Overview of the Past and Present Earth System Observations of the Earth OSHR 1609 Climate 101 September 20, 2013 Scott Denning, CSU

The Earth System

The Earth’s climate results from the interaction of many properties and processes –Solar radiation and orbital geometry –The size, gravitational force, and rotation rate of the planet –The composition, structure, and internal dynamics of the planet –The geography of continents, glaciers, mountain ranges, and oceans –Ocean properties and circulation –Atmospheric constituents, their chemical interactions, circulation, and the hydrologic cycle –The living ecosystems that inhabit the planet, and the biogeochemical transformations they conduct

Origins Earth formed by gravitational accretion ~ 4.7 billion years ago Solar “constant” was ~ 30% less than today Impact heating kept surface hot and sterile Giant collision separated the Moon and helped differentiate chemical layers

Evolution of the Atmosphere 1 ) Volcanic emissions –Water vapor85% –Carbon dioxide 10% –Nitrogen % –Sulfur % –Particles and surface materials 2)When collisions became less frequent, planet cooled 3)Water vapor condensed, forming oceans 4)Strong acids (HCl, HNO 3, H 2 SO 4 ) dissolved readily into the oceans, taken out of atmosphere, combined with dissolved materials from continental weathering to make sea salt 5)Condensation of oceans, aqueous chemistry, and sedimentation have steadily depleted CO 2 6)Role of life in creating oxygen & O3 and in depleting CO2

Plate Tectonics Continental plates are lighter (buoyant) and rise in collisions, whereas oceanic plates subduct Continents can “bunch up” due to collisions, forming supercontinents (“Pangea,” “Gondwana”) Continental drift can radically alter the geometry of ocean basins, with corresponding dramatic changes in ocean circulation and poleward heat transport Image Courtesy USGS

Land and Ocean What controls these variations? What are the consequences in the atmosphere? What are the consequences in the oceans?

Water on Earth Should be called “Planet Water” Atmosphere is a bit player in storage of water Very dynamic cycling

Energy Reservoirs The oceans are about 4000 m deep The top 10 m equal the mass of the atmosphere The top 3 m equal the heat capacity of the atmosphere! The state of the oceans determines the climate on time scales of thousands to millions of years! Ocean Atmosphere

Deep, Dark, and Cold Warm buoyant “raft” floats at surface Cold deep water is only “formed” at high latitudes Very stable, hard to mix, takes ~ 1000 years! Icy cold, inky black, most of the ocean doesn’t know we’re here yet! sfc 4 km

Ice and Snow

Greenland is covered with ice to depths of several kilometers Permanent ice cover further north overlies an isolated ocean basin Land and Sea Ice

Continental Ice

Sea Ice

Cause and Effect Climate is a result of physical, chemical, & biological processes Forcing causes a response Strength of response to unit forcing is called “sensitivity”

Response Times Response to climate forcing can be fast, slow or in between Persistent forcing produces a range of responses on different time scales Eventual equilibration to forcing

Responses to forcing can be fast, slow, or both! Response Times

Cycles of Forcing and Response Strength of response depends on matching time scales of forcing and response! Mismatched time scales may produce a weak response to strong forcing or vice versa

Feedback Forcing can be either amplified or reduced by the climate system itself Amplifying effects are called “positive feedback” Damping effects are called “negative feedback”

Cause and Effect External forcing affects internal processes Internal feedback can amplify or damp forcing System responds in many ways over time

Changing Earth System

Climate Changes