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I am new to statistics but scraped data from NOAA's web site to plot CO2 level vs time. Is there a good statistical technique to extrapolate past limit of data X axis to near future like 2050? One could cont the curve I guess in a polynomial function. This is a super relevant question as climate change is dangerous.

**CO2 level from NOA**

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  • $\begingroup$ An exponential function is commonly used, as in James Phillips' answer below. But there is an extensive scientific literature on forecasting CO2 emissions that also takes into account different scenarios of economic and population growth, so those papers would probably worth looking into. $\endgroup$ – mkt - Reinstate Monica Jun 24 '19 at 6:37
  • $\begingroup$ I want to try to look those up. But if you have any citations on hand, , feel free to comment. $\endgroup$ – Cliff Oct 3 '19 at 12:20
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The NOAA site has the Moana Loa observatory atmospheric CO2 data directly downloadable as text at ftp://aftp.cmdl.noaa.gov/products/trends/co2/co2_mm_mlo.txt - no scraping needed. After removing a few "-99.99" values for "average CO2" that are stated to represent missing data I was easily able to perform an equation search on just over 350 known, named equations with three or less fitted parameters. The search purpose was to find an equation that both fit well and should also extrapolate well due to simplicity. My equation search turned up the Standard Vapor Pressure equation "CO2 = exp(a + (b/year) + c*log(year))" as an excellent candidate, with parameters a = -1.9342529555687474E+03, b = 4.3355326963670307E+05 and c = 2.2673459584210687E+02 yielding RMSE = 2.216 and R-squared = 0.993, here is error plot of this fit with extrapolation of this equation to the year 2040.

error

extrapolation

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  • $\begingroup$ I was wondering if you could give us the citation for those 350 equations that you used? or name the database or repository? thx "I used my zunzun.com open source Python online curve and surface fitting web site, it has a "function finder" for equation search". – James Phillips 11 hours ago $\endgroup$ – Cliff Jun 24 '19 at 13:56

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