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NASA
Global Warming 101
Roy W. Spencer, Ph.D
Principal Research ScientistThe University of Alabama In Huntsville
19 March 2007
Temperature
Due to greenhouse effect
Hei
gh
t
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.
We are probably not as warm as during
Medieval Warm Period
1. Carbon Dioxide is a greenhouse gas,2. it is increasing in the atmosphere (at ½ rate of human production),
3. therefore, the lower atmosphere MUST warm
Global Warming Basic Hypothesis:
CO2 concentration is now about =>40% above pre-industrial times.
Boundary layer
Cooling (loss of IR radiation)by dry air to space
warm, humid air cool, dry airevaporationremoves heat
Air sinks inresponse to precipitation systems:
Sinking air is relatively dry
Ocean or Land
Heat released throughcondensationcauses air to rise,rain falls to surface
Most of our atmosphere is being continuouslyrecycled by precipitation systems, which thendetermine the strength of the Greenhouse Effect
Sunlight absorbed at surface
Outline
• Evidence for climate change
• Predictions of future climates
• Assessing response of natural ecosystems
• Future directions
Incoming Sunlight Emitted Infrared Radiation =
GLOBAL WARMING BASICS: “Radiative Energy Balance” (= const. Temp.)
=> Greenhouse gases affect Infrared Radiation
Global average input = output =≈235 Watts per square meter
“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”
Niagara Falls NY - 1911
GLOBAL WARMING: Early Warning SignsGLOBAL WARMING: Early Warning Signs
http://www.climatehotmap.org/
Fingerprints and Harbingers
Heat waves and periods of unusually warm weather
Sea level rise and coastal flooding
Glaciers melting
Arctic and Antarctic warming
Spreading disease
Earlier spring arrival
Plant and animal range shifts and population declines
Coral reef bleaching
Downpours, heavy snowfalls, and flooding
Droughts and fires
Changes in surface
temperatures
Global 20th century
US 20th century
°F
A 1000-year record of temperatures
Borehole temperatures
Retreat of glaciers
Grinnell glacier, 1938 Grinnell glacier, 1981
Retreat of glaciers
Sea ice extent and mass
Coral reef bleaching
Bleaching hot spots in last 15 years
Bleached Goniopora coral, Micronesia
Rising sea levels
Rising sea levels
Rising sea levels
Insect pests and disease
Changes in growing season length
Mauna Loa, HIThoning and Tans
Changes in US precipitation regimes
20th c.
%
Arctic Climate Impact Assessment (ACIA)
Sources: Claire Parkinson and Robert Taylor
Greenland Mass Loss – From Gravity Satellite
Responsibility for CO2 Emissions and Climate Change