LEARNING FROM GLOBAL DISASTER LABORATORIES PART 11A: FUNDAMENTALS OF GLOBAL CLIMATE CHANGE Walter Hays, Global Alliance for Disaster Reduction, Vienna, Virginia, USA Walter Hays, Global Alliance for Disaster Reduction, Vienna, Virginia, USA

FUNDAMENTALS OF GLOBAL CLIMATE CHANGE  WHAT DO WE NOT KNOW FOR CERTAIN?

COULD human activities exacerbate the “unnatural” Greenhouse effect by increasing certain greenhouse gases (e.g., CO2) above normal (i.e., safe) levels; if so, can we do anything to slow or reverse the undesirable trend?

THE ISSUE: HUMAN INFLUENCES  Are humans exacer- bating GLOBAL WARMING by adding too much carbon dioxide to the normal levels of greenhouse gases in the atmosphere through rapidly increasing global use of fossil fuels.

HUMAN INFLUENCES  Aerosols, smoke and sulfates reflect sunlight away from the Earth, which outweigh the temporary, localized cooling effects from aerosols and the smoke and sulfates from industry.

HUMAN INFLUENCES ON LAND SURFACES  Once tropical forests (a carbon sink) are cleared for cattle ranching or community development, the cleared land can becomes a major source of methane, a greenhouse gas.

FUNDAMENTALS OF GLOBAL CLIMATE CHANGE  WHAT DO WE THINK WE KNOW FOR CERTAIN?

THE EARTH’S GREENHOUSE EFFECT OCCURS NATURALLY.

PLANET EARTH (THE BLUE PLANET) AND THE SOLAR INPUT

PHYSICAL INTERACTIONS OCCUR ON MANY DIFFERENT SCALES Propagation, reflection, and refraction of light and EM waves radiated from the sun (i.e., the solar input to Planet Earth)

ABOUT 33 PERCENT OF THE INCOMING SOLAR INPUT IS REFLECTED BACK TO SPACE BY CLOUDS, SNOW, ICE, AND, TO A LESSER DEGREE, BY LAND AND WATER SURFACES.

THE BALANCE (ABOUT 70 PERCENT) OF THE INCOMING SOLAR INPUT IS ABSORBED BY LAND, AIR, WATER, AND ICE.

THE SOLAR SPECTRUM INCLUDES: A) VISIBLE LIGHT (ROYGBIV), ALONG WITH: B) ULTRAVIOLET LIGHT (SHORTER WAVE LENGTHS), AND C) INFRARED LIGHT (LONGER WAVE LENGTHS).

PHYSICAL INTERACTIONS OCCUR ON MANY DIFFERENT SCALES Absorption, storage, and re- radiation of light and EM waves causes the “natural” greenhouse effect).

THE GREENHOUSE EFFECT OCCURS WHEN AN EARTH WARMED BY THE SOLAR SPECTRUM RADIATES INVISIBLE INFRARED LIGHT BACK, BUT…

CONTINUED … INSTEAD OF GOING BACK TO SPACE, IT IS PARTLY ABSORBED BY GREENHOUSE GASES IN THE ATMOSPHERE  NOTE: ABSORPTION MAKES THE ATMOSPHERE WARMER.

GREENHOUSE GASES IN THE ATMOSPHERE  “Greenhouse" gases include water vapor, carbon dioxide, methane and nitrous oxide.

WATER VAPOR  Water vapor is the most potent greenhouse gas  Higher air temperatures increase the rate of water vaporization.

VOLCANIC ERUPTIONS  Volcanic eruptions add water vapor and ash to the atmosphere.

PHYSICAL INTERACTIONS OCCUR ON MANY DIFFERENT SCALES Absorption of heat by greenhouse gases in the atmosphere causes the “unnatural” greenhouse effect).

“UNNATURAL”GREENHOUSE EFFECT  Greenhouse gases trap heat inside the atmosphere.  Too much trapped heat increases temperatures in the atmosphere and on the land and ocean surfaces, which causes climate change.

WHAT DOES IT ALL MEAN? THE “NATURAL” GREENHOUSE EFFECT KEEPS THE EARTH WARM AT ABOUT 57.9 DEGREES F, AND THE “UNNATURAL”GREENHOUSE EFFECT CAUSES THE ATMOSPHERE’S TEMPERATURE TO RISE, FOLLOWED BY A RISE IN LAND AND OCEAN TEMPERATURES, CAUSING CLIMATE CHANGE ON A GLOBAL SCALE

SATELLITE MEASUREMENTS INDICATE THAT THE TROPO- SPHERE IS WARMING FASTER THAN THE EARTH’S SURFACE.  NOTE: THIS INDICATES THAT GREENHOUSE GASES IN THE ATMOSPHERE ARE ABSORBING TOO MUCH HEAT.

HOTTEST YEAR ON RECORD According to NASA and other organizations, 2005 was the hottest year on record for the Northern Hemisphere. Temperatures were about 1.4 degrees Fahrenheit above the historical average.

A WARMING EARTH: SEPT 25, 2007

THE AVERAGE GLOBAL TEMPERATURE HAS RISEN 1.7 DEGREES F IN PAST 150 YEARS

AVERAGE GLOBAL SEA LEVEL HAS INCREASED BY 4.7 INCHES SINCE THE LAST ICE AGE.

SEA LEVEL RISES FOR TWO REASONS:  WATER EXPANDS WHEN IT IS WARMED, AND  WATER VOLUME INCREASES AS MELT WATER IS ADDED.

IF THE FLOATING ARCTIC ICE CAPS MELT, GLOBAL SEA LEVEL WILL NOT BE AFFECTED. IF ALL THE SNOW AND ICE IN GREENLAND MELTED, GLOBAL SEA LEVEL WILL RISE 24 FEET.

CLOUDS CAUSE BOTH COOLING AND WARMING  Clouds cool Earth by reflecting incoming solar energy.  Clouds cool Earth by slowing evaporation.  Clouds warm Earth by trapping heat being re- radiated upward from the Earth’s surface.

LAND SURFACES AFFECT TEMPERATURES AND MOISTURE  Mountain ranges can block clouds, creating "dry" shadows downwind.  Sloping land facilitates water runoff, leaving the land and air drier.

ROLE OF ICE AND SNOW  Ice and snow reflects heat outward into space, cooling Planet Earth in the process.  When ice melts, ocean water looses some of its stored heat.

THE OCEANS ARE A NATURAL CARBON SINK  The oceans and marine life remove and/or consume huge amounts of carbon dioxide.

THE OCEANS STORE HEAT BETTER THAN LAND DOES  Oceans, the source of moisture in the air, store heat more effectively over the long term than land and transports it efficiently over distances of thousands of miles.

THE ALBEDO (PERCENT OF LIGHT REFLECTED) FOR FRESH SNOW IS PERCENT,  BUT IT IS ONLY 50 – 60 PERCENT FOR MELTING ICE.

CARBON DIOXIDE ENTERS THE ATMOSPHERE NATURALLY, AND IT LEAVES THE ATMOSPHERE NATURALLY.

AS THE GREENHOUSE EFFECT INCREASES, TEMPERATURES IN THE ATMOSPHERE INCREASES AND THE REMOVAL RATE OF CARBON DIOXIDE DECREASES.

SUMMARY

WITHOUT THE “NATURAL” GREENHOUSE EFFECT, PLANET EARTH WOULD BE MUCH COLDER; E.G., A TEMPERATURE OF ABOUT MINUS 2 DEGREES F.

IF THE “UNNATURAL” GREENHOUSE EFFECT WERE TO GET OUT OF CONTROL, PLANET EARTH WOULD BE WARMER THAN THE CURRENT AVERAGE TEMPERATURE OF 57.9 DEGREES F.

THE WORLD IS DEBATING THE TIPPING SCENARIO ISSUE The “Tipping Scenario Issue” is: “Within a few decades, will humans be virtually helpless to slow the perceived risks associated with global climate change?