cive230 lec 5 - global atmospheric change including climate change

Climate

The long-term average of weather.

Weather

The short term variation in the long term climate. Day to day, short term atmospheric conditions

Climate Change

A change in the statistical distribution of weather patterns (e.g., avg. temperature, number of snowy days, rainy days, storms, severity, etc.) when that change lasts for an extended period of time.

Causes of climate change

anthropogenic processes, variations in solar radiation received by earth, plate tectonics, and volcanic eruptions

What is Earth’s climate governed by?

Absorption of solar radiation and emission of infrared radiation

Greenhouse gases

Carbon dioxide, methane, vapour, nitrous oxide. Also halocarbons. Emitted from anthropogenic and natural sources

Greenhouse Effect

Allows sun’s rays to come in but blocks outward flow of energy. Refers to the partial absorption by certain gases in the atmosphere of infrared radiation emitted by the Earth’s surface.

Human Impacts on Climate - how much radiative forcing has been caused?

• Humans have directly emitted and increased the concentrations of greenhouse gas emissions.

• This in turn has caused a radiative forcing so far of about 2.5-3.5 W/m2

If CO2 were to double, how much would radiative forcing be?

If CO2 alone were to double, radiative forcing would be about 3.75 W/m2

Impacts of Climate Change

Global average temperature rises, increase in frequency and intensity of weather events, snow cover drops, sea level rises, inundation, ocean acidification, species extinction

Impacts of global temperature rise

frequent wildfire, longer periods of drought, frequent extreme snow events, frequent hurricane/tornado, frequent flooding, change of location of weather events

Albedo

A measure of how reflective a surface is, the ratio of reflected radiation from the surface to incident radiation upon it

Radiative Forcing

The propensity for an atmospheric chemical to change the energy balance.

Positive radiative forcing

Chemicals which tend to increase the amount of energy in the earth’s atmosphere.

Negative radiative forcing

Chemicals which reduce the energy in the atmosphere

Global Warming Potential (GWP)

The relative impact of a GHG on the energy equilibrium.

What does lower level atmosphere do

GHGs absorb outgoing radiation from Earth’s surface, makes Earth warmer

What does upper level atmosphere do

Ozone layer absorbs UV rays

rate at which solar energy strikes the earth

SπR² (W)

Energy radiated equation

Q = σ4πR²T^4

earth’s albedo

0.31

what natural controls does the earth have to balance and control its climate

The atmosphere's greenhouse effect (traps heat), the role of the oceans in absorbing heat and carbon (absorb heat and carbon dioxides, acting as a carbon sink), and natural cycles that regulate atmospheric composition (radiative forcing, absorption of solar radiation, emission of infrared radiation)