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The Climate System
and
Climate Change
M.Abdel wahab
Usama Anber
Faculty of Science Cairo
University
Weather and Climate
Weather is what you get, Climate is what
you expect
E.Lorenz
The Climate System and Influences
Global warming

Heating

Temperature & Evaporation

water holding capacity

atmospheric moisture


greenhouse effect
& rain intensity

Floods
&
Droughts
Climate change
and its manifestation
in terms of weather
(climate extremes)
Greenhouse Gases
• Nitrogen, Oxygen and Argon (99.9% volume mixing
ratio) have only limited interaction with incoming
solar radiation, and they do not interact with the
infrared radiation emitted by the Earth
• A number of trace gases (carbon dioxide, methane,
nitrous oxide, and ozone) do absorb and emit
infrared radiation (as does water vapor)
• Water vapor, carbon dioxide and ozone also absorb
solar shortwave radiation
• Because they emit infrared radiation up- and
downward, these greenhouse gases increase the
energy received at the Earth’s surface, thus raising
the temperature
The carbon cycle
• Humans put vast amounts of CO2 into the atmosphere.
• The earth/atmosphere removes about half of it.
• Exponential rise in concentration 250 - 370 ppm in last 150 Y.
• Concentration increases by about 3.5 ppm/year.
• Atmosphere oceans plantsanimalsearth.
• Humans and volcanoes return CO2 to the atmosphere.
Changing Atmospheric Composition:
Indicators of the Human Influence
Global, well-mixed greenhouse
gas (GHG) concentrations
CO2
• 31% increase since 1750: Highest levels
since at least 420,000 years ago
• Rate of increase unprecedented over
at least the last 20,000 years
CH4
• Increased 150% since 1750 to its highest
levels in at least 420,000 years
N2O
• Increased 16% since 1750 to its highest
levels in at least 1,000 years
1000
1200
1400
1600
Year
1800
2000
Negative feedback
Positive feedback
Causes of Climate Change
• Variation in solar output.
– Period of about 11 years.
– .1 - .2% due to sunspot activity.
• Drought in Great Plains and Nile River drainage areas
have been linked to this cycle.
• The "Maunder Minimum" coincided with the Little Ice
Age.
• Fairly strong link between the sunspot cycle and the
quasi-biennial oscillation of the stratosphere.
• The sun's output has increased by about 1/3 since earth
formed, yet warmest temperatures were in the past
• Changes in Earth's Orbit
– Milankovitch cycle
• Eccentricity -- about 100 TY cycle.
• Circular to highly elliptical.
• Aphelion distance varied between 1 and 11%
during last 600 TY.
• Earth Sun distance varies  3% between
Aphelion in July and Perihelion in January.
– Earth receives about 7% more insolation in
January than in July.
• Has decreased for about 15 TY
• Will decrease for another 35 TY.
Obliquity -- tilt of Earth's axis with respect to the orbital
plane.
• Varies 22.1° to 24.5°.
•
41000-year cycle.
• Higher latitudes effected more than lower.
– Receive as much as 15% more radiation in summer
when the tilt is greatest.
• The most recent maximum tilt occurred about 10000
years ago.
Changes in Atmospheric Turbidity -- affect
the surface and atmospheric energy balances.
• Tropospheric Aerosols -- Cool the surface, short
residence time.
• Stratospheric Aerosols -- Cool the surface, long
residence time.
Changes in Radiation Absorbing Gases -- Increases
may warm the lower troposphere and cool the
stratosphere.
• Carbon Dioxide and other Green House Gases
• Gases such as methane, nitrous oxide, and
chlorofluorocarbons combined, produce as large an effect
as carbon dioxide but carbon dioxide gets most of the
press.
• Atmospheric concentrations of these gases have increased
steadily since the industrial revolution.
• Green house gases directly affect the energy budget, but
perhaps more important, the increase in lower tropospheric
temperature raises water vapor concentrations. Since water
vapor is a better green house gas than any of the others,
this further raises temperatures.
Figure 2: Annual Temperature Trends,
(°C / century) 1901-1999
Source: P. Jones, et. al. 2000.
Annual Global Mean Surface Temperature
and Carbon Dioxide Concentrations
Global Temperature (°C)
CO2 Concentration (ppmv)
T
CO2
Year
Confidence in the ability of models to project
future climate has increased
Simulated Annual Global Mean Surface Temperatures
Will all regions in the world experience the
same amount of climate change?
NO
• Some regions will response to global climate
change more than do others. What are they ?
• Regional Climate Change Index (RCCI) was
developed to measure the so called Hotspots,
that is, regions that are more responsive to
global change.
• Regional Climate Change Index (RCCI) is a
comparative index based on: changes in mean
precipitation, changes in mean regional
temperature compared to global temperature
change, changes in precipitation and
temperature inter-annual variability.
• Output Data from 14 GCMs.
• Three Emission Scenarios, B1, A2 and
A1B. (Scenario Ensemble )
• Applying the RCCI to study the regional
variability in climate over Africa during the
21st century.
• Results show that Southern Mediterranean
(SMED) and Sahara (SAH) are the most
sensitive regions to global climate change
than any other regions in Africa.
• Egypt lies in these two regions.
Hotspots over Africa at the beginning of
the 21st century
Hotspots over Africa at the end of the 21st
century
Situation in Egypt at the beginning and at
the end of the 21st century
Thank You!