Samayaluca Dune Field, south of Juarez, Chihuahua Global Climate Change

Weather Related Hazards 1. Drought 2. Desertification 3. Heat waves 4. Snow and Ice 5. Hurricanes 6. El Niño

Climate System: 5 parts Cryosphere (ice) Oceans Lithosphere Sun and internal earth heating Atmosphere

Cryosphere: ICE Ice reflects solar energy Melting ice increases ocean volume Sea level was 130 m (425 feet) lower during last ice age (18,000 years ago)

Albedo is reflectance of land Earth reflects about 30% of incident solar energy.

Ocean influences climate Transfers of heat from tropics to polar regions (i.e., Gulf Stream)

What causes sea level rise? Melting ice Hotter oceans have larger volume

Barrier Islands Sea Level Rise

1 meter rise2 meter rise 4 meter rise8 meter rise

Sea-Level Rise

Lithosphere Mountains influence weather Continents influence ocean currents Volcanism –Warms by adding greenhouse gases –Cools when ash blocks sunlight

Solar energy input to Earth’s surface is 342 W/m 2. Heat flowing out of Earth’s deep interior is only 0.06 W/m 2.

The Greenhouse Effect Without some natural greenhouse effect, Earth would be uninhabitable, average temperature below freezing

Earth Temperature Normal: 14 o C (57 o F) Without greenhouse gases : -19 o C (-2 o F)

Climate System Atmosphere –Nitrogen N 2 78% –Oxygen O 2 21% –Argon Ar 0.93% –Carbon dioxide CO % –Other minor gases 0.035%

Greenhouse Gases CO 2, H 2 0 and methane (CH 4 ): Absorb and re-radiate radiation Insulates and raises Earth temperature

GEOLOGIC RESERVOIRS Fossil organic carbon Fossil organic carbon Rock carbonates Rock carbonates Fossil- fuel burning (5.3 Gt/yr) Fossil- fuel burning (5.3 Gt/yr) OCEAN Cement production (0.1 Gt/yr) Land-use change: deforestation, agriculture (1.7 Gt/yr) Land uptake By new plant growth (1.9 Gt/yr) Ocean uptake by air-sea gas exchange (1.9 Gt/yr) Terrestrial biosphere LAND ATMOSPHERE The influence of Carbon on climate change

GEOLOGIC RESERVOIRS Fossil organic carbon Fossil organic carbon Rock carbonates Rock carbonates Fossil- fuel burning (5.3 Gt/yr) Fossil- fuel burning (5.3 Gt/yr) OCEAN Cement production (0.1 Gt/yr) Land-use change: deforestation, agriculture (1.7 Gt/yr) Land uptake By new plant growth (1.9 Gt/yr) Ocean uptake by air-sea gas exchange (1.9 Gt/yr) Terrestrial biosphere LAND ATMOSPHERE Human activities release a total of 7.1 Gt of carbon into the atmosphere each year. New plant growth and air-sea gas exchange remove 3.8 Gt/yr,… …yielding a net atmospheric increase of 3.3 Gt/yr.

Climate Change Understanding Natural Climate Variability: Use the geologic record to understand Earth Climate in the past (Uniformitarianism)

Milankovitch cycles Related to variations in: 1. Eccentricity 2. Tilt of axis 3. Precession (wobble)

All of these variables change the earth-sun distance

Is Human-induced climate change possible?

Long-term change can be assessed from ice cores, which record annual cycles of ice formation from snow.

Temperature relative to present climate (°C) Thousands of years before present Relative carbon dioxide and methane concentrations High Low Key: Temperature CO 2 Methane Ice Ages Deglaciation Climate has been relatively warm and stable during the last 10,000 years.

Years Temperature CO 2 concentration The 20th-century is clearly anomalous when compared with the last millennium. Northern Hemisphere temperature anomaly (°C) CO 2 concentration (ppm)

Keeling Curve

Years Temperature CO 2 concentration Global temperature anomaly (°C) A recent warming trend correlates with the increase in CO 2. CO 2 concentration (ppm)

Atmospheric CO 2 Projections Under 3 Alternate Scenarios… Year

….and Estimated Average Surface Temperatures for Those Scenarios Uncertainty envelope due to lack of knowledge of climate system

Feedback enhances warming Positive Feedback: –Amplifies changes in the system. –Temperature increase decreases Earth’s albedo by reducing snow and ice cover

Evidence for Warming Weather is highly variable* Glaciers provide long-term trends

1941

2004

Columbia glacier

Greenland

Weather Related Hazards 1. Drought 2. Desertification 3. Heat waves 4. Snow and Ice 5. Global Warming 6. El Niño

Transition zones between deserts and humid areas are fragile

Soil gets eroded by wind and water Productive land becomes degraded

Human activity can stress the ecosystem Grazing Cutting trees for charcoal Some agriculture

El Niño Pacific Ocean is pushed westward by trade winds Warm water off Peru is replaced by upwelling of cold, deep, nutrient-rich water Circulation reverses: El Niño 6 Year cycle Opposite extreme in weather patterns is La Nina

El Niño Subtropical trade winds weaken Warm surface water remains in east Pacific Incessant rain to west coasts Fisheries suffer (no cold, nutrient-rich upwelling water)

El Nino