global issues global warming epa site covers most of the global climate change ozone depletion

Global Issues

Global WarmingEPA Site covers most of the global climate change

Ozone Depletion

The Atmosphere• Four distinct zones

– Temperature– Relative gas concentrations– Pressure

• Troposphere: 75% of total mass– 5 to 10 miles– What happens to temperature?

• Stratosphere: to about 31 miles– Low water vapor; ozone 1000x higher than troposphere– What is source and importance of ozone?– Ionosphere

Solar Radiation

• How much reaches the earth’s surface?

• Selective absorption in the atmosphere– Visible light– Ultraviolet– Infrared

• Albedo– Snow vs. a dark surface– Average earth’s is 5% (due to oceans)

Earth’s Radiation

• All energy absorbed by surface is reradiated

• But… how is this different than incoming?

• Reradiated as infrared vs. incoming visible light

• So What? What gasses absorb infrared?

Climate and Climatic Catastrophes

• Climate vs. weather• Gradual climatic change: adaptation, evolution• Abrupt climatic change: mass extinctions

– 65 million years ago (end of Cretaceous)

– Up to dozen such great climatic changes

• What is the evidence of past climatic changes?• Developing models for future changes

Some Numbers - Temperatures

Global temperature increase, 1750-1990: 1.25° F or about 0.8 degrees C

Rate of temperature increase since 1990: 0.72° F or 0.5 degrees C.

IPCC's estimate of global temperature increase by 2100: 2.5° F - 10.4° F

Temperature increase in the Arctic since 1970: 4° F

Average temperature on Earth, with moderate greenhouse effect: 59° F

Some Numbers - Carbon Quantity of CO2 in the atmosphere before the industrial

revolution: 288 parts per million

Quantity of CO2 in the atmosphere in 2000: 370 parts per millionYears since Earth's CO2 level was last this high: 20 millionAnnual increase of CO2 in the atmosphere: 1.5 parts per

% of the enhanced greenhouse effect caused by CO2 52.5%% of the enhanced greenhouse effect caused by methane: 17.3%% of the enhanced greenhouse effect caused by ozone: 12.5%

Some Numbers -

Global temperature increase, 1750-1990: 1.25° F or about 0.8 degrees C, most in the last 40 years

Rate of temperature increase since 1990: 0.72° F or 0.5 degrees C.

IPCC's estimate of global temperature increase by 2100: 2.5° F - 10.4° F (1.4-5.8 deg C)

Temperature increase in the Arctic since 1970: 4° F

Data source: IPCC report (over 2000 leading climatologists)– and, US National Academy of Sciences

Videos with some data NOAA data and graphs

Carbon Dioxide Concentrations

• Annual increase of 0.5%

• Twice pre-industrial concentrations by 2100

• What are the sources?

Other Greenhouse Gasses

• Methane– Absorbs 20x to 30x as much heat as CO2

– Accumulating 2x as fast as CO2

– Ruminant animals, coal mines, pipeline leaks, landfills

• Chlorofluorocarbons (CFCs)

Effects of Climatic Change

• Temperatures– Middle and high latitudes much indrease

• Precipitation– High latitudes wetter– Mid latitudes drier

• Rising sea levels (appear to be increasing 2mm/year)

• Continental glaciers may melt - coastlines inundated

Can CO2 Emissions be Reduced?

• Earth Summit-1992-Industrialized nations reduce to 1990 emissions by 2000

• Kyoto Protocol - 1997: industrialized nations – Average 5.2% below 1990 by 2012– How to enforce? No penalties

• U.S.: Wants to trade emission quotas– Forest replanting would equate to emission

controls

Can CO2 Emissions be Reduced?

• Kyoto Protocol - 1997: industrialized nations – Average 5.2% below 1990 by 2012– Has this been ratified?– What was U.S. opposition– How to enforce? No penalties

• IPCC Report: summary of the report

Can CO2 Emissions be Reduced?

• IPCC Report: summary of the report

• Cap and Trade –( trading emission allowances)

Critical Thinking - What To Do?

• How certain should we be before acting?• What are the potential economic consequences (of

taking or not taking action)?• Should developing countries be forced to remain

at or near current levels?• Are there potential positives if we cut emissions

even if the models are overly pessimistic?• What will happen if we don’t act?

El Nino

• La Nina- Trade winds move ocean surface currents westward– Thermocline

– Upwelling of waters west of S.A.

• El Nino– Indonesian Low Collapses; warm water moves east

– Jet stream drawn south- moist air drawn from Gulf and Pacific

– Are El Nino years becoming more frequent?

Ozone Depletion

• First detected “ozone hole” over Antarctica in 1985

• 1997: all ozone over Antarctica between 14 and 20 km destroyed

• Danger: more UV rays – 1% decrease in ozone results in 2% increase in

UV equals 1 million more skin cancers

Why is Ozone Being Depleted

• Antarctica - unique weather conditions

• CFC - Freon- a great refrigerant - Why?

• Propellants in aerosols - A What??

• No longer propellants

• Helsinki Agreement (1989) - phasing out of all uses of CFC’s