finding 25.5 : key-message-25-5

The ability of hydropower and fossil fuel electricity generation to meet growing energy use in the Southwest is decreasing as a result of drought and rising temperatures (very likely, very high confidence). Many renewable energy sources offer increased electricity reliability, lower water intensity of energy generation, reduced greenhouse gas emissions, and new economic opportunities (likely, high confidence).

This finding is from chapter 25 of Impacts, Risks, and Adaptation in the United States: The Fourth National Climate Assessment, Volume II.

Process for developing key messages:

The authors examined the scientific literature in their areas of expertise. The team placed the highest weight on scientific articles published in refereed peer-reviewed journals. Other sources included published books, government technical reports, and, for data, government websites. The U.S. Global Change Research Program issued a public call for technical input and provided the authors with the submissions. The University of Arizona Center for Climate Adaptation Science and Solutions organized the Southwest Regional Stakeholder Engagement Workshop on January 28, 2017, with over 70 participants at the main location in Tucson, AZ, and dozens of participants in Albuquerque, NM, Boulder, CO, Davis, CA, Los Angeles, CA, Reno, NV, and Salt Lake City, UT, all connected by video. Participants included scientists and managers. The author team met the following day for their only meeting in person. Subsequently, authors held discussions in regular teleconferences. Many chapter authors met at the all-author meeting March 26–28, 2018, in Bethesda, MD.

Description of evidence base:

Numerous studies link Southwest hydrologic drought with a decline in renewable hydroelectricity generation in the region. Hydroelectric generation depends on runoff to fill reservoirs to maximize generation capacity.7db8f4ff-81fb-4d22-949a-076aab55aa86,e4a5a03e-0138-4ebb-98ad-6fb28ec56be5 During the California drought, which was intensified by climate change,ba57f86f-c42f-4bba-83f6-676d6875c176,89e08a41-6091-45fa-a92e-6168a90a8151 hydroelectric generation in California fell from 43 trillion watt-hours (TWh) in 2011 before the drought to 14 TWh in 2015 during the drought.8347d2b2-855d-4765-b7a2-6d2a9e0c99f4 Climate change also reduced the snowpackfd8947cd-6705-4ec7-9126-0444a730d48a,3c0fc226-ca97-4b80-aeb7-517cd5d1acff,e450ba2c-db69-43c8-8af4-e0c8ce7c8f2f,0d8b090e-e060-4f9d-a442-b7e050608a20 and river runoff on which hydroelectric generation depends.7db8f4ff-81fb-4d22-949a-076aab55aa86,e4a5a03e-0138-4ebb-98ad-6fb28ec56be5

Similarly, low reservoir levels in Lake Mead—which is formed by damming the Colorado River—driven by reduced Colorado River runoffa42c4f5e-f16b-4196-af05-61f117e0491d,3d53beca-0617-4351-a7e9-f5af06a049dc can reduce the efficiency and production levels of hydropower at Hoover Dam.

Fossil fuel generation efficiency depends on the temperature and availability of the external cooling water. Warming could reduce energy efficiency up to 15% across the Southwest by 2100.8c12cc4c-3448-4055-b7a2-e03ead1c2572 Higher temperatures also increase electric resistance in transmission lines, causing transmission losses of 7% under higher emissions.673a11a4-4d3c-4303-af82-29de1ca24bd6 Replacing fossil fuel generation with solar power renewables reduces greenhouse gas emissions and water use per unit of electricity generated.437ba8f2-66cf-44f5-8bea-173c02458858 This supports the assertion that increasing solar energy generation in the Southwest could meet the energy demand no longer being met by hydropower and fossil fuel as well as the expected increase in energy use in the future.

Solar energy production is also an economic opportunity for the region. The energy potential for renewable energy is estimated to range from one-third to over ten times 2013 generation levels from all sources.2c0c6750-e017-4590-b7aa-e1756bc7854b The lower range assumes capacity requirements remain at 2013 levels,2c0c6750-e017-4590-b7aa-e1756bc7854b but recent data show an upward trend in Southwest energy use.ab3cc54d-c74f-4a6d-8746-efa051c2e97e

The high potential for solar energy projects in the Southwest and the extent of federally owned land in the Southwest (well over half the total surface area for the six-state region) prompted the Bureau of Land Management (BLM) and the U.S. Department of Energy to conduct a programmatic environmental impact analysis of a new Solar Energy Program to further support utility-scale solar energy development on BLM-administered lands.2c0c6750-e017-4590-b7aa-e1756bc7854b,607ad598-58b0-46e3-8371-bede11c93089 This potential capacity, combined with the increasingly competitive cost of solar and wind,1f8c0eab-9564-4064-bd8e-b98c135744e9 presents economic opportunities for the region and an opportunity to reduce overall greenhouse gas emissions.

Solar and renewable energy jobs are increasing. The solar workforce increased 25% in 2016, while wind employment increased 32%.92b75533-4ebe-4cad-af48-6789b4627f47 Jobs in low-carbon-emission generation systems, including renewables, nuclear, and advanced low-emission natural gas, comprise 45% of all the jobs in the electric power generation and fuels technologies.92b75533-4ebe-4cad-af48-6789b4627f47 Growing Southwest energy use, competitive prices for renewables, and the renewable energy potential of the Southwest favor the replacement of fossil-fuel-generated energy by renewable solar and wind energy.

New information and remaining uncertainties:

Climate model projections of the future diverge on whether precipitation may increase or decrease for much of the region, so hydroelectric power changes may exhibit spatial variation. The amount of runoff is a key factor driving the generation potential for hydroelectric power. A key uncertainty is how much hydroelectricity generation will decline. Some projections of higher-than-average precipitation in the northern parts of the Southwest could roughly offset declines in warm-season runoff associated with warming.9d8a98fa-0338-486a-b902-cd02d43cae87

Energy demand in the Southwest is increasing, but the rate of growth is uncertain.561029d5-4494-43bf-98d2-96ad38606588 Changes in energy market prices cause future uncertainty in the future mix of energy sources for the Southwest.2c0c6750-e017-4590-b7aa-e1756bc7854b The low cost of natural gas and the competitive cost of solar and wind renewables make it somewhat certain the proportion of the energy generated from these sources will continue to increase and offset reductions in traditional fossil-fuel-generated energy, reducing overall greenhouse gas emissions.1f8c0eab-9564-4064-bd8e-b98c135744e9 Renewable energy job growth potential is also uncertain and depends on the factors mentioned above.92b75533-4ebe-4cad-af48-6789b4627f47

Additionally, daily to multiyear variation in coastal cloud cover affects solar electricity generation potential along the California coast.beba4436-bbd0-43c2-bd04-e6000c5e4a27,60730cd1-dc90-4add-957b-2a32981cf398,566f09cf-bf52-4392-90d5-3b96d6c42c93,753f4b51-bd4f-49c4-b519-0789b10b1a89

Assessment of confidence based on evidence:

Hydrological drought in California reduced hydroelectric generation8347d2b2-855d-4765-b7a2-6d2a9e0c99f4 and fossil fuel electricity generation efficiencies. Drought and rising temperatures under climate change can reduce the ability of hydropower and fossil fuel electricity generation to meet growing energy use in the Southwest (very likely, very high confidence). Renewable solar and wind energy offers increased electricity reliability, lower water intensity for energy generation, reduced greenhouse gas emissions, and new economic opportunities (likely, high confidence).

This finding was derived from scenario rcp_4_5
This finding was derived from scenario rcp_8_5

References :

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