MAINSTREAMING CLIMATE CHANGE ADAPTATION IN AGRICULTURAL EXTENSION
Let us now look at a cause of climate change. The „greenhouse effect‟ is
understood to be the main cause of climate change in recent decades and is
predicted to be what will cause changes in climate. The term „greenhouse effect‟
is used simply because the process is a bit similar to the way a greenhouse
heats up. In other words we can think of the world and its atmosphere as being
similar to a big greenhouse which the sun heats up.
Ozone gas (O3) is found mostly at altitudes of 20-35 km in the Stratosphere –
forming the ozone layer. At ground-level it is extremely dangerous to humans,
damages plants and is a greenhouse gas.
However, in the Stratosphere it plays an essential role in enabling life by filtering
the Sun‟s harmful ultraviolet radiation (UV). This protective layer was becoming
damaged by chemicals such as Chlorofluorocarbons (CFC‟s). An international
agreement called The Montreal Protocol was created to prevent any further
damage. This was signed in 1987 and in 1990 a complete phase-out of these
harmful substances was adopted.
SLIDE 5 – The greenhouse effect
- Sunlight (short wave radiation) passes through the atmosphere and
warms the Earth‟s surface. This heat is re-radiated out towards space
as long wave radiation
- Most outgoing heat is absorbed by greenhouse gas molecules and re-
emitted in all directions, warming the surface of the Earth and the lower
atmosphere
- Greenhouse gases include C02, Methane, N20
Gases that we call Greenhouse Gases (GHG's) behave differently to other
gases. They block some outgoing long-wave infrared from easily leaving our
atmosphere. So some heat cannot escape from the atmosphere back out to
space. The GHGs act a bit like a blanket and the atmosphere warms up.
Simply put, without greenhouse gases, or the greenhouse effect, the earth would
be a frozen planet - incapable of sustaining life as we know it. There would be
no plants, no trees, no animals, just frozen ice and stone. Greenhouse gases
are essential to sustain life as we now know it. With no (or just a little) change to
SLIDE 6 The affect on the weather
- The sun can only heat part of the atmosphere at any one time, so the
atmosphere is constantly trying to readjust
- Plus the Earth is spinning & the atmosphere and ocean can interact
- Everything mixes together into a highly complex, chaotic system to give
day to day weather systems
the amount of GHGs in the atmosphere the temperature remains fairly similar for
A Training Manual on Use of Climate Information and Vulnerability and Capacity Assessment for
Agricultural Extension Staff in Zimbabwe
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