Global Warming• What is it?

• What’s causing it?• What are the solutions?

Greenhouse effect

CO2: one of the main heat-trapping gases.

Its concentration in the atmosphere, past 250 yrs.

Past 10,000 yrs

CO2 concentration: 400,000 yrs--4 ice ages.Read graph from right to left.Recent increase unprecedented, NOT a natural cycle.

Present interglacialperiod

2010, 2005, 1998: tied as hottest years on record.

2001-2010: hottest decade on record.

It’s getting warmer

Global warming is here now!• The number of severe hurricanes has increased by 80% during past 30 yrs.• Droughts in Texas, western states. • Decrease in migratory birds, due to warmer winters in northern states. • Increase in tree mortality, Western U.S. • pH of ocean is dropping due to CO2; affects corals, shellfish.• Range shifts of MANY biological species.• Forest fires are increasing, as predicted.• Prolonged dry spells.• Reduced snowpack. • More rain, more extreme rain.• Polar bear now “endangered.” • Bacterial “blooms” in waters.• ETC!

Glacier National Park,Montana, is melting.

1850: 150 named glaciers.

2007: 26. 2030: 0 expected

S Cascade Glacier, Washington, 1928, 1979, 2003.

Alaska

Austria

Arctic melt extent, 1979 and 2003

Expected to be ice-free in summer by 2030.

Recentlly: Melting has accelerated. “Arctic ice could be in an abrupt, irreversible decline.” Are we approaching a tipping point?

Reflectivity feedback could have serious consequences for Greenland.

Greenland ice is melting

Greenland melt extent

James Hansen, NASA’s chief climatologist, GW expert:

Earth could pass a “tipping point” during next 10 to 20 yrs that would initiate irreversible melting of the Greenland and W Antarctic ice caps, raising sea levels by 50 feet over the next few centuries and “produce a new planet.”

We could see 10-ft rises by the end of this century.

Is this what you want for your

grandchildren?

It’s a moral issue!

What’s causing the warming?When we look at the patterns of global changes (temps, ice, rainfall, etc.) …..

…we find that natural sources cannot explain it, but human-emissions of

greenhouse gases do.

Intergovernmental Panel on Climate Change (IPCC): •“Unequivocal” that climate is warming, •“Very likely” that human activities are major driver.

The cause: mostly fossil fuels

Carbon in atmosphere

IPCC Report: A conservative document

• Spons by U.N. & World Meteorological Org

• ~3000 scientists compile the 6-yr reports

• Based on tens of thousands of peer-reviewed scientific papers published in hundreds of scientific journals

• Results arrived at by consensus

The major U.S. carbon polluters:

Electric Power 41%

3/4 from coal

Transportation 33%

3/4 from cars and trucks

COAL

• 1 plant = 1 million cars

SOLUTIONS:• Energy efficiency & alternative energy sources

• Carbon capture & storage! (~50% price incr)

• Congress could mandate CCS

CARS

• 55 mpg by 2020 (hybrids today)

• Plug-in hybrids, attached to renewable electricity

• Gasoline tax of several $ per gallon

• “Externalities” of driving: $12 per gallon!

• 6 tons of CO2 / yr,

3 X car’s weight!

SOLUTIONS:

The Solutions:

Reduce CO2 emissions: Efficiency (use less) Renewables (solar, wind)

Nuclear powerCarbon capture and storage

More broadly: Preserve, replant forestsLimit population growth

The best choice: Energy efficiency!

Bicycling

Pedestrian zones,pedestrian streets

Light rail for NW Arkansas!

Renewables: Wind

Photovoltaics

Solar-thermal electricity

Active solar heating

Passive (or direct)

solar

Geothermal energyFor electricity: For heating & cooling:

Biofuels

biofuels from grasses…

… and agri waste

From corn today: bad idea! With research:

Also: Nuclear power

• No greenhouse gases !

• Serious drawbacks (proliferation etc.)

• MUCH safer than fossil fuels.

China, India

20 leading climate scientists published a paper in Nature in

Sep 2009:

• Our present 390 ppm atm CO2 concentration is already unsustainable and dangerous.

• We need to move it back to 350 ppm asap, in order to hold the temp increase to 2oC.

James Hansen, NASA’s cilmatologist

Paul CrutzenNobel Prize, Chem.

What’s needed:

• 60% global emissions reduction by 2050.

• Converge on 1.5 tons / person-yr

• India: emits 1 ton / person-yr today

• US: emits 20 tons / person-yr

--must reduce by 90%

• Europe: reduce by 80%.

• But emissions are increasing, not decreasing!

THANK YOU!

ART HOBSONahobson@uark.edu

Website: physics.uark.edu/hobson

We’re all in this together!