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

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

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

1) http://www.ecy.wa.gov/climatechange/whatis.htm#Q12) http://www.wikipedia.org3) http://www.epa.gov/climatechange/science/recentac.html4) http://www.nasa.gov/topics/earth/features/climate_by_any_other_n

ame.html5) http://blog.epa.gov/blog/2009/07/01/science-wednesday-earthrise/6) http://www.epa.gov/climatechange/science/pastcc.html7) An Inconvenient Truth by Al Gore8) http://climate.nasa.gov/causes/9) http://www.epa.gov/climatechange/emissions/co2_human.html10) http://www.atmos.washington.edu/~aaron/How%20do%20Climate

%20Models%20Work.ppt#273,18,Greenhouse gases11) http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-

spm.pdf12) http://www.atmos.washington.edu/~aaron/How%20do%20Climate

%20Models%20Work.ppt#273,18,Greenhouse gases13) http://www.scienceinschool.org/2008/issue9/climate14) http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-

chapter8.pdf15) http://www.southwestclimatechange.org/climate/modeling/how-

models-work