (greenhouse gas) concentrations in the atmosphere from the burning of fossil fuels.”

The new paper appears this month in the Journal of Climate, a publication of the American Meteorological Society. (Sorry, it’s not yet available online.)

Source: Eurekalert

Comments on this entry are closed.

  • Torbjorn Larsson OM July 18, 2009, 7:00 AM

    Ah, interesting! I dearly hope the accumulated work is correct, as it makes sense (shared mechanisms), tells us somewhat about climate stability, implies that climate science is alive and well (as it can go on and discern differences in forcing beyond the AGW change), but foremost elucidates on the major climate gap of science denialists. We have enough problems to contend with as it is, so any result that takes a whack at them is especially welcome.

  • Sili July 18, 2009, 11:20 AM

    Very disturbing if indeed such small variations in solar output can trigger weather phenomena at that scale. Scary.

  • neoguru July 18, 2009, 1:48 PM

    The sun is entirely responsible for heating the earth. Yet you question the suns 0.1% variability to influence climate and totally embrace the idea that 0.03% atmospheric carbon dioxide plays a critical part when it changes 0.006% over a century. Is anybody out there giving this any real thought?

  • Torbjorn Larsson OM July 18, 2009, 3:27 PM

    @ neoguru:

    I’m not sure what you mean by “thought” or which ass you pulled your erroneous numbers from. But the science is clear and has been clear since 2006 or so when the balance tipped over to mostly “tested beyond reasonable doubt”. [IPCC review.]

    The carbon dioxide change is huge at 70 % change relative to preindustrial levels. (Now ~390 ppm compared to ~ 280 ppm at interstitials. And it is now known to be the largest level and most rapid change in the last 2 My, by isotope measurements.)

    While it is a small part of the greenhouse effect and even less of Earth temperature, its change has been unequivocally found to be responsible for the forcing of the climate at this time.

    Also, La Niña and El Niño events are short time weather phenomena which are averaged out in climate models, as are the sun cycle mechanism with its 0.1 % variation. So by definition these things aren’t influencing or part of climate as you suggest.

  • Anaconda July 19, 2009, 8:03 AM

    “tested beyond reasonable doubt”. [IPCC review.]

    Complete bunk.

    An IPCC “lead author” on Global Warming conclusions: “we’re not scientifically there yet.”

    Tom Tripp, a member of the UN IPCC since 2004, is listed as one of 450 IPCC “lead authors” who reviewed reports from 800 contributing writers whose work in turn, was reviewed by more than 2,500 experts worldwide. (Tripp, a metallurgical engineer, is the Director of Technical Services & Development for U.S. Magnesium.) […]
    At Thursday’s [Utah Farm Bureau] convention, Tripp found a receptive audience among the 250 people attending the conference. He said there is so much of a natural variability in weather it makes it difficult to come to a scientifically valid conclusion that global warming is man made. “It well may be, but we’re not scientifically there yet.”

    Tripp also criticized modeling schemes to evaluate global warming, but stopped short of commenting on climate modeling used by the IPCC, saying “I don’t have the expertise.”

    http://www.sltrib.com/business/ci_12854537

    Fact: The Earth has cooled since 1998, first it leveled off, and now in the last couple of years it has cooled.

    Get to know it.

  • gwhitton July 19, 2009, 12:21 PM

    Anaconda,

    Lets not assert facts, when your facts are based purely on an opinion that hasn’t studied all the facts.

    Here is a scientific response to your assertion that global warming stopped in 1998

    http://www.aussmc.org/documents/waiting-for-global-cooling.pdf

    Here’s the crux of the scientists comments.

    There is very little justification for asserting that global warming has gone away over the past
    ten years, not least because the linear trend in globally-averaged annual mean temperatures
    (the standard yardstick) over the period 1998-2007 remains upward. While 1998 was the
    world’s warmest year in the surface-based instrumental record up to that point in time, 2005
    was equally warm and in some data sets surpassed 1998. A substantial contribution to the
    record warmth of 1998 came from the very strong El Niño of 1997/98 and, when the annual
    data are adjusted for this short-term effect (to take out El Niño’s warming influence), the
    warming trend is even more obvious.
    Because of the year-to-year variations in globally-averaged annual mean temperatures, about
    ten years are required for an underlying trend to emerge from the “noise” of those year-toyear
    fluctuations. Hence, the fact that 2006 and 2007 were cooler than 2005, is nowhere near
    enough data to clearly establish a cooling trend.
    Global warming stopped in 1998. Global temperatures have remained static since
    then, in spite of increasing concentrations of greenhouse gasses in the
    atmosphere. Global temperatures have cooled since 1998. Because 2006 and
    2007 were cooler than 2005, a global cooling trend has established itself.
    All these statements, and variations on them, have been confidently asserted in the
    international and Australian media in the past year or so, but the data do not support them.

  • gwhitton July 19, 2009, 12:23 PM

    That blockquote didn’t quite come out the way I planned…but you get the point.

  • DrFlimmer July 19, 2009, 1:51 PM

    Global warming man made or not:

    We have only one chance! And we should not risk it!

  • Anaconda July 19, 2009, 7:10 PM

    From the pdf file linked: “In the
    longer term, it would not be at all surprising, in the lead up to the next strong El Niño and its aftermath, to see global temperatures approach and then exceed the records set in the past ten years.”

    We’ll see…

  • Torbjorn Larsson OM July 20, 2009, 2:12 PM

    Better late reply than never:

    “Complete bunk.”

    Nope, read the IPCC 2007 definitions for uncertainty and compare with the report data. Most of the hypotheses from the models are satisfiable tested or nearly so. Sure there is room for improvements, as always. But the climatology community is clear on the results.

    “The Earth has cooled since 1998″

    I already explained the difference between shortterm weather and longterm climate. Yet you repeat the stupidity.

  • Sili July 20, 2009, 6:13 PM

    The sun is entirely responsible for heating the earth. Yet you question the suns 0.1% variability to influence climate and totally embrace the idea that 0.03% atmospheric carbon dioxide plays a critical part when it changes 0.006% over a century. Is anybody out there giving this any real thought?
    neoguru Says:
    July 18th, 2009 at 1:48 pm

    Apart from the fact that you .006% is wrong that’s still an increase of 20% – pretty significant, I should say. And, duh!, .03% CO2 is pretty damn significant. It basic A-level application of black-body radiation formulae that the equilibrium temperature for Earth is around -20 degrees (someone please correct me, I can’t recall the exact number). UNLESS one takes into account the greenhouse effect from those measly .03%.

    <epithet goes here>

  • Anaconda July 21, 2009, 8:45 AM

    “Nope, read the IPCC 2007 definitions for uncertainty and compare with the report data. Most of the hypotheses from the models are satisfiable tested or nearly so.”

    Two issues:

    The IPCC is calling for drastic governmental action, so it’s no surprise they confirm the accuracy of the models they use to arrive at their conclusions.

    This is called, ‘confirmational bias’.

    There are many reputable scientists that disagree with that conclusion.

    And the “models” have not been tested.

    You can’t test the “future”, only reaching the “future” and then comparing the actual temperatures with what the “model” in the past predicted can confirm or falsify the “model”, and even then with a phenomenon as complex as climate, even an apparent agreement with the predicted temperatures does not mean the model was “correct”.

    There can be other physical factors that weren’t even considered, or not given proper weight in the “model” that caused the temperature pattern recorded.

    “.03% CO2 is pretty damn significant.”

    350 parts per MILLION?

    Science really doesn’t know if CO2 has a “greenhouse” absorption quality or not.

    Classical chemical studies were never able to determine if such is actually the case.

    The CO2 increase equals temperature increase hypothesis came out of a qualitative comparison of Earth and its supposed “twin” Venus which is hot and has a high concentration of CO2 in its atmosphere.

    This “twin” idea is now widely discredited.

  • DrFlimmer July 21, 2009, 12:27 PM

    Anaconda, just one simple quastion:

    Shall we risk it?

  • Jon Hanford July 21, 2009, 1:42 PM

    With 6+ billion people now and more on the way, Dr. Flimmer nails it. Do you really want to risk it ?

  • Anaconda July 21, 2009, 7:03 PM

    The cure could be worse than the disease, particularly if there is no disease to start with.

    This whole movement started off with a small cadre of people obsessed with the alleged rapaciousness of Man.

    Their attitude was that Man is a “blight” on the Earth’s environoment.

    Interestingly, many, if not most (of the original ones) were there for the “global cooling” scare of the 1970’s promoting that little gem.

    As soon as that became untenable, they switched to “global warming” promotion.

    Jim Hansen of NASA fame studied Venus for his Ph. D.and promoted the Venus “twin” idea based on hardly any science at all.

    (So much for the objective scientific standard for astronomers.)

    Look, if there was some hard, rigorous and yes quantified (we are on Earth where classical chemistry can be tested) chemical & physical science for CO2 being an absorbtion agent (greeen house gas), then I would be more persuaded.

    Models of such a complex system as climate are inherently problematic.

    I’m not in favor of giving government and, therefore, elites and special interest groups (insider manipulation) that much power to tax — which is the power to destroy — over individuals.

    This is recipe for political disaster.

    As the “lead author” (there are apparently lots of lead authors) said: “we’re not scientifically there yet.”

    At this point, all I see is a government power grab for controlling economies and increasing their power through higher taxes and down the road some weird kind of move to “world government”.

    I’m opposed to that kind of enslavement.

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