Lecture #3 Climate

Studying Climate

• Ice cores - collected from glaciers reveal light and dark bands caused by annual snow accumulation on glacier – Gas bubbles can be analyzed for atmospheric

composition.– Ash and sulfur deposits correlate with volcanic

eruptions.– Vostok ice core gives us a record back 420,000

years.

Climate

• Data show that:– Abrupt climatic change has catastrophic effect on

living things as organisms are unable to adjust before conditions exceed their tolerance limits. Species may become extinct.

– There is a close correlation between carbon dioxide concentration and temperature of the atmosphere.

Climate• What causes climate change?– Sunspot cycles– Solar magnetic cycles– Cycle of shift in angle of moon alters tides and

currents.– Milankovitch Cycles - periodic shifts in Earth’s orbit

and tilt which change distribution and intensity of sunlight• Ice cores show drastic changes may have occurred

over short periods of time (years to decades).– Volcanic eruptions can cool planet suddenly.

Milankovitch Cycles

El Nino/Southern Oscillation• Warm surface water in Pacific Ocean moves back and

forth between Indonesia and South America.– Most years, the pool is held in western Pacific by

steady equatorial trade winds.– Surface waters driven westward by trade winds are

replaced by upwelling of cold, nutrient rich waters off west coast of South America. Nutrients supply food for fisheries.

– Every three-five years the Indonesian low collapses and the mass of warm surface water surges back east and we call this an El Nino.

El Nino/Southern Oscillation

– During an El Nino year, the northern jet stream pulls moist air from the Pacific over the U.S.• Intense storms and heavy rains from California

to the Midwest• During intervening La Nina years, hot, dry

weather is often present.• ENSO events are becoming stronger and more

irregular due to global warming.

El Nino/Southern Oscillation

– High sea surface temperatures cause hurricanes to be more violent.

– Pacific Decadal Oscillation - very large pool of warm water moving back and forth across the North Pacific every 30 years. Affects fishing harvest.

Global Warming is Happening

• Most important environmental issue of our time

• In 2007, the Intergovernmental Panel on Climate Change released its fourth report.– Represents a consensus by more than 90% of all

scientists working on climate– Gives a probability value of 90% that the warming

we are now seeing is caused by humans

Global Warming

• Range of temperature increase predicted to be from 1.1 to 6.4°C (2 to 11.5°F) by 2100 depending on population growth, energy conservation, etc.

• Best estimate is 1.8 to 4°C (3.2 to 7.8°F)– To put that in perspective, there has been a 5

degree C rise since the middle of the last ice age (about 20,000 years ago).

Global Warming• Most people will experience more extreme weather

including droughts, floods, heat waves and hurricanes. These extremes have increased significantly in the last decade.

• In the worst outcome, we could see millions of human deaths.

• Sea levels are projected to rise 17-57 cm (7 to 23 in). If we do nothing, Greenland’s ice will melt and raise sea levels 20 ft.

Global Warming• If Greenland’s ice melts, a great deal of land will be

flooded including:– Most of Florida– Some of the Gulf Coast– Most of Manhattan– Shanghai– Hong Kong– Tokyo

• Bush administration praised the report but said it opposes mandatory cuts in greenhouse gas emissions as too costly.

Sources of Greenhouse Gases

• Carbon Dioxide - fossil-fuel burning• Atmospheric levels increasing steadily• Most important cause of warming

• Methane - ruminants, rice paddies• Absorbs more infrared than CO2 .

• Chlorofluorocarbons (CFC’s) - refrigerants• Declined in developed countries, but now

produced in developing nations.• Nitrous Oxide - burning organic material

Carbon Dioxide Concentrations on Mauna Loa

Sources of Greenhouse Gases• U.S. has less than 5% of world’s population but

produces 28% of carbon dioxide.• China, with 1.3 billion people, is second.• Japan and Europe produce half as much carbon dioxide

per person as the U.S.

So what does this mean for us?