4.4: CLIMATE CHANGE

Carbon dioxide and water vapour are the most significant greenhouse gases. Other gases including methane and nitrogen oxides have less impact. The impact of a gas depends on its ability to absorb long wave radiation as well as in its concentration in the atmosphere. The warmed Earth emits longer wavelength radiation (heat). Longer waved radiation is absorbed by greenhouse gases that retain the heat in the atmosphere. Global temperatures and climate patterns are influenced by concentrations of greenhouse gases. There is a correlation between rising atmospheric concentrations of CO 2 since the start of the industrial revolution 200 years ago and average global temperatures. Recent increases in atmospheric CO 2 are largely due to increases in the combustion of fossilized organic matter. NEED TO KNOW:

Many factors are thought to contribute to global temperature changes over time. Volcanic activity Position of the continents Oscillation in ocean currents But we are focusing on: the influence of changes in the composition of the atmosphere, notably the presence of greenhouse gases. WHAT WE ARE CONCENTRATING ON

Visible light from sun passes through glass in greenhouse Visible light is absorbed by surface (ground) Objects inside radiate their heat into the greenhouse. Light is re-radiated as heat (infrared) Glass is semi-transparent to infrared radiation Trapped IR waves (heat waves) – warm up greenhouse Glass prevents warm air from rising through convection to dissipate heat. Results in the temperature inside the greenhouse being warmer than outside. GHG’s have the ability to absorb and radiate IR (heat). They keep the atmosphere near Earth’s surface warm by absorbing heat from the warmed surface and redirecting it in all directions.

Different gases, different impacts Influence due to: Ability to absorb long-wave radiation (heat) Concentration of gas in atmosphere Methane: Warming Potential: High Duration: Short – 12 yrs Increase: 150% since 1750 Concentration: 1700 p.p.b. Carbon Dioxide: Warming Potential: Good Duration: Long– yrs Increase: 40% since 1750 Concentration: 400 p.p.m. Water Vapor: Warming Potential: Fair Duration: 9 days Concentration: variable Nitrous Oxide: Warming Potential: Great Duration: Long– 114 yrs Concentration: 320 p.p.b. Methane can be broken down into other molecules, whereas carbon dioxide is not very reactive.

Only a small amount of sunlight is converted into infrared to warm up the surface. The ability of a surface to reflect light is called its albedo. Light colored objects, such as ice and snow, have a high albedo so very little light is absorbed. Dark colored objects, such as dark rocks and black sand, have a low albedo so more light is absorbed. This light is converted to heat. WARMED EARTH EMITS LONGER WAVELENGTH

High Albedo Effect Low absorption is due to reflective surfaces – cooler atmosphere Low Albedo Effect High absorption, less reflective surfaces - warmer atmosphere

If Earth had no atmosphere, the heat from low albedo objects would radiate back into space, causing our night time temperatures to plunge. The greenhouse gases absorb and retain the IR coming from the surface, and re-radiate the heat in ANY direction. Shorter days during winter and at a different angle. Not as long for the sun to warm up the Earths surface. Certain gases also prevent harmful rays, like UV rays, from reaching the Earths surface. Preventing temperatures from reaching extremely high temperatures, like the moon (+120°C) HOW GREENHOUSE GASES HEAT THE ATMOSPHERE

Effect of angle of the sun? Types and amounts of gases in atmosphere?

Climate: the patterns of temperatures and precipitation Weather can change from hour to hours, but climate does not change typically. Earths’ temperature from thousand or millions of years ago can be inferred from proxies. Thermometers have only been around for a few hundred years. 15,000 years ago, it was very cold, and Earth was undergoing a glaciation (ice age). Proxy data: tree rings, coral reef growth, and the presence of fossils of temp- sensitive organisms, to estimate climate back then. GLOBAL CLIMATE CHANGE IN AFFECTED BY GREENHOUSE GASES

Due to atmosphere being opaque to more harmful, high energy waves  protective barrier Prevents overwarming IR is absorbed by atmosphere  leads to warming

Since the 1800s, humans have produced increasing quantities of carbon dioxide from factories, transport and other processes using fossil fuels. Give me an example. =) Diet also has an impact. Why do you think this? Since we eat a lot of meat, the raising of cattle has increased. What do cattle produce?  Methane with the aid of microorganisms. The problem? We do not see a sign of slowing the industrial revolution. THE INDUSTRIAL REVOLUTION

Industrial Revolution Muscle power  fuel (fossilized organic matter) power Releases GHGs into atmosphereCO 2 increased 35% Concentrations of GHGs naturally low  prevents too much warming CO 2 emissions: Human transport, deforestation, heating homes, high meat diet, purchasing high mileage goods Methane emissions: Cattle Nitrous oxide emissions: catalytic converters in cars, fertilizers, industrial processes

Water temperature: Water acidity: increased CO2 in the atm, lead to increased CO2 dissolved in the ocean, lowering the pH. Leading to the death of coral polyps and algae, when they die the reefs are not built up anymore. Depth of the water: This causes a “bleaching” of the coral and the organisms that live there are forced to find shelter elsewhere. This causes an interruption in the food chain. THREAT TO CORAL REEFS

Threats to Coral Reefs Sensitive to: Water temperature Water acidity Depth of water Death of coral = bleaching

Distinguish between politically controversial and scientifically controversial. P. 212 for more examples. ARE HUMANS CAUSING CLIMATE CHANGE?

Study Guide Questions 4.4 Challenge yourself p. 207 HOMEWORK

Light is divided into wavelengths. The colour of incoming light is determined by it's wavelength, or the frequency of the wave. Shorter wavelengths (higher frequency) contain more power than longer wavelengths (lower frequency) and are considered "bluer." Why bluer? Well, from longest wavelength to the shortest, colours are: Infrared> Red > Orange > Yellow > Green > Blue > Purple > UV So, you can see how a blue wavelength is shorter than a red wavelength... and thus, it contains more power. Now, greenhouse gasses, especially CO2 reflect longer wavelength radiation, and let higher wavelength radiation pass. This means, that the majority of the Infrared light that intercepts a CO2 molecule, will be scattered or reflected. Sunlight is a mix of wavelengths, most are within the red > blue spectrum (with little UV and IR radiation). Sunlight is allowed to pass through the greenhouse layer, and be absorbed by the surface of the Earth. Since all objects emit radiation (and the wavelength of this radiation is determined by the temperature of the emitting body) the earth's surface emits radiation too. However, since the earth is MUCH cooler than the sun, the earth mainly produces IR radiation. This, of course, travels outwards to space, yet is reflected back towards the earth by the greenhouse layer. Therefore, incoming radiation is allowed to pass, yet outgoing radiation is reflected and captured... More CO2, more reflection, higher temperatures for everyone.