Editing IPCC:AR6/WGI/Chapter-11 (section)

=== 11.4.5 Projections ===

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The AR5 concluded it is ''very likely'' that extreme precipitation events will be more frequent and more intense over most of the mid-latitude land masses and wet tropics in a warmer world ( [[#Collins--2013|Collins et al., 2013]] ). Post-AR5 studies provide more and ''robust evidence'' to support the previous assessments. These include an observed increase in extreme precipitation ( [[#11.4.3|Section 11.4.3]] ) and human causes of past changes ( [[#11.4.4|Section 11.4.4]] ), as well as projections based on either GCM and/or RCM simulations. The CMIP5 models project that the rate of increase in Rx1day with warming is independent of the forcing scenario ( [[IPCC:Wg1:Chapter:Chapter-8#8.5.3.1|Section 8.5.3.1]] ; [[#Pendergrass--2015|Pendergrass et al., 2015]] ) or forcing mechanism ( [[#Sillmann--2017a|Sillmann et al., 2017a]] ). This is confirmed in CMIP6 simulations ( [[#Sillmann--2019|Sillmann et al., 2019]] ; [[#Li--2021|Li et al., 2021]] ). In particular, for extreme precipitation that occurs once a year or less frequently, the magnitudes of the rates of change per 1°C change in global mean temperature are similar, regardless of whether the temperature change is caused by increases in carbon dioxide (CO <sub>2</sub> ), methane (CH <sub>4</sub> ), solar forcing, or sulphate (SO <sub>4</sub> ) ( [[#Sillmann--2019|Sillmann et al., 2019]] ). In some models – CESM1 in particular – the extreme precipitation response to warming may follow a quadratic relation ( [[#Pendergrass--2019|Pendergrass et al., 2019]] ). Figure 11.15 shows changes in the 10- and 50-year return values of Rx1day at different warming levels as simulated by the CMIP6 models. The median value of the scaling over land, across all Shared Socio-economic Pathway (SSP) scenarios and all models, is close to 7% per 1°C of warming for the 50-year return value of Rx1day. It is just slightly smaller for the 10- and 50-year return values of Rx5day ( [[#Li--2021|Li et al., 2021]] ). The 90% ranges of the multimodel ensemble changes across all land grid boxes in the 50-year return values for Rx1day and Rx5day do not overlap between 1.5°C and 2°C warming levels ( [[#Li--2021|Li et al., 2021]] ), indicating that a small increment such as 0.5°C in global warming can result in a significant increase in extreme precipitation. Projected long-period Rx1day return value changes are larger than changes in mean Rx1day and with larger relative changes for more rare events ( [[#Pendergrass--2018|Pendergrass, 2018]] ; [[#Mizuta--2020|Mizuta and Endo, 2020]] ; [[#Wehner--2020|Wehner, 2020]] ). The rate of change of moderate extreme precipitation may depend more on the forcing agent, similar to the mean precipitation response to warming ( [[#Lin--2016|Lin et al., 2016]] , 2018). Thus, there is ''high confidence'' that extreme precipitation that occurs once a year or less frequently increases proportionally to the amount of surface warming, and the rate of change in precipitation is not dependent on the underlying forcing agents of warming.

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[[File:16ec961ba91dca7123ead5a0783a5a3d IPCC_AR6_WGI_Figure_11_15.png]]

'''Figure 11.15 |''' '''Projected changes in the intensity of extreme precipitation events under 1°C, 1.5°C, 2°C, 3°C, and 4°C global warming levels relative to the 1850–1900 baseline.''' Extreme precipitation events are defined as the annual maximum daily maximum precipitation (Rx1day) that was exceeded on average once during a 10-year period (10-year event, blue) and once during a 50-year period (50-year event, orange) during the 1850–1900 base period. Results are shown for the global land. For each box plot, the horizontal line and the box represent the median and central 66% uncertainty range, respectively, of the intensity changes across the multi-model median, and the ‘whiskers’ extend to the 90% uncertainty range. The results are based on the multi-model ensemble estimated from simulations of global climate models contributing to the Coupled Model Intercomparison Project Phase 6 (CMIP6) under different Shared Socio-economic Pathway forcing scenarios. Based on [[#Li--2021|Li et al. (2021)]] . Further details on data sources and processing are available in the chapter data table (Table 11.SM.9).

The spatial patterns of the projected changes across different warming levels are quite similar, as shown in Figure 11.16, and confirmed by near-linear scaling between extreme precipitation and global warming levels at regional scales ( [[#Seneviratne--2020|Seneviratne and Hauser, 2020]] ). Internal variability modulates changes in heavy rainfall ( [[#Wood--2020|Wood and Ludwig, 2020]] ), resulting in different changes in different regions ( [[#Seneviratne--2020|Seneviratne and Hauser, 2020]] ). Extreme precipitation nearly always increases across land areas with larger increases at higher global warming levels, except in very few regions, such as Southern Europe around the Mediterranean Basin at low warming levels (Table 11.17). The ''very likely'' ranges of the multi-model ensemble changes across all land grid boxes in the 50-year return values for Rx1day and Rx5day between 1.5°C and 1°C warming levels are above zero for all continents except Europe, with the lower bound of the ''likely'' range above zero over Europe ( [[#Li--2021|Li et al., 2021]] ). Decreases in extreme precipitation are confined mostly to subtropical ocean areas and are highly correlated to decreases in mean precipitation due to storm track shifts. These subtropical decreases can extend to nearby land areas in individual realizations.

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[[File:94210254c8d018b47fc349341792c580 IPCC_AR6_WGI_Figure_11_16.png]]

'''Figure 11.16 |''' '''Projected changes in annual maximum daily precipitation at (a) 1.5°C, (b) 2°C, and (c) 4°C of global warming compared to the 1850–1900 baseline.''' Results are based on simulations from the Coupled Model Intercomparison Project Phase 6 (CMIP6) multi-model ensemble under the Shared Socio-economic Pathway (SSP), SSP1-1.9, SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5 scenarios. The numbers on the top right indicate the number of simulations included. Uncertainty is represented using the simple approach: no overlay indicates regions with high model agreement, where ≥80% of models agree on the sign of change; diagonal lines indicate regions with low model agreement, where &lt;80% of models agree on the sign of change. For more information on the simple approach, please refer to the Cross-Chapter Box ( [[IPCC:Wg1:Chapter:Atlas|Atlas]] 1. For details on the methods see Supplementary Material 11.SM.2. Changes in Rx1day are also displayed in the Interactive Atlas. Further details on data sources and processing are available in the chapter data table (Table 11.SM.9).

Projected increases in the probability of extreme precipitation of fixed magnitudes are nonlinear and show larger increases for more rare events (Figures 11.7 and 11.15; [[#Fischer--2015|Fischer and Knutti, 2015]] ; [[#Kharin--2018|Kharin et al., 2018]] ; [[#Li--2021|Li et al., 2021]] ).The CMIP5 model projected increases in the probability of high (99th and 99.9th) percentile precipitation between 1.5°C and 2°C warming scenarios are consistent with what can be expected based on observed changes ( [[#Fischer--2015|Fischer and Knutti, 2015]] ), providing confidence in the projections. The CMIP5 model simulations show that the frequency for present-day climate 20-year extreme precipitation is projected to increase by 10% at the 1.5°C global warming level, and by 22% at the 2.0°C global warming level, while the increase in the frequency for present-day climate 100-year extreme precipitation is projected to increase by 20% and more than 45% at the 1.5°C and 2.0°C warming levels, respectively ( [[#Kharin--2018|Kharin et al., 2018]] ). CMIP6 simulations with SSP scenarios show that the frequency of 10-year and 50-year events will be approximately doubled and tripled, respectively, at a very high warming level of 4°C (Figure 11.7; [[#Li--2021|Li et al., 2021]] ).

There is a limited number of studies on the projections of extreme hourly precipitation. The ability of GCMs to simulate hourly precipitation extremes is limited ( [[#Morrison--2019|Morrison et al., 2019]] ) and very few modelling centres archive sub-daily and hourly precipitation prior to CMIP6 experiments. RCM simulations project an increase in extreme sub-daily precipitation in North America ( [[#Li--2019b|]] [[#Li--2019|]] [[#Li--2019|]] [[#Li--2019|C. Li et al., 2019]] b ) and Sweden ( [[#Olsson--2013|Olsson and Foster, 2013]] ), but these models still do not explicitly resolve convective processes that are important for properly simulating extreme sub-daily precipitation. Simulations by RCMs that explicitly resolve convective processes (convection-permitting models) are limited in length and only available in a few regions because of high computing costs. Yet, a majority of the available convection-permitting simulations project increases in the intensities of extreme sub-daily precipitation events, with the amount similar to or higher than the C-C scaling rate ( [[#Kendon--2014|Kendon et al., 2014]] , 2019; [[#Ban--2015|Ban et al., 2015]] ; [[#Prein--2016b|Prein et al., 2016b]] ; [[#Helsen--2020|Helsen et al., 2020]] ; [[#Fowler--2021|Fowler et al., 2021]] ). An increase is projected in extreme sub-daily precipitation over Africa ( [[#Kendon--2019|Kendon et al., 2019]] ); East Africa ( [[#Finney--2020|Finney et al., 2020]] ) and Western Africa ( [[#Berthou--2019a|Berthou et al., 2019a]] ; [[#Fitzpatrick--2020|Fitzpatrick et al., 2020]] ), even for areas where parametrized RCMs project a decrease; in Europe (Hodnebrog et al., 2019; [[#Chan--2020|Chan et al., 2020]] ); as well as in the continental USA ( [[#Prein--2016b|Prein et al., 2016b]] ). Overall, while limited, the available evidence points to an increase in extreme sub-daily precipitation in the future. Studies on future changes in extreme precipitation for a month or longer are limited. One study projects an increase in extreme monthly precipitation in Japan under 4°C global warming for around 80% of stations in the summer ( [[#Hatsuzuka--2019|Hatsuzuka and Sato, 2019]] ).

In Africa (Table 11.5), extreme precipitation will ''likely'' increase under warming levels of 2°C or below (compared to pre-industrial values) and ''very likely'' increase at higher warming levels. Simulations by CMIP5, CMIP6 and CORDEX regional models project an increase in daily extreme precipitation between 1.5°C and 2.0°C warming levels. The pattern of change in heavy precipitation under different scenarios or warming levels is similar with larger increases for higher warming levels (e.g., [[#Nikulin--2018|Nikulin et al., 2018]] ; [[#Li--2021|Li et al., 2021]] ). With increases in warming, extreme precipitation is projected to increase in the majority of land regions in Africa ( [[#Mtongori--2016|Mtongori et al., 2016]] ; [[#Pfahl--2017|Pfahl et al., 2017]] ; [[#Diedhiou--2018|Diedhiou et al., 2018]] ; [[#Dunning--2018|Dunning et al., 2018]] ; [[#Akinyemi--2019|Akinyemi and Abiodun, 2019]] ; [[#Giorgi--2019|Giorgi et al., 2019]] ). Over Southern Africa, heavy precipitation will ''likely'' increase by the end of the 21st century under RCP 8.5 ( [[#Dosio--2016|Dosio, 2016]] ; [[#Pinto--2016|Pinto et al., 2016]] ; [[#Abiodun--2017|Abiodun et al., 2017]] ; [[#Dosio--2019|Dosio et al., 2019]] ). However, heavy rainfall amounts are projected to decrease over western South Africa ( [[#Pinto--2018|Pinto et al., 2018]] ) as a result of a projected decrease in the frequency of the prevailing westerly winds south of the continent that translates into fewer cold fronts and closed mid-latitudes cyclones ( [[#Engelbrecht--2009|Engelbrecht et al., 2009]] ; [[#Pinto--2018|Pinto et al., 2018]] ). Heavy precipitation will ''likely'' increase by the end of the century under RCP8.5 in West Africa ( [[#Diallo--2016|Diallo et al., 2016]] ; [[#Dosio--2016|Dosio, 2016]] ; [[#Sylla--2016|Sylla et al., 2016]] ; [[#Abiodun--2017|Abiodun et al., 2017]] ; [[#Akinsanola--2019|Akinsanola and Zhou, 2019]] ; [[#Dosio--2019|Dosio et al., 2019]] ) and is projected to increase ( ''high confidence'' ) in Central Africa ( [[#Fotso-Nguemo--2018|Fotso-Nguemo et al., 2018]] , 2019; [[#Sonkoué--2019|Sonkoué et al., 2019]] ) and eastern Africa ( [[#Thiery--2016|Thiery et al., 2016]] ; [[#Ongoma--2018a|Ongoma et al., 2018a]] ). In north-east and central east Africa, extreme precipitation intensity is projected to increase across CMIP5, CMIP6 and CORDEX-CORE ( ''high confidence'' ) in most areas annually ( [[#Coppola--2021a|Coppola et al., 2021a]] ), but the trends differ from season to season in all future scenarios ( [[#Dosio--2019|Dosio et al., 2019]] ). In northern Africa, there is ''low confidence'' in the projected changes in heavy precipitation, either due to a lack of agreement among studies on the sign of changes ( [[#Sillmann--2013a|Sillmann et al., 2013a]] ; [[#Giorgi--2014|Giorgi et al., 2014]] ) or due to insufficient evidence.

In Asia (Table 11.8), extreme precipitation will ''likely'' increase at global warming levels of 2°C and below, but ''very likely'' increase at higher warming levels for the region as whole. The CMIP6 multi-model median projects an increase in the 10- and 50-year return values of Rx1day and Rx5day over more than 95% of regions, even at the 2°C warming level, with larger increases at higher warming levels, independent of emissions scenarios ( [[#Li--2021|Li et al., 2021]] , also Figure 11.7). The CMIP5 models produced similar projections. Both heavy rainfall and rainfall intensity are projected to increase ( [[#Zhou--2014|Zhou et al., 2014]] ; [[#Guo--2016|Guo et al., 2016]] , 2018; Y. [[#Xu--2016|]] [[#Xu--2016|Xu et al., 2016]] ; [[#Endo--2017|Endo et al., 2017]] ; [[#Han--2018|Han et al., 2018]] ; G. [[#Kim--2018|]] [[#Kim--2018|]] [[#Kim--2018|Kim et al., 2018]] ). A half-degree difference in warming between the 1.5°C and 2.0°C warming levels can result in a detectable increase in extreme precipitation over the region ( [[#Li--2021|Li et al., 2021]] ), in the Asian–Australian monsoon region ( [[#Chevuturi--2018|Chevuturi et al., 2018]] ), and over South Asia and China (D. [[#Lee--2018|]] [[#Lee--2018|]] [[#Lee--2018|Lee et al., 2018]] ; W. [[#Li--2018|]] [[#Li--2018|]] [[#Li--2018|]] [[#Li--2018|Li et al., 2018]] b). While there are regional differences, extreme precipitation is projected to increase in almost all sub-regions, though there can be spatial heterogeneity within sub-regions, such as in India ( [[#Shashikanth--2018|Shashikanth et al., 2018]] ) and South East Asia ( [[#Ohba--2019|Ohba and Sugimoto, 2019]] ). In East and South East Asia, there is ''high confidence'' that extreme precipitation is projected to intensify (Seo et al., 2014; [[#Zhou--2014|Zhou et al., 2014]] ; Y. [[#Xu--2016|]] [[#Xu--2016|Xu et al., 2016]] ; [[#Nayak--2017|Nayak et al., 2017]] ; X. [[#Wang--2017|]] [[#Wang--2017|Wang et al., 2017]] ; Y. [[#Wang--2017|]] [[#Wang--2017|Wang et al., 2017]] ; [[#Guo--2018|Guo et al., 2018]] ; D. [[#Li--2018|]] [[#Li--2018|]] [[#Li--2018|]] [[#Li--2018|Li et al., 2018]] ; [[#Sui--2018|Sui et al., 2018]] ). Extreme daily precipitation is also projected to increase in South Asia (Xu et al., 2017; [[#Han--2018|Han et al., 2018]] ; [[#Shashikanth--2018|Shashikanth et al., 2018]] ). The extreme precipitation indices, including Rx5day, R95p, and days of heavy precipitation (i.e., R10mm), are all projected to increase under the RCP4.5 and RCP8.5 scenarios in central and northern Asia ( [[#Xu--2017|Xu et al., 2017]] ; [[#Han--2018|Han et al., 2018]] ). A general wetting across the whole Tibetan Plateau and the Himalayas is projected, with increases in heavy precipitation in the 21st century (Palazzi et al., 2013; [[#Zhou--2014|Zhou et al., 2014]] ; [[#Rajbhandari--2015|Rajbhandari et al., 2015]] ; R. [[#Zhang--2015|Zhang et al., 2015]] ; [[#Wu--2017|Wu et al., 2017]] ; [[#Gao--2018|Gao et al., 2018]] ; [[#Paltan--2018|Paltan et al., 2018]] ). Agreement in projected changes by different models is low in regions of complex topography such as Hindu-Kush Himalayas ( [[#Roy--2019|Roy et al., 2019]] ), but CMIP5, CMIP6 and CORDEX-CORE simulations consistently project an increase in heavy precipitation in higher latitude areas, such as West and East Siberia, and Russian Far East ( ''high confidence'' ) ( [[#Coppola--2021a|Coppola et al., 2021a]] ).

In Australasia (Table 11.11), most CMIP5 models project an increase in Rx1day under RCP4.5 and RCP8.5 scenarios for the late 21st century (CSIRO and BOM, 2015; [[#Alexander--2017|Alexander and Arblaster, 2017]] ; [[#Grose--2020|Grose et al., 2020]] ) and the CMIP6 multi-model median projects an increase in the 10- and 50-year return values of Rx1day and Rx5day at a rate between 5% and 6% per 1°C of near-surface global mean warming (Figure 11.7; [[#Li--2021|Li et al., 2021]] ). Yet, there is large uncertainty in the increase because projected changes in dynamic processes lead to a decrease in Rx1day that can offset the thermodynamic increase over a large portion of the region (Box 11.1, Figure 1; [[#Pfahl--2017|Pfahl et al., 2017]] ). Projected changes in moderate extreme precipitation (the 99th percentile of daily precipitation) by RCMs under RCP8.5 for 2070–2099 are mixed, with more regions showing decreases than increases ( [[#Evans--2021|Evans et al., 2021]] ). It is ''likely'' that daily rainfall extremes such as Rx1day will increase at the continental scale for global warming levels at or above 3°C. Daily rainfall extremes are projected to increase at the 2.0°C global warming level ( ''medium confidence'' ), and there is ''low confidence'' in changes at the 1.5°C ''.'' Projected changes show important regional differences with ''very likely'' increases over Northern Australia ( [[#Alexander--2017|Alexander and Arblaster, 2017]] ; [[#Herold--2018|Herold et al., 2018]] ; [[#Grose--2020|Grose et al., 2020]] ) and New Zealand ( [[#MfE--2018|MfE, 2018]] ) where projected dynamic contributions are small (Box 11.1 Figure 1; [[#Pfahl--2017|Pfahl et al., 2017]] ) and ''medium confidence'' on increases over central, eastern, and Southern Australia where dynamic contributions are substantial and can affect local phenomena (CSIRO and BOM, 2015; [[#Pepler--2016|Pepler et al., 2016]] ; [[#Bell--2019|Bell et al., 2019]] ; [[#Dowdy--2019|Dowdy et al., 2019]] ).

In Central and South America (Table 11.14), extreme precipitation will ''likely'' increase at global warming levels of 2°C and below, but ''very likely'' increase at higher warming levels for the region as whole. A larger increase in global surface temperature leads to a larger increase in extreme precipitation, independent of emissions scenarios ( [[#Li--2021|Li et al., 2021]] ). But there are regional differences in the projection, and projected changes for more moderate extreme precipitation are also more uncertain. Extreme precipitation, represented by the number of days with daily precipitation exceeding 50 mm and the annual fraction of precipitation falling during days with the top 10% daily precipitation amount, is projected to increase on the eastern coast of Southern Central America, but to decrease along the Pacific coasts of El Salvador and Guatemala ( [[#Imbach--2018|Imbach et al., 2018]] ). Chouet al. (2014b) and [[#Giorgi--2014|Giorgi et al. (2014)]] projected an increase in extreme precipitation over South-Eastern South America and the Amazon. Projected changes in moderate extreme precipitation represented by the 99th percentile of daily precipitation by different models under different emissions scenarios, even at high warming levels, are mixed: increases are projected for all regions by the CORDEX-CORE and CMIP5 simulations, while increases for some regions and decreases for other regions are projected by CMIP6 simulations ( [[#Coppola--2021a|Coppola et al., 2021a]] ). Extreme precipitation is projected to increase in the La Plata basin ( [[#Cavalcanti--2015|Cavalcanti et al., 2015]] ; [[#Carril--2016|Carril et al., 2016]] ). [[#Taylor--2018|Taylor et al. (2018)]] projected a decrease in days with intense rainfall in the Caribbean under 2°C global warming by the 2050s under RCP4.5 relative to 1971–2000.

In Europe (Table 11.17), extreme precipitation will ''likely'' increase at global warming levels of 2°C and below, but ''very likely'' increase for higher warming levels for the region as whole. The CMIP6 multi-model median projects an increase in the 10- and 50-year return values of Rx1day and Rx5day over a majority of the region at the 2°C global warming level, with more than 95% of the region showing an increase at higher warming levels (Figure 11.7; [[#Li--2021|C. Li et al., 2021]] ). The most intense precipitation events observed today in Europe are projected to almost double in occurrence for each 1°C of further global warming ( [[#Myhre--2019|Myhre et al., 2019]] ). Extreme precipitation is projected to increase in both boreal winter and summer over Europe ( [[#Madsen--2014|Madsen et al., 2014]] ; [[#Christensen--2015|Christensen et al., 2015]] ; [[#Nissen--2017|Nissen and Ulbrich, 2017]] ). There are regional differences, with decreases or no change for the southern part of Europe, such as the southern Mediterranean (Tramblay and Somot, 2018; [[#Lionello--2020|Lionello and Scarascia, 2020]] ; [[#Coppola--2021a|Coppola et al., 2021a]] ), uncertain changes over central Europe ( [[#Argüeso--2012|Argüeso et al., 2012]] ; [[#Croitoru--2013|Croitoru et al., 2013]] ; [[#Rajczak--2013|Rajczak et al., 2013]] ; [[#Casanueva--2014|Casanueva et al., 2014]] ; [[#Patarčić--2014|Patarčić et al., 2014]] ; [[#Paxian--2014|Paxian et al., 2014]] ; [[#Roth--2014|Roth et al., 2014]] ; [[#Fischer--2015|Fischer and Knutti, 2015]] ; [[#Monjo--2016|Monjo et al., 2016]] ) and a strong increase in the remaining parts, including the Alps region ( [[#Gobiet--2014|Gobiet et al., 2014]] ; [[#Donnelly--2017|Donnelly et al., 2017]] ), particularly in winter ( [[#Fischer--2015|Fischer et al., 2015]] ), and in northern Europe. In a 3°C warmer world, there will be a robust increase in extreme rainfall over 80% of land areas in northern Europe ( [[#Madsen--2014|Madsen et al., 2014]] ; [[#Donnelly--2017|Donnelly et al., 2017]] ; [[#Cardell--2020|Cardell et al., 2020]] ).

In North America (Table 11.20), the intensity and frequency of extreme precipitation will ''likely'' increase at the global warming levels of 2°C and below, and ''very likely'' increase at higher warming levels. An increase is projected by CMIP6 model simulations ( [[#Li--2021|Li et al., 2021]] ) and by previous model generations (Wu,2015; Easterling et al., 2017; [[#Innocenti--2019|Innocenti et al., 2019]] ), as well as by RCMs (Coppola et al., 2021a). Projections of extreme precipitation over the southern portion of the continent and over Mexico are more uncertain, with decreases possible ( [[#Sillmann--2013b|Sillmann et al., 2013b]] ; [[#Alexandru--2018|Alexandru, 2018]] ; [[#Coppola--2021a|Coppola et al., 2021a]] ).

In summary, heavy precipitation will generally become more frequent and more intense with additional global warming. At global warming levels of 4°C relative to the pre-industrial, very rare (e.g., one in 10 or more years) heavy precipitation events would become more frequent and more intense than in the recent past, on the global scale ( ''virtually certain'' ), and in all continents and AR6 regions: The increase in frequency and intensity is ''extremely likely'' for most continents and ''very likely'' for most AR6 regions. The likelihood is lower at lower global warming levels and for less-rare heavy precipitation events. At the global scale, the intensification of heavy precipitation will follow the rate of increase in the maximum amount of moisture that the atmosphere can hold as it warms ( ''high confidence'' ), of about 7% per 1°C of global warming. The increase in the frequency of heavy precipitation events will be non-linear with more warming and will be higher for rarer events ( ''high confidence'' ), with 10- and 50-year events to be approximately double and triple, respectively, at the 4°C warming level. Increases in the intensity of extreme precipitation events at regional scales will depend on the amount of regional warming as well as changes in atmospheric circulation and storm dynamics leading to regional differences in the rate of heavy precipitation changes ( ''hi'' ''gh confidence'' ).

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