Solar Cycle Linked to Global Climate—Drives events similar to El Niño, La Niña

[OKIsItJustMe]

http://www.nsf.gov/news/news_summ.jsp?cntn_id=115207&org=OLPA&from=news

Press Release 09-139

Solar Cycle Linked to Global Climate

Drives events similar to El Niño, La Niña

July 16, 2009

Establishing a key link between the solar cycle and global climate, research led by scientists at the National Science Foundation (NSF)-funded National Center for Atmospheric Research (NCAR) in Boulder, Colo., shows that maximum solar activity and its aftermath have impacts on Earth that resemble La Niña and El Niño events in the tropical Pacific Ocean.

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

"These results are striking in that they point to a scientifically feasible series of events that link the 11-year solar cycle with ENSO, the tropical Pacific phenomenon that so strongly influences climate variability around the world," says Jay Fein, program director in NSF's Division of Atmospheric Sciences. "The next step is to confirm or dispute these intriguing model results with observational data analyses and targeted new observations."

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.

Building on previous work, the NCAR researchers used computer models of global climate and more than a century of ocean temperature to answer longstanding questions about the connection between solar activity and global climate.

The research, published this month in a paper in the Journal of Climate, was funded by NSF, NCAR's sponsor, and by the U.S. Department of Energy.

"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," says NCAR scientist Gerald Meehl, the paper's lead author. "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 new paper, along with an earlier one by Meehl and colleagues, shows that as the Sun reaches maximum activity, it heats cloud-free parts of the Pacific Ocean enough to increase evaporation, intensify tropical rainfall and the trade winds, and cool the eastern tropical Pacific.

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.

Over the following year or two, the La Niña-like pattern triggered by the solar maximum tends to evolve into an El Niño-like pattern, as slow-moving currents replace the cool water over the eastern tropical Pacific with warmer-than-usual water.

Again, the ocean response is only about half as strong as with El Niño.

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

The paper does not analyze the weather impacts of the solar-driven events. But Meehl and his co-author, Julie Arblaster of both NCAR and the Australian Bureau of Meteorology, found that the solar-driven La Niña tends to cause relatively warm and dry conditions across parts of western North America.

More research will be needed to determine the additional impacts of these events on weather across the world.

"Building on our understanding of the solar cycle, we may be able to connect its influences with weather probabilities in a way that can feed into longer-term predictions, a decade at a time," Meehl says.

Scientists have known for years that long-term solar variations affect certain weather patterns, including droughts and regional temperatures.

But establishing a physical connection between the decadal solar cycle and global climate patterns has proven elusive.

One reason is that only in recent years have computer models been able to realistically simulate the processes associated with tropical Pacific warming and cooling associated with El Niño and La Niña.

With those models now in hand, scientists can reproduce the last century's solar behavior and see how it affects the Pacific.

To tease out these sometimes subtle connections between the sun and Earth, Meehl and his colleagues analyzed sea surface temperatures from 1890 to 2006. They then used two computer models based at NCAR to simulate the response of the oceans to changes in solar output.

They found 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.

Although this Pacific pattern 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. 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," says Meehl, "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."

-NSF-

Media Contacts
Cheryl Dybas, NSF [phone] [email protected]
Rachael Drummond, NCAR [phone] [email protected]

…

[pscot]

1. The deniers will get on this

like ants at a picnic. It says nothing about anthropogenic warming, but that won't stop them.

[Narkos]

2. What's the point of this post? n/t

[OKIsItJustMe]

3. Hmmm… "What's the point?"

Excellent question! I wonder what "the point" was in doing the research?

I wonder what the point was of the NSF posting it on their home page. http://www.nsf.gov/

[Narkos]

4. I'm just curious what YOUR point was. That's all.

:eyes:

[OKIsItJustMe]

5. Our understanding of the environment and of climate is changing every day

I like to keep track of it. Whether it is something that reinforces conventional wisdom, or something which contradicts orthodox theories, if it's coming from a credible source (like the NSF) then I'm interested in it.

I believe that the "skeptics" who charge that "global warming" is caused purely by an increase in solar output are dangerously wrong. (In some cases, I believe they are simply lying.)

On the other hand, the Sun clearly plays a very important role in our climate. There's a tendency (by some) to chalk everything up to increasing greenhouse gases, and to dismiss the role of the solar cycle.


This study helps us to begin to better understand how and to what extent the solar cycle affects our climate.

…

"These results are striking in that they point to a scientifically feasible series of events that link the 11-year solar cycle with ENSO, the tropical Pacific phenomenon that so strongly influences climate variability around the world," says Jay Fein, program director in NSF's Division of Atmospheric Sciences. "The next step is to confirm or dispute these intriguing model results with observational data analyses and targeted new observations."

…

Building on previous work, the NCAR researchers used computer models of global climate and more than a century of ocean temperature to answer longstanding questions about the connection between solar activity and global climate.

…

"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," says NCAR scientist Gerald Meehl, the paper's lead author. "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 better we understand the systems we're dealing with, the better our chances of successfully dealing with them.

[Narkos]

6. Okay, I'll buy that

but I've seen you post a couple of items that seem to subtly suggest that climate change is not man-made. I think we can all accept that climate science is incredibly dynamic and complex, and there are many factors at play. I just find it odd for someone to be doing that on a liberal leaning political forum.

[The Croquist]

7. I post not so subtly that it is largely not man made.

You may have us confused.

That said, I think that what OKIsItJustMe's #5 post is pretty much much right on. Most knowledge is good (how to books on building nuclear weapons being an exception to the rule).

The fact that it jumbles the mix up a little bit is besides the point. The research also centers on the 11 year solar cycle and linking it to short term temperature fluctuations. It does little to blame 100 years of temperature increase on the sun. About the worst case you can make is that if an 11 year cycle is out there, what about longer cycles that we may not as of yet have clearly identified?

[OKIsItJustMe]

8. "… seem to subtly suggest that climate change is not man-made …"

I guess I'd need to see those postings.

My general take on things is this:

1. Incidents of "Climate Change" (both "Global Warming" & "Global Cooling") have happened before in the geologic record, with no influence from us. From this, we know that there are "natural processes"† which are sufficient to cause "climate change." (See "http://en.wikipedia.org/wiki/Paleoclimatology">Paleoclimatology.")


2. Relatively recent incidents of rather dramatic "climate change" (i.e. "ice ages" and "thaws") appear to have been kicked off by seemingly small changes in insolation (see "http://en.wikipedia.org/wiki/Milankovitch_cycles">Milankovitch cycles") the direct effects of which were apparently amplified by "http://en.wikipedia.org/wiki/Climate_feedback#Feedback">feedbacks;" some of which we believe we understand, and some of which we http://manoa.hawaii.edu/cgi-bin/uhmnews2?20090714185609">apparently do not!


3. Just as "forest fires" can happen "naturally," or can be set off by humans accidentally, through some seemingly insignificant act (carelessly burning love letters, for example) which leads to a disproportionately large result; I believe humanity may also kick off "natural processes" which have led to "climate change" in the past. The "skeptics" are right when they say the amount of "greenhouse gases" we release is small compared to the entire "http://en.wikipedia.org/wiki/Carbon_cycle">carbon cycle." However I believe they underestimate the cumulative effects of a century and more of such emissions, on what is apparently a rather precariously balanced system.


4. "Climate Change" in the past http://en.wikipedia.org/wiki/Permian%E2%80%93Triassic_extinction_event">may have led to mass extinction. The potential risk here is overwhelming, we need to understand what we're dealing with, so we know what actions to take.

So, in a sense, I guess you could say that I don't feel that "climate change" is entirely "man-made," in that "Climate Change" is "natural." However I firmly believe that humanity has the ability to set things in motion, and may have already done so. Which is to say, that I firmly believe that "http://dictionary.reference.com/browse/anthropogenic?jss=0">anthropogenic climate change" is a very real hazard.

This is what scares me most about "climate change" i.e. the fact that we may be actuating "natural processes" which may quickly be (if they are not already) far beyond our ability to control.


If, the primary cause of "Global Warming" is our emission of "greenhouse gases" then our response seems clear; we must stop emitting them (ASAP) and do everything we can to decrease current atmospheric concentrations. If, however, (as one recent study suggests) the primary cause of "Global Warming" is the accumulation of our "waste heat," with "greenhouse gases" having only a secondary influence, then putting our efforts into reducing "greenhouse gases" without reducing "waste heat" (ex: by building nuclear plants to replace coal plants) would be wasted effort. While using tremendous amounts of additional nuclear power in an attempt to "artificially" remove "greenhouse gases" from the atmosphere (as some have suggested) might have disastrous consequences.

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† I put "natural" in quotes, because there is a tendency to speak of "humanity" as separate from "nature," as if we were not a part of "nature."