When Students Listen: Atlantic Multi-decadal Oscillation
When Students Listen: Atlantic Multi-decadal Oscillation -
This week a student who took my class a couple of years ago and also helped me with my class this past term, Kevin Reed, wrote me a message that he remembered my commenting in class that the Atlantic Multi-decadal Oscillation might not be real. He made reference to a paper in Nature entitled Aerosols implicated as a prime driver of twentieth-century North Atlantic climate variability. A good thing about students is that they get to read all sorts of interesting things, send them back to me, and help me appear smarter than I am.
The term “Atlantic Multi-decadal Oscillation” (aka AMO) has been used to define the variation of sea surface temperature in the North Atlantic Ocean. What did I mean in class when I said “it might not be real?” There is no doubt that the temperature of the Atlantic Ocean varies, and as we take and accumulate measurements we identify extended times when the ocean is warmer or cooler than average. When these data are plotted, we see these warmer and cooler time spans persist for a few tens of years; hence, a multi-decadal oscillation. The plot below is taken from a good article in Wikipedia, and the plot was made from data that is available at the Earth Systems Research Laboratory.
Figure 1: An area index that measures how much warmer or cooler the North Atlantic Ocean is from a long-term average (from Wikipedia). (The indices for the Atlantic Multi-decadal Oscillation are not especially well documented in the web resources that even a reasonably informed practitioner can find. The indices tend to be averages of the Atlantic surface temperatures from somewhere in the deep tropics to Greenland. They are then subtracted from long-term means. The 20th century mean is used in some papers. This example demonstrates some of foibles of data, data documentation, and data presentation on the web.)
The Atlantic Oceanographic and Meteorological Laboratory has a nice set of Frequently Asked Questions about the Atlantic Multi-decadal Oscillation.
I want to revisit this figure that I use as a template to think about the natural science of the Earth’s climate.
Figure 2: A summary figure I use to organize the basics of climate science and global warming.
A focus on the Atlantic Multi-decadal Oscillation is most naturally categorized in Figure 2 as “internal variability.” When we talk about global warming in the past 100 years and the next 100 years, internal variability usually refers to states of the atmosphere and ocean that are persistent for some amount of time – weeks, months, years, decades. For example, in El Nino the temperature of the ocean in tropical eastern Pacific is warm and stays warm for a few months or more. Then in La NIna the eastern Pacific is cool and stays cool for a few months or more. There is an easy feeling of the Earth oscillating back and forth between the warm and cool times in the eastern Pacific Ocean. For El Nino and La Nina, there are many related changes in atmospheric circulation (the trade winds change) and precipitation (tropical convention moves east and west). All of these related changes fit together, and they describe the atmospheric and ocean behaving as a coherent system. This coherent behavior allows us to understand cause and effect; it allows the possibility for prediction.
On a scale of a million years, the cycles between the ice ages and temperate times might be internal variability. This would be related to, for example, carbon dioxide coming into and out of the ocean due to changes in temperature and biology. So far, I have been diligent not to call internal variability “natural variability.” El Nino and La Nina are “natural,” but that does not mean that their behavior will remain the same as the climate warms. To call internal variability “natural” suggests this idea of a “natural” and a “manmade” climate that are two different things, and this idea is clearly not the case. We have our climate, there is internal variability, there is manmade warming, and they all occur together, and they will change together.
The Atlantic Multi-decadal Oscillation is internal variability. When I stand in front of class and say the Atlantic Multi-decadal Oscillation might not be real, I mean several things. At the foundation of my statement is that we don’t have this story of coherent behavior like we have in El Nino and La Nina; we don’t have a construction of the atmosphere and ocean behaving as a connected, dynamic system. In fact, I would argue that the issues I raise in the caption of Figure 1, for example mushy definitions of indices, indicate the challenges of the Atlantic Multi-decadal Oscillation. We know there is a signal, but it is even hard to describe that signal very well. When we link back to cause and effect, one of the leading ideas is that it is related to subtle changes of global scale ocean circulation, which we neither model nor observe very well. So I don’t say that the signal of the temperature change is unreal, but I suggest that the Atlantic Multi-decadal Oscillation is not a coherent sloshing back and forth between warm and cold.
One reason we are interested in the Atlantic Multi-decadal Oscillation is that we know that there are strong relationships between the temperature of the ocean in the tropical North Atlantic and drought and flood in North America and Africa. We know that warm Atlantic sea surface temperature is very highly linked to hurricanes in the United States. One of the scientists most quoted as a skeptic of the science of global warming, Bill Gray, bases much of his climate change argument on the role of Atlantic Multi-decadal Oscillation as a proxy for global climate. (For those who are interested, go back to Forms of Argument, and look at the focus on isolated information and reliance in this case on the reality of a process that is both hard to model and observe. How does this stand up in the face of all that we can observe?)
Back to the paper in Nature referenced in the first pargraph, Aerosols implicated as a prime driver of twentieth-century North Atlantic climate variability. This paper is a set of model simulations of the past century and a half. The simulations are associated with the Coupled Model Intercomparison Project Phase 5 (CMIP5). CMIP5 represents a coordinated set of simulations run by scientists around the world with the most recent production-ready climate models. I expect a set of interesting new results to be reported from these simulations especially with regard to the role of aerosols and land use in the climate. Aerosols, particulates in the atmosphere, have strong regional climate impacts, and are closely related to air quality – two of the other items listed in my Figure 2 template.
The point of Aerosols implicated as a prime driver of twentieth-century North Atlantic climate variability by Ben Booth and coauthors is that temperature changes associated with different amounts of aerosols at different times can explain the majority of the variability observed in the temperature of the North Atlantic Ocean. Natural sources of aerosols include volcanoes, which cool the Earth’s surface. Other natural sources are salt and soil dust. Manmade aerosols include pollutants, soot, and soil dust. (old Rood blogs - Volcanoes and Long Cycles, and Black Carbon) What aerosols do is to change the absorption and reflection of solar radiation; the absorption and reflection of clouds; and how efficiently heat is held near the Earth’s surface. In the simulations by Booth and others, the predominant impact of aerosols is related to effects on solar radiation – both directly by reflection (volcanoes) and indirectly by changes to clouds. Earlier studies have investigated the effect of volcanoes, and this study brings to the forefront the importance of other sources of aerosols, many of them manmade, in modulating global climate with strong regional influences.
The numerical experiments in Booth et al. (2012) are well designed. But they are complex, and, well, numerical experiments. I hold such numerical experimentation as an important part of scientific methodology of the 21st century. They help us think in a field where our ability to execute controlled experiments is limited. To me, these experiments suggest a strong, well-based explanation of the variability of North Atlantic temperatures. However, scientific method requires more scrutiny, more use of observations, and independent verification of the results. But as it stands right now, we have at hand a plausible explanation of cause and effect that explains the majority of the observed variability.
To finish another long article – The work of Booth et al. (2012) extends back to 1860. The Atlantic Multi-decadal Oscillation extends back, well seemingly, at least 8000 years. In Nature Communications there is an article Tracking the Atlantic Multidecadal Oscillation through the last 8,000 years by Mads Faurschou Knudsen and others (2011). This paper concludes that for most of the time since the last ice age ended, there has been a 50 – 70 year oscillation, which they attribute to atmospheric-oceanic coupled behavior modulated by variations in the orbit of the Earth. As I understand this paper, the authors tested whether or not variations in the Sun could explain their observed variability. Since solar variability did not explain their observations, they accepted the hypothesis that atmospheric-oceanic coupled behavior provided the explanation. They did not investigate the impact of aerosols.
As it stands in my mind today, the variability in the North Atlantic temperature behavior is strongly influenced by aerosols in the atmosphere and a trend due to increasing carbon dioxide. If there is oscillatory behavior in the temperature, it is due to increases and decreases in atmospheric aerosols, perhaps on top of a smaller atmospheric-oceanic dynamic variation that still requires explanation. A good step forward, I think.
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Reader Comments
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If you're implying he shouldn't rely so much on the AMO, I don't see why. Just because we don't know much about why the AMO exists doesn't mean we don't know how it influences the weather, and in turn can use it as a powerful forecasting tool.
2:57 AM GMT on May 08, 2012
Useful for thinking about hurricanes.
Not a solid foundation to frame global climate.
Levi32, I am very glad that you here. I can easily learn some of the aspects concerning the AMO just by reading about it, but observing the conversations of better minds than mine delve into its varied aspects is a much better learning tool for me to use. I hope that you decide to continue your comments. At least until the coming hurricane season diverts your attention towards the season? Do you mind?
can keep this in
the blue to restore Arctic Ice and regulate our climate..........
Thanks for the article.
Has anyone investigated a possible pulse or something like that in the general Atlantic current structure that would allow tropical water to pick up more heat at sometimes and not at others?
The time frame, multi-decadal, implies a very large system that is showing variation and the ocean current system is one of the biggest.
I am so pleased that the Weather Underground has begun to dedicate time and space to the critical issues surrounding AGW and Climate Change.
Would it be possible at some time for you to provide your insights about the difficulties and complexities associated with the development of predictive climate models. I'm very familiar with the use of Monte Carlo simulations in the development of complex weapon systems (Guided Missiles, Ballistic Missile Defense, etc.). In that world the majority of the variables were ostensibly within the control of the designer, leaving only the operational environmental conditions as independent variables to be considered in the modelling algorithms.
Whereas the development of accurate climate models is many times more complex. There are so many independent variables from the various forcing mechanisms to feedback loops that need to be factored in to the simulations. I admire the work that has already been done in this area, because I appreciate the complexity of the task.
What I would like is the professional perspective of climatologists on this topic. What are some of the unknowns that need further research to make the models more reliable.
The multidecadal oscillation I'd helped discover would nonetheless become a cause célèbre among climate change contrarians. It would even get a name: the "Atlantic multidecadal oscillation" (AMO)—a moniker I coined off the cuff in a phone interview with science writer Dick Kerr. The AMO appeared to be real, and at least partly responsible for certain phenomena, such as the acceleration of recent warming in parts of the Arctic, that some had attributed to anthropogenic climate change. Other phenomena that have been blamed on the AMO, such as the increase in Atlantic hurricane activity in recent decades, arguably have nothing to do with it all. That hasn't stopped climate change contrarians, however, from dragging out the AMO as a favorite catch-all explanation for just about any observed climate trend. At times I have felt like I helped create a monster.
Thanks for an interesting article, Prof. Rood. I'm unconvinced that that AMO actually exists absent human influence, much less has anything to do with climate. I wouldn't argue against its existence in the 20th century, based on both the graph above and the Booth paper, but I think that that's all that can be shown with any confidence.
Tamino recently wrote a nice blog on this subject.
3:08 PM GMT on May 08, 2012
I will try to do some on this subject. While it's not a control theory process like you explain, there are some principles of information theory as applied to providing initial conditions that are important.
There are problems of forcing, like the one I suggest in the current blog post, what are the aerosol amounts and optical properties. And, of course, greenhouse gases. But I think must people would say the big challenge is ocean circulation and multi-year variability in the ocean - and ocean initialization. The ocean state then strongly influences the weather and hence climate.
Dr. Rood,
Thank You for your prompt and informative reply. That's why I'm here....to learn from experts who are much more knowledgable than I am.
Ditto!
I have already learned much from the many informed people that post here. You are new here and I have already learned from you as well.
I have watched this blog turn from a personal attack blog into a Science blog over the past few months. This could not have happened without the persistence of Neapolitan, Birthmark, Greentortuloni, Percylives, Xandra, Lowercal, Alwaysthinking, Cyclonebuster and several others that use actual Science to expunge the pseudoscience others have tried to introduce. Thanks, in large part to their efforts, the trolls, deniers of the fundamental basics of Science, antagonist, ideologues and sociopaths have fallen victim to their own pseudoscience and bias and have fallen to the side. Science will rule the day, even if it ruins the day. ;-) ... The Laws of Physics simply do not respond to polls.
Knowledge has not yet conquered ignorance, but now the door is open for it to do so. ... Unfortunately, those that choose to live by their own self induced ignorance will never gain further knowledge beyond their own liking.
How True!!
I'm glad to be joining such a knowledgeable and collegial learning environment. However, I must share my motto regarding the sharing of knowledge and the spirited debating of facts:
If two people agree on everything, one of them is not necessary!
Moral support? LOL
Oh, I agree. That is the lovely thing about Science. There is always something to debate, knowledge to be gained and thoughts provoked with out egos being trounced upon. ;-) ... Yeah, if all I wanted was a gathering of people patting themselves on their backs, then I would just join one of the "good ole boys" clubs. ;-)
Interesting, I found these tidbits from the last blog
topic.
162.
A) It wasn't a "paper", but a letter signed by a bunch of crotchety old denialists, many with no formal training or experience in climate science. B) I didn't "pick out three names", I simply scanned the list and realized you were doing nothing but again bringing up the same batch of bad actors, as represented by two names that stood out. (Suggest you read Merchants of Doubt by Naomi Oreskes; Fred Singer's name is repeated more than any other)/ The point being, once you throw in the likes of Singer and Scafetta, you have immediately lost almost all credibility. C) I merely brought up Muller's name to note that, if you're trying to make a case against global warming, he's no longer a very good witness for your side, since he's been forced by fact to recant much of his denialism. Next time you cut and paste that list, you may wish to excise his name. Just trying to be helpful.
So, again: what else you got? Or is that about it
163.
Crank science calls this an absence of warming. That's deliberate deceit. It is a play on the fact that it takes many years to establish a statistically significant trend --at least 17 years, according to Santer. 1995-2012 isn't even seventeen years at this point.
Of course, fans of crank science also fail to note that both GISTEMP and HADCRUT4 do show statistically significant warming -UAH does not, though it may by the end of the year. So, you are cherry picking, failing to give a fair assessment of the totality of the data
By Matt Peckham | @mattpeckham | June 15, 2011
You know what they say about a leopard not changing its spots, but when it comes to our sun, change is all but guaranteed. In fact new research suggests the sun may be on the verge of changing its sunspots in a way that could significantly alter weather patterns for the long haul, both on Earth and in space.
Three studies presented by scientists at a conference in Las Cruces, New Mexico yesterday predict that sunspots are set to temporarily and unexpectedly vanish in coming years as part of a solar “hibernation” period that could last for decades.
The consequences for us? Possibly global cooling, for starters—a byproduct of an extended period of “solar minimum,” in which sunspot and solar flare activity would be diminished. The sun usually runs through an 11-year cycle during which sunspot activity waxes and wanes. The last solar “maximum”—the point at which upwards of hundreds of sunspots may be active on the sun’s surface—was back in 2000. The current peak is expected in early 2013, and it may be one of the weakest since 1928, though we’re kind of bad at predicting these things: NASA had previously suggested the cycle would peak between 2010 and 2012 and that it would be “the most intense solar maximum in fifty years.”
The same approach employed to determine that year or two delay in solar maximum—an approach dubbed “helioseismology” that studies seismic wave activity on the sun—now suggests the sun is entering a relatively quiet period, prompting weaker future solar cycles.
So are we headed for another “little ice age,” like the exceptionally cool period that occurred between 1645–1715, known as the Maunder Minimum, when astronomers reportedly observed little to no sunspot activity? Probably not, though according to Tom Woods, associate director of the Laboratory for Atmospheric and Space Physics at the University of Colorado, the shift in solar activity could alter warming predictions by climate scientists.
Prepared jointly by the U.S. Dept. of Commerce, NOAA,
Space Weather Prediction Center and the U.S. Air Force.
Updated May 07 2200 UTC
Joint USAF/NOAA Report of Solar and Geophysical Activity
SDF Number 128 Issued at 2200Z on 07 May 2012
IA. Analysis of Solar Active Regions and Activity from 06/2100Z
to 07/2100Z: Solar activity has been at moderate levels for the past
24 hours. Even though Region 1476 (N10E48) is the largest, 810
Millionths, and most magnetically complex, Fkc/beta-gamma; todays
only M-class event came from the sunspot cluster Region 1470
(S15W57) and Region 1471 (S19W50). This sunspot complex produced an
M1/1n x-ray event at 07/1431Z. Multiple discrete radio frequency
bursts were associated with this event, as well as a 240 sfu
Tenflare and a Type IV radio sweep. These characteristics, as well
as COR2 imagery from the STEREO A spacecraft suggest an Earth
directed CME. Initial analysis suggests only a weak disturbance of
the Earths magnetic field. Earlier in the day around 07/0400Z,
another CME was observed in STEREO A imagery but after analysis, it
was determined to not have an Earth-directed component. Region 1476
continues to grow in size and magnetic complexity as it rotates
further onto the solar disk.
IB. Solar Activity Forecast: Solar activity is expected to be at
low to moderate levels for the next three days (08 - 10 May).
IIA. Geophysical Activity Summary 06/2100Z to 07/2100Z:
The geomagnetic field has been at quiet levels for the past 24 hours.
IIB. Geophysical Activity Forecast: The geomagnetic field is
expected to be at quiet to unsettled levels on day one (08 May) as a
solar sector boundary crossing is expected, as well as possible
effects from a weak CME, observed leaving the solar disk on 05 May.
Quiet to unsettled with a chance for active levels are expected on
day two (09 May), as a coronal hole high-speed stream (CH HSS) moves
into a geoeffective position. Quiet to active levels with a chance
for minor storm levels are expected on day three (10 May) as effect
from the CH HSS continue with the possible arrival of todays CME.
Link
I see what you are driving at, but those are far from personal attacks. None of the derogatory comments are directed at you or at anyone in particular. They are general statements.
Iceage, you have seen the personal attacks this blog was notorious for. Egos clashing against egos. Ideology at odds with reality. The name calling, tagging and labeling was rampant here. You and I have never, that I remember, resorted to personal attacks on each other. Yet, we have both experienced them here. Do you not sense the change away from this?
You bring many weather related posts here and try to make a connection to a coming ice age. Your posts would be compelling, if the global observations did not show otherwise. All of us are just as guilty of making weather posts while trying to make a point. The posts that show weather of a warming world are supported by the actual observations and long term trends of these observations.
Let us say that you are correct. We are soon heading towards another ice age. You have the evidence of this, but this information has only fallen on deaf ears. I still would not fear an impending ice age because we have the knowledge, technology and willingness to rewarm the climate and thus probably avert any serious damage to life on Earth. The reverse of this is not so easily accomplished and on so many levels. We witness this today.
ExxonMobil's Dirty Secrets From Indonesia to Nigeria to D.C
From the description of the video:
We continue our conversation with Pulitzer Prize-winning reporter Steve Coll, author of the exhaustive book, "Private Empire: ExxonMobil and American Power." He examines controversial role ExxonMobil has played in Afghanistan and Indonesia, where it operated lucrative gas fields amidst a bloody war for independence. Coll also discusses the corporate giant's involvement in the controversial natural gas drilling process known as "fracking" known as fracking, and the role of its lobbyists could play in the upcoming U.S. election.
Part 1 of this interview
South Pole hits minus 100F mark earliest ever in the winter
By Peter Rejcek, Antarctic Sun Editor
Posted April 20, 2012
It’s no secret that the South Pole in Antarctica is one of the coldest places on Earth.
But this year it got really cold faster than ever, breaking a 30-year-old record for the earliest the temperature has dropped below minus 100 degrees Fahrenheit (minus 73.3 degrees Celsius).
The mercury officially bottomed out at minus 100.1F (minus 73.4C) on April 7 (local time), less than three weeks after the one sunset of the year that occurs at the bottom of the world. Previously, the earliest the temperature had broken the minus 100F barrier was on April 8, 1982 (local time), plummeting down to minus 103.4F (minus 75.2C).
“Climatology shows that it isn’t as atypical as one would think,” said South Pole Station FPRIVATE "TYPE=PICT;ALT=External Non-U.S. government site" senior meteorologist Dale Herschlag.
Link
Must be more Crank Science!
Dale Herschlag's Overview
Current Senior Meteorologist at PAE
Past Meteorologist at Raytheon Polar Services
Meteorologist at Raytheon Polar Services
Raytheon is part of the Idustrial Complex Conspiracy
By Matt Peckham:
[CLARIFICATION: Some commenters seem to be confused about the terms "global warming" and "global cooling." As I'm using them, they refer to the forces impacting the overall temperature of the Earth's atmosphere. A less active sun may have a "global cooling" effect on the planet. That doesn't mean the impact of greenhouse gases or the average overall thermal trend are offset. In fact it has nothing to do with offsets or equation balancing. It simply refers to the hypothetical impact of the phenomenon—in this instance, a temporarily less active sun.]
Source
"Climatology shows that [reaching -100 in early April] isn't as atypical as one would think."
Aww shucks! Someone you deserve just as much credit as the rest and for being a better angel when we are ready to gouge eyes certainly is something you should be credited for. Take a bow sir we are just as enamoured with you as you are with the rest of us! And on that note the mockery of the Heartland Institute continues!
Good thing he clarified. Of course, we recently had a deep and protracted solar minimum. Here's what happened:
I don't think we're going to be seeing any cooling trend in the near future. I think even a Maunder Minimum type event will only slow down the warming slightly.
Still, it'd be a good break for us and might give us a little more time to take action.
So now that the Arctic Sea Ice is melting at break-neck speed, the fight moves to Antarctica, eh? ;^D
There are two things that are noteworthy here:
1. Even with possibly diminished solar activity over the next few years, the article points out that we would likely not see even a mini ice age as a result of this.
2. I suspect that a global cooling will not be observed, but that it is just me. I suspect more that less/slower warming will be the result and not an actual cooling down of the planet.
An actual cooling, or even a slowing of the warming, may be the most detrimental thing that could happen to us. When I say "us", it is in regards to all of the citizens of this planet. Allow me to explain this statement. Should a cooling, or a decrease in the amount of warming, occur then the motivations to lower anthropogenic CO2 emissions will also decrease. A false sense that everything is going to balance out will take control over reasoned thought. We will likely see even more anthropogenic CO2 will being released. Also likely, this will happen at an even greater rate. Once the solar activity increases again, and it will, then it will be doing so with even higher levels of CO2 in the atmosphere and a more rapid warming of the climate would be almost assured. This will likely happen when CO2 levels have reached the point to where we have no options available to us any more. The longer the solar inactivity persists, the more likely this will be true. Well, this is what I see when I "play it forward".
That was a rapid decline in extent during the last week of April. How much of that was due to melting or was it just the winds pushing the ice-pack closer together?
No problem. How ya been, Brian?
I have a question regarding the increase of CO2 in the oceans. We know that CO2 is causing increased acidification of the oceans which is detrimental to marine life. In the event that global warming is slowed due to decreased solar activity or Pinatubo-like volcanic eruptions, do the increasing CO2 levels in the ocean have any significant impact on the climate??
I don't know. I read Neven's blog regularly to try to keep up, but I don't think anyone there has mentioned what mechanism is responsible for the decline of the past couple of weeks. I would imagine that both are at work considering the steepness of the decline, but in what proportion I can't hazard a guess even.
Same old thing, one big, hairy furball after another. lol
THANKS!!
Hear ya. 9 more months to go.....
If the cooling was significant enough to cool the oceans, then the uptake of CO2 by the oceans would increase. That seems extremely unlikely to me, but I'm not an expert.
My guess is that there would be no discernible effect in the case of volcanoes whose effects diminish fairly rapidly. In the case of decreased solar activity, I suppose it would depend upon how long and how severe the decreased solar activity was. A long period of decreased solar activity might produce some noticeable effect, or not. Again, no expert = me. :^)
Speaking of ice, I wrote to the folks at the Arctic Climate Research unit at the University of Illinois (Cryosphere Today) to ask about the Arctic Sea ice area numbers that haven't been updated since the two-century drop on April 27 & 28; the tech who responded said that they're experiencing "server issues", and hope to have the problem resolved ASAP--perhaps within the next day or two.
Neven's blog is a fantastic resource. Sadly, however, as it has become ever more popular, denialist trolls have started to sniff their way in like the rats they are. To be expected, I suppose, but, still...
Oh, no! Someone forgot to make "."! Therefore, everything that person has ever said is now invalid.
Typos. They're how reality is decided.
Seriously? Silly denialists. Silly, desperate denialists...
(On another note, I had a nice online exchange with Michael Mann last week--in fact, on the same day that HuffPo comment was made. I tell you, Dr. Mann has more climate science knowledge and sense in his pinky fingernail than Watts, Goddard, and Bastardi have combined. Times ten.)
What do you believe the denialists will be saying when the arctic experiences it's first ice-free summer?? Probably about as likely as the Chicago Cubs winning the World Series in my lifetime (15 years...maybe 20)
It won't.. Just ask NOAA...........
The amount of solar energy received at the top of our atmosphere has followed its natural 11-year cycle of small ups and downs, but with no net increase. Over the same period, global temperature has risen markedly. This indicates that it is extremely unlikely that solar influence has been a significant driver of global temperature change over several decades.
From ScienceDaily:
New Research Brings Satellite Measurements and Global Climate Models Closer
One popular climate record that shows a slower atmospheric warming trend than other studies contains a data calibration problem, and when the problem is corrected the results fall in line with other records and climate models, according to a new University of Washington study.
The finding is important because it helps confirm that models that simulate global warming agree with observations, said Stephen Po-Chedley, a UW graduate student in atmospheric sciences who wrote the paper with Qiang Fu, a UW professor of atmospheric sciences.
They identified a problem with the satellite temperature record put together by the University of Alabama in Huntsville. Researchers there were the first to release such a record, in 1989, and it has often been cited by climate change skeptics to cast doubt on models that show the impact of greenhouse gases on global warming.
In their paper, appearing this month in the American Meteorological Society's Journal of Atmospheric and Oceanic Technology, Po-Chedley and Fu examined the record from the researchers in Alabama along with satellite temperature records that were subsequently developed by the National Oceanic and Atmospheric Administration and Remote Sensing Systems.
Scientists like Po-Chedley and Fu have been studying the three records because each comes to a different conclusion.
"There's been a debate for many, many years about the different results but we didn't know which had a problem," Fu said. "This discovery reduces uncertainty, which is very important."
When they applied their correction to the Alabama-Huntsville climate record for a UW-derived tropospheric temperature measurement, it effectively eliminated differences with the other studies.
Scientists already had noticed that there were issues with the way the Alabama researchers handled data from NOAA-9, one satellite that collected temperature data for a short time in the mid-1980s. But Po-Chedley and Fu are the first to offer a calculation related to the NOAA-9 data for adjusting the Alabama findings, said Kevin Trenberth, a distinguished senior scientist at the National Center for Atmospheric Research.
"It should therefore make for a better record, as long as UAH accepts it," he said.
To come up with the correction, Po-Chedley and Fu closely examined the way the three teams interpreted readings from NOAA-9 and compared it to data collected from weather balloons about the temperature of the troposphere.
They found that the Alabama research incorrectly factors in the changing temperature of the NOAA-9 satellite itself and devised a method to estimate the impact on the Alabama trend.
Like how a baker might use an oven thermometer to gauge the true temperature of an oven and then adjust the oven dial accordingly, the researchers must adjust the temperature data collected by the satellites.
That's because the calibration of the instruments used to measure Earth's temperature is different after the satellites are launched, and because the satellite readings are calibrated by the temperature of the satellite itself. The groups have each separately made their adjustments in part by comparing the satellite's data to that of other satellites in service at the same time.
Once Po-Chedley and Fu apply the correction, the Alabama-Huntsville record shows 0.21 F warming per decade in the tropics since 1979, instead of its previous finding of 0.13 F warming. Surface measurements show the temperature of Earth in the tropics has increased by about 0.21 F per decade.
The Remote Sensing Systems and NOAA reports continue to reflect warming of the troposphere that's close to the surface measurements, with warming of 0.26 F per decade and 0.33 F respectively.
The discrepancy among the records stems from challenges climate researchers face when using weather satellites to measure the temperature of the atmosphere. The records are a composite of over a dozen satellites launched since late 1978 that use microwaves to determine atmospheric temperature.
However, stitching together data collected by those satellites to discover how the climate has changed over time is a complicated matter. Other factors scientists must take into account include the satellite's drift over time and differences in the instruments used to measure atmospheric temperature on board each satellite.
The temperature reports look largely at the troposphere, which stretches from the surface of Earth to around 10 miles above it, where most weather occurs. Climate models show that this region of the atmosphere will warm considerably due to greenhouse gas emissions. In fact, scientists expect that in some areas, such as over the tropics, the troposphere will warm faster than the surface of Earth.
The paper does not resolve all the discrepancies among the records, and researchers will continue to look at ways to reconcile those conflicts.
"It will be interesting to see how these differences are resolved in the coming years," Po-Chedley said.
Source
Though deniers keep lying--
So logic-defying--
There's little denying
Our planet is frying.
In my experience, the response will probably be along the lines of "it's just a natural phenomena", and/or "the ice caps have melted in the past". It seems that every time I have this discussion with a denialist, they always have an answer. Whether or not their answer actually fits with the facts doesn't seem to matter to them.
Link
Came across these articles while reading a Peak-Oil website today. It is a sad commentary about America's educational and political systems that citizens of other nations seem to be much better informed about climate change than here in the U.S. Of course the 'Denialist' crowd is well funded by the petrochemical industry and extreme libertarian idealogues who don't understand that global problems can only be solved by collaboration and cooperation on a global scale!
Rising temperature to hit wheat production in India, says report
Link
Vietnam's climate woes ignite national strategy
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'We have seen the enemy': Bangladesh's war against climate change
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