The seasonal cycle on Earth causes shifts in the bands of precipitation in the northern and southern hemispheres. The polar front shifts between high and mid-latitudes which causes a latitudinal shift in the occurrence of frontal cyclones. The Intertropical Convergence Zone also shifts across the equator bringing bands of precipitation to different tropical regions throughout the year. Regional climates on Earth have been classified based on temperature and precipitation values. Areas...

Renewable energy sources are discussed. These include wind energy, solar energy, biomass energy and geothermal energy. Energy from wind is acquired through the use of large wind turbines. These turbines ideally need to be located in areas where there is strong wind and low atmospheric turbulence. Solar power is collected using both photovoltaic solar cells and concentrated solar power. Energy from biomass can be produced in two ways: burning biomass to generate electricity or...

The various types of resources currently used for energy production are discussed. Energy is primarily used for heating, transportation, and generating electricity. Coal is burned largely to produce electricity and is a major contributor to air pollution with coal power plants emitting carbon dioxides and nitrous oxides. Another major resource used for energy is oil. It is projected that each country either has reached or will reach a peak oil use, after which oil use will decrease. ...

The material covered throughout the course is reviewed. Properties of air and water are discussed. Hydrostatic balance is discussed as related to the atmosphere, ocean and solid earth. Geostrophic balance is a force balance between the Coriolis force and the pressure gradient force, and applies to winds in the atmosphere as well as currents in the ocean. Several examples of equilibrium states are reviewed. Heat and mass are transported by fluid motion in the earth system through winds,...

Stratospheric ozone is important as protection from harmful ultraviolet solar radiation. Ozone in the stratosphere blocks almost all UVC radiation, which is extremely energetic and harmful. Ozone within the ozone layer is destroyed through chemical reactions involving chlorine atoms and the ozone molecules. The main anthropogenic source of chlorine in the atmosphere is chlorofluorocarbons (CFCs). Emissions of CFCs began to increase after 1960 and continued to increase until the 1990s. ...

Climate sensitivity is defined as either the temperature change resulting from a doubling of atmospheric carbon dioxide concentration or the temperature change resulting from a 1W/m2 increase in radiative forcing. There are several different climate sensitivities that take into account different feedbacks in the climate system. The simplest climate sensitivity is black body sensitivity, which does not account for any feedbacks but gives the temperature change resulting just from a change in...

There are two ozone problems in the atmosphere. Tropospheric ozone in the form of photochemical smog is sometimes dangerously high whereas stratospheric ozone concentration is sometimes dangerously low. Photochemical smog is created through chemical reactions between UV radiation from the run and nitrogen oxides that are emitted from automobiles. High concentrations of tropospheric ozone are dangerous because of the damage ozone can cause to a person’s airway if it is inhaled. The EPA has...

Several greenhouse gas emissions scenarios have been developed by the IPCC to determine possible affects on atmospheric greenhouse gas concentrations and related climate warming. The largest estimates show a carbon dioxide concentration of about 800ppmv by the year 2100. Lower estimates rise to 450ppmv by the year 2100. The amount of projected warming associated with these emissions scenarios range from about 2-4°C. Several possible disadvantages and advantages of such a warming are...

The current Holocene epoch is considered to be a time period of relatively stable climate compared to earlier geological periods. Still, some significant changes in temperature and sea level did occur. These climatic fluctuations include the Medieval Warm Period and the Little Ice Age, and more recently global warming. Temperature data for the 20th century shows a strong warming from about 1970 to the present day, typically associated with anthropogenic forcing including greenhouse gas and...

Isotopes are used to measure past climate properties. Deuterium and oxygen 18 are the most commonly used climate proxies. Lighter isotopes evaporate more readily from the ocean, so water vapor in the atmosphere is isotopically lighter than ocean water. This vapor gets lighter still as it is transported to higher latitudes while losing mass by precipitation. These processes leave an isotopic signal of temperature and continental ice volume in ice cores and deep sea sediment cores....

The issue of global warming is discussed. Recent climate change over the last half of the 20th century is thought to be driven largely by greenhouse gas emissions, with carbon dioxide playing a large role. The carbon cycle describes the reservoirs of carbon (atmosphere, terrestrial biomass and ocean) and the exchanges that occur between these reservoirs. Inputs of carbon to the atmosphere include burning of fossil fuels and respiration from biomass. Vegetation also removes carbon from the...

Ice on earth is sensitive to climate change and ice plays a role in climate change processes. Recent trends in the Greenland ice sheet provide an important example. Over the past two decades the extent of surface melt water on the ice sheet has increased. Inaddition, satellites have detected a decrease in the overall mass of the Greenland Ice Sheet. Paleoclimate is also discussed in this lecture, with a focus on climate over the last 5 million years. The mid-Pliocene was a particularly...

The El Niño/Southern Oscillation (ENSO) phenomenon is the primary mode of variability in the equatorial Pacific Ocean. It is composed of two extreme states, El Niño and La Niña. The oscillation between these states can be seen in measurements of sea surface temperature (SST), sea level pressure, thermocline depth, and easterly trade wind strength. Changes in SST and pressure lead to shifting of convective activity across the equatorial Pacific. Changes in the strength of the easterly...

Five types of ice in the climate system are discussed. Sea ice forms when ocean water reaches its freezing temperature of about -2°C. Sea ice is currently found in the Arctic Ocean and around Antarctica. Ice sheets form on land and are composed of compacted snow that has accumulated over time. Ice sheets spread over a land surface and can reach the ocean. If the ice continuity is maintained when the ice sheet reaches the ocean, the ice will float on the water and this is referred to as...

The atmosphere forces the ocean in three ways: addition and removal of heat, precipitation and evaporation, and wind stress. The former two processes influence the density of sea water. Gravity acts on these density differences to cause large-scale thermohaline currents Wind driven ocean currents are forced by the wind stress acting on the ocean surface which indirectly causes geostrophic currents. Complete course materials are available at the Open Yale Courses website:...

Ocean currents are generally divided into two categories: thermohaline currents and wind driven currents. Both types of currents are forced remotely rather than locally. Wind driven currents are initially forced by the wind stress causing water to pile up in certain locations. This produces a pressure gradient, which is then balanced by the Coriolis force and geostrophic currents develop. The gyre circulations found in the Atlantic and Pacific Oceans are wind driven currents. There is a...

There are several factors that impact climate on Earth. Different areas on Earth have different climates depending on factors such as their latitude and surrounding terrain. Maps of annual average precipitation illustrate these variations in climate. Continentality also affects climate based on the ability to change temperatures on land versus in the oceans and also the imbalance of land mass between the northern and southern hemispheres. Seasonality is a dominant factor in climate. It...

Stability in the ocean is based on the density of the water. Density must increase with depth in order for the ocean to be stable. Density is a function of both temperature and salinity, with cold salty water having a higher density than warm fresh water. Temperature and salinity in the ocean can be affected by the atmosphere. Heat can be added to or removed from the ocean, and precipitation and evaporation change the salinity of the ocean. Surface winds also act as a forcing mechanism...

Plate tectonics and ocean bathymetry are discussed. Bathymetry is the study of ocean depth, which is affected in some regions by plate tectonics and mantle dynamics. Mid-ocean ridges are formed at plate boundaries where mantle material is rising to the ocean crust and solidifying as it cools to form new ocean crust material. Seamounts are volcanoes that have formed from molten mantle material pushing up through the ocean crust, but these volcanoes lie below sea level. These features are...

Mid-latitude frontal cyclones gain energy from temperature gradients rather than latent heat release as is the case with convective storms. They form in the belt of westerly winds and therefore generally move west to east in both the northern and southern hemispheres. A mid-latitude frontal cyclone develops from a kink in the polar front, and eventually warm and cold fronts develop around a low pressure center to form the storm. An example of this type of storm is a nor’easter, which...

Large scale air motion in the atmosphere occurring sufficiently above the surface is in geostrophic balance. Areas of high and low pressure anomalies in the atmosphere are surrounded by rotating flow caused by the balance between the pressure gradient and Coriolis forces. The direction of rotation around these pressure anomalies reverses between the northern and southern hemispheres due to the reversal in sign of the Coriolis force across the equator. This can be seen in the reverse...

There are three main types of convective storms: airmass thunderstorms, severe thunderstorms and hurricanes. These storms are all driven by the release of latent heat into the atmosphere during condensation of water vapor. Severe thunderstorms include both squall line thunderstorms and tornados. They acquire energy from water vapor in the atmosphere over land and therefore typically require warm air temperatures and high humidity. Hurricanes gain energy from water vapor evaporated from...

The circulation in the atmosphere is composed of three circulation cells in the northern and southern hemispheres. These cells are caused by the rotation of the Earth which creates the Coriolis force. The Coriolis force deflects northern hemisphere motion to the right and southern hemisphere motion to the left. The majority of large-scale motion in the atmosphere is in geostrophic balance, meaning the Coriolis force acting on the motion is balanced by a pressure gradient force. The...

There is a latitudinal gradient of heat on the Earth caused by the tilt of the Earth’s axis with respect to the sun. This tilt produces seasonal fluctuations in heat input from the sun, as well as an excess of heat received on average annually near the equator. Heat is transferred poleward by both the ocean and atmosphere in an attempt to balance the Earth’s energy budget. The circulation of the Earth also causes a separation of the atmospheric circulation into three main circulation...

Scattered visible light and microwave radar can used used to detect clouds and precipitation. Cloud formation in rising air can be simulated in the classroom by suddenly dropping the pressure in a glass chamber. The small cloud droplets formed in this way fall too slowly to ever reach the earth. There are two main mechanisms by which precipitation is generated from clouds. Collision coalescence occurs mainly over tropical oceans whereas the ice phase mechanism is more common and also more...