Global Warming? Then Why Is It So Cold?

Introduction

The last two winters have seen the heaviest snow and the lowest temperatures across the Northern Hemisphere in many years. This, of course, fills the hearts of climate change sceptics with great delight, as they cling to the old tagline, labelling the drastic changes in temperature simply as “global warming”. The following article examines the simple science behind the cause and predictions for climate change and investigates why scientists have for many years insisted that climate change actually means long term global cooling.

Recording of surface temperatures began in 1860 and public awareness of human-induced climate change was raised in the early 1970’s, when it was observed that the Earth had been experiencing a period of cooling. Since 1988, the IPCC (International Panel on Climate Change) has been the recognised scientific organisation responsible for global research and forecasts on climate change as well as coordinating policies accordingly.

Global Warming

Greenhouse gases absorb infrared radiation (heat), which occurs when sunlight striking the Earth’s surface is reflected back towards space. Without interference, the temperature of the Earth’s surface should be reasonably constant, since the amount of energy from the sun and the amount of energy radiated back into space should be roughly the same. However, an increasing amount of undispersed gases in the atmosphere results in the Sun’s heat being absorbed, thus raising the surface temperature of the Earth. Many of these gases exist naturally, while some are solely man-made. Although the majority of the gases in the atmosphere are derived from natural sources and cause no harm to the environment, the accelerating rate at which they are being generated holds responsibility for the “Greenhouse Effect” and the apparent rise in the Earth’s climate.

Carbon Dioxide is the primary contributor to greenhouse gases (CO2), which is formed by the burning of fuels to generate energy for requirements such as heating, lighting and travel and represents 60% of greenhouse gases. The current concentration of CO2 in the atmosphere is approximately 375 parts per million. However, in recent times, scientists have discovered that levels of Methane (CH4) in the atmosphere as high as 15% of the total indicates another serious threat. Approximately 49% of the emissions are generated by agriculture, with the majority of that figure being a direct result of dairy farming. It is estimated that there is a population of 1.4billion cows worldwide, each producing 500 litres of methane per day, totalling an amount that has tripled in the last two centuries. Other gases come in the forms of nitrous oxide, which is the third most important human-induced gas and also CFC’s, whose use was finally banned over much of the world, after widely reported proof of the gas’s contribution to ozone depletion.

In recent years, the scientifically accepted illustration of the Earth’s average temperature over the last thousand years has appeared in the form of paleoclimatologist Michael Mann’s “Hockey stick graph”, which has been widely used by the IPCC. The graph, so named for its relatively flat line for the first 900 years and subsequent sharp rise similar to the shape of an ice hockey stick, is calculated prior to 1860 by use of “proxy” temperature records, such as tree rings, ice cores, lake sediments and isotopic ratios of corals.

However, more recently, Mann’s graph has come under fire from global warming sceptics, who argue that the data is as flawed as the methods used to retrieve it. For example, the emissions of the 300 year “Little Ice Age” from 1550 and the “Mediaeval Warm Period” in the graph, which are widely accepted historical events, are for some, evidence enough that the data is simply incorrect. This, combined with arguments over the reliability of the proxy data, particularly tree rings, allegations of data “smoothing” and Mann’s initial refusal to part with the computer program he used to compile the graph, made it a target for attacks within the scientific community.

Nevertheless, many scientists concur with the data, finding it to be in line with information derived from other means such as by satellite and, as the IPCC’s chosen model for climate change, Mann’s findings continue to be recognised as the standard. Studies presented in many books and journals are based on this information.

The average surface temperature of pre-industrial Earth is 14.8 °C and it was observed by the mid 20th century that average temperatures had increased by about 0.25 °C between 1880 and 1940. The period of cooling of 0.2 °C between 1940 and 1970 coincided with new data showing the level CO2 in the atmosphere, which was increasing considerably. At that point, it was predicted that the concentration of CO2 would double, resulting in a global temperature rise of 2 °C.

Statistics from NASA scientists indicate that the degree of global warming over the last 30 years surpasses that of any equivalent period and 2003 saw new records set in the Arctic region, where inconsistencies above 3 °C were shown for land and water temperatures. More recent studies show that 2005 was the warmest year on record. Prior to this, 1998 held the title of warmest year, with the IPCC declaring, “it is likely that the 1990s was the warmest decade and 1998 the warmest year during the past thousand years” (New Scientist, 18 March 2006).

With mankind showing no signs of reducing its dependence on CO2-emitting fossil fuels, according to the IPCC, the future looks warm. A 2001 IPCC forecast shows that doubling CO2 levels will result in temperature increases between 1.4 and 5.8 °C. The report, based on a computer-generated climate predictor, known as a “general circulation model” or GCM, lists best and worst case scenarios, as shown:

High Forecast: 5.8 °C
Middle Forecast 3.6 °C
Low Forecast 1.4 °C
(Christopherson – Geosystems, 2006)

This data shows a potential surge from the Earth’s current temperature of 14.8 °C to between 16.2 and 20.6 °C.

The consequences of such an increase are well known. Already, as climate alters, global precipitation is being significantly transformed. More or less rain and changing temperatures in various regions is responsible for crop failure and shifts of preferred habitats in a variety of plants and animals. Ultimately, this can cause the more vulnerable among the population starvation or displacement in the absence of sustainable agriculture.

NASA scientists have already announced that Greenland’s ice sheet is diminishing by 1m per year. Glacial ice accounts for 85% of the Earth’s freshwater and totals 24,000,000 km3. These ice shelves hold the responsibility of retaining grounded continental ice and so, once melted, there is the possibility of a surge of continental ice, dangerously raising the sea levels.

The IPCC’s forecasts for the rise in sea level this century are as follows:

High Forecast: 0.88m
Middle Forecast 0.48m
Low Forecast 0.09m
(Christopherson – Geosystems, 2006)

Even if the release of greenhouse gases is stabilised, these rises could continue beyond 2100. Furthermore, although these figures may appear minimal, a 0.3m rise in sea level is capable of resulting in a shoreline retreat of 30m.

The melting of Arctic icecaps and the subsequent influx of freshwater into the oceans offers a new threat with effects seemingly opposing those discussed so far.

Global Cooling

Considering the close proximity of much of Western Europe to the Arctic, it might be expected that the regions temperatures would be lower. However, yearlong temperatures remain comparatively high and surprisingly, temperatures on the southwestern coast of Iceland never dip below freezing.

The reason for the relatively high temperatures is the Gulf Stream, which operates as a result of a negative feedback mechanism, in response to rates of evaporation and latent heat transfers. The stream carries warm water into the North Atlantic from the East Coast of North America and generates warm winds that raise the temperature of Northern Europe by 5 to 10 °C. Upon reaching the North Atlantic and cooling, the water sinks downwards and, acting as a huge oceanic conveyor belt, returns to the tropics. The sinking of the water occurs where the water is cooled, increasing its density. The degree of the waters density is determined by its salinity, rendering it a somewhat fragile system in the face of gigantic freshwater icecaps.

Although there is far less information regarding the potential outcome of a surge of freshwater into the Gulf Stream, the worst possible consequence offered by scientists is that of Europe entering into an ice age.

However, scientific findings suggest that at the end of the last ice age, lakes collecting meltwater purged a sufficient amount of freshwater into the North Atlantic to halt the stream. Known as the “Younger Dryas” era and lasting for around 1200 years some 12,000 years ago, the events did not plunge Europe into another ice age. Nonetheless, it is also believed that the “Little Ice Age, which dropped the temperature sufficiently to freeze the River Thames in London, may have been as a result of deceleration of the Gulf Stream.

A recent study of ocean circulation in the North Atlantic by the Southampton Oceanography Centre has showed a reduction of the stream by 30%. This alone could be a drop sufficient to cool the United Kingdom by 1°C and Scandinavia by 2°C. However, this decrease in temperature has not yet occurred and scientists speculate that this may be due to the counteracting effect of global warming.

Even though research on global cooling is still in its infancy compared to that of global warming, it is estimated that the stream may halt in as little as 20 years and not recover for many hundreds of years.

Conclusion

Although sceptics argue that the recent dramatic climate change is part of a series of natural cycles, from the evidence presented, it is undeniable that the Earth is experiencing unprecedented rises in its temperature.

The relatively minor changes required to influence the climate on a massive scale appear to already be underway and it has been shown that the Arctic icecaps are reducing significantly. Further small temperature rises can only add to the depletion of the ice and subsequently, the gigantic abandonment of freshwater into the Atlantic seems unavoidable.

The apparently simple science used to determine the machinery of the Gulf Stream leaves little room for argument that when, injected with a mass of freshwater, it will slow significantly or even cease altogether.

Therefore, it may be reasonable to expect that temperatures will continue to rise in the predicted patterns until sufficient to melt substantial amounts of freshwater into the sea.

Then it will be cold.

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