Earth's Energy Balance 2023 PDF

Earth’s Energy Balance IR UV λmax Sun λmax Earth visible light IN (100 - 30) = OUT (70) Planetary energy budget is out of balance. Earth is absorbing more energy from the Sun than it is radiating back to space due to the increasing greenhouse gas concentrations. The imbalance is ~ 0.6...

Earth’s Energy Balance IR UV λmax Sun λmax Earth visible light IN (100 - 30) = OUT (70) Planetary energy budget is out of balance. Earth is absorbing more energy from the Sun than it is radiating back to space due to the increasing greenhouse gas concentrations. The imbalance is ~ 0.6 W m-2 Source: Intergovernmental Panel on Climate Change (IPCC, AR5) 2013 The imbalance is ~ 0.6 W m-2 0.79 W m-2 Source: Intergovernmental Panel on Climate Change (IPCC, AR5) 2013 2021 1) Water vapour feedback 2) Ice-albedo feedback 3) IR flux-temperature feedback 4) Cloud feedback 1) Water vapour feedback 2) Ice-albedo feedback 3) IR flux-temperature feedback 4) Cloud feedback Your task : Draw a systems diagram for the first three on the list J increase in temperature -> -> increase in water vapour -> increase in greenhouse effect -> further increase in temperature increase in temperature -> -> increase in water vapour -> increase in greenhouse effect -> further increase in temperature http://svs.gsfc.nasa.gov/vis/a010000/a010000/a010021/index.html http://svs.gsfc.nasa.gov/vis/a010000/a010000/a010021/index.html F = σ T4 F = σ T4 high albedo -> reflect incoming solar radiation high water content -> absorb outgoing IR radiation low thick warm clouds generally cause cooling high thin cold clouds generally cause warming http://www.windows.ucar.edu/earth/Atmosphere/images/cirrus6_small.jpg http://www.windows.ucar.edu/earth/Atmosphere/images/stratocumulus3_big.jpg Cloud Feedback http://www.theresilientearth.com/files/images/cloud_chart.gif Cloud Feedback...appears to be positive http://www.theresilientearth.com/files/images/cloud_chart.gif 1) Water vapour feedback 2) Ice-albedo feedback 3) IR flux-temperature feedback 4) Cloud feedback 1) Water vapour feedback - positive 2) Ice-albedo feedback - positive 3) IR flux-temperature feedback - negative 4) Cloud feedback - likely positive 1) Water vapour feedback - positive 2) Ice-albedo feedback - positive 3) IR flux-temperature feedback - negative 4) Cloud feedback - likely positive ¡ The current global mean energy budget is out of balance by roughly 0.79 W m-2 due to greenhouse gas forcing. ¡ Ts has risen 1°C over the past century as a result and will likely rise another 0.6 °C in response to the presently existing imbalance. ¡ As Ts rises, so does the outgoing IR flux radiated by the Earth. This negative feedback is operating now. ¡ As long as greenhouse gas concentrations continue to rise, the amount of solar energy absorbed will continue to exceed the thermal IR flux that escapes to space. Summary The habitability of Earth is due: § Earth’s distance from the sun § Earth’s albedo § Greenhouse gases in our atmosphere The 3 factors above allow for the existence of water in its three phases Major events involve perturbations in the carbon and water cycles on Earth. ¡ Carbon dioxide and water vapour are minor constituents of the atmosphere, but they are major greenhouse gasses. ¡ Water, CO2 and other greenhouse gases absorb IR energy by increasing their rotation- or vibration- frequencies. ¡ Both CO2 and water absorb strongly at a wavelengths emitted by the Earth’s surface. ¡ Heating of the atmosphere by the Earth’s surface causes convection. ¡ Convection produces weather, including clouds. ¡ Clouds affect climate by changing planetary albedo and by absorbing and re-emitting IR radiation. ¡ There are some important feedbacks at work in the Earth system. ¡ END