Human Influence on Weather

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Transcript Human Influence on Weather

Human Influence on
Chapter 18 material
Well-Accepted Ideas (IPCC)
– Human activites causing a rapid
rise in atmospheric CO2
 Fossil fuel burning
 Destruction of forests
– Human activities have destroyed a
amount of stratospheric ozone
– Higher global temperatures have
correlated with increasing CO2
Land Use Changes
 Dust Bowl
– Prairie grass was plowed under and
– With no grass to hold the soil in place, a
naturally occurring prolonged dry spell
(drought) caused the bare soil to be carried
away by the wind
 Owens Lake
Urban Heat Island effect
– Cities are warmer, on average, than their
 Urban Heat Island
 Increased emission of heat (cars, people)
 Changes in water cycling
 Changes in surface area and
heat capacity
The Urban Heat Island: The
Ultimate Land Use Change
 Localized climate
– Increased runoff =
warmer daytimes
(less cooling due to
– Increased surface
area = more solar
radiation can be
absorbed, more IR
emitted and reabsorbed at night
– Autos, factories,
people = heat
Stratospheric Ozone
– Ozone is good or bad, depending upon where it is
 Good: In the stratosphere, where it protects us from
much of the sun’s harmful ultraviolet radiation, which
causes skin cancer
 Bad: In the troposphere, where we are - it is toxic to
plants, animals and us
‘Ozone Hole’
– CFCs (chlorofluorocarbons)
destroy ozone very
efficiently, used in many
things in 20th century
– Ozone “hole” is an area over
the south pole where
stratospheric ozone levels
have drastically fallen
– Atmospheric conditions
(extreme cold,
polar vortex) lead to efficient
ozone destruction there
An international environmental
 Have been banned and atmospheric
CFC levels are leveling off (1987)
 As atmospheric CFC levels decline,
stratospheric ozone should recover, but
there is a significant delay between
CFC reduction and ozone recovery
Global Warming: The
Enhanced Greenhouse Effect
 Greenhouse Effect keeps our planet about
60F warmer than it otherwise would be. Life
as we know it depends upon this effect.
Greenhouse gases (primarily water vapor and
carbon dioxide) absorb/re-emit IR radiation.
Enhanced Greenhouse Effect
 “Global Warming”
– Too much of a “good” thing
– Anthropogenic (human-induced)
 CO2
 Methane
 CFCs – low concentrations, but very efficient IR
absorbers (replacements of CFCs also very efficient
IR absorbers)
 So the earth is warming on average…what
does that mean?
Global Warming: Uncertainties
 Cloud cover: Should increase as condensation nuclei
(pollution) increase, but type of cloud has an effect on
surface temperature. Some cause cooling, some cause
warming. Which type will increase more??
 Sea Level changes: Expected to rise as snow/ice melts,
and is happening now, but some regions will see increased
snowfall if planet warms, offsetting some, if not all, of the
sea level rise
 Ocean Currents: Infusion of fresh water alters density,
disrupts currents
Global Response?
 Climate change: Gradual or Rapid?
 Political Forces
– Will countries play by the rules after ratifying a treaty?
– Should developed countries curtail their emissions and
let developing nations continue until their emissions
become “substantial?”
– Should developing nations be denied the chance the
U.S. and other developed nations had?
 No, it’s only fair. We can’t stifle their development
 Yes, we know more today about what we’re doing to the planet
– Then, should developed nations cover the increased cost developing
nations will incur to meet stricter environmental guidelines? After all, we
screwed it up in the first place.
What do ya’ll think?
 Is this just liberal fear-mongering BS?
 Something you’re concerned about?
 Something you’re willing to sacrifice for to
deal with? (higher energy prices, etc.)