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.
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.
