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

==== 6.7.1.2 Low-carbon Energy Transition Strategies ====

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There are multiple technological routes to reduce energy system emissions ( [[#6.6|Section 6.6]] ). Here we discuss three of these: (i) decarbonising primary energy and electricity generation; (ii) switching to electricity, bioenergy, hydrogen, and other fuels produced from low-carbon sources; and (iii) limiting energy use through improvement of efficiency and conservation. CDR is discussed in [[#6.7.1.3|Section 6.7.1.3]] Fossil fuel transitions are discussed in [[#6.7.4|Section 6.7.4]] .

'''Decarbonising primary energy and electricity generation.''' Limiting warming to well below 2°C requires a rapid and dramatic increase in energy produced from low- or zero-carbon sources ( ''high confidence'' ). Low- and zero-carbon technologies produce 74–82% (interquartile range) of primary energy in 2050 in scenarios limiting warming to 1.5°C (&gt;50%) with no or limited overshoot and 55–68% in scenarios limiting warming to 2°C (&gt;67%) (Figure 6.29). The share of low-carbon technologies in global primary energy supply today is below 20% (Chapter 3, [[#6.3|Section 6.3]] , and Figure 6.29). The percentage of low- and zero-carbon energy will depend in part on the evolution of energy demand – the more that energy demand grows, the more energy from low- and zero-carbon sources will be needed, and the higher the percentage of total primary energy these sources will represent.

Low- and zero-carbon sources produce 97–99% of global electricity in 2050 in scenarios limiting warming to 1.5°C (&gt;50%) with no or limited overshoot and 93–97% in scenarios limiting warming to 2°C (&gt;67%) (Figure 6.29) ( ''medium confidence'' ). Decarbonising electricity generation, in tandem with increasing use of electricity (see below), is an essential near-term strategy for limiting warming. The increase in low- and zero-carbon electricity will occur while electricity demand grows substantially. Studies have projected that global electricity demand will roughly double by 2050 and quadruple to quintuple by 2100 irrespective of efforts to reduce emissions ( [[#Bauer--2017|Bauer et al. 2017]] ; [[#Luderer--2017|Luderer et al. 2017]] ; [[#IEA--2019a|IEA 2019a]] ).

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'''Figure 6.29 | Reductions in CO''' 2 '''emissions relative to 2020 levels for scenarios that limit/return warmin''' '''g to 1.''' '''5°C (&gt;50%) with no or limited/after a high, overshoot, and scenarios that limit warming to 2°C (&gt;67%), with action starting in 2020 or NDCs until 2030, during 2030–2050.''' Boxes indicate 25th and 75th percentiles while whiskers indicate 5th and 95th percentiles. Source: AR6 Scenarios Database '''.'''

Renewable energy, especially generation from solar and wind, is likely to have an important role in many low-carbon electricity systems. The contributions of wind and solar electricity will depend on their levelised costs relative to other options, integration costs, system value, and the ability to integrate variable resources into the grid ( [[#6.6|Section 6.6]] ). Electric sector technology mixes will vary by region but will typically include additional resources such as hydropower, nuclear power, fossil generation with CCS, energy storage resources, and geothermal energy, among others. Contributions of different options vary widely across scenarios based on different assumptions about these factors (Figure 6.30).

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'''Figure 6.30 | Shares of low-carbon energy (all sources except unabated fossil fuels) and bioenergy (including both traditional and commercial biomass) in total primary energy, and solar+wind, CCS and nuclear in electricity for scenarios that limit/return warming to''' '''1.''' '''5°C (&gt;50%) with no or limited/after a high, overshoot, and scenarios that limit warming to 2°C (&gt;67%), with action starting in 2020 or NDCs until 2030, during 2030–2050''' (Source: AR6 Scenarios Database). Boxes indicate 25th and 75th percentiles while whiskers indicate 5th and 95th percentiles.

Nonetheless, it is likely that wind and solar will dominate low-carbon generation and capacity growth over the next couple of decades due to supporting policies in many countries, and due to their significant roles in early electric sector decarbonisation, alongside reductions in coal generation ( [[#Bistline--2021b|Bistline and Blanford 2021b]] ; [[#Pan--2021|Pan et al. 2021]] ). Clean firm technologies play important roles in providing flexibility and on-demand generation for longer durations, though deployment of these technologies is typically associated with deeper decarbonisation levels (e.g., beyond 70–80% reductions), which are likely to be more important after 2030 in many regions, and with more limited CDR deployment ( [[#Baik--2021|Baik et al. 2021]] ; [[#Bistline--2021a|Bistline and Blanford 2021a]] ; [[#Williams--2021a|Williams et al. 2021a]] ).

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