Nathan wrote:

>The differencing is forward differencing.

Forward differencing is this? :

\$diffforward(q_i):=q_{i+1}-q_i\$

>Then the smoothed data are differenced (i.e. differences between successive smooth months are computed.

So you think now this should probably be different?

With

>The iteration over months in the code had puzzled me.

you mean that part?:

`for (m in 1:12) {´

`ii <- is.element(mm, m) ´

`#print(c(m,length(ii),sum(ii),length(diff12[m,]),length(diff(x[ii]))))´

`diff12[m,] <- diff(x[ii])´

(John wrote that I should use quotation marks for code but I don't no why the quotation marks are here still visible)

I don't know rcode but it looks to me that the differencing is done in that (probably again built-in) function "diff"
and the for loop seems is here only for going through the array of monthly values. ??

So it seems to me the big question is now, what is "diff" ? Is it "forward differencing?"

The green dashed curve in Fig. 2 is the resulting smoothed-and-differenced CO2 curve, whose magnitude is given by the right-hand scale.

If I look at the yearly differences in the co2 curve then on the right hand scale they are in the range of 2-4 so this would still not go together with the factor of 1/12.