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

ght

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

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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