Climate Weather and Global Warming What Is Weather
Climate, Weather, and Global Warming
What Is Weather? • Weather is the conditions in the atmosphere at a particular place and time. • “Weather” describes all aspects of the atmosphere and is closely related to the transfer of thermal energy. • Atmospheric pressure, measured with a barometer, is the amount of pressure the molecules in the atmosphere exert at a particular location and time. • Atmospheric pressure is measured in kilopascals (k. Pa) = 1 N/m 2 • • • Our bodies equalize pressure = why our ears pop with pressure change At sea level, atmospheric pressure = 1 kg/cm 2, and as you increase altitude, the pressure drops. Warm air is lighter and less dense than cool air and so warm air has a lower pressure than cool air. Atmospheric pressure exerts force on you from all directions.
What Is Weather? • Humid air (air with more water vapour) has lower pressure than dry air. • When pressure drops moist air is arriving in the area. • Specific humidity = the total amount of water vapour in the air. • Dew point = the temperature where no more water vapour can be held by air • Relative humidity = the percentage of the air that is currently holding water vapour • 45 percent relative humidity means that the air is holding 45 percent of the water vapour it could before reaching its dew point.
Convection in the Atmosphere • Wind is the movement of air from higher pressure to lower pressure. High pressure system • An air mass is a large body of air with similar temperature and humidity throughout. • Air masses take on the conditions of the weather below. • Air masses can be as large as an entire province or even larger. • High pressure systems form when an air mass cools. • This usually occurs over cold water or land. • Winds blow clockwise around the centre of the system. • Low pressure systems form when an air mass warms. • This usually occurs over warm water or land. • Winds blow counterclockwise around the centre of the system. • Lows usually bring wet weather. Low pressure system
Prevailing Winds • Prevailing winds are winds that are typical for a location. • Winds in British Columbia usually blow in from the ocean. • Precipitation falls as air is forced up the mountain slopes. • Air gets drier as it moves inland, continuing to drop precipitation. • Dry air rushes down the far side of the mountains into the prairies. The prevailing winds off British Columbia’s coast, crossing into Alberta.
The Coriolis Effect • Winds move from higher pressure to lower pressure. • In a simple model, air would warm in the tropics and rise. • Cooler air from the north would rush in below to fill the empty spot. • The warm air at higher altitudes would move north to replace the cooler air. • This occurs at several latitudes as we move north. • As Earth rotates, these winds are “bent” clockwise = Coriolis effect • The equator moves much more quickly than do the poles. • Wind systems develop. • The trade winds • The prevailing westerlies • The polar easterlies Wind systems of the world.
Jet Streams, Local Winds, and Fronts • Strong winds occur in areas between high and low pressure systems. • The boundaries between the global wind systems have very strong winds. • In the upper troposphere, between warm and cool air, are the jet streams. • The polar jet stream can move at 185 km/h for thousands of kilometres. • Planes flying east across Canada “ride” the jet stream and avoid it flying west. • Local winds arise and are influenced by local geography. • In British Columbia, sea breezes blow inland (onshore breeze) when the land warms in the morning and outward (offshore breeze) when the land cools in the evening. • A front is a boundary between two different air masses. • Cold air forces warm air to rise, so fronts usually bring precipitation.
Extreme Weather • Air masses often have very large amounts of thermal energy. • Extreme weather can arise under certain conditions as this energy is released. • Thunderstorms occur when warm air rises and water condenses (which releases even more energy), building the thunderhead even higher. • Static energy can be built up and released as lightning. • Sea breezes in the tropics and energetic cold (and even warm) fronts can cause thunderstorms. • Tornadoes form when thunderstorms meet fast horizontal winds. • A “funnel” of rotating air may form, which sometimes extends all the way to the ground with winds of up to 400 km/h. • The tropics, with their intense heat, can often have severe weather. • Large masses of warm, moist air rise quickly and cool air rushes in. • Air rotates counterclockwise in the northern hemisphere, clockwise in the south. Hurricanes = tropical cyclones = typhoons
Natural Climate Change • “Climate” describes the average conditions of a region. • Climate is usually measured over a minimum of 30 years or more. • Climate = clouds, precipitation, average temperature, humidity, atmospheric pressure, solar radiation, and wind. • The size of the region can range from an island to the entire planet. • Climate and geography combine to allow specific organisms to grow. w Biogeoclimatic zones have distinct plants, soil, geography, and climate. w British Columbia has 14 distinct biogeoclimatic zones.
Looking Forward by Studying the Past • Paleoclimatologists study long-term patterns in various regions. • • Fossils may show what kind of environment was present. Tree rings show evidence of growing seasons. River sediments can reveal types of rainfall. Glacier ice cores show air condition and composition for thousands of years. • Gases trapped in the ice, specifically CO 2, reveal long-term atmospheric levels. • Fossils and sediment evidence show Earth’s climate has drastically changed often in the past. • 21 000 years ago, much of Canada and northern Europe was under glaciers.
Looking Forward by Studying the Past • Ice core data reveal CO 2 levels for the past 650 000 years. • Scientists have also tested the atmospheric air for CO 2 for the past 50 years
Factors That Influence Climate: Composition of Earth’s Atmosphere • Earth is a closed system. • A system is a group of parts that all function together as a whole. • Very little energy (except radiant energy) enters or leaves the system. • Earth’s atmosphere is the outer boundary. • A greenhouse is a closed system that absorbs thermal energy. • The Earth’s “natural greenhouse effect” allows a narrow range of temperatures. • Solar radiation comes in, is absorbed, and is then emitted trapped before being able to escape. • Greenhouse gases in the atmosphere absorbs thermal energy. • This keeps Earth an average of 34ºC warmer than it would be otherwise. • More greenhouse gases could make it too warm.
Factors That Influence Climate: Earth’s Tilt, Rotation and Orbit • Earth’s tilt is responsible for seasons in northern hemisphere. • In summer, we are tilted toward the Sun, decreasing the angle of incidence. • In winter when we are tilted away from the Sun, solar radiation has a large angle of incidence. • Earth’s tilt varies between 22. 3º and 24. 5º (currently 23. 5º) in 41 000 year cycles. • When tilt is largest, climate should experience the largest extremes. • Earth also “wobbles” as it rotates on its axis. • Because the axis changes on a 23 000 year cycle, the angle of incidence of solar radiation also changes. • Earth’s revolution around the Sun is elliptical, not circular. • On a 100 000 year cycle, Earth’s elliptical orbit becomes more circular. • When the orbit is most elliptical, Earth is farther away from the Sun.
Factors That Influence Climate: The Water Cycle • The water cycle describe the circulation of water on, above, and below Earth’s surface. • 70 percent of all greenhouse gases in the atmosphere is water vapour. • When temperature increases, more water evaporates. • More water vapour in the atmosphere may have two effects. • More solar energy may be absorbed by this greenhouse gas. • More solar energy may be reflected back out to space and never reach Earth. The water cycle stores and transfers large amounts of thermal energy.
Factors That Influence Climate: Ocean Currents • Convection currents in the oceans move large amounts of thermal energy all around Earth. • Deep ocean currents (200 m and deeper) flow based on density differences. • They behave like massive convection currents, with warm water rising in the tropics and cold water from the higher latitudes replacing it. Deep-ocean currents move cold, salty water below the surface and warm, less-salty water near the surface.
Factors That Influence Climate: Ocean Currents • Salinity of water also changes density. • Cold water (found at the poles) is more dense than warm water. • Salty water (found at the poles) is more dense than fresh water. • Large changes in ocean water density can reverse current direction. • Surface currents (0 - 200 m) are warmed by from solar radiation. • The thermocline is the region separating surface and deep ocean currents. • Upwelling occurs when cold, deep water rises into surface currents. • La Niña is an example of upwelling. • When this occurs, cool water at the surface of the Pacific Ocean causes warm winters in southeastern North America, and cool winters in the northwest. • El Niño is the reverse: warmer water on the surface of the Pacific Ocean results in warm winters in the Pacific Northwest and in eastern Canada.
Factors That Influence Climate: The Carbon Cycle • Carbon dioxide is a very important greenhouse gas. • Even though each molecule absorbs only a small amount of thermal energy, there are more CO 2 molecules than any greenhouse gas other than H 2 O. • Without CO 2 to trap infrared radiation from Earth’s surface, the average temperature of Earth would be below freezing. • The carbon cycle maintains a balance of CO 2 in the atmosphere. • Deep oceans are carbon sinks, as are forested areas. • CO 2 in the ocean is converted to carbonates (CO 32 -), in shells. • Phytoplankton use CO 2 for photosynthesis at the ocean’s surface. • Weathering of rocks releases carbon. • Carbonic acid is formed when water reacts with CO 2 in the atmosphere. • Forests take in CO 2 while growing but release CO 2 when burned or when decaying.
Factors That Influence Climate: The Movement of Tectonic Plates, and Catastrophic Events • Large=scale disasters can quickly change atmospheric conditions. • Erupting volcanoes can release ash and molten rock that absorb radiation. • Water vapour and sulfur dioxide (changed into sulfuric acid) can reflect solar radiation back into space. • Meteorites and comets are thought to have caused dramatic changes. • These large masses strike Earth and the result is large quantities of dust, debris and gases in the atmosphere. • Solar radiation is affected so much that it is thought that these events are responsible for some of Earth’s largest extinction events. Large comet and meteor collisions with Earth can cause debris to block solar radiation and change all over the Earth.
Human Activity and Climate Change • Climate change is the change in long-term weather patterns in certain regions. • These changes can affect the flow of thermal energy over the entire Earth. • Several ice ages have occurred in the past million years. • Global warming refers to a global increase in average temperature. • Both the causes and effects of global warming are unknown and controversial.
The Enhanced Greenhouse Effect • The enhanced greenhouse effect increases thermal energy absorbed. • More greenhouse gases in the atmosphere = increase of natural greenhouse effect • Greenhouse gases include water vapour, CO 2, methane, nitrous oxide, and CFCs. • Global warming potential (GWP) refers to the ability to trap thermal energy. • CO 2 is given a GWP of 1; CFCs are 4750 -5310.
The Enhanced Greenhouse Effect: Carbon Dioxide and Methane • CO 2 levels have increased greatly in the past 200 years. • Since the Industrial Revolution, humans have greatly increased their overall use of fossil fuels, which release CO 2 when burned. • Deforestation has changed carbon sinks, such as forests, into carbon sources. • Many people are attempting to reduce CO 2 emissions by using alternative energy sources or by reducing their energy use. • Carbon offsets, such as wind farms, can be purchased to offset CO 2 emissions. • Methane is very efficient at trapping thermal energy. • 25 X more efficient than CO 2 • Methane is produced by bacteria breaking down wastes in oxygen-free environments, animals digesting plant matter, rice paddies (and other natural wetlands), and the burning of fossil fuels. Livestock produce 18 percent of the total methane in the atmosphere.
The Enhanced Greenhouse Effect: Nitrous Oxide, Ozone, and Halocarbons • Nitrous oxide, N 2 O, is the third largest contributor to the enhanced greenhouse effect. • Even though there are only small amounts, it has 300 X more GWP than CO 2. • N 2 O comes from bacteria, fertilizers, and improper disposal of human and animal waste. • Ozone is an important UV radiation blocker in the stratosphere. • At lower altitudes, however, it is a very powerful greenhouse gas. • This ozone comes from solar radiation reacting with pollution from the burning of fossil fuels, and is released from photocopiers and certain air conditioners. • Halocarbons, used as refrigerants, are strong greenhouse gases. • Chlorofluorocarbons (CFCs) are the best-known halocarbons. • Halocarbons are also the main reason for ozone layer depletion.
Albedo and Climate, Making Predictions About Climate Change • The albedo at Earth’s surface affects the amount of solar radiation that region receives. • Changes in a region’s albedo - for example, snow cover melting earlier in the season than it did previously Could result in climate change. • Forests have a low albedo. Deforestation increases albedo. • Forests also emit large amounts of water vapour, which reflects solar radiation back into space. • Deforestation’s effects on climate change are unknown. Albedo for different surfaces
The Role of Science in Understanding Climate Change • Scientists use computers to model what Earth’s climate might be like. • Although models differ, most indicate that a decrease in the production of greenhouse gases is necessary to stop the apparent global warming trend. • Global warming models use data from multiple locations over long periods of time. • General circulation models (GCMs) are computer models used to study climate. • GCMs take into account changes in greenhouse gases, albedo, ocean currents, winds and surface temperatures. • GCMs are also used for weather forecasting, climate analysis, and climate change predictions. • Scientists are always trying to improve GCMs. • GCMs predict the future and reveal the past. Projected global temperatures.
The Role of International Cooperation in Climate Change • It is believed human-induced climate change is a recent occurrence. • The United Nations and the World Meteorological Organization created the Intergovernmental Panel on Climate Change (IPCC) to address global concerns about climate change and global warming. • The IPCC, formed in 1988, has Per capita emissions of greenhouse gases for various countries. members from 130 countries. • The IPCC examines possible climate change, highlights the causes, and suggests solutions. • The United Nations Framework Convention on Climate Change created a voluntary treaty to encourage governments to reduce greenhouse gas emissions.
Global Impacts of Climate Change
Impacts of Climate Change on Canada • Being in the northern hemisphere, Canada could be strongly affected by global warming. • Parts of Canada have had average temperature increases of 0. 5ºC to 1. 5ºC. • Southern and western parts of the country have been most affected. • The Arctic regions are losing permafrost and Arctic Ocean ice cover. • Growing seasons are getting longer and more precipitation is falling. • There could be heavier spring rains and severe droughts in the future. • Fisheries could be very negatively affected. • Pollution concerns could lead to health issues. • Most regions of British Columbia will probably be warmer, sea levels will rise, and fresh drinking water may be harder to find as glaciers disappear.
Uncertainty and Decision, An Action Plan for the Global Community • Although climate change is a controversial issue, our actions now are important. • Improving our environmental approach will help, no matter how dramatic climate change actually is. • Not acting could result in huge problems. • The United Nations suggests the precautionary principle, “better safe than sorry. ” • Relatively small changes could have large positive impact on the climate in Canada. • • Reduce vehicle greenhouse gas emissions. Reduce industrial greenhouse gas emissions. Increase use of energy-efficient products. Improve indoor air quality.
- Slides: 28