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 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
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 is the change in the balance between radiation coming
into the atmosphere and radiation going out.
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.
CO2 Concentration in the atmosphere: Mauna
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
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 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.
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 - 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
The global carbon cycle shows the carbon reservoirs in GtC (gigatonne=
one thousand million tonnes) and fluxes in GtC/year.
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.
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.
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.