SOLAR FORCING: The sun's variability actually has a big impact on Earth's climate.
Image: Courtesy of NASA
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Small changes in the sun's brightness can have big impacts on our planet's weather and climate. And now scientists have detailed how that process might work, according to a new study published August 28 in Science.
For decades some scientists have noted that certain climate phenomena—warmer seas, increased tropical rainfall, fewer clouds in the subtropics, stronger trade winds—seem to be connected to the sun's roughly 11-year cycle, which causes ebbs and flows in sunspots that result in variations in solar output.
That variation is roughly equal to 0.2 watt per meter squared—far too little to explain, for instance, actual warming sea-surface temperatures. A variety of theories have been proposed to explain the discrepancy: ozone chemistry changes in the stratosphere, increased sunlight in cloudless areas, even cosmic rays. But none of these theories, on its own, explains the phenomenon.
Now, using a computer model that pairs ozone chemistry with the fact that there are fewer clouds in the subtropics when the sun is stronger, climate scientist Gerald Meehl of the National Center for Atmospheric Research (NCAR) in Boulder, Colo., and colleagues have reproduced all the observed cyclical climate phenomena as sunlight waxed and waned in intensity over the course of the last century. "Even though [sunlight variability] is a very small number on a global average, regionally or locally it can be much bigger," Meehl explains. Changes to stratospheric ozone chemistry and cloud cover in the subtropics "kind of add together and reinforce each other to produce a bigger amplitude of this small solar forcing signal," he says.
If the model is correct, the mechanism works like this when the sun is at maximum strength: Ozone in the tropical stratosphere traps slightly more heat under the increased ultraviolet sunlight, warming its surroundings and, in turn, allowing increased ozone production. (Warmer temperatures make it easier for ultraviolet light to break up O2 molecules, thereby allowing the resulting free oxygen ions to hook up with other molecules of their kind to create ozone.) That ozone also warms and the cycle continues, resulting in roughly 2 percent more ozone globally. But this change also begins to affect the circulation of the stratosphere itself, which then alters the circulation in the lowest layer of the atmosphere, known as the troposphere, by reinforcing certain wind patterns that then affect the weather we experience.
Meanwhile, the increased radiance during the solar max also adds slightly more heat to the ocean in areas that are already relatively cloudless because of sinking, cooler air. That produces a little more evaporation, which is carried by the trade winds back into the tropics where it comes down again as increased rainfall, but also helps strengthen the upward convection that causes the subtropical cloudless skies. That, in turn, further increases downward pressure back in the subtropics, resulting in even fewer clouds—again roughly 2 percent less clouds over these parts of the Pacific. "You basically spin up this whole system," Meehl says.
But the model did not exactly reproduce real-world conditions. Whereas sea-surface temperatures in the actual eastern Pacific typically decline by roughly 0.8 degree Celsius under a stronger sun, the model could only replicate about 0.6 degree C of cooling. Nor did the model predict changes where they actually occur on the planet. Other factors are likely at work, Meehl says, and even the best computer model can only begin to approximate the complexity of the actual climate.
Right now, the sun is stuck in a period of extremely low sunspot activity, not unlike the "Maunder Minimum" that may have been responsible for the Little Ice Age that cooled Europe in the late 17th century as well as the fall of imperial dynasties in China. And, for the latter half of the 20th century, the sun's output remained relatively constant as global temperatures rose—ruling out our star itself as the direct source of global warming.
Nevertheless, the research begins to explain the physical mechanisms by which changes in the sun's radiance can have outsized impacts on the planet. And that means that the next uptick in the solar cycle, and thereby the sun's brightness, might bring La Niña conditions—unusually cold surface waters—in the equatorial Pacific. "Whenever it happens," Meehl predicts, "chances are it would behave like a weak La Niña–like pattern."
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21 Comments
Add CommentMombo jumbo -- When recorded temperatures on Mars, Earth and Venus all increase I would suggest a common influence and it is not industrial pollution.
Reply | Report Abuse | Link to thisBesides the amount of Methane that will be released from the melting tundra in the next decade will exceed the global industrial output for the past two centuries.
In other words were cooked!!
Say what?
Reply | Report Abuse | Link to thisIn the mid-to-late '90s, the sun peaked at a grand solar maximum vis-a-vis the last 10K years. If it is indeed accurate that the effects of said maximum were amplified, then this is a major dagger into the heart of the theory of global warming.
Which shouldn't bother anyone interested in the truth but will definitely bother those to whom global warming is more than just another theory.
"When recorded temperatures on Mars, Earth and Venus all increase I would suggest a common influence and it is not industrial pollution."
Reply | Report Abuse | Link to thisDid you read the article? Why would you think the atmospheres of Venus and Mars would in anyway behave like Earth's.
/The eye altering alters all/
"Sunlight controls climate" registers as SciAm's biggest duuuhhh ever. Congratulations go to lame brain editors and sensational writer, David Biello.
Reply | Report Abuse | Link to thisI find it hard to believe, not one mention of AGW in this article.
Reply | Report Abuse | Link to thisSomeone must have been asleep at the switch.
How refreshing, a science report without a paid political pronouncement.
Good advise!
Reply | Report Abuse | Link to thisv.gates
Reply | Report Abuse | Link to thisThere are more daggers and stakes through the heart of the discredited theory of man made global warming than in all of the Dracula movies combined, but like some character from a Monty Python movie the MMGW true believers keep jumping up proclaiming "It's only a flesh wound! Come back you coward!".
In science, you don't need multiple daggers through the heart to kill a theory, one will suffice. But according to MMGW true believers, unless every one of their beliefs is disproved, they take it to mean that their religion is still true.
It's impossible to prove them wrong; their faith in their religion is unshakeable.
Shoshin,
Reply | Report Abuse | Link to thisYes, it's a religion to many and a very warped one at that. The harm these zealots are causing and will continue to cause is huge. I heard somewhere that the food products required to produce one tank of the ethanol that they have foisted upon us would feed a family of four in a 3rd-world country for a year! Could that be true?
I suspect you are both right v.gates and Shosin.
Reply | Report Abuse | Link to thisWhat I find most frustrating about the whole global warming issue is how for so many advocates of the global warming theory, the theory has passed beyond science and reason and into the area of faith. There is a well worn expression that extraordinary claims require extraordinary proofs. I would submit man made global warming is a rather extraordinary claim. When you consider that earth has been cooling for the last eleven years and that our long term temperature measurements are full of uncertainties and biases, I would suggest that the only rational and scientific position is one of skepticism.
Don't be confused because the weather seems to be about the same from day to day, and that is the only real connection you have to climate.
Reply | Report Abuse | Link to thisThe Earth's climate has been all over the place over the past millions of years, and even of the past 500 years. It can and will change in the future as well.
Mankind has altered the ecosystem of the Earth by dramatically increasing the concentration of infrared active gases and particles in the atmosphere over the course of the last 100 years. It is simple physics that the infrared active gases strongly absorb and emit infrared radiation, thereby changing the temperature structure of the atmosphere and adding infrared radiation to the surface.
The overall radiation balance struck between sunlight from our star and infrared radiation from our planet is likely to continue. The planet's reflectivity strongly affects this balance. The types of clouds and land surfaces determine the planet's reflectivity. Water molecules are a highly variable trace gas in the atmosphere and their concentration and phase (ice, water, or vapor) influences weather and climate.
We need to understand as much about our planet and star as possible so that we can plan our future as a species. If it turns out that we miraculously find that the Earth's climate will remain the same forever, we smile and go on about our daily lives. If it is to get colder where we live, we buy coats and think about methods for staying warm, and the opposite if it gets warmer where we live.
It is not an emotional issue. No faith is involved. Science works by assuming that if you strike your thumb with a hammer today, it will have the same consequences today as if you repeat the exercise tomorrow, the day after, and so forth, forever. It is our empirical experience that the laws of physics seem the same every day, so we expect that to be true.
The radiation transfer component of weather and climate has components that are simple to deal with. In contrast, fluid dynamical calculations are notoriously challenging because the system of equations can have great sensitivity to initial conditions. In addition, models need to consider scales from molecules to the atmosphere size.
It is time to quit calling each other names, quit with uncertain propaganda, and to start with the language of science. What do we know? What are the error bars in our knowledge? What do we not know? Can we improve upon our knowledge of the unknown?
Don't worry, people are going to use a lot of gas and coal. Likewise, the sky won't fall. Think
"When you consider that earth has been cooling for the last eleven years"
Reply | Report Abuse | Link to thisCompared to what and where?
The top 11 warmest years on record have all been in the last 13 years. We used to have long lasting snow cover where I live when I was younger, these days we're lucky if they last a week.
Some argue that the earth is cooling compared to 1998, but that is a rather far fetched conclusion based on the data.
See http://www.sciencedaily.com/releases/2007/12/071213101419.htm for tables.
The biggest hindrance to doing the proper research necessary for us to even begin to understand our climate and its changes, is those who have made a religion out of "man-made-global-warming". They are demanding that funds be allocated toward the stopping of those things THEY have determined are causing GW; determined without recourse to proper research, I might add.
Reply | Report Abuse | Link to thisPoliticians, being politicians, see this as a means of increasing taxes that will have public consent if not whole hearted enthusiasm. They can be relied upon to push taxes to higher and higher levels; all the while "rewarding" themselves handsomely for "stopping GW."
Oh yes, we are indeed "cooked".... but not by global warming......... Can you say "S U C K E R S !!
Of course, I'm no Astrophysicist, but, and this is only a guess, without sunlight, it might be some colder.
Reply | Report Abuse | Link to thisAlthough, I'd sure like some of that damn Global Warming you guys keep rippin' on. Here, in Michigan, its been a bitchin' cold summer.
It is interesting to watch folks jump on this article and cling to it as evidence that climate change is not real just a cycle and certainly is not man-made. The important cycle here might be the fluxuations in the amount of money being spent by oil, gas, energy, and automotive industries to poke holes in the science that their own scientists warned them about a decade and half ago. The money faucet is fully open at this point and hopefully the Senate will have the good sense and fortitude not to collapse under the weight of the resultant misinformation being offered. Please show me one statement in this article that specifically contradicts the current view that climate change is happening and that it is caused in part by human activity. This article and the modeling talks solely about why solar intensity has a greater impact that would be predicted in certain areas and under what conditions. Period. It is one of the natural cycles that is interwoven in the climate change fabric, but not the only one.
Reply | Report Abuse | Link to thisLinks:
http://www.scientificamerican.com/article.cfm?id=how-sunlight-can-control-c...
http://www.businessinsider.com/oil-coal-auto-industry-lobbyist-lied-about-g...
http://environment.about.com/od/globalwarming/a/globalwarmingad.htm
Ask Maurice...he knows the answer...
Reply | Report Abuse | Link to thisIsnt the only hope for the planet that the industrialized civilizations collapse? Isnt it our responsiblity to bring that about? - Maurice Strong, founder of the UN Environment Programme
Time and time again we see this kind of presentation, 80% of the article provides reasonable and valid points, but then it presents a conclusion that is totally unsupported by the previous data.
Reply | Report Abuse | Link to thisHow can the low solar activity over the last 4 years completely reverse the warming trend during the 80s and 90s, yet the twenty years of high solar activity had nothing to do with the warming.
There is little doubt that CO2 content effects global temperature, but the question is, how much? You cannot increase the influence of solar forcing without decreasing the influence of CO2.
I love this meely-mouth quote:
Reply | Report Abuse | Link to this"...the sun's output remained relatively constant as global temperatures roseruling out our star itself as the direct source of global warming."
Oh . . . ok . . . so the Sun does NOT warm the globe? Oh, you mean that the street term "global warming" is reserved for the Al Gore theologians and their mindless AGWA sheep.
And, of course, we needn't dwell on scientific details like the broadbrush GARBAGE in that quote that coyly declares that the "sun's output" is like the output of an auto plant; it doesn't matter what the exact constituents are, just as long as the broadbrush 1000 vehicles holds: one day it's 100 cars and 900 trucks, the next it's 1000 trucks . . . but the auto plant output "remained relatively constant."
The climate devil is in the solar details, but it should not surprise us that fundraising tabloids like SciAm would print such checkout counter crap. I'm serious. The role of SciAm is stampeding of the cattle with broadbrush goo; that's all they're good for anymore.
How much UV thru IR thru . . . varies considerably, and the meelymouths at SciAm (and NASA) can still spew the crap "remained relatively constant." Pathetic!
I love this meely-mouth quote:
Reply | Report Abuse | Link to this"...the sun's output remained relatively constant as global temperatures rose—ruling out our star itself as the direct source of global warming."
Oh . . . ok . . . so the Sun does NOT warm the globe? Oh, you mean that the street term "global warming" is reserved for the Al Gore theologians and their mindless AGWA sheep.
And, of course, we needn't dwell on scientific details like the broadbrush GARBAGE in that quote that coyly declares that the "sun's output" is like the output of an auto plant; it doesn't matter what the exact constituents are, just as long as the broadbrush 1000 vehicles holds: one day it's 100 cars and 900 trucks, the next it's 1000 trucks . . . but the auto plant output "remained relatively constant."
The climate devil is in the solar details, but it should not surprise us that fundraising tabloids like SciAm would print such checkout counter crap. I'm serious. The role of SciAm is stampeding of the cattle with broadbrush goo; that's all they're good for anymore.
How much UV thru IR thru . . . varies considerably, and the meelymouths at SciAm (and NASA) can still spew the crap "remained relatively constant." Pathetic!
I love this meely-mouth quote:
Reply | Report Abuse | Link to this"...the sun's output remained relatively constant as global temperatures rose—ruling out our star itself as the direct source of global warming."
Oh . . . ok . . . so the Sun does NOT warm the globe? Oh, you mean that the street term "global warming" is reserved for the Al Gore theologians and their mindless AGWA sheep.
And, of course, we needn't dwell on scientific details like the broadbrush GARBAGE in that quote that coyly declares that the "sun's output" is like the output of an auto plant; it doesn't matter what the exact constituents are, just as long as the broadbrush 1000 vehicles holds: one day it's 100 cars and 900 trucks, the next it's 1000 trucks . . . but the auto plant output "remained relatively constant."
The climate devil is in the solar details, but it should not surprise us that fundraising tabloids like SciAm would print such checkout counter crap. I'm serious. The role of SciAm is stampeding of the cattle with broadbrush goo; that's all they're good for anymore.
How much UV thru IR thru . . . varies considerably, and the meelymouths at SciAm (and NASA) can still spew the crap "remained relatively constant." Pathetic!
It is statements like this (below) which have caused me to cancel my subscription (of 30 years) to Scientific American.
Reply | Report Abuse | Link to this"the sun's output remained relatively constant as global temperatures roseruling out our star itself as the direct source of global warming."
Baloney, the sun's output was rising to a maximum and now has fallen into a minimum as temperatures have cooled. Our Star, and only our Star is the source of global temperature.
Keep your fishwrap out of my mailbox, please.
How Sunlight Controls Climate
Reply | Report Abuse | Link to this?????
By being there! If it were somewhere else, it wouldn't. See? No degree required.