The great thing about complex data is that one can basically come up with any number of headlines describing it – all of which can be literally true – but that give very different impressions. Thus we are sure that you will soon read that 2008 was warmer than any year in the 20th Century (with the exception of 1998), that is was the coolest year this century (starting from 2001), and that 7 or 8 of the 9 warmest years have occurred since 2000. There will undoubtedly also be a number of claims made that aren’t true; 2008 is not the coolest year this decade (that was 2000), global warming hasn’t ‘stopped’, CO2 continues to be a greenhouse gas, and such variability is indeed predicted by climate models. Today’s post is therefore dedicated to cutting through the hype and looking at the bigger picture.
As is usual, today marks the release of the ‘meteorological year’ averages for the surface temperature records (GISTEMP, HadCRU, NCDC). This time period runs from December last year through to the end of November this year and is so-called because of the fact that it is easier to dice into seasons than the calendar year. That is, the met year consists of the average of the DJF (winter), MAM (spring), JJA (summer) and SON (autumn) periods (using the standard shorthand for the month names). This makes a little more sense than including the JF from one winter and the D from another as you do in the calendar year calculation. But since the correlation between the D-N and J-D averages is very high (r=0.997), it makes little practical difference. Annual numbers are a little more useful than monthly anomalies for determining long term trends, but are still quite noisy.
The bottom line: In the GISTEMP, HadCRU and NCDC analyses D-N 2008 were at 0.43, 0.42 and 0.47ºC above the 1951-1980 baseline (respectively). In GISTEMP both October and November came in quite warm (0.58ºC), the former edging up slightly on last month’s estimate as more data came in. This puts 2008 at #9 (or #8) in the yearly rankings, but given the uncertainty in the estimates, the real ranking could be anywhere between #6 or #15. More robustly, the most recent 5-year averages are all significantly higher than any in the last century. The last decade is by far the warmest decade globally in the record. These big picture conclusions are the same if you look at any of the data sets, though the actual numbers are slightly different (relating principally to the data extrapolation – particularly in the Arctic).
So what to make of the latest year’s data? First off, we expect that there will be oscillations in the global mean temperature. No climate model has ever shown a year-on-year increase in temperatures because of the currently expected amount of global warming. A big factor in those oscillations is ENSO – whether there is a a warm El Niño event, or a cool La Niña event makes an appreciable difference in the global mean anomalies – about 0.1 to 0.2ºC for significant events. There was a significant La Niña at the beginning of this year (and that is fully included in the D-N annual mean), and that undoubtedly played a role in this year’s relative coolness. It’s worth pointing out that 2000 also had a similarly sized La Niña but was notably cooler than this last year.
While ENSO is one factor in the annual variability, it is not the only one. There are both other sources of internal variability and external forcings. The other internal variations can be a little difficult to characterise (it isn’t as simple as just a super-position of all the climate acronyms you ever heard of NAO+SAM+PDO+AMO+MJO etc.), but the external (natural) forcings are a little easier. The two main ones are volcanic variability and solar forcing. There have been no climatically significant volcanoes since 1991, and so that is not a factor. However, we are at a solar minimum. The impacts of the solar cycle on the surface temperature record are somewhat disputed, but it might be as large as 0.1ºC from solar min to solar max, with a lag of a year or two. Thus for 2008, one might expect a deviation below trend (the difference between mean solar and solar min, and expecting the impact to not yet be fully felt) of up to 0.05ºC. Not a very big signal, and not one that would shift the rankings significantly.
There were a number of rather overheated claims earlier this year that ‘all the global warming had been erased’ by the La Niña-related anomaly. This was always ridiculous, and now that most of that anomaly has passed, we aren’t holding our breath waiting for the ‘global warming is now back’ headlines from the same sources.
Taking a longer perspective, the 30 year mean trends aren’t greatly affected by a single year (GISTEMP: 1978-2007 0.17+/-0.04ºC/dec; 1979-2008 0.16+/-0.04 – OLS trends, annual data, 95% CI, no correction for auto-correlation; identical for HadCRU); they are still solidly upwards. The match of the Hansen et al 1988 scenario B projections are similarly little affected (GISTEMP 1984-2008 0.19+/-0.05 (LO-index) 0.22+/-0.07 (Met-station index); HansenB 1984-2008 0.25+/-0.05 ºC/dec) – the projections run slightly warmer as one would expect given the slightly greater (~10%) forcing in the projection then occurred in reality. This year’s data then don’t really change our expectations much.
Finally, as we’ve discussed before, what climate models did or did not predict is available for all to see. Despite many cautions about using short-term changes to imply something about the long-term trend, these comparisons will still be made. So just for fun, here is a comparison of the observations with the model projections from 1999 to 2008 using 1999 as a baseline. The answer might be surprising for some:
You can get slightly different pictures if you pick the start year differently, and so this isn’t something profound. Picking any single year as a starting point is somewhat subjective and causes the visual aspect to vary – looking at the trends is more robust. However, this figure does show that in models, as in data, some years will be above trend, and some will be below trend. Anyone who expresses shock at this is either naive or … well, you know.
As for the next few years, our expectations are not much changed. This coming winter is predicted to be ENSO neutral, so on that basis one would expect a warmer year next year than this year (though probably not quite record breaking). Barring any large volcanic eruption, I don’t see any reason for the decadal trends to depart much from the anticipated ~0.2ºC/decade.
Update: Just FYI, the same figure as above baselined to 1990, and 1979.
Reminder — quoting the nonsense, even to refute it, increases both the number of times search engines find it, and the likelihood that the uneduated reader will remember the nonsense.
Make a specific positive statement that differs — to be remembered — rather than a repetition of the mistake followed by some comment on it.
Falconsword says: …well, nothing very interesting.
Next!
Re Gavin’s in-line @142, that assumes birdtalk can even recognize that there is a real world.
138 Mark says, “And you are incorrect about how cancer forms. The cells don’t “remember” squat. The single cancer cell can metastasize and live dormant.”
Whether a cell metastasizes or not isn’t relevant to developing cancer, though it does affect survival rates.
Cancer often (always?) requires more than one mutation in a cell. So when smoking causes a large number of cells to acquire 1 or 2 of 3 mutations for cancer, then it becomes more likely for the ex-smoker to get cancer. On the other hand, the body does clean itself up, and after a number of years the risks for an ex-smoker drop. Besides, “remember” was in quotes – 2 of 3 mutations, fully mutated yet dormant, or damaged in some way that encourages future mutations (say damage to the cilia which help clear the lungs) – they all fit the term rather well.
142 Falcon claims, “most of the so called ‘climate scientists’ are being funded by government grants, and those grants are written by liberal politicians”
I didn’t know Bush and Co were ‘liberal’. James Hansen’s experience is quite different from what you describe. Are you postulating about the future, cuz if you are talking about the past, your comment is fanciful at best.
143 wayne says, “The true measure of temperature change is found with the entire troposphere”
I disagree. The true measure is found in the entire ocean/atmosphere system, with perhaps the top meter or three of land surface. Given the relative masses, that means ocean temp is all that really matters. The ‘at the surface’ measurement is used because it’s where we live. Anthro-bias.
Gavin and Matt,
The actual weekly discussion of ENSO at the same site says:
“Based on recent trends in the observations and some model forecasts, ENSO-neutral or La Niña conditions are equally likely through early 2009.”
Something I am sort of hazy about is why La Nina or El Nino would affect world temperatures so dramatically. After all, neither changes the basic solar input to the system. At most, they seem to redistribute the heat and shouldn’t be changing its absolute value.
Can anyone explain that?
[Response: They change both the cloud distribution and total water vapour in the system. – gavin]
Gavin: what is your response to the criticism of your graphs, by Lucia at the Blackboard?
[Response: I have no idea who she thinks she is arguing with. Since she never actually talks to me or asks for clarification, she persists in imagining interpretations of my thoughts that have very little to do with anything I actually think. If you think there are any substantial issues to be addressed, let me know. – gavin]
So, in other words, if we went into a period where La Nina dominated, then we would cool or not warm as fast? And, vice versa, in a period where El Nino dominated, we would warm faster?
Correct me if I’m wrong, but ENSO isn’t really well understood from a causality standpoint or long term predictability.
That’s not an answer, Gavin.
from her site:
That text seems plausible if we compare data to models using Gavin’s cherry picked baseline year of 1999. In contrast, if we use the slightly different (and equally cherry picked) baseline year of 1998, one would show that all but one out of 49 model runs lies above the trend.
[Response: But what is your point? (there are 55 runs in any case). I’m perfectly well aware that the start date is subjective – I said so above. I also said this was for ‘fun’ and it wasn’t anything ‘profound’ and that trends are a better thing to look at (but I did that months ago). What would you like me to add that I didn’t already acknowledge? I’ll also point out that 1998 is extreme cherry picking, 1999 not so much. If her point is to argue that short term comparisons aren’t particularly useful, I will gleefully agree. – gavin]
Her point was that with short term comparisons, with arbitrary start dates, you could pretty well get any result you want.
The chart at the top of this page, then, would also be representative of her point.
Thanks for agreeing.
[Response: Bingo! So that goes for starting in 2001 as well I suppose? – gavin]
Her point was that with short term comparisons; with arbitrary start dates, you could pretty well get any result you want.
The chart at the top of this page, then, would also be representative of her point.
2001, yes. Or 1998. Or 1999, for that matter.
Which, of course, is exactly what she’s done in the past with her “temps from 2001 prove IPCC projections wrong” baloney.
Jim Cross (157) — El Nino indicies exhibit a 3.6 year periodicity (and lots of ‘noise’ as well, of course). Still, this means that there is some slight predictably to ENSO. It is a subtopisc here:
http://tamino.wordpress.com/2008/11/12/co2-blip/
dhogaza: actually, IRC, she said that from 2001, measured temperatures vs IPCC projections fall outside the 95% confidence limits.
Which has just as much validity as Gavin’s chart above.
Actually, the year 1999 was more in line with global temperature trends than 1998 was.
As a little exercise, take 30 years of annual average global temperature data, put it into Excel and draw a liner trend graph.
For the years 1968 to 1998, the trend line is below the year 1998.
On the other hand, for the years 1969 to 1999, the trend line falls almost exactly on the value for 1999, at least using NCDC data.
Most impartial people should agree that 1998 was an anomoly and it would be wrong to use it as the starting point for future comparisons.
As for trends? Long term linear trends won’t show any rapid changes in a system, especially in long running systems, and especially if you go out to the start of the data.
If I plot and linear trend UAH data, and insert anomalies of 0.0, it takes until about 2025 until I see a flat trend.
I haven’t done it with GISS or Hadley data, but I suspect that I would need 100 years, or more, of 0.0 anomalies to get a flat trend, if I start the trend around 1900.
Do we need to wait 100 years? Nope. If Gavin is right, we will see a continued 0.2 deg/decade of warming, and the temps will come back inside the 95% levels. If Lucia is right, the measured temps will continue to fall outside of 95%.
I can wait.
#154 RichardC: “he true measure is found in the entire ocean/atmosphere system, with perhaps the top meter or three of land surface. Given the relative masses, that means ocean temp is all that really matters. The ‘at the surface’ measurement is used because it’s where we live. Anthro-bias.”
I am all for it! a planetary ocean/atmosphere temperature index would be nice, but I deal mainly with the atmosphere, which is warmed by the sun and ocean (sometimes cooled by the ocean). Studying just the atmosphere offers a clear focus .
Anthro-biased surface temperatures are flawed by its spacial randomness. It is not an easy straight world wide average, its taken where ever humans live, from below sea level to 3 to 4 thousand meters above. Its a mistake not to consider better averages. Humans live at the bottom of an ocean of air, global surface temperatures vary too much, and need be taken long term by necessity. A DWT is the best metric for temperature with respect to the atmosphere. The only other thing that comes close is IR down welling.
Gee, is it time to regurgitate the ‘AGW causing more hurricanes’ again? So soon?
Re: #127
Don’t forget that most of the warming is going into the oceans. That’s the essential reason why the long-term trend is robust – there will be many fluctuations in surface temperature, but the warming signal in the oceans is just as strong.
Can someone explain the exact mechanism for this process. OK I know the oceans are warmed by the sun, but I’m more interested in the amount of additional warming that has resulted from the reported increase of ~1.6 w/m2 due to GHGs since ~1850.
Rod, you _can_ digest new science. Chew. Ruminate.
> according to a NASA study released Friday….
> The space agency’s Jet Propulsion Laboratory (JPL) said
> a study by its scientists “found a strong correlation ….
> … released Friday.
Rod, it’s barely Saturday. You’re regurgitating prematurely.
Don’t stick your finder down your throat immediately.
Give your tender digestion time to assimilate the unfamiliar.
If you fwow up evewy time NASA posts a press release, you’ll never assimilate any actual information.
Reading the actual paper is sort of minimal competence to demonstrate before decrying the result. Check the work, see if you can find a problem with the correlation.
Rod,
There is a new result that has bearing here:
http://www.jpl.nasa.gov/news/news.cfm?release=2008-242
#164
According to the Wikipedia, recent El Niños have occurred in 1986-1987, 1991-1992, 1993, 1994, 1997-1998, 2002-2003, 2004-2005 and 2006-2007.
I suppose Tamino can look into his tea leaves of statistics and derive a 3.6 year cycle from that but I only see that it is something that happens every couple of years in a chaotic fashion.
Since ENSO does seem to drive global temperatures to a considerable degree (warm year 1998 was El Nino and this cooler year La Nina), it would be nice if it were understood more.
Gavin:
Sorry, try as I may, I remain a sceptic. I am curious, what would have to happen for you to stop believing the models are predictive? Seriously. These models output results so variable that there is hardly an outcome immaginable that does not fall within an acceptable range. If all outcomes are acceptable then in what sense have these models been proven or disproven? I applaude scientists for there efforts here but this simply tells me that climate is: a) a complex system which cannot be accurately predicted or b) climate prediction is still in its infancy and more research is needed. Either way, suggesting that this evidence is absolutely conclusive is just bizaar to me. For many this long ago stopped being science and has morphed into political activism.
There is a credibility gap a mile wide here [edit]
Bill H., Perhaps you would find the science more convincing if you understood it. Weather is noisy. It is chaotic. It cannot be predicted. However, if you look at long-term trends–e.g. 30 years or more–trends emergy. This is climate. One of the most prominent trends is the long-term warming.
What you are looking at in the graph is what happens when you use climate models to predict weather. You learn little from the spread of the models. Instead, look at the median or mean. That’s where you see the trend, especially in the 1979-2009 plot.
You ask what it would take to “falsify” the models. The answer: a better model. GCMs explain a broad range of climate phemonena–from long-term paleoclimatic trends to response to short-term perturbations like ENSO and volcanic eruptions. Any new model needs to do at least that well. The fact that all models imply anthropogenic warming means essentially that you can’t explain climate without AGW being a consequence.
Wyoming says:
snorbert zangox Says:
18 December 2008 at 4:23 PM
JW, Gavin,
The year 2000 was the last year of the 20th century. Think of it as 199ten. The first year of the 21st century was 2001.
Another way to look at it, since this is all religion based. Roughly speaking Christ was born on day zero (I know we use Dec 25 and others point out that it had to be in March some time, but in any case). Then the end of the first year of his life was his 1st birthday. YOur first year of life does not occur in year one, but in year zero. His 100th birthday was ..ta da! year 100. Big surprise. So…his 2000th birthday came after the last day of what year? Sort of seems to be the day after Dec 31st 1999 doesn’t it? So common sense being what it is…most folks think that the new century/millenium start on New Years day 2000. All things being equal I prefer pagan rituals. They are a lot more fun.
Gavin, you replied to someone:
“(MSU-TLT is a weighted average of temperatures reaching from the surface to 10km, peaking at around ~4km and with significant influence from surface type depending on elevation and polar latitude). Therefore comparing them with surface temperature anomalies from the models is not comparing like with like i.e. they are incommensurate. There are ways to create synthetic MSU data from the models, and I’ll discuss this in another post. – gavin]”
I look forward to a post on this. Wouldn’t it be more useful to use, instead of MSU-TLT, a measure at a single height?
[Response: You study climate with the diagnostics you have, not the ones you might want or wish to have at a later time. – gavin]
> remain a skeptic … stopped being science …
No, it’s continued to be science, which is informing political activity.
You’re confused about the outcomes; you misstate the facts then leap to the conclusion that what’s known now can’t be useful.
Politics is the art of getting moving _while_ trying to understand what’s happening, not just standing still watching trouble coming.
http://www.google.com/search?num=50&hl=en&newwindow=1&safe=off&hs=77O&q=%22climate+prediction%22+infancy+%22more+research+is+needed%22&btnG=Search
Rod reminds me of Homer Simpson: “Eggheads — what do they know?”
“Sorry, try as I may, I remain a sceptic.” – Bill H.
The rest of your comment indicates that you’re not trying to understand the science at all.
Jim Dunlap Says:
20 December 2008 at 10:51 AM
Another way to look at it, since this is all religion based. Roughly speaking Christ was born on day zero (I know we use Dec 25 and others point out that it had to be in March some time, but in any case).
The problem with that argument, which is the source of this whole issue, is that there was no year zero!
The first year was 1 so jan 1 xxx1 is the first year of the calendar decade, century, millennium. Decade is also used in the more general sense of ’10 years’
To Jim Cross #173: The fascinating factor here is that if NASA is correct and we have indeed crossed the threshold into a negative Pacific Decadal Oscillation, then we can expect more La Nina (cooling influences) vs. El Nino events (warming influences) in the coming few decades. Already, this decade has cool events outpacing warm events (with no strong El Nino events in ten years’ time).
Phil. Felton wrote: “The problem with that argument, which is the source of this whole issue, is that there was no year zero!”
Sure there was a year zero — the year before the Big Bang. And since time begins with the Big Bang — or more precisely, the concept of time cannot be applied beyond the Big Bang — the year zero may be regarded as infinitely long, or infinitesimally short, whichever you prefer.
Of course there is a year zero: the year preceeding year 1. Basic arithmetic, you know? Sure, certain religious “authorities” can’t (or couldn’t) wrap their minds around the concept, but is that reason for the rest of us to forever be enthralled by their mistake?
“…This coming winter is predicted to be ENSO neutral…”
No doubt I’m not the first to comment but the SOI looks anything but neutral these days.
Regards, BRK
Jumping on the 0 (no) bandwagon:
Golly, should this yearly wrangling be on the Mountains and Molehills thread?
The dominant numbering system goes straight from 1 BC to AD 1, but to be fair, I’ll wish an early Happy New Year to all, regardless of which decade it is, and when it might start!
Hank, Whew! Good! Thanks! I was just reacting to the headline in, and the post 158.
But then comes Ray to back it up ;-) … though he was referring to severe storms which at least has a teeny better correlation.
RE what year is this, anthropologists use “BCE” before the common era, and “CE” common era (replacing BC & AD) to make it somewhat more universal and secular. There are calendars for many civilizations, and we’d be in very different years on each of them, and the Mayan calendar is much more accurate than ours…which has leap years & even then is a bit inaccurate.
I’m thinking the big bang might be like absolute zero in temp (kelvin scale), and the different calendars of civilization like Fahrenheit and celsius scales, except that time is nothing like temperature or space, tho we use the space analogy to think about it (a point in time, a length of time…). We have to think of time in re to movements of astronomical bodies, esp the sun & moon. Apparently the Hopi had a better concept of time for physics, one detached from the space metaphor.
All I can say is we’re very late in seriously taking up the AGW issue, and time is of essence.
Which is quoting a new paper from JPL, which …
Ray kindly pointed you to.
And they’re claiming a *strong* correlation, not a “teensy better” correlation.
But, of course, it’s typical for denialists to handwave off research they don’t read.
Wait, at least let’s read the press release together, shall we?
The correlation (strong) described is between high clouds and sea surface temperature.
I think they’ll make the connection between sea surface temperature and storms in the paper.
It’s a press release. What do we know about press releases?
(Someone should study them, it’d be a good thesis topic …)
Actually they did it in the quote in the press release, that bit about a 6% decadal increase related to a 1.6C (or something like that, less than 2.0C) decadal increase in global temps.
Right or wrong, I can’t judge. But that’s how they allowed themselves to be quoted, and I would guess they didn’t say this if their paper contradicts it.
“Swiss glaciers in ‘full retreat'”
Don’t miss this further proof of the tragedy of AGW:
http://news.bbc.co.uk/2/hi/science/nature/7770472.stm
#192
PHE, did you read the article?
The decline began in 1860 and the glaciers lost mass even faster in the 1940’s.
Perhaps the most intriguing part of your post was this:
“However, we are at a solar minimum. The impacts of the solar cycle on the surface temperature record are somewhat disputed, but it might be as large as 0.1ºC from solar min to solar max, with a lag of a year or two.”
At least you see seem to concede that increases and decreases in solar magnetic output are capable of changing the average global temperature.
[Response: No. There is no compelling evidence that magnetic activity noticeably affects climate – gavin]
Svensmark has said that at solar minimum, cloud cover may increase by 3-4% over solar maximum.
[Response: He can say what he likes, it doesn’t make it true. Continuations of the data he used do not support any such change. – gavin]
The 20th century had the most magnetic sun of the last 1500 years and possibly the last 8000 years. So if Svensmark is correct (and his CLOUD project at CERN may prove that increased cosmic radiation from low solar magnetism increases cloud cover) then we have to be concerned about the impact that a number of continuous years of low solar magnetism would produce.
[Response: The long term trend is not certain, and equally convincing reconstructions (Mueschler etc) show similar solar activity in more recent times. Note the CLOUD is not Svensmark’s project (AFAIK he is no longer on the science team), and it’s impact on our understanding of solar impacts on climate in recent decades is going to be very close to zero (since, as I’m sure you know, there is no long term trend in GCR). – gavin]
Sunspots are indicative of the strength of solar magnetic output. During the 20th century we had the most sunspots we have had since sunspots were first noted and counted. But beginning in about 2002, the numbers of sunspots began to wane during solar cycle 23, far more so than generally predicted. This solar minimum is a very deep one, with solar cycle 24 yet to kick off and about a year and one half late already. 2008 was the most sunspotless year since 1913 with about 255 spotless days as of December 20. (The sun is spotless today).
The decrease in solar magnetism is now obvious with the solar wind the lowest since the space age began.
Also others have noted that decreased solar magnetic output also decreases solar UV which heats up the atmosphere and expands the ionosphere, increasing the ionosphere’s height. Right now, the low magnetic solar output has shrunk the ionosphere to its lowest levels since the beginning of the space age.
Livingston and Penn in 2005 predicted that based upon the observed decline in solar magnetic output that by 2014 or 2015 the sun’s magnetic output will have dwindled to the point where the sun produces no sunspots. Others have noted that when the sun goes into these magnetic funks, these periods last from between 30-70 years.
So the question is, what happens to the earth if many successive years of 0.1C degree negative anomalies occur?
[Response: Think about your question again (the answer is contained within it). – gavin]
Do you think we get to a point where the earth cools by 1C degree, and if so, how long would it take?
Gavin, Where can I find a list of the data collection points for the data used to calculate the earth’s surface temperatures? And other information about the gathering of the data?
[Response: The sources for GISTEMP are described and linked to on their website. Most data comes from GHCN (details at NOAA’s website). – gavin]
Aside for the “we can’t go photograph the satellite so how do we know it’s giving accurate information” question: calibration:
http://spiedl.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PSISDG00708100000170811B000001&idtype=cvips&gifs=yes
Absolute radiometric calibration accuracy of the Atmospheric Infrared Sounder (AIRS)
Proc. SPIE, Vol. 7081, 70811B (2008); DOI:10.1117/12.795445
Online Publication Date: 20 August 2008
—-excerpt—-
… AIRS has demonstrated in-flight NIST traceability and high radiometric accuracy. This accuracy is achieved in orbit by transferring the calibration from a Large Area Blackbody (LABB) to the On-Board Calibrator (OBC) blackbody during preflight testing. The LABB theoretical emissivity is in excess of 0.9999 and temperature uncertainty is less than 30 mK. The LABB emitted radiance is NIST traceable through precision Platinum Resistance Thermometers (PRTs) located on the internal surfaces. The radiometric accuracy predictions for AIRS based on the OBC, LABB, and pre-flight measurements give an accuracy of 0.2K, 3 sigma. AIRS pre-flight calibration coefficients have not changed in flight, preserving the link between observations and pre-flight calibration and characterization. An update is being considered that will improve accuracy and preserve traceability. …
—-end excerpt—–
Well placed reference Hank, there is a lot of recent data from AIRS and some other sources.
@194 [davidgmills]
“Svensmark has said that at solar minimum, cloud cover may increase by 3-4% over solar maximum.”
He can “say” whatever he likes, there is virtually no evidence to support the claim, and quite a bit that rejects it.
(ReCaptcha: “head Tragedy”)
#194 Gavin
I’ve heard this many times about no long term trends in GCR and more or less accepted. But what about this?
http://en.wikipedia.org/wiki/File:Solar_Activity_Proxies.png
The Be10 which is a proxy for GCR clearly looks to have a trend of reduced GCR for more than the last 100 years.
[Response: It all depends on where you measure it. At Dye3 in Greenland, there is a trend, but there isn’t in the data from the South Pole. Trends in recent decades in both cases do not come out of the noise. Plus, you have the problem in knowing how to calibrate a Be10 concentration to solar activity. There is little reason to prefer 10Be over the last 50 years over the continuous measurements from the cosmic ray monitoring instruments (ie. CLIMAX Neutron Monitor) and these show no trend. – gavin]
RE: My post at 194 and your responses:
My post: Svensmark has said that at solar minimum, cloud cover may increase by 3-4% over solar maximum.
[Your Response: He can say what he likes, it doesn’t make it true. Continuations of the data he used do not support any such change. – gavin]
First thanks for the response.
I think there is more than a sufficient basis to conclude that
Svensmark could be right with his estimations and I am aware of papers that critique his work. I am also aware of papers that support it.
Most notably I would refer you to Jasper Kirkby’s recent paper on what the CLOUD project is about. (Kirkby is the director of the CLOUD project). If you have read the article already or know about Jasper Kirkby, no condescension is intended.
Here’s the link:
http://arxiv.org/PS_cache/arxiv/pdf/0804/0804.1938v1.pdf
Since it is a pdf, I can not cut and paste so I have handwritten a few quotes from his conclusion which I will quote here:
“Numerous paleoclimatic observations, covering a wide range of time scales, suggest that galactic cosmic ray variability is associated with climate change…. The satellite data suggest that decreased GCR flux is associated with decreased low altitude clouds, which are known to exert globally a net radiative effect…. The question of whether, and to what extent, the climate is influenced by cosmic ray variability remains central to our understanding of the anthropogenic contribution to present climate change.”
This is a thirty eight page paper with about 175 footnotes (Svensmark is footnoted four or five times) that describes in detail why Kirkby thinks this project is warranted. He goes into great detail about the correlation between cosmic radiation and climate not only for the last millennium, but for three other time periods dating all the way back to 550 million years ago.
He also details the ways in which cosmic radiation could effect climate and supports this with his numerous references.
What concerns me is that climatologists see no need to wait to see if there is any correlation between the magnetic output of the sun and climate change. Kirkby clearly thinks this research is “central to our understanding of the anthropogenic contribution to present climate change.”
If it is central, why not do the research to see how central? Why not wait for the results? They may be surprising. I think Kirkby expects them to be significant. Why? His review of the cosmic radiation correlation with climate for the last 550 million years.
I think Kirkby believes the CLOUD project will show, (as Svensmark’s pilot project SKY has already tentatively indicated), that cosmic radiation is able to seed low clouds in quantities sufficient enough to effect significant climate change.
[Response: It is often the case that a PI for a project thinks it is ‘central’ to understanding some big problem. I might go as far as to suggest it’s almost universal. However, it can’t be universally true. The existing data, and the lack of a GCR trend in recent decades already imply that whatever comes out of CLOUD, it’s role in attributing recent trends will be negligible, and the impact on future projections negligible. It may improve our understanding of solar cycle effects, or for the impacts of long term solar in the past. But the indications are not good (i.e. no correlations of climate change to the Laschamp excursion or the B-M magnetic reversal etc.). Understanding ionization impacts on aerosols is important, but it is not the game-changing study you (and possibly Kirkby) are anticipating. – gavin]