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Component of the climate System and greenhouse effect Ladislaus Chang a Institute of Resource Assessment Tanzania Meteorological Agency Education Program on Climate Change and Biodiversity Conservation, Institute of Resource Assessment, University of Dar es Salaam, 19 July, 2010 - 3rd September 2010 OUTLINE 1. Weather and Climate 2. Components of the climate system 3. Characteristics of the climate system 4. The greenhouse effect Questions to think about • What is climate? • How is climate different from weather? • What controls the climate? • Which are greenhouse gases? • The role of greenhouse gas in climate change Weather vs. Climate • Weather variables: – Temperature – Pressure – Clouds – Dew point – Precipitation – Wind – Visibility • Weather describes current conditions • Climate describes longterm synthesis – Means – Extremes – Frequencies – Spatial patterns • Impacts are also assessed The Climate System • Global climate is: – Driven by solar radiation (Earth s external heat engine) – Composed of diverse, interrelated components that function as a whole Components of the Climate System Atmosphere Biosphere - Vegetation - Anthrosphere Lisosphere - land Cryosphere -ice Hydrosphere -ocean Climate System Fig. 1.1 Bigg The role of the climate system Atmosphere: Volatile turbulent fluid, strong winds, Chaotic weather, clouds, water vapor feedback Transports heat, moisture, materials etc. Heat capacity equivalent to 3.2 m of ocean Ocean: 70% of Earth, wet, fluid, high heat capacity Stores, moves heat, fresh water, gases, chemicals Adds delay of 10 to 100 years to response time Land: Small heat capacity, small mass involved (conduction) Water storage varies: affects sensible vs latent fluxes Wide variety of features, slopes, vegetation, soils Mixture of natural and managed Vital in carbon and water cycles, ecosystems Ice: Huge heat capacity, long time scales (conduction) High albedo: ice-albedo feedback Fresh water, changes sea level Antarctica 65 m (WAIS 4-6m), Greenland 7m, other glaciers 0.35m The role of the atmosphere in energy v The atmosphere is the most volatile component of climate system v Winds in jet streams exceed 100 mph or even 200 mph; winds move energy around. v Thin envelope around planet 90% within 10 miles of surface 1/400th of the radius of Earth; clouds appear to hug the surface from space. v The atmosphere does not have much heat capacity v Weather occurs in troposphere (lowest part) v Weather systems: cyclones, anticyclones, tropical storms/hurricanes move heat around: mostly upwards and polewards Role of Oceans v The oceans cover 70.8% of the Earth s surface. v The oceans are wet: water vapor from the surface provides source for rainfall and thus latent heat energy to the atmosphere. v The heat capacity of the atmosphere is equivalent to that of 3.5 m of ocean. The oceans slowly adjust to climate changes and can sequester heat for years. v The ocean is well mixed to about 20 m depth in summer and over 100 m in winter. An overall average of 90 m would delay climate response by 6 years. v Estimate of delay overall is 10 to 100 years. v The ocean currents redistribute heat, fresh water, and dissolved chemicals around the globe. Role of Land Ø Heat capacity of land is much less than water: Ø Specific heat of land 4½ less than sea water Ø Land plays lesser role than oceans in storing heat. Consequently: Ø Surface air temperature changes over land are large and occur much faster than over the oceans. Ø Land has enormous variety of features: topography, soils, vegetation, slopes, water capacity. Ø Changes in land and vegetation affect climate through albedo, roughness and evapotranspiration. The Role of Ice Major ice sheets, e.g., Antarctica and Greenland. Penetration of heat occurs primarily through conduction. Unlike land, ice melts ⇒ changes in sea level on longer time-scales. Ice volumes: 28,000,000 km3 water is in ice sheets, ice caps and glaciers. Most is in the Antarctic ice sheet which, if melted, would increase sea level by ∼65 m, vs Greenland 7 m and the other glaciers and ice caps 0.35 m. In Arctic: sea ice ~ 3-4 m thick Around Antarctic: ~ 1-2 m thick CLIMATE SYSTEM HYDROSPHERE ATMOSPHERE CRYOSPHERE L. VICTORIA BIOSPHERE Mt. Kilimanjaro КИЛИМАНДЖАРО (5895 М) LISOSPHERE 13 The Climate System Systems Approach • Systems – Comprised of diverse components that function as a whole • Climate System – Flow of energy and mass between components – Change in one component will affect other components – Linked (coupled) interactions Climate System • Example of coupling – – – – – – – – Increase seafloor spreading rate (volcanism) geosphere More CO2 to atmosphere atmosphere Warmer climate Melt ice cryosphere Raise sea level Alters ocean circulation hydrosphere Alters distribution of nutrients- productivity biosphere Impact on CO2…. atmosphere... Climate System • Interactions: – Complex • Each component works at a different rate • Feedbacks – Complicated • Nonlinear patterns of variation Components of the Climate System • Discuss each component in terms of: – Response time- how quickly it responds to inputs – Heat capacity- amount of energy that must be put into the component to cause a change – Albedo -reflectivity of incoming short wave radiation Biosphere - Vegetation - Anthrosphere Geosphere - land Hydrosphere -ocean Atmosphere Cryosphere -ice Atmosphere • Response time – Strong diurnal cycle – Fastest response to perturbation- days to months – Mixes globally in months to years • Heat Capacity – Low heat capacity – Easily heated and set into motion – Strong vertical and horizontal gradients Atmosphere • Albedo – Clouds reflect 50-55% – Clear skies reflect ~5% • Coupled to other systems through energy and chemical exchanges – Evaporation/precipitation – Wind stress – Trace gas exchange Hydrosphere • Heat Capacity – Very high – Stores heat and buffers the system against change • Albedo – Ocean surface ~8% Hydrosphere • Coupled to other components through exchange of energy and mass – Evaporation/precipitation – Trace gas exchange – Land/sea boundary defined by sea level – Drives chemical reactions (weathering) – Necessary for life (photosynthesis) Cryosphere- Ice • Cryosphere includes: continental ice sheets, mountain glaciers, ice shelves, sea ice, snow, permafrost • Currently 6% of Earth permanently covered by ice (highly variable) Cryosphere • Antarctic Ice Sheet (AAIS) – 60% of world s fresh water – Sea level would rise 73 m if AAIS melted (7.4 m sea level rise if Greenland melted) Cryosphere • Response time- multiple time scales – Rapid seasonal variations- annual meltback – Observed decadal changes – Ice sheet growth- 10,000 to 100,000 yrs – Ice sheet decay- 1,000 to 10,000 yrs • Heat Capacity – High- lots of energy required for phase transition (melting) Cryosphere • Albedo – Primary role in climate system = reflectivity – Highly reflective • Old snow ~50% • Fresh snow 80-90% Lisosphere Mt Pinatubo Erupted June 1991 Philippines Reduced mean global surface temperature by 0.5C for ~2 years Lisosphere • Albedo – – – – Dark soil ~10% Light soil ~30% Black top~5-10% Concrete ~20% • Major impacts on climate – Continentality – Topography (atm circulation) Biosphere • Can include people (anthropogenic effects) • Response time – Individuals – seasonal or annual – Communities- centuries Biosphere • Albedo – Forests ~5-10% – Meadows and crops ~5-25% – Rainforests- lowest albedo on Earth • Important contributions to climate – Evapotranspiration rates – Atmospheric composition – Albedo (forest ~10%; soil ~25%) Properties of a System • Feedback loops – A particular type of interaction between components of a system – A change in Component 1 elicits a change in Component 2, which in turn comes back to affect Component 1 Requires a disturbance/perturbation to initiate the change Feedback Loops • Positive Feedback Loop – Interactions amplify the effects of the disturbance • Negative feedback loop – Interactions diminish the effects of the disturbance Positive Feedback Loop (amplifies) • Temperature decreases • Ice grows • Albedo increases • Temperature decreases • More ice grows… Negative Feedback Loop (diminishes) • Temperature increases • Increased evaporation • Increased cloud cover Negative Feedback Loop (diminishes) • Temperature increases • Increased evaporation • Increased cloud cover • Albedo increases • Temperature decreases • Less evaporation • Fewer clouds Climate Change Change – Compare climate state at one time to some time in the past or the future – Requires record of past climate or predictions of future climate Climate Variability • Periodic (seasons, annual) • Quasiperiodic (El Niño) • Chaotic GREENHOUSE EFFECT & OZONE DEPLETION The GREENHOUSE EFFECT, like a real greenhouse (below) is to allow heat in, but not out. Gases in the atmosphere (CO2, Methane) naturally trap outgoing LW radiation more effectively than they do incoming SW radiation. This retains heat, warming the earth’s atmosphere. This has, over geological time, been in balance. Now, human activity is increasing such gases so the warming effect is (possibly) beyond recall. This is the modern The Earth would be -19°C (-2°F) without atmosphere. 99% of the atmosphere is nitrogen and oxygen which are transparent to radiation The Natural Greenhouse Effect: clear sky O3 8% Carbon Dioxide 26% CH4 N20 6% Water Vapor 60% Clouds also have a greenhouse effect Kiehl and Trenberth 1997 Greenhouse Gases • Carbon dioxide – fossil fuel combustion. • Methane – fossil fuel production, decomposition of organic wastes. • Nitrous oxide - agricultural and industrial activities, as well as during combustion of solid waste and fossil fuels. Greenhouse Gases • Greenhouse gases are emitted by human activities. Do you know ? Without green house effect, the global average temperature on earth would be -18°C, whereas at the moment it is +15°C. Definitions of 'greenhouse effect' • warming that results when solar radiation is trapped by the atmosphere: caused by atmospheric gases that allow sunshine to pass through but absorb heat that is radiated back from the warmed surface of the earth • FACT:- If the greenhouse effect did not exist at all the earth would be a frozen lifeless planet. • FACT:- Carbon dioxide is responsible for about 50% of the Greenhouse Effect. • These gasses are known as greenhouse gasses, and the main ones are Carbon dioxide Methane and Chlorofluorocarbons better known as CFC's. Gases involved in the Greenhouse Effect: past and present concentration and sources. Greenhouse Gas Concentration Concentration 1750 2003 Carbon Dioxide 280 ppm 376 ppm Methane 0.71 ppm 1.79 ppm 270 ppb 319 ppb 0 880 ppt Nitrous Oxide Chlorofluorocarbons (CFCs) Natural and Anthropogenic Sources Organic decay; Forest fires; Volcanoes; Burning fossil 34% fuels; Deforestation; Land-use change Wetlands; Organic decay; Termites; Natural gas & oil extraction; 152% Biomass burning; Rice cultivation; Cattle; Refuse landfills Forests; Grasslands; Oceans; Soils; Soil cultivation; 18% Fertilizers; Biomass burning; Burning of fossil fuels Refrigerators; Aerosol spray Not propellants; Applicable Cleaning solvents Percent Change Questions for group discussion 1. Which component of the climate system is more affected by climate change? 2. Discuss the linkage between the components of the climate system and from African perspective identify the component that is more affected by human activities? 3. Discuss the relationship between climate variability and climate change. Identify a country or region in Africa where rainfall is increasing and temperature is decreasing and explain the reason 4. Discuss the Greenhouse effect and identify the major sources of Carbon dioxide and Methane in Africa Thank You