Topics to be covered today Regarding Global Effects HNRT 228 Spring 2016 Future CO2 Forcing Climate Sensitivity – Feedbacks Natural Short and Long-term Forcings Global Warming Impacts

iClicker Question There has been much talk on television news about the severe weather conditions recently across the country. Is this an indication of global warming? A Yes B No

Kaya Identity Model kaya identity model

Future Atmospheric CO2 One emission scenario Range of predictions suggest double pre-industrial by mid-century

Stabilization Scenarios 2000 2300 2100 2200 What our emissions can be for different constant CO2 levels. What do these tell us about future biosphere and ocean sinks?

Committed to Warming: Time Response

A Long View of Fossil Fuel Perturbation

Climate Sensitivity-All about Feedbacks is climate sensitivity parameter  units: K “per” W/m2   determined by feedbacks!

Estimates of Climate Sensitivity T change for a 4 W/m2 forcing (i.e. “double CO2”) Most probable  ~ 0.75 K/(W/m2)

Feedbacks +/- +/- Process or coupling State Variable “feedback loop” Initial Forcing + increases state variable - decreases state variable

Ice-Albedo Feedback + + - Example of a positive feedback Temperature More solar radiation absorbed + Temperature + Albedo - Initial Forcing (e.g. GHG) Ice melts, dark soils exposed

Water Vapor-Temperature Feedback Increased Greenhouse effect + Temperature + Water Vapor + Initial Forcing (e.g. GHG, solar radiation) More evaporation, saturation vapor pressure increase

Atmosphere—Protector of the Oceans? water trap If H2O reaches top of atmosphere it is blown apart by UV radiation H atoms escape to space, never to return Probable cause for no H2O on Venus

IR Flux-Temperature Feedback Example of a negative feedback - Temperature + Outgoing IR flux increases + Initial Forcing (e.g. GHG)

Phytoplankton-DMS-Marine Cloud Feedback Charlson, Lovelock, Andreae, Warren “C.L.A.W.” Hypothesis aerosols and cloudiness + - Solar Radiation (Temperature) + Biogenic Sulfur Emissions Initial Forcing (decreased clouds) + + Photosynthesis DMS - Dimethylsulfide

Cloud Forcings and Feedbacks Low altitude thick clouds  Stratus High altitude thin ice clouds  Cirrus

Aircraft emit particles (and particle precursors) which can nucleate clouds. This activity gives rise to a A Positive radiative forcing B Negative radiative forcing

Aviation Contrails—Positive Forcing October 2004

Clouds and Climate—a complex problem Cirrus: Not so reflective, but absorb and emit at cold T Low Clouds: Absorb IR but emit like warm surface. Reflective

Clouds and Cloud Feedbacks Uncertain! Increased greenhouse effect Albedo + - + Temperature Low Clouds + High Clouds + Atmosphere holds more water Initial Forcing (e.g. GHG, solar radiation) Temperature

Predicted Changes in Cloud Forcings IPCC 2007

Sunspots – Cyclic Changes in Solar Output

~11 year Sunspot Cycle

Radiative Forcing by Solar Cycle

The solar cycle forcing has increased from -0. 1 to 0 The solar cycle forcing has increased from -0.1 to 0.2 W/m2 since 1900. This forcing can explain ____ of 1oC increase in global Avg. T since 1900 A 60 - 70% B 40 - 50% C < 30%

False Assertions: Sun – Global Warming WRONG Solar Cycle WRONG T record Originally from WSJ Article written by two chemists named Robinson

False Assertions: Sun – Global Warming Correct cycle Laut 2003

T Response After Major Eruptions

Natural and Anthropogenic Forcings

El Nino Southern Oscillation-ENSO

Neutral Walker Circulation

El Nino/La Nina State Flip-Flop

El Nino/La Nina Circulation Patterns Strong La Nina Very Strong El Nino

ENSO “Periodicity” El Niño years La Niña years

El Nino Global Impacts

El Nino Impact on Fish Normal El Nino

Climate History

18O Ratios in Sediment and Ice Core

Pleistocene Glacial and Interglacials Reconstruction of land and sea ice 21,000 years ago (last glacial maximum) February July

Records of NH Glaciations Geological Records: glacial deposits, scarring, larger scale Cordilleran Ice Sheet Lake Missoula Spokane Floods (from Lake Missoula)

Milankovitch—Before sediment cores Predicts glacial and interglacial transitions based on variations in Earth’s orbit His results suggested many such transitions in ~ 1 million yrs (he was right) —at the time, no observable records show that many, so his work widely criticized Milutin Milankovitch

Milankovitch Continued While lacking patience for critics, he did not lack confidence Milutin Milankovitch “I do not consider it my duty to give an elementary education to the ignorant, and I have also never tried to force others to use my theory, with which no one could find fault.”

Orbital Forcing Summary Precession Tilt Eccentricity IPCC 2007

Currently NH summer takes place at aphelion, in about 12,000 years, NH summer will occur at perihelion. At this time, SH seasonality will be A stronger B weaker

Solar Insolation at 65N and Glaciation

Recent UW Research Time rate of change of ice volume and solar insolation

The Key For Glaciation Solar insolation in NH summer appears to be key maintaining glaciation. Ice sensitive to melting! Positive Feedback—Destabilizing Climate - T Albedo - Initial Forcing Weaker NH summer insolation + Ice Coverage + Same old ice-albedo feedback, just different initial forcing

Eccentricity: More to Less Circular

Obliquity: More or Less Seasonality

Precessional Cycle: Tilt and Eccentricity Current situation

Questions—In Class Activity Given the behavior of CO2 and CH4 is there a positive or negative feedback with T? Provide a feedback involving marine biota which might explain CO2’s behavior. Suppose marine biota are the cause of CO2’s behavior, is this support for or against Gaia theory? When’s the next glacial maximum? Do you think we’ll get there?