This is just one of dozens of responses to common climate change denial arguments, which can all be found at How to Talk to a Climate Sceptic.
Objection:
Global temperatures have been trending down since 1998. Global Warming is over.
Answer:
At the time, 1998 was a record high year in both the CRU and the NASA GISS analysis. In fact, it was not just a record year, it blew away the previous record by .2oC. (That previous record went all the way back to 1997, by the way!) According to NASA, it was elevated far above the trend line because 1998 was the year of the strongest El Nino of the century. Choosing that year as a starting point is a classic cherry pick and demonstrates why it is necessary to remove the very chaotic year to year variability that exists (aka: weather) by smoothing out the data. Looking at the CRU's graph below, you can see the result of that smoothing in black.
Clearly 1998 is an anomaly and the trend has not reversed. (Even the apparent levelling at the end is not the real smoothing. The smoothed trend in 2005 depends on all of its surrounding years, including a few years still in the future.) By the way, choosing the CRU analysis is also a cherry pick because NASA has 2005 breaking the 1998 record, though by very little.
Now this is an excusable mistake for average folks who do not need the rigors of statistical analysis in their day jobs, but any scientist in pretty much any field knows that you can not extract any meaningful information about trends in noisy data from single-year end points. This is why it is hard to hear a scientist make this argument and still believe that they are a voice of integrity in this debate, rather it appears more to be an abuse of the trust people would like to place in them as scientists. Bob Carter is such a voice and was the first to trot out this argument in an article in the Daily Telegraph. Since then it has echoed far and wide and has been used by Richard Lindzen as well as a host of sceptic websites.
Interestingly, Bob Carter seems to know what he is doing as he tries to pre-empt objections in his article by basically insinuating that any choice of starting point, (such as 1978), will just be a cherry pick with the opposite motive! But cherry picking is about choosing data for the sole purpose of supporting a pre-conceived conclusion, it is not the simple act of choosing at all, as one must choose some starting point. In the case of his example year, 1978, this is often chosen simply because it is the first year that satellite records of tropospheric temperatures were available.
So what choices are there, what are the reasons for those choices and what are the conclusions we can draw from them?
- As just mentioned above, one could chose to examine the last 30 years because that is the period of time where both surface and tropospheric readings were available. We have been experiencing warming of approximately .2oC/decade during this time. It would take a couple of decades trending down before we could say the recent warming did in fact end in 1998.
- You could choose 1970 in the NASA GISS analysis as this was the start of the late 20th century warming and as such it is a significant feature of the temperature record. The surface temperature over this period shows .6oC warming.
- You could choose 1965 in the CRU analysis as this is when the recent warming started in their record. This record shows around .5oC warming of the smoothed trend line.
- You could choose 1880 in the NASA record. This shows .8oC warming.
- You could choose 1855 in the CRU record. This shows .8oC warming. Again, with this trend and the above we can not say it is over without many decades more data all indicating cooling.
- You could choose to look at the last 500 years in the bore hole record analysis because that is its entire length. This puts today about 1oC above the temperatures in the first 3 centuries of that record. The record of today's trend in that kind of analysis will be hidden from view for many more decades.
- You could choose to look at the last one thousand years, because that is as far back as the dendrochronology studies reliably go. Then the conclusion is:
Although each of the temperature reconstructions are different (due to differing calibration methods and data used), they all show some similar patterns of temperature change over the last several centuries. Most striking is the fact that each record reveals that the 20th century is the warmest of the entire record, and that warming was most dramatic after 1920.
- You could choose to look at the entire period of time since the end of the last ice age, around 10kyrs ago. Then the conclusion is that GHG warming has reversed a very long and stable period with a very slight downward trend and we are now at a global temperature not experienced in the history of human civilisation, the entire Holocene. Such a long view applied to today will take many centuries to clear up. The situation is a bit more urgent than that!
I think that about covers any periods of time relevant to today's society. Clearly, "it has stopped warming" is only supported by taking a single specific year out of context and using a 7 year window to look at multi-decadal trends in climate. That is a classic cherry pick.
This is just one of dozens of responses to common climate change denial arguments, which can all be found at How to Talk to a Climate Sceptic.
"Warming Stopped in 1998" was first published here, where you can still find the original comment thread. This updated version is also posted on the Grist website, where additional comments can be found, though the author, Coby Beck, does not monitor or respond there.
Environment
Politics
Comments
No,"stopped warming" means just that.2001 or 2002 is when it stopped warming and 2007 and 2008 in particular show a strong fall.We are now back to the same temperature as around 1980.AGW predicts that as the co2 level rises temperature will rise.This has not happened since 2002,which suggests that co2 is not a primary driver of climate.
Posted by: Tim Wells | August 19, 2008 6:24 AM
Hi Tim,
How about some kind of data to back up your wild claims? Please provide a temperature record showing 2007 or 2008 at the same level as 1980.
Thanks.
Posted by: coby | August 19, 2008 11:11 AM
Coby
Here is a copy of the UAH (University of Alabama, Huntsville) Microwave Sounder Unit (MSU) - it ends in July (can't find the August one sorry)
http://wattsupwiththat.files.wordpress.com/2008/08/uah_july_08.png
This shows that the anomaly for 1980 is higher than the current 2008. Would this count as evidence for Tims wild claims?
Posted by: Chris,Baildon | August 21, 2008 9:26 AM
Hi Chris,
Thanks for presenting something concrete. I guess I should have been more precise and specified seasonally averaged global temperatures, monthly fluctuations are too chaotic. But just eyeballing your graph (I'm sure I could google it, and am not doubting its veracity, but it is always nice to have the source handy for detail and explanation) it is clear that 2007 is not below 1980 and 2008 is not over yet. So strictly speaking Tim's claim is still incorrect even if we ignore all of the other temperature records available.
But let me ask you this: what would it mean if a single year did drop below 1980? There is very large inter-annual variability even in globally and seasonally averaged temperatures, these changes are really part of weather. Climate trends require a lot of time to determine. This is why the IPCC took until the late nineties to finally say "yes, the climate is warming" when looking back on the CRU graph above one might be tempted to say it was obvious in the early 80's.
I remember very well and not too long ago, sceptical voices saying it was too soon to say the climate was really warming even after the IPCC decided it was clear. Now these same voices are all too happy to seize on a mere 8 years to decide we are cooling! I have great difficulty believing the sincerity of such arguments. That said, I have no idea where you are coming from in all this and do not wish this digression to reflect on you personally!
Thanks for the comment.
Posted by: coby | August 21, 2008 9:51 AM
The point of the discussion Coby was that warming stopped around 2002,and that 2007 and 2008 have seen a sharp fall in temperatures.According AGW theory the 5% increase in CO2 over the last decade should have resulted in more warming-it has not!What it does show is another example of the LACK of correlation between CO2 and temperature.Please present some clear evidence that CO2 has caused the current warm period.
[Tim, there is no point conversing with you if you simply ignore everything put in front of you, it is in the article above: a 10 year trend is more influenced by weather than climate change. There are other guide entries about the strength of the correlation over this century. Please remember there are other influences, no one claims CO2 is the only factor. Look at the CRU graph, the trend has leveled off recently but there has been long term cessation or reversal yet.]
Posted by: Tim Wells | August 22, 2008 1:44 AM
Hi Coby - I'm happy to have reasonable arguments on any topic ;-)
I agree with you that 8 years is not long enough for a long term climate trends - although it is intriguing. In the same argument is the 20 odd years of warming since the late 1970's long enough? - when I believe CO2 was supposed to overcome the natural variability in the worlds climate.
[Even 20 years is not long enough to be unequivocal. We do have, however, a 100 year long record to analyse.]
I'm happy to admit the world has warmed slightly in the last 100 years. Increased CO2 in the atmosphere may well have something to do with it. Were I tend to start getting very sceptical is the "tipping point", "we've got 10 years to save the world", etc type scenarios. There always seems to be a "10 years to save the world" disaster about to happen.
[I can't disagree that 10 years to act is a little arbitrary. I would say to be safe we should move as quickly as possible.]
I'm happy to try and improve the environment and use more efficient things (its saves me money after all). What I'm not too keen on is destroying the world economy because some computer models foretell disaster - which would happen if we went back to the under 300 ppm on C02 - as Dr Hansen wants.
[I think "destroy the world economy" is a tad alarmist, no? : )]
I do not see how blaming the worlds climate woes on one politically amenable constituent (i.e. CO2) when the climate has thousands of variables (many unknown), is chaotic and does seem to have changed rather alot over the past centuries, will really make the world a better place.
[But this is not at all a fair characterization of the scientific reality of our situation. Plus CO2 is hardly a politically convenient target, we all produce it in almost every economic activity and the biggest corporate and political powers are very heavily involved in the oil industry. No one decided first to target CO2 and second to build a fraudulent case against it.]
Happy to be put right on any points - I'm just an interested layman.
By the way if the Jevons paradox stays true -- this drive for energy efficiency may have unforeseen consequences.
[Maybe it will make us a happier and cleaner society ;-)]
Posted by: Chris,Baildon | August 22, 2008 9:06 AM
Coby,you start off by sayin g that there is no use conversing with me because of.......
Well,if you could show me the evidence that CO2 has caused our recent warming,I would be happy.I will repeat;there is no meaningful correlation between CO2 and temperature over any significant timescale.Please present your evidence!By the way,by admitting that "weather" or "aerosol pollution" can override the effect of CO2 you are simply confirming the fact that CO2 does indeed have a negligible effect on climate.Do you realise that?It is another way of saying that CO2 is NOT the primary driver of climate.
Posted by: Tim Wells | August 24, 2008 11:46 PM
Tim Wells wrote:"Please present some clear evidence that CO2 has caused the current warm period,"
Coby replied:"Tim,there is no point conversing with you if you ignore everything put in front of you,it is in the article above."
Is it?Are you sure? Not only is there not any evidence about CO2 in that article,CO2 is not even mentioned ONCE!!
Posted by: Tim Wells | August 25, 2008 12:03 AM
Tim,
It is a little confusing that you are making cross thread references in your comments. Please read the IPCC AR4, at least the summary for policy makers, all the evidence is there. If you don't trust that summary, follow up with the references in there in the primary literature. I also highly recomment Spencer Weart's "History of Global Warming".
by admitting that "weather" or "aerosol pollution" can override the effect of CO2 you are simply confirming the fact that CO2 does indeed have a negligible effect on climate.
No, it only means there are other factors that can dominate on short timescales. Volcanic erruptions are another. CO2 clearly dominates on multi-decadal timescales this last 100 years or so. It is not an either-or, all or nothing proposition at all, but rather a complex interaction of many factors, CO2 being just one, albeit a very important one.
Posted by: coby | August 25, 2008 12:35 PM
Well I keep on asking but it is obvious that you can't present any evidence.AR4 does not have it either,and I challenge you to post it here from the SPM.
"CO2 clearly dominates on multi-decada timescales.."
No it does not!We had global COOLING from 1940 to 1976 during the greatest period of economic expansion in history.That is almost FOUR decades,and CO2 did NOT drive up temperatures.And just to pre-empt you.....if you are thinking of saying that this cooling was caused by aerosols,then that simmply demonstrates that CO2 does not have a strong temperature signature,and it's effect is negiligble.[which is what the science says!]In any case the aerosol theory is wrong.If the aerosols caused cooling then it should have had more effect[ie more cooling]in the northern hemisphere.It did not,as there was more cooling in the SOUTHERN hemisphere.Once again real world observations just dont match the theory!
Posted by: TimWells | August 27, 2008 4:18 AM
the odd thing is - if you disregard all the text and just look at the top graph is *does* seem to look like warming has stopped, doesn't it?
Posted by: botogol | August 28, 2008 4:45 AM
Funny, now that you mention it, botogol, no, it doesn't look like that at all.
Posted by: Douglas Barnes | August 30, 2008 11:41 AM
Tim,
It did cool more in the NH than the SH mid 20th century. So by your own admission this is good evidence that the aerosol theory is correct.
http://data.giss.nasa.gov/gistemp/graphs/Fig.B.lrg.gif
And I just have to point out that aerosols temporarily dominating CO2 forcing does not imply CO2 forcing is insignificant, just that there are other factors and they need to all be assessed. They have been and over the last 100 years CO2 is the largest single factor.
http://www.grida.no/climate/ipcc_tar/wg1/figspm-3.htm
Posted by: coby | September 5, 2008 11:52 AM
Coby once again these graphs are from James Hanson and have been shown by McIntyre to be doctored.There is a full expose about it on Climate Audit.
Posted by: tim wells | September 19, 2008 1:45 AM
Tim, the graph is from the Hadley center, which is unaffiliated with Hansen. He had nothing to do with that graph.
If you can't tell the difference between Hadley and GISS, how can you claim to be informed here?
Posted by: Brian D | September 19, 2008 10:37 AM
Brian, he's talking about the links I provide just above. Not that it makes a difference to the argument, but here then is the same comparison from CRU:
http://www.cru.uea.ac.uk/cru/data/temperature/nhshgl.gif
For the 50's, 60's and 70's the NH trend was down, while the SH trend was up. This is consistent with the explanation that NH air pollution caused cooling until 70's pollution controls came into effect.
ClimateAudit has shown no such thing about Hansen, though they did helpfully uncover an error that changed nothing fundamental about the record.
Posted by: coby | September 19, 2008 4:35 PM
Tim Wells: No Tim, your argument is a strawman type argument and as Coby asserts a classic cherry picking of data. Indeed, while I haven't done the analysis, I'm fairly certain given the yearly variation present in the climate record that the past 8 years would not represent a deviation in a statistically meaningful sense from the preceding warming.
Moreover your argument is irrelevant because you point to global temperature anomalies since 1998 remaining constant or falling slightly, point to C02 rising and then suggest it somehow refutes the theory. It does no such thing.
the theory for AGW does NOT assert that climate is ONLY driven by GHGs, it asserts that GHGs are having an impact on climate and is resulting is warming. That doesn't mean that the numerous other variables that are part of the climate play no part, they do, yet you focus on only ONE variable, infer some sort of linear relationship between the two, instead of a complex one with feedbacks, and then erroneously claim this refutes AGW. It's absurd and shows a profound ignorance of climate science and modeling.
Posted by: shoegazer | November 2, 2008 9:09 AM
Shoegazer,I did not suggest that the AGW theory is 'refuted' by that last 8 years of stasis/falling temps.I said it suggests that CO2 is not a primary driver of climate.If AGW theory is right and CO2 is responsible for 'most' of the temperature rise,then what has caused the stasis/falling in temperatures since 2001,while CO2 has continued to go up??This observational evidence is not consistent with the theory.Something has apparently turned off the CO2 'warming driver'.If you have an explanation I am all ears.
"you focus on only ONE variable..." NO,rather I focus on ONE CLAIM!!That claim is that CO2 has produced most of the warming,and so far the evidence supporting that claim is both sparse and inconsistent.
Posted by: timwells | November 3, 2008 6:06 AM
Coby thank-you for providing the temp graphs from CRU.Even the breifest of glances confirms my original assertion-that is that there should have been more cooling in the northern hemisphere,and there was not.Temps dropped faster AND farther in the Southern Hemisphere from 1940.The aerosol theory is supposed to produce the opposite!!If the aerosols were to produce cooling,then why didn't the greater[and more rapid]cooling happen in the Northern Hemisphere?This also strongly suggests that the cooling was not produced by the aerosols which,by your own admission,were mainly a NH phenomenom.As such,I fail to see how these graphs support the aerosol theory as you state it.
Posted by: timwells | November 3, 2008 7:09 AM
So shoegazer, if I understand correctly, when the temps go up between late 1970s and late 1990s, it is just as clear as day, and not even worth discussion, that this was due to human CO2. But when they level off not for an insignificant amount of time but for half the length of the "preceding warming", something unlikely given the model predictions, suddenly things are very complicated and to even request an explanation of this behaviour is to be ignorant of science and modelling.
Posted by: paul | November 3, 2008 11:30 AM
Tim Wells: Tim NO ONE has suggested GHGs were the ONLy driver or even the primary driver of warming.In fact I would venture if you asked any climate scientist the PRIMARY driver of climate is the SUN.
The AGW theory is that GHGs are causing warming that would not have occurred due to natural factors alone and that that contribution is resulting in warming, which poses a danger to the planet as it exists today.
Thus Tim since there are numerous variables that impact climate, it is entirely consistent with the theory and modeling to have GHGs increase but temperatures not increase and the reason is that changes in the other variables have likely occured. Now IF GHGs increase ceritus paribus - all other variables remain the same - then this could suggest some dynamic or variables not being accounted for, which warrants further investigation.
There are variables, such as many of the aerosol forcings that exist, which act in a cooling manner on climate. It's entirely possible that there factors are contributing more.
Actually Tim the evidence isn't sparse at all. The current state of the art models of climate demonstrate quite clearly that the warming observed during the 20th century can only be explained by the inclusion of GHGs. That doesn't mean GHGs are the primary driver of climate, it means they are contributing to excess warming.
Posted by: shoegazer | November 8, 2008 6:17 PM
Lots of wonderful sounding theory Shoegazer,but not a lot of facts to back it up.
Firstly,you are incorrect about the claims of CO2 being the primary driver.The IPCC says that "the majority of warming is very likely due to human activities".In other words,CO2 is the primary driver of the recent warming.
You actually state the same thing in your second paragraph above,so I fail to see what you are arguing about.
The rest of your post is just about theory and modeling as opposed to real evidence.If temperatures dont rise when there is an increase in CO2,then it is because of "other variables",not because the theory is flawed.So as such,what "other variable" has caused the stasis/cooling since 2001?Let me guess-you dont know!Infact you have written it with your own words.Here they are.
"...have likely occured."
"...this could suggest.."
"Its entirely possible.."
In science Shoegazer,you have to do better than that.
Also you seem to have the same problem that some other people have on this site in regards to what constitutes "evidence"."The current state of the art models..." are NOT evidence my friend-they are just more theory!Evidence is real world data-try to understand that.
Now you finish by claiming that "GHG's....they are contributing to excess warming." So exactly how much is this "excess warming" that you speak of?
Posted by: timwells | November 10, 2008 4:59 AM
Tim Wells: Well thank you Tim, now have you not only demonstrated your lack of understanding of the science, you've brought into question your ability at reading comprehension.
I said that the primary driver of climate is the sun. Anyone who disagrees with that statement is either woefully ignorant or an idiot and I say that with about as much due respect as any such person would deserve.
The AGW theory does not say that C02 is the primary driver of climate, nor the only driver, which is why there are numerous variables that (are included in) affect the climate (models) including but not limited to: insolation, water vapour, clouds, volcanic activity, earth's axial tilt, precession, obliquity, aerosol compounds such as dust, sulphates, soot, etc. all contribute to global climate as does the earth's albedo.
CO2 is seen as the primary driver of recent warming above what one might expect from the natural parameters driving climate, not of climate overall. This has been demonstrated through models of climate where excess C02 buildup beyond the natural C02 cycle is included or excluded. Again only a facile level of understanding of the theory could allow one to conclude as you have that it implies C02 is the primary driver of climate. AGW theory says that ceritus paribus, manmade C02 increases are warming the planet on average over time. That doesn't mean the average temperature has to respond as a smooth linear response variable to C02.
Tim I have 4 degrees in science and engineering the highest being a doctorate. I'm also extremely well versed in the history and philosophy of science from Aristotle to Hume and onto Popper, so please don't tell me how science works.
All of science, every field is built on models. Einstein's theory of relativity is a model, as are quantum mechanics, as are fluid mechanics, electromagnetism represented by Maxwells equations, etc.
No Tim, I said that YOU make the error by assuming that if CO2 increases but global average temperature does not then the AGW theory has been refute. It does NO SUCH THING, such a belief represents an incredibly facile understanding of the science. NO ONE is claiming that global average temperature is positively linearly proportional to C02 and ONLY C02 which is the only way your assertion could be correct. There are numerous other variables. I used the words "could" because I haven't looked at every single other data set to see if there are other input factors that could explain the "cooling", but then neither have you since you discount them entirely.
Data is JUST data Tim. It can suggest a model of nature which develops into a theory or it can falsify a theory if the predictions made by the theory don't materialise. The latter has not occurred here. But it is the model, the theory that describes how nature works or how we believe it to work. Data is fine Tim but science relies on models of nature in virtual every field of scientific endeavour and engineers rely on them as well to design processes and products using our understanding of the theory/model of how nature operates.
Posted by: shoegazer | November 19, 2008 2:18 AM
Shoegazer – you said
"I said that the primary driver of climate is the sun. Anyone who disagrees with that statement is either woefully ignorant or an idiot"
"CO2 is seen as the primary driver of recent warming"
"Again only a facile level of understanding of the theory could allow one to conclude as you have that it implies C02 is the primary driver of climate."
So, you seem to be either admitting that you are an idiot (though of course anyone with 4 degrees, who knows the highly relevant works of Aristotle and who uses phrases like “ceritus paribus” could not possibly be so) or saying that there is a difference between "recent warming" and "climate". Could you explain what this is with clear English and numbers/timescales? That is, what is “climate”? When does the “recent warming” refer to? And how could something be driving "climate" but not be responsible for the recent warming, and vice versa?
You also say about “data” that “It can suggest a model of nature which develops into a theory or it can falsify a theory if the predictions made by the theory don't materialise. The latter has not occurred here.” and you also say “NO ONE is claiming that global average temperature is positively linearly proportional to C02”.
In order to falsify a model with observational data, it has to make some predictions. As you are clear that AGW theory does not predict that temperatures will rise linearly as CO2 does, what exactly does it predict and how could it be falsified by observations?
Posted by: paul | November 20, 2008 3:37 AM