Transcript Climate

Climate Change and
Climate Modeling
Kristina Fitzhugh
November 17, 2009
Earthrise
“The picture became known as ‘Earthrise’ and
the image of the world from the perspective of
a desolate lunar surface became an iconic
reminder of our need to protect the Earth’s
fragile resources. Earthrise and images like it are
widely credited with inspiring the environmental
movement and indirectly the start of the
Environmental Protection Agency in 1970.” (5)
What is Climate Change?
•“A long-term change in the Earth’s climate, or
of a region on Earth”
•Can be the change in average weather or
change in weather distributions
(ex: fewer or greater extreme weather
events)
•Can occur locally, regionally, or globally (1,2,4)
Misconception 1
•Temperatures in some areas aren’t increasing,
so global warming is a myth.
“It is certainly true that the temperature is
not rising at every point on the
planet...global warming refers to the rise in
average temperature...the impacts of
climate change will not be the same
everywhere”
Climate Change vs. Global Warming
•Terms sometimes used interchangeably
•Global warming refers to the average surface
temperature increase caused by rising levels of
greenhouse gases (ghg’s)
•Originally introduced in a 1975 Science article
by geochemist Wallace Broecker of Columbia
University
•Previously referred to as “inadvertent
climate modification”
(4)
Climate Change vs. Global Warming
•Scientist knew human activity would affect the
climate, but they didn’t know how
•In 1979 the National Academy of Science
conducted a study on the effects of carbon
dioxide on climate
•Adopted Broecker’s term when referring to
rising surface temperatures
•Used “climate change” when referring to
other changes to the climate
(4)
Misconception 2
•Scientists disagree about whether humans are
causing the Earth’s climate to change
“Scientists overwhelmingly agree that the
Earth is getting warmer, that this trend is
caused by people, and that if we continue to
pump greenhouse gases into the
atmosphere, the warming will be
increasingly harmful”
Causes of Climate Change
•Plate tectonics
•Ocean currents
•Volcanoes
•Earth’s orbit and tilt
•Greenhouse gases
Plate Tectonics & Ocean Currents
•Earth’s lithosphere is broken into
tectonic plates
•Plates sit on the asthenosphere
•Plates move in relation with one
another at plate boundaries
•Moved by convection currents
beneath the plates
•Position of continents affect
ocean currents
(4)
Plate Tectonics & Ocean Currents
•The ocean is
important in
controlling heat and
moisture transfer
•Location of land
masses affects the
distribution of
temperature
•Affects climate
around the world (4)
Volcanoes
•Emit aerosols and carbon dioxide into the
atmosphere
•Aerosols block sunlight and causes short
term cooling, though no long term affects
• CO2 causes warming, but relatively small
amount released compared to humans
(6)
Earth’s Orbit & Tilt
•Majority of Earth’s land
mass is above the equator
•Spring/Summer – Northern
Hemisphere is pointed toward
the Sun
•Fall/Winter – Northern
Hemisphere is pointed away
from the Sun
(7)
Greenhouse Effect
Greenhouse Gases
1. Water vapor – the most abundant ghg,
increases clouds and precipitation so
important feedback to the climate
2. Methane – produced naturally and through
human processes, much less abundant than
other ghg’s
• decomposition of waste, rice cultivation, livestock
3. Nitrous oxide – produced naturally and
through human processes
• microbials in soil, agriculture soil management, sewage
treatment
(8)
Greenhouse Gases
4. Chlorofluorocarbons – completely of
industrial origin, severe depletion of ozone
layer
• 1987 Montreal Protocol: complete elimination of
CFC’s by 2000, gone from developing countries by
2010
5. Carbon dioxide – produced naturally and
through human processes, most important
ghg
(8)
Carbon Dioxide Emissions
(9)
Misconception 3
•Climate naturally varies over time, so any
change we’re seeing now is just a part of a
natural cycle
“Climate does naturally change....but these changes all
took place with natural variations in carbon dioxide levels
that were smaller than the one we are now
causing...carbon dioxide levels are higher now than they
have been at any time in the last 650,000 years, which
means we are outside the realm of natural climate
variation. ”
Misconception 4
•Antarctica’s ice sheets are growing, so it must
not be true that global warming is causing
glaciers and sea ice to melt.
“Some ice on Antarctica may be
growing...study shows that overall the ice is
shrinking in Antarctica...Globally more than
85% of glaciers are shrinking.”
Hurricane Katrina
•Less than a month before Hurricane Katrina
hit New Orleans and the South with it’s huge
forces, MIT had released a study that said...
•“Major storms spinning in both the Atlantic
and the Pacific since the 1970’s have
increased in duration and intensity by about
50 percent”
(7)
Climate Models
•Study dynamic climate system
•Predict relation of ghg emissions and future
climate
•Predict regional environments, such as
future stream flow or vegetation changes
•2007 International Panel on Climate Change
Report – models show predicted ranges for
average worldwide temperature increase of:
•Low range: (1.1 – 2.9) 1.8 C
•High range: (2.4 – 6.4) 4.0 C
(11)
Simple Climate Model
•Want to find Earth’s temperature from an
energy model in equilibrium
•solar radiation (S) = 1370/4
•% of albedo (a) = 0.3
•Stefan Boltzmann constant (q) = 5.67 x 10-8
•Temperature (T)
(13)
Stefan Boltzmann Constant
•All bodies radiate energy as electromagnetic
radiation
•SB Law is the total energy, I, emitted by a
black body at any temperature, T, by:
•I(T) = q(T4)
•I = energy per unit area emitted per second
•T = absolute temperature (K)
•q = Stefan Boltzmann constant
(13)
Simple Climate Model
•Looking for the Earth’s temperature
•T = (S/q)(1/4)
•Plugging in values from previous slides we
get...
•T = [(1370/4)/(5.67 x 10-8)](1/4) = 279 K = 6 C
•Too cold!
(13)
Slightly More Complicated Model
•Looking for the Earth’s
temperature
•T= [(S(1-a)(1+Tvis))/(q(1+Tir)](1/4)
•S, a, and q are previously defined
•Tvis=proportion of incoming energy
absorbed by the atmosphere
•Tir=proportion of infrared energy not
absorbed by the atmosphere
•Plugging in we get...
T = 288.5 K ~ 15.5 C
•Average surface temperature
of Earth currently 16 C
(12,13)
Climate Models
• More accurate model
• The model gets very complicated very fast
• Add seasonal cycle
• Cover whole Earth (sphere)
• Plants, clouds, etc.
• Derived from fundamental physical laws,
empirical data, observations
• Ex: Newton’s Law of Motion, Conservation of
Energy, etc.
• Altered to fit large-scale climate system by
adding details about Earth’s geography
• Ex: topography and vegetation
(12,14,15)
Climate Models
Climate Models
•Earth Simulator
•Was the fastest supercomputer in the world
from 2002-2004
•Used to run “global climate models to
evaluate the effects of global warming and
problems in solid earth geophysics”
•35.86 trillion floating point calculations per
second
(2)
Earth Simulator
Do They Really Work?
•IPCC says they have “considerable
confidence”
•Have ability to reproduce features of past and
current climate
•Cannot reproduce the weather of a specific day, but can
calculate the average weather conditions
•Confidence higher for predictions of some
weather circumstances than others
•Higher for temperature than precipitation
(14)
Implications of Climate Change
•Decrease in biodiversity
•Sea level rise
•Higher population concentration
•Spread of disease
•And the list goes on...
•“The Himalayas contain 100 times as much ice as
the Alps and provide more than half of the drinking
water for 40% of the world’s population...that 40% of
the world’s people may well face a very serious
drinking water shortage”
(7)
Misconception 5
•There is nothing we can do about climate
change. It’s already too late.
“There are lots of things we can do – but we
need to start now...We need to reduce our
use of fossil fuels, through a combination of
government initiatives, industry innovation,
and individual action.”
What Can We Do?
•U.S. Mayors Climate Protection Agreement
•Over 500 cities
•Save energy at home
•Lighting, appliances, heating and cooling
•Reduce miles driven
•Public transportation, walk, bike
•Consume less, conserve more
http://www.youtube.com/watch?v=s-_LBXWMCAM
Sources
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15)
http://www.ecy.wa.gov/climatechange/whatis.htm#Q1
http://www.wikipedia.org
http://www.epa.gov/climatechange/science/recentac.html
http://www.nasa.gov/topics/earth/features/climate_by_any_other_name.html
http://blog.epa.gov/blog/2009/07/01/science-wednesday-earthrise/
http://www.epa.gov/climatechange/science/pastcc.html
An Inconvenient Truth by Al Gore
http://climate.nasa.gov/causes/
http://www.epa.gov/climatechange/emissions/co2_human.html
http://www.atmos.washington.edu/~aaron/How%20do%20Climate%20Models%20
Work.ppt#273,18,Greenhouse gases
http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-spm.pdf
http://www.atmos.washington.edu/~aaron/How%20do%20Climate%20Models%20
Work.ppt#273,18,Greenhouse gases
http://www.scienceinschool.org/2008/issue9/climate
http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter8.pdf
http://www.southwestclimatechange.org/climate/modeling/how-models-work