Science Man and His Environment/Global Warming

Recent Climate Change
The global temperature of the Earth has increased over the last century.

Current temperatures are 0.6 &deg;C over the 1950-1980 average





In the Arctic current temperatures are 2 &deg;C higher



Natural Greenhouse Effect


The above picture shows the natural greenhouse effect in red. All objects emit heat in the form of infrared (IR) radiation. Gases in the atmosphere absorb the IR radiation from the Earth and reradiate it back to the surface. This regulates the temperature.

The natural greenhouse effect allows life to survive on Earth.

But problems occur when humans cause additional greenhouse effects.

Greenhouse Gases
Now we can define global warming:

Major human-generated greenhouse gases :
 * Carbon dioxide 76% of all greenhouse gas emissions
 * Methane 16%
 * Nitrous Oxide 8%
 * F-gases (see below) 1%

Carbon Dioxide
Carbon dioxide is by far the largest cause of global warming.

Largest sources of carbon dioxide:
 * Burning of carbon-based fuels
 * Deforestation and burning grasslands for crop production



Methane
Methane is at lower concentrations, but has a stronger greenhouse effect.

Largest sources of methane:
 * Agriculture,
 * Cattle and other ruminants
 * Manure
 * Rice farming
 * Disturbance of peat lands

Nitrous Oxide
Nitrous Oxide (N20) is at low concentrations and has a strong greenhouse effect.

Largest sources:
 * Natural denitrification in soils
 * Breakdown of fertilizers

Fluorinated Gases
Fluorinated gases (F-gases) which contribute to climate change include:
 * Hydrofluorocarbons (HFC's) - used as substitutes for CFC's and HCFC's (HFC's do not destroy the ozone)
 * Perfluorocarbons (PFC's) - used in electronics and other industries
 * Sulfur Hexaflouride (SF6) - used in high-voltage switches

Changing of the weather
Global warming will cause shift in climate

An animation of how the Earth's climate would change can be found here

Generally, more hot days and fewer cool days. Tropics will get less precipitation. Polar regions will get more precipitation.

Temperate regions will shift north. Heat waves, droughts, wildfires, and storms will increase. Growing seasons are also moving poleward.

Melting of sea ice and glaciers
Rising temperatures causes sea ice and glaciers to decrease



Sea level rise
The melting of the ice sheets and glaciers causes the amount of seawater to increase. Also heating water causes it to expand.

Models estimate that sea levels will rise 0.18 - 0.59 m.

10 percent of world's population lives less than 10 m above sea level. Some island countries may no longer exist.

Wildlife
Global warming can also affect wildlife. It can affect their distribution. Some species have already migrated towards the poles.

This is a especially a threat to endangered species.

Permafrost melting
Permafrost is soil which remains frozen all year.

Melting of permafrost is a feedback mechanism. It releases methane, which increases global warming, which in turn causes more permafrost melting creating a loop.

Ocean Acidification
This effect is due to the carbon dioxide directly and not temperature change. Carbon dioxide dissolves in the ocean to create acid conditions.

This in turn has an effect on marine organisms. Acidic conditions increase the solubility of calcium carbonate in shells of shellfish, coral, etc.

Mitigation
Reducing the amount of carbon dioxide

Methods of mitigation
 * energy conservation
 * renewable energy sources
 * changing transport
 * carbon tax - taxing companies for each ton of carbon dioxide they produce
 * reforestation
 * carbon sequestering ? - capturing CO2 and then pumping it underground
 * note that we are still producing carbon dioxide, but then burying it underground
 * the technology is untested. What happens if leaks occur and will changing acidity cause problems?
 * geoengineering ??? - mega projects to reduce effects of global warming
 * examples: setting huge mirrors in outer space, adding huge quantities of iron filings to the ocean, injecting aerosols of sulfur dioxide into the stratosphere
 * problems: hugely expensive, most are not technically feasible with today's technology, may have undetermined consequences, and questions about governance

Adaptation
Measures to reduce the effects of global warming

Examples
 * Building sea walls
 * Changing crop types
 * Generating a fund to help low income countries (the most talked about adaptation measure)