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17 although precipitation patterns are expected to become more variable, projections of annual totals show no clear signal of significant directional change. San Leandro may experience higher average daily temperatures and more extreme heat days Temperature and precipitation projections were provided by Four Twenty Seven using scenarios from the Intergovernmental Panel on Climate Change (IPCC). The Representative Concentration Pathway (RCP) 8.5 is characterized by a minimal greenhouse gas mitigation effort and high emissions scenario, resulting in the largest increase in radiative forcing and warming, while RCP 4.5 is considered a moderate mitigation scenario where climate action limits the amount of global emissions.27 Future temperature rise scenarios vary based on which government policies and commercial and human actions are actually implemented in the coming years and how well these climate change mitigation efforts work cumulatively. While, temperatures in San Leandro are projected to increase under both scenarios, daily average temperatures are projected to increase by about twice as much under the RCP 8.5 (high emissions) scenario than under the RCP 4.5 (lower emissions) scenario by the end of the century. (RCP 8.5 leads to a 6.9 to 8.8 ◦F increase in daily average temperature, compared to 3.2 to 4.9 ◦F increase under RCP 4.5.) Temperatures in San Leandro may be two to four degrees higher According to the model baseline (1970-2000), San Leandro’s climate has been characterized by a daily average temperature of about 58.6 ◦F, an average maximum temperature of 67 ◦F, and an average minimum temperature of 50.2 ◦F.28 Temperature projections exhibit a clear trend toward warmer average temperatures and more frequent occurrence of high or even extreme temperature events. Under RCP 8.5 (a high emissions scenario), daily average temperatures are projected to increase from the model baseline by as much as 2.5 ◦F to 3.5 ◦F, daily minimum temperatures by about 2.5 ◦F to 3.5 ◦F, and daily maximum temperatures by about 2.5 ◦F to 4 ◦F between now and mid-century. Even under RCP 4.5 (a lower emissions scenario), temperature increases are anticipated, and projections range between an average daily increase of as much as 2.5 ◦F and 3.5 ◦F by mid-century. By the end of the century, temperature changes are estimated to be substantial, for daily average, minimum, and maximum temperatures with the high-end of the range of RCP 8.5 temperature increase projections suggesting increases from about 7 ◦F to 9 ◦F.29 This means that San Leandro’s average maximum temperature would be comparable to current levels in San Luis Obispo, California. These projections do not indicate seasonal fluctuations, but yearly averages. The greatest potential impact of temperature increases lies in the relative increase in the severity of extreme heat and the frequency of hot days. According to the modelled historical baseline of San Leandro’s climate, the occurrence of temperatures exceeding 90 ◦F is rare.30 The average number of days over 90 ◦F is projected to rise significantly after mid-century. Under RCP 4.5, 90 ◦F days in San Leandro are projected to double by mid-century, with a threefold increase under RCP 8.5 over the same period. 27 IPCC. (2014). Scenario Process for AR5. Accessed at: http://sedac.ipcc-data.org/ddc/ar5_scenario_process/RCPs.html 28 Reclamation. (2013). 29 Reclamation. (2013). 30 Reclamation. (2013). 'Downscaled CMIP3 and CMIP5 Climate and Hydrology Projections: Release of Downscaled CMIP5 Climate Projections, Comparison with preceding Information, and Summary of User Needs', prepared by the U.S. Department of the Interior, Bureau of Reclamation, Technical Services Center, Denver, Colorado. 61