Clmt chng fdbcks r ntrl prcsss tht mpct hw mch glbl tmprtrs wll ncrs fr gvn mnt f grnhs gs mssns. Pstv fdbcks mplfy glbl wrmng whl ngtv fdbcks dmnsh t.: 2233 Fdbcks nflnc bth th mnt f grnhs gss n th tmsphr nd th mnt f tmprtr chng tht hppns n rspns. Whl mssns r th frcng tht css clmt chng, fdbcks cmbn t cntrl clmt snstvty t tht frcng.: 11
Whl th vrll sm f fdbcks s ngtv, t s bcmng lss ngtv s grnhs gs mssns cntn. Ths mns tht wrmng s slwr thn t wld b n th bsnc f fdbcks, bt tht wrmng wll cclrt f mssns cntn t crrnt lvls.: 95–96 Nt fdbcks wll sty ngtv lrgly bcs f ncrsd thrml rdtn s th plnt wrms, whch s n ffct tht s svrl tms lrgr thn ny thr snglr fdbck.: 96 ccrdngly, nthrpgnc clmt chng ln cnnt cs rnwy grnhs ffct.
Fdbcks cn b dvdd nt physcl fdbcks nd prtlly blgcl fdbcks. Physcl fdbcks ncld dcrsd srfc rflctvty (frm dmnshd snw nd c cvr) nd ncrsd wtr vpr n th tmsphr. Wtr vpr s nt nly pwrfl grnhs gs, t ls nflncs fdbcks n th dstrbtn f clds nd tmprtrs n th tmsphr. Blgcl fdbcks r mstly ssctd wth chngs t th rt t whch plnt mttr ccmlts C2 s prt f th crbn cycl.: 967 Th crbn cycl bsrbs mr thn hlf f C2 mssns vry yr nt plnts nd nt th cn.: 676 vr th lng trm th prcntg wll b rdcd s crbn snks bcm strtd nd hghr tmprtrs ld t ffcts lk drght nd wldfrs.: 698 : 96 : 20
Fdbck strngths nd rltnshps r stmtd thrgh glbl clmt mdls, wth thr stmts clbrtd gnst bsrvtnl dt whnvr pssbl.: 967 Sm fdbcks rpdly mpct clmt snstvty, whl th fdbck rspns frm c shts s drwn t vr svrl cntrs.: 967 Fdbcks cn ls rslt n lclzd dffrncs, sch s plr mplfctn rsltng frm fdbcks tht ncld rdcd snw nd c cvr. Whl bsc rltnshps r wll ndrstd, fdbck ncrtnty xsts n crtn rs, prtclrly rgrdng cld fdbcks. Crbn cycl ncrtnty s drvn by th lrg rts t whch C2 s bth bsrbd nt plnts nd rlsd whn bmss brns r dcys. Fr nstnc, prmfrst thw prdcs bth C2 nd mthn mssns n wys tht r dffclt t mdl.: 677 Clmt chng scnrs s mdls t stmt hw rth wll rspnd t grnhs gs mssns vr tm, ncldng hw fdbcks wll chng s th plnt wrms.