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20 December 2009
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Climate change, global warming and the greenhouse effect are all
names used more or less interchangeably for the same thing, often
incorrectly.
How many times have we heard people say during a warm spell, "Must be
global warming" or during a cold snap, "Where is this global warming?"?
I must have heard them a hundred times or more, yet it is all wrong.
Yes, all wrong! Weather has nothing to do with climate and climate has
nothing to do with weather. So, let's define them, to try and make the
issue clear:
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Climate:
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The prevailing atmospheric phenomena (sun, rain, wind,
humidity etc.) of a region, averaged over many years, and
creating the biota of that region.
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Weather:
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The instantaneous atmospheric phenomena (sun, rain, wind,
humidity etc.) at one given place and time.
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Let me emphasise the difference by an analogy; a very rich man, with
all his wealth invested wisely, may not have much cash in his pocket,
while a very poor man, living on the vital minimum, may have a lot more
money in his pocket on the day he collects his benefits. The wealth of
these two men is their financial climate, while the cash in hand is
their weather. It can be a cold day in Central Africa, or it may be a
warm day in Antarctica. It can rain in the Sahara desert or there can be
a drought in Central Borneo.
Global climate is the climate of the whole planet or
the averaged climate of all regions. A heat wave over Mediterranean
countries in early August is "normal weather", just as much as snow in
the mountains in winter. Even if the heat wave, one year, hits record
daytime maxima of, say, 47°C or more, it is still weather and it is
unlikely to show any change in the climate and it certainly will have
almost no effect on the average global temperature and, even less, on
the global climate.
If the earth had an inert atmosphere, it would be a very cold,
inhospitable place, with a global average air temperature of about
-18°C. In fact, the global average temperature is between 14° and 15°C.
Why? The answer is global warming. In the hypothetical first case, all
the energy in the sun's rays striking the earth's surface would heat it
up (if the earth did not have a hot core and there were no sun, its
temperature would be close to absolute zero). However, much of this
energy would be radiated straight out again and equilibrium would be
reached at about -18°C. In reality, it is not like that, because of
global warming, without which, life as we know it could not exist. In
fact, global warming has existed for many millions of years.
To explain this, let us take the analogy of a greenhouse. All the
sun's energy passes almost uninhibited through the glass and heats up
the inside surfaces to above ambient temperature. However, glass will
not allow the long wavelength energy which the warmed surfaces could
radiate to escape, so the air inside the greenhouse also increases in
temperature. So it is with the earth, except that we are not surrounded
by glass but by certain gases which have the same effect of not allowing
the energy stored in the earth's surface to escape into outer space. The
average global temperature is in a careful equilibrium dependent on many
factors and parameters. The concentration of these "greenhouse gases"
(GHGs) is one such factor, and a very important one at that.
What are these greenhouse
gases? The most important one is water vapour, which averages about 1
per cent by volume over the planet. In terms of weather, the
concentration is extremely variable from the dry air of a sirocco wind
to a dank Scotch mist, but the average over time is very constant and is
governed largely by evaporation from the oceans and vegetation. The
quantity of water in the atmosphere is so great (about 12 trillion
tonnes) that man cannot change the overall global amount, not even by
his worst efforts, so that a natural equilibrium pertains. The next
greenhouse gas and the most important from the point of view of climate
change is carbon dioxide. The concentration of this has increased from
280 to 390 ppm in the last 125 years and this change is due to human
activities, mostly burning extracted minerals, such as coal and oil,
from where they have resided for millions of years under the earth's
surface (for a further treatment on this subject, see the essay on
Sequestration).
However, carbon dioxide and water vapour are not the only greenhouse
gases, nor even the worst ones. If carbon dioxide is given an index of
1, called the Global Warming Potential (GWP), representing the rise in
resultant temperature for a given mass, methane has a GWP of about 20 −
50, meaning it is 35 times worse. on average. Fortunately, there is only
about 0.00017 per cent of methane in the atmosphere, but that has more
than doubled in the last 150 years, again because of man's activities.
This is largely because of
leaks of
natural gas (increasing yearly), waste gases in petroleum refining,
increased areas of
rice paddies and increases in the numbers of cattle (enteric
fermentation within a single cow will produce several litres of methane
per day!), all of them resulting from human activities (on the other
hand, draining wetlands would cause a slight reduction of natural
methane). Nitrous oxide has increased from 280 to 312 ppbv (parts per
billion by volume) in the same period, relatively modest, in comparison.
However, the worst of the lot are all man-made compounds, mostly
containing fluorine. Hydrofluorocarbons (HFCs) often have GWPs between
500 and 2000, while perfluorocarbons (PFCs) may even exceed 10,000.
Happily, the concentrations of these gases are still very low, a
fraction of 1 ppbv. However,
HFC production has increased enormously
over the past two decades as a result of using them as substitutes for
CFCs, banned by the
Montreal Protocol. In particular, HFC-134a is a very popular gas for
refrigeration and air conditioning.
Let me take the example of
Cyprus, because I happen to live there and happen to have some
statistics over the past century.
It can be seen from the above
graph that the average temperature in Cyprus has increased by a little
over 1°C in the past century. The red line is the mean annual
temperature and the blue line is the average over the five preceding
years, which tends to smooth the curve. This does show that we are
suffering from a small climate change.
Over the same period, we can
see that the rainfall has dropped by as much as about 100 mm or 20 per
cent, although the fluctuations are much greater, even as much as in a
ratio of almost 4:1. This is serious, because the population, and thus
water demand, has increased by about 50 per cent since 1950, not
counting an increased usage because of better hygiene.
Although the observations and the theory closely correlate, there is
still no absolute scientific proof that the increase of greenhouse gases
due to human activities is a contributory cause of climate change. The
evidence is circumstantial, but very strong (many murderers have been
executed on much weaker evidence!). It is therefore reasonable to
discuss the ramifications of this, as if it were proven. In the unlikely
event of it being proved wrong, no harm will have resulted, only good,
so it's a double-whammy in favour of action being taken.
As can be seen from the above
graphs, Cyprus has a hotter, drier climate than it had a century ago,
even if we cannot prove that the cause is man-made. This is serious
because it means changes to our nature, especially as we are taking more
out of the land than ever before.
Recent research (2004-2005)
is tending to show the correlation between the emissions of man-made
GHGs and the resultant effect on global climate is becoming stronger.
Worse, a study by scientists at Oxford University is predicting a
greater effect on climate than hitherto believed possible, with global
temperature rises of up to a maximum of 11°C by the end of this century.
This is based on the fact that polar and oro-glacial ice is already
melting at a much faster rate that was previously forecast. If this
extreme prediction came to pass, then life on earth, as we know it
today, will become very precarious and the human population decline may
become much greater, because of famine and disease. Personally, I think
that there is much more research necessary to be able to subscribe to
the worst doomsday scenario, but we must not discount the possibility,
either.
The earth's climate and weather is the result of a delicate balance
between a host of different natural phenomena:
- the "greenhouse effect"
- solar radiation
- the sunspot cycle
- elliptical orbits of the earth and moon
- wobble of the earth's axis
- the earth's magnetic field and positional polar changes
- ocean currents
- continental drift
- atmospheric convection cells, notably the Hadley cell
- photolysis and hydrolysis of organic matter
- volcanoes
- sulfate aerosols and other dust sources
- transpiration of living organisms
- forestation
- the size of the ice caps
- and many others...
A modification of any one of these may induce rapid changes of
weather or slower changes of climate, depending on how and the length of
time of the modification. Some changes may involve negative feedback,
which will tend to restore the status quo while others may
involve positive feedback which may tend to cause a runaway effect. As a
hypothetical example of negative feedback, let us assume that the sun's
radiation increases, causing a small rise of the temperature of the
surface oceanic water; evaporation will increase, causing a heavier
water vapour loading and more clouds form; the clouds have a high albedo
and more radiation is reflected back into space, so the ocean water will
tend to cool down again. An equally hypothetical example of positive
feedback is that if a large tract of tropical rain forest were cut down
for timber or to claim farm land, there will be a very reduced mass of
vegetable matter and less transpiration will occur, resulting in lower
regional rainfall; this will result in an inability of the remaining
forest to sustain itself and it will slowly die off from the edges,
causing desertification which will encroach continually and more rapidly
until no rain forest is left.
What is sure is that the earth's regional climates do change, as is
shown by the ice ages and by evident changes of vegetation over time.
This is a perfectly natural phenomenon, usually taking many thousands of
years.
What is equally sure is that the earth's average temperature,
throughout the world, has increased by nearly 1°C over the past century
or so. Never has such a change occurred in so short a length of time,
since we have been able to follow the evolution of the earth's climate,
dating back a few thousand years. As this is coincident with the
increase of greenhouse gases caused by man's activities, the hypothesis
of the latter being causal becomes inevitable. This has caused many of
the world's most eminent atmospheric scientists to attempt to determine
whether the observations result from the supposed cause. The main way
that this has been tackled is to calculate mathematically all the
potential identified causes, outlined in the above list, and their
probable effect on the global temperature. Their results have been
published in many scientific assessments and can be summarised by:
These graphs were published by the Intergovernmental Panel on Climate
Change (IPCC) under the auspices of the United Nations Environmental
Programme (UNEP), which instigated this research. It can be seen, in
graph (a) that natural phenomena alone cannot explain the observed rise
in temperatures, especially since 1950. Man-made greenhouse gases alone
do not fit the observations, either, especially between 1930 and 1980,
as shown in (b). Combine the two, producing graph (c), and the fit is
visibly very good. Note that the model results take into account
potential tolerances, due to incomplete knowledge (e.g., the tonnage of
dust reaching the stratosphere from a violent volcanic explosion). The
models take into account the minimum and maximum values, where there are
uncertainties, therefore the grey lines in these graphs are broader than
the observations line.
Note that the red line in graph (c), between 1900 and 2000, is
similar in shape and amplitude to the blue line in the average
temperature curve for Cyprus. This shows that the changes there are
probably the same as in the rest of the world.
I don't believe it is necessary to say much more than that the
average climate change is causing several effects, some of them
potentially severe. It does not really matter whether the change is
caused by human activities, it is happening. The obvious ones have been
mentioned in the press that we are all sick and tired of hearing them:
ice cap meltings, atolls and low-lying land disappearing, increased
desertification, biota changes, increasing violent weather phenomena
etc.
The only statement that can result from this is:
if the changes are due partially to human activity, as seems most
probable, then we should do everything in our power to reduce their
effect as quickly as possible; if they are not due to this, then it will
do no harm if we try to reduce their effect. In other words, we
should do our best to restore the average climate to what it was over a
century ago.
If we wait for formal scientific proof before doing anything, then it
will be too late. The only reasonable time scale to reduce GHG emissions
is immediate or sooner.
For me, this is the most telling argument to act rapidly. If carbon
dioxide were the only problem, then the urgency would be less. The
problem is that every vehicle exhaust pipe, every power station stack,
every domestic chimney, if these are all using fossil fuels directly or
indirectly, are emitting other pollutants. These are causing diseases of
epidemic proportions. Skin and lung diseases, including cancer,
emphysema and asthma are just the tip of the iceberg, the visible
results. The invisible results are damage to the body's immune system
and a whole host of other new and old diseases find it even easier to
gain a strong foothold. These indirect costs of our fossil-fuel economy
are swingeing and are bleeding health services dry in most countries. If
we reduce carbon dioxide emissions by 20 per cent, the cost may be high
but the collectivity would save far more than it would cost.
I ask all those who are over about 50 to think back to how many kids
in your class suffered from asthma. Then ask how many kids in a class of
30 have an inhaler in their pocket today.
This report shows that, in the USA, school absence days due to
asthma in 1980-82 were 6.6 million, rising to 14.0 million in 1994-1996.
Other reports evoke a 160 percent increase in the last ten years. Other
juvenile diseases, such as severe migraines, rheumatoid arthritis and
diabetes have been following similar progressions. I am not saying that
these are all directly due to pollution from burning fossil fuels, but I
am sure that it is contributory.
Over the past few years, we have seen outbreaks of a number of
apparently new diseases or an increase in the apparent virulence of
previously known diseases. These include bird 'flu, SARS, ebola,
Creutzfeldt-Jakob disease and a number of others. Have you not thought
that the reason why these are becoming serious is not because they are
new (they have always been around in other species) but that the human
immune system is weakened and cannot fight against trans-species
transmission? I have no proof of this hypothesis, but neither can I rule
it out. What we do know is that the immune system is weaker, partly
because improved hygiene does not expose us to as many pathogens as in
the past and partly as a result of pollution-related effects.
Perhaps the most telling argument is that the World Health
Organisation estimates that 3,000,000 persons die each year from
diseases caused by pollution from energy use. At least ten times this
number receive treatment − often for long periods of time − for the same
diseases, many of them being so afflicted as being unable to work. This
is 2½ times the number of people killed or incapacitated in road
accidents and is about equal to deaths from AIDS (the propagation of
which, incidentally, may also be aggravated by energy-related pollution
reducing the body's effectiveness of the immune system).
I therefore state, quite categorically, that we cannot afford
NOT to act against fossil fuels for fear that the cost of health care
will be out of the reach of ordinary people. Health care and
insurance is the biggest economic inflationary influence in most
countries, developed and developing alike.
The Kyoto Protocol, which is designed to reduce GHG emissions, has
now entered into force. The adoption by the USA is very unlikely, as the
Bush administration has pronounced an opposition to it, for purely
selfish reasons; it is aberrant that 5 percent of the world's population
emits 28 per cent of the GHGs that cause such problems and literally
intends to do nothing to improve the situation, other than lip service.
The EU has unilaterally agreed to reduce GHG emissions by an average
of 8 percent from 1990 levels by 2008 - 2012. Within member-states, this
will vary according to a number of factors. In addition to this, if one
state exceeds its reduction "quota", it can sell the difference to other
member-states that have not reached their's, so there is some degree of
flexibility, albeit costly. This is aberrant.
Every country can and must make a contribution to reducing its GHG
emissions, even below 1990 levels, but it will require a strong will and
sacrifices from its population. The means of doing so are outlined in a
number of the other essays on this web site. It will depend on a mix of
improved public transport, changes in fuel types, especially for
electricity generation, renewable energy sources and, above all, the
will to do so by the people. However, contrary to popular opinion, I
believe that implementing radical change will actually improve the
standard of living, in the long term.
Climate change books
Climate
change in Europe
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