Lecture 4

Question 1

external forcings

Answer 1

forcing outside natural climate system
- orbital
- solar
- volcanism bc rando and unpredictable
- anthropogenic changes
- tectonic

Question 2

internal forcings

Answer 2

• GHG
• albedo
• aerosols
• ocean-atmospheric patterns

Question 3

eccentricity

Answer 3

• gravitational interactions with planets
• orbit
• only one to alter average insolation
• 100-400 ka

Question 4

obliquity

Answer 4

• tilt
• affects strength of seasonal insolation (seasons)
• more tilt means more extreme seasons
• 41 ka

Question 5

___ obliquity favours ice ages why?

Answer 5

low
- bc we get less summer insolation and less insolation at higher latitudes

Question 6

precession

Answer 6

• wobble
• when axis pointing at perihelion (closest to sun) N hemi gets more seasonality and vice versa when pointing away
• 19-23ka

Question 7

glacial-interglacial cycles driven by

Answer 7

changes in summer insolation at Northern latitudes
- bc it has most land and is where ice sheets begin

Question 8

solar forcing

Answer 8

caused by change in total solar irradiation received at top of atmosphere

Question 9

long term solar forcing

Answer 9

Sun increasing in strength over time

TSI one of largest contributors to natural climate variabilty on the Holocene

Question 10

short term solar forcing

Answer 10

random variations in TSI on centennial scales

Question 11

very short solar forcing

Answer 11

sunspot cycles
- schwabe cycle (11 years)
- solar flares caused by changes in sun’s magnetic field

Question 12

aerosols

Answer 12

tiny particles suspended in atmosphere absorbing and scattering light
- smog, fog, etc

Question 13

aerosol direct affect

Answer 13

reflection/absorption of sunlight by aerosols themselves
- net cooling effect
- (physically reflect or absorb)

Question 14

indirect affect of aerosols

Answer 14

can change albedo of other aspects of earth
- cloud brightening as aerosols seed clouds and change size of droplet to be smaller and denser and more reflective
- aerosols fall back to earth and accumulate and darken ice
- sites for chemical reactions like ozone depletion

Question 15

aerosol types

Answer 15

dust
- mostly saharan
sea salt
- ocean spray
volcanic
- ash and sulphur
natural carbon
- forest fires, pollen, smoky mountains (trees breathe out aerosols that create clouds)
human
- burning of fossil fuels, landuse, incineration, etc

Question 16

Volcanic forcing

Answer 16

ash and so2 released into cools earth as they are very reflective
- stochastic
- caused by glacial pump
- many climate and TSI variabilities line up w volcanic activity

Question 17

glacial pump

Answer 17

decompression of magma chamber leads to increased eruptions, thought to be cause dby isostatic rebound from glacier melt