Climate Change

2

Global carbon cycle (billion metric tons)

3

Global carbon dioxide emissions and concentration

Historical and Projected Climate Change

•90% chance of temperature rise in the shaded blue area.

•10% chance in the dark blue area.

Source: CBO, Potential Impacts…, May 2009.

5

CO2 content by fuel (1 million Btu)

• 99 lbs coal (anthracite)> 227 lbs CO2• 8 gallons gasoline> 156 lbs CO2• 7.2 gallons diesel> 161 lbs CO2• 971 cubic feet natural gas: > 117 lbs CO2

Greenhouse gas

• Very different from conventional air pollution problems

Conventional air pollution• SO2

– Pollution impacts increased linearly when pollution increased

– Pollution concentrations fell fairly quickly when emissions were reduced

– Time frame a decade or less– Negative impacts could be reversed by cutting pollution– Good estimate of benefits and costs (if too low initially)– Costs and benefits affected the same generation

Climate Change• Greenhouse gas (GHG)

– Pollution impacts may rise nonlinearly with increasing GHG concentrations; thresholds may exist

– Pollution concentrations will fall only very slowly when emissions are reduced

– Time frame several decades if not 100 years– Negative impacts may produce irreversible damages– Estimates of benefits and costs are uncertain– Costs and benefits will affect different generations

Potential Impacts of Climate Change

• Link between emissions and climate• Impacts on:

– Physical environment– Biological systems– Human health– Economy

Potential Impacts of Climate Change

• Impacts on:– Physical environment

• Temperature– Warm areas get warmer– Patterns in the U.S. shift north

• Precipitation– Dry areas get drier– North gets wetter

• Sea Level– Inundation of some coastal areas, more frequent 100 yr floods

– Biological systems• Slower to adapt• Extinction for some species

Average Temperatures

Illustration of Changes in Averages and Extremes in

Temperature and Precipitation

Potential Impacts of Climate Change

• Impacts on:– Human health

• More insect-borne diseases• More warm-weather deaths• More ozone events• Fewer cold-weather deaths

Potential Impacts of Climate Change

• Impacts on:– Economy

• Longer growing season, farmers could benefit (if water available)

• West and Southwest will experience even more severe water scarcity (less snow pack, precipitation)

• Less spending for heating, more for cooling• More spending for flood control along coastlines• Aggregate impacts modest, GDP will be 3% lower by

2100.

Uncertainty Reigns• Linkages:

– Emissions>Concentration>Warming>PhysicaI impacts>Economic impacts

• Linkages subject to very large uncertainty• Possible:

– Nonlinearities– Irreversibilities

Emissions and Climate

• Ongoing emissions will continue to raise atmospheric concentrations and temperatures indefinitely.

• Even if emissions were cut dramatically today, average global temperature would continue to rise.

What temperature to expect?• Uncertainties make establishing a range difficult.• 20th Century, planet warmed 0.70 C relative to the

Industrial Revolution• Warming is accelerating: up 0.20 C in each of the past

three decades.• Stern Review: GHG concentrations could triple that

of pre-industrial levels by end of century.• If this occurs, 50:50 chance of 5.00 C rise above pre-

industrial level by end of 21st century.

CO2 Emissions Are Lower

Electricity: coal lower; wind, hydro, and natural gas higher

Market-based Policy Options

• A tax on GHG emissions• A cap-and-trade system (HR 2454)