Earth Science:A study in Change - Natural

Resources: Our Climate

Global Warming vs. Greenhouse Effect

• Weather NOT the same as climate!• They are DIFFERENT! (Weather = short term

conditions, Climate = long term pattern)• Greenhouse effect: a natural warming of the

surface of the Earth and lower atmosphere– Caused by stratospheric ozone– Also caused by trace gases: CO2 (.039%) & H2O

• These are the MOST important gases to the greenhouse effect.

Greenhouse Effect Process• Greenhouse gases let solar radiation in

without reflecting/absorbing it, then absorb radiation from the earth.– Two heat sources for the atmosphere, 1 = sun and

2 = earth.– Bottom sandwich bun– Longer wavelength

• Life on Earth CANNOT exist without the greenhouse effect! It would be too cold.

Global Warming• Global Warming: the overall increase in global

temperatures due to manmade increase of carbon dioxide levels.– Caused by burning fossil fuels– Same process as greenhouse effect– Results in changing the RATE of global climate changes.

• Keep in mind: Global Mean (average) Temperature does naturally change.– Called Global climate change – Due to a combination of orbit, rotation, precession, solar

activity, &. . . &. . . .&. . . – This is what caused the ice ages– Life is messy! We know we can affect the atmosphere, but

by how much?

Global Mean Temerature NOAA (updated 5/2011)

Global Temperature Variations in perspective

Book diagram starts here.

Industrial revolution starts here.

Carbon Dioxide Levels(pg 602)

CO2 Levels

• CO2 naturally varies annually due to tilt of planet. – majority of plant life located in Northern

hemisphere. – 6CO2 + 6H2O C6H12O6 + 6O2

– Summer in north = more photosynthesis = lowering of CO2

LIGHT

Historic CO2 levels -measured many ways. . .

• Measured using isotope data from glaciers– Thousands of years old– Trap gas bubbles– Ice cores taken and analyzed

• From this data (800,000 yrs), CO2 never rose above 290 ppm until after the industrial revolution.– 1ppm= one credit card on a football field– 1ppm = one step on a walk of 568 mi– 1ppm = 726 people (150 lbs. ea.) sharing one

chocolate bar.– 1ppm =one minute in 2 years

• 290ppm = 4hrs 48min

CO2 Levels• CO2 also changes by approximately 100

ppm every one million years. (.0001 ppm/yr)

• Man made rate of change = approximately 2 ppm/yr.

• Do the math! Humans overwhelm natural variations (20,000 X natural rate of change).

• Began during industrial revolution, one cause is the burning of fossil fuels.

Carbon Dioxide and Temperature

CO2 and temperature• Global temperatures closely follow CO2

levels.• From glacial studies we know that global

temperatures are sensitive to changes of about 1oC.– This means that lots of “stuff” happens when

global temperatures change even a little.• Current rate of CO2 increase means an

approximate 2-11oC rise of global temperature by 2100.

Trends and projections• Minimum temperatures are increasing at a

faster rate than maximums. – “squeezing” the habitable zone

• Nighttime lows show greater warming trend than daytime highs

• CO2 emissions reduced = 2.2oC-3.3oC(4oF-6oF) increase.

• CO2 emissions same = 3.9oC-6.1oC(7oF-11oF)• Polar regions tend to have greater effects.

– In US, for example, Colorado annual temperature increase = .9oF, North Dakota = 2.9oF, since 2011

Effects of Temperature Increase

• Thermal inertia - latent heat/specific heat of water: water heats & COOLS slower than land/atmosphere.– Even if we made all necessary changes today, will

still see effects until at least 2100!• Water and CO2 in atmosphere increases with

temperature.– Due to increased capacity.

• When water and CO2 increase, so does temperature = positive feedback loop

Global and Regional effects: DIFFERENT

• Precipitation changes patterns– Increased annual precipitation due to heavy

downpours. (US increase = 5%)– Regionally: Ne decreased annual snowfall– Northern regions = wetter, South/West = drier– Therefore, LOCAL effects are NOT THE same as

GLOBAL effects.• Increased evaporation = more irrigation =

less water in Ogallala Aquifer

Greenland & Antarctic land ice sheets

• In Greenland, 70 meters of ice lost in the last 5 yrs.

• Approximately 150 km3/yr• Translates to a rise in sea level of 3

cm/yr– This is double the rate of the last 15 yrs.

Ice sheet loss• If continues at this rate = irreversible

– Ice = high albedo (reflectivity)– Recall: 30% of all incoming solar radiation is

reflected!– Ice loss means lower reflectivity and increase of

absorption.– Positive feedback loop

• 3oC of global warming = 25 m higher sea level– Florida, Japan, Bangladesh, – All under water!– Since 1900 the San Francisco Bay Tide Station

has recorded an 8 in. rise in sea level.

USGS estimationshttp://cegis.usgs.gov/video/1Km/

sealevel_us.avi

Impact on Species• Habitats will change altitudes.

– Cooler climates at higher altitudes will warm– Species will migrate up to higher altitudes.– Species that prefer cool climates migrate. . where?– Increase of invasive species

• Current rate of ~3oC = ~25-50% of species lost (Nobel 2008)– Nobel 2012 = rate of change more like last global

warming event that had 92% species lost.• Slow to <1oC = ~<10% of species lost• Lowers diversity and subjects survivors to

extinction.

Impact on Humans• Water shortage

– Huh? Water for much of Tibet and California comes from snow pack melting or glacial melting. (decrease in preciptiation = less snowfall)

– Increased evaporation = more irrigation for food production = less water in Ogallala Aquifer

• Change in ocean chemistry/currents– Impact on local climates = changes precipitation

globally– Fishing and trade routes change– Food shortage due to decreased nutrient

supply(fishing), decreased pH harms hard shelled organisms.

Impact on Humans (cont.)• Coastal communities & Sea level rise

– Approx 10% of world population lives below 33ft elevation. (Omaha elevation = 1,090 ft)

• Tundra thawing– Increases erosion & methane release– Damages towns/homes/water lines/etc

• Physiology– What range can our bodies function well in?

(Tuna hearts)