THE BREAKDOWN OF CLIMATE

HUMAN CHOICES OR GLOBAL DISASTER?

PETER BUNYARD

FLORIS BOOKS            1999

PART III

Chapter 3: Ice Ages and Greenhouse Gases (Continued)

Carbon dating

• Between 1850 and 1986, the burning of fossil fuels released nearly 200 gigatonnes of carbon into the atmosphere and deforestation to convert land for agriculture added another 120 gigatonnes.
• The current concentrations of carbon dioxide indicate that almost half of these emissions are still in the atmosphere. For the past decade, we have been emitting 7.5 gigatonnes of carbon in the form of carbon dioxide each year, an amount close to 1% of total atmospheric carbon dioxide.
• It may be 250 years before a year’s extra carbon dioxide is finally removed.

Photosynthesis

• Photosynthesis across the globe mops up 10% of the atmosphere’s carbon dioxide each year. If nothing happened to replace that carbon, then in a matter of a decade no carbon dioxide would be left in the atmosphere and photosynthesis as we know it, would grind to a halt.
• The oceans contain 50 times more carbon dioxide than the atmosphere but bubbling-out is a slow process and certainly not as fast as the uptake of carbon dioxide by vegetation.

Respiration

• Charles Keeling, at the Mauna Loa laboratory, played a pivotal role in alerting us to the global dynamics of photosynthesis and respiration; rather than obtaining a straight line of carbon dioxide concentrations during the months of the year, the line followed a regular, though oscillating path, with an upward pulse that reached its peak in May and its trough in October.
• In 1958 carbon dioxide levels had reached 315 ppmv. Forty years later, levels were up 50 ppmv. The annual pulse raises the concentration by 7 ppmv in May, from its low in October, a demonstration of seasonal cycles of growth and decay, therefore of photosynthesis and respiration, the trend being ever upward.

Glaciers and fossils

• Analysis of air bubbles trapped in the glacier ice of Greenland and Antarctica not only confirms the measurement of carbon dioxide from Mauna Loa, but indicates that the pre-industrial levels of carbon dioxide during the 18^th century were around 275 ppmv, and that over the past 160,000 years the levels of the gas have never exceeded 300 ppmv until the mid twentieth century.

Isotopes and ice caps

• Climatologists believe they can measure how much water existed as ice at any moment during the past 160,000 years.

The Vostok ice core

• The conclusion that carbon dioxide concentrations are rising at rates and to levels that are unprecedented over the past 250,000 years depends extensively on data derived from Antarctic ice cores.
• The Vostok core has provided some of the most concrete evidence of atmospheric changes that have taken place over two ice ages and interglacials. Fluctuations of carbon dioxide closely match the rise and fall of temperature.
• Ice cores from Greenland indicate changes of around 50 ppmv in the concentration of carbon dioxide that seem to have taken place in less than 100 years and are associated with abrupt temperature changes of as much as 5ºC.

Tropical glaciers

• Glaciers offer an advantage over the polar ice caps in that they also exist in high mountain ranges in the tropics and provide some indication of past climates in equatorial rather than polar regions.
• When rainfall was high in coastal areas, civilizations thrived there; when rainfall gave way to drought, the civilization collapsed.
• Highland civilizations thrived when the coast was in the throes of drought, and did less well when it was raining on the coast.
• In such marginal environments switches in climate appear to have direct consequences on human survival and therefore on cultures.

Global warming potentials

• Aside from water vapour, carbon dioxide is the most important greenhouse gas in the atmosphere, with its concentration more than 100 times greater than that of methane, and 1000 times greater than that of nitrous oxide.
• When water vapour is taken into consideration, CO₂ is responsible for approximately ¼ of the greenhouse effect.
• Each greenhouse gas makes its own particular contribution to global warming until washed out by rain or broken down by sunlight.
• Global warming potentials are likely to increase in the future as carbon dioxide builds in the atmosphere due to saturation effects. Relative to carbon dioxide the effects of the other greenhouse gases will proportionately increase.

Chapter 4: Winds, Volcanoes and El Niňo

Air circulation

• The Equator receives nearly 2½ times more energy than the poles over the course of the year. If that energy were not distributed, the Equator would be 14ºC warmer and the North Pole 25ºC colder than at present.
• The atmosphere, with considerable help from the oceans, effects the transfer of energy from the Equator to the poles, thereby generating the world’s climate in the long term and its weather in the short term.

Blown off course

• Rossby realized that a narrow band of strong westerly winds, with speeds of 200 kph and more, was circumnavigating the planet in the middle latitudes – the jet streams that pilots encounter.
• The vortex is extraordinarily deep, carrying a mass of air that may range from 2km above the surface to as much as 20km above the Earth.

Jet streams

• Jet streams can spread the ash and sulphurous material from an erupting volcano around the Earth within a week, thereby potentially affecting the weather on a planetary scale.
• The usual path of the polar front jet stream over Britain is from south-west towards the north-east, which accounts for much of Britain’s more miserable weather.
• This is occasionally alleviated by anticyclones that block the jet stream forcing it southwards, so that while Britain bathes in hot, dry weather, such as the summers of 1976, 1989 and 1995, regions further to the south are drenched in unseasonable rain.

El Niňo

• The cycle of one El Niňo every few years fitted the pattern of a system that released its energy in a single event. However, the cycle has changed dramatically over the past 30 years, with four consecutive El Niňos since 1990, and more El Niňos than ‘normal’ since 1976.
• Researchers believe that the last El Niňo sequence, which ended in June 1995 only to restart with a vengeance in 1997, has been the longest for about 2000 years.
• The weather patterns that prevailed during abrupt cooling of the northern hemisphere in the last ice age, share many features with the El Niňo of 1982-83 – dry weather over the tropics and heavy precipitation over the mid-latitudes.
• The latest El Niňo involved massive releases of energy from the Pacific Ocean. The first signs in 1997 were a sudden warming of the tropical waters off the coast of Peru by as much as 6ºC, combined with violent downpours and landslides in what is one of the driest deserts in the world – the Atacama.
• From early July to August 1997, heavy rains over eastern Europe filled rivers to bursting point and sent waters swirling through towns, villages and farms.
• In September in East Kalimantan, southern Borneo, fires raged out of control and for weeks clouds of acrid smoke drifted across Malaysia, Thailand and the Indonesian islands, blocking out the sun and making life a misery for millions of people.
• There were devastating hurricanes on the Mexican west coast in the autumn, followed by ferocious typhoons. The same week saw a 150 mph tornado in Florida, and landslides in the Azores brought on by torrential rain, followed by violent storms over Spain and Portugal, and unprecedented December floods.
• Lack of rain was widespread over South-East Asia in 1997 and by the end of October, Papua New Guinea was in the throes of a terrible drought that threatened  much of the population with starvation.
• It is no coincidence that the amount of carbon dioxide accumulating in the atmosphere in 1998, as measured at Mauna Loa, jumped upwards by one seventh compared to the previous peak.

The harbinger of worse to come

• El Niňo hits hardest where we have already begun to degrade the environment. The horrendous damage and loss of life in Honduras and Nicaragua resulting from Hurricane Mitch, were largely the result of deforestation which left soils exposed and vulnerable to sheet erosion and massive landslides.
• Honduras is still continuing to destroy its native upland forests at the rate of 80,000 hectares per year. The situation is even worse in Nicaragua where 150,000 hectares of forest are destroyed each year as a result of commercial timber extraction, the advancing agricultural frontier and slash and burn farming. The country has lost nearly 60% of its forest cover in the last 50 years.

Trade winds and Pacific currents

• We have experienced two El Niňos over the past 15 years that appear to be stronger than any recorded over the past five centuries, and the suspicion is bound to arise that exceptional El Niňos must be a consequence of global warming.
• If El Niňos become the norm they will undoubtedly play havoc with our expectations of climate and weather patterns. Agriculture could be jeopardized; where before we had plenty of rain we could experience arid conditions and, vice versa.

Causes of El Niňo

• Atmospheric moisture has risen by 5% per decade since 1973 over the United States and by 10% over temperate regions of the northern hemisphere, providing a significant increase in energy to drive storms and El Niňos.
• The Pacific Ocean has warmed by at least 0.5ºC over the past century.

Deforestation and El Niňo

• Tropical forests are responsible for prodigious releases of energy in the form of water vapour, equivalent to 6 million atomic bombs every day over the Amazon Basin.
• This energy is transferred by global circulations from the Equator up into the higher latitudes, and is crucial for the movement of air masses.
• Rainforests act as thermal machines and as regulators of atmospheric and oceanic systems which control climate.
• The wholesale destruction of tropical forests over the last 40 years has seriously jeopardized the efficiency with which energy is transferred from the Equator to higher latitudes.
• Forest destruction in the Tropics is changing climate and weather systems in new and unpredictable directions.
• A series of powerful El Niňos would play havoc with tropical agriculture, with vast areas of the Tropics becoming desert.
• It is now disturbingly apparent that the destruction of the world’s tropical rainforests, and of the Amazon in particular, will have a devastating effect on climate.

The Amazon as heat pump

• Without in tact forest the amount of solar energy carried away towards higher latitudes is reduced, causing significant cooling over temperate zones such as Britain.
• Combined with the seizing up of the Gulf Stream the loss in heat transfer would be devastating to the climate of Northern Europe and Scandinavia.
• The energy carried away as latent heat each year from the Amazon is 40 times the total energy humans use worldwide for industrial and agricultural activities.

Accelerating destruction

• 17 million hectares of tropical forests are being destroyed each year. More than 50 million hectares of the Brazilian Amazon have gone in recent decades.
• Once the Amazon rainforest in Brazil is wholly destroyed, the world will discover too late that it has pulled down one of the most important components of a stable, global climate.

Clouds and forests

• Trees emit isoprenes that act as the focal point from where water vapour condenses as droplets.
• The forest is largely responsible for the recycling of water over land as well as maintaining the hydrological cycle. In addition a tropical rainforest distributes solar energy to other parts of the planet and makes the planet a more habitable place.

Hurricanes, typhoons and tropical storms

• In one day a full-blown hurricane may unleash the energy equivalent to 500,000 Hiroshima-size atomic bombs.
• Hurricanes and typhoons form over oceans where the sea temperature exceeds 26ºC for a considerable depth.
• The eye of the storm is an area of subsiding air 30-50 km in diameter, which warms as it descends. In general such storms last from one to two weeks.
• Global warming is likely to greatly increase the area of ocean with temperatures above 26ºC, therefore increasing the number and intensity of tropical storms.

Chapter 13: The Impact of Climate Change

• We have remained woefully ignorant of the impact of what we are doing to the planet.
• Global warming models suggest that once carbon dioxide levels in the atmosphere have doubled, soils in southern Europe may lose 50% of their moisture, and soils in northern Europe 30%. Scientists fear that the pH of European soils will plunge down to four or less with consequences for vegetation and aquatic life.

Warming feedbacks

• The latest reports from the Hadley Centre of the UK Met Office state clearly that worldwide we are sliding inexorably into a period of global warming.
• Within 50 years we will face climatic disturbances that could even put our future at risk.

Terrestrial sinks and sources

• In 50 years we have lost approximately half of the world’s tropical forests and, at the rate we are going it will not be long – possible as little as 30 years – before we have lost the rest.
• Global warming could also be on the verge of triggering the destruction of the West Antarctic ice sheet, which in its entirety could cause a worldwide rise in sea levels more than 10 times the current predictions.
• If greenhouse gases increase at their current rate of 1% a year over the next 50 years, some regions in the Arctic Circle would warm by as much as 6ºC compared with today – 2 to 3 times greater than the global average.

Losing the ocean sinks

• The circulation of the oceans is vital in both the uptake of carbon dioxide from the atmosphere and the transport of heat from the Equator to the high latitudes.
• As the oceans warm the solubility of carbon dioxide drops significantly. Instead of a vital sink for carbon dioxide the oceans could turn into a net source.
• With 50 times more carbon dioxide in the oceans than in the atmosphere, it takes no more than a subtle change in the exchange between the oceans and atmosphere for greenhouse gas levels to double.

Clouds and global warming

• The energy pumped into the atmosphere by the Amazon rainforest is practically equivalent to the energy transported northwards by the Gulf Stream.
• If the pattern of watering is broken, for instance by a succession of El Niňos, then the Amazon rainforest is doomed.

Living on a knife-edge

• The general circulation models, although vastly improved in recent years, do not come close to evaluating the true impact of our activities on global climate.
• The issue is not just greenhouse gases and global warming, it is also our destruction of vital ecosystems.
• For every hectare of improved land for modern intensive agriculture we leave another behind that has become desert.

The consequences of climate change

• We now face the danger that many interconnected, though separate positive feedbacks could be triggered at the same time, all acting synergistically to exaggerate the impacts of the other. It is most unlikely that we have identified all of them.
• A fourfold increase in the greenhouse gases from pre-industrial times appears inevitable if we carry on as we are. That will take us to 1100 ppmv – the highest level for more than 100 million years.
• We know from ice cores that the global climate is perfectly capable of making dramatic shifts in a decade or less.
• Climate change is teaching us some crucial lessons: we cannot predict the future of climate, we can only guess at it; we should disabuse ourselves of any notion that we can manage climate.
• We need to learn to manage ourselves and our relationship with our environment if we are to bring an end to the destruction that is threatening our existence.