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- Climate
change is not happening.
False. Climate change is a reality. The IPCC synthesis report
2001, shows that the earth warmed between 1900 and 1940, then
subsequently cooled between 1941 and 1965, but surface temperatures
have been warming ever since. Data from millions of thermometer
measurements taken from all over the world from as far back
as 1860, allow calculation of average surface air temperatures.
This data is believed to be the most useful when describing
the state of the global climate. It can be seen that 1998
is the warmest year on record, with the ten warmest all occurring
since 1990.
- Climate change and the loss
of the ozone layer are not the same thing.
True. Climate change and the loss of the ozone layer are
two different problems that are not very closely connected.
The largest contributor to global warming is carbon dioxide
gas released when coal, oil, and natural gas are burned. CFCs,
gases which cause stratospheric ozone depletion, play only
a minor role in climate change. The depletion of the stratospheric
ozone layer, including the ozone hole, is a serious environmental
problem because it causes an increase in ultraviolet radiation
which can harm people, animals, and plants. This is a different
problem from the problem of climate change.
- Climate change is
nothing to do with humans.
False. It is true that the world has experienced
warmer or colder periods in the past without any interference
from humans. The Earth's climate is complex and influenced
by many things - particularly changes in the Earth's orbit
in relation to the Sun, as well as volcanic eruptions and
variations in the energy being emitted from the Sun. But even
when we take all these factors into account, we cannot explain
the temperature rises that we have seen over the last 100
years.
So what is causing this increase in average global temperature?
The natural greenhouse gas effect keeps the Earth around 30°C
warmer than it would otherwise be and, without it, the Earth
would be extremely cold. It works because greenhouse gases
such as carbon dioxide, methane, but mostly water vapour,
act like a blanket around the Earth. Any increases in the
levels of greenhouse gases in the atmosphere mean that more
heat is trapped and global temperatures increase - an effect
known as 'global warming'. It has been alleged that the increased
level of carbon dioxide in the atmosphere is due to emissions
from volcanoes, but these account for less than one per cent
of the emissions due to human activities.
- Carbon dioxide only makes up a small part
of the atmosphere and is responsible for global warming.
True. Carbon dioxide only makes up a small
amount of the atmosphere, but even in tiny concentrations
it has a large influence on our climate.
The properties of greenhouse gases such as carbon dioxide
mean that they strongly absorb heat a fact that can be easily
demonstrated in a simple laboratory experiment. While there
are larger concentrations of other gases in the atmosphere,
such as nitrogen, because they do not have these heat trapping
qualities they have no effect on warming the climate whatsoever.
Water vapour is the most significant greenhouse gas. It occurs
naturally, although global warming caused by human activities
will indirectly affect how much is in the atmosphere through,
for example, increased evaporation from oceans and rivers.
Humans have been adding to the effect of water vapour and
other naturally occurring greenhouse gases by pumping greenhouse
gases such as carbon dioxide into the atmosphere through,
for example, the burning of fossil fuels and deforestation.
Before industrialization carbon dioxide made up about 0.03
per cent of the atmosphere or 280ppm (parts per million).
Today, due to human influence it is about 380ppm. Even these
tiny quantities have resulted in an increase in global temperatures
of 0.75ºC.
- Rises in CO2 occur after global warming,
not before.
False. It is true that the fluctuations
in temperatures that caused the ice ages were initiated by
changes in the Earth's orbit around the Sun which, in turn,
drove changes in levels of carbon dioxide in the atmosphere.
The reasons for this are partly because the oceans emit carbon
dioxide as they warm up and absorb it when they cool down
and also because soil releases greenhouse gases as it warms
up. These increased levels of
greenhouse gases in the atmosphere then further enhanced warming,
creating a positive feedback'.
In contrast to this natural process, we know that the recent
steep increase in the level of carbon dioxide - some 30 per
cent in the last 100 years - is not the result of natural
factors. This is because, by chemical analysis, we can tell
that the majority of this carbon dioxide has come from the
burning of fossil fuels. And, carbon dioxide from human sources
is almost certainly responsible for most of the warming over
the last 50 years.
-The sun getting hotter is changing the temperature.
False. Changes in the Sun's activity influence
the Earth's climate through small but significant variations
in its intensity. When it is in a more active' phase as indicated
by a greater number of sunspots on its surface it emits more
light and heat. While there is evidence of a link between
solar activity and some of the warming in the early 20th Century,
measurements from satellites show that there has been very
little change in underlying solar activity in the last 30
years there is even evidence of a detectable decline and so
this cannot account for the recent rises we have seen in global
temperatures.
Over the first part of the 20th Century higher levels of solar
activity combined with increases in human generated carbon
dioxide to raise temperatures. Between 1940 and 1970 the carbon
dioxide effect was probably offset by increasing amounts of
sulphate aerosols in the atmosphere, and a slight downturn
in solar activity, as well as enhanced volcanic activity.
During this period global temperatures dropped. However, in
the latter part of the 20th Century temperatures rose well
above the levels of the 1940s. Strong measures taken to reduce
sulphate pollution in some regions of the world meant that
industrial aerosols began to provide less compensation for
an increasing warming caused by carbon dioxide. The rising
temperature during this period has been partly abated by occasional
volcanic eruptions.
- The impacts of Climat Change are
exaggerated.
False. Under one of its mid-range estimates(*),
the Intergovernmental Panel on Climate Change (IPCC) - the
world's leading authority on climate change - has projected
a global average temperature increase this century of 2 to
3 ºC. This would mean that the Earth will experience
a larger climate change than it has experienced for at least
10,000 years. The impact and pace of this change would be
difficult for many people and ecosystems to adapt to.
However the IPCC has pointed out that as climate change progresses
it is likely that negative effects would begin to dominate
almost everywhere. Increasing temperatures are likely, for
example, to increase the frequency and severity of weather
events such as heat waves, storms and flooding.
Furthermore there are real concerns that, in the long term,
rising levels of greenhouse gases in the atmosphere could
set in motion large-scale and potentially abrupt changes in
our planet's natural systems and some of these could be irreversible.
Increasing temperatures could, for example, lead to the melting
of large ice sheets with major consequences for low lying
areas throughout the world.
And the impacts of climate change will fall disproportionately
upon developing countries and the poor those who can least
afford to adapt. Thus a changing climate will exacerbate inequalities
in, for example, health and access to adequate food and clean
water.
- Computer models which predict the future
climate are unreliable.
False. Modern climate models have become
increasingly accurate in reproducing how the real climate
'works'. They are based on our understanding of basic scientific
principles, observations of the climate and our understanding
of how it functions.
By creating computer simulations of how different components
of the climate system - clouds, the Sun, oceans, the living
world, pollutants in the atmosphere and so on - behave and
interact, scientists have been able to reproduce the overall
course of the climate in the last century. Using this understanding
of the climate system, scientists are then able to project
what is likely to happen in the future, based on various assumptions
about human activities.
It is important to note that computer models cannot exactly
predict the future, since there are so many unknowns concerning
what might happen. Scientists model a range of future possible
climates using different scenarios of what the world will
'look like'. Each scenario makes different assumptions about
important factors such as how the world's population may increase,
what policies might be introduced to deal with climate change
and how much carbon dioxide and other greenhouse gases humans
will pump into the atmosphere. The resulting projection of
the future climate for each scenario, gives various possibilities
for the temperature but within a defined range.
While climate models are now able to reproduce past and present
changes in the global climate rather well, they are not, as
yet, sufficiently well-developed to project accurately all
the detail of the impacts we might see at regional or local
levels. They do, however, give us a reliable guide to the
direction of future climate change. The reliability also continues
to be improved through the use of new techniques and technologies.
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