Wikipedia:Reference desk/Archives/Science/2018 August 25

= August 25 =

Source of a basemap
Greetings, does someone have an idea where the underlying information of File:Peru physical map.svg might come from? Jo-Jo Eumerus (talk, contributions) 07:30, 25 August 2018 (UTC)
 * According to the file description (on commons), it is the "author's own work"; you can contact the author here: https://commons.wikimedia.org/wiki/User:Urutseg —2606:A000:1126:4CA:0:98F2:CFF6:1782 (talk) 01:23, 27 August 2018 (UTC)

Range of Likely Rise in GMST
The second paragraph of the global warming article reports "Climate model projections summarized in the report indicated that during the 21st century, the global surface temperature is likely to rise a further 0.3 to 1.7 °C to 2.6 to 4.8 °C depending on the rate of greenhouse gas emissions." What is the significance of four temperatures in defining this range? Shouldn't a range be defined by two temperatures and a confidence level? Also, where do theese numbers come from in the source? --Tag (talk) 15:35, 25 August 2018 (UTC)
 * It has to be 4 because how much of the 2001 carbon humans decide to burn by 2101 and how front-loaded or back-loaded and how much they slash-and-burn, desertify and plant trees and stuff is hard to pin down. Sagittarian Milky Way (talk) 17:32, 25 August 2018 (UTC)
 * I don't think this answers my question. Can you elaborate specifically on what each of the four numbers means and where I can find them in the source? --Tag (talk) 18:01, 25 August 2018 (UTC)
 * The first number is fast emissions cutting timeline, low estimate; second is fast emissions cutting timeline, high estimate; third is humans treat the Earth like crap timeline, low estimate; fourth is humans treat the Earth like crap timeline, high estimate. Probably. This is useful because it provides more information than just 2 numbers, it shows what's scientific uncertainty and what's "we don't know what humans will do in the future". Sagittarian Milky Way (talk) 20:00, 25 August 2018 (UTC)
 * The source is likely to be IPCC5. I'm not going to bother to look through it to find out. As SMW says, the 4 numbers encapsulate different CO2 emissions rates, and different estimates of the sensitivity of GMST to CO2 concentration. Specifically the higher numbers are based on RCP 8.5 which the frauds called 'business as usual'. Among other assumptions is that the population of Nigeria will grow to 1.5 billion (one eighth of the then predicted population), giving the same population density for the entire country as the Vatican City is at the moment https://link.springer.com/article/10.1007%2Fs10584-011-0148-z. Really? Here's an article with a graph that agrees with the numbers in question. Overplotting the actual data would be an interesting exercise. https://medium.com/@davidfurphy/what-on-earth-is-an-rcp-bbb206ddee26  Greglocock (talk) 21:16, 25 August 2018 (UTC)
 * The abbreviation "GMST" means "Greenwich Mean Sidereal Time".  It obviously doesn't mean that here.   What does it mean? 151.227.20.35 (talk) 07:08, 26 August 2018 (UTC)
 * Global Mean Surface Temperature. Mikenorton (talk) 07:21, 26 August 2018 (UTC)


 * The figures are on p. 89: Under the assumptions of the concentration-driven RCPs, GMSTs for 2081–2100, relative to 1986–2005 will likely be in the 5 to 95% range of the CMIP5 models; 0.3°C to 1.7°C (RCP2.6), 1.1 to 2.6°C (RCP4.5), 1.4°C to 3.1°C (RCP6.0), 2.6°C to 4.8°C (RCP8.5) (see Table TS.1). With high confidence, the 5 to 95% range of CMIP5 is assessed as likely rather than very likely based on the assessment of TCR (see TFE.6).


 * Incidentally, the word "Nigeria" does not appear in the reference Greg gives, so I'd take his answer with a barrel of salt. HenryFlower 21:55, 28 August 2018 (UTC)


 * Salt supplied http://science.sciencemag.org/content/346/6206/234.full Greglocock (talk) 22:42, 30 August 2018 (UTC)