Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Snowball Earth wikipedia , lookup
Climate engineering wikipedia , lookup
Mitigation of global warming in Australia wikipedia , lookup
Attribution of recent climate change wikipedia , lookup
IPCC Fourth Assessment Report wikipedia , lookup
Global warming wikipedia , lookup
Hemispherical photography wikipedia , lookup
Instrumental temperature record wikipedia , lookup
UCSD COSMOS 2012: Living Oceans and Climate Change Prof. Lynn Russell (lead instructor) Dr. Ngai Chin Lai (co-instructor) Prof. Joel Norris (co-instructor) Ms. Megan Jones (teacher fellow) Ms. Amanda Frossard (cluster assistant) Mr. Khalid Azizi (cluster assistant) Course websites http://aerosols.ucsd.edu/cosmos.html http://meteora.ucsd.edu/~jnorris/cosmos/cosmos.html PowerPoint lectures and other materials will be made available on the course websites Albedo, Greenhouse Effect, and Global Warming Unless otherwise noted, figures and illustrations come from the Fourth Report (AR4) by the Intergovernmental Panel on Climate Change (IPCC). Visible light, infrared (IR), ultraviolet (UV), X-rays, γ-rays, microwaves, and radio are all forms of electromagnetic radiation Sun Each type has a different wavelength (λ). Earth The shorter the wavelength, the greater the energy of individual photons Shortest to longest wavelength: γ-rays, X-rays, UV, visible, IR, microwave, radio Does infrared radiation easily go through glass? Earth’s Energy Budget • Earth absorbs visible and near IR radiation from the Sun • Earth emits thermal infrared radiation back to space • Certain constituents reduce emission to space Sun Earth Start CO2 in jar Solar Radiation • Solar radiation flux at the average distance of Earth’s orbit (S0) is about 1367 W m-2 (This is equivalent to ?? 60W light bulbs every square meter) • This solar radiation intersects with πR2 area, where R is the radius of the Earth Solar Radiation • The total energy rate for solar radiation intersecting Earth is S0 πR2 • The global surface area of Earth is 4πR2 • What is the average amount of solar radiation per m2 spread out over the Earth? (S0 = 1367 W m-2) Solar Radiation • Global average solar radiation flux at the top of the atmosphere: S0 / 4 = 342 W m-2 (This is equivalent to ?? 60W light bulbs every square meter) • How much is directly reflected back? • How much is absorbed by the Earth and atmosphere? • What happens to absorbed radiation? • In equilibrium, how much radiation is emitted by the Earth? What happens to visible light when it arrives at the Earth? How does heat leave the surface of the Earth? Look outside. Jars go outside. Planetary Albedo • Planetary albedo αp is the global average fraction of solar radiation reflected back to space. • Earth’s planetary albedo is 0.31 • The global average value of reflected solar flux is αp S0 / 4 = 107 W m-2 • The global average value of absorbed solar flux is (1 – αp) S0 / 4 = 235 W m-2 Various Albedo Values • • • • • Ocean albedo is about 0.1 (except for sunglint) Sandy desert albedo is about 0.25-0.35 Forest albedo is about 0.15 Snow/ice albedo is about 0.6-0.9 Cloud albedo is about 0.3-0.6 Greenhouse Effect • The reduction in the amount of energy leaving the Earth caused by clouds and greenhouse gases acts like a blanket to keep the Earth warmer • Clouds and greenhouse gases also emit IR radiation toward the surface (324 W m-2) • The surface absorbs this additional radiation and thus is kept warmer Greenhouse Effect • The strongest greenhouse gas is water vapor • The next strongest greenhouse gas is CO2 • Clouds (composed of liquid water droplets and ice crystals) have a greenhouse effect and an albedo effect • High clouds have the strongest greenhouse effect because they are coldest Check jars Earth’s Radiation Budget • What will happen if absorbed solar radiation is out of balance with emitted thermal radiation? • What can cause imbalances? Importance of Albedo • All else held the same, a doubling of CO2 in the atmosphere (280 ppm 560 ppm) will reduce outgoing IR by about 4 W m-2 • This is roughly equivalent to the change in absorbed solar radiation caused by a 0.01 change in planetary albedo 0.01 x 342 W m-2 = 3.4 W m-2 • Small changes in albedo can have a big effect on climate human activity natural state measured global warming of Earth’s surface primarily caused by anthropogenic increase in greenhouse gases temperature variations estimated from tree rings and other proxy records measured temperature change Thermal Inertia • The change in temperature caused by radiative imbalance does not occur instantaneously due to thermal inertia • It takes decades to centuries for the ocean to warm up or cool down • We have not yet experienced the full warming that will be produced by the CO2 we have already put into the atmosphere Positive Feedbacks • Two processes will very likely increase the warming initially produced by additional CO2 Ice Albedo Feedback • Warmer temperature will cause ice sheets and snow to melt back • The surface will become darker and absorb more solar radiation • This will cause temperature to increase even more Water Vapor Feedback • Warmer temperature will cause more water to evaporate and enter the atmosphere • More water vapor in the atmosphere will reduce the amount of IR radiation emitted to space • This will cause temperature to increase even more Check jars Describe Jar Experiment