Fabrice.Lambert

Your new graph at Paleoclimatology

Hi, welcome to Wikipedia! I noticed you changed the graph at the Paleoclimatology page. The old graph always puzzled me because at the left-side of the graph, year zero which is supposedly today, the ppm of CO2 is not at today's level. What year actually is year zero?

If you look at the old graph, you will see which pages still use the old graph and once I know what year zero is (and if you will reverse the time axis), I'd like to update all the pages that use the old graph. Note in the old graph file history, 30 November 2013, that someone reversed the time axis, maybe you could do that too, because it's kind of confusing unless noted in the caption. Best Wishes, I like to see new climate-change graphs and have uploaded a few from NOAA! Raquel Baranow (talk) 19:11, 31 March 2016 (UTC)

ANSWER: Hi! Sorry for replying within your message, I couldn't find a reply button. I've tried to be as close as possible to the old figure with the new one, but indeed I have included this inaccuracy. The unit of the x-axis is in ka BP, which are thousands of years before 1950 (according to the radiocarbon standard). So the year zero is actually 1950. However, the CO2 data only starts at age 137 (i.e. around 1800). Thus the CO2 values are still on pre-industrial levels. All of this is not visible on the figure because of the resolution (lots of data in a small figure). The convention to go from right to left is controversial and constantly debated. It follows the logic that numbers should get larger when you move to the right and since we have Age on the x-axis you go back in time. A correct alternative would be to have time in negative numbers going from left to right and year zero on the right. Some people prefer one, others the other. I have followed the current convention in this type of figure in the scientific literature.--Fabrice.Lambert (talk) 21:51, 31 March 2016 (UTC)