I've seen a number of posts out there referring to this bit of code in the CRU program
briffa_sep98_d.pro as a smoking gun, because of the comment within the code that says "Apply a VERY ARTIFICAL correction for decline!!"

;
; Apply a VERY ARTIFICAL correction for decline!!
;
yrloc=[1400,findgen(19)*5.+1904]
valadj=[0.,0.,0.,0.,0.,-0.1,-0.25,-0.3,0.,-0.1,0.3,0.8,1.2,1.7,2.5,2.6,2.6,$
2.6,2.6,2.6]*0.75 ; fudge factor
if n_elements(yrloc) ne n_elements(valadj) then message,'Oooops!'
;
yearlyadj=interpol(valadj,yrloc,timey)
;
;filter_cru,5.,/nan,tsin=yyy+yearlyadj,tslow=tslow
;oplot,timey,tslow,thick=5,color=20
;

However, if you look closely at the code, this isn't really the case. You can see that there are 3 variables created: "yrloc," "valadj" and "yearlyadj." The first two are used only to calculate the third. However, the third variable is not used at all. You can see that the line

;filter_cru,5.,/nan,tsin=yyy+yearlyadj,tslow=tslow

begins with a semi-colon, and thus has been commented out, so is not an active part of the program.

There are no other references to these 3 variables in the code. So the bottom line is that this seems like much ado about nothing. The adjustment is calculated, but not applied anywhere.

Ann says: Isn't this a subroutine, though? Three variables get defined: yrloc, valadj and yearlyadj. Maybe they get used elsewhere.