Chapter One: Greenhouse gases and their effect

HNR 330Dr. Hengchun Ye

Climate LiteracyUSGCRP: U.S. Global Climate Research Program. Established in 1989, coordinates

and integrates the climate change activities of 12 federal departments and agencies.

Seven Principles:1. The sun is the primary source of energy for the earth’ s climate system2. Climate is regulated by complex interactions among components of the

earth’s system3. Life on earth depends on, is shaped by, and affects climate4. Climate varies over space and time through both natural and human-made

processes5. Other understanding of the climate system is improved through observations,

theoretical studies, and modeling6. Human activities are affecting the climate system7. Climate change will have consequences for the earth system and human lives

Four Spheres of the Earth’s System

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 extremesShared 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. TroposphereSurface to 18 km (11 mi)90% mass of atmosphereLapse rate: the rate of air temperature decreases with elevationNormal lapse rate – average cooling at rate of 6.4 C°/km (3.5 F°/1000 ft)

2. Stratosphere18 to 50 km (11 to 31 mi)Inversion: air temperature increases with elevationOzone maximum

3. Mesosphere50 to 80 km (30 to 50 mi)4. ThermosphereRoughly same as heterosphere80 km (50 mi) outward

Atmosphere Global Circulation Pattern

Causes: 1. hot air rises and cold air

sinks2. Pressure gradients:

changes in air pressure over a horizontal distance

3. 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 SystemsSurface 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

Albedo distribution

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 EffectThe 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:1. A coal liquefaction in south Africa-a largest single source of CO2 on the earth2. 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 radiationO3 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%

AerosolsFine solid particles or liquid droplets suspended in the atmosphere

Scatter or absorb sunlightSO4 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:

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 CO2N2O absorbs 270 times more; CFCs is 30,000 times more than CO2.

Positive: increases air temperatureNegative: decreases air temperature

Human behavior related to radiative forcing

Mitigating Global warming requires managing carbon

Carbon in the atmosphere, in the water, and in the crust

Carbon stored in the crust:1. Limestone (CaCO3)2. 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