Projected future climate: Difference between revisions
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As described in [[Recent climate change]], the climate of the Colorado River Basin has become substantially warmer in the past 40 years, very likely due to human changes to the atmosphere and climate system. Meanwhile, average precipitation in the basin has not clearly changed, but the underlying atmospheric processes (e.g., circulation patterns, water vapor content) are already being influenced by the warming global climate. | As described in [[Recent climate change]], the climate of the Colorado River Basin has become substantially warmer in the past 40 years, very likely due to human changes to the atmosphere and climate system. Meanwhile, average precipitation in the basin has not clearly changed, but the underlying atmospheric processes (e.g., circulation patterns, water vapor content) are already being influenced by the warming global climate. | ||
Both basic physics and our most sophisticated tools (global climate models; GCMs) tell us that further warming will occur in the basin over at least the next several decades, at a similar or greater rate than what has been observed since 1980. Neither the physics nor the GCMs present a clear picture | Both basic physics and our most sophisticated tools (global climate models; GCMs) tell us that further warming will occur in the basin over at least the next several decades, at a similar or greater rate than what has been observed since 1980. Neither the physics nor the GCMs present a clear picture of future precipitation change, however. | ||
==Relevance== | ==Relevance== | ||
Continued warming of the basin’s climate will further impact the surface water balance and hydrology, | Continued warming of the basin’s climate will further impact the surface water balance and hydrology, leading to chronic drought conditions by today's standards in the absence of a large increase in average precipitation. More warming will also further stress the basin’s ecosystems and species, potentially beyond thresholds for viability in some cases. | ||
basin’s ecosystems and species, potentially beyond thresholds for viability in | |||
==Future temperature== | |||
[[File:Southwest_JJA_Tmax_figure.png|thumb|700px|Figure 2. Fraction of the area of the Southwest U.S. (UT, CO, AZ, NM) experiencing extremely warm (upper 10%; red bars) and extremely cool (lower 10%; blue bars) daily high temperatures averaged over the summer (June-August), 1895-2020. Note the abrupt increase in the area experiencing extremely warm summer daily highs after 1995. The green line is a 9-point smoothing filter to emphasize decadal-scale variability. (Chart: NOAA NCEI https://www.ncdc.noaa.gov/extremes/cei/; annotation on y-axis by Jeff Lukas)]] | [[File:Southwest_JJA_Tmax_figure.png|thumb|700px|Figure 2. Fraction of the area of the Southwest U.S. (UT, CO, AZ, NM) experiencing extremely warm (upper 10%; red bars) and extremely cool (lower 10%; blue bars) daily high temperatures averaged over the summer (June-August), 1895-2020. Note the abrupt increase in the area experiencing extremely warm summer daily highs after 1995. The green line is a 9-point smoothing filter to emphasize decadal-scale variability. (Chart: NOAA NCEI https://www.ncdc.noaa.gov/extremes/cei/; annotation on y-axis by Jeff Lukas)]] | ||
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== | ==Future precipitation== | ||
As discussed in [[Climate patterns and variability]], annual precipitation in the basin is highly variable, and there are no recent trends in annual or seasonal precipitation that clearly emerge from the background “noise” of historical year-to-year and decadal variability, as with temperature. But the most recent two decades does stand out for overall dryness, which is accentuated by the preceding two wet decades in the 1980s and 1990s (Figures 3 & 4). By slight margins, 2000-2020 has been the driest 21-year period on record in both the Upper Basin (with 94% of the 20th-century average) and Lower Basin (88% of the 20th-century average). The period since 2000 also includes the driest single water years on record in the Upper Basin (2018) and Lower Basin (2002). | As discussed in [[Climate patterns and variability]], annual precipitation in the basin is highly variable, and there are no recent trends in annual or seasonal precipitation that clearly emerge from the background “noise” of historical year-to-year and decadal variability, as with temperature. But the most recent two decades does stand out for overall dryness, which is accentuated by the preceding two wet decades in the 1980s and 1990s (Figures 3 & 4). By slight margins, 2000-2020 has been the driest 21-year period on record in both the Upper Basin (with 94% of the 20th-century average) and Lower Basin (88% of the 20th-century average). The period since 2000 also includes the driest single water years on record in the Upper Basin (2018) and Lower Basin (2002). | ||
Revision as of 17:25, 11 May 2021
Overview
As described in Recent climate change, the climate of the Colorado River Basin has become substantially warmer in the past 40 years, very likely due to human changes to the atmosphere and climate system. Meanwhile, average precipitation in the basin has not clearly changed, but the underlying atmospheric processes (e.g., circulation patterns, water vapor content) are already being influenced by the warming global climate.
Both basic physics and our most sophisticated tools (global climate models; GCMs) tell us that further warming will occur in the basin over at least the next several decades, at a similar or greater rate than what has been observed since 1980. Neither the physics nor the GCMs present a clear picture of future precipitation change, however.
Relevance
Continued warming of the basin’s climate will further impact the surface water balance and hydrology, leading to chronic drought conditions by today's standards in the absence of a large increase in average precipitation. More warming will also further stress the basin’s ecosystems and species, potentially beyond thresholds for viability in some cases.
Future temperature
Future precipitation
As discussed in Climate patterns and variability, annual precipitation in the basin is highly variable, and there are no recent trends in annual or seasonal precipitation that clearly emerge from the background “noise” of historical year-to-year and decadal variability, as with temperature. But the most recent two decades does stand out for overall dryness, which is accentuated by the preceding two wet decades in the 1980s and 1990s (Figures 3 & 4). By slight margins, 2000-2020 has been the driest 21-year period on record in both the Upper Basin (with 94% of the 20th-century average) and Lower Basin (88% of the 20th-century average). The period since 2000 also includes the driest single water years on record in the Upper Basin (2018) and Lower Basin (2002).
Drought indicators
=Other climate metrics
Data and tools
There are several climate tools that are useful for plotting and examining time-series and recent trends in temperature, precipitation, and other climate variables over specific areas (states, counties, river basins, etc.). Each tool depicts one or more Gridded climate datasets (LINK), so it is advised that users of the tools familiarize themselves with these datasets as well.
NOAA NCEI Climate at a Glance - Regional Time Series
The “CAG” tool is a versatile tool that can be used to generate many types of charts, maps, and analyses from NOAA’s official nClimGrid monthly gridded climate dataset. The link above opens the Regional and Time Series options, allowing users to plot temperature, precipitation, and other variables for the Upper Basin, Lower Basin, or many other U.S. basins and regions. All variables can be plotted from 1895 to present.
Additional resources
State of the Science Report
Chapter 2 of the State of the Science report describes recent climate changes in greater detail, in section 2.10.
NCA4 Climate Science Special Report
The 2018 Climate Science Special Report (CSSR), Volume 1 of the Fourth National Climate Assessment (NCA4), describes the historical record and likely causes of recent temperature change (Ch 6.1, 6.2) and recent precipitation change (Ch. 7.1) in the U.S.
Research directions
New and Notable Research (2020-present)
[<URL FOR PAPER>]
Summary