Transcript natural climate schangex

CLIMATE
CHANGE
World Meteorological Organization
Age 10-14
What is climate
variability ?
“Climate variability” refers to
changes in climate from
one year to another.
It can be caused by
changes in ocean
conditions far away, which
can affect climate all over
the world (for ex: el Niño)
Climate variability is natural and occurs on a
regular basis.
What is climate change ?
Climate change is the change in
climate over a time period from
10 to 100s of years.
Climate change involves
both natural changes and
changes caused by people.
Why does our climate
change?
• Over the history of the
Planet, the climate has
changed naturally. It
happened during the ice
ages, and maybe also
when the dinosaurs
disappeared.
• In addition, human
activities have warmed
the climate.
I. The Earth's Climate has changed
many times, due to natural causes.
**There have been at least 4 Ice Ages in the last 3 million years
- with only a 5 degree Celsius cooler difference!
Climatic Change associated with Feedback
Mechanisms
• Positive Feedback Mechanisms – A process whereby an initial change in
an atmospheric process will tend to reinforce the overall effect.
– Water vapor-greenhouse effect
• Increase in water vapor content will lead to warmer temperature which will
lead to more evaporation.
– Snow-albedo effect
• As the snow and ice melts from the polar regions, the albedo of the earth
will be reduced. Temperature will increase.
• Negative Feedback Mechanisms – A process whereby an initial change in
an atmospheric process will tend to weaken the overall effect.
– Increased warming of the earth surface will lead higher emission of IR
radiation
• The higher the IR surface output, the slower the rise in temperature in the
atmosphere.
– Increase in clouds
• Warmer surface will lead to more evaporation which leads to more clouds.
•Just 18,000 years ago, the Earth was in an ice age where continental glaciers
reached as far south as the Ohio River Valley over North America.
•Over Europe, the northern region and higher terrain were covered in thick sheet
as well.
•The glacial advance/retreat occurred about 10 times over a 2 million year period.
Main Natural
Factors that
Affect Climate
Milankovitch Theory of Climate Change
• Climate change may be driven by changes in earth's:
a) orbit (eccentricity) → from ellipse to circle at a 100,000 year cycle.
from
b) wobble (precession) → from the north pole pointing toward or away
the sun in a 23,000 year cycle.
c) tilt (obliquity) → from 22° to 24.5° at a 41,000 year cycle.
Eccentricity is the major forcing factor for the timing of ice ages.
Main Natural Factors
The Sun
• The amount of energy
coming off the Sun is not
constant but keeps changing
• Slow changes in the Earth's
distance from the Sun affect
the amount of energy
received from the Sun.
• Those variations are believed
to be one of the causes that
start ice ages.
Solar Output Variation and Climate Change
• The sun usually experiences a 11-year cycle of maximum and minimum in
sunspots.
•From 1645 to 1715, the sun went through a long duration of minimum
sunspots which coincided with a cooling spell called the Maunder Minimum.
•Recent researchers have found the 11-year sunspot cycle and the weather
pattern in North American can be related to:
•Warmer winter
Main Natural Factors
• Volcanoes - when a volcano
erupts it throws out large
amounts of sulphur dioxide
(SO2), water vapour, dust,
and ash into the atmosphere.
• The climate system is made
up of many components
that all affect climate: this
includes ocean currents,
atmospheric circulation,
sea ice and land covers
(trees, grass…)
Mt. Pinatubo Eruption & Impact
•Three months after the June 1991 eruption of this Philippine volcano,
much of the 20 million tons of ejected sulfur dioxide had been directed by
zonal stratospheric winds and inundated the equatorial region.
•Recorded changes in air temperature indicate the volcanic eruptions on
climate.
•“The year without the summer” (1816) brought heavy snow in June and
killing frost with respect to the vegetation in July and August over the
northeast United States. These freakish events coincided with a massive
volcanic eruption of Mount Tambora.
The two major variations of temperature in the atmosphere are due to
the eruption of El Chichon volcano in Mexico (1982) and Pinatubo
volcano in the Philippines (1991).
• An eruption can cause warming and
cooling.
– An addition of carbon dioxide contributes to
greenhouse warming.
– An addition to sulfurous gases induces
cooling, because they turn into droplets of
sulfuric acid that absorb and reflect sunlight,
and cut down the amount of heat that reaches
the ground.
• But most documented cases show a net
cooling effect.
Main Natural Factors
The Greenhouse Effect
controls our climate
• When energy from the Sun enters the
Earth's atmosphere, about a third of it is
reflected back to space.
• Of the remainder, most is absorbed by
the Earth’s surface. Some also stays in
the atmosphere, absorbed by water
vapor and green house gases.
• This natural Greenhouse Effect is vital
to life as we know it.
• Right now, the average temperature on
the Earth is 15°C. If there was no
greenhouse effect, the average
temperature would be -18°C (33°C
colder than it is now – too cold for most
living beings).
3 is the Greenhouse Effect
Long Term Affects
• Volcanic particles can cause occurrences
such as:
– Global Cooling
– Mass Extinctions
– Ice Ages
Little Ice Ages
• 1783 – Skaftar in Iceland and Mount
Asama in Japan erupted.
• These eruptions were followed by several
very cold winters in Europe and America.
• They caused unusually thick polar ice to
form.
Plate Tectonics
180 m.y.a.
Present
Plate tectonics and drift concentrated continents at higher latitudes
allowed for more ice cover, which reflected more sunlight and created a
positive feedback to cause greater cooling.
Periods of mountain building increase snow-covered high elevation
areas producing a similar snow-albedo positive feedback.
The position of continents, mountains, and oceans create complex
changes in atmospheric (and oceanic circulation).
Extinction of the Dinosaurs
• Billions of tons of dust and debris were injected into atmosphere around 65
m.y.a. from a giant meteorite collision with earth.
• The reduction in sunlight from the dust and debris clouds caused
photosynthesis to stop and broke down the food chain.
• This catastrophic collision is evident around the world from a thin layer of
sediment deposit called the K-T boundary where it separates the end of the
Cretaceous period, and the beginning of the Tertiary Period.
• The K-T boundary is made up of iridium material which is commonly found in
meteorite.
Main Human
Factors
that Affect
Climate
Main Human Factors
Greenhouse Gases
• Human activities send gases (for example
methane, carbon dioxine CO2) into the
athmosphere that enhance the greenhouse effect.
• Many of the gases come from fossil fuels such as
oil, coal and natural gas to run vehicles, and
generate electricity for industries or households.
• When the atmosphere contains too much of those
gases, the whole atmosphere and the Earth
becomes hotter, like it does in a greenhouse. The
atmosphere holds on to too much heat, instead of
letting it escape into space.
This causes global warming !
Main Human Factors
The example of CO2
• Today there is about 25% more Carbon dioxide (CO 2) in
the atmosphere than in 1860. CO2 is the greenhouse gas
that people make the most of. The more CO 2 we put into
the air, the more the temperature could rise.
• Two of the biggest sources of CO2 are burning fossil fuels
and cutting down and burning trees.
• Forests are called « carbon sinks » because they take
CO2 from the air and store it. When trees are cut down
and burned, the CO2 that is stored in them is released
back into the air. Scientists believe that every year, 2 to 5
billion tonnes of CO2 are released into the air from forests
being cut down and burned.
Main Human Factors
Aerosols
• Aerosols are tiny solid
particles or liquid
droplets that remain
suspended in the
atmosphere for a long
time.
•They originate naturally (for example from volcanoes)
but also as a result of human activities (industries…). In
the later case, aerosols are considered pollutants, which
cause direct effects on the Earth’s radiation budget and
also indirectly through changing the formation and
behavior of clouds.
Main Human Factors
Land Use Change
• There are over 6 billion
people on Earth. Humans
continue replacing forests
and natural vegetation with
agricultural lands. More and
more people move into
cities, therefore more
houses are built. All this has
an impact on climate.
• For example, it affects the
evaporation of water and
therefore the rain cycle.
What is global warming?
It refers to an average increase in
the Earth's temperature, which in
turn causes changes in climate.
A warmer Earth leads to a wide
range of impacts on plants,
wildlife, and humans.
Observed data indicate that global
temperature over land and ocean
has increased by approximately
0.6°C (1.08°F) since the late
nineteenth century.
Do you know exemples of effects
global warming has on our Planet?
Our future climate according to scientists
According to meteorologists and
climatologists (they are the scientists who
study weather and climate), the changing
climate very likely entail more:
•Heat waves
•Heavy rain and snow
•Droughts
•Tropical cyclones
Our future climate according to scientists
Rising sea level
Scientists also predict that global warming
will cause the level of water in the oceans
to rise between 15 and 95 cm in the next
100 years, because warmer temperature
will cause sea ice and glaciers to melt,
adding more water to oceans, and because
as water gets warmer, it takes up more
space
IPCC
It won
IPCC stands for the Intergovernmental
the nobel
Panel on Climate Change created by the prize!
World Meteorological Organisation
(WMO) and the United Nations
Environment Programme (UNEP).
It brings together scientists from around
the world to report on climate change.
IPCC advises that for a better future, we
need:
• to reduce greenhouse gas emissions
• to adapt to climate change (for
example with better alert systems,
water and food management).
Through WMO, 188 Member countries worldwide produce,
share and improve information on weather, water and
climate, including forecasts and warnings.
WMO organizes training for weather and climate
professionals to bring you reliable and clear information.
The Meteorological and Hydrological Services work
together within WMO to improve the quality and safety of
your life.
What can we do to improve
our climate?
Please tell us what you think
For more information
• WMO comic book: « We care for
our planet » - WMO-No. 975
•The World Meteorological
Organization in your daily life
• A career in meteorology
WMO-No. 1012
• WMO « Skies and Oceans »
Youthfull perspectives
• WMO web site : www.wmo.int
• IPCC web site : www.ipcc.ch