Talk:Instrumental temperature record

Old general discussion

I've (William M. Connolley 20:03 Feb 12, 2003 (UTC)) moved 2 paras to the end. These are:

the intro that someone copied in, viz:

"The historical temperature record shows the fluctuations of the temperature of the atmosphere and the oceans throughout history. Climate scientists generally agree that Earth has undergone several cycles of global warming and global cooling in the last 20,000 years, with the average air temparature fluctuating within a range of about 3 Celsius degrees (5 Fahrenheit degrees), over this time period."

This is mangled info. Someone can straighten it out if they like. If you look over the last 20 kyr, the biggest signal you see is the end of the last ice age - so the stuff about little cycles is then in the noise.

There are various sub-cycles/sub-signals, of ??1500 year ish?? periodicity; and their are the D-O events etc etc. But the above para mangles that. *Also* it fits rather poorly with the emphasis of this subsection-now-a-page, ie on the last 150 or 1000 years - so it shouldn't be up there in the intro.

I've also pushed

"In January 2002, scientists released data showing that Antarctica had grown about 25% (???). Some editorial writers claimed that this contradicts the expectation that rising temperatures should cause the ice cap to shrink. However, the scientists studying the situation in the Antarctic who released this data point out that local cooling in some areas is consistent with an overall trend of global warming and say that "the ice-sheet growth that we have documented in our study area has absolutely nothing to do with any recent climate trends."[9]"

into the misc section. The first sentence is junk. If its to stay, someone has to find a decent ref to what its supposed to mean. Mind you, ref [9] is nice and its a pity I've misc'd it too...

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The IPCC says that it has corrected the land station data to account for the urban heat island effect. To do: find and summarize their correction technique.

The comment above has been around for about a year, and still no one has shown me where in any IPCC report they have explained how they "account for" urban heat islands. So I'm inclined to say rather:

Critics of the IPCC report note that it fails to explain how it accounts for the urban heat islands. These critics argue that the heat island effect correlates with land-based thermometer readings better than the global warming theory espoused by the IPCC.

... or something along those lines. Work with me here, folks. Let's make an informative and neutral article. --Uncle Ed

That looks fairly reasonable - I'd modify slightly:

The IPCC report does not explain how it accounts for the urban heat island effect - increased warming due to proximity to major cities. The heat island effect, if not properly accounted for, would tend to increase the amount of apparant warming.

Martin

(William M. Connolley 09:46 Feb 13, 2003 (UTC)) There is at least a problem in the wording here. IPCC doesn't do research, it reports other peoples. But apart from that... see section 2.2.2.1 [1]. In particular:

These results confirm the conclusions of Jones et al. (1990) and Easterling et al. (1997) that urban effects on 20th century globally and hemispherically averaged land air temperature time-series do not exceed about 0.05°C over the period 1900 to 1990 (assumed here to represent one standard error in the assessed non-urban trends). However, greater urbanisation influences in future cannot be discounted. Note that changes in borehole temperatures (Section 2.3.2), the recession of the glaciers (Section 2.2.5.4), and changes in marine temperature (Section 2.2.2.2), which are not subject to urbanisation, agree well with the instrumental estimates of surface warming over the last century. Reviews of the homogeneity and construction of current surface air temperature databases appear in Peterson et al. (1998b) and Jones et al. (1999a). The latter shows that global temperature anomalies can be converted into absolute temperature values with only a small extra uncertainty.

Errr... shouldn't all this go into the UHI page?

Yep. And then summarised here. :) It all seems rather a lot of work... :-/ Martin

William, the large quote above (0.05°C over the period 1900 to 1990) seems at first reading to answer Martin's other question: are heat islands causing global warming. My question is different: are temperature readings taken within heat islands giving a false impression of global warming. That is, (1) if a city gets 0.8°C warmer, and this warming is averaged in with all other temperature differences, I think this would be a statistical error. What do you think? Also, (2) if cities get much warmer, suburbs get kind of warmer, rural areas get a bit warmer, and uninhabited areas don't get warmer at all, what would this tell us? (Not saying that's the case for now, just asking what this would tell us if it were so.) --Uncle Ed 17:19 Feb 13, 2003 (UTC)

AFAICT, "globally and hemispherically averaged land air temperature time-series" - I think this phrase is referring to the temperature readings rather than the actual temperatures - IE, it answers your question... Oh, I'm copying some of this stuff to the urban heat island page. Martin

There is an answer to UE from IPCC. Essentially, you can (if you wish) separate out the obviously-likely-to-be-affected stations if you like, but it makes little difference. Reasons include: cities are small areas anyway; the trends from cities (etc) don't in fact differ substantially from the trends without them; in fact the trends over city areas agree quite well with the dreaded MSU... I'll try to find this and add it in, since its clearly a concern (William M. Connolley 21:31 Feb 13, 2003 (UTC)).

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I have started studying a paper on the temperature record in the USSR. The writers find no warming trend in rural stations and hint (or imply) that other researchers have selectively chosen data to fit their "warming" views. [Read it yourself] and decide. --Uncle Ed 17:52 Feb 13, 2003 (UTC)

Its worth reading (William M. Connolley 21:36 Feb 13, 2003 (UTC)). I've had a brief look before. Of the 2 stations I picked to check his analysis, one had the jump he claimed (according to objective statistics) and one didn't, or it was impossible to tell: the trends he claimed as implausible against "neighbouring" stations were from places 100's of km away, and in different exposures: near the sea or not.

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Martin and William,

I'm not sure either of you is getting my point. I am not wondering whether a few hot cities are making the whole world hot.

I am wondering whether a large number of the temperature readings from weather stations in and near rapidly warming cities, when averaged with a relatively small number of temperature readings from rural and remote stations, are giving a false impression of global warming. That is, it might be that (A) the only parts of the world that are warming are the urban heat islands and (B) the only reason these are heating up is because cities absorb and generate heat; rather than (C) that carbon dioxide, etc. is causing worldwide warming.

Do you understand my point? (I'm not asking whether you agree with my point of view, but only whether my English is clear.) --Uncle Ed 22:33 Feb 13, 2003 (UTC)

I believe so - let me paraphrase to try and prove it.

* Because of the urban heat island effect, cities are warming up more than the surrounding countryside

* Thermometers are recording an increase in temperature

* Many thermometers are located near urban heat islands

* Therefore, the temperature increase recorded by thermometers may overestimate the actual temperature increase of the climate as a whole.

To draw a parallel, one shouldn't put the thermostat in one's house next to a log fire, because in that case the thermostat will overestimate the general temperature of one's house.

My reading of the IPCC report is that the distortion introduced by the urban heat island effect is, at most, 0.05°. In other words, if we had located our thermometers away from urban heat islands, they would have recorded 0.05° less temperature increase over the period 1900 to 1990. Of course, this depends on whether you trust the research cited by the IPCC... Martin

I mostly agree with Martin. Have you read the bit about marine and borehole temperatures? This does a lot to counter your point. I also think you're wrong to suppose that, numerically, urban reading predominate. Martin: note that strictly speaking IPCC reprots that UHI leads to at most 0.05 *uncertainty*. They don't (I think) explicitly state that this is necessarily in the warming direction.

Thank you, both, for helping me to feel understood. Now I'll have a G-R-E-A-T weekend! ^_^ (Uncle Ed)

Expert review (Feb 2022)

I've received comments about this article in a Word document by Blair Trewin, one of the authors of the IPCC Sixth Assessment Report. This is done as part of this project for 3 SDGS. I will try to enter his comments into the Wikipedia article over the coming days/weeks and also raise discussion points here on the talk page. In case someone is watching this page and has worked on this Wikipedia article a lot and would be interested to collaborate, please reach out to me. In that case, I could e-mail you the marked up Word document for your careful consideration. I am a complete non-expert on this topic, so will struggle. EMsmile (talk) 22:49, 23 February 2022 (UTC)

Here are some of the main comments from the Word document that Blair provided to me. Do people broadly agree with his suggestions? (I am happy to forward the Word document to anyone who's interested, just send me an e-mail through the system):

1. Change citation to IPCC AR6 WG1 (these numbers are also in SPM). Think it best to present consolidated assessment here rather than individual data sets for consistency.
2. AR6 findings. Since AR6 uses changes from one period to another (rather than linear trends) as the primary temperature change metric, there is not an assessment finding re: linear trends but results are reported in a table. Suggest citing Chapter 2, Table 2.4 - the final chapters are still being typeset so page numbers are not necessarily stable, but table numbers should be.
3. Regarding the figure that is currently under "warmest years": This figure is about records at the regional level, not in global means - I would move it to the regional temperatures section and introduce a discussion on extremes there.
4. I think we want to structure this in such a way that it can be updated with each new year's data with fairly minimal disturbance. I've suggested a replacement paragraph below. I also suggest we focus here on WMO and IPCC as consolidated sources of information, while noting that they draw on a number of data sets (which I then suggest we discuss in detail in the 'Global temperature since 1850' section).
5. Regarding the paragraph that starts with "While record-breaking years can attract considerable public interest": I'm not sure this paragraph really adds very much. The key points we want to capture here are that there is a long-term warming trend, that there is variability about this trend because of natural sources of variability (e.g. ENSO, volcanic eruption), that not every year will set a record but record highs are occurring regularly.
6. Regarding the table "Top 10 warmest years (NOAA)": We will need to take a decision on which dataset to use here. IPCC uses the mean of four different datasets - there are advantages in doing this (including that it is expressed relative to 1850-1900), but at the moment there is a loss of transparency since the consolidated dataset itself will be accessible through the IPCC data portal which is not yet operating. Is archiving the time series on Wikipedia itself an option?
7. Regarding the image under "warmest decade": I like the format of this image, but it will need to be updated for the latest dataset versions. It's also unclear which underlying dataset is used (presumably not NOAA given the 1850 start date). (NB the source data is explain when clicking on the image but perhaps a reference in the caption itself would be good?)
8. Chapter 2 executive summary (currently p6), also in the main body of the chapter but expressed slightly differently. This is the only AR6 finding which compares the last decade specifically to paleoclimate results, although there are other relevant findings on paleoclimate timescales (e.g. rate of warming in last 50 years).
9. Regarding the table with temperature anomalies: Whichever dataset we end up using here, I suggest we use years ending in 0 to align with the IPCC reporting to 2011-2020 (and so we don't have a "decade" with only 1-2 years of available data.
10. Regarding the graph where the caption starts with "Colored bars show how El Niño years": This looks like something that's been produced specifically? (WMO has from time to time published something conceptually similar in its annual State of the Climate reports but hasn't distinguished strong from weak events). If it doesn't have a defined source then we probably need to have a link somewhere to how the strength of El Nino/La Nina events is defined.
11. Regarding the paragraph about El Nino: There will be papers which can be cited here. (As it happens, I've got one myself in review, but there are others which have been published). The new text can largely be inferred from the graph (assuming it stays in its current form). Note that the 1982-83 El Nino has a weak temperature response because it was offset by the El Chichon eruption.
12. Presumably there will be links here to pages on the Pinatubo and Agung eruptions? Larger volcanic signals are sometimes quoted but these are typically either not for a full year, or are model simulations rather than observations. The effect of Pinatubo was also partially offset by El Nino conditions which prevailed for much of the 1991-94 period.
13. Either here, or in the 'Temperature anomaly' article, there needs to be a discussion of which baseline periods are in use, the purposes they serve, and why the choice of baseline has no impact on long-term trends.
14. A picture of a Stevenson screen might be useful here. The MMTS name covers both the instruments and the shelter so shouldn't be used for the shelter alone.
15. Buckets are almost out of use now but were heavily used historically. There are papers which can be cited here.
16. I think either as an addition to this section, or a new section (I prefer the latter), there should be a discussion of how global temperature datasets are developed from the base observations, and a listing of the main datasets. Reanalyses, and how they are used/not used, could also be introduced here - I see there is a Wikipedia article for 'Atmospheric Reanalysis', although it could do with some more content. (I'm not a reanalysis expert but can point you to some if you want that article strengthened).EMsmile (talk) 17:36, 24 February 2022 (UTC)

Hi User:RCraig09 what are your thoughts regarding the comments by Blair Trewin which I posted above? Would you have time to involve yourself to address them? (you appear to be a content expert on this topic as well as a Wikipedia expert which is an ideal combination). Feel free to send me an e-mail through the system if you'd like to see the mentioned Word document. EMsmile (talk) 18:43, 4 March 2022 (UTC)

@EMsmile: I'm not a subject matter expert (just an engineer who is interested in climate change). You may want to post a note at Wikipedia talk:WikiProject Climate change to get a broader, more expert response. I can respond to issues on the graphics I created:

3. "Warmest years" graphic: I think that the graphic is appropriate where it is, since it tallies temperature records worldwide. The already-crowded Regional temperature section is actually less appropriate since the graphic isn't concerned with regions per se.

7. "Warmest decade" graphic: Source data is HadCRUT from Met Office (UK), with specific links in the Wikimedia file description. I didn't put a footnote in the graphic's caption here because the source provided the data but not the caption's content that can be deduced by looking at the graphed data. I think it's superfluous to cite source data in this instance; so I didn't. Separately, it shouldn't be a big worry updating data, since a new bar won't be added until 2030, and dataset variations are so small that they probably won't visually change the shape of the existing bars in the meantime.

10. The "El Nino etc" graphic: Yes, the graphic was specially made from WP:Routine calculations (adding within timewise groupings of monthly data in a Microsoft Excel spreadsheet). The sources for the El Nino/La Nina year data, and for the temperature data, are provided on the Wikimedia file description page. Most Wikipedia readers won't be interested in the source data.

Again, Wikipedia talk:WikiProject Climate change may inspire more informed responses on other issues. —RCraig09 (talk) 19:54, 4 March 2022 (UTC)

Thanks, have written at Wikipedia talk:WikiProject Climate change now. I feel bad towards the reviewer that I haven't been able to address his comments yet. Maybe I'll start by sending him your explanations about the graphics as a starting point. EMsmile (talk) 13:09, 16 March 2022 (UTC)

Update: I have now addressed all the changes that Blair Trewin had made (as listed above). I need a few more references in some cases; have asked him about that now. I have also culled some of the content that was in the last quarter of the article as it was outdated and is better available at effects of climate change and climate change.EMsmile (talk) 15:34, 17 March 2022 (UTC)

How global temperature datasets are developed from the base observations

Comment by Blair Trewin: "I think either as an addition to this section, or a new section (I prefer the latter), there should be a discussion of how global temperature datasets are developed from the base observations, and a listing of the main datasets. Reanalyses, and how they are used/not used, could also be introduced here - I see there is a Wikipedia article for 'Atmospheric Reanalysis', although it could do with some more content. (I'm not a reanalysis expert but can point you to some if you want that article strengthened)." EMsmile (talk) 14:29, 17 March 2022 (UTC)

Continued review with content expert

I am continuing the article review with content expert Blair Trewin. He sent me the following: "I think there's two significant points to make a decision on:

• Now that the IPCC temperature data set is available in a publicly accessible archive, I suggest that we should use that where appropriate, e.g. in the two tables that currently use NOAA data. If you agree I can provide the numbers.
• I think the section that's currently about satellite temperature data should instead be reframed as upper atmospheric temperature, referring to the main sources of information – satellite (with link to the article on that), reanalyses and radiosondes. This would largely draw on the material in IPCC AR6 section 2.3.1.2. If you agree I can draft some text on this.

Main other things outstanding from my perspective:

• Drafting some further text for the lead, and a few other bits where flagged
• Adding a wider range of citations more generally"

Comments/objections on these suggestions changes by anyone? If not, we'll go ahead. EMsmile (talk) 10:27, 22 March 2022 (UTC)

Comment from Blair: " I see from the talk page that there were no objections to our proposed restructurings/additions, so can go ahead with those. (The upper atmosphere part also addresses what you mentioned in the talk page under the heading 'removed content about global temperatures')." EMsmile (talk) 08:45, 30 March 2022 (UTC)

Questions about some of the graphs

About the graph in the section on warmest years: "Global area reaching record temperatures"

Comment by Blair about this graph: "This figure is about records at the regional level, not in global means - I would move it to the regional temperatures section and introduce a discussion on extremes there." Answer by RCraig09 above was: "I think that the graphic is appropriate where it is, since it tallies temperature records worldwide. The already-crowded Regional temperature section is actually less appropriate since the graphic isn't concerned with regions per se." Answer by Blair: "It's a global aggregation of regional results (i.e. it is the percentage of gridpoints which set a record in each year). It doesn't relate directly to the global average temperature which is what is being discussed at this point." Do we follow Blair's argument? EMsmile (talk) 15:18, 24 March 2022 (UTC)

The thrust of this graphic is global area. Granted, that's not exactly the same as global average, but it's much more relevant to the global viewpoint than to the distinctions between regions that is the subject of the tiny "Regional temperature changes" section. It's OK to maintain the current mix of global area and the global average temperatures "that is being discussed at this point." —RCraig09 (talk) 16:39, 24 March 2022 (UTC)

Answer from Blair: "on the first graph - if it's going to stay where it is, it probably just needs a bit of text to better link the graph to the text and explain what it's telling us - I can do this. EMsmile (talk) 08:44, 30 March 2022 (UTC)

About the graph with the caption "Colored bars show how El Niño years (red, regional warming) and La Niña years etc.

Comment by Blair about this graph: "This looks like something that's been produced specifically? (WMO has from time to time published something conceptually similar in its annual State of the Climate reports but hasn't distinguished strong from weak events). If it doesn't have a defined source then we probably need to have a link somewhere to how the strength of El Nino/La Nina events is defined". My reply to him: "The full explanation of the graph is accessible when clicking on the graph: https://commons.wikimedia.org/wiki/File:20210827_Global_surface_temperature_bar_chart_-_bars_color-coded_by_El_Ni%C3%B1o_and_La_Ni%C3%B1a_intensity.svg But I don’t understand it fully: does it explain the definition of strength for these events?" - His next reply was: "It does, although the text has a "very strong" category, which looks as if it is grouped with "strong" on the graph." EMsmile (talk) 15:30, 24 March 2022 (UTC)

In making this graphic, I followed the data categories in the original source. I didn't group "strong" with "very strong"—they're distinct colors for distinct categories. —RCraig09 (talk) 16:45, 24 March 2022 (UTC)

Answer from Blair: "on the second one - I see what's happening now - there's no 'Very strong' label for La Nina since no year has yet reached the 'Very strong' criteria for La Nina (whereas some have for El Nino). I still think it might be better to add 'Very strong' to the La Nina legend for balance even though it isn't used (yet), but don't feel strongly about this." EMsmile (talk) 08:44, 30 March 2022 (UTC)

Hi RCraig09, I am just wondering where we stand with this now? See my comments here and just above from 30 March. EMsmile (talk) 10:19, 4 May 2022 (UTC)

Absent specific substantive reasons, I will not change the graphic away from what is disclosed in the reference. In particular, I do not plan to add a 'Very strong La Nina'—"for balance", as suggested—as that would wrongly suggest such years exist. —RCraig09 (talk) 15:37, 4 May 2022 (UTC)

Overlap with global average surface temperature Global surface temperature

I noticed an overlap with the article on global average surface temperature. To start with, they use exactly the same graph in the lead. The rest of that article also seems to be a wild mixture of content that is already in other articles. Any suggestions on improving this situation? Should anything be moved from there to here or vice versa? EMsmile (talk) 09:32, 30 June 2022 (UTC)

Avoiding redirects, the correct article titles are: Global temperature record and Instrumental temperature record.

Factually, the two articles do not use the same lead graphic: File:20200324 Global average temperature - NASA-GISS HadCrut NOAA Japan BerkeleyE.svg versus File:2000+ year global temperature including Medieval Warm Period and Little Ice Age - Ed Hawkins.svg

As the hatnote to GTR implies: ITR is a ~170-year instrumental subset of GTR.

Looking at the GTR table of contents, it does not seem "wild", but is reasonably ordered by time periods involved. —RCraig09 (talk) 15:20, 30 June 2022 (UTC)

I'm sorry for the mixup: I wasn't referring to Global temperature record. I was referring to Global surface temperature, and they do have the same image in the lead. I saw it mentioned for the first time in this edit of yours. You added there [[Global surface temperature|global average surface temperatures]]. So you linked the words "global average surface temperatures" to Global surface temperature. These are two separate articles however:

• Global surface temperature
• global average surface temperature (i.e. it redirects to Global temperature record) EMsmile (talk) 09:24, 1 July 2022 (UTC)

User:RCraig09 just wondering if you have overlooked this or had decided to let it be for now. I'd like to see if we can resolve this as there seems to be overlap between Global surface temperature and Instrumental temperature record, e.g. they both use the same image in the lead. "Global average surface temperature" on the other hadn redirects to Global temperature record. I don't see how "Global average surface temperature" should be different to "Global surface temperature". Should I rather bring this up on the talk page of WikiProject Climate change? EMsmile (talk) 16:54, 21 September 2022 (UTC)

— I corrected the clearly wrong redirect so that it's now GAST --> GST=GMST=GAST.

— GST and ITR are distinct, though overlapping. GST is in principle the temperature itself, distinct from ways temperature is measured (viz., with instruments). Each article can be considered separately for its content, through ordinary editing.

— It's very much a secondary issue that GST and ITR happen to have the same lead graphic; it would be odd to show a picture of a record book in the lead of ITR. —RCraig09 (talk) 19:39, 21 September 2022 (UTC)

OK, glad that redirect is fixed now. I'll start a conversation on WikiProject Climate Change because I think given our limited resources we should streamline this article with Global surface temperature to avoid overlap. EMsmile (talk) 08:20, 22 September 2022 (UTC)

P.S. Funny how you like point out which of my suggestions are "primary" and "secondary" issues (you do this regularly when reacting to my comments). Yes, I agree, it is indeed a minor issue but so what? At the end of the day, it's the sum of improving "minor issues" on Wikipedia that makes it a high quality resource. If someone went around and only corrected typos ("a minor issue"), I would still be grateful to them as every little bit counts. - I do think that the image in the lead should be unique to the article. MOS:LEADIMAGE says the image in the lead is there "to give readers visual confirmation that they've arrived at the right page". EMsmile (talk) 08:20, 22 September 2022 (UTC)

The point in pointing out that the same-lead-graphic issue is secondary, is that it is apparently not based on any objective Wikipedia policy or guideline; MOS:LEADIMAGE does not state or imply that articles must or should have mutually distinct lead images. My comment was not personal. That you "think" lead images should be unique is not only your personal subjective belief, but is a idea that you admit is "a minor issue". Objectively, it's altogether reasonable—even expected—that "X" and "Record of X" might the same lead image. —RCraig09 (talk) 18:18, 22 September 2022 (UTC)

Question about the first figure (correct base period to use?)

Five datasets over different time periods. . . . Update: changed on 2023-07-23 to six datasets normalized to pre-industrial levels (1850-1900 average)

Dear all, I'm not a climate expert, but an astronomer with keen interest in this topic. I struggled over the first figure in this article that gives the impression that global temperatures have "only" increased by less than 1 degree so far. This is of course due to the use of the very awkward base period 1950-1980 (see also point 13 of the expert review above). I would strongly suggest to use the same base period as the IPCC (and most other publications that I have seen on this topic), i.e. the "pre-industrial" time with instrumental temperature record, 1850-1900 (see. e.g. Fig. SPM-1 in the IPCC's AR6 report): https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_SPM_final.pdf -- if you agree, I'd be happy to update the figure (or if the creator of that figure is still active, perhaps they can speak up). Regards, Ileo (talk) 10:32, 27 July 2022 (UTC)

Thanks, seems like an important point you're making here. I copy here Point 13 from the expert review as I had moved your comment to the bottom of the page: "Either here, or in the 'Temperature anomaly' article, there needs to be a discussion of which baseline periods are in use, the purposes they serve, and why the choice of baseline has no impact on long-term trends." EMsmile (talk) 11:21, 27 July 2022 (UTC)

Preliminarily: there is no "correct" base period for temperature anomalies; they are reference periods. More to the point here, only two of the five datasets go all the way back to 1850, so it's impossible to adjust all five datasets to the IPCC 1850-1900 "pre-industrial" reference period. Oddly, "pre-industrial", literally, is before 1850 anyway, so scientifically the IPCC reference period isn't that distinctly authoritative. A main purpose of this graphic is to convey the high correlation among numerous authoritative instrumental temperature record datasets, a purpose that would be thwarted if there were only two datasets. In any event, it's clear from the chart that the change isn't less than 1 °C. —RCraig09 (talk) 19:33, 27 July 2022 (UTC)

OK, fair enough but I think the expert reviewer was right when he said "Either here, or in the 'Temperature anomaly' article, there needs to be a discussion of which baseline periods are in use, the purposes they serve, and why the choice of baseline has no impact on long-term trends." Currently the word baseline appears only once in the entire article. I am not sure what the best reference would be to use to explain a bit about the issue of baselines. The article Temperature anomaly doesn't mention the word "baseline" at all. Pinging Ileo. EMsmile (talk) 07:41, 28 July 2022 (UTC)

Temperature anomaly already recites "A temperature anomaly is measured against a reference value or long-term average.[1][2]" The NOAA reference explains anomalies quite thoroughly. —RCraig09 (talk) 14:55, 28 July 2022 (UTC)

P.S. In August 2022, I made substantial additions to the Temperature anomaly itself. I think more detail isn't warranted here. —RCraig09 (talk) 03:10, 22 September 2022 (UTC)

I've made some small edits to the article and the caption of the lead image to clarify this issue of reference point. I think it's important so that it becomes clearer why the data in the graph starts off with negative values in 1850. EMsmile (talk) 09:04, 23 June 2023 (UTC)

Update: This week I discovered the Met Office has collected six datasets and normalized them to the presumptive "pre-industrial" temperature, 1850-1900 average. The chart is now updated to be based on that cooler reference period, so the change of more than 1 °C is now evident. —RCraig09 (talk) 20:57, 13 July 2023 (UTC)

that's good but I think we should update the caption accordingly. Currently it says: "(In this chart, the "0" value is what is considered the "pre-industrial" temperature level.)" I don't think we can expect everyone to know what pre-industrial means (I would have guessed it means e.g. average of 1800-1850). Would you agree to change the caption to something like this: In this chart, the "0" value is what is considered the "pre-industrial" temperature level, which is the average of the years 1850 to 1900. or In this chart, the "0" value is the average of the years 1850 to 1900 which is commonly called the "pre-industrial" temperature level? EMsmile (talk) 07:54, 14 July 2023 (UTC)

 Done —RCraig09 (talk) 18:03, 17 July 2023 (UTC)