Climatology and Atmospheric Layers

Troposphere

• Weather happens here
• Location: surface to about 10 km
• Composition: unpolluted air; Nitrogen (78%), Oxygen (21%), Remaining 1% is CO2 (0.0365%), H, He, Ar
• Water vapor is .01% to 5%

Stratosphere

• Location: above troposphere, about 10 to 50 km
• Very thin air; virtually no weather, and no turbulence
• Similar composition to troposphere, except:
• Water vapor is 1000 x less
• Ozone is 1000 x greater

Atmospheric Pressure and Temperature

• Pressure and temperature decrease with increasing altitude
• The graph displays how pressure, temperature and altitude relate.
• Note the location of the tropopause and stratopause

Climate vs Weather

• Climate = long-term atmospheric conditions
• Weather = short-term atmospheric conditions
• Both are dynamic and change over time

CO2 Measurements

• Graph shows CO2 levels rising over time (1960-2000)

Evidence for Climate Change

• 20th century was the warmest in the past 1000 years
• Global temperatures have risen 0.6°C (1.1°F) since 1861
• 16 warmest years recorded since 1980, 10 warmest since 1990
• Glaciers and sea ice are melting
• Sea level has risen 100-200 cm over the 20th century

Projecting Future Changes

• Real experiments aren't possible for the entire Earth's climate
• Use scaled-up small experiments
• Computer models (GCMs)
• Learn from the past (paleoclimatology)

Sea Level Rise

• There is a graph showing sea level rise over time
• The graph also shows different scenarios for sea level rise by the year 2100

Solutions to Climate Change

• Do more research (wait and see) - current US strategy
• Act now to reduce risks because of global warming impacts (severe)
• Act now in the same way to reduce global warming risks, regardless of whether warming occurs
• Prevention strategies and cleanup strategies detailed

Removing CO₂ from the Atmosphere

• Methods for removing CO2 from the atmosphere are described.

Reducing Greenhouse Gas Emissions

• 1988 - IPCC established (Intergovernmental Panel on Climate Change)
• 1997 - Kyoto Protocol reached
• Agreement to reduce CO2 emissions from 39 countries
• US pulled out of the agreement in 2001
• Russia's ratification was needed for the Protocol to take effect;
• New post-Kyoto treaty?

Ozone in the Stratosphere

• Ozone (O₂) protects life on Earth from harmful UV solar radiation
• Ozone depletion causes the ozone "hole"

CFCs

• Chlorofluorocarbons (CFCs) and related chemicals break down ozone in the stratosphere
• Used in many applications, now mostly phased out

Seasonal Ozone Layer Thinning

• Graph showing seasonal thinning of ozone layers

Loss of the Ozone Layer: Reasons for Concern

• Increased incidence of sunburn, eye cataracts, skin cancer
• Immune system suppression
• Increase in acid deposition
• Lower crop yields and reduced productivity

Solutions: Protecting the Ozone Layer

• CFC substitutes
• Montreal Protocol (1987)
• Copenhagen Protocol (1992)

Future Climate Predictions

• Global average temperature and sea level will likely rise based on IPCC scenarios
• Temperature increases between 1.4 and 5.8 °C from 1990–2100
• Snow and ice cover will decline (exceptions noted), with Greenland losing ice compared to Antarctica gaining
• Sea-level rise anticipated
• Change will potentially persist for centuries