Climate Change: Science Basics and Impacts Around the Great Lakes Jeffrey C. Rogers Department of Geography and Atmospheric Science Program State Climate Office for Ohio The Ohio State University May 6, 2010 Ohio State University Climate Change Webinar Series Climate Change & Water Resource Impacts in the Great Lakes Region

Overview Scientific basics of climate change associated with global warming. – The gases, their sources, temporal changes, role in climate change. Currently observed & the Predicted changes in both air temperature and in rainfall intensity. Potential changes in Great Lakes precipitation patterns and water levels.

What are Greenhouse Gases? Greenhouse gases (i) absorb outward bound infrared radiation from the earth’s surface. (ii) Delay the return of infrared radiation to space (iii) warm the atmosphere. The “greenhouse effect” modulates radiation in the earth-atmosphere system.

Greenhouse Gases (GHGs) (ranked by importance) GasSourceResidency in air Water Vapor Evaporation from surface, fut- ure impact poorly understood About 10 days Carbon Dioxide Fossil fuel consumption, deforestation years MethaneAg byproduct; fossil fuel extraction 12 years OzoneCar combustion; it is part of photochemical smog Hours/days Nitrous Oxide Decay of fertilizers; car exhaust 114 years CFC’sAerosol sprays pre-1990sUp to 3,000 yr

Increasing GHG Concentrations N 2 O Methane

Earth with Greenhouse Gases With Greenhouse gases (CO 2 and H 2 O vapor) the planet’s average temperature fluctuates around +59ºF. This is 60ºF warmer than with no greenhouse gases 40F° is contributed by H 2 O vapor, 20F° by CO 2 Our societal debate is whether the observed increases in GHGs will increase the air temperature beyond 59°F, to 60°F, 61°F, etc. Carina Van Vliet

Aerosols & Sulfate Aerosols: Tiny particles & liquid droplets from burning of fossil fuels that also have radiative effects in our atmosphere. Sulfates are aerosols from coal & oil burning; they backscatter solar radiation & cool the climate. “Global dimming”.

Attribution of Climate Change to Human Activities Modeled climate change (shaded gray) is close to observed variability (black line). The climate change is the sum of the “forcings” shown at bottom, producing a net warming. Natural forcings neutral. Modeled climate: DOE parallel climate model Meehl et al (2004; J. Climate)

Annual Air Temperature Trends Rogers, 2010; J. Climate (submitted)

Plants, Crops, & Climate Change 1990 USDA plant hardiness zones (based on data) 2006 Nat’l Arbor Day Foundation (based on weather service data )

The U.S. Climate Change Science Program (6/19/08) “… biggest impacts of global warming will come in the form of changes in weather and climate extremes.” More heat waves Drought more frequent & severe in some regions Precipitation will be less frequent but more intense, high rainfall events more common.

Trends in Heavy Precipitation Periods, Heavy precipitation events have already increased. Consistent with increases in atmospheric water vapor associated with human-caused greenhouse gas increases. Precipitation has become less frequent but more intense. (Kunkel, Andsager and Easterling, 1999)

One Inch Rain Days per Year: Ohio Dayton: 6 days Columbus: 4.5 days Cleveland: under 4 days 2000’s Dayton: Over 9 days Columbus: ~ 8 days Cleveland: ~ 7 days

Alternating rainfall extremes Consequences: flooding, property damage, increased fertilizer runoff. Old community water/sewer systems may not be able to handle high rain events. Consequences: Prolonged dry periods & drought; low soil moisture; reduced lake/stream levels, reduced community water storage; water conflicts.

Great Lakes Hydrologic Cycle Water input from precipitation (tan arrows) and flow from the basin streams (green) and upstream lakes (purple), plus ground water. Air temperature (& wind) controls Evaporation (red arrows) that removes water; as does flow out to other Lakes and to the Atlantic (purple). EPA:

Changes in Great Lakes’ Levels Will be driven by temperature, and therefore evaporation, increases. In all models, precipitation changes little, within ± 10%.

A basin-wide Lake-effect snowfall event illustrating where the lake effect clouds and precipitation typically occur.

Current Lake-effect snowfall Reductions in Lake-effect snowfall Warmer winters = less lake-effect snow Southern Lakes: snows become rain more often. Northern Lakes: Less ice but still cold, lake effect snow still common. Study conducted by Kunkel, Westcott, Kristovich; Illinois State Water Survey HadCM2 model

Summary Earth already has a substantial greenhouse environment, keeping the planet warmer than it should be. Current temperature increases appear to be the result of warming by GHGs and cooling by sulfates. Expectations for the future emphasize increased number of extreme events. Large variations in precipitation. – More frequent high rain events, flooding & infrastructure strain – Longer dry spells in between, drought, agricultural problems Future Great Lakes’ levels may succumb to increased evaporation.

Thank You!

References Kunkel, K.E., K. Andsager, and D.R. Easterling, 1999: Long-term trends in extreme precipitation events over the con-terminous United States and Canada. J. Climate, 12, Meehl, G.A., W.M. Washington, C.A. Ammann, J.M. Arblaster, T.M.L. Wigleym and C. Tebaldi (2004). "Combinations of Natural and Anthropogenic Forcings in Twentieth-Century Climate". Journal of Climate 17: Wikipedia: global dimming Rogers, J.C., 2010: The 20 th century cooling trend over the southeastern U.S. Submitted to J. Climate.