I think the biggest factor differentiating the climate on the halves of the globe is that there's more landmass on the upper* bit of the Earth, so my first guess would be that the difference is tied to this overall difference.
Because co2 is not evenly distributed with most polluters concentrated in northern hemisphere and prevailing wind direction to be from equator to poles.
Any air moving towards the poles must necessarily be balanced by air moving away from the poles. This manifests as "Hadley cells" and other similar wind patterns.
This suggests that when the ice melts the darker water absorbs more energy from the light, and then warmer water freezes less resulting in a permanently warmer arctic.
I really dislike the use of the word "anomaly" in climate change circles. It may be technically correct, but it feels like propaganda. All it is is the difference to the average of an arbitrarily chosen time frame.
It would actually be strange if temperatures where exactly like the average all the time, so calling it an anomaly if they are different from the average really seems misleading. Again, it may be the technically correct term, but it has a different meaning in "normal language" imo.
The trend of the temperature may be "anomal", but that is not what they call an "anomaly".
It is a comparison of two averages, not of a single temperature to an average. A changing average suggests a change in the underlying factors at play, because while a single observation may not ever match the average as you say, a system in equilibrium should not see the average changing. This is why it is called anomalous: the mean is changing continuously.
It’s a crude metric but in the framework of the analysis (pre-industrial vs post-industrial) it is an appropriate comparison.
I would consider that "anomaly" would refer to something unusual or unexpected, an outlier, or a weird unexplained occurrence contrary to our expectations, or a one-off deviation followed by a return to the norm.
On the other hand, a continuously changing mean or a systematic pattern IMHO is not an "anomaly"; something can't be unusual for long - if something has become or is clearly going to become usual, then it's a "new normal", it's a "trend" or something like that, but not an anomaly anymore; if we're seeing what we expected to see, that can't be called an "anomaly" because that's the expected result.
With respect to climate change we see that the underlying factors have changed, we mostly know why, we observe the consequences now, see their trends and can predict how the mean is going to change - so all the factors are contrary to the definition of "anomaly".
Yes, this is a good point. It is only anomalous if we expect the mean temp to remain relatively constant—it is definitely dependent on the conceptual framework!
I don't think that explanation is correct. The average temperature of a year is just a specific way to take a measurement. Comparing it to an average of averages over several years is then the same as comparing a measurement to an average of measurements.
That the climate should never see averages changing seems obviously false. There clearly are cycles that last longer than a year, for example, as several ice ages came and went before industrialization. El Nino take phases last between two and seven years.
Yes, the averages can and do change—that is my point. A changing average suggests something about the system is changing. It doesn’t need to be compared to preindustrial temperatures, but it is a good baseline because the temperature variation (as shown in the chart) was pretty small within that timeframe compared to the changes we are seeing today.
Temperatures are anomalous, given what we know about the state of all the non anthropogenic factors acting upon climate at the moment. Nothing really contentious or 'propaganda' there.
It is a technical term meaning difference to the average of a certain period of time. In itself such a difference to the average does not imply anything strange is going on. I'm not saying there isn't an anomaly in the sense of common speech, it just seems weird to me to use it in charts that are supposed to show the existence of an anomaly.
Anomaly relative to the climate without the extra human forcings, like how you could call the dead forest from acid rains an "anomaly". A simple average of a reference period is used as reference for simplicity but is by the fact that climate change is happening much faster than typical climate variations so it's fine for now: the difference is (still) essentially entirely out fault.
I think the point parent is making is that it is possible to cherrypick a reference period.
You can say that the melting of glaciers is an anomaly but when an ancient forest appears below the melted glacier how can we agree on what an anomaly is?
I don't want to deny global warming but I agree with the parent that it's difficult to state what an anomaly is.
It is true that you don’t want anomalies to be anomalous only with respect to some arbitrarily chosen (or sought) feature of the reference periods. The solution to this is to do sensitivity analysis of the anomaly to these ‘arbitrary’ features (length, starting/ending points). With most climate things, anomalies will persist. This is a standard thing to do.
It means the difference to the average of a certain time frame. Whether it was caused by human activity is a different question. That is why I call it misleading. They certainly want to imply humans caused it, but at the point where they show the chart they haven't really shown it. That requires considering other aspects.
The fastest shifts occurred after large volcanic activity. And cold summers for a few years then led to crop failures.
Am really interested in more analysis of correlation of reduced sunspot activity and then increased volcanic activity. It appears to be a fascinating correlation.
Update - The mammoths with undigested grass in their stomachs, which froze to death while eating, may indicate magnetic pole flip creates faster climate change than volcanic activity.
> Am really interested in more analysis of correlation of reduced sunspot activity and then increased volcanic activity. It appears to be a fascinating correlation.
Sad to see the sunspot conspiracies still alive and kicking. Here, have some 14 year old news about how they don't matter enough to bother with in discussions about today's climate: https://www.nature.com/articles/nature05072
No they picked a certain time frame and compare to the average temperature of that time frame. Nothing more, nothing less. I think the reference time frame is some 20 year period in the end of 20th century, but not sure if I remember it correctly.
From the site the baseline is very clearly stated:
What is the Yearly Average Temperature Anomaly?
It is the difference between the average yearly global surface temperature and its pre-industrial baseline. The pre-industrial baseline is calculated as the average temperature from 1850 till 1900. The value for the current year is actually the average for the last 12 months, for example in June we include values since the previous July.
I really don't understand what your issue is with the terminology. Are you suggesting there is no change from the norm? Propaganda as in there is a political agenda to presenting this data? Would that be that the data is wrong, if so on what basis? Or that the data is irrelevant and it is being presented as relevant?
Global temperature changes seems very relevant to me. This site is also just presenting data, the language is pretty neutral and in line with the common use of anomaly ("something that deviates from what is standard, normal, or expected") given the baseline they have stated, as well as the wikipedia article you link. The main issue I see from the wikipedia article is that these are not "standardised anomalies" - but the site is not claiming to provide these.
If your argument were that they should provide more data I could see that, although it's marked as version 0.1 so perhaps that's a bit harsh. If it's just that they're using the wrong word, then that's not very compelling to me.
As I said - the issue I have that a year having a different temperature from the average of some timeframe is not actually "anomal". It is to be expected. It would in fact be weird in most cases if temperature would be exactly like the average.
So calling any difference to the average an "anomaly" seems misleading to me.
The trend of rising temperature may still be "anomal", but that is not what they are referring to.
Your explanation kind of points out the problem, as you also seem to think a "deviation from the norm" is somehow unusual.
If you look at another example, it should be obvious: take the average temperature throughout one year, then plot the "anomaly" of daily temperatures in that year against the average temperature of the year. Then in summer it would be "anomaly hot" and in winter it would be "anomaly cold". Except it wouldn't actually be anomal to be hotter in summer and colder in winter at all.
I’m guessing English isn’t your first language by your use of the word “anomal” - which doesn’t mean what you think it does. This may be contributing to your confusion.
https://xkcd.com/1732/ Suggests the fastest temperature change in last 20k years is around 1 deg c in a 1000 years. The graph linked here shows 1 deg c in around 50 years.
Annual variation is up to 0.3 deg c, mostly less, from eyeballing the graph data. If you’re suggesting that there is a reason we shouldn’t call a 1 deg c plus change an anomaly, you should really just say what that is, just like you have for winter and summer which nobody would call an anomaly.
The chart is a chart of the yearly "anomaly". So even a 0.3 degree deviation is plotted in the chart as an "anomaly". Clearly you don't understand the issue, which is exactly my point. It is a misleading label.
I am not saying the rise by whatever many degrees is not an anomaly. That is simply not what they plot. They don't call the steep rise an anomaly, they call every deviation from the arbitrary average an anomaly. They don't plot the "steepness of the rise", although you can see it in the chart. Every point in the plot is called an "anomaly", not the plot as a whole. Even the data points where a year is colder than their arbitrary average is called an anomaly in their chart.
English is not my first language but I think I know what an anomaly is supposed to be.
The term 'temperature anomaly' has come to mean: A temperature anomaly is the departure from the average temperature, positive or negative, over a certain period (day, week, month or year).
If I look up 'anomaly' in a dictionary: a person or thing that is different from what is usual, or not in agreement with something else and therefore not satisfactory
The word anomaly is only used for unusual/unexpected things. Where in the scientific world the term temperature anomaly doesn't have to be used for unusual and unexpected things.
For example a temperature anomaly of 0, which isn't unusual or unexpected at all, is still a valid temperature anomaly. However, you would never use the dictionary meaning to classify the 0 as an anomaly.
Maybe it feels more neutral to use a term like temperature deviation or delta.
I don't know who initially came up with the term temperature anomaly and what their intend was, so I won't blame anyone of propaganda.
The temperature rise since pre-industrial times as a whole is generally considered an actual anomalous situation, so it seems fine to keep using the term temperature anomaly in this case.
Yes - I know it is technically the correct term. If you look it up on Wikipedia, you get the proper definition. But for people not in the field it suggests something different than it actually shows - even though by chance there is also an actual "anomaly" in the form of the rising temperature trend.
You're really straining for this point - nobody is going to be confused by the use of the word anomaly. It is not "chance" that there is an actual anomaly, that's the reason the terminology is being used.
If they'd used the word "deviation" would you have been happy? Or is your real objection to the use of the word "anomaly" to describe temperature deviations in science generally?
I don't really think anyone is misunderstanding the word "anomaly". I get what you're saying I just don't think it's an issue.
By saying it is not chance I mean that the word "anomaly" is used because there is an anomaly. That's what appears to be confusing you, that you feel this word is being picked to imply something about the science, when in fact the causality is the other way around. The science has shown there to be an anomaly and the word has been used because there is an anomaly. The fact that it is less relevant pre-1920 is not important because people care about climate risks now when there is a clear anomaly shown in the data. You're focusing on something utterly unimportant.
No you are wrong, it is not that "science has shown there is an anomaly", and the word isn't being used because there is an anomaly. It is just a definition. I don't think you have understood the issue at all. Rather, you convince me even more that it is an issue.
For comparison, again, consider the average temperatures within a year, and then the daily temperatures are an "anomaly" and summer and winter would be anomaly because their temperatures deviate from the average. You wouldn't say "science has shown that summer and winter are an anomaly".
Nobody at all other than you says summer and winter temperatures are anomalies. Really - what are you on about? This is a completely irrelevant example. Again who is getting confused here? There is no misunderstanding at all on the meaning of this data just quibbling on the word usage. Even if we call summer and winter temperature variations anomalies - who cares?
Anomaly is used because this is a new phenomenon due to human actions. You have no apparent concern about this but are just worrying about word usage.
Why do you think that the word temperature anomaly is used in climate science? The important issue is the global risk not your carping about the terminology.
"Anomaly is used because this is a new phenomenon due to human actions. You have no apparent concern about this but are just worrying about word usage."
No you are wrong. That is exactly the issue. It is not used because it is a new phenomenon due to human action. It is simply a technical term meaning different to some average. That is why it would also be used in a chart of temperatures throughout the year.
You demonstrate the issue very well. However, I give up convincing you, as clearly you won't understand it for some reason.
"Why do you think that the word temperature anomaly is used in climate science? The important issue is the global risk not your carping about the terminology."
So you admit it is being used for propaganda, not for scientific reasons. Exactly what I am concerned about.
Why are you using the pejorative term "propaganda"? It is communication.
I don't think you're confused about the data. I don't think I'm confused about the data. I don't think anyone is confused about the data.
To me the important thing is the data, I don't care if they call it "burning hot death" in the chart. You're focusing on a word that I don't care about, and that is used in accordance with its technical meaning. And you're ignoring the data and distracting from the issue it represents.
To convince me I'm wrong on the usage of the word anomaly - please find the etymology of this word as used here - I had a look and couldn't, but don't really think it matters enough to search for why this word was used in the first place.
But really, I think you're deliberately trying to detract from what the data shows by focusing on something irrelevant.
To know it was "intentionally misleading" you'd need to know their intentions, I don't see how you could do that. I don't see this as intentionally misleading, as you can probably guess, so I don't know why you would assume that whoever made this did.
I said here that the pre-1920 period, which is relatively flat (within a variation of around +/-0.5 deg C), represents years with normal temperatures:
I'd say anything outside of +/-1 deg C from that average would not be "normal", and would need need an explanation. I'm not an expert though, but eyeballing the data that looks reasonable to me. I have already said this though, so not quite sure why you're asking me again.
I also don't see this as misleading ("intentionally misleading communication") - are you saying there is not an "anomaly"? That there is no climate change? Or that any climate change is within normal variation, that is, not affected by industrial emissions?
The example you give of summer and winter having different temperatures is obviously not relevant to climate change as presented here. The "little ice age" has a scale and speed of change not comparable to what is presented here, as I've already mentioned.
Given all this I don't understand how you can think there is no anomaly. It is even less clear to me how you would conclude this was intentionally misleading when it seems totally reasonable to label this an anomaly based on the data and the science behind it, which you seem to be ignoring or disagreeing with.
I mean... they even have a chart of average temperatures going back to 1850, so it's not like they're hiding their data.
I guess you might be arguing that by calling it an "anomaly" they are making an assumption on the science that isn't justified by the chart. But the whole existence of this site is clearly premised on climate change being an issue, so the causality is the other way round. The site provides a simplified visualisation of data that shows what people have concluded through exhaustive scientific analysis.
The exhaustive scientific analysis provides the justification for the anomaly, this site shows this data in a way that's easy to digest. You shouldn't be looking at this data in isolation and saying there is man-made climate change, you should be looking at this site as a starting point to review more research and understand why this data that looks concerning is in actual fact really concerning.
If the scientific literature was in any was non-conclusive about whether there is genuine anthropogenic climate change, I'd have more sympathy to your point on whether using the word anomaly is appropriate or misleading. But you're not arguing the science, not even arguing the data, you're only arguing the word "anomaly", and for me that's such a long way from proving this to be propaganda that I don't feel you're arguing in good faith.
I am not at all concerned with the use of the word anomaly because I already am concerned about climate change. I'm assuming you're concerned about the use of this word because you're not concerned about climate change.
Pre-1920 is roughly in-line with average, 1920-1970 looks to be above average but could be argued to be within normal range of variation, post-1970 is clearly above normal range of variation.
Your concern seems to be (1) that there is some negative connotation to the word "anomaly", (2) that the chart labels small differences anomalies rather than just large differences, despite small differences being possibly within a natural range of variation, and (3) that a baseline has been arbitrarily and improperly chosen.
These are all non-issues. The word "anomaly" as used here is clearly defined, and means deviation from a baseline. It is not being used in a pejorative or leading sense. In any case, the data is clear - there is a larger deviation towards higher temperatures, over many years, without historic precedent.
What you call an arbitrary average is not arbitrary. It is chosen for a clear reason - the temperature rise is due to industrial emissions which did not exist prior to the period covered by this chart, and at that point global temperatures were more stable than they are now by around an order of magnitude.
Nobody should be confused or misled by the use of the word anomaly here. The context is obvious to anyone paying attention to the science. I doubt you're confused by the data as presented, so I really don't understand why you're concerned about the title.
If it helps, think of the chart as showing which years actually are "anomalies". You seem to have a vague definition of an "anomaly" as something like a significantly large change from a specific average - presumably the temperatures over the last 1000 years would be sufficient.
I feel like you're expecting this chart to show more than it does, it's really very simple, and in no way misleading.
"In any case, the data is clear - there is a larger deviation towards higher temperatures, over many years, without historic precedent."
Except you also seem to misunderstand the use of the word, as it is completely unrelated to there being a "deviation towards higher temperatures". At most you could argue that it doesn't matter if people misunderstand it, as there happens to actually be an "anomaly" anyway.
About the reference time frame - I think things were going on before, like mini ice ages and what not. However I merely wanted to point out that the timeframe is arbitrarily chosen, not that it is necessarily a bad choice. In combination with the word "anomaly" it becomes more questionable as it kind of implies that those 10 years were "normal".
Again - it's not arbitrary! It's chosen because industrial emissions have affected the climate. There is a very clear reason why it was chosen. That's why we use the word anomaly too - it isn't chance!
Are you trying to say that it's not an anomaly at the beginning of the period in the chart when the delta is negative? I already granted that point but it doesn't matter because everybody already knows there is an actual anomaly due to industrial emissions! The "implication" that the 10 years were "normal" is not questionable because the temperature was normal before! This case doesn't need to be made here because it's been made by a global coalition of governments and scientists in exhaustive detail.
From Wikipedia on mini ice age:
"...a multi-centennial period of relatively low temperature beginning around the 15th century, with GMST averaging –0.03 [–0.30 to 0.06] °C between 1450 and 1850 relative to 1850–1900."
This is within the annual variation I was suggesting and is not comparable to what we see today. It's irrelevant.
"There is a very clear reason why it was chosen. That's why we use the word anomaly too - it isn't chance!"
So it is propaganda. The official definition of temperature anomaly is just "distance to an average".
There was temperature variation before industrialization, for example mini ice ages, so simply showing there is a temperature difference to some small period of time in the 19th century is not sufficient to show there are "anomalies".
You're not reading what I said. I just responded on "mini ice ages" and you ignored it. It's clear why they are using that period, and is scientifically justified.
Propaganda is a pejorative term that you're not justifying the usage of, and I certainly don't agree with your usage here.
I don't know the etymology of anomaly, but I think it's a perfectly sensible usage.
You are avoiding the question of whether you think there is an anomaly, probably for the good reason that there clearly is one in the colloquial and scientific senses of the word.
The data and science are clear, and I don't think your professed confusion at the use of the word anomaly is in good faith.
If you don't think there's a problem to be addressed, then it's on you to show the data doesn't show an issue. Just making accusations of propaganda is not good enough.
Comparing to a baseline is useful because that is what our culture, technology and habits are adapted to. And the conditions that ecosystems can be based on. An increase in temperature away from that has consequences that need to be understood.
I have nothing against the comparison, just with the choice to call the deviation from the average "anomaly".
I think in one step you should present the data, making sense of it is another step. Technically "anomaly" is just used for the distance to the average of some chosen timeframe, but in common language terms it suggests something unnatural is going on. As I said, it would be unnatural to have exactly the average temperature every year. (It may still be such an extreme difference that it is unnatural, but that is not how they use the word anomaly. It just means different from the average).
The non-purely-materialistic dimension of reality (the part that prevents humanity from actually doing anything substantial about climate change) unfolds according to people's perceptions of reality, not reality itself (which we do not see, even though it seems to be the exact opposite of that). It may be enjoyable to look down one's nose at the unintelligent, but realize that intelligence is a spectrum and the sense one has that they are at the apex of that spectrum is illusory.
Science is a very useful tool, but it is not the only tool we need to deal with this problem, and it is certainly not the best tool for dealing with the most important unsolved (and seemingly not even realized) aspect of it: the human mind.
I think we need to start thinking very differently about this problem - one approach (applied to a different domain) is described in this[1] post, I think it would provide more value than more and more scientific statistics, which seem to be accomplishing very little.
I mean people trying to show or prove the effects of climate change. Whether you believe in it or not, there supposedly are specialists working in that area. At least that is usually the argument, that there are experts who worked it all out whom we should listen to. So I think those can be called "climate change circles".
Since at this point 99.9% [0] of all studies come to the conclusion that climate change is real and man made, can we just use the phrase 'reputable scientist' instead of 'climate change circles'?
To add to your post, where and how did they determine that 30 years was the appropriate time scale to use?
>The value we show is a 30 year rolling average of temperature change. We have chosen that long term trend because it fits the time scale of the climate and its changes.
There isn’t enough temperature record around before that timeframe to estimate an accurate global average. You can still see the effects of temperate indirectly
Arguably, the quality record only began with the launch of satellites. How much can we really trust some weather station in the middle of Montana from 1880? And of course pre-satellite the data for the southern half of the globe is relatively sparse.
When it comes to CO2 in particular, there are things like ice cores and plant fossil stomata that gives us some understanding over geological timeframes, but that's very different from a thirty year average.
Even if the measurements from the middle of Montana is correct, I could imagine there are different ways to extrapolate to average global temperature from just a few points of measurements. In the end, it will just be another estimate.
That reminds me of a thought experiment. Suppose you want to accurately measure the average temperature of a company cafeteria. How many thermometers do you need and where do you place them? Do you keep them in fixed locations or move them?
That thought experiment is readily adapted to other spaces, such as a high school gymnasium or the state of Iowa.
I'm presuming that the foundation here is solid and well-intentioned, but there are many different data sources that could be powering these visualizations so a clearer citation would be helpful (beyond what is provided, just the orgs, Berkeley earth+nasa).
I'd like to see some innovation in reporting on the human side of the puzzle....how people perceive the problem of global warming, how they feel about it, what is behind how they feel about it, etc.
Maybe it's just me, but preaching to the choir with ever more impressive science is not moving the ball forward very fast, and if you trust the science, moving the ball forward quickly is an ability that is crucially important.
Maybe visualizations like these will finally get the message through to the last bastions of ignorance.
Or maybe not. If at this point you are still pretend to be skeptical about the data, it's probably more to do with willful blindness rather than intellectual rigor and no amount of data will ever convince you otherwise.
Truth is that lots and lots of people benefit from that continued 'doubt' delaying further actions. Even though in the end we'll all suffer the devastating consequences - the political upheavals, the social unrest, the ecological destruction - there are still people that are so obtuse as to think that this will not tough them.
I have a feeling that the climate change charts induce a similar knee jerk reaction as IQ scores or vaccines. Most people have an ideology they subscribe to and will argue using facts and reason in order to support it. I have yet to witness a religious person be reasoned into atheism. I suspect the applies for the above mentioned categories, whatever side of the fence the person happens to be on.
Charts and visualisations are a great way to trick people. Not only is the source data obscured (and so readily cherry picked) but it opens up all sorts of tricks around visual perception.
I also suspect most people yet to be convinced will immediately think back to Al Gore's infamous hockey stick chart when presented with visual simplifications of deeply complex climate data.
At the heart of the matter, looking at such a chart isn't meant to inform you, it is meant to elicit an emotional response, and they have been trained to respond with skepticism.
Surely you mean the infamous lies about the Mann 1999 "hockey stick"? The Mann 1999 results are correct (see for instance https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5505119/figure/... for confirmation) and the graph doesn't do anything more nefarious than the plot summaries you'll see in imdb: it summarises a complicated thing.
The results are only verified correct for the recent past (for which we already have data for from actual, rather than proxy readings) but even the NAS committee concluded that from 900-1600 they had only mild confidence in the method, and before that very little.
