4. 1. Weather and Climate
W
E
A
T
H
E
R
a specific event or condition or the state of the atmosphere
that happens over a period of hours or days.
is the temperature, humidity, precipitation, cloudiness and wind that we
experience in the atmosphere at a given time in a specific location.
C
L
I
M
A
T
E
the average weather over a long period of time and generally for a specified
geographical region.
It depends on how much radiation (heat) reaches the earth from the sun,
and how much radiation is given off by the earth.
For example,
the climate in Polar Regions is cold and snowy in the winter,
while climate in equators are hot and humid.
Weather is what is happening around us at any one moment every day
i.e., what is the weather like today? It is dry and sunny now but it might rain
later. Types of weather include sunny, cloudy, rainy, windy, and
snowy.
is the average weather over a long time period (30 – 50 years) in a region.
5. 1. Weather and Climate
Global
C
L
I
M
A
T
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o The average climate around the world is called global climate.
o Meteorologists (scientists who measure the weather) collect detailed
information about the weather every day, often using high-tech
satellite and computer systems, to determine climate.
C
L
I
M
A
T
E
VARIABILITY
o Climate variability refers to natural variation in climate that
occurs over months to decades.
6. 1. Weather and Climate
Climate
Scale of Weather and Climate
Global Change
Minute
Hour
Day
Week
Month
Year
Decade
Century
1 Km 10 Km 100 Km 1000 Km 100000 Km
10000 Km
Dust
Storm
Tornado
Thunder
Storm
Typhoon
Torrential Rain
Front
Monsoon
El Nino
squall
line
Low/High
Pressure
Short-range weather forecasting
Medium-range weather forecasting
Short-term Climate prediction
Long-term Climate prediction
Climate Change prediction
Small S (＜2Km） Meso-Scale（2-200 Km） Large S（200-10000 Km） Global S（＞10000 Km）
Point of Transition
Weather
Nowcasting
6
8. 1. Weather and Climate
BASIS FOR
COMPARISON
WEATHER CLIMATE
What is it? Minute by minute state of
atmosphere in an area.
Average weather in a
region.
Represents What are the condition of
atmosphere in a geographical
location, over short period.
In what way atmosphere
acts over typically long
period.
Variation Varies constantly. Does not vary constantly.
Affected by Temperature, humidity, air
pressure, cloudiness, precipitation
etc.
Temperature and
Precipitation.
Assessment For short term Over a long period
Study Meterology Climatology
Meaning Weather is everyday atmospheric
condition of a particular region, as
regards temperature, humidity,
wind speed, etc.
Climate alludes to standard
pattern of weather of a
particular place, taken over
more than 25-30 years.
9. 1. Weather and Climate
Factors that determine climate
1. Latitude: Distance north or south of equator.
10. 1. Weather and Climate
Factors that determine climate
2. Altitude: Distance above or below sea level.
3. Topography: Distance from mountains (how close they are).
11. 1. Weather and Climate
Factors that determine climate
4. Global winds: The circulation of global air called wind, hot or cold.
12. 1. Weather and Climate
Factors that determine climate
5. Ocean currents: The circulation of ocean.
6. Distance from water: How close the area is to and ocean or lake or any water
body.
13. 2. Definition of Climate Change
Climate change
o Climate is the average weather at a given point and time of year, over a long
period (typically 30 years).
o We expect the weather to change a lot from day to day, but we expect the
climate to remain relatively constant.
o If the climate doesn’t remain constant, we call it climate change.
refers to a long-term change in the average weather patterns over a specific region,
over a significant period of time and
it includes changes in temperature, wind patterns and precipitation.
14. 3. Causes of Climate Change
a. Earth’s orbital changes
The earth makes one full orbit around the sun each year. It is tilted at an angle of
23.5° to the perpendicular plane of its orbital path. Changes in the tilt of the earth
can lead to small but climatically important changes in the strength of the seasons,
more tilt means warmer summers and colder winters; less tilt means cooler
summers and milder winters. Slow changes in the earth’s orbit lead to small but
climatically important changes in the strength of the seasons over tens of thousands
of years. Climate feedbacks amplify these small changes, thereby producing ice ages.
A. Natural Causes
15. b. Solar variations
The Sun is the source of energy for the earth’s climate system. Although the Sun’s
energy output appears constant from an everyday point of view, small changes over
an extended period of time can lead to climate changes. Some scientists suspect
that a portion of the warming in the first half of the 20th century was due to an
increase in the output of solar energy.
Scientific studies demonstrate that solar variations have performed a role in past
climate changes. For instance a decrease in solar activity was thought to have
triggered the Little Ice Age between approximately 1650 and 1850, when Greenland
was largely cut off by ice from 1410 to the 1720s and glaciers advanced in the Alps.
Current global warming however cannot be explained by solar variations. Some
examples are evidenced such as since 1750, the average amount of energy coming
from the Sun either remained constant or increased slightly.
3. Causes of Climate Change
A. Natural Causes
16. b. Solar variations
The Sun is the source of energy for the earth’s climate system. Although the Sun’s
energy output appears constant from an everyday point of view, small changes over
an extended period of time can lead to climate changes. Some scientists suspect
that a portion of the warming in the first half of the 20th century was due to an
increase in the output of solar energy.
Scientific studies demonstrate that solar variations have performed a role in past
climate changes. For instance a decrease in solar activity was thought to have
triggered the Little Ice Age between approximately 1650 and 1850, when Greenland
was largely cut off by ice from 1410 to the 1720s and glaciers advanced in the Alps.
Current global warming however cannot be explained by solar variations. Some
examples are evidenced such as since 1750, the average amount of energy coming
from the Sun either remained constant or increased slightly.
3. Causes of Climate Change
A. Natural Causes
17. c. Volcanic eruptions
Volcanic activity which can emit large volumes of sulphur dioxide, water vapour,
dust, and ash into the atmosphere—called aerosols that reflect solar energy back
into space and have a cooling effect on the world. The carbon dioxide is also
produced into the atmosphere by volcanic eruption, thus increase greenhouse gases
and have a heating effect on the world, causes climate change; however the carbon
dioxide produced is insignificant when compared to emissions created by humans.
3. Causes of Climate Change
A. Natural Causes
18. d. Ocean current
The oceans are a major component of the climate system. Changes in ocean
currents shift air currents. Ocean currents move vast amounts of heat across the
planet. Winds push horizontally against the sea surface and drive ocean current
patterns i.e., deep ocean circulation of cold water from the poles towards the
equator and movement of warm water from the equator back towards the poles.
Without this movement the poles would be colder and the equator would be
warmer. Moreover, the oceans play an important role in determining the
atmospheric concentration of carbon dioxide. Changes in ocean circulation may
affect the climate through the movement of carbon dioxide into or out of the
atmosphere (or ocean). As we know earlier that carbon-dioxide absorbs heat and
creates global warming.
3. Causes of Climate Change
A. Natural Causes
19. Same as Causes of Anthropogenic GHE & GW
The Industrial Revolution in the 19th century saw the large-scale use of fossil fuels
for industrial activities. These industries created jobs and over the years, people
moved from rural areas to the cities. This trend is continuing even today. More and
more land that was covered with vegetation has been cleared to make way for
houses. Natural resources are being used extensively for construction, industries,
transport, and consumption. Consumerism (our increasing want for material things)
has increased by leaps and bounds, creating mountains of waste. Fossil fuels such as
oil, coal and natural gas supply most of the energy needed to run vehicles, generate
electricity for industries, households, etc. Also, our population has increased to an
incredible extent. All this has contributed to a rise in greenhouse gases in the
atmosphere causes climate to change.
3. Causes of Climate Change
A. Natural Causes
20. Same as Causes of Anthropogenic GHE & GW
3. Causes of Climate Change
A. Anthropogenic Causes
21. 3. Causes of Climate Change
Climate change is causing five critical global environmental changes:
1. Warming temperature of the earth’s surface and the oceans: The earth has
warmed at a rate of 0.13° C per decade since 1957, almost twice as fast as its rate
of warming during the previous century.
2. Changes in the global water cycle (‘hydrologic’ cycle): Over the past century
there have been distinct geographical changes in total annual precipitation, with
some areas experiencing severe and long-term drought and others experiencing
increased annual precipitation. Frequency and intensity of storms increases as
the atmosphere warms and is able to hold more water vapor.
3. Declining glaciers and snowpack: Across the globe, nearly all glaciers are
decreasing in area, volume and mass. One billion people living in river watersheds
fed by glaciers and snowmelt are thus impacted.
4. Sea level rise: Warmer water expands, so as oceans warm the increased volume
of water is causing sea level rise. Melting glaciers and snowpack also contribute
to rising seas.
5. Ocean acidification: Oceans absorb about 25% of emitted CO2 from the
atmosphere, leading to acidification of seawater.
23. 3. Causes of Climate Change
Climate change is causing five critical global environmental changes:
These global changes result in what we experience as changes in our local weather
and climate:
• Greater variability, with “wetter wets”, “drier dries” and “hotter hots”
° More frequent and severe extreme heat events
° More severe droughts
° More intense precipitation, such as severe rains, winter storms and hurricanes
• Higher average temperatures and longer frost-free seasons
• Longer wildfire seasons and worse wildfires
• Loss of snowpack and earlier spring runoff
• Recurrent coastal flooding with high tides and storm surges
• More frequent and severe floods due to intense precipitation and spring snowmelt
• Worsening air quality: Higher temperatures increase production of ozone (a key
contributor to smog) and pollen, as well as increasing the risk of wildfires.
• Longer pollen seasons and more pollen production
