Class 4 - The Causes of Global Warming

Scientific and Spiritual Dimensions of Climate Change

A Study Course

Class 4

The Causes of Global Warming

“God saw everything that he had made, and indeed, it was very good.” ⁱ The Bible

“No defect canst thou see in the creation of the God of Mercy: Repeat the gaze: seest thou a single flaw?” ⁱⁱ The Qur'an

“How great, O my God, is this Thy most excellent handiwork, and how consummate Thy creation, which hath caused every understanding heart and mind to marvel!” ⁱⁱⁱ Baha'u'llah

Section 1: What Is Global Warming?

“Scientists tell us that a gradual warming of the planet is underway and will continue at an accelerating rate. Globally, 11 out of the 12 warmest years on record have occurred in the past 12 years (during 1995 to 2006).” ^iv 1998 and 2005 were the hottest years ever recorded.

“The average rate of global warming over the full 20th century was slightly less than 0.1°C (0.18°F) per decade, but in the past few decades the warming rate has nearly doubled to about 0.2°C per decade. Overall, the average temperature of the globe has warmed from about 13.5°C to 14.5°C (56.3° to 58.1°F) since the beginning of the 20th century.

While this warming of roughly 1°C (1.8°F) might seem small, it is nearly one-fourth of the estimated change in the (average) temperature of the globe between today and the depths of the last ice age, when (the area of) New York City was covered by a sheet of ice almost half a kilometer thick.” ^v

Some areas have warmed much more. Parts of the Arctic have warmed by 2.2°-2.7°C (4-5°F) just since the 1950s. ^vi

As we have see in the last two chapters, this warming has serious consequences, especially for low-lying areas and poor countries, but in the near future also for all of humanity.

For the understanding of global warming it helps to have some insight into the carbon cycle: “The biosphere is maintained by a complex set of delicately balanced systems which are still poorly understood. The atmospheric conditions that permit life to exist were themselves created in part by the action of living things. The early plants removed carbon dioxide from the atmosphere and added oxygen, making animal life possible. Dead plants, both the remains of marine plankton and terrestrial vegetation, were buried and fossilized as coal, oil and gas, and their carbonate skeletons became layers of limestone, locking a significant part of the Earth's carbon away in geological formations. Carbon cycles through the biosphere, as plants take up carbon dioxide to make organic matter, while animals and decomposers return the carbon dioxide to the oceans and atmosphere.” ^vii

The Greenhouse Effect:

Atmospheric gases like carbon dioxide (CO₂), methane and nitrous oxide are called greenhouse gases because they act similar to the glass in a greenhouse by trapping heat. Or more specifically worded: “the greenhouse gases are transparent to incoming ultraviolet (short wavelength) radiation from the sun, which passes through the atmosphere and hits the Earth. The Earth is warmed by this radiation, and in response radiates infrared (long wavelength) energy back into space. That is where greenhouse gases come into play. These atmospheric gases absorb some of the outgoing infrared radiation, trapping the heat energy in the atmosphere and thereby warming the Earth.” ^viii Life on Earth is only possible because of this greenhouse effect. It has kept the Earth’s average surface temperature stabilized at around 13.5°C (56.3°F).

Since the industrial revolution, greenhouse gases have sharply increased upsetting the previously long-lasting balance. Scientists confirm that this increase of greenhouse gases is for the most part anthropogenic (man-made). The increase comes mainly from emissions from power plants, cars, airplanes, from deforestation and industrial activities. We are “returning carbon to the atmosphere and oceans that has long been out of circulation.” ^ix

The more greenhouse gases there are in the atmosphere the warmer our planet becomes.

A little bit of climate science history

The Greenhouse Effect has been an accepted scientific fact since the 19th century. Already in the 19th and early 20th century, some scientists suggested a possible future global warming caused by human emissions of CO₂, but this theory was only confirmed later. Instrumental to this discovery was Prof. Charles Keeling. In 1958, he began daily measurements of CO₂ concentrations in the atmosphere. The resulting curve showed a steady increase of CO₂ concentrations (see graph 1). Each year, there is a temporary decline in the curve: Whenever it is spring and summer in the Northern Hemisphere (which has much more land mass than the Southern Hemisphere), CO₂ concentrations in the atmosphere are falling, because its vegetation is taking in more CO₂.

Graph 1: ^x
atmospheric CO2 concentration

Many more studies have been done since then. Besides carbon dioxide (CO₂), the main greenhouse gases are methane (CH₄) and nitrous oxide (N₂O). (Water vapor, a naturally occurring greenhouse gas, will be discussed in class 8, section 2.)

Scientists collected data on the atmospheric concentrations of these three greenhouse gases during the past 1000 years. As you can see on the curves below, for a long time their levels were pretty constant with only minor variations, but then they started to increase dramatically in the 19th century.

Graph 2:
carbon dioxide, methane, nitrous oxide concentrations

carbon dioxide, methane, nitrous oxide concentrations

Carbon Dioxide (CO₂) is emitted primarily by burning fossil fuels and by the clearing of forests. CO₂ remains in our atmosphere for many decades and some of it for many centuries.

Methane (CH₄) is emitted from landfills, coalmines, oil and gas operations, beef production and rice paddies. Methane is a very powerful greenhouse gas. It stays in the atmosphere for about 12 years.

Nitrous oxide (N₂O) is emitted by nitrogen based fertilizers and industrial activities. It stays in the atmosphere on average for 114 years.

We should also be aware of another category of greenhouse gases, the Fluorocarbons or F-gases. Chemical engineers have designed these gases specifically to trap heat. That’s why they are very powerful greenhouse gases. These chemicals are used mainly “in refrigeration and air conditioning, but also as solvents, as blowing agents in foams, as aerosols or propellants, and in fire extinguishers. The Intergovernmental Panel on Climate Change calculated that the cumulative buildup of these gases in the atmosphere was responsible for at least 17% of global warming due to human activities in 2005. The most commonly used F-gases are the hydrofluorocarbons (HFCs). HFCs were developed by the chemical industry in response to the discovery of damage to the Earth’s ozone layer due to chlorofluorocarbons (CFC) use. But this development ignored the known global warming effect of the newer chemicals. Fortunately, there are environmentally safe, efficient, technologically proven, and commercially available alternatives to F-gases in almost all domestic and commercial applications.”^xi The chemical industry has so far resisted the use of these natural alternatives. As many F-gases stay in the atmosphere for a very long time it is extremely important that we discontinue their use and production.

Section 2: A Look into the Past

“Science is the discoverer of the past. From its premises of past and present we deduce conclusions as to the future”. ^xii ‘Abdu'l-Baha

Looking back into the more distant past we know that there have been natural cycles of warming and cooling. The Earth went through many ice ages and interglacial periods. British scientists drilled three kilometers deep into the Antarctic ice and measured gas concentrations in pockets of air that have been trapped in the ice for thousands of years. From the analysis of the ice cores they could figure out the temperatures and CO₂ concentrations of the past 420,000 years:

Graph 3: ^xiii
past temperature and CO2

Let us first look only at the temperature changes which is the lower curve. The areas with low temperatures signify ice ages; the peaks going up signify the briefer interglacial periods. The last dip down on the right shows the last ice age more than 10’000 years ago. These climate changes were caused by natural factors. The main factors were slight variations in the earth’s rotation, namely the cyclical changes in the tilt of the Earth’s axis of spin and the shape of the Earth’s orbit around the sun. Solar variation and volcanic eruptions played a minor role as well.

Now, let us look at the CO₂ concentrations, which is the higher curve. You can see easily how similar the two curves are. When temperature is up, CO₂ is up and vice versa. Although the graph may look simple, the relationship between CO₂ level and temperature is very complex. As we said before, in the past, the reasons for climatic changes were all natural processes, especially shifts in the Earth's rotation. Temperatures affected CO₂ levels due to feedback mechanisms (more about that in class 8, section 2). In turn CO₂ had an effect on temperature by augmenting the warming or cooling trend. In other words: Without the atmospheric CO₂ the changes in temperatures would have been much smaller.

On graph 4 below we see the atmospheric CO₂ concentrations over the past 420’000 years, the same as in the previous picture. In addition, we can see the levels in 2001 and projections for the end of this century.

Graph 4:
past and projected CO2

“The atmospheric concentrations of CO₂ consistently fluctuated between 200 parts per million (ppm) during the ice ages and 280 ppm during the warm intervals. This shift from ice age to warm period occurred many times and always within this CO₂ range. When the Industrial Revolution began, the atmospheric CO₂ level was roughly 280 ppm.”^xiv

On the graph we can see that they never went above 300ppm. In 2009, atmospheric CO₂ concentrations are at an extraordinary 387 ppm!

From this and other studies we know that 387ppm “is not only far above any level over the last 740,000 years, it may be nearing a level not seen for 55 million years. At that time the Earth was a tropical planet. There was no polar ice; sea level was 260 feet higher than it is today.” ^xv Let's put the number of 740,000 years into proper perspective. What we consider human civilization doesn't extend farther back than 10,000 years. At that time a relatively warm and stable climate emerged which allowed agriculture.

Section 3: The Present and the Future

The situation today is very different from the past’s natural cycles. In a very short period of time, human beings have used huge quantities of stored solar energy (fossil fuels) thereby releasing unprecedented amounts of greenhouse gases into the atmosphere. That’s why greenhouse gas concentrations have been so rapidly rising. "We find that CO₂ is about 30% higher than at any time, and methane 130% higher than at any time; and the rates of increase are absolutely exceptional: for CO₂, 200 times faster than at any time in the last 650,000 years." ^xvi

The global warming we have already experienced and the many changes in climate all over the world can only be explained by these tremendous increases in greenhouse gases. They cannot be explained by any natural cycle or changes in solar activity.

Today, human activities have a stronger impact on climate than natural occurrences: “We have so much CO₂ in the atmosphere that its huge radiative forcing overwhelms the changes associated with orbital forcing. No ice age could start at this point!” ^xvii

If greenhouse gases were held constant at today's level, it is estimated that it would take several decades for their full impact to be felt. The Earth would continue to warm until the climate is in balance with the current greenhouse gases. Unfortunately, CO₂ levels are not constant but are continuing to rise at an accelerating rate, which will change the climate and the living conditions on Earth in a very dangerous way.

Review questions on the causes of climate change:
What is the “Greenhouse Effect?” Why are global temperatures rising? What are some of the greenhouse gases and where do they come from? What are the reasons for the sudden increase of greenhouse gases since the 19^th century? Which human activities emit greenhouse gases?

REFERENCES

i    Genesis 1,31
ii    The Qur'an (Rodwell tr), Sura 67 - The Kingdom)
iii    Baha'u'llah (Prayers and Meditations by Baha'u'llah, p. 48)
iv    Intergovernmental Panel on Climate Change Report, April 6, 2007, WG 1, Frequently Asked Questions 3.1
v Dire Predictions – Understanding Global Warming, The illustrated guide to the findings of the IPCC, by Michael E. Mann and Lee R. Kump, p. 36
vi    http://www.pewclimate.org/arctic_qa.cfm
vii CLIMATE CHANGE: SCIENTIFIC AND FAITH PERSPECTIVES, Arthur Lyon Dahl, http://www.bcca.org/ief/doc/ddahl06b.htm
viii “Common Wealth – Economics for a Crowded Planet” by Jeffrey D. Sachs, p. 84
ix    CLIMATE CHANGE: SCIENTIFIC AND FAITH PERSPECTIVES, Arthur Lyon Dahl, http://www.bcca.org/ief/doc/ddahl06b.htm
x    Graph 1: http://www.aip.org/history/climate/xMaunaLoa.htm
xi    “The Risk of Other Greenhouse Gases” by Janos Mate, Kert Davies, and David Kanter, published in “State of the World 2009” by the Worldwatch Institute
xii   'Abdu'l-Baha (The Promulgation of Universal Peace, p. 28)
xiii UNEP, Grid: http://maps.grida.no/go/graphic/temperature-and-co2-concentration-in-the-atmosphere-over-the-past-400-000-years
xiv up-dated from Plan B 2.0 by Lester R. Brown p.59 2. EPICA Community Members, op. cit. note 1; current carbon dioxide level from C. D. Keeling and T. P. Whorf, “Atmospheric CO 2 Records from Sites in the SIO Air Sampling Network,” in Trends: A
Compendium of Data on Global Change (Oak Ridge, TN: Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, May 2005); Brown, op. cit. note 1; Quirin Schiermeier, “A Rising Tide,” Nature, vol. 428 (11 March 2004), pp. 114–15.
xv   ibid
xvi Thomas Stocker from the University of Bern, Switzerland, 24 November 2005 http://news.bbc.co.uk/2/hi/science/nature/4467420.stm
xvii Rebecca Robinson, Prof. of Oceanography, University of Rhode Island, in an e-mail, Sept. 18, 2008

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Last updated 9 November 2009
© Christine Muller and International Environment Forum