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NASA. Global Warming 101. Roy W. Spencer, Ph.D Principal Research Scientist The University of Alabama In Huntsville 19 March 2007. Height . Due to greenhouse effect. Temperature . We are probably not as warm as during Medieval Warm Period.

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global warming 101

Global Warming 101

Roy W. Spencer, Ph.D

Principal Research Scientist

The University of Alabama In Huntsville

19 March 2007



Due to greenhouse effect



We are probably not

as warm as during Medieval Warm Period

The GRIP (Greenland) borehole record is one of the best records because it is not a proxy, it is a DIRECT measure of temperature.  Shown are the last 2000 years. (Dahl-Jensen et al. 1998, Science, 282, 268-271 "Past Temperatures Directly the Greenland Ice Sheet").  A similar reconstruction occurs for the Ural Mountain borehole temperatures (i.e. warmer 1000 years ago, Bemeshko, D., V.A. Schapov, Global and Planetary Change, 2001.


Global Warming Basic Hypothesis:

  • Carbon Dioxide is a greenhouse gas,
  • it is increasing in the atmosphere (at ½ rate of human production),
  • therefore, the lower atmosphere MUST warm

CO2 concentration is now about =>

40% above pre-industrial times.


Most of our atmosphere is being continuously

recycled by precipitation systems, which then

determine the strength of the Greenhouse Effect

Cooling (loss of IR radiation)

by dry air to space


released through


causes air to rise,

rain falls to surface

Air sinks in

response to precipitation systems:

Sinking air is relatively dry

Sunlight absorbed

at surface

Boundary layer

warm, humid air

cool, dry air


removes heat

Ocean or Land

  • Evidence for climate change
  • Predictions of future climates
  • Assessing response of natural ecosystems
  • Future directions

GLOBAL WARMING BASICS: “Radiative Energy Balance” (= const. Temp.)

Incoming Sunlight

Emitted Infrared Radiation


Global average input = output =

≈235 Watts per square meter

=> Greenhouse gases affect Infrared Radiation


“Global Warming”(at least since 1920)is Real…

But how unusual is it?

How much of it is natural versus man-made?

Data source: J. Hansen/ GISS

“Little Ice Age”


Spreading disease

Coral reef bleaching

Heat waves and periods of unusually warm weather

Downpours, heavy snowfalls, and flooding

Glaciers melting

Earlier spring arrival

Plant and animal range shifts and population declines

Sea level rise and coastal flooding

Arctic and Antarctic warming

Droughts and fires

GLOBAL WARMING: Early Warning Signs

Fingerprints and Harbingers

changes in surface temperatures
Changes in surface temperatures

US 20th century

Global 20th century


retreat of glaciers
Retreat of glaciers

Grinnell glacier, 1938

Grinnell glacier, 1981

coral reef bleaching
Coral reef bleaching

Bleaching hot spots in last 15 years

Bleached Goniopora coral, Micronesia

changes in growing season length
Changes in growing season length

Mauna Loa, HI

Thoning and Tans

arctic climate impact assessment acia
Arctic Climate Impact Assessment (ACIA)

Sources: Claire Parkinson and Robert Taylor