each change, sundry species have benefited
and flourished, others adapted, faltered, or
died
surface air temperature a half degree celsius
during this century. If the trend continues, it
could alter climate patterns worlwide
global climate depends on combinations
of factors interacting in subtle and
complex ways that we do not yet fully
understand
THE GREENHOUSE EFFECT
without our atmosphere, global
temperature would be about minus 18°c
the atmosphere, only a fraction of that heat
makes it directly back into space
the rest trapped in the lower air
layers, wich contain a number of
gases
that absorb the outgoing infrared radiation. gases
heat up warmth radiates back down to the surface
caused by the predominant greenhouse gas, water vapor
the hotter it gets, the higher the water vapor content of
the air, and the greater the greenhouse warming
MODELS AND UNCERTAINTY
to project future climate patterns, scientists use computer
simulations of the interactions among land, air, water, ice and
sunlight
equations representing the know laws of atmospheric
physics and ocean circulation
they can provide only a range of projected temperature change
the warming could be one degree c over the next century, or it
could be as much as three times greater than that
A CASE OF MISSING CARBON
human activity releases approximately
7 billion metric tons of carbon
every year adding to the 750 billion tons that is already there
3 billion tons remain in the air, the rest is taken
up by terrestrial and marine plants
the ocean remove at least 2 billion tons from
the atmosphere each year
the role of clouds and airbone suspended particles called aerosols
clouds shade earth´s surface promoting cooling, depending on
their altitude, density and other conditions
also they trap outgoing heat, promoting warming
AS THE WORLD WARMS
warming of the magnitude could also prompt
widespread calamity, more water vapor in the air
causing more rainfall worldwide and
probably more intense weather
generally
precipitation in any given event will be greater,
increased precipitation would be extremely uneven
heat waves may become more seriousght
if the land has less chance to cool overni
ANTICIPATING THE FUTURE
a conference in kyoto, japan, in wich the industralized
nations agreed in priciple to cut their emmisions of
greenhouse gases
some argue that hasty measures are pointless
if all greenhouse gas emmisions stopped
tomorrow, the planet almost vertainly would
continue to warm for several decades because of
the gases
WHAT DRIVES CLIMATE CHANGE
weather is what happens outside your home
this morning. climate is what you can expect
to happen outside
SOLAR INPUT
solar energy hits the upper atmosphere at about the
intensity of three 100-watt bulbs per square yard-
one third of wich is reflected back into space
the rest of the energy warms
earth and fuels its weather
engine
THE ATMOSPHERE
absorb heat energy then re-radiate a portion
of it back to the surface
THE OCEANS
covering 70 percent of earth´s surface,
oceans are the chief source of water vapor in
the air
THE WATER CYCLE
higher air temperatures can mean increased
water evaporation and the melting of sea and
land ice
CLOUDS
the role of clouds is poorly understood, but they
are know to both cool earth by reflecting solar
energy and warm earth by trapping heat being
radiated up from the surface
ICE AND SNOW
bright white expanses of ice and snow reflect sunlight
back into space, cooling the planet
LAND SURFACE
when solar energy penetrates the land surface it is
converted into heat, most of which radiates upwards quickly
HUMAN INFLUENCES
adding to the mix of greenhouse gases naturally present in
the atmosphere, human activities magnify warming effects