Topic 4.4 Climate change

How do greenhouse gasses work?

Absorb and emit long-wave (infrared) radiation, thereby trapping and holding heat within the atmosphere. They make up less than 1% of the Earth’s atmosphere

Greenhouse gasses with largest effect

Water vapour (clouds) and CO2

How is water vapour created? (largest greenhouse gas)

The evaporation of water bodies (e.g. oceans) and transpiration

How is CO2 created? (largest greenhouse gas)

Cell respiration and burning fossil fuels

Other greenhouse gasses that have a lower impact and how they are produced

* Methane: Emitted from waterlogged habitats and landfills.
* Nitrogen oxides: Released by bacteria and exhaust of certain vehicles.

Two factors that determine the impact of a greenhouse gas

1. Ability to absorb long-wave radiation
2. Concentration within the atmosphere

Overall impact of a greenhouse gas

* Methane has a larger capacity to absorb long-wave radiation than carbon dioxide, but is significantly less abundant
* Water vapour enters the atmosphere rapidly but only remains for short periods, while carbon dioxide persists for years.
* Human activity is increasing the amount of greenhouse gases (except water vapour) and hence increasing their impact.

Why is the greenhouse effect a natural process?

* Ensures moderate temperatures on Earth
* Without greenhouse effect, temperatures would significantly drop at night.

How does the greenhouse effect work?

* incoming radiation from the sun is shorter wave radiation
* surface of Earth absorbs short wave radiation and re-emits it at a longer wavelength (heat)
* Greenhouse gases absorb and re-radiate this longer wave radiation and hence retain the heat within the atmosphere

How are human increasing greenhouse gas emissions? (farming)

* Deforestation
* Increased farming

CO2 increases the most, how come?

Combustion:

* When fossil fuels are combusted
* Increased reliance on fossil fuels

How will greenhouse gasses affect conditions on earth?

* More frequent extreme weather conditions
* Some areas to become more drought affected
* Changes to circulating ocean currents

How was the link between global temperatures and carbon dioxide laid?

* By analyzing data over a long time period
* Ice cores taken from the Vostok station in Antarctica provide evidence of the environmental conditions at the time of freezing
* The Vostok ice core is one of the longest drilled, reaching back 420,000 years and covering the past four glacial cycles
* By analyzing the gas bubbles trapped in ice, historical CO2 levels and air temperatures can be deduced.

What does data collected from the Vostok ice core demonstrate

* There is a strong positive correlation between CO2 conc. and temp
* There have been fluctuating cycles of CO2 conc. which appear to correlate with global warm ages and ice ages
* Current concentrations of CO2 are higher than at any time recorded in the last 400,000 years.

Since when have CO2 levels started rising significantly?

Since the industrial revolution