Climate Change A simple climate model - PowerPoint PPT Presentation

Loading...

PPT – Climate Change A simple climate model PowerPoint presentation | free to download - id: 581b08-Nzc2Z



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

Climate Change A simple climate model

Description:

Climate Change A simple climate model Dudley Shallcross and Tim Harrison, Bristol University Example calculations TE = [ FS(1-A)(1 + VIS) / (1 + IR )]0.25 FS /Wm-2 ... – PowerPoint PPT presentation

Number of Views:52
Avg rating:3.0/5.0
Slides: 51
Provided by: Nhe78
Learn more at: http://www.chemlabs.bristol.ac.uk
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Climate Change A simple climate model


1
Climate ChangeA simple climate model
  • Dudley Shallcross and Tim Harrison, Bristol
    University

2
Simple climate model
  • A simple climate model
  • Students can use an excel spreadsheet to run it
  • Simple factors to change
  • Can look at feedbacks on climate
  • Ideas and questions e-mail d.e.shallcross_at_bris.ac.
    uk or t.g.harrison_at_bris.ac.uk

3
Grannys model of climate 1
Earth Sun Temperature of the Earth
10o C
4
Big problema clouds and ice
  • From sun (100)
  • Scattered out to space
  • by clouds (24)
  • Scattered out to space
  • by the surface (6) (skiing)
  • Surface Land/water Ice
  • 30 of incoming solar radiation reflected back
    out to space without being absorbed (Earths
    albedo A 0.3)

5
Grannys model of climate 2
Earth Sun With clouds and
ice Temperature of the Earth - 18o C
6
Granny is now very cold
  • What can she do to warm herself up?
  • Move closer?
  • (Earths distance to the Sun varies but not
    enough to make up this loss in heat)
  • Get a blanket? (In effect this is what Greenhouse
    gases do)

7
CO2
O3
8
Grannys model of climate 3 (with blankets)
Earth Sun with clouds and ice and
greenhouse gases Temperature of the
Earth 16o C
9
  • Thanks to Mike Stuart 2008
  • www.disphoria.co.uk
  • For the granny cartoons

10
Essential Background Physics Black Body
Radiation   All bodies radiate energy as
electro-magnetic radiation.   A black body
absorbs all radiation falling on it. It emits
radiation as a function of its surface
temperature without favouring particular
frequencies.   The Stefan-Boltzmann Law relates
how the total energy emitted by a black body
relates to the temperature by     Equation
1   where I is the energy per unit area emitted
per second (Watts m-2 s-1), T is the Absolute
Temperature (K) and ? is the Stefan-Boltzmann
constant (5.67 x 10-8 W m-2 K-4).
11
Model 1 Heat in, heat outBalanced Flux model
  • We know that the energy from the Sun reaching
    the top of the atmosphere, the so-called solar
    constant S, is 1370 Wm-2.
  • If we take the radius of the Earth to be RE, in
    this very simple model we can see that the Earth
    absorbs solar radiation over an area ?R2 (i.e. a
    flat atmosphere) but emits energy from an area
    4?R2 (i.e. from the entire surface).

12
Energy Out Energy In Out ?TE4 4?RE2 IN
S x Area IN 1370 pRE2 W m-2
13
Surface temperature looks OK
  • Energy in Energy out
  • 1370 x ?RE2 ?TE4 x 4? RE2
  • TE4 1370 4 x
    5.67x10-8
  • TE 279 K
  • (note for later we will call 1370/4 FS)

14
Big problema clouds and ice
  • From sun (100)
  • Scattered by
  • Clouds (24)
  • Scattered by
  • the surface (6)
  • Surface
  • Land/water Ice
  • 30 of incoming solar radiation reflected back
    out to space without being absorbed (Earths
    albedo A 0.3)

15
Re-calculate TE
24 of solar flux is reflected by clouds 6
Scattered by surface
TE 255 K (- 18 o C) Cold
16
Terrestrial Radiation The Earth also acts as a
blackbody radiator TE 288 K so most of the
irradiance from the Earth is in the infra-red
part of the spectrum and peaks at about 10 ?m.
little overlap between the incoming solar
radiation and the outgoing infra-red radiation
from the Earths surface. separated by a gap at
around 4 ?m shortwave (SW) radiation longwave
(LW) radiation
17
Atmospheric Window (C-F bonds absorb ir energy)
18
Model 2 One layer atmosphere
  • FS(1-A) Fg?IR
  • Fa
  • Atmosphere
  • FS(1-A)?VIS Fa Fg
  • Ground

?IR
?VIS
19
FS Energy Flux from the Sun (1370/4)A Albedo
or reflectivity of Earth typically 0.3
  • FS(1-A) Fg?IR
  • Fa
  • Atmosphere
  • FS(1-A)?VIS Fa Fg
  • Ground

?IR
?VIS
20
?VIS Transmittance of UV/Vis light from the
Sun through the Earths
atmosphere to the ground. If all the light is
absorbed ?VIS 0.0 and if all
the light passes through ?VIS 1.0
  • FS(1-A) Fg?IR
  • Fa
  • Atmosphere
  • FS(1-A)?VIS Fa Fg
  • Ground

?IR
?VIS
21
?IR Transmittance of IR light from the Earth
through the Earths atmosphere
to space. If all the ir light is absorbed ?IR
0.0 and if all the ir light
passes through ?IR 1.0
  • FS(1-A) Fg?IR
  • Fa
  • Atmosphere
  • FS(1-A)?VIS Fa Fg
  • Ground

?IR
?VIS
22
Fa Energy flux from the atmosphere, in a
balanced flux model the flux upwards
and the flux downwards are the same.
  • FS(1-A) Fg?IR
  • Fa
  • Atmosphere
  • FS(1-A)?VIS Fa Fg
  • Ground

?IR
?VIS
23
Fg?IR The IR energy flux from the ground
modified by the transmittance
properties of the Earths atmosphere that now
escapes to space.
  • FS(1-A) Fg?IR
  • Fa
  • Atmosphere
  • FS(1-A)?VIS Fa Fg
  • Ground

?IR
?VIS
24
FS(1-A)?VIS The UV/Vis energy flux reaching
the ground from the Sun
modified by the transmittance properties of
the Earths
atmosphere.
  • FS(1-A) Fg?IR
  • Fa
  • Atmosphere
  • FS(1-A)?VIS Fa Fg
  • Ground

?IR
?VIS
25
Fg The IR energy flux from the Earths
surface.
  • FS(1-A) Fg?IR
  • Fa
  • Atmosphere
  • FS(1-A)?VIS Fa Fg
  • Ground

?IR
?VIS
26
Fluxes at the top of the atmosphere must balance
  • FS(1-A) Fg?IR
  • Fa
  • Atmosphere
  • FS(1-A)?VIS Fa Fg
  • Ground

?IR
?VIS
27
Fluxes at the ground must balance
  • FS(1-A) Fg?IR
  • Fa
  • Atmosphere
  • FS(1-A)?VIS Fa Fg
  • Ground

?IR
?VIS
28
Simply balance energy fluxes
  • At the surface
  • FS(1-A) ?VIS Fa Fg (a)
  • And at the top of the atmosphere,
  • Fg ?IR Fa FS(1-A) (b)
  • If the two fluxes are in balance
  • Fg FS(1-A)(1 ?VIS) / (1 ?IR )

29
Finally
  • Fg ?TE4 FS(1-A)(1 ?VIS) / (1 ?IR )
  • TE FS(1-A)(1 ?VIS) / s(1 ?IR ) 0.25
  • Assuming FS 336 Wm-2
  • A 0.3
  • ?VIS 0.8
  • ?IR 0.1
  • TE 287 K

30
Example calculations
  • TE FS(1-A)(1 ?VIS) / s(1 ?IR )0.25
  • FS /Wm-2 336 336 336 336
  • A 0.3 0.0 0.0 0.3
  • ?VIS 1.0 1.0 1.0 1.0
  • ?IR 1.0 1.0 0.0 0.0
  • TE /K 254 278 330 302

31
Example calculations
  • TE FS(1-A)(1 ?VIS) / s(1 ?IR )0.25
  • FS /Wm-2 336 336 336 336
  • A 0.3 0.0 0.0 0.3
  • ?VIS 1.0 1.0 1.0 1.0
  • ?IR 1.0 1.0 0.0 0.0
  • TE /K 254 278 330 302

32
Example calculations
  • TE FS(1-A)(1 ?VIS) / s(1 ?IR )0.25
  • FS /Wm-2 336 336 336 336
  • A 0.3 0.0 0.0 0.3
  • ?VIS 1.0 1.0 1.0 1.0
  • ?IR 1.0 1.0 0.0 0.0
  • TE /K 254 278 330 302

33
Example calculations
  • TE FS(1-A)(1 ?VIS) / s(1 ?IR )0.25
  • FS /Wm-2 336 336 336 336
  • A 0.3 0.0 0.0 0.3
  • ?VIS 1.0 1.0 1.0 1.0
  • ?IR 1.0 1.0 0.0 0.0
  • TE /K 254 278 330 302

34
Example calculations
  • TE FS(1-A)(1 ?VIS) / s(1 ?IR )0.25
  • FS /Wm-2 336 336 336 336
  • A 0.3 0.0 0.0 0.3
  • ?VIS 1.0 1.0 1.0 1.0
  • ?IR 1.0 1.0 0.0 0.0
  • TE /K 254 278 330 302

35
Quick Questions TE FS(1-A)(1 ?VIS) / s(1
?IR ) 0.25 Assuming FS 336 Wm-2
A 0.3
?VIS 0.8 ?IR 0.1 TE 287 K
  • 1 If the Earth were to move closer to the Sun
    such that the solar constant increases by 10
    calculate the effect on the surface temperature
    of the Earth.
  • 2 If the Earths ice caps were to grow such that
    25 of the surface was covered in ice (it is
    about 6 now) calculate the effect on the surface
    temperature of the Earth.

36
Quick Questions TE FS(1-A)(1 ?VIS) / s(1
?IR ) 0.25 Assuming FS 336 Wm-2
A 0.3
?VIS 0.8 ?IR 0.1 TE 287 K
  • 1 If the Earth were to move closer to the Sun
    such that the solar constant increases by 10
    calculate the effect on the surface temperature
    of the Earth. 294 K (up 7 K)
  • 2 If the Earths ice caps were to grow such that
    25 of the surface was covered in ice (it is
    about 6 now) calculate the effect on the surface
    temperature of the Earth. 265 K (- 8 C)

37
Secrets in the Ice
  • Snow accumulation lays down record of
    environmental conditions
  • Compacted to ice preserving record
  • Drill ice core date

38
Climate Change
39
Milankovitch Cycles
  • Climate shifts correspond to three cycles related
    to Earths orbit
  • Effect intensity of solar radiation
  • Caused by gravitational attraction between the
    planets (mainly Jupiter) and Earth
  • Predictions from cycles match major
    glacial/interglacial periods and minor periodic
    oscillations in climate record

40
Milankovitch Cycles
  • Obliquity of Earths axis of rotation (tilt)
    changes from 22 (currently23.5) to 24.5 ?
    41,000 years
  • Precession (wobble) changes the quantity of
    incident radiation at each latitude during a
    season ? 22,000 years
  • Eccentricity of Earths orbit varies from nearly
    circular to elliptical. At low eccentricity
    orbits the average Earth-sun distance is less ?
    100,000 years

41
Source OSTP
42
Indicators of the Human Influenceon the
Atmosphere during the Industrial Era
Source IPCC TAR 2001
43
Climate Change
44
Variations of the Earths Surface Temperature
relative to 1961-1990 average
Source IPCC TAR 2001
45
Projected Changes in Annual Temperatures for the
2050s
The projected change is compared to the present
day with a 1 increase per year in equivalent CO2
Source The Met Office. Hadley Center for Climate
Prediction and Research
46
Temperature Projections
  • Global average temperature is projected
  • to increase by 1.0 to 10 C from 1990 to
  • 2100
  • Projected temperature increases are
  • greater than those in the SAR (1.8 to
  • 6.3C)
  • Projected rate of warming is
  • unprecedented for last 10,000 years

Source IPCC TAR 2001
47
Model simulation of recent climate
Natural forcings only(solar, volcanic etc.
variability)
Anthropogenic forcings only(human-induced
changes)
The Met Office
48
Simulated global warming 1860-2000Natural
Man-made factors
49
Factors affecting climate system
Establishing a link between global warming and
man-made greenhouse gas pollution?
The global mean radiative forcing of the climate
system for the year 2000, relative to 1750 (IPCC,
2001).
50
Impacts of Climate on the UK
UK will become warmer High summer temperatures
more frequent Very cold winters increasingly rare
Winters will become wetter and summers may become
drier
About PowerShow.com