Climate change in the UKOTs an overview of the ... - JNCC - Defra

Sunlight
passes
through the
greenhouse
gases and
warms the
earth
Figure 6. Greenhouse effect
Source: Impetus Consulting Ltd.
The greenhouse effect works much the
same way. Energy from the sun, or solar
radiation, passes through the atmosphere
and warms the Earth’s surface. Some of
the radiation is reflected back out into
space at the level of the atmosphere.
Some reaches the Earth, is absorbed by
the ground and released as heat. Some of
this heat passes back through the atmosphere
into outer space and some is
retained by the gases in the atmosphere
and warms the Earth (Figure 6).
This natural warming is what makes the
Earth habitable for the plants, animals and
humans that have evolved there; without it,
the Earth’s average temperature would be
an inhospitable -18°C instead of the
present 14°C.
The enhanced greenhouse effect
When this natural warming process is
exaggerated or enhanced, there is cause
for concern. An increase in the concentration
of greenhouse gases in the atmosphere
results in more heat being retained
and an overall warming of the Earth’s temperature.
Although they make up a small
percentage of atmospheric gases,
changes in the concentration of greenhouse
gases have a huge effect on the balance
of natural processes.
34
Greenhouse gases
Atmosphere
Outer Space
The earth
warms up and
gives out heat,
some heat passes back out
through the greenhouse gases
but some is trapped inside
keeping the earth warm
The human factor
The core concern about climate change is
human potential to alter the climate
through activities that are a result of our
way of life and how we treat the natural
environment. There have been significant
Box 4. Human activity and
greenhouse gases
The principal greenhouse gases
that enter the atmosphere because
of human activities are:
Carbon Dioxide (CO 2 ): Carbon dioxide
enters the atmosphere through the burning
of fossil fuels (oil, natural gas, and coal),
solid waste, trees and wood products, and
also as a result of other chemical reactions
(e.g., manufacture of cement). Carbon dioxide
is also removed from the atmosphere
(or “sequestered”) when it is absorbed by
plants as part of the biological carbon cycle.
Methane (CH 4 ): Methane is emitted during
the production and transport of coal,
natural gas, and oil. Methane emissions also
result from livestock and other agricultural
practices and by the decay of organic waste
in municipal solid waste landfills.
Nitrous Oxide (N 2 O): Nitrous oxide is
emitted during agricultural and industrial
activities, as well as during combustion of
fossil fuels and solid waste.
Fluorinated Gases: Hydrofluorocarbons,
perfluorocarbons, and sulfur hexafluoride
are synthetic, powerful greenhouse gases
that are emitted from a variety of industrial
processes. Fluorinated gases are sometimes
used as substitutes for ozone-depleting substances
(i.e., CFCs, HCFCs, and halons).
These gases are typically emitted in smaller
quantities, but because they are potent
greenhouse gases, they are sometimes
referred to as High Global Warming Potential
gases (“High GWP gases”).
Source: US Environmental Protection Agency
(www.epa.gov/climatechange/emissions/index.html)