Introduction to climate change

planets and atmospheres

1. Planets and atmospheres

A planet's climate is decided by its mass, its distance from the sun and the composition of its atmosphere. Mars is too small to keep a thick atmosphere. Its atmosphere consists mainly of carbon dioxide, but the atmosphere is very thin. The atmosphere of the Earth is a hundred times thicker.


Temperature and CO

2. Temperature and CO2 concentration in the atmosphere over the past 400 000 years

Over the last 400,000 years the Earth's climate has been unstable, with very significant temperature changes, going from a warm climate to an ice age in as rapidly as a few decades. These rapid changes suggest that climate may be quite sensitive to internal or external climate forcings and feedbacks.


The greenhouse effect

3. The greenhouse effect

The Earth has a natural temperature control system. Certain atmospheric gases are critical to this system and are known as greenhouse gases.


Radiative forcing

4. Radiative forcing

Radiative forcing is the change in the balance between radiation coming into the atmosphere and radiation going out.


The main greenhouse gases

5. The main greenhouse gases

The table lists some of the main greenhouse gases and their concentrations in pre-industrial times and in 1994; atmospheric lifetimes; anthropogenic sources; and Global Warming Potential.


Mauna Loa curve

6. CO2 Concentration in the atmosphere: Mauna Loa curve

CO2 concentrations in the atmosphere have been measured at an altitude of about 4,000 meters on the peak of Mauna Loa mountain in Hawaii since 1958.


Global atmospheric concentration of CO2

7. Global atmospheric concentration of CO2

Atmospheric CO2 has increased from a pre-industrial concentration of about 280 ppmv to about 367 ppmv at present (ppmv= parts per million by volume).


CO2 emissions from industrial

8. CO2 emissions from industrial processes

This map depicts the unequal distribution of industry in the world. The significant part of carbon dioxide emissions comes from energy production, industrial processes and transport.


CO2 emissions from land use change

9.CO2 emissions from land use change

Emissions of carbon dioxide due to changes in land use mainly come from the cutting down of forests and instead using the land for agriculture or built-up areas, urbanisation, roads etc.


Emissions of CO2

10. Emissions of CO2 - selected countries (1995)

The rich countries of the world historically has emitted most of the anthropogenic greenhouse gases since the start of the industrial revolution in the latter half of the 1700s. Per capita, the significant emissions still are produced by the OECD countries


The present carbon cycle

11. The present carbon cycle

The global carbon cycle shows the carbon reservoirs in GtC (gigatonne= one thousand million tonnes) and fluxes in GtC/year.


The cooling factors

12. The cooling factors

The amount of aerosols in the air has direct effect on the amount of solar radiation hitting the Earth's surface. Aerosols may have significant local or regional impact on temperature.



13. The UN Convention on Climate Change (UNFCCC)

The United Nations Framework Convention on Climate Convention is the foundation of global efforts to combat global warming.



14. Intergovernmental Panel on Climate Change (IPCC)

In 1988, UNEP and WMO jointly established the Intergovernmental Panel on Climate Change (IPCC) as concern over climate change became a political issue. The purpose of the IPCC was to assess the state of knowledge on the various aspects of climate change including science, environmental and socio-economic impacts and response strategies.



Source: United Nations Environment Programme / GRID-Arendal