Climate Change Impacts Water Resources (Drought & Snow) Richard R. Heim Jr.

Transcription

1 Climate Change Impacts Water Resources (Drought & Snow) Richard R. Heim Jr. NOAA / NESDIS / Climate Monitoring Branch Asheville, North Carolina National Association of Clean Water Agencies Web Seminar, 10 March 2010 Topics To Cover: Climate Change Past, Present, and Projections Temperature, Precipitation, Water Vapor Trends Drought Snow and Ice 1

2 Four Types of Drought Drought operates on different time scales (short- vs. longterm) and impacts many different sectors. Meteorological drought atmospheric conditions resulting in the absence or reduction of precipitation Agricultural drought short-term dryness in the surface layers (root zone) at a critical time during the growing season, severely reducing crop yields Hydrological drought precipitation deficits over a prolonged period that affect surface or subsurface water supply, reducing streamflow, groundwater, reservoir & lake levels Socioeconomic drought relates the supply and demand of various commodities to drought References: International Meteorological Vocabulary, WMO, 1992 Meteorological Drought, AMS, 1997, Glossary National of Meteorology, Climatic AMS, Data Center 2000 Palmer Drought Index Created by Wayne Palmer in 1965 & 1968 Quickly accepted and became widely used Defines Drought as the Balance between Water Supply and Water Demand Consists of Short-term (Z Index, agricultural Crop Moisture Index), Meteorological (PDSI, PMDI), and Long-term (PHDI Palmer Hydrological Drought Index) Indices 2

3 The Past: What Has Happened The Palmer Drought Index is Useful for Examining Drought Extremes In North America the most severe droughts occurred in the 1930s. There is no indication of an overall trend in the observational record (dates back to 1900). In Mexico and the U.S. SW, the 1950s were the driest period, though droughts in the past 10 years now rival the 1950s drought. Observed Changes 3

4 Palmer Drought Index Percent area of contiguous U.S. back to 1900 for national drought assessments. Palmer Drought Index Contiguous U.S. The Palmer Drought Index can give a spatial as well as temporal perspective of drought. 4

5 Historical Drought By Location Paleoclimatic Data Paleo (past) climate Proxy indicators are used to quantify climate during the pre-instrumental period (including historic and geologic time) Tree rings Palynology (pollen analysis) Ice cores Deep sea cores Varves Geomorphic structures t (glacial l polish, glacial moraines, drumlins, eskers, etc.) Historical records (harvests, floods, etc.) National Glossary Climatic of Meteorology, Data Center AMS,

6 Dendroclimatology Relates tree rings to climate The width of each annual growth ring reflects the climatic conditions prevailing during the growing season Depends on species Ring width reflects temperature for some species Moisture conditions (rainfall, soil moisture) for other species Extending a chronology NOAA/NCDC Paleoclimatology Branch Why Is It Important to Know the Long-term Drought History of an Area? Two Examples: Jamestown! The Lost Colony! From 6

7 Why Is It Important to Know the Long-term Drought History of an Area? Droughts were more frequent, severe, and lasted longer in the pre-historical past. Water management compacts were negotiated during an unusually wet period Percent area of western U.S. in drought last 1200 years last 110 years Graph above: The black line shows the percentage of the area affected by drought (Palmer Drought Severity Index less than 1) in the West over the past 1,200 years. The red line indicates the average drought area in the years 900 to The blue horizontal line in the yellow box indicates the average during the period from 1900 to 2000, illustrating that the most recent period, during which population and water infrastructure grew rapidly in the West, was wetter than the long-term average (thin horizontal black line).189 Droughts shown in the period significantly exceed those that have occurred over the past 100 years. (USP, 2009) Graph to right: Percent area of western U.S. experiencing drought and wet spell conditions for January 1900-January 2010, based on PDSI < -1. 7

8 Palynology Relates pollen to climate Pollen grains which are washed or blown into lakes can accumulate in sediments and provide a record of past vegetation. Different types of pollen in lake sediments reflect the vegetation that was present around the lake, and therefore the climate conditions favorable for that vegetation. Palynology is the science that studies contemporary and fossil palynomorphs, including pollen, spores, dinoflagellate cysts, acritarchs, chitinozoans and scolecodonts, together with particulate organic matter (POM) and kerogen found in sedimentary rocks and sediments Wikipedia Each plant species grows best under specific climatic conditions Radiocarbon date the pollen in the core layers to create a chronology Pollen & Lake Sediment Chronologies Moon Lake, ND Mono Lake, Sierra Nevada Mtns, CA Punta Laguna, Yucatan, Mexico lake sediment cores: Relate periods of intense drought to collapse of Classic Maya civilization ~ AD Dry periods, 7120 to 7770 BP 16 8

9 Present Vegetation Types Vegetation Types 18,000 Years Ago (Last Glaciation) Source: Global land environments since the last interglacial Increasing Trend in Global Mean Temperatures *Through 2005 Source: IPCC, Bottom Map: The pattern of linear global temperature trends from 1900 to 2008 has not been uniform around the globe. National Climatic FAQ 3.1, Data Figure Center 1 9

10 Increasing Trend in Global Mean Temperatures Source: IPCC, *Through 2005 Bottom Maps: Patterns of linear global temperature trends from 1979 to 2005 estimated at the surface (left), and for the troposphere (right) from the surface to about 10 km altitude, from satellite records. Grey areas indicate incomplete data. Note the more spatially uniform warming in the satellite tropospheric record while the surface temperature changes more clearly relate to land and ocean. National Climatic FAQ 3.1, Data Figure Center 1 Figure 3.20 Increasing Trend in Water Vapor Linear trends in precipitable water (total column water vapor) in % per decade (top) and monthly time series of anomalies relative to the 1988 to 2004 period in % over the global ocean plus linear trend (bottom), from RSS SSM/I (updated from Trenberth et al., 2005a) (from IPCC, 2007). 10

11 Figure 3.21 Upper-tropospheric moistening as expressed by water vapor s radiative signature. [Shown are upward linear trends in T2 T12 for 1982 to 2004 (0.1 ºC per decade; top) and monthly time series of the global-mean (80 N to 80 S) anomalies relative to 1982 to 2004 (ºC) and linear trend (dashed; bottom). Data are from the RSS T2 and HIRS T12 (Soden et al., 2005). The map is smoothed to spectral truncation T31 resolution. (IPCC, 2007).] Precipitation Trends (%/Century) for Various Categories (Percentiles) of Precipitation Intensity Observed 20 th Century Trends 11

12 Observed trends (% per decade) for in contribution to total annual precipitation of very wet days (95 th percentile). Trend in annual land precipitation amounts, for (top) and (bottom). [Based on NCDC s GHCN precipitation data. The percentage is based on the means for the 1961 to 1990 period. Areas in grey have insufficient data to produce reliable trends. The minimum number of years required to calculate a trend value is 66 for 1901 to 2005 and 18 for 1979 to Trends significant at the 5% level are indicated by black + marks. (IPCC, 2007).] 12

13 FAQ 3.2, Figure 1 Palmer Drought Dominant spatial pattern of Palmer Drought Index (67% of variance). (from IPCC, 2007). Positive Phase Positive Phase: Red & Yellow = Drier, Blue & Green = Wetter. Negative Phase: Red & Yellow = Wetter, Blue & Green = Drier. Negative Phase Snow Cover Trends N. Hemisphere 13

14 Spring (March-April) Northern Hemisphere snow cover area (from IPCC, 2007). Values before 1972 are based on the station-derived snow cover index of Brown (2000); values beginning in 1972 are from the NOAA satellite data set. The smooth curve shows decadal variations, and the shaded area shows the 5 to 95% range of the data estimated after first subtracting the smooth curve. Satellite snow cover extent, 1966-present, North America by month 14

15 In a warming world, precipitation may fall more as liquid rain than snow. Significant impact on water supply in the West Snow Drought Above-normal precipitation p Below-normal snowpack 15

16 Trend in Number of Days With Snowfall 0.1 inch Observed Spring Snowmelt Dates Date of onset of spring runoff pulse. Reddish-brown circles indicate significant trends toward onsets more than 20 days earlier. Lighter circles indicate less advance of the onset. Blue circles indicate later onset. The changes depend on a number of factors in addition to temperature, including altitude and timing of snowfall. (USP, 2009). 16

17 The Future: What the Models Say Will Happen Model projections of annual precipitation averaged over compared to drier wetter Changes are annual means for the SRES A1B scenario for the period 2080 to 2099 relative to 1980 to To indicate consistency in the sign of change, regions are stippled where at least 80% of models agree on the sign of the mean change. Soil moisture and runoff changes are shown at land points with valid data from at least 10 models. (IPCC, 2007). 0.5 mm/day X 30 days / 25.4 mm/inch = 0.59 inch/month 17

18 Model projections of seasonal precipitation averaged over compared to Changes are seasonal means for the period 2080 to 2099 relative to 1980 to 1990, simulated by 15 climate models. Hatching indicates highest confidence. (USP, 2009). Model projections of annual soil moisture averaged over compared to drier wetter Changes are annual means for the SRES A1B scenario for the period 2080 to 2099 relative to 1980 to To indicate consistency in the sign of change, regions are stippled where at least 80% of models agree on the sign of the mean change. Soil moisture and runoff changes are shown at land points with valid data from at least 10 models. (IPCC, 2007). 18

19 Model projections of annual evapotranspiration (ET) averaged over compared to less ET more ET (warmer) Changes are annual means for the SRES A1B scenario for the period 2080 to 2099 relative to 1980 to To indicate consistency in the sign of change, regions are stippled where at least 80% of models agree on the sign of the mean change. Soil moisture and runoff changes are shown at land points with valid data from at least 10 models. (IPCC, 2007). Model projections of annual runoff averaged over compared to drier wetter Changes are annual means for the SRES A1B scenario for the period 2080 to 2099 relative to 1980 to To indicate consistency in the sign of change, regions are stippled where at least 80% of models agree on the sign of the mean change. Soil moisture and runoff changes are shown at land points with valid data from at least 10 models. (IPCC, 2007). 19

20 Increase in extreme daily precipitation For a mid-range emission scenario, daily precipitation so heavy that it now occurs only once every 20 years is projected to occur every eight years or so by the end of this century over much of Eastern North America. SAP 3.3 *CCSP: Climate Change Science Program CCSP 3.3 *SAP: Synthesis and Assessment Product 39 Projections for heavy and light precipitation Models project heavy precipitation will increase and light precipitation decrease. Potential increase in flooding and increase in dry spells 40 20

21 annual total precipitation / number of wet days minus less intense more intense * annual maximum number of consecutive dry days minus * Standardized relative to each 20-year mean fewer dry days more dry days * Less snow cover compared to more less Percent snow depth changes in March (only calculated l where climatological snow amounts exceed 5 mm of water equivalent), as projected by the Canadian Regional Climate Model (CRCM; Plummer et al., 2006), driven by the Canadian General Circulation Model (CGCM), for 2041 to 2070 under SRES A2 compared to 1961 to (IPCC, 2007). 21

22 Expected changes in regional climate change for mean and extreme precipitation, p drought, and snow. (IPCC, 2007). Potential water supply conflicts by 2025 The map shows regions in the West where water supply conflicts are likely to occur by 2025 based on a combination of factors including population trends and potential endangered species needs for water. The red zones are where the conflicts are most likely to occur. This analysis does not factor in the effects of climate change, which h is expected to exacerbate many of these already-identified issues. (USP, 2009). 22

23 Precipitation Summary Observed Changes Changes in precipitation patterns and intensity it Changes in the incidence of drought Widespread melting of snow and ice Increasing atmospheric water vapor Increasing evaporation Increasing water temperatures Reductions in lake and river ice changes in soil moisture and runoff -- IPCC 4 th Assessment Report, 2007 and Global Climate Change Impacts in the United States, 2009 Precipitation Summary Projected Changes Floods and droughts are likely to become more common and more intense as regional and seasonal precipitation patterns change, and rainfall becomes more concentrated into heavy events (with longer, hotter dry periods in between). Precipitation and runoff will undergo changes based on region & season. In areas where snowpack dominates, the timing of runoff will continue to shift to earlier in the spring and flows will be lower in late summer. Surface water quality and groundwater quantity will be affected. Climate change will place additional burdens on already stressed water systems. -- IPCC 4 th Assessment Report, 2007 and Global Climate Change Impacts in the United States,

24 Thank You! NCDC Climate Monitoring Branch Reports & Products: Global Climate Change Impacts in the United States: Intergovernmental Panel on Climate Change (IPCC) : National Integrated Drought Information Systems (NIDIS): 24