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Climate Change - What Do We Really Know?

"If things don't change, it will be your children who pay the price," President Sarkozy told an audience at a heat pump factory in eastern France, when he finally announced the much-debated carbon tax.  But, though it clearly makes sense, for social, economic and political reasons to reduce dependence on unsustainable fossil fuels, can climate change really be halted, or even influenced, by relatively small reductions in mankind’s carbon footprint, as envisaged by the governments of France and other industrialised countries?

1988 was a year of heat waves and other types of extreme weather in the USA.   James Hansen told the US Congress that increasing carbon dioxide in the atmosphere, following industrialisation in the twentieth century, had caused a “Greenhouse Effect” leading to “Global Warming”.   The United Nations founded the International Panel on Climate Change (IPCC) to study this phenomenon.    Since then Climate Science has become the hottest topic in universities around the world.   The majority scientific opinion is that human produced carbon dioxide is the main driving force of climate change.  This is known as the theory of “Anthropogenic Global Warming”.   Scientists love long words, it just means that it is all our fault.   However, there is a growing body of sceptical scientists who argue that twentieth century warming was mainly due to natural cycles in the climate, and that the more apocalyptic predictions are wildly exaggerated.

Gases like carbon dioxide, methane and water vapour absorb and re-emit infrared energy.  In this way the atmosphere acts as a blanket capturing the heat from the sun and warming the planet.   Without this greenhouse effect the Earth would be 33C cooler, and hence uninhabitable.   The IPCC has calculated that carbon dioxide contributes about 10% of the greenhouse effect, the rest being mainly due to water vapour.

During the twentieth century, the concentration of carbon dioxide in the atmosphere rose by 50%.   At the same time the average global temperature increased by 0.8C.   Carbon dioxide concentration in the atmosphere continues to rise due to industrial activity and the alarmist prediction is that, if this is left unchecked, runaway global warming will lay waste to the planet causing frequent environmental disasters.   Temperatures peaked in 1998 since when they have been more or less constant with a slight trend to decrease.  We do not really know if they will start to increase again.

Glaciers retreated and the Arctic sea ice area reduced during the twentieth century.   There are predictions that mountains and the Arctic will be ice-free by the end of the century.   The outgoing head of Greenpeace admitted in a recent BBC interview that these stories are exaggerations but justified them by saying that we need to inject some urgency into the debate.   Glaciers have been retreating since 1800, well before the age of industrialisation and the retreat is slowing.   Arctic sea ice area has reduced by about ten percent but started to recover during the last few years.   It is worth noting that the sea ice melts every summer and refreezes in the winter.   The minimum ice area is in September, when politicians are taken to witness the disappearing ice and stories of opening sea-lanes appear in the press.

As President Sarkozy announces a new carbon tax Dr. Geoffrey Dobson examines how much of the Greenhouse Gas debate is just hot air

The twentieth century is not unique in undergoing climate change.   Over geological history the earth has been through many cycles of ice age and warm interglacials.   There is no guarantee that the current interglacial will last forever.   

During the last 2000 years there have been minor climate cycles.   Around AD1000 we had the “Mediaeval Warm Period” when Greenland became ice-free and was settled by the Vikings.   This was followed between AD1500 and AD1900 by the “Little Ice Age” when rivers like the Thames regularly froze over during the winter.     

The intensity of the sun must influence climate to some extent.  Ice ages may be caused by irregularities in the earth’s orbit around the sun.   During the Little Ice Age the sun was relatively inactive with no sunspots for many years.  The sun was particularly active during the twentieth century but is currently entering a quiet spell.

Ocean currents have a strong effect on local climates.   There is a Pacific Ocean Oscillation between El Nino (a warm current running towards America) and La Nina (the reverse).   There is also a North Atlantic Oscillation in sea temperatures.   Some oceanographers think that the retreat of the Arctic sea ice has more to do with the variation of ocean currents than with global warming.

Volcanoes have a mixed effect on climate.   After a major eruption, the dust cloud thrown into the upper atmosphere partially obscures the sun leading to global cooling.   The eruption also emits large quantities of carbon dioxide adding to the greenhouse effect.

The most contentious issue between alarmists and sceptics is the question of feedback.   Positive feedback increases warming, while negative feedback reduces it.   Increased water vapour in the atmosphere and reduced reflection from melting ice caps will give positive feedback.   However, increased water vapour will also increase cloud cover, giving negative feedback.  

Greenhouse warming caused by a doubling of atmospheric carbon dioxide alone will be approximately 1C.  Climate scientists introduce strong positive feedback to increase this figure to between 3C and 7C.   All computer climate models include strong positive feedback in their predictions for warming by the end of the century.

Sceptics argue that historical evidence shows that overall feedback in the atmosphere is weakly negative.   They conclude that warming due to the greenhouse effect by the end of the century will be between 0.1C and 0.3C, and that this amount of warming is insignificant compared to the natural cyclic variation in the climate.

The enormous difference in calculating feedback provokes intense argument that still goes on today.   The difference between the two theories will not be resolved by actual climate observations for another 30 to 50 years, by which time, alarmists tell us, it will be too late to do anything about it.   Some environmentalists have argued that whether or not we believe the more apocalyptic predictions, it would be prudent to cut carbon dioxide emissions now by reducing fossil fuel consumption just in case the alarmists are right.   Most western governments appear to accept this argument.   

In any case there are good reasons to reduce our consumption of oil and gas.   These are limited commodities that are beginning to run into a deficit of supply over demand as economies like India and China expand rapidly.   There are large reserves of coal, but using these will create pollution problems.  The UK in particular faces urgent decisions about electricity generation.   Unless we start building new power stations now, the lights will start to go out round about the year 2016 as old power stations shut down.   To do this in a non fossil fuel way will involve a massive development of windmills and tidal barriers despoiling the landscape with unpredictable environmental effects, or building a new generation of nuclear power stations.   France faced up to this problem years ago and went nuclear.   One thing is certain, we cannot say no to everything.

“It isn’t easy being green” (Kermit the frog).

Dr. Geoffrey Dobson lives in the Pas de Calais  and writes on a number of science related topics.  This is a very condensed and simplified version of one of his articles.  

The use of fossil fuels can pollute the atmosphere with many harmful emissions - not just carbon dioxide

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Sarkozy has introduced a Carbon Tax