Editing IPCC:AR6/WGIII/Chapter-6 (section)

=== 6.5.2 Impacts on Energy Supply ===

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The increased weather dependency of future low-carbon electricity systems amplifies the possible impacts of climate change ( [[#Staffell--2018|Staffell and Pfenninger 2018]] ). However, ''globally'' climate change impacts on electricity generation – including hydro, wind and solar power potentials – should not compromise climate mitigation strategies ( ''high confidence'' ). Many of the changes in the climate system will be geographically complex at the regional and local levels. Thus, ''regionally'' climate change impacts on electricity generation could be significant. Climate change impacts on bioenergy potentials are more uncertain because of uncertainties associated with the crop response to climate change, future water availability and crop deployment. Climate change can reduce the efficiency of thermal power generation and increase the risk of power plant shutdowns during droughts. The potential additional cooling water needs of CCS can increase these risks.

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==== 6.5.2.1 dropower ====

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The impacts of climate change on hydropower will vary by region. High latitudes in the northern hemisphere are anticipated to experience increased runoff and hydropower potential. For other regions, studies find both increasing and decreasing runoff and hydropower potential. Areas with decreased runoff are anticipated to experience reduced hydropower production and increased water conflict among different economic activities ( ''high confidence'' ).

Hydropower production is directly related to the availability of water. Changes in runoff and its seasonality and changes in temperature and precipitation intensity will influence hydroelectricity production ( [[#IHA--2019|IHA 2019]] ). In general, increased precipitation will increase water availability and hydropower production. Increased precipitation intensity, however, may impact on the integrity of dam structures and affect power production by increasing debris accumulation and vegetation growth. Additionally, increased precipitation intensity results in the silting of the reservoirs or increases the amount of water spilt, resulting in erosion ( [[#Schaeffer--2012|Schaeffer et al. 2012]] ; [[#IHA--2019|IHA 2019]] ). Climate change will likely lead to higher air temperatures, resulting in more surface evaporation, less water storage, and loss of equipment efficiency ( [[#Ebinger--2011|Ebinger and Vergara 2011]] ; [[#Mukheibir--2013|Mukheibir 2013]] ; [[#Fluixá-Sanmartín--2018|Fluixá-Sanmartín et al. 2018]] ; [[#Hock--2019|Hock et al. 2019]] ). Climate change may alter the demands for water use by other sectors that often rely on stored water in multi-purpose reservoirs, and may therefore generate conflicts over water use. The increased need for water for irrigation and/or industry can affect the availability of water for hydropower generation ( [[#Spalding-Fecher--2016|Spalding-Fecher et al. 2016]] ; [[#Solaun--2017|Solaun and Cerdá 2017]] ). Higher temperatures increase glacier melt, increasing water availability for hydropower while the glaciers exist. Changes in the timing of snow and ice melt may require upgrading in storage capacity and adaptation of the hydropower plant management for fully exploiting the increase in water availability.

The conclusions regarding climate change impacts on hydropower vary due to differences in modelling assumptions and methodology, such as choice of the climate and hydrological models, choice of metrics (e.g., projected production vs hydropower potential), level of modelling details between local and global studies, reservoir operation assumptions. Also important is how hydropower production matches up with other reservoir purposes, accounting for other water and energy users, and how the competing uses are impacted by climate change ( [[#van%20Vliet--2016b|van Vliet et al. 2016b]] ; [[#Turner--2017|Turner et al. 2017]] ). Nonetheless, analyses consistently demonstrate that the global impact of climate change on hydropower will be small, but the regional impacts will be larger, and will be both positive and negative (Figure 6.20). Gross global hydropower potential in the 2050s has been estimated to slightlydecrease ( [[#Hamududu--2012|Hamududu and Killingtveit 2012]] ) between 0.4% (for the low-emission scenario) and 6.1% (for the highest-emission scenario) for the 2080s compared to 1971–2000 ( [[#van%20Vliet--2016a|van Vliet et al. 2016a]] ).

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[[File:d638a221224162ded9f7674d2feb6ef8 IPCC_AR6_WGIII_Figure_6_20.png]]

'''Figure 6.20 | Global spatial patterns of changes in gross hydropower potential based on climate forcing from five climate models.''' Changes are shown for the 2050s (upper) and the 2080s (lower) for the low-emission scenario (RCP2.6; left) and highest emission scenario (RCP8.5; right) scenarios relative to the control period (1971–2000). Source: data from [[#van%20Vliet--2016b|van Vliet et al. (2016b)]] .

Regional changes in hydropower are estimated from 5–20% increases for most areas in high latitudes ( [[#van%20Vliet--2016b|van Vliet et al. 2016b]] ; [[#Turner--2017|Turner et al. 2017]] ) to decreases of 5–20% in areas with increased drought conditions ( [[#Cronin--2018|Cronin et al. 2018]] ). Models show a consistent increase in streamflow and hydropower production by 2080 in high latitudes of the northern hemisphere and parts of the tropics (Figure 6.20) (e.g., central Africa and southern Asia) while decreasing in the USA, southern and central Europe, Southeast Asia and southern South America, Africa and Australia ( [[#van%20Vliet--2016c|van Vliet et al. 2016c]] ,a). Decreases in hydropower production are indicated for parts of North America, central and southern Europe, the Middle East, central Asia and Southern South America. Studies disagree on the changes in hydropower production in China, central South America, and partially in southern Africa ( [[#Hamududu--2012|Hamududu and Killingtveit 2012]] ; [[#van%20Vliet--2016b|van Vliet et al. 2016b]] ; [[#Solaun--2019|Solaun and Cerdá 2019]] ; [[#Fan--2020|Fan et al. 2020]] ).

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==== 6.5.2.2 Wind Energy ====

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Climate change will not substantially impact future wind resources and will not compromise the ability of wind energy to support low-carbon transitions ( ''high confidence'' ). Changing wind variability may have a small-to-modest impact on backup energy and storage needs ( ''low confidence'' ); however, current evidence is largely from studies focused on Europe.

Long-term global wind energy resources are not expected to substantially change in future climate scenarios ( [[#Karnauskas--2018|Karnauskas et al. 2018]] ; [[#Pryor--2020|Pryor et al. 2020]] ; [[#Yalew--2020|Yalew et al. 2020]] ). However, recent research has indicated consistent shifts in the geographic position of atmospheric jets in the high-emission scenarios ( [[#Harvey--2014|Harvey et al. 2014]] ), which would decrease wind power potentials across the Northern Hemisphere mid-latitudes and increase wind potentials across the tropics and the Southern Hemisphere. However, the climate models used to make these assessments differ in how well they can reproduce the historical wind resources and wind extremes, which raises questions about the robustness of their predictions of future wind resources ( [[#Pryor--2020|Pryor et al. 2020]] ).

There are many regional studies on changes in wind resources from climate change. For Europe, there is medium evidence and moderate agreement that wind resources are already increasing and will continue to increase in Northern Europe and decrease in Southern Europe ( [[#Carvalho--2017|Carvalho et al. 2017]] ; [[#Devis--2018|Devis et al. 2018]] ; [[#Moemken--2018|Moemken et al. 2018]] ). For North America, the various studies have low agreement for the changes in future wind resources in part because the year-to-year variations in wind resources are often larger than the future change due to climate change ( [[#Johnson--2016|Johnson and Erhardt 2016]] ; [[#Chen--2020|Chen 2020]] ; [[#Costoya--2020|Costoya et al. 2020]] ; [[#Wang--2020b|Wang et al. 2020b]] ). Studies show increases in future wind resources in windy areas in South America ( [[#Ruffato-Ferreira--2017|Ruffato-Ferreira et al. 2017]] ; [[#de%20Jong--2019|de Jong et al. 2019]] ). No robust future changes in wind resources have been identified in China ( [[#Xiong--2019|Xiong et al. 2019]] ). However, none of the global or regional studies of the effects of climate change on wind resources considers the fine-scale dependence of wind resources on the topography and wind direction ( [[#Sanz%20Rodrigo--2016|Sanz Rodrigo et al. 2016]] ; [[#Dörenkämper--2020|Dörenkämper et al. 2020]] ) or the effect of expanding wind energy exploitation ( [[#Volker--2017|Volker et al. 2017]] ; [[#Lundquist--2019|Lundquist et al. 2019]] ). There is limited evidence that extreme wind speeds, which can damage wind turbines, will increase due to climate change ( [[#Pes--2017|Pes et al. 2017]] ; [[#Pryor--2020|Pryor et al. 2020]] ). Nevertheless, projected changes in Europe and North America – regions where the most extensive analysis has been undertaken – are expected to be within the estimates embedded in the design standards of wind turbines ( [[#Pryor--2013|Pryor and Barthelmie 2013]] ).

Future wind generation in Europe could decrease in summer and autumn, increasing in winter in northern-central Europe but decreasing in southernmost Europe ( [[#Carvalho--2017|Carvalho et al. 2017]] ). Towards 2100, intra-annual variations increase in most of Europe, except around the Mediterranean area ( [[#Reyers--2016|Reyers et al. 2016]] ), but this may reflect natural multi-decadal variability ( [[#Wohland--2019b|Wohland et al. 2019b]] ). Wind speeds may become more homogeneous over large geographical regions in Europe due to climate change, increasing the likelihood of large areas experiencing high or low wind speeds simultaneously ( [[#Wohland--2017|Wohland et al. 2017]] ). These changes could result in fewer benefits in the transmission of wind generation between countries and increased system integration costs. Europe could require a modest increase (up to 7%) in backup energy towards the end of the 21st century due to more homogeneous wind conditions over Europe ( [[#Wohland--2017|Wohland et al. 2017]] ; [[#Weber--2018|Weber et al. 2018]] ). However, other studies report that the impact of climate change is substantially smaller than interannual variability, with no significant impact on the occurrence of extreme low wind production events in Europe (Van Der Wiel et al. 2019). If European electricity systems are designed to manage the effects of existing weather variability on wind power, they can likely also cope with climate change impacts on wind power ( [[#Ravestein--2018|Ravestein et al. 2018]] ). Changes in wind-generation variability caused by climate change are also reported for North America ( [[#Haupt--2016|Haupt et al. 2016]] ; [[#Losada%20Carreño--2018|Losada Carreño et al. 2018]] ), with modest impacts on electricity system operation ( [[#Craig--2019|Craig et al. 2019]] ).

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==== 6.5.2.3 Solar Energy ====

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Climate change is not expected to substantially impact global solar insolation and will not compromise the ability of solar energy to support low-carbon transitions ( ''high confidence'' ). Models show dimming and brightening in certain regions, driven by cloud, aerosol and water vapour trends ( [[IPCC:Wg3:Chapter:Chapter-12|Chapter 12]] of IPCC AR6 WGI). The increase in surface temperature, which affects all regions, decreases solar power output by reducing the PV panel efficiency. In some models and climate scenarios, the increases in solar insolation are counterbalanced by reducing efficiency due to rising surface air temperatures, which increase significantly in all models and scenarios ( [[#Jerez--2015|Jerez et al. 2015]] ; [[#Bartók--2017|Bartók et al. 2017]] ; [[#Emodi--2019|Emodi et al. 2019]] ). Increases in aerosols would reduce the solar resource available and add to maintenance costs ( [[IPCC:Wg3:Chapter:Chapter-12|Chapter 12]] of IPCC AR6 WGI).

In many emission scenarios, the effect on solar PV from temperature-induced efficiency losses is smaller than the effect expected from changes on solar insolation due to variations in water vapour and clouds in most regions. Also, future PV technologies will likely have higher efficiency, which would offset temperature-related declines ( [[#Müller--2019|Müller et al. 2019]] ). Cloud cover is projected to decrease in the subtropics (around –0.05% per year), including parts of North America, vast parts of Europe and China, South America, South Africa and Australia ( ''medium agreement'' , ''medium evidence'' ). Thus, models project modest (&lt;3%) increases in solar PV by the end of the century for southern Europe, northern and southern Africa, Central America, and the Caribbean ( [[#Emodi--2019|Emodi et al. 2019]] ). There are several studies projecting decreasing solar production, but these are generally influenced by other factors, for example, increasing air pollution ( [[#Ruosteenoja--2019|Ruosteenoja et al. 2019]] ). The multi-model means for solar insolation in regional models decrease 0.60 W m –2 per decade from 2006 to 2100 over most of Europe ( [[#Bartók--2017|Bartók et al. 2017]] ), with the most significant decreases in the Northern countries ( [[#Jerez--2015|Jerez et al. 2015]] ).

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==== 6.5.2.4 Bioenergy ====

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Climate change can affect biomass resource potential directly, via changes in the suitable range (i.e., the area where bioenergy crops can grow) and/or changes in yield, and indirectly, through changes in land availability. Increases in CO 2 concentration increase biomass yield; climate changes (e.g., temperature, precipitation, and so on) can either increase or decrease the yield and suitable range.

Climate change will shift the suitable range for bioenergy towards higher latitudes, but the net change in the total suitable area is uncertain ( ''high confidence'' ). Several studies show northward shifts in the suitable range for bioenergy in the northern hemisphere ( [[#Tuck--2006|Tuck et al. 2006]] ; [[#Barney--2010|Barney and DiTomaso 2010]] ; [[#Bellarby--2010|Bellarby et al. 2010]] ; [[#Hager--2014|Hager et al. 2014]] ; [[#Wang--2014a|Wang et al. 2014a]] ; [[#Preston--2016|Preston et al. 2016]] ; [[#Conant--2018|Conant et al. 2018]] ; [[#Cronin--2018|Cronin et al. 2018]] ), but the net effect of climate change on total suitable area varies by region, species, and climate model ( [[#Barney--2010|Barney and DiTomaso 2010]] ; [[#Hager--2014|Hager et al. 2014]] ; [[#Wang--2014a|Wang et al. 2014a]] ).

The effect of climate change on bioenergy crop yields will vary across region and feedstock ( ''high confidence'' ); however, in general, yields will decline in low latitudes ( ''medium confidence'' ) and increase in high latitudes ( ''low confidence'' ) ( [[#Haberl--2010|Haberl et al. 2010]] ; [[#Cosentino--2012|Cosentino et al. 2012]] ; [[#Preston--2016|Preston et al. 2016]] ; [[#Cronin--2018|Cronin et al. 2018]] ; [[#Mbow--2019|Mbow et al. 2019]] ). However, the average change in yield varies significantly across studies, depending on the feedstock, region, and other factors (Beringer et al. 2011; [[#Kyle--2014|Kyle et al. 2014]] ; [[#Mbow--2019|Mbow et al. 2019]] ; [[#Dolan--2020|Dolan et al. 2020]] ). Only a few studies extend the modelling of climate change impacts on bioenergy to quantify the effect on bioenergy deployment or its implications on the energy system ( [[#Calvin--2013|Calvin et al. 2013]] , 2019; [[#Kyle--2014|Kyle et al. 2014]] ; [[#Thornton--2017|Thornton et al. 2017]] ). These studies find that changes in deployment are of the same sign as changes in yield; that is, if yields increase, then deployment increases.

Some of the uncertainty in the sign and magnitude of the impacts of climate change on bioenergy potential is due to uncertainties in CO 2 fertilisation (the increase in photosynthesis due to increases in atmospheric CO 2 concentration) ( [[#Haberl--2011|Haberl et al. 2011]] ; [[#Bonjean%20Stanton--2016|Bonjean Stanton et al. 2016]] ; [[#Cronin--2018|Cronin et al. 2018]] ; [[#Solaun--2019|Solaun and Cerdá 2019]] ; [[#Yalew--2020|Yalew et al. 2020]] ). For example, earlier studies found that, without CO 2 fertilisation, climate change will reduce global bioenergy potential by about 16%; with CO 2 fertilisation, however, climate change increases this potential by 45% ( [[#Haberl--2011|Haberl et al. 2011]] ). However, newer studies in the USA find little effect of CO 2 fertilisation on switchgrass yield ( [[#Dolan--2020|Dolan et al. 2020]] ). There is also a considerable uncertainty across climate and crop models in estimating bioenergy potential ( [[#Hager--2014|Hager et al. 2014]] ).

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==== 6.5.2.5 Thermal Power Plants ====

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The operation of thermal power plants will be affected by climate change, deriving from changes in the ambient conditions like temperature, humidity and water availability ( [[#Schaeffer--2012|Schaeffer et al. 2012]] ) ( ''high confidence'' ). Changes in ambient temperature have relatively small impacts on coal-fired and nuclear power plants (Rankine cycle); however, gas-fired power plants (Brayton or combined-cycle) may have their thermal efficiency and power output significantly decreased ( [[#De%20Sa--2011|De Sa and Al Zubaidy 2011]] ; [[#Schaeffer--2012|Schaeffer et al. 2012]] ). Droughts decrease potential cooling water for thermal power plants and increase the probability of water outlet temperatures exceeding regulatory limits, leading to lower production or shutdowns. Thermal power utilisation has been reported to be, on average, 3.8% lower during drought years globally ( [[#van%20Vliet--2016c|van Vliet et al. 2016c]] ), and further significant decreases in available thermal power plant capacity due to climate change are projected ( [[#Koch--2014|Koch et al. 2014]] ; [[#van%20Vliet--2016b|van Vliet et al. 2016b]] ; [[#Yalew--2020|Yalew et al. 2020]] ). An increase in climate-related nuclear power disruptions has been reported in the past decades globally ( [[#Ahmad--2021|Ahmad 2021]] ).

Carbon capture may increase cooling water usage significantly, especially in retrofits, with up to 50% increase in water usage for coal-fired power plants globally, depending on the CCS technology (Rosa et al. 2020) ( [[#6.4|Section 6.4]] ). In Asia, planned coal capacity is expected to be vulnerable to droughts, sea level rise, and rising air temperatures, and this may be exacerbated by incorporating carbon capture ( [[#Wang--2019c|Wang et al. 2019c]] ). Recently, however, studies have proposed designs of CCS with a minimal increase in water requirements ( [[#Magneschi--2017|Magneschi et al. 2017]] ; [[#Mikunda--2021|Mikunda et al. 2021]] ).

Older thermal power plants can be retrofitted to mitigate climate impacts by altering and redesigning the cooling systems ( [[#Westlén--2018|Westlén 2018]] ), although the costs for these solutions may be high. For example, dry cooling may be used instead of once-through cooling; however, it lowers thermal efficiency and would leave plants vulnerable to ambient temperature increase ( [[#Ahmad--2021|Ahmad 2021]] ). Closed-circuit cooling is much less sensitive to water temperature than once-through cooling ( [[#Bonjean%20Stanton--2016|Bonjean Stanton et al. 2016]] ). Modifying policies and regulation of water and heat emissions from power plants may also be used to mitigate plant reliability problems induced by climate change ( [[#Eisenack--2016|Eisenack 2016]] ; [[#Mu--2020|Mu et al. 2020]] ), albeit with potential impacts for other water users and ecology. Improvements in water use and thermal efficiencies and the use of transmission capabilities over large geographical regions to mitigate risks on individual plants are also possible mitigation options ( [[#Miara--2017|Miara et al. 2017]] ).

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