Could global warminmg be a natural cycle?

Question

Here's the 10 year moving average temps...

2007 - 14.607°C
1997 - 14.481°C
1987 - 14.274°C
1982 - 14.182°C
1977 - 14.093°C
1967 - 13.987°C
1957 - 13.976°C

In the last 50 years temps have increased by 0.631°C and by 0.426°C in the last 25 years. Could this be a natural cycle and if so when did temps last increase at this sort of rate?

Source: NASA/GISS, Global Historical Climate Network GISTemp global mean monthly data..

Notes: Met station reports, derived from anomalies from 1951 to 80 base period using absolute base mean of 14°C, outliers eliminated, homogeneity adjusted.

Forgot to include the link to the data source - http://data.giss.nasa.gov/gistemp/tabledata/GLB.Ts.txt

I'll add comments as and when time permits...

SUZETTE: Thanks, I wouldn't personally recommend An Inconvenient Truth. It's pretty accurate although there are some errors but it's all very one sided.

CHUCK: Spot on, no records from more than a few hundred years ago at best (1659 are the earliest ones). However, it is possible using numerous techniques to accurately reconstruct temps for the last 850,000 years and pretty accurately for the last 542 million years.

MR JELLO: Welcome back. The data isn't cherry picked. I used the figures from 0, 10, 20, 30, 40 and 50 years ago and the temps from 25 and 50 years ago. If it were cherry picked there would be no consistency on the numbers.

It was warmer in the 30's and 40's than in the 50's and 60's but the last 35 consecutive years have been warmer than at any time in the 30's or 40's. If I've cherry picked the years then why don't you provide a list of years and compare the temps to 2007 (and you can cherry pick your years as much as you like).

GABY: Be careful with CO2science.org - check out who's behind it. You're right that GW is a natural cycle but what no one (so far) has done is to answer my question about when temps last rose as fast as they are now. It was a rhetorical question, the answer is they've never risen this fast. We know why they're rising so fast now - increased atmospheric greenhous gas concentrations.

LODE RUNNER: Movies - fun to watch but not the most reliable source for science.

SOME YANK: The figures are 10 year moving averages, each one being an average of 21 years (except 2007 which is an average of 11). They cover the range 1947 to 2007. Chosing any similar data points shows almost exactly the same trend. I've now added the link to the full dataset.

VLADOVIKING: The significant thing isn't 'one degree' but 'one degree in such a short space of time' (current average is one degree in 56 years). Had temps risen at this rate during the end of the last glacial advance (often called the end of the last ice age) then temps at that time would have risen by 133°C (239°F).

LISTON: Very good points. The 'mini ice age cycle' is one of approx 100,000 years, the current natural warming trend began 18,000 years ago with the glacial retreat at which point temps rose by 7°C in 7,500 years then a further 1°C in the next 10,000 years and a final 1°C in recent decades.

Long term climate is difficult to predict, when you look at predictions they aren't specific because of this, instead they give a range of 'between X and Y'.

BIG JON: The instrumental temp record is comparatively recent but the reconstructed temp record goes back millions of years. We can't say exactly what temps were back then but within the last million years we can to an accuracy of about 0.1°C, that gives us a pretty good record from which to work. What's most significant is how much faster temps are now rising.

BIBSIAN: Urban myth that grapes were grown on the Scotland / England border - there's not much grows there are all, it's primarily upland sheep farming (I live pretty close by). About 1000 years ago grapes were grown in southern England, today they're grown as far north as Carnforth in Lancashire, Leeds in West Yorkshire and at Bolton, Ryeland and Helmesley all in North Yorkshire, all these are in the north of England meaning grapes are now grown further north in the UK than ever before.

There was a case brought before the High Court in London to have An Inconveneint Truth banned from being shown in British schools. Mr Justice Burton refused to ban the movie stating that the movie was "substantially founded upon scientific research" and that "global warming is mostly due to man, is dangerous, can be fixed by man [and] are all supported by a vast quantity of research" Here's the full High Court ruling http://www.bailii.org/ew/cases/EWHC/Admin/2007/2288.html

AMIRAM: Indeed, there are global warming (and cooling) cycles and every so often we have an 'ice age' at approx 100,000 year intervals.

TOMCAT: Ave global temp in 1910 was 13.768°C, in 1942 it was 14.026°C, an increase in 32 years of 0.258°C, the same rise has occurred in half the time from 1991 (14.346°C) to 2007 (14.607°C). Much of this rise was attributable to sunspot activity but by bringing this up you're shooting yourself in the foot because by studying the relationship between sunspot activity and temperatures it is apparent that there is a dramatic divergence in recent decades with temps rising and sunspot activity falling - http://solar-center.stanford.edu/sun-on-earth/600px-Temp-sunspot-co2.svg.png

Sunspot activity in 1942 was approx the same as it is now, following your train of thought then temps should also be the same, quite clearly they're not.

Positive feedbacks: The approx duration of reduction / expansion of sea ice coverage is directly (and inversely) proportional to the cumulative difference between atmospheric and ocean temps, the positive feedback from reduced sea ice coverage has long since been negated. Decreased snow cover is replenished very quickly in a period of cooler temps. Glacial advance / retreat is one of the best barometers of climate change there is, they're both sensitive to and responsive to temp changes, the glacial retreat in the period you refer to was more than compensated for by glacial advance in the mid 20th century. Water vapour has an atmospheric residency period of 4 to 12 days. The increased CO2 levels is the only mechanism still affecting us as this has an ARP of 115 years.

They're not El Nino years, my opening sentence states they are 10 year moving averages (e.g. 1967 is the average from 1957 to 1977 inclusive). Every year from 1947 onwards is included.

LARRY: You've done what I specifically didn't do and that was to chose specific years. I could have made my figures more dramatic if I'd have done that (e.g. I used an anomaly of 0.607°C for 2007 because it's the 10 year average, the figure for 2007 itself is 0.758°C). Climate is not about specific years, the 10 year average for 1917 is 13.816°C and for 1944 it's 14.031°C; instead of 0.6°C the more realistic figure is 0.215°C.

CO2 levels in 1917 were 299 parts per million by volume, by 1944 they were 309 ppmv. Although small by comparison to the rate at which they're currently rising (2ppmv per year) it is still significant. What's of greater significance is that the CO2 contribution + other greenhouse gases + increased solar contribution = temperature increase, today where there is no increased solar contribution the equation simply becomes increased greenhouse gases = temperature increase. You’ve effectively confirmed that increased CO2 levels cause the temperatures to rise.

ERIC C: These aren’t reconstructed figures they’re instrumental ones. The MWP isn’t part of the instrumental record and has nothing at all to do with the question. In any event, we know about the MWP, what caused it, when it happened, what the temps were etc.

KEITH P: Hallelujah, finally come to someone who understands the science, doesn’t attempt to distort it and has the links to back it up with.

BOB: I think you might be onto something there with ‘shazam’, it could explain a lot.

GJTUDOR: Thank you, a sensible answer and yes, the present warming does have an underlying natural trend. But… you’ve used specific years to get the 25 year temp rise from 1910 to 1940. The specific temps in these years were 13.798°C and 14.141°C, a difference of 0.343°C less one sixth = 0.286°C. If we compare 2007 with 25 years ago the difference is 0.666°C (14.758°C in 2007 and 14.092°C in 1982). Again, specific years are non representative.

The average temp in 1910 was 13.768°C and in 1940 it was 14.025°C, a difference of 0.257°C less one sixth = 0.214°C (compared with the 0.426°C difference between the 1982 and 2007 averages).

RON: Good answer and I admire the work of Watts and what he is attempting to do, it is important to have accurate monitoring stations. But there are some very basic flaws in his argument, not least of which is that for 30 years we’ve been using satellite telemetry to measure temperatures and this shows the same warming as is indicated by the surface stations (slightly more so in some cases). Secondly, temperature changes are measures as anomalies, irrespective of how badly a station is sited it’s the anomaly from the base mean that’s important and indicative of warming or cooling trends.

If a station has been sited on a roof or in a parking lot it will give an inaccurate temp reading but the anomalous reading will only be affected if the surrounding environment is affected; and in most cases this isn’t so.

Thirdly, whilst many stations in the US aren’t well cited they’re a fraction of the global network. Here in the UK we have probably the most reliable network of surface stations in the world and there are very precise specifications for the construction, maintenance, siting, monitoring etc of surface stations. If there is anything untoward the station is off-lined and the data rejected.

Fourthly, take the unreliable stations out of the network and the figures remain the same. Fifthly, stations on remote mountain tops, uninhabited islands, in Antarctica, cited at remote observatories and right across the seas and oceans are again providing the same picture.

DANA: I’m glad you get it, I knew you would. The key is the rate at which temps are changing.

SOPHIE: You’re right, it has been proven. There’s actually very few scientists want to prove it again; it tends to get reproven, almost by accident sometimes, as a consequence of other research.

MADNOELLE: Can’t argue with that – proof that global warming is natural (sort of).

COOCACHOO: Good point about Greenland but, as with so many things, it needs to be put into perspective. The climate on Greenland was never all that conducive to human survival. The communities that were first established in 984 managed to survive there and expand over a period of approx 400 years but it was a very harsh life and crops could only be grown during a very short ‘summer’ season in one of two locations. The fact that anyone was able to survive there was only made possible by the glacial retreat associated with the Medieval Warm Period. This made available some land for the communities to settle.

With the readvance of the glaciers occasioned by the cooling after the MWP the people were eventually forced from their lands. The temp difference between these warm and cool periods was approx 0.8°C (glaciers are very sensitive to changing temps and a small difference can cause rapid retreat or advance). On a global scale the temps fell by about half as much during the time of the Viking occupation (from approx 14.0°C in 1000 to 13.6°C in 1400).

BB: Nice short answer that sums it up. It should have been a natural cycle shouldn’t it?

ED: Levels are now closer to 400 parts per million by volume (387 a couple of months back) and understanding how greenhouse gases work renders it impossible to deny that humans are having an effect on out climate.

JIM: For 30 years we’ve been using satellite telemetry to measure temperatures right across the globe. There are weather stations situated on islands all over the planet and information fed back from ships covering pretty much the entire body of seas and oceans. Here’s a live map of ship locations - http://www.sailwx.info/shiptrack/shiplocations.phtml

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FINAL COMMENT / BEST ANSWER

Best Answer goes to AMANCALLEDCHUDA (Formerly known as a man called GJTUDOR), thanks also to everyone else who answered, there were some good answers.

To Amancalledchuda: You've obviously spent some time on this so thanks for that. I'm not quite sure where you got your data from, you said it's HadCRUT3 but the numbers are wrong. The dataset is constantly revised, you can probably get the latest (up to Sept 07) from HadObs (Hadley Observations) which is on the Met Office website - hadobs.metoffice.com

Hadley uses a different base period to Goddard (1961 to 90 as opposed to 1951 to 80) so there will be differences in any anomalous temp record comparison between HadCRUT and GISTemp, typically 0.1 to 0.2°C.

Using HadCRUT3 the temp diff from Oct 82 to Sept 07 is 0.366°C and from Oct 57 to Sept 07 it's 0.543°C (10 year moving averages).

The 25 year period with the greatest temperature increase is 1982 to 2007 (0.403°C), for the ranges you mentioned it's 0.273°C for 1910 to 1935, 0.276°C for 1910 to 1915 and 0.242 for 1920 to 1945°C


Elimination of outliers improves the reliability of the data by removing the inconsistencies (e.g. 15, 16, 17, 81, 19, 20) homogeniety adjustments are used to harmonise the data in a dataset that has compiled from data from more than one source.

Finally, taking a 10 year average gives a reasonably accurate result, the way I'd calculated my figures was by taking the subject year as the central year in a 21 year range (e.g. 1975 being the average of all years inclusive from 1965 to 1985).

Finally, the anthropogenic contribution is greater than 20% (not sure how you arrived at this figure). The warming in the early 20th century had a substantial contribution from the sun. Today the level of warming is greater than the sum of the early 20th C natural warming + the human component + the recent decline in solar output.

Answer 1

Well, the amount of CO2 (and other GHGs) in the atmosphere has risen sharply over the last century or so and mankind is the likely source of most of this rise. If the amount of GHGs in the atmosphere has increased, then we should expect it to cause some warming.

So, mankind has almost certainly had an effect, thus the warming we are experiencing is *not* entirely natural.

However, the warming is *not* entirely down to mankind either.

So the only correct answer to your question is…

Yes, and no.

In answer to your second question of “when did temps last increase at this sort of rate?”

Looking at this graph http://www.globalwarmingart.com/images/f/f4/Instrumental_Temperature_Record.png I would argue that between approx 1910 and 1940, a period of 30 years, we experienced a rise of, in my estimation, approx 0.55°C. If we reduce that by 1 sixth to give a 25 year equivalent, we get approx 0.46°C.

This is slightly higher than your figure and at a time when the rise is CO2 was significantly lower than it is today… http://www.globalwarmingart.com/images/5/52/Carbon_History_and_Flux_Rev.png


:::EDIT:::


Ah! OK, yes, I see what you mean. As my German teacher at school used to say: “Oh Lord! Help me to keep my big mouth shut, until I know what I’m talking about!”

Right, as ever with this sort of game, it depends on which data set you’re using. I’m going with the HadCRUT3 data set, cuz it’s British. :) I’ve only got data to 2006, because 2007 hasn’t finished yet! Also, www.co2science.org presents the data in an anomaly format, so I’m assuming 0 = 14°C. I’m afraid I have no idea if the data is “outliers eliminated, homogeneity adjusted” (because, let’s be honest, I don’t know what that means! LOL) Anyway, after much playing in Excel I get the following figures (these are the average of the temps for the 10 years preceding the date given. Is that correct?)…

2006 – 14.451°C
1996 – 14.175°C
1986 – 14.028°C
1981 – 13.949°C
1976 – 13.878°C
1966 – 13.931°C
1956 – 13.841°C

In the last 50 years temps have increased by 0.611°C and by 0.503°C in the last 25 years. (Oh bugger! Can we gloss over that bit?)

Moving swiftly on (cough), using the HadCRUT3 data set for the years 1900 – 1950, the 25 years 1910 – 1935 work out at a mere 0.275°C. 1915 – 1940 is 0.404°C, but the winner by a nose is, somewhat surprisingly, 1920 – 1945 with a rise of 0.418°C.

This is within 2% of your rise, so does that count as “sort of” similar? Sadly I suspect I’m going to get my own data used against me, because my past 25 years figure is 20% higher!

Does this mean that it’s perfectly possible that all but 20% of the recent rise could be natural?

Answer 2

They are/have... 1. Been brainwashed by George Bush 2. Are too lazy to look after the Environment 3. Believe what the press says not what certified experts on the subject say (Ex Al Gore and IPCC) 4. There thick headed and too stubborn to notice the change. 5. There afraid to face the truth. There is so many things that the public will believe just because the rich and famous say so. Today's society is based to much on what they say and not individuality anymore. ♥Edit♥ The earth does go through cycles of being hotter and cooler, but for those who believe that, show me a point in history where the temperature has gone up this fast in this short time span. Come on people were not talking about ice ages were talking about a time span of a fraction of an ice age.

Answer 3

Trevor, the global surface temp record is all fouled up with a pervasive warming bias due to poorly sited stations. Anthony Watts is leading the effort to rank the quality of weather stations beginning in the US. So far they have photographed about 1/3 of surface stations and found only 15% of them meet the minimum requirements of NOAA. About half of the observed warming is not real but an artifact of these poorly sited stations.

You should visit http://surfacestations.org to see the pictures for yourself. Some of the weather stations are on top of parking lots!
I like this photo of a weather station at the University of Arizona in Tucson.
http://gallery.surfacestations.org/UCAR-slides/page61.html

You should also view the presentation Watts delivered to UCAR in August.
http://gallery.surfacestations.org/UCAR-slides/index.html
See especially this graph
http://gallery.surfacestations.org/UCAR-slides/page92.html

Since the surface temp record is fouled up, Roger Pielke proposed a different metric for measuring climate change - ocean heat content. This has been used by both warmers and skeptics. Stephen Schwartz of Brookhaven National Laboratory used ocean heat in combination with surface temp record to estimate climate sensitivity. With this more accurate metric, it shows that global warming is not going to be catastrophic.
http://www.ecd.bnl.gov/steve/pubs/HeatCapacity.pdf

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Note to Bob - Watts was very well received by the scientists at UCAR. They welcomed his efforts to document the quality of surface stations. What scientist would not want better quality data? Why should Watts cause scientists to panic? If anything, his work shows we do not need to panic. Yes, Watts is supported by Pielke, McIntyre and many others. Perhaps the people most upset by Watts' research are the folks at the Department of Atmospheric Sciences at the University of Arizona. They were embarrassed by the photos of the weather station they oversee proving they are the caretakers of a very poor station ranked CRN5. Their reputations have been damaged the most so far.

Trevor, thank you for your response. However, you are completely wrong. Studies have shown that 95% of poorly sited stations have a warm bias. McIntyre reconstructed US temp record using only the top 15% of stations and the warmest year anomalies changed quite a bit. Using only good stations, 1934 was the warmest year, followed by 1921, then 1998 and 2006. And the difference in the anomalies were significant. This is only for US temps, but the global station survey should be completed in about two years. At that point, we will have an accurate reading of surface temps and I expect it to be more in line with the metric of ocean heat content. BTW, I have heard the claim the UK network is the best in the world and that may be true, but the UK is a very small part of the globe. Most of the networks around the globe are far worse than the US network. Pielke has a number of photos of stations in Africa and other places with obvious warming biases.

Answer 4

I see your numbers and it is amazing the rate at which the earth is warming. Apparently it must have warmed and cooled at a similar rate during the 14th and 15th century when vikings were able to farm on Greenland. Though it was difficult they were able to do it. Then out of no where the vikings disappeared either by starvation or moved on. What I'm saying is when they first landed on Greenland they could farm. Then by the end of their stay after a couple of hundred years they could no long farm b/c of the landscape turning into permafrost. So apparently at least in Greenland the temps changed drastically at a fairly quick pace in Geologic times.. So who's to say the temps didn't change like that over the world.

Answer 5

Let me pitch in here:

Some Yank. Since each of the seven points is an average of ten points, the trend of the seven points is meaningful. Here's the whole picture, if you like. Note how taking 5 year averages reduces variability.

http://data.giss.nasa.gov/gistemp/graphs/Fig.A2.lrg.gif

Vladoviking - If the temperature goes up a mere 3-4 degrees, the resulting coastal flooding and damage to agriculture will be enormous, costing hundreds of billions of dollars to fix. We're headed there pretty fast, note how, in Trevor's data, the rate of increase is accelerating.

bibsian - The judge rejected the lawsuit asking that Gore's movie be banned and approved it to be shown to students. He said it was based on proven science, and was basically right about global warming. He also said nine small details were unproven, and students had to be told that. Read the full decision here:

http://groups.google.com/group/alt.global-warming/msg/87ffb8db671bf175?

Tomcat, Larry - It is true that the warming of the early 20th century can be explained mostly by natural causes. But the warming of the late 20th century cannot, unless, like Tomcat, you wave your hands and say "shazam". Given that there is an explanation which obeys the laws of physics and works, scientists are reluctant to invoke magic. Even "skeptical" scientists don't claim the recent warming is natural. This graph is illustrative, from the Source below.

http://www.globalwarmingart.com/wiki/Image:Climate_Change_Attribution.png

eric c - Whatever some guy said, climatologists don't ignore the Medieval Warm Period. Here's a good explanation, complete with a graph that shows it (and that we've moved well beyond it).

http://environment.newscientist.com/channel/earth/climate-change/dn11644

Ron C - note that Watts and his band of amateurs with digital cameras has not made a dent in the scientific community. Do you think they don't know about experimental errors and evaluating data? Do you think that they are risking their professional reputations on bad data? Poppycock (an excellent word here). Peer reviewed study after peer reviewed study study has shown that the data is good. He made his pitch to UCAR, did any of the scientists run out in panic? Do any of the reputable skeptics (Lindzen, Christy...) support him?

Answer 6

Looking at your source for temperatures also shows a .6ºC increase in temperature from about 1917 to 1944. Could that increase in temperature have been natural? There was a negligible increase in CO2 prior to 1944.

Additional details:

You did mention specific years in your first sentence when you said "the last 25 years". Then you asked, if it could be natural and if so when?

Also, solar cycle 23 was slightly less active than was 22 but , it was still more active than cycles 14 - 17, which occurred and probably accounted for most of the warming during the pre-WWII period.

I know you only like to look at TSI but, solar activity also changes solar magnetic flux and there have been studies that show a good correlation between a reduction of cosmic rays and increased temperature via reduced cloud cover.

You stated in your response to Tomcat, that "Water vapour has an atmospheric residency period of 4 to 12 days" but the ocean stores heat for decades and that heat is dissipated by evaporation, which creates more water vapor.

In the ice cores, CO2 has been shown to lag temps by approximately 800 years, so it's conceivable that some of the current increase in CO2 is from the Medieval warming period.

Answer 7

Yes it is! And there ARE records of millions of years ago all around us. The pattern they have discovered so far is tropical/hot climate, then there was the first ice age, then tere was a period of tropical/hot climate, and then there was the second ice age, and now we are between ice ages. But recall that this is over millions of years, an amount of time hard to comprehend. It takes a long time for these changes to happen. But they did and they will.
From learner.org:
During the last 10 million years, Earth has had 10 major ice ages and numerous smaller glaciations such as the recent Little Ice Age. Each major ice age has been followed by a warm period of about 10,000 years. We're in a warm period now—more specifically, we're at the end of one. Should we expect another major ice age soon? There's no way of knowing. Climate change may be cyclical, but it's not easy to forecast. Both day-to-day weather and long-term climate change remain difficult to predict.

Answer 8

No, the current warming cannot.

Tomcat and Larry gloss over 2 important details in their conclusions otherwise.

1) The warming from 1910-1940 was not entirely due to the Sun or other natural causes. Human greenhouse gas emissions played a role back then as well (though not nearly as large of a role as they currently play).

http://en.wikipedia.org/wiki/Image:Climate_Change_Attribution.png

2) Solar output increased from 1910-1940, but it decreased from 1980-Present.

I suppose one could argue that theoretically the current warming trend could be due to primarily natural causes, as was the case from 1910-1940. However, to make this argument you have to ignore the data which clearly disproves this theory.

I believe Trevor's point was that the current warming is far too rapid to be caused by long-term natural cycles, which cause gradual warming over thousands of years.

Answer 9

Yes, from 1910 to 1942 the average global temperature rose by .45 degrees, which can be explained by an increase in solar output levels. How many positive feedback mechanisms occurred, such as reduction of sea ice coverage, reduction of snow cover, receding glaciers, INCREASED CO2 LEVELS and increased atmospheric H2O levels. How many of those positive feed back mechanisms are still with us today from that increase in solar activity, considering solar output levels have not diminished since 1942? How long does it take the ocean to dissipate such an increase in solar output?

A natural cycle is definitely not out of the realm of possibility, as far as my feeble mind is concerned.

http://data.giss.nasa.gov/gistemp/graphs/Fig.A2.lrg.gif
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EDIT2:

Trevor all of the years you listed are biased by El-Nino, and the ten year smoother further biases the entire temperature record.

http://www.oar.noaa.gov/climate/observing1.html

EDIT:

Trevor

I do not believe that I ever mentioned the word sunspots, there are other methods of obtaining reconstructed TSI. I do not believe I have shot myself in the foot. Atmospheric water vapor may have a residency of 4 - 12 days, but it's rate of replacement is also relative to atmospheric temperature. TSI has not fallen below mid 1970's levels, if the sun on average is maintaining an average of 2 watts more energy, physics demands that the atmosphere holds more water vapor, the oceans are warmer, so there is less sea ice and less snow cover and a hosts of other positive feedbacks.

Interestingly enough you say that temperatures should be similar to 1942 because of sunspots, well in the US they are very close, which brings up another point, what exactly is an average global temperature. This concept has some theoretical problems.

http://data.giss.nasa.gov/gistemp/graphs/USHCN.2005vs1999.lrg.gif

So.... shazaam.

http://www.fel.duke.edu/~scafetta/pdf/2006GL027142.pdf

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Answer 10

What natural climatic process can cause the CO2 levels in the atmosphere to rise to over 300 parts per million over just a few decades?

Seems pretty much man-made to me