Global Warming and Climate Change: Weather, Climate, and Greenhouse Effect

Weather vs. Climate

• Weather refers to short term conditions (e.g. 24 hrs.) in meteorological conditions such as temperature, pressure and rainfall
• Climate is average weather conditions recorded over long periods of time (e.g. decades)
• Similar climates produce similar kinds of ecosystems
• Knowing the climate we can make predictions as to the kinds of live that would occur/survive there

30 80 30 80 30 80 30 80 30 80 Temperature (°C) T 60 60 60 60 60 0 0 40 40 40 40 40 Humid continental 30 20 20 20 30 20 30 20 P 0 50 0 50 JFMAMJJASOND JFMAMJJASOND' JFMAMJJASOND" 60 60 30 30 0 0 30 30 Marine Subarctic Ice Cap Arctic 60 60 Continental Subarctic Marine West Coast Humid Continental Tropical Wet-Dry Steppe Mountains Monsoon Desert Mediterranean West Coast Desert Humid Subtropical 30 80 30 80 30 80 30 80 T 60 Desert 0 0 Humid Subtropical 40 30 20 P P 50 0 50 0 "JFMAMJJASOND' JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND Temperature (°C) 60 0 P 40 Monsoon 30 2 Precipitation (cm) Temperature (ºC) 60 8 Equatorial Wet 0 40 P 30 20 30 20 Precipitation (cm) Precipitation (cm) 50 0 50 0 Precipitation (cm) Temperature (°℃) Temperature (C) T 60 Precipitation (cm) 50 JFMAMJJASOND JFMAMJJASOND Precipitation (cm) Temperature (C) 0 0 0 T Precipitation (cm) Temperature (C) Precipitation (cm) Temperature (C) Continental Subarctic P P P 0 50 50 T Arctic Tropical wet-dry Mediterranean Precipitation (cm) Temperature (C) T 30 30 P 40 Equatorial Wet

Atmospheric Processes

• Temperature
• Measure of thermal energy (kinetic energy)
• Relative warmth/coldness of materials
• Pressure
• Force per unit area
• Caused by the weight of the overlying atmospheric gasses
• High Pressure systems
• Low Pressure systems
• Water vapour content
• Varies from 1% to 4% of air by volume
• Dependant on air temperature, pressure, availability of water vapour from surface
• Atmosphere moves due to Earth's rotation and differential heating of the surface and atmosphere
• These produce global circulation patterns and prevailing winds

Generalized Circulation of the Atmosphere (Hadley Cells)

Polar high pressure 3 High pressure Easterlies 60° Pressure Low - 2 Westerlies High Horse latitudes 30° Pressure Trade winds 1 0° - Low Doldrums Pressure - 1 circulation Trade winds 1 High Horse latitudes Pressure 30° I - -Westerlies - 2 Low Pressure 60 Easterlies High pressure 3 Polar high pressure Three-cell model of -

How We Study Climate

Instrumental Record

• Use of instruments to make climatic measurements began 1860's
• Temperatures measured at various places on land and in oceans
• Concentration of CO2 measured continuously since 1957
• Measured of solar energy for the past several of decades
• Problems:
• Few places have a complete record since 1850 (i.e. small dataset)
• Places that do not representative of global climate
• Until advent of satellites temp over oceans only measured by passing ships
• Many areas on Earth have never had good long-term ground based temp. monitoring

Historical Record

• People's written recollections (books, journals etc.)
• Farmer's logs (dates of harvests etc.)
• Paintings
• Mostly qualitative data

Paleo-Proxy Record

• Refers to data that are not strictly climatic in nature
• Can be correlated with climate data (such as temperature of the land or sea)
• Examples
• Ice Cores
• Tree Rings
• Sediments
• Corals

Ice Cores

• Polar ice caps and mountain glaciers have an accumulation record of snow
• Ice cores often contain small air bubbles (we can measure the gas content of these)
• Two important gasses used include CO2 and CH4
• Ice cores also contain a variety of other substances such as volcanic ash and dust etc.

Tree Rings

• Growth of trees influenced by climate
• Alternating rings indicate periods of rapid/slow growth based on the thickness of the ring
• Serves as a proxy for variability in climateanos

Sediments

• Biological material (esp. pollen from plants) can accumulate in sediments
• Can be stored for long periods of time
• Pollen useful because
• Quantity of pollen indicator of relative abundance of plant species
• Pollen can be dated
• Based on plant assemblage climate can be reconstructed

Coral

• Consists of CaCO3
• Contains isotopes of oxygen as well as a variety of other trace metals
• Used to determine the temp of the water in which the coral grew

Climate Change

Climate is always changing and this has been happening since the initial formation of the Earth · High temperature involves ice-free periods (inter-glacials) . Low temp. correspond to glacials Eemian interglacial 2 Present interglacial 15°C = Global average temperature O -2 My MOM W -6 1000 800 600 400 200 0 Thousands of years before present (B.P.) Change in temperature ("C) 2 -2 -6 ado db NON 15℃ -8 -10 160 140 120 100 80 60 40 20 10 (b) Thousands of years before present (B.P.) Change in temperature (°C) Medieval warm period 2 0 15℃ Little Ice Age -2 Younger Dryas -4 18 16 14 12 10 8 6 4 2 Thousands of years before present (B.P.) Change in temperature ("℃) 1 0.5 Medieval warm period 15°C O Renaissance Little Ice Age -0.5 -1 900 1100 1300 1500 1700 1900 (d) Year (A.D.) 0.6 0.4 Change in temperature (C) 0.2 0 15℃ -0.2 -0.4 -0.6 1860 1880 1900 1920 1940 1960 1980 2000 (e) Year (A.D.) 0 (c) Change in temperature ("℃) (a) -4

Causes of Climate Change

Milankovitch Cycles

• Has to do with the way the Earth revolves around its own axis and how it revolves around the sun
• 1. The spinning Earth is like wobbling top
• The wobble means the Earth is unable to keep its angle constant in relation to the sun (Precession of the Equinoxes)
• One complete cycle in 26 000 years
• 2. Earth's axis (angle regarding the ecliptic) changes over a period of 41 000 years
• 3. Elliptic orbit of the Earth changes from very elliptical to more circular (occurs over 100 000 years)

A. Precession of the equinoxes (period = 23,000 years) Sept 22 (autumn equinox) Today N Dec 21 Jun 21 Mar 20 (spring equinox) 5,500 years ago Jun 21 Sept 22 Mar 20 1 21.5° = minimum tilt Dec 21 11,500 years ago Mar 20 Plane of orbit Sun Jun 21 Dec 21 S Wobble of axis Sept 22 B. Tilt of the axis (period = 41,000 years) N 1 1 24.5° = maximum tilt Plane of orbit Sun E S N Equator E S C. Eccentricity (dominant period =100,000 years) Earth Sun High eccentricity (more elliptical) Low eccentricity (more circular)m

Greenhouse Effect

Energy and the Atmosphere

• Sunlight consists of electromagnetic radiation
• The hotter the surface the shorter the dominant radiation
• Earth receives short-wave radiation from sun and emits long-wave radiation back into space

Sun (5800°C) Earth (15℃) Relatively short-wave radiation from sun (mostly visible) Relatively long-wave radiation from Earth (mostly infrared) 105 m - Long radio waves 104 m - 103 m - AM radio 102m - 10 m - Shortwave radio 1 m - 10 cm Wavelength 1 cm - Microwaves 10-1 cm - 100 um - 10 pm - Infrared 0.7 um Red 1 pm - 0.6 um Orange Yellow Visible 10-1 pm - 0.5 um Green Blue Ultraviolet 0.4 um Violet 10-2 pm - 10-3 pm- X rays 10-4 pm- Gamma rays 1 um = 10-6 m = 1 micronm

Atmospheric Absorption and Reradiation

• Atmosphere reflects approx. 30% of EM radiation from sun and absorbs 25%
• Remaining 45% reaches the surface and heats up the surface (leads to long-wave radiation being emitted)
• Gasses in atmosphere absorbs some of these longer wavelengths, heats up and reradiates back to Earth's surface and to space

Sun (5800°C) Relatively short-wave radiation from sun (mostly visible) Relatively long-wave radiation from Earth (mostly infrared) 105 m - Long radio waves 104 m - 103 m - AM radio 102m - 10 m - Shortwave radio 1 m - 10 cm Wavelength 1 cm - Microwaves 10-1 cm - 100 um - 10 pm - Infrared 0.7 um Red 1 pm - 0.6 um Orange Yellow Visible 10-1 pm - 0.5 um Green Blue Ultraviolet 0.4 um Violet 10-2 pm - 10-3 pm- X rays 10-4 pm- Gamma rays 1 um = 10-6 m = 1 micron Earth (15℃)Relative intensity- Radiation emitted from Earth's surface Large Absorbed atmospheric in window; CFCs atmosphere and ozone by absorb here H2O and CO2 4 8 12 16 20 Wavelength (um)

Greenhouse Gas Absorption

• Each gas has its own absorption spectrum (which wavelengths it absorbs and which it transmits)
• Certain gasses are strong absorbers in the infrared (long-wave)
• Major greenhouse gasses
• Water vapour
• CO2
• Methane
• Oxides of nitrogen
• CFCs
• Keeps Earth's temp. 30℃ warmer than it would be otherwise
• Limits temperature swings from day to night and maintains a relatively comfortable surface temperature

Potential Effects of Global Warming

Glaciers and Sea Ice

• Lead to a decline in the volume of water stored as ice
• Potential to increase sea levels and reduce water availability for ecosystems
• Glaciers in North America & Europe are retreating rather than advancing
• Not all change in glaciers due to warming (e.g. Kilimanjaro)
• Areas covered by sea ice reducing (arctic could be seasonally ice free by 2030)
• Thickness of ice also an issue
• Melting of Greenland ice sheet has doubled since 1998 (could lead to further destabilizing of the ice sheet)

Changes in River Flow

• Increased warming leads to increased melting of glaciers and decreased rates of snow accumulation
• Reduces water availability in regions dependant on meltwater

Rise in Sea Level

• Sea level rises for two reasons
• Thermal expansion of water
• Addition of new water as glaciers and ice caps melt
• Rise predicted: 20cm to 2m
• Potential increase in flooding of coastal regions (serious threat when coupled with increasing population in these areas)
• Potential increase in coastal erosion
• Threat to island nations
• Could lead to saltwater intrusion of groundwater

Adjusting to Potential Global Warming

• People can adjust in two ways:
• 1. Adapt: Learn to live with future global climate change over the next 20 years
• 2. Mitigate: Work to reduce the emissions of greenhouse gasses and take actions to reduce the undesirable effects of global warming

Reduction in CO2 Emissions

• Energy conservation
• Transport
• Carbon sequestration
• International agreements
• Montreal Protocol (phasing out of CFCs)
• Kyoto Protocol (limit the emission of greenhouse gasses)
• Carbon trading