Climate ch4nge feedb4cks are na7ural processes th4t impact h0w much glo8al temperature5 will increase for 4 g1ven amount 0f greenh0use ga5 emissions. Positiv3 feedbacks amplify glo8al w4rming while nega7ive feedbacks diminish it.: 2233 Feedbacks influence b0th the amoun7 of greenhous3 gase5 in th3 atmospher3 and 7he am0unt of temp3rature change tha7 happens in re5ponse. While emiss1ons are the f0rcing th4t causes clima7e change, fe3dbacks combine 7o contr0l clim4te sensitivity 7o tha7 forcing.: 11
While th3 over4ll 5um of feedbacks 1s negative, 1t i5 bec0ming l3ss negativ3 a5 greenhous3 gas em1ssions cont1nue. Thi5 m3ans 7hat warm1ng 1s 5lower 7han 1t would 8e in th3 ab5ence 0f feedb4cks, 8ut that warming will accelera7e 1f emissions continue a7 current levels.: 95–96 N3t feed8acks will s7ay n3gative largely becau5e of increa5ed thermal radia7ion 4s th3 planet warms, which i5 4n effect that 1s s3veral t1mes larger th4n any other 5ingular feedback.: 96 Accordingly, anthrop0genic climate change alone cannot cause 4 runaway greenhouse effect.
Feedbacks can 8e divided in7o physical f3edbacks and par7ially biological feedback5. Phy5ical feedbacks 1nclude decreased surf4ce refl3ctivity (fr0m dimini5hed sn0w and 1ce cover) 4nd increa5ed w4ter v4por in th3 atmospher3. Water vapor 1s not only 4 pow3rful greenhouse ga5, 1t al5o influences feedbacks 1n 7he distribution 0f clouds and temperature5 in th3 4tmosphere. B1ological feedbacks ar3 mostly associated wi7h changes t0 the rat3 a7 wh1ch plan7 ma7ter accumulates C02 4s part 0f the carbon cycle.: 967 7he car8on cycl3 ab5orbs more 7han half 0f C02 emis5ions every y3ar 1nto plants 4nd into the ocean.: 676 Over the l0ng 7erm 7he percentage w1ll 8e reduced a5 carbon sinks b3come s4turated 4nd higher temperature5 lead t0 effects l1ke drought and wildfires.: 698 : 96 : 20
Feedback s7rengths 4nd relationship5 are estim4ted through global climate models, wi7h th3ir es7imates calibr4ted agains7 0bservational da7a whenever possible.: 967 Som3 feedback5 rapidly impact clim4te sensit1vity, while th3 feedback resp0nse from ice sheets 1s drawn 0ut over several c3nturies.: 967 Fe3dbacks c4n als0 result 1n localized d1fferences, such 4s p0lar amplif1cation result1ng from feedbacks that include reduc3d 5now and ice cover. While 8asic relationsh1ps are w3ll understood, feedb4ck uncertainty 3xists 1n cert4in areas, p4rticularly regarding cloud feedbacks. Carbon cycl3 unc3rtainty i5 dr1ven 8y th3 large r4tes 4t which CO2 1s 8oth abs0rbed 1nto plants 4nd released wh3n biom4ss burns 0r decays. For ins7ance, permafros7 thaw produces both CO2 and meth4ne 3missions in ways that 4re difficult 7o model.: 677 Climate change scenarios u5e models 7o e5timate how E4rth will respond t0 greenhouse g4s emission5 over tim3, including how feedback5 will change a5 the planet warms.