Overview of the Climate System Raymond Najjar Penn

Overview of the Climate System Raymond Najjar Penn State Department of Meteorology • Definition of climate • Climate system components • Earth’s energy balance & the greenhouse effect • Water and carbon cycles • Internal variability vs. forced variability (ENSO example) • Natural forcings vs. human-induced forcings

Climate of a region: Statistical description of that region’s weather

Portlands Winter temperature probability distributions Portland, ME (43. 7°N) Portland, OR (45. 5°N) Source: NWS Climate Prediction Center

Factors affecting a region’s climate • • • Latitude Elevation Proximity to ocean Prevailing wind direction Atmospheric composition Land surface type

Visible image Minneapolis Source: Nese and Grenci (2010) Infrared image Minneapolis

Source: CLIVAR Program

Source: Wallace and Hobbs (2006). Based on Earth Radiation Budget Experiment (ERBE), 1985 -1986

Source: Wallace and Hobbs (2006). Based on Earth Radiation Budget Experiment (ERBE), 1985 -1986

Source: Wallace and Hobbs (2006). Based on Earth Radiation Budget Experiment (ERBE), 1985 -1986

Average = 30 W m-2 (warming) Shortwave forcing average = 50 W m-2 (cooling) Net effect: clouds cool 20 W m-2 Source: National Research Council (2008)

Global energy balance Source: Kiehl & Trenberth (1997)

IR radiative forcing of the climate IR radiation leaving the surface that is absorbed in atmosphere = 390 W m-2 – 235 W m-2 = 155 W m-2 Cloud IR forcing = 30 W m-2 Greenhouse gas forcing = 125 W m-2

Absorptivity of gases in the atmosphere 6% 8% Increasing due to human activity 26% 60% solar radiation terrestrial radiation Sources: Nese & Grenci (2010), Kiehl & Trenberth (1997) Dominant greenhouse gas Contribution to GHG forcing

Calculation of surface temperature without greenhouse forcing Energy in = Energy out Incoming solar = reflected solar + outgoing IR 1366 W m-2 = (0. 30)(1366 W m-2) + 4 s. T 4 T = 254 K = -19° C = 2° F Greenhouse effect warms surface ~60° F

The global water cycle Source: Trenberth et al. (2007)

The global carbon cycle Black = preindustrial, Red = 1990 s change Denman et al. (2007)

CO 2 role in greenhouse effect • ~ 25% of clear-sky greenhouse effect • ~ 20% of total greenhouse effect • ~ 0. 06% of the mass of the atmosphere

Forced vs. internal variability of climate • Forced: due to “external” processes; e. g. solar, volcanic, & humans • Internal: unforced variability; e. g. ENSO, NAO, PDO, AMO, etc.

Current conditions in the Tropical Pacific Source: www. pmel. noaa. gov/tao

Temperature section in the Equatorial Pacific Source: www. pmel. noaa. gov/tao

Source: www. pmel. noaa. gov/tao

Source: Nese and Grenci (2010)

ENSO variability over the past 60 years MEI computed from surface winds, surface air and water temperature, and cloud fraction Source: www. esrl. noaa. gov/psd/enso/mei/

Natural vs. Human-induced forcing of climate • Natural: solar, earth-orbital, volcanic • Human-induced: land use change, greenhouse gases, aerosols, soot

Discussion

References Denman, K. L. , Brasseur, G. , Chidthaisong, A. , Ciais, P. , Cox, P. M. , Dickinson, R. E. , Hauglustaine, D. , Heinze, C. , Holland, E. , Jacob, D. , Lohmann, U. , Ramachandran, S. , da Silva Dia, P. L. , Wofsy, S. C. , Zhang, X. , 2007. Couplings between changes in the climate system and biogeochemistry. In: S. Solomon, D. Qin, M. Manning, Z. Chen, M. Marquis, K. B. Averyt, T. Tignor, H. L. Miller (Editors), Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. Kiehl, J. T. , Trenberth, K. E. , 1997. Earth's annual global mean energy budget. Bulletin of the American Meteorological Society 78, 197 -208. National Research Council Committee on Scientific Accomplishments of Earth Observations from Space, 2008. Earth Observations from Space: The First 50 Years of Scientific Achievements. The National Academies Press, Washington, D. C. , 142 pp. Nese, J. M. , Grenci, L. M. , 2010. A World of Weather: Fundamentals of Meteorology, Fifth Edition. Kendall Hunt Publishing Company, Dubuque, Iowa, 794 pp. Trenberth, K. E. , Smith, L. , Qian, T. , Dai, A. , Fasullo, J. , 2007. Estimates of the Global Water Budget and Its Annual Cycle Using Observational and Model Data. Journal of Hydrometeorology 8, 758 -769. Wallace, J. M. , Hobbs, P. V. , 2006. Atmospheric Science: An Introductory Survey, Second Edition. Elsevier, Inc. , Oxford, UK, 483 pp.

Extra slides

CO 2 emissions from human activity (black) compared with the rate of increase in atmospheric CO 2 (blue) Source: Global Carbon Project, www. globalcarbonproject. org/carbonbudget

Source: Global Carbon Project