240 likes | 433 Views
Chapter One: Greenhouse gases and their effect. HNR 330 Dr. Hengchun Ye. Climate Literacy. USGCRP: U.S. Global Climate Research Program. Established in 1989, coordinates and integrates the climate change activities of 12 federal departments and agencies. Seven Principles:
E N D
Chapter One: Greenhouse gases and their effect HNR 330 Dr. Hengchun Ye
Climate Literacy USGCRP: U.S. Global Climate Research Program. Established in 1989, coordinates and integrates the climate change activities of 12 federal departments and agencies. Seven Principles: • The sun is the primary source of energy for the earth’ s climate system • Climate is regulated by complex interactions among components of the earth’s system • Life on earth depends on, is shaped by, and affects climate • Climate varies over space and time through both natural and human-made processes • Other understanding of the climate system is improved through observations, theoretical studies, and modeling • Human activities are affecting the climate system • Climate change will have consequences for the earth system and human lives
Weather and Climate • Weather: is a short term status of the atmosphere at a given time. • Climate: is a long term average weather pattern in a particular region and its extremes Shared Variables: Temperature, precipitation, humidity, sunshine, cloud types and cover, wind speed and direction, visibility, etc. To understand the climate is to understand the “HEAT”-energy balance In order to have a equilibrium condition and keep the air temperature constant, all components of energy summed up together=0 NASA scientist James E. Hanson discovered the earth’s energy was no longer balanced, Global warming issue came to the light.
Atmospheric structure-based on temperature profiles • 1. Troposphere • Surface to 18 km (11 mi) • 90% mass of atmosphere • Lapse rate: the rate of air temperature decreases with elevation • Normal lapse rate – average cooling at rate of 6.4 C°/km (3.5 F°/1000 ft) • 2. Stratosphere • 18 to 50 km (11 to 31 mi) • Inversion: air temperature increases with elevation • Ozone maximum • 3. Mesosphere • 50 to 80 km (30 to 50 mi) • 4. Thermosphere • Roughly same as heterosphere • 80 km (50 mi) outward
Atmosphere Global Circulation Pattern Causes: hot air rises and cold air sinks Pressure gradients: changes in air pressure over a horizontal distance Coriolis effect Isobars: lines of equal air pressure
Coriolis Force: an apparent force caused by the rotation of the earth;1) deflects to the right (of the movement) in northern hemisphere.2) Maximum in the poles and zero in the equater3) Proportional to the wind speed.
Global Circulation Systems Surface pressure system: 1. Inter-tropical convergence zone-ITCZ (equator) 2. Polar High Pressure (poles) 3. Subtropical high pressure (30N/S) 4. Subpolar low-pressure cells (60N/S) Wind Patterns: 1. Northeast trade wind (between equator and 30N/S) 2. Westerlies (between 30N/S-60N/S) 3. Polar northeasterly (between 60N/S-poles
Hadley Cell: rises from equator subsides over Subtropical High • Polar Cell: rises at 60 latitudes and subsides over Poles • Ferrel Cell: rises at 60 latitude and subsides at 30 latitudes Rises at low pressure and subsides at high pressure
Ocean Circulation (Fig 1.4) Surface Current: 5 major gyres North Pacific, south Pacific, North Atlantic, south Atlantic, Indian Ocean Caused by the surface wind and Coriolis effect Warming of the surface temperature of the ocean is 0.6°C during past 100 years
Earth’s Energy Budget Albedo: the percentage of solar radiation reflected by a surface Half of the solar radiation energy is absorbed by the earth’s surface Earth gives off energy to atmosphere by longwave radiation, conduction/convection (sensible heat), and latent heat. Latent heat: energy transfer through water phase change
Greenhouse gases: Carbon Dioxide (CO2), Water Vapor (H2O), Methane (CH4), Ozone (O3), Nitrous Oxide (N2O), Chlorofluorocarbons (CFCs). They consists of less than 1% of total atmosphere. The current average earth’s air temperature is 14C (57.2c). Without greenhouse gases, the temperature would be -18C (0°F). Venus atmosphere is 98% CO2, the surface temperature is 858°F.
Greenhouse Effect The longwave radiation emitted by the earth is absorbed by greenhouse gases and re-emitted back to the earth’s surface to keep atmosphere warm. More greenhouse gases in the atmosphere, more heat accumulates near the earth’s surface
Atmospheric composition: N2 (78%), O2 (21%), Ar (0.96%), CO2 (0.04%), etc. History of CO2 content measured in ice cores (Fig 1.10) ppb: parts per million. They are measured using fossil air trapped in ice in Antarctic.
Remote sensing observation of CO2 (Fig 1.11) Sources: burning fossil fuel, solid waste, deforestation, industrial agricultural, cement production The Atmospheric Infrared Sounder (AIRS) is able to pinpoint the influence of specific carbon dioxide sources. Large amount in 40-50°S: A coal liquefaction in south Africa-a largest single source of CO2 on the earth A Cluster of power generating plants in eastern Austria
Modern greenhouse gas records (Fig 1.12) CO2 measure at Mauna Loa Observatory in Hawaii; has season oscillations. Methane: (decreased in 1990s due to former Soviet Union collapse and drought) Natural: wetland, seawater, soil; ocean sediments; permafrost thawing. Anthropogenic (60%): deforestation, mining and burning fossil fuels, processing human waste, cultivating rice paddies, manure production, landfill emissions, cattle farms CFCs have declined since the Montreal Protocol in 1987
Climate feedbacks • Positive feedback: amplified effect. Example: climate warms, more permafrost thaw, further increase CH4 emission, climate warms further, etc. • Negative feedback: suppressed effect. Ozone: good in stratosphere; bad in troposphere. O3 in stratosphere block UV radiation O3 in troposphere create smog, a type of air pollution. Sources: indirect production of emission of CO, N2O, SO2, and hydrocarbons from burning biomass and fossil fuels. (last a few weeks to month) N2O Natural source: activity of microbes in swamps, soil, rainforests, and ocean surface, thawing permafrost. Anthropogenic: fertilizer, industrial production of nylon and nitric acid, burning of fossil fuels, and solid waste. CFCS: unnatural gas produced by industrial processes including air conditioning, aerosol sprays, manufacture of plastics and polystyrene. Very stable and long life time (75-150 years).
Ozone Hole: CFCs react with and destroy O3 in stratosphere (Fig 1.14) • Montreal Protocol on 1987 signed by 27 nations; United states ceased production of CFCS in 1995. • Ozone hole show signs of recover over the Antarctic. Dobson unit: one Dobson unit is the number of O3 molecules that would be required to create a layer of pure ozone 0.01mm thick at a temperature of 0C and a pressure of 1 atmosphere (air temperature at the sea level)
Water vapor 2% of atmosphere. Hydrological cycle: consists of five major processes of condensation, precipitation, infiltration, run off, and evapotranspiration (evaporation plus transpiration). Human has no direct impact except for local scale: irrigation, reservoir building, changes in surface features, etc. Increasing air temperature has a positive feedback in water vapor (6%-7.5% per degree of C). Could potential double the increases in air temperature caused by CO2 alone If the world warms 2-3C, the water cycle could accelerate 16-24%
Aerosols Fine solid particles or liquid droplets suspended in the atmosphere Scatter or absorb sunlight SO4 from burning coal, woods, dung, and petroleum. 1950s-1970s industrial growth, caused cooling of global temperature. Volcanic eruption: Mount Pinatubo in Philippines erupted in June 1991, cooled the planet early 1C, offsetting the greenhouse effect for more than one year. NASA’s Terra Satellite Black soot: burning fuels made of biomass (wood, coal, animal dung, diesel, vegetable oil etc). Causes warming in high latitude regions where snow and ice present
Radiative forcing: Positive: increases air temperature Negative: decreases air temperature Radiative Balance: incoming solar radiation=outgoing earth radiation; Despite low solar activity between 2005-2010, earth continued to absorb more energy than it returned to space as heat. Methane absorbs 21 times more heat per molecule than CO2 N2O absorbs 270 times more; CFCs is 30,000 times more than CO2.
Mitigating Global warming requires managing carbon Carbon in the atmosphere, in the water, and in the crust Carbon stored in the crust: Limestone (CaCO3) Buried as organic matter Organic material in ecosystems, such as the simple carbohydrate glucose (C6H12O6), found in plants and animals. Sink: reduce carbon Source: produce carbon