File talk:All palaeotemps.svg

Phanerozoic temperature curve exaggerated?

Comparing the temperature curve for the Phanerozoic as given in fig. 4 in Royer et al. (2004) with the temperature curve for the Phanerozoic on the backside, the curve seems to be exaggerated by a factor of two. How come? --Gretarsson (talk) 19:36, 1 March 2015 (UTC)

It's in the description under Data, Panel 1, paragraph 2. Could be clearer though; I'll add some words.--Gergyl (talk) 22:09, 1 March 2015 (UTC)

Done. The challenge is that, though widely interpreted as such, the Royer/Veizer temperatures are not global estimates. Certainly Royer et al do not represent them as such; they repeatedly refer to them as "low-latitude" (which I write less technically as "tropical and sub-tropical"). It follows that to view them as global estimates, at a minimum some sort of globalising factor is warranted, akin to the polar amplification factor applied to the polar series. A weakness is that my choice (2.0) is somewhat arbitrary and unsupported, but without it Royer/Veizer becomes problematic in the context, even misleading. For example, much of the Cretaceous is reported* to have been as warm or warmer than the Eocene, but without magnification Royer/Veizer would show it as way cooler. And in the Paleogene (abt 23-66 My), which Royer/Veizer also covers, the misfit with e.g. Hansen/Zachos would become very large (about an 8°C offset, or a factor of more than four on the anomalies). A reference to cite for the adjustment would be nice, and I'd be very happy if you can locate one. Dana Royer, when asked, offered the not very helpful "just view it qualitatively" (as ref'd).

* e.g. see the benthic δ18O record in Friedrich, Norris & Erbacher (2012). Evolution of middle to Late Cretaceous oceans—A 55 my record of Earth's temperature and carbon cycle. Geology, 40(2), 107-110

--Gergyl (talk) 02:58, 2 March 2015 (UTC)

Thanks a lot for the quick answer. I see the problem. Seems that it is still generally difficult to tie a point in the more distant earth’s history to an absolute temperature value... Cheers! --Gretarsson (talk) 09:43, 2 March 2015 (UTC)

need something more clear and compelling

@Perhelion: @Glen Fergus: I very much appreciate your work on this, but I wonder if you can produce something that is simultaneously clearer and more compelling? I want a single graphic that will jump off the page and help me predict by eye what's likely to happen in the next century if appropriate action is not taken.

I'm thinking of something with perhaps only 2 or 3 periods rather than 5 with something like the following characteristics:

• The latter period would include only the most recent 100 or 200 years showing a fairly stable period starting to rise rather dramatically in the last quarter or so of that period -- enough so a naive lay person could estimate by eye the rate of increase, with a clear demarcation between actual measurements and forecasts.
• The middle period might include a mark for the appearance of humans plus another event or two that people would recognize and understand. Or maybe eliminate this middle period.
• The first period would go back 500 million years before the present, as does the current plot, and end sometime after the extinction of dinosaurs.

To me, the present plot provides simultaneously too much and not enough detail. After I stared at it long enough and read the summary, I understood that the vertical scale is deviation from the 1960-1990 global average surface air temperature. However, I have no substantive intuition about thousands and millions of years before the present (2015 CE). Terms like pliocene mean nothing to me. (I'm an engineer with a PhD in statistics, by the way.) I could relate to events like "first human" and "dinosaurs extinct".

Also, it would help if a plot like this had its own Wikipedia article with clear, concise and compelling documentation of a plot like this. I think it would help if such a Wikipedia article would discuss what's likely to happen to the polar ice caps, e.g., at what temperature would we expect them to completely disappear after however many decades and the resulting rise in sea level, etc. Details on the resulting rise in sea level might be left to other sources, but a sentence or two on that with a link would be great, I think.

I know I'm asking a lot, and neither of you may have time for anything like this. However, I think a plot like this and a Wikipedia article explaining it in simple terms that a lay person could understand could go a long way toward bridging the media hype explained in, e.g., John Cook Visually depicting the disconnect between climate scientists, media and the public, 1 August 2010. Sadly, I hardly know enough to be able to produce this myself, and I want to use something like this in other work I'm doing.

Thanks, DavidMCEddy (talk) 03:27, 25 March 2019 (UTC)

Addition of spurious predictions

Your two predictions are based on the ludicrous RCP 8.5 scenarios. The rest of the data is historical. The predictions are out of place because everything else is based on measurement (however inaccurate) whereas the predictions are based on estimates of both CO2 and climate sensitivity. Greglocock (talk) 04:03, 6 June 2019 (UTC)

Explain caption

The picture contains indications like "(x2.0)" and "(x0.5)" which are not clear and not explained in the page. — Preceding unsigned comment was added by 2A01:CB08:42:9500:329C:23FF:FEA2:DF4F (talk) 11:44, 28 May 2022 (UTC)