ESS 111 – Climate & Global Change Lecture 3 Greenhouse Effect El Nino – Southern Oscillation

What is the Greenhouse Effect?

Review of Energy – What is energy? – 3 methods of energy transfer? – Conduction – Convection – Radiation – phy.org/energy/domestic/heat_phy/flash/heat_transfer_e.html – Insolation (Incoming Solar Radiation) = shortwave radiation – Heat energy emitted by the Earth (ground) = longwave radiation

Earth’s energy budget Yellow: shortwave Red: longwave

Satellite Measurements of the Earth’s Radiation Budget NASA ’ s Earth Radiation Budget Satellite (ERBS)

Earth’s energy budget (averaged over the whole globe & a long time At the top of the atmosphere: Incoming shortwave = Reflected Shortwave + Emitted longwave At the surface: Incoming shortwave = Reflected shortwave + Net emitted longwave (emitted - incoming) + Latent heat flux + sensible heat flux Sensible heat 7% Latent heat 23% Net Longwave 21% Yellow: shortwave Red: longwave

Atmospheric influences on radiationReflectionScattering Absorption (absorber warms)

Atmospheric Absorption - The Greenhouse Effect Transparent to solar (shortwave) radiation Opaque to earth’s (longwave) radiation Major GH gases: CO 2, H 2 0 (v), CH 4

Impact of the Greenhouse Effect The Goldilocks Principle can be summed up neatly as "Venus is too hot, Mars is too cold, and Earth is just right." The fact that Earth has an average surface temperature comfortably between the boiling point and freezing point of water, and thus is suitable for our sort of life, cannot be explained by simply suggesting that our planet orbits at just the right distance from the sun to absorb just the right amount of solar radiation. Our moderate temperatures are also the result of having just the right kind of atmosphere. A Venus-type atmosphere would produce hellish, Venus- like conditions on our planet; a Mars atmosphere would leave us shivering in a Martian-type deep freeze.

Greenhouse Gases Water Vapor is by far the most abundant GHG. Methane (CH 4 ) 23 times more powerful as a greenhouse gas than CO 2 The livestock sector is a major player, which accounts for % global anthropogenic emissions of methane (their burps!)

3 Types of Scattering: 1. Raleigh 2. Mie 3. Non-Selective Atmospheric Scattering A discussion of each type follows…

involves gases smaller than insolation wavelength scatters light in all directions most effective at short wavelengths (violet, blue)… hence, blue sky Rayleigh Scattering The Earth has an atmosphere. So it has Rayleigh scattering and its sky appears blue The Moon has no atmosphere. So it has no Rayleigh scattering and its sky appears dark

Rayleigh scattering also explains reddish-orange sunsets when light travels through thick slice of atmosphere

Monet: Impressions, Sunrise

2) Mie scattering involves aerosols (e.g. dust, smoke) larger than gas molecules forward scatter equally effective across visible spectrum explains hazy, gray days

3) Non-selective scattering Happens when atmospheric particles are much larger than the wavelength of incoming radiation (e.g. water droplets in clouds) Act like lenses; scatter all wavelengths equally to create a white appearance That ’ s why clouds appear white

Summary: Earth’s energy budget At the top of the atmosphere: Incoming shortwave = Reflected Shortwave + Emitted longwave At the surface: Incoming shortwave = Reflected shortwave + Net emitted longwave (emitted - incoming) + Latent heat flux + sensible heat flux Sensible heat 7% Latent heat 23% Net Longwave 21% Yellow: shortwave Red: longwave

What Are the El Nino and La Nina?

The Walker Circulation Mean ascent (rising air), and low surface pressure, over warmest SST associated with deep convection (T-storms) Subsidence (sinking air), and high surface pressure, in non-convection regions (clear skies) Equatorial trades blow from high to low pressure, thus the easterly trade winds blow from east to west Low slp High slp

El Nino During El Nino trade winds slacken  E-W tilt of thermocline & upwelling of cold water are reduced.  SST rises in central/eastern equatorial Pacific  Changes Walker Circulation

Tropical mean state: Sea surface temperature (SST) Indo-Pacific warm pool Eastern Pacific cold tongue 2 basic regions

Ocean Upwelling is an oceanographic phenomenon that involves wind-driven motion of dense, cooler, and usually nutrient-rich water towards the ocean surface, replacing the warmer, usually nutrient-depleted surface water. Ocean upwelling & the Thermocline The thermocline is the transition layer between the mixed layer at the surface and the deep water layer. The definitions of these layers are based on temperature. The mixed layer is near the surface where the temperature is roughly that of surface water. In the thermocline, the temperature decreases rapidly from the mixed layer temperature to the much colder deep water temperature. The mixed layer and the deep water layer are relatively uniform in temperature, while the thermocline represents the transition zone between the two.

Thermocline and wind patterns during the normal Walker Circulation. Cooler, nutrient rich water moves upward from below along the South American coast. Thermocline, Upwelling, & El Nino Thermocline and wind patterns during the normal El Nino – Southern Oscillation conditions Cooler, nutrient rich water does not “upwell” to the ocean surface. Warm surface water piles up along the South American Coast.

Mean climate El Ni ñ o ’82/83 El Nino

SST anomalies during El Nino Dec 1982 Sept 1987

ENSO Comparison Animations =9rPqIuXlWuA =whsQbIwWjBo

The 1997/98 El Nino Jan 1997 Trade Winds

The 1997/98 El Nino Nov 1997Jun 1997 Trade Winds

The 1997/98 El Nino Nov 1997 Trade Winds

The 1997/98 El Nino Mar 1998 Trade Winds

The 1997/98 El Nino Mar 1998Jan 1997

The 1997/98 El Nino Jun 1997

The 1997/98 El Nino Nov 1997

The 1997/98 El Nino Mar 1998

What about La Nina? Dec 1982 Nov 1988 La Nina conditions sometimes occur in the year following an El Nino event (e.g followed 1987 El Nino) In La Nina conditions SST in the central and eastern equatorial Pacific is unusually cold & easterly trade winds are unusually strong

Typical ENSO period is 3-7 years, but with significant irregularity

The dramatic impacts of ENSO around the globe Flood in Lakeport, California as a result of the 1998 El Nino event Bushfire in Australia as a result of the 1998 El Nino event

The dramatic impacts of ENSO around the globe Flood in Lakeport, California as a result of the 1998 El Nino event Bushfire in Australia as a result of the 1998 El Nino event

Disastrous effects of El Nino: 1.Australia-Drought and devastating brush fires 2.Indonesia, Philippines-Crops fail, starvation follows 3.India, Sri Lanka-Drought,fresh water shortages 4.Tahiti-6 tropical cyclones 5.South America-Fish industry devastated - decrease in nutrients off Peru- fewer fish (anchovy) 6.Across the Pacific-Coral reefs die 7.Colorado River basin-Flooding, mud slides 8.Gulf states-Downpours cause death, property damage 9.Peru, Ecuador-Floods, landslides 10.Southern Africa-Drought, disease, malnutrition

A seasonal reversal of wind due to seasonal thermal differences between landmasses and large water bodies Orographic lifting often enhances precipitation totals The Seasonal “Monsoon”