SIO15-12: Lecture 21: Long- and Short-term Climate Changes

Lecture 21: Global Climate Changes

aquarium trip 1 (HW7) last day tomorrow

aquarium trip 2 (HW8) assignment is now online (and available here)

• return HW#6 (to your right)• pick up HW#4,5 (to your left)

office hour: Tue, Nov 20 4-5:50 pm York3030

midterm 2 (NOV 30) study guide will be online Nov 23

• return trip1 on TABLE!

SIO15-12: Lecture 21: Long- and Short-term Climate Changes

Where do Hurricanes Occur? NamingWhere do Hurricanes Occur? Naming

Image: NASA’s Earth Observatory

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hurricanes

hurricanes

typhoons

cyclones

• most hurricanes in W. Pacific (typhoons)most hurricanes in W. Pacific (typhoons)• more hurricanes in E. Pacific than in Atlanticmore hurricanes in E. Pacific than in Atlantic• Indian Ocean: cyclonesIndian Ocean: cyclones

Hurricane Hurricane pathspaths::N hemisphere: clockw.N hemisphere: clockw.S hemisphere: countercw.S hemisphere: countercw.Hurricane Hurricane windswinds::N HS: ccw S HS: cwN HS: ccw S HS: cw

SIO15-12: Lecture 21: Long- and Short-term Climate Changes

• strongest hurricanes in W. Pacificstrongest hurricanes in W. Pacific• no hurricanes in S. Atlanticno hurricanes in S. Atlantic (1 exception: hurricane Catarina, Mar 2004)(1 exception: hurricane Catarina, Mar 2004)• “ “ “ “ “ “ S.E. PacificS.E. Pacific

Location and Frequency of HurricanesLocation and Frequency of Hurricanes

Image: NASA’s Earth Observatory

hurricanes do not hurricanes do not cross equatorcross equator(Coriolis Effect)(Coriolis Effect)

strong cold currentsstrong cold currents

winds unfavorablewinds unfavorable

SIO15-12: Lecture 21: Long- and Short-term Climate Changes

El Nino and Atlantic HurricanesEl Nino and Atlantic Hurricanes

-1997 1997 El NinoEl Nino cooler trop. Atl.cooler trop. Atl. dry summers in West Africadry summers in West Africa- - less Atl. hurricanesless Atl. hurricanes

-1998 1998 La NinaLa Nina warmer trop. Atl.warmer trop. Atl. wet summers in West Africawet summers in West Africa- - more Atl. hurricanesmore Atl. hurricanes

Image: Abbott “Natural Disasters”

SIO15-12: Lecture 21: Long- and Short-term Climate Changeshttp://en.wikipedia.org

sustained winds: 185mph gusts: 220mph pressure: 902 mbar no landfall but hit Socorro Island no fatalities but $3.2Mio Damage

1997: Cat 5 Hurricane Linda(strongest ever recorded in E.P.)

Hurricanes close to home (Baja California)Hurricanes close to home (Baja California)

cut power to met. station on Socorroclosed resorts in Bajaflooding in mainland Mexico15ft surge in So. Cal.5 people swept off jetty in Newport Beachsevere flooding and mudslides in So. Cal.(destroyed 2 houses, damaged 77)

Linda and Mainland

SIO15-12: Lecture 21: Long- and Short-term Climate Changes

S.D. Meteorological ObservationsS.D. Meteorological Observations

no hurricane ever made landfall in So. Cal. landfall of a tropical storm in 1939 ($ 2Mio damage) some came into SW but made landfall somewhere else

meteorological records don’t go back very far newspaper accounts -> Oct 2 1858 San Diego Hurricane from winds speeds and pressure -> category 1/F2 winds ships blown ashore house completely destroyed 1860 population of New San Diego county: 4325

Damage if such a hurricane would strike today: several $100Mio

SIO15-12: Lecture 21: Long- and Short-term Climate Changes

Hurricanes in Southern California?Hurricanes in Southern California?

from: Marshak “The Earth: Portrait of a Planet”

HURRICANESHURRICANES- need warm water to grow/sustainneed warm water to grow/sustain- cold California Current protects uscold California Current protects us- “ “no hurricane has ever made landfall in SoCal”no hurricane has ever made landfall in SoCal”- global warming could shift currents

SIO15-12: Lecture 21: Long- and Short-term Climate Changes

….why do we have to know?...

“hurricanes over Scotland;new ice age over a few weeks”

ONLY IN HOLLYWOOD (2004) BUTNEVERTHELESS WORTH WATCHING

Long- and Short-term Climate ChangesLong- and Short-term Climate Changes

SIO15-12: Lecture 21: Long- and Short-term Climate Changes

Recent Temperature and Atmospheric CORecent Temperature and Atmospheric CO22

• T has increased nearly exponentially in last 50 years• rate not seen in previous 950 years• proxies: tree rings, pollen counts, etc

Why do we care about this in a natural disasters class?• climate changes can happen rapidly (over several years)• clues of what to expect may lie in past

current CO2 changing dramatically

SIO15-12: Lecture 21: Long- and Short-term Climate Changes

+ other stuff-CO2 353ppm (0.0353%) (1992); 391 ppm (2012)- Ne 18ppm- He 5ppm- CH4 2ppm- Kr 1ppm- H2O variable (water vapor)

Before Life Now

- before life: mainly CO2

- today: mainly N2 and O2Greenhouse Gases: CO2, CH4, H2O

Greenhouse effect: see Lecture 15

Review: Composition of Earth’s AtmosphereReview: Composition of Earth’s Atmosphere

SIO15-12: Lecture 21: Long- and Short-term Climate Changes

Radiative Forcing-Greenhouse GasesRadiative Forcing-Greenhouse Gases

the 2most important greenhouse gases: natural and anthropogenic: CO2, CH4

* anthropogenic: CFC; destroys stratospheric ozone

-CO2 contribute 60%-CH4 16% (less abundant but more effective)

relative ability of gas to add or reduce warming

from: Abbott “Natural Disasters”

SIO15-12: Lecture 21: Long- and Short-term Climate Changes

Radiative Forcing - AerosolsRadiative Forcing - Aerosolsrelative ability of substance to add or reduce warming

radiative forcing of aerosols (e.g. SO2): negative in upper atmospherepositive in lower atmosphere

Radiative Forcing – HRadiative Forcing – H22OO

relative ability of H2O to add or reduce warming

clouds: negative (reflects sunlight) AND positive (reflects IR emitted by Earth)water vapor: positive

SIO15-12: Lecture 21: Long- and Short-term Climate Changes

feedback: secondary process that responds to and influences a change

Feedback MechanismsFeedback Mechanisms

positive feedback: enhances change (e.g. warming melts ice sheets -> decrease in albedo -->> more warming)(e.g. warming thaws tundra -> release of methane -->> more warming!!)

negative feedback: counteracts/moderates change (e.g. warming melts ice sheets -> cold fresh water floats on warm ocean -->> inhibits oceanic heat transport -> cooling)(e.g. warming causes more evaporation -> clouds -->> cooling)

SIO15-12: Lecture 21: Long- and Short-term Climate Changes

Venus: run-away greenhouseEarth: moderate greenhouse

most COmost CO22 is stored in limestones from chemical weathering, is stored in limestones from chemical weathering,

fossil shells, corals etc. as calcium carbonate fossil shells, corals etc. as calcium carbonate

Early Earth: 98% CO2 290ºCEarth Today: 0.038% 16ºC/61ºF

young faint sun paradox: sun only 70% of today’s output but 1 Ga old Earth too hot for water on Earth

Climate of the Early EarthClimate of the Early Earth

SIO15-12: Lecture 21: Long- and Short-term Climate Changes

rifting and volcanism affect climate spreading rates affect sea level (shallow seas) position of continents affect climate - albedo (large continents near pole -> cooling) - arrangement of continents affect ocean circulation

Sun, Plate Tectonics and Climate ChangeSun, Plate Tectonics and Climate Change

changes in solar output on scales of millions of years early sun was fainter than today; 10% per Ga (billion years)

INDITCATORS:glacial striationssedimentary rock- fossil content- plant casts

igneous rocks cannot tell past climate!

SIO15-12: Lecture 21: Long- and Short-term Climate Changes

-recent long-term trend is coolingrecent long-term trend is cooling-Earth was mostly warmer than today!Earth was mostly warmer than today!-glaciation very rareglaciation very rare

-colder periods tend to be driercolder periods tend to be drier

Climate over TimeClimate over TimeT and PrecipitationT and Precipitation

Cretaceous: a lot warmer than today Cretaceous: a lot warmer than today --> 3 times more CO--> 3 times more CO22????????

current long-term trend: COOLING

SIO15-12: Lecture 21: Long- and Short-term Climate Changes

Changes in Global Sea LevelChanges in Global Sea Level

Sea level has changed by many 100m over time

• lower sea level during glaciationlower sea level during glaciation• higher sea level in warm periodshigher sea level in warm periods• sea level dropped by 200m in last 10 Mio yrssea level dropped by 200m in last 10 Mio yrs

sea level also depends on sea floor spreading!!sea level also depends on sea floor spreading!!--> cannot infer T directly!!-> cannot infer T directly!!

SIO15-12: Lecture 21: Long- and Short-term Climate Changes

recent short-term trend: WARMING

Short-Term Changes (1000s of years)Short-Term Changes (1000s of years)

- short-term changes NOT cause by plate tectonics

possible causes:• Milankovich cycles• change in solar output• volcanism• ocean currents

indicators:• ice cores (CO2/oxygen isotopes)• coral rings (oxygen isotopes)• tree ring• pollen composition

SIO15-12: Lecture 21: Long- and Short-term Climate Changes

Amount of insolation changes with Earth’s orbital parameters

- eccentricity (100,000 yrs)- tilt of spin axis/obliquity (41,000 yrs)- precession (25,000 yrs)

The Milankovitch CyclesThe Milankovitch Cycles

SIO15-12: Lecture 21: Long- and Short-term Climate Changes

The Milankovitch Cycles The Milankovitch Cycles

- Milankovich cycles change T by up to 4oC- However: T during ice age 5-7oC/coast and 10-13oC inland

Earth’s orbital parameters: eccentricity, obliquity, precession

something else needed: feedback mechanisms!

SIO15-12: Lecture 21: Long- and Short-term Climate Changes

- saw-tooth pattern: warming happens faster than cooling

- positive feedback mechanisms stronger for warming than for cooling

research done at SIO/UCSD!!

Milankovitch and the Positive FeedbackMilankovitch and the Positive Feedback

SIO15-12: Lecture 21: Long- and Short-term Climate Changes

Popquiz #10

your name and student ID

Name the three factors that increase a hurricane surge.

(all three needed for full credit!)