Nevada CO2 Emissions Analysis

Heatwaves have become more frequent in the United States since the 1960s, while extreme cold temperatures and cold waves are less frequent. Recent record-setting hot years are projected to be- come common in the near future for the United States, as annual average temperatures continue to rise. Annual average temperature over the contiguous United States has increased by 1.8°F (1.0°C) for the period 1901-2016; over the next few decades (2021-2050), annual average temperatures are expected to rise by about 2.5°F for the United States, relative to the recent past (average from 1976-2005), under all plausible future climate scenarios. The Incidence of large forest fires in the western United States and Alaska has increased since the early 1980s and is projected to further increase in those regions as the climate changes, with profound changes to regional ecosystems. Annual trends toward earlier spring melt and reduced snowpack are already affecting water re- sources in the western United States and these trends are expected to continue. Under higher scenar- ios, and assuming no change to current water resources management, chronic, long-duration hydro- logical drought is increasingly possible before the end of this century. The magnitude of climate change beyond the next few decades will depend primarily on the amount of greenhouse gases (especially carbon dioxide) emitted globally. Without major reduc- tions in emissions, the increase in annual average global temperature relative to preindustrial times could reach 9°F (5°C) or more by the end of this century. With significant reductions in emissions, the Increase in annual average global temperature could be limited to 3.6°F (2°C) or less. The global atmospheric carbon dioxide (CO) concentration has now passed 400 parts per million (ppm), a level that last occurred about 3 million years ago, when both global average tempera- ture and sea level were significantly higher than today. Continued growth in CO₂ emissions over this century and beyond would lead to an atmospheric concentration not experienced in tens to hundreds of millions of years. There is broad consensus that the further and the faster the Earth system is pushed towards warming, the greater the risk of unanticipated changes and impacts, some of which are poten- tially large and irreversible. The observed increase in carbon emissions over the past 15-20 years has been consistent with higher emissions pathways. In 2014 and 2015, emission growth rates slowed as economic growth became less carbon-Intensive. Even if this slowing trend continues, however, it is not yet at a rate that would limit global average temperature change to well below 3.6°F (2°C) above preindustrial levels. 23 23

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