Global Climate Change for Beginners Robert K. Kaufmann July 7,

Surface Temperature

Climate vs. Weather Weather: Conditions on any given day Temperature in Boston today is 91 o F Climate: Average conditions on any given day over The average temperature in Richmond on July 7, is 83 o F

15,000 Years of Temperature

1000 Years of Temperature

Instrumental Temperature Record

Heat Balance of Planet Earth

Changes in Out-Going Radiation

Radiative Forcing of Sulfur Emissions Direct Effect

The Heat Balance of Planet Earth Ground SO x

The Heat Balance of Planet Earth Ground SO x Clouds

The Vostok Record From: Petit et al., Nature 399, (1999

How Do Humans Affect Radiative Forcing?

Burning Fossil Fuels

Changing Land-Use Deforestation Chopping down trees releases carbon dioxide Increasing termite habitat methane emissions Agriculture Rice paddies--human swamps emit methane Livestock--Methane ‘burps’

Human Sources of Carbon Dioxide Fossil Fuel Deforestation

Humans are Not the Largest Source of Carbon Dioxide

The Global Carbon Cycle

Atmospheric Concentrations

Detection: Is Climate Changing?

Earlier Springs, Later Autumns

Rising Sea Levels

Attribution: Are Humans Responsible for Climate Change?

Model Results

Statistical Analysis of Historical Data

How Much Doubt Really Exists? “If rising carbon dioxide is the cause of rising temperatures, why didn’t it cause temperatures to rise from 1940 to 1970? “Trust me, the satellite data have been reanalyzed dozens of times,…they show much less warming than expected by theory

Solar Activity is to Blame

Solar Activity Solar Activity watts/m 2 (Lean et al., 1995),

No Relationship Between Carbon Dioxide and Temperature

Remember Sulfur Aerosols!

Climate Models: How, Where, and By How Much Will Climate Change?

Causes For Temperature Change Doubling of radiative forcing……………1.2 o C Increased water vapor………..……….1.6 o C Increase in clouds………………………..0.8 o C Changes in surface albedo……………….0.4 o C Other changes……………………………0.2 o C Total change in temperature…………….4.2 o C

Climate change impacts on the environment & economy Change in sea level Impact on agriculture Impact on biomes Water Supply

Changes in Sea Level Melting of glaciers and polar ice Thermal expansion of water

Florida 11.8 Thousand Years Ago

Florida 5 Meter Sea Level Rise

Florida 50 Meter Sea Level Rise

Impacts on Agriculture BenefitsCosts Longer growing season CO 2 Fertilization Mid Continent Drying Warmer nights Water use efficiency

Can Biomes Migrate in Time?

Climate Change & Extinction & Extinction Thomas et al, 2004 Nature 427: Migration rateMinimumMiddleHigh Universal dispersal No dispersal Climate change scenario

By How Much Should Carbon Emissions Be Reduced? What does society “give up” What does society gain?

Command & Control Benefits Politicians can measure their effects Invisible taxes Reductions known Costs May not be least cost No incentive for further reductions No incentive for technical development Cumbersome

Carbon Taxes Tax reflects the marginal damage of carbon emissions Higher cost reduces emissions Replace energy use with capital or labor Replace high carbon fuels with low carbon fuels Tax rate based on carbon content of fuel ($100 ton) Gasoline ($1.00 per gallon) $2.80 per gallon Natural gas ($6.00 per tcf) $12.91 per tcf Coal ($100 per ton) $55 per ton Electricity ($0.11 per Kwh) $0.11 per Kwh

Carbon Taxes Advantages Least cost reduction Cost is well known Constant incentive to reduce emissions Constant incentive to improve technology Easy to implement Disadvantages Reductions are not well known Taxes Kiss of death

Tradable Permits Advantages Reductions well known Least cost reduction Constant incentive to reduce emissions Constant incentive to improve technology Proven to work well (US sulfur market) Disadvantages Cost of permit unknown Strong institutions Good governance

Carbon Offsets Commercial providers Boston-Nashville round trip 2,043 miles Emissions 1,009 pounds carbon $9.95 in Offsets Offsets reduce emissions elsewhere