Global Warming Global Warming

Public perceptionPublic perceptionPhysics of anthropogenic global Physics of anthropogenic global

warmingwarmingKey diagrams Key diagrams ConsequencesConsequencesWhat can you do?What can you do?

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Do you think Global Warming is Do you think Global Warming is happening?happening?

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Americans’ Top 4 Gaps in Understanding Climate Change

1. It’s happening now2. It’s us3. We have a choice4. Scientists agree

Results of recent study by the Yale Project on Climate Change Communication

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It’s happening nowIt’s happening now

• 2011 was the 35th year in a row that the global temperature was above average.

• That means half of all Americans have never lived through a year that was below average.

5State of the Climate 2009 Highlights (NOAA 2010)

6State of the Climate 2009 Highlights (NOAA 2010)

7State of the Climate 2009 Highlights (NOAA 2010)

8State of the Climate 2009 Highlights (NOAA 2010)

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What causes Global Warming?What causes Global Warming?

• Addition of greenhouse gases to atmosphere

• Main culprits are Carbon Dioxide, Methane, and water

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Basic PhysicsBasic Physics

• Greenhouse gases trap heat in Earth’s atmosphere

• Greenhouse gas concentrations have risen

• Trapped radiation has been measured

• Planet will warm!!!!

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Heat-Trapping Blanket

NASA, handweaver.com

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It’s usIt’s us

• Half of human CO2 emissions are added to atmospheric CO2 concentrations each year

• Since 1958, CO2 concentrations have risen from 315 ppm (parts per million) to 392 ppm in 2011 (about 2 ppm per year)

• Other greenhouse gases have risen as well

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CS Fig. 15.17

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Measured Changes in Outgoing Radiation 1970-1997

1818Similar to CS Fig. 15.20

Trees take upCO2

AnimalsProduceMethane

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CS Fig. 15.19

2020

CS Fig. 15.20

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Carbon emissions since 1800Carbon emissions since 1800

Fig. 15.20

Has the burning of Has the burning of fossil fuels resulted in fossil fuels resulted in

increased CO2 increased CO2 concentrations in the concentrations in the

atmosphere?atmosphere?Yes!Yes!-Measurements of air in HawaiiMeasurements of air in Hawaii-Measurements of ancient air Measurements of ancient air preserved in icepreserved in ice

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Bubbles in glacialice preserveair of past cent-uries:

Tell us what CO2

concentrationswere like beforethe industrialrevolution

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Longer recordsLonger records

CurrentCO2 levelsare well aboverange observedduring recentgeologichistory associated withthe ice ages

LastInterglacial

Current

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Best evidence that recent Best evidence that recent warming is anthropogenicwarming is anthropogenic

Data from Mannand others,Nature, 1998;Figure from IPCC 2001Report

Three years in the1990’s are thewarmest in theNorthern Hemisphere,by far, of the last400 years!

Can’t accountFor recent warming Can’t account

For prior warming

Works!

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Figure 15_19Figure 15_19

CS Fig. 15.21

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ConsequencesConsequences

• Planet will warm– High latitudes will warm more than low

latitudes

• Sea level will rise

• Questions:– How fast will warming and sea level rise

occur?– How will Earth’s weather patterns be

affected?

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CS Fig. 15.18

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Fig. 15.24 Grinnell Glacier in Glacier National Park 1n 1914 and 1998.At present rates of melting, there will be no glaciers in Glacier National Parkby 2030.

Global Temperatures Global Temperatures projected to riseprojected to rise

3 to >7 °C3 to >7 °CIPCC 2009

Fig. 15.22

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USGCRP 2009 Climate Assessment

Number of days over 100 degrees F

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Figure 15_25b

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Figure 15_25a

Fig. 15.25a Models predict warmer, wetter winters and drier summers by 2100.Midwestern farm states will have summer climate similar to current summers inLouisiana or Texas. USGRP 2009.

35CS Fig. 15.26

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Change in MinnesotaChange in Minnesota“Recent research indicates a warming trend in Minnesota. A study of the climate record at Fort Snelling shows an increase of 2.9°F in average annual temperature between the 1860s and 1987, almost three times the worldwide average. Analyses of more than a hundred temperature-depth profiles in North America show that ground latitudes comparable to Minnesota’s indicated ground warming of up to 3.6°F.”

From “Playing with Fire, Global Warming in Minnesota” 1999; data from Baker and Skaggs, 1989

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Change in Lake Change in Lake SuperiorSuperior

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MN Biomes at riskMN Biomes at risk

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We have a choiceWe have a choice

http://www.geograph.org.uk/photo/764803

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How optimistic are you?How optimistic are you?

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An economist’s viewAn economist’s view

• Sir Nicholas Stern, former chief economist of the World Bank– “Scientific evidence is overwhelming: climate

change is a serious global threat and demands an urgent global response.”

– Costs of climate change will be 5 to 20% of global GDP

– Reducing greenhouse emissions will cost 1% of global GDP

• $1 spent now could save $20 later in the century

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Scientific consensusScientific consensus

Examining the Scientific Consensus on Climate ChangeEOS, VOLUME 90 NUMBER 3 20 JANUARY 2009

43Somerville and Hassol, Physics Today, Oct. 2011

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The EndThe End

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