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Means, Extremes and the Changing Character of Maine’s Climate Bradfield Lyon Climate Change Institute and School of Earth and Climate Sciences, University of Maine, Orono 2016 Maine Sustainability & Water Conference Augusta Civic Center, Augusta, Maine 29 March, 2016 Outline • Changes in the mean can affect changes in extremes: Temperature Atmospheric Moisture and Precipitation • A warmer climate increases precipitation intensity AND the severity of drought (i.e., an enhanced hydrologic cycle) • Impacts of extremes: Extreme precipitation Extreme temperature Tipping Points • Conclusions Means and Extremes -- Temperature Maine’s Climate Zones Distribution of Monthly Temperature Departures from Average 1981-2010 (all Maine climate zones) Number of Months 140 120 100 80 60 40 20 0 Source: www.manomet.org -10 -8 -6 -4 -2 0 2 4 6 8 10 Temp. Departure from Average (deg. F) Source: climatenexus.org Means and Extremes -- Temperature Now consider temperature departures from an 1896-2015 average for the two periods 1896-1955 and 1956-2015 separately… 120 1896-1955 Number of Months 100 1956-2015 80 60 40 20 0 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 Departure from 1896 to 2015 average (deg. F) 40 30 20 Number of Months Compute the differences Divide the number of between the two months in each category: distributions… latest period/earlier period 2.5 18 16 2.0 14 12 1.5 10 8 1.0 6 4 0.5 2 0.0 0 10 0 A +10F departure is 16x more frequent… -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 -10 -20 -30 -12 -10 -10 0 2 warm 2 4 4months -40 -12 -8-8 cold -6 -6months -4 -4 -2 -2 0more 6 68 fewer -50 Departure from 1896 to 2015 average (deg. F) 810 Means and Extremes -- Temperature Number of Days with Maximum Temperature > 90 deg. F 1971-2000 2041-2070 Source: National Climate Assessment 2014 Means and Extremes -- Precipitation 120 100 80 60 40 20 0 -4.0 -3.5 -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 Number of Months 140 Precipitation Departure (inches) 5 0 -5 -4.0 -3.5 -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 Difference: Ratio: Recent Recent/Earlier – Earlier period Period Number of Months 10 -10 -15 -20 Precipitation Departure (inches) Means and Extremes Consider changes in 20-yr moving averages (mean & variability) Avg. 4.5 Variability 2.5 *** 1.5 2014 2004 1994 1984 1974 1964 1954 1944 1934 -0.5 1924 0.5 1914 Temperature (all months) Temperature (deg. F) 3.5 -1.5 -2.5 Avg. Variability ** 1.5 1.0 0.5 -0.5 2014 2004 1994 1984 1974 1964 1954 1944 1934 1924 0.0 *** 1914 Precipitation (all months) Precipitation (inches) 2.0 Atmospheric Water Vapor Saturation Vapor Pressure (hPa) A Warmer Atmosphere can Hold More Moisture Atmospheric Water Vapor Increases ~7% for every 1°C of warming Trends 1973-1995 Weather Balloons Reanalysis (same locations) Temp. (deg. C) Trenberth et al. (2005) Atmospheric Water Vapor Low-Level temperature and Water Vapor Content over Maine 1979-2014 2.02.0 Temp. Departure (deg. C) Water Content Departure (mm) 1.51.5 1.01.0 0.50.5 0.00.0 1979 1979 -0.5 -0.5 -1.0 -1.0 -1.5 -1.5 -2.0 -2.0 1984 1984 1989 1989 1994 1994 1999 1999 2004 2004 2009 2009 2014 Atmospheric Water Vapor -- Reminder Rainfall (inches) 29 October, 2015 Water vapor may travel large distances before arriving in Maine… Atmospheric Water Vapor -- Conceptual More water vapor = Heavier Precipitation Atmospheric Water Vapor -- Models • The In climate amount models, of energy this required results into fewer evaporate light precipitation water from the days earth’ and more surface heavy is limited: and extreme In a warmer precipitation climate days... it takes more time to “recharge” the atmospheric water vapor content to its new, higher value… Figure Source: US Climate Change Science Program Atmospheric Water Vapor -- Observations Observed trends in precipitation over the past 50 years show an increase in the amount of precipitation occurring during extreme events… Shaleen Jain et al. Source: National Climate Assessment 2014 Drought “dry” “wet” Maine State Average of the Palmer Drought Severity Index 1895-2015 “Severe Drought” A warming climate exacerbates drought… Additional atmospheric heating further drys the surface, increases temperature. Greater heating from greenhouse gases Current Climate Future Climate Drought -- What Lurks Below the Surface Drought Conditions in Maine, 1999-2002: A Historical Perspective, USGS 2004 * * Source: USGS http://pubs.usgs.gov/fs/2004/3021/ Changing Character of Maine’s Climate Source: Maine’s Climate Future 2009, University of Maine Changing Character of Maine’s Climate Climatological Snowfall Change in SWE/Total Prcp Projected Change in Snow Maine’s Climate Future Source: Portland Press Herald Huntington et al. 2004 Journal of Climate Impacts -- Extreme Rainfall Urban Flooding Water Quality (DOC) Flooding in Portland, ME Aug 13, 2014 Photo Source: earthsky.org Balch et al., 2016 Erosion Fecal Coliform Bacteria gulfofmaine.org From Tilburg et al. 2015 Impacts – Temperature Tipping Points Aug. 11, 2015 Water intake > 75F Millstone Nuclear power station in CT Water Intake too Warm… www.centralmaine.com Boston Globe August 11, 2015 Boston Globe ... A power line failure knocked several power substations out August 9, 2013 of commission, leaving 13,000 Central Maine Power customers without electricity… During the height of last month’s heat wave, millions of people in northern New England were urged to conserve energy… at the same time, at least two wind farms in Maine and Vermont were ordered to reduce the amount of electricity they provided. …weakness in the rural system linking wind turbines to the power grid mean wind companies are routinely taken offline or have their output reduced. Conclusions • Changes in the mean may accompany changes in the full distribution of a climate variable: changes the probability of extremes. • A warmer atmosphere can hold more water vapor (7%/deg. C) Increased rainfall Increased extreme rainfall • A warming climate is associated with an enhanced hydrologic cycle: heavier precipitation and exacerbated drought • Impacts are numerous and varied: erosion, water quality, flooding, heat stress,… • Tipping points: Non-extremes can have substantial impacts • (e.g., power generation, dissolved O2, SLR,...) Supplemental Slides Source: IPCC Water Vapor Trends (SSMI) IPCC Fourth Assessment Report http://waterwatch.usgs.gov/ Water Vapor Maximum Solubility Soden et al. 2005 Climate models are able to capture this effect… How is Precipitation Changing in Maine by Season? Look at 20-yr changes in the average & variability Mar-May Sep-Nov * Jun-Aug * *** Dec-Feb *