Researchers Say Sun Cycle Alters Earth's Climate
Written by Nancy Atkinson
If the energy from the sun varies by only 0.1 percent during the 11-year solar cycle, could such a small variation drive major changes in weather patterns on Earth? Yes, say researchers from the National Center for Atmospheric Research (NCAR) who used more than a century of weather observations and three powerful computer models in their study. They found subtle connections between solar cycle, the stratosphere, and the tropical Pacific Ocean that work in sync to generate periodic weather patterns that affect much of the globe. Scientists say this will help in predicting the intensity of certain climate phenomena, such as the Indian monsoon and tropical Pacific rainfall, years in advance.
"The Sun, the stratosphere, and the oceans are connected in ways that can influence events such as winter rainfall in North America," says NCAR scientist Gerald Meehl, the lead author. "Understanding the role of the solar cycle can provide added insight as scientists work toward predicting regional weather patterns for the next couple of decades."
The new study looked at the connection between the Sun's impact on two seemingly unrelated regions. Chemicals in the stratosphere and sea surface temperatures in the Pacific Ocean respond during solar maximum in a way that amplifies the Sun's influence on some aspects of air movement. This can intensify winds and rainfall, change sea surface temperatures and cloud cover over certain tropical and subtropical regions, and ultimately influence global weather.
The team first confirmed an earlier theory, that the slight increase in solar energy during the peak production of sunspots is absorbed by stratospheric ozone. The energy warms the air in the stratosphere over the tropics, where sunlight is most intense, while also stimulating the production of additional ozone there that absorbs even more solar energy. Since the stratosphere warms unevenly, with the most pronounced warming occurring at lower latitudes, stratospheric winds are altered and, through a chain of interconnected processes, end up strengthening tropical precipitation.
At the same time, the increased sunlight at solar maximum causes a slight warming of ocean surface waters across the subtropical Pacific, where Sun-blocking clouds are normally scarce. That small amount of extra heat leads to more evaporation, producing additional water vapor. In turn, the moisture is carried by trade winds to the normally rainy areas of the western tropical Pacific, fueling heavier rains and reinforcing the effects of the stratospheric mechanism.
The top-down influence of the stratosphere and the bottom-up influence of the ocean work together to intensify this loop and strengthen the trade winds. As more sunshine hits drier areas, these changes reinforce each other, leading to less clouds in the subtropics, allowing even more sunlight to reach the surface, and producing a positive feedback loop that further magnifies the climate response.
These stratospheric and ocean responses during solar maximum keep the equatorial eastern Pacific even cooler and drier than usual, producing conditions similar to a La Nina event. However, the cooling of about 1-2 degrees Fahrenheit is focused farther east than in a typical La Nina, is only about half as strong, and is associated with different wind patterns in the stratosphere.
Earth's response to the solar cycle continues for a year or two following peak sunspot activity. The La Nina-like pattern triggered by the solar maximum tends to evolve into a pattern similar to El Nino as slow-moving currents replace the cool water over the eastern tropical Pacific with warmer water. The ocean response is only about half as strong as with El Nino and the lagged warmth is not as consistent as the La Nina-like pattern that occurs during peaks in the solar cycle.
Solar maximum could potentially enhance a true La Nina event or dampen a true El Nino event. The La Nina of 1988-89 occurred near the peak of solar maximum. That La Nina became unusually strong and was associated with significant changes in weather patterns, such as an unusually mild and dry winter in the southwestern United States.
The Indian monsoon, Pacific sea surface temperatures and precipitation, and other regional climate patterns are largely driven by rising and sinking air in Earth's tropics and subtropics. Therefore the new study could help scientists use solar-cycle predictions to estimate how that circulation, and the regional climate patterns related to it, might vary over the next decade or two.
The team used three different computer models to look at all the variables and each came up with the same result, that even a small variablilty in the sun's energy could have profound effects on Earth.
"With the help of increased computing power and improved models, as well as observational discoveries, we are uncovering more of how the mechanisms combine to connect solar variability to our weather and climate," Meehl says.
The team's research was published in the Journal Science.
Filed under: Environment
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August 27th, 2009 at 2:44 pm
It appears to remain a mystery why the Sun goes through these 'strange to humans' cooling or warming cycles in the last few thousand years. It appears quite clear if the Solar System goes through dense nebula(s), the Suns' Solar wind and heliosphere will go through drastic changes -causing much warmer or cooler periods in far prehistoric times.
August 28th, 2009 at 12:07 am
Hmm. As for climate changing a few thousand years back, I seem to remember that there is evidence or at least ideas of human forcing, as cultures go agricultural. And of course there is a glacial interstitial dynamic in the background, perhaps the larger mystery.
But I don't know of any connection to nebula. Could you provide references, please?
August 28th, 2009 at 12:40 am
And then ther's also the change in UV light, up to 100% change during a solar cycle (while the emission of IR and VL remain fairly stable).
And then there's also the increased magnetic activity of the sun, deflecting cosmic rays that could hit earth.
And then there's also the inlfuence of the solar wind on the upper atmosphere, possibly seeding cloud formation.
And then there's the fact that the solar cycle of 11 years is actually too short to influence the climate, which is measured on a much larger scale (100s of years).
We are still lightyears away from understanding "climate changes"
August 28th, 2009 at 1:23 am
Torbjorn Larsson OM Says
There are articles I've read in the past,which I unfortunately don't have available at this time, that says as the Sun travels around the Milky Way, it will sooner or later run into nebulas' of various types and the Sun will eventually run into the 'dense density wave' of our Galaxy.
I'm talking about many millions of years duration. Going through these various nebulas' can cause material to crash into the Sun causing drastic changes to the Suns' energy output. I am not an expert on this subject. I'm hoping an expert can make this post more understandable and much better clarification.
August 28th, 2009 at 2:41 am
lucky for us to have a star that varies so little.
August 28th, 2009 at 3:28 am
ILTS your comment really sparks the imagination.
regardless of whether or not forces acting on the heliosphere are affecting climate on earth, one could spend a certain amount of time examining the heliosphere in general and forming theories on the various influences that it has on the solar system; if any measurable at all.
the voyagers are out that way these days. check out some of their findings here:
http://voyager.jpl.nasa.gov/
August 28th, 2009 at 11:19 am
Pvt.Pantzov Says
Thank you for the link. It's interesting to periodically check the progress of the Voyagers and amazing they are still working after all these years;it is unfortunate the computer tech is of the early 70s , but it does address the vast distances required to travel in the Universe–the Voyagers are still in the Suns' backyard!!!;. As I interprete from articles I read in the past, should the heliosphere be 'squashed' into the inner Solar System, perhaps into the orbit of Mercury, far more Cosmic Rays/charged particles from 'true' outer space will hit the Earth-traveling through a dense Nebula will cause the Suns' heliosphere to contract, I don't think it would be healthy for Earth to be hit by far more Cosmic Rays/charged particles, but the Suns' energy output can be affected in a way beyond my knowledge/understanding.
August 28th, 2009 at 7:56 pm
ILTS, perhaps you may find some useful material and links to the 'galactic year' on this wiki page: http://en.wikipedia.org/wiki/Galactic_year . While the idea that repeated passages of our solar system bobbing and weaving through denser arms of the Milky Way has been debated for years, AFAIK no such 1:1 correspondences have been found regarding mass extinctions or changes in solar output (or composition), and has never been correlated wrt our solar system (check our the timetable at the linked wiki page to events occurring during our stars' ~18 orbits around the Milky Way).
August 29th, 2009 at 1:57 am
Jon Hanford Says:
Thank you for posting and the link. These articles I read was from Scientic American and Science some years back-the articles was actially more of a theory what could happen should the Solar System enter various types of dense Nebulas. The effect would take years if not many thousands before the Sun is affect. They described the Earth can cause some strange climate conditions but the Earth is responsible for 2% of our climate while our Sun more or less is 98%. The articles desribed ' frozen Earth', according to the articles,this happened several times far in the past and for a few times occured about 500MY apart or 2 Calactic years-they think this happened 3-4 times before it stopped as the Solar System cannot travel in the same path around the Milky Way due to slight gravitational interference from other stars and the Galaxy itself.They believe the Sun was in a 'fever' serveral times in the past causing the Earths' climate to be much warmer than today and perhaps during the Jurassic period.. They admit it will be extremely difficult if not impossible to find the reason and the 'smoking gun' what caused these serious overheating and super cooling of the Sun, However, they did say the Earth is NOT capable of causing such super heating or cooling of its' climate by itself regardless of Earths' internal heat source and continental drift. They said the Sun has the last word on what happens with Earths' climate..
Interesting articles, however, I don't know what issue it was, but it was before Y2000,
August 29th, 2009 at 2:14 am
Humans are starting to attempt to slow or eventually stop the production of CO2. It makes me wonder if after 100 years of near zero C02 production, and the Earth is still warming, how long will humans continue to produce near zero C02 but after another 100 years, the Eartg is accelerating its' heating.!!
Although I will have long turn to dust, I would think the people will have to consider mass migrations from the previous productive areas that turned into arid areas and head North like prehistoric humans had to do when the Earth turned much cooler up North.
and had to head South. However, with so many hundreds of million if not a few billion people having to migrate to greener pastures,'this can be dangerous as there will be competition for resources and probably protracted wars will be the outcome!!!!
August 29th, 2009 at 2:34 am
Sorry to those who lives in the Southern hemisphere. Besides 'puters, Astronomy, graffics, multimedia, I research alot about the climates of the Earth. Perth Australia, with a Mediterranean climate, mild, rains in winter, dry Summers. It appears the 30 year average 1921-1950 showed Perth received 38inches
(97CM) per year, while 1971-2000 showed
25inches (64CM) . I search where they took the readings, and it was pretty much the same as 60 years ago with no hi-rise interference..Dammm, that is bad-Perth is a nice big city and I visited the place the other year for a month to see Comet Mcnaught in Jan-Feb07 besides seeing the tourist traps lol. De-saltination treated water is expensive!!!!!!!.
I hope to travel to Chile coastal areas one day.