IPCC:AR6/WGI/Chapter-4 - Revision history

Laura at 08:34, 22 May 2026

2026-05-22T08:34:52Z

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			{{ChapterNavigation
			\| cover = Cover-WGI.jpg
			\| reporturl = IPCC:AR6/WGI
			\| reporttitle = WGI
			\| prevurl = IPCC:AR6/WGI/Chapter-3
			\| nexturl = IPCC:AR6/WGI/Chapter-5
			}}

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Laura: Laura moved page IPCC:Wg1:Chapter:Chapter-4 to IPCC:AR6/WGI/Chapter-4 without leaving a redirect

2026-05-18T16:17:28Z

Laura moved page IPCC:Wg1:Chapter:Chapter-4 to IPCC:AR6/WGI/Chapter-4 without leaving a redirect

← Older revision	Revision as of 16:17, 18 May 2026
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Laura: /* 4.5.1.6.2 Zonal wind and westerly jets */

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4.5.1.6.2 Zonal wind and westerly jets

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	<span id="zonal-wind-and-westerly-jets"></span>		<span id="zonal-wind-and-westerly-jets"></span>
	===== ''4.5.1.6.2 Zonal wind and westerly jets'' =====		===== 4.5.1.6.2 Zonal wind and westerly jets =====

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	===== 4.5.1.6.3 Storm tracks =====		===== 4.5.1.6.3 Storm tracks =====

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Laura: /* Chapter 4: Future Global Climate: Scenario-based Projections and Near-term Information */

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Chapter 4: Future Global Climate: Scenario-based Projections and Near-term Information

← Older revision		Revision as of 14:03, 13 May 2026
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	<div id="chapter-authors"></div>		<div id="chapter-authors"></div>

	Coordinating Lead Authors:		'''Coordinating Lead Authors:'''

	June-Yi Lee (Republic of Korea), Jochem Marotzke (Germany)		June-Yi Lee (Republic of Korea), Jochem Marotzke (Germany)

	Lead Authors:		'''Lead Authors:'''

	Govindasamy Bala (India/United States of America), Long Cao (China), Susanna Corti (Italy), John P. Dunne (United States of America), Francois Engelbrecht (South Africa), Erich Fischer (Switzerland), John C. Fyfe (Canada), Christopher Jones (United Kingdom), Amanda Maycock (United Kingdom), Joseph Mutemi (Kenya), Ousmane Ndiaye (Senegal), Swapna Panickal (India), Tianjun Zhou (China)		Govindasamy Bala (India/United States of America), Long Cao (China), Susanna Corti (Italy), John P. Dunne (United States of America), Francois Engelbrecht (South Africa), Erich Fischer (Switzerland), John C. Fyfe (Canada), Christopher Jones (United Kingdom), Amanda Maycock (United Kingdom), Joseph Mutemi (Kenya), Ousmane Ndiaye (Senegal), Swapna Panickal (India), Tianjun Zhou (China)

	Contributing Authors:		'''Contributing Authors:'''

	Sebastian Milinski (Germany), Kyung-Sook Yun (Republic of Korea), Kyle Armour (United States of America), Nicolas Bellouin (United Kingdom/France), Ingo Bethke (Norway/Germany), Michael P. Byrne (United Kingdom /Ireland), Christophe Cassou (France), Deliang Chen (Sweden), Annalisa Cherchi (Italy), Hannah M. Christensen (United Kingdom), Sarah L. Connors (France/United Kingdom), Alejandro Di Luca (Australia, Canada/Argentina), Sybren S. Drijfhout (The Netherlands), Christopher G. Fletcher (Canada/United Kingdom, Canada), Piers Forster (United Kingdom), Javier García-Serrano (Spain), Nathan P. Gillett (Canada), Darrell S. Kaufmann (United States of America), David P. Keller (Germany/United States of America), Ben Kravitz (United States of America), Hongmei Li (Germany/China), Yongxiao Liang (Canada/China), Andrew H. MacDougall (Canada), Elizaveta Malinina (Canada/Russian Federation), Matthew Menary (France/United Kingdom), William J. Merryfield (Canada/United States of America), Seung-Ki Min (Republic of Korea), Zebedee R.J. Nicholls (Australia), Dirk Notz (Germany), Brodie Pearson (United States of America/United Kingdom), Matthew D. K. Priestley (United Kingdom), Johannes Quaas (Germany), Aurélien Ribes (France), Alex C. Ruane (United States of America), Jean-Baptiste Sallée (France), Emilia Sanchez-Gomez (France/Spain), Sonia I. Seneviratne (Switzerland), Aimée B. A. Slangen (The Netherlands), Chris Smith (United Kingdom), Malte F. Stuecker (United States of America/Germany), Ranjini Swaminathan (United Kingdom/India), Peter W. Thorne (Ireland/ United Kingdom), Katarzyna B. Tokarska (Switzerland/Poland), Matthew Toohey (Canada, Germany/Canada), Andrew Turner (United Kingdom), Danila Volpi (Italy), Cunde Xiao (China), Giuseppe Zappa (Italy)		Sebastian Milinski (Germany), Kyung-Sook Yun (Republic of Korea), Kyle Armour (United States of America), Nicolas Bellouin (United Kingdom/France), Ingo Bethke (Norway/Germany), Michael P. Byrne (United Kingdom /Ireland), Christophe Cassou (France), Deliang Chen (Sweden), Annalisa Cherchi (Italy), Hannah M. Christensen (United Kingdom), Sarah L. Connors (France/United Kingdom), Alejandro Di Luca (Australia, Canada/Argentina), Sybren S. Drijfhout (The Netherlands), Christopher G. Fletcher (Canada/United Kingdom, Canada), Piers Forster (United Kingdom), Javier García-Serrano (Spain), Nathan P. Gillett (Canada), Darrell S. Kaufmann (United States of America), David P. Keller (Germany/United States of America), Ben Kravitz (United States of America), Hongmei Li (Germany/China), Yongxiao Liang (Canada/China), Andrew H. MacDougall (Canada), Elizaveta Malinina (Canada/Russian Federation), Matthew Menary (France/United Kingdom), William J. Merryfield (Canada/United States of America), Seung-Ki Min (Republic of Korea), Zebedee R.J. Nicholls (Australia), Dirk Notz (Germany), Brodie Pearson (United States of America/United Kingdom), Matthew D. K. Priestley (United Kingdom), Johannes Quaas (Germany), Aurélien Ribes (France), Alex C. Ruane (United States of America), Jean-Baptiste Sallée (France), Emilia Sanchez-Gomez (France/Spain), Sonia I. Seneviratne (Switzerland), Aimée B. A. Slangen (The Netherlands), Chris Smith (United Kingdom), Malte F. Stuecker (United States of America/Germany), Ranjini Swaminathan (United Kingdom/India), Peter W. Thorne (Ireland/ United Kingdom), Katarzyna B. Tokarska (Switzerland/Poland), Matthew Toohey (Canada, Germany/Canada), Andrew Turner (United Kingdom), Danila Volpi (Italy), Cunde Xiao (China), Giuseppe Zappa (Italy)

	Review Editors:		'''Review Editors:'''

	Krishna Kumar Kanikicharla (Qatar/India), Vladimir Kattsov (Russian Federation), Masahide Kimoto (Japan)		Krishna Kumar Kanikicharla (Qatar/India), Vladimir Kattsov (Russian Federation), Masahide Kimoto (Japan)

	Chapter Scientists:		'''Chapter Scientists:'''

	Sebastian Milinski (Germany), Kyung-Sook Yun (Republic of Korea)		Sebastian Milinski (Germany), Kyung-Sook Yun (Republic of Korea)
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	<div id="chapter-citation"></div>		<div id="chapter-citation"></div>

	This chapter should be cited as:		'''This chapter should be cited as:'''

	Lee, J.-Y., J. Marotzke, G. Bala, L. Cao, S. Corti, J.P. Dunne, F. Engelbrecht, E. Fischer, J.C. Fyfe, C. Jones, A. Maycock, J. Mutemi, O. Ndiaye, S. Panickal, and T. Zhou, 2021: Future Global Climate: Scenario-Based Projections and Near-Term Information. In ''Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change'' [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 553–672, doi: [https://doi.org/10.1017/9781009157896.006 10.1017/9781009157896.006] .		Lee, J.-Y., J. Marotzke, G. Bala, L. Cao, S. Corti, J.P. Dunne, F. Engelbrecht, E. Fischer, J.C. Fyfe, C. Jones, A. Maycock, J. Mutemi, O. Ndiaye, S. Panickal, and T. Zhou, 2021: Future Global Climate: Scenario-Based Projections and Near-Term Information. In ''Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change'' [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 553–672, doi: [https://doi.org/10.1017/9781009157896.006 10.1017/9781009157896.006] .

imported>Design: /* References */

2026-05-11T08:41:36Z

References

Show changes

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	Before the industrial period, explosive volcanic eruptions were the largest source of forced climate variability globally on interannual to centennial time scales ( [[IPCC:Wg1:Chapter:Chapter-2#2.2\|Section 2.2]] ). While usually omitted from scenarios used for future climate projections, as they are unpredictable, volcanic eruptions have the potential to influence future climate on multi-annual to decadal time scales and affect many climatic impact drivers (as defined in Sections 12.1 and 12.3). Since AR5, more comprehensive paleo evidence and observations, as well as improved modelling have advanced understanding of the climate response to past volcanic eruptions. Building on multiple chapter assessments, this box synthesizes how volcanic eruptions affect climate and considers implications of possible future events.		Before the industrial period, explosive volcanic eruptions were the largest source of forced climate variability globally on interannual to centennial time scales ( [[IPCC:Wg1:Chapter:Chapter-2#2.2\|Section 2.2]] ). While usually omitted from scenarios used for future climate projections, as they are unpredictable, volcanic eruptions have the potential to influence future climate on multi-annual to decadal time scales and affect many climatic impact drivers (as defined in Sections 12.1 and 12.3). Since AR5, more comprehensive paleo evidence and observations, as well as improved modelling have advanced understanding of the climate response to past volcanic eruptions. Building on multiple chapter assessments, this box synthesizes how volcanic eruptions affect climate and considers implications of possible future events.

	~~'''~~'''How frequent are volcanic eruptions?'''~~'''~~		'''How frequent are volcanic eruptions?'''

	Proxy records show that large volcanic eruptions with effective radiative forcing (ERF) more negative than –1 W m <sup>–2</sup> occurred on average twice a century throughout the last 2500 years, the most recent being Pinatubo in 1991 ( [[IPCC:Wg1:Chapter:Chapter-2#2.2.2\|Section 2.2.2]] ). About eight larger eruptions (ERF stronger than –5 W m <sup>–2</sup> ) also occurred during this period (Figure 2.2), notably Tambora about 1815 and Samalas about 1257. A Samalas-type eruption may occur one to two times per millennium on average ( [[#Newhall--2018\|Newhall et al., 2018]] ). Typically, three in every four centuries have experienced at least one eruption stronger than –1 W m <sup>–2</sup> (Pinatubo or larger). The volcanic aerosol burden was 14% lower during the 20th century compared to the average of the preceding 24 centuries ( [[IPCC:Wg1:Chapter:Chapter-2#2.2.2\|Section 2.2.2]] ), whereas the 13th century was among the most volcanically active, with four eruptions exceeding that of Pinatubo-1991 ( [[#Sigl--2015\|Sigl et al., 2015]] ).		Proxy records show that large volcanic eruptions with effective radiative forcing (ERF) more negative than –1 W m <sup>–2</sup> occurred on average twice a century throughout the last 2500 years, the most recent being Pinatubo in 1991 ( [[IPCC:Wg1:Chapter:Chapter-2#2.2.2\|Section 2.2.2]] ). About eight larger eruptions (ERF stronger than –5 W m <sup>–2</sup> ) also occurred during this period (Figure 2.2), notably Tambora about 1815 and Samalas about 1257. A Samalas-type eruption may occur one to two times per millennium on average ( [[#Newhall--2018\|Newhall et al., 2018]] ). Typically, three in every four centuries have experienced at least one eruption stronger than –1 W m <sup>–2</sup> (Pinatubo or larger). The volcanic aerosol burden was 14% lower during the 20th century compared to the average of the preceding 24 centuries ( [[IPCC:Wg1:Chapter:Chapter-2#2.2.2\|Section 2.2.2]] ), whereas the 13th century was among the most volcanically active, with four eruptions exceeding that of Pinatubo-1991 ( [[#Sigl--2015\|Sigl et al., 2015]] ).

	~~'''~~'''Past climate responses to volcanic activity'''~~'''~~		'''Past climate responses to volcanic activity'''

	Major eruptions drive a range of climate system responses for several years depending upon whether the eruption occurs in the tropics (stratospheric aerosol dispersion into both hemispheres) or the extratropics (dispersion into the hemisphere of eruption) owing to the Brewer-Dobson circulation. The climatic response also depends on the effective injection height, sulphur mass injected, and time of year of the eruption ( [[#Marshall--2019\|Marshall et al., 2019]] , 2020). These factors determine the total mass, lifetime and optical properties of volcanic aerosol in the stratosphere and influence the stratospheric aerosol optical depth (SAOD). The ERF from volcanic stratospheric aerosol is assessed to be –20 ± 5 W m <sup>–2</sup> per unit sAOD (Section 7.3.4.6).		Major eruptions drive a range of climate system responses for several years depending upon whether the eruption occurs in the tropics (stratospheric aerosol dispersion into both hemispheres) or the extratropics (dispersion into the hemisphere of eruption) owing to the Brewer-Dobson circulation. The climatic response also depends on the effective injection height, sulphur mass injected, and time of year of the eruption ( [[#Marshall--2019\|Marshall et al., 2019]] , 2020). These factors determine the total mass, lifetime and optical properties of volcanic aerosol in the stratosphere and influence the stratospheric aerosol optical depth (SAOD). The ERF from volcanic stratospheric aerosol is assessed to be –20 ± 5 W m <sup>–2</sup> per unit sAOD (Section 7.3.4.6).

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	Although incomplete, proxy records show large impacts upon contemporary society from eruptions such as 1257 Samalas and 1815 Tambora, the latter resulting in ‘the year without a summer’ with multiple harvest failures across the Northern Hemisphere (e.g., [[#Raible--2016\|Raible et al., 2016]] ). Comparing CMIP5 multi-model simulations with observations has improved understanding of the hydrological responses to 20th century eruptions, particularly global land monsoon drying, and associated uncertainties ( [[IPCC:Wg1:Chapter:Chapter-3#3.3.2.3\|Section 3.3.2.3]] ). Global mean land precipitation decreases for up to a few years following the eruption, with climatologically wet regions drying and dry regions wetting (Sections 3.3.2.3 and 4.4.4). Changes in monsoon circulations occur with a general weakening of tropical precipitation (Section 8.5.2.3) and a decrease in extreme precipitation over global monsoon regions (Section 11.4.4). Monsoon precipitation in one hemisphere tends to be enhanced by eruptions occurring in the other hemisphere or reduced if they occur in the same hemisphere (Sections 3.3.2.3 and 8.5.2.3). Volcanic eruptions have been linked to the onset of El Niño followed by La Niña although this connection remains contentious ( [[#Adams--2003\|Adams et al., 2003]] ; [[#Bradley--2003\|Bradley et al., 2003]] ; [[#McGregor--2010\|McGregor et al., 2010]] ; [[#Khodri--2017\|Khodri et al., 2017]] ; F. [[#Liu--2018\|]] [[#Liu--2018\|]] [[#Liu--2018\|]] [[#Liu--2018\|Liu et al., 2018]] ; [[#Sun--2019\|Sun et al., 2019]] ; [[#Paik--2020\|Paik et al., 2020]] ; [[#Predybaylo--2020\|Predybaylo et al., 2020]] ). Volcanic activity could drive short-term (one-to-three-year) positive changes in the annual SAM index through modulations in the extratropical temperature gradient and wave driving of the polar stratosphere ( [[#Yang--2018\|Yang and Xiao, 2018]] ). In the cryosphere, Arctic sea ice extent increases for years to decades ( [[#Gagné--2017a\|Gagné et al., 2017a]] ), and modelling indicates that sea ice/ocean feedbacks can prolong cooling long after volcanic aerosols are removed ( [[#Miller--2012\|Miller et al., 2012]] ). On annual time scales, the ocean buffers the atmospheric response to volcanic eruptions by storing the cooling in the ocean subsurface, then feeding it back to the atmosphere. Large eruptions affect ocean heat content and thermosteric sea level over decadal-to-centennial scales (Section 9.2.2.1).		Although incomplete, proxy records show large impacts upon contemporary society from eruptions such as 1257 Samalas and 1815 Tambora, the latter resulting in ‘the year without a summer’ with multiple harvest failures across the Northern Hemisphere (e.g., [[#Raible--2016\|Raible et al., 2016]] ). Comparing CMIP5 multi-model simulations with observations has improved understanding of the hydrological responses to 20th century eruptions, particularly global land monsoon drying, and associated uncertainties ( [[IPCC:Wg1:Chapter:Chapter-3#3.3.2.3\|Section 3.3.2.3]] ). Global mean land precipitation decreases for up to a few years following the eruption, with climatologically wet regions drying and dry regions wetting (Sections 3.3.2.3 and 4.4.4). Changes in monsoon circulations occur with a general weakening of tropical precipitation (Section 8.5.2.3) and a decrease in extreme precipitation over global monsoon regions (Section 11.4.4). Monsoon precipitation in one hemisphere tends to be enhanced by eruptions occurring in the other hemisphere or reduced if they occur in the same hemisphere (Sections 3.3.2.3 and 8.5.2.3). Volcanic eruptions have been linked to the onset of El Niño followed by La Niña although this connection remains contentious ( [[#Adams--2003\|Adams et al., 2003]] ; [[#Bradley--2003\|Bradley et al., 2003]] ; [[#McGregor--2010\|McGregor et al., 2010]] ; [[#Khodri--2017\|Khodri et al., 2017]] ; F. [[#Liu--2018\|]] [[#Liu--2018\|]] [[#Liu--2018\|]] [[#Liu--2018\|Liu et al., 2018]] ; [[#Sun--2019\|Sun et al., 2019]] ; [[#Paik--2020\|Paik et al., 2020]] ; [[#Predybaylo--2020\|Predybaylo et al., 2020]] ). Volcanic activity could drive short-term (one-to-three-year) positive changes in the annual SAM index through modulations in the extratropical temperature gradient and wave driving of the polar stratosphere ( [[#Yang--2018\|Yang and Xiao, 2018]] ). In the cryosphere, Arctic sea ice extent increases for years to decades ( [[#Gagné--2017a\|Gagné et al., 2017a]] ), and modelling indicates that sea ice/ocean feedbacks can prolong cooling long after volcanic aerosols are removed ( [[#Miller--2012\|Miller et al., 2012]] ). On annual time scales, the ocean buffers the atmospheric response to volcanic eruptions by storing the cooling in the ocean subsurface, then feeding it back to the atmosphere. Large eruptions affect ocean heat content and thermosteric sea level over decadal-to-centennial scales (Section 9.2.2.1).

	~~'''~~'''Potential implications on 21st century projections'''~~'''~~		'''Potential implications on 21st century projections'''

	Given the unpredictability of individual eruptions, volcanic forcing is prescribed as a constant background loading in CMIP6 models ( [[#Eyring--2016\|Eyring et al., 2016]] ). This means the effects of potential large volcanic eruptions are largely absent from model projections, and few studies have addressed the potential implications on 21st century warming. One study considered future scenarios with hypothetical volcanic eruptions consistent with levels of Common Era volcanic activity ( [[#Bethke--2017\|Bethke et al., 2017]] ) under RCP4.5 and found that climate projections could be substantially altered ( [[#cross-chapter-box-4.1\|Cross-Chapter Box 4.1]] , Figure 1). Although temporary, close to pre-industrial level temperatures could be experienced globally for a few years after a 1257 Samalas-sized eruption. Several other key climate indicators are also changed substantially, consistent with evidence from past events. [[#Bethke--2017\|Bethke et al. (2017)]] suggest that an eruption early in the 21st century could delay the timing of crossing 1.5°C global warming by several years. Clustered eruptions would have substantial impact upon GSAT evolution throughout the century ( [[#cross-chapter-box-4.1\|Cross-Chapter Box 4.1]] , Figure 1), and could have far-reaching implications, as observed for past eruptions. For near-term response options, decadal prediction models can update 21st-century projections once a volcanic eruption occurs ( [[#Timmreck--2016\|Timmreck et al., 2016]] ).		Given the unpredictability of individual eruptions, volcanic forcing is prescribed as a constant background loading in CMIP6 models ( [[#Eyring--2016\|Eyring et al., 2016]] ). This means the effects of potential large volcanic eruptions are largely absent from model projections, and few studies have addressed the potential implications on 21st century warming. One study considered future scenarios with hypothetical volcanic eruptions consistent with levels of Common Era volcanic activity ( [[#Bethke--2017\|Bethke et al., 2017]] ) under RCP4.5 and found that climate projections could be substantially altered ( [[#cross-chapter-box-4.1\|Cross-Chapter Box 4.1]] , Figure 1). Although temporary, close to pre-industrial level temperatures could be experienced globally for a few years after a 1257 Samalas-sized eruption. Several other key climate indicators are also changed substantially, consistent with evidence from past events. [[#Bethke--2017\|Bethke et al. (2017)]] suggest that an eruption early in the 21st century could delay the timing of crossing 1.5°C global warming by several years. Clustered eruptions would have substantial impact upon GSAT evolution throughout the century ( [[#cross-chapter-box-4.1\|Cross-Chapter Box 4.1]] , Figure 1), and could have far-reaching implications, as observed for past eruptions. For near-term response options, decadal prediction models can update 21st-century projections once a volcanic eruption occurs ( [[#Timmreck--2016\|Timmreck et al., 2016]] ).

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	'''Potential impact of volcanic eruption on future global temperature change.''' CMIP5 projections of possible 21st-century futures under RCP4.5 after a 1257 Samalas magnitude volcanic eruption in 2044, from [[#Bethke--2017\|Bethke et al. (2017)]] . '''(a)''' Volcanic ERF of the most volcanically active ensemble member, estimated from SAOD. '''(b)''' Annual mean global surface air temperature. Ensemble mean (solid) of future projections including volcanoes (blue) and excluding volcanoes (red) with 5–95% range (shading) and ensemble minima/maxima (dots); evolution of the most volcanically active member (black). Data created using a SMILE approach with NorESM1 in its CMIP5 configuration. See Sections 2.2.2 and 4.4.4 for more details. Further details on data sources and processing are available in the chapter data table (Table 4.SM.1).		'''Potential impact of volcanic eruption on future global temperature change.''' CMIP5 projections of possible 21st-century futures under RCP4.5 after a 1257 Samalas magnitude volcanic eruption in 2044, from [[#Bethke--2017\|Bethke et al. (2017)]] . '''(a)''' Volcanic ERF of the most volcanically active ensemble member, estimated from SAOD. '''(b)''' Annual mean global surface air temperature. Ensemble mean (solid) of future projections including volcanoes (blue) and excluding volcanoes (red) with 5–95% range (shading) and ensemble minima/maxima (dots); evolution of the most volcanically active member (black). Data created using a SMILE approach with NorESM1 in its CMIP5 configuration. See Sections 2.2.2 and 4.4.4 for more details. Further details on data sources and processing are available in the chapter data table (Table 4.SM.1).

	~~'''~~'''Summary'''~~'''~~		'''Summary'''

	It is ''likely'' that at least one large eruption will occur during the 21st century. Such an eruption would reduce GSAT for several years, decrease global mean land precipitation, alter monsoon circulation, modify extreme precipitation, and change the profile of many regional climatic impact-drivers. A low-likelihood, high-impact outcome would be several large eruptions that would greatly alter the 21st century climate trajectory compared to SSP-based ESM projections.		It is ''likely'' that at least one large eruption will occur during the 21st century. Such an eruption would reduce GSAT for several years, decrease global mean land precipitation, alter monsoon circulation, modify extreme precipitation, and change the profile of many regional climatic impact-drivers. A low-likelihood, high-impact outcome would be several large eruptions that would greatly alter the 21st century climate trajectory compared to SSP-based ESM projections.