Download The Oceans and Global Warming

Climate Change: Present and Future
Hurricanes & Tornadoes
Some of chapters 19, 20 & 21
Pete Kozich
Climate Change Factors
• Extraterrestrial factors:
Solar output, Earth-Sun geometry,
Interstellar dust… focus on these first
• Intra-Earth System factors:
Atmospheric reflectivity (aerosols, clouds, and
precipitation) Surface reflectivity, Continental
drift, Atmospheric chemistry, Volcanic
emissions, Atmosphere-Ocean heat
exchange, Mountain building
Climate Change
…already covered the extraterrestrial
factors
Climate change
• Intra-Earth System factors:
Atmospheric reflectivity (aerosols, clouds, and
precipitation) Surface reflectivity, Continental
drift, Atmospheric chemistry, Volcanic emissions,
Atmosphere-Ocean heat exchange, Mountain
building
• Already covered the boldface
• That leaves: Atmospheric reflectivity (aerosols,
clouds, and precipitation) Surface reflectivity, and
Atmospheric chemistry
Climate Change
• Surface reflectivity (surface albedo).
Increased albedo would lead to less surface
warming, with more sunlight reflected into
space. How does one increase surface albedo:
more ice & snow, less oceans, more deserts.
• Atmospheric chemistry. N2, 02, and Ar do little
to climate. H20, C02, and CH4 are important
greenhouse gases. S04 helps facilitate
condensation and ends up reflecting lots of
incoming sunlight, and so would cool the
surface of the earth.
Some
estimates of
major
factors
involved in
climate
change
Climate Change
• Atmospheric reflectivity (aerosols, clouds, and
precipitation).
This is the great unknown, and probably has even
greater impacts than greenhouse gases. Clouds
comprise about 2/3 of Earth’s albedo, which clouds
affecting radiation transfer depending on their level
and thickness. Precipitation nuclei affect heating
profiles and change cloud reflection properties.
Precipitation also is important in latent heat release
and surface properties of the Earth. It gets very
confusing and extremely complex very quickly. The
roles of water vapor are extremely complex in the
atmosphere.
Climate
• Clouds at upper levels tend to emit little energy
and allow a lot of sunlight through.
Increase surface temp
Clouds at lower levels tend to emit a lot of energy
but not allow much sunlight through.
Decrease surface temp
Clouds that are thicker and have more cloud
condensation nuclei reflect more. Also, how long
clouds last will affect temperatures.
Sunspot cycles
• Shorter sunspot cycles (~10 years), more active
sun and greater solar output. Last several
decades.
• Longer period cycles (~12 years), less solar output
(textbook has great picture of temperature and
sunspot period). No sunspots during Little Ice
Age.
• Is this as large of an effect or larger than
greenhouse gases? Possibly, possibly not. We
don’t know.
What to conclude
• We are not certain what has caused global
warming the past few decades.
• Greenhouse gases do seem at least partially
responsible for it. The sun is probably also at
least partially responsible. Global warming is also
occurring on Mars, though.
• Most global warming research has ignored the
sun, Earth’s primary energy source. Our society
has become too greenhouse gas obsessive. This
will obsession will probably decrease a bit in the
future, as I would guess we’ll all figure out that
greenhouse gases are not the whole story.
Remember
• Don’t forget about the oceans, cloud changes,
and changes in solar radiation in addition to
greenhouse gas concentrations. All four play very
large factors in our climate for time scales
pertinent to our lifetimes. Vegetation changes
may also be significant.
• We will probably know a great deal more than we
do in 20 years. If the temperature trends shoot
upward the next 20 years, as they did from 19802000, then we indeed have trouble and will need
to address global warming more fully than we do
now.
Hurricanes
• We do not know how climate change will
effect hurricanes. Best predictions to date:
near same or decrease in overall number, with
the very strongest possibly becoming slightly
stronger if global warming continues.
• We do not a lot more about formation,
structure, and intensity of hurricanes than
how they would change if the future climate
changes appreciably.
Hurricanes
• Formation. Necessary but not sufficient
conditions…
-Disturbance of low pressure. Tropical wave, ITCZ
rollup, monsoon trough, stalled frontal boundary,
MCS, midlatitude cyclone
-Low level cyclonic vorticity (spin)
-Moist low and mid levels.
-Vertical instability.
-Planetary vorticity (not on equator)
-Lack of vertical wind shear, with diffluent pattern
aloft.
-Sufficiently warm ocean temperatures.
Hurricanes
• Eye formation.
Heating from deep clouds in tropical storm help
contract the wind field and change the vertical
wind fields and structure as well. Eventually, the
deep clouds will cause sinking motion over the
middle of the storm. When that sinking motion is
great enough, it will dissipate the clouds, making
an eye, and some of that air will be ingested in
the deep clouds surrounding the eye (the
eyewall). The eyewall will intensify until it
reaches equilibrium with the maximum intensity
limits set on by its surrounding environment.
Devonian
oxygen
increasing
Tornadoes
• Storms with a persistent, rotating updraft
(supercells) can have strong vertical winds.
Evaporatively cooled air associated with falling
precipitation may meet air ahead of it that is
warm and rising. Interaction with the
thunderstorm updraft (typically spinning
cyclonically) may help create a violent,
rotating column of wind in contact with the
ground (a tornado).