Arrhenius suggested that this increase could be beneficial, making Earth's climate “more equable,” while stimulating plant growth and food production. Most scientists thought the idea that humans could actually affect average global temperatures far-fetched.
In 1938, G. S. Callendar, a British amateur meteorologist, made a bold claim that may sound familiar. He argued that man was responsible for heating up the planet with CO2 emissions. Despite the previous work of Arrhenius, it still wasn’t a common notion at the time. He published an article in the Quarterly Journal of the Royal Meteorological Society on the subject stating, “In the following paper I hope to show that such influence is not only possible, but is actually occurring at the present time.” He went on the lecture circuit describing carbon-dioxide-induced global warming, similar to Al Gore's present day crusade.
The 1940s saw significant developments in infrared spectroscopy, particularly for measuring long-wave IR radiation. It was empirically demonstrated that increasing the amount of atmospheric carbon dioxide resulted in greater absorption of infrared radiation. Also, it was discovered that water vapor, ozone and carbon dioxide absorbed radiation at different wavelengths. This allowed scientists to measure the increase in atmospheric CO2 by studying spectroscopic data.
In 1956, Gilbert Plass, a Canadian physicist working in the United States, concluded that adding more carbon dioxide to the atmosphere would capture infrared radiation that is otherwise lost to space.25 ,26 He further concluded that human activities were raising the average global temperature. Plass also pioneered the use of electronic computers in climate studies, a foreshadowing of modern climate science's dependency on computer models.
The American government first became involved in 1965, when Roger Revelle, a member of the President's Science Advisory Committee Panel on Environmental Pollution, helped publish the first high-level government document to mention global warming.27 The report identified many of the environmental troubles the nation faced, including the potential for global warming by carbon dioxide. Revelle would continue to popularize the notion of human-caused global warming, publishing a widely-read article in Scientific American in 1982. The article linked the rise in global sea level and the “relative role played by the melting of glaciers and ice sheets versus the thermal expansion of the warming surface waters.”28
Revelle, an oceanographer by training, convinced himself that he was the “grandfather” of global warming theory, conveniently ignoring the work of Arrhenius, Chandler, and Plass. On his death in 1982, his hometown paper, the San Diego County edition of the Los Angeles Times, began its front page coverage as follows: “Roger Revelle, the internationally renowned oceanographer who warned of global warming 30 years before greenhouse effect became a household term, died Monday of complications related to a heart attack.” Even if his role in discovering global warming wasn't as central as he and the press thought, Revelle did play a major part in popularizing the subject.
Increased political awareness of global warming issues led to the establishment of the Intergovernmental Panel on Climate Change (IPCC) in 1988. The IPCC was established by two UN organizations, the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP), to evaluate the risk of climate change brought on by humans. The IPCC was the first international effort of this scale to address environmental issues and has become the primary source of global warming information quoted by government officials and the media.
The remaining portion of this chapter will examine the case for human-caused global warming as advanced by the IPCC. We will show how a scientific observation by one man evolved into a political controversy, involving thousands of scientists, politicians and bureaucrats. First, we will examine changes in Earth's temperature over the past century or so.
Is Earth Really Warming?
There is little doubt that, over the past 100 years or so, Earth's climate has been warming. There may still be a few scientists out there who would disagree, but the fact that the planet is warming comes as close to universal acceptance (i.e. consensus29 ) as anything in science. But, as we shall see, consensus is not a valid scientific argument. Despite claims of consensus, opinions vary widely when the rate of warming and its causes are discussed.
The changing global temperature shown in Illustration 2 reveals a warming trend of around 1.8°F (1°C) per century. What is also apparent is the fact that the temperature didn't rise in a smooth, straight line. There were a number of ups and downs, particularly when traced from year to year. The five year mean temperature provides a smoother curve, but even it has had a bumpy rise. While Earth's climate is constantly changing, the change is anything but constant.
After a slight dip at the beginning of the last century, temperatures rose for 30 years, until around the start of World War II. Then the temperature sank for four decades, resuming an upward trend only after the mid-1970s. Because of this capricious temperature fluctuation, the time frame used to calculate the temperature trend is tremendously important.
Illustration 2 Change in global mean temperature since 1880. Source NASA.
When measured from 1975 to the 2005, a temperature rise of 0.8°C is observed in 30 years, a rate of +2.7°C per century. But, if the past 20 years were measured in 1964, a 20 year decrease of 0.4°C would be recorded, a cooling trend of -1.3°C per century. The temperature difference between 1900 and 2000 shows a rise for that century of 0.4°C, significantly lower than the accepted 1°C per century. Clearly, how the measuring points are chosen can distort the perceived temperature trend greatly.
Judging a trend on yearly fluctuations is also an unsound practice. There was a 0.2°C drop from 1998 to 1999, in the midst of a 30 year warming period, while from 1956 to 1957 there was a 0.2°C rise during a 30 year period of temperature decline. Claiming that a year is the “hottest year in a decade” is totally meaningless in terms of the overall trend, and claiming that it is proof of global warming is an outright lie.
The truth is that Earth's climate is always changing. It varies from year to year, from decade to decade, and from century to century. What is seldom mentioned in the global warming debate is that there are also longer trends, spanning thousands and even millions of years. The forces affecting Earth's climate are colossal, long-acting, and only poorly understood by science.
How should we judge climate change? Assuming that the previous century's trend will continue for the next 100 years is naive, but probably a good place to start. If you extend the warming trend of the past century out into the future, a linear prediction, Earth's climate should grow warmer by another 1.8°F by the year 2100, but there is no guarantee this will happen. This continued, modest increase falls below the lowest increase predicted by the IPCC, which uses much more complicated means of estimating future temperature change.
The IPCC Reports
Since its creation, the IPCC has issued four major, and numerous special, reports on the threat of human-caused global warming. Each installment has reported more dreadful consequences with greater certainty than the last. The latest report, the fourth in the series, states that the world's scientists are “90% sure” that humans are to blame for the unprecedented rise in Earth's temperature.30
Table 1: Time-line for IPCC reports.
The previous report, the Third Assessment Report (TAR), had been released in 2001. Its findings were dire enough. In the words of Dr. R. K. Pachauri, Chairman of the IPCC at the High Level Segment, in an address given at the 11th Conference of the Parties to the United Nations Framework Convention on Climate Change and 1st Conference of the Parties serving as Meeting of the Parties to the Kyoto Protocol, in Montreal, Canada, 7 December 2005:
“The Earth’s climate system has demonstrably changed on both global and regional scales since the pre-industrial era, and there is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities...
Projections using the SRES31 emissions scenarios based o
n a range of climate models point to an increase in globally averaged surface temperature of 1.4 to 5.8°C over the period 1990 to 2100. This is about two to ten times larger than the central value of observed warming over the 20th century, and the projected rate of warming is very likely to be without precedent during at least the last 10,000 years, based on paleo-climate data.”32
So, here is a prediction of unprecedented climate change over the next century, a change not seen in “at least the last 10,000 years.” Temperatures could rise by as much as 2.5°F to 10°F (1.4°C to 5.8°C) around the world. This change could be bad for the climate, living things, and human civilization.
But the TAR isn't all doom and gloom. It mentions several courses of action that could reduce the level of threat. There is also some carefully worded bureaucratic bet-hedging about the effect of these “change mitigation efforts” on the ultimate outcome. What the report says is, if we cut down on CO2 emissions, the temperature won't go up as much. So, the sooner we stop the emissions the better.
Dr. Pachauri noted the AR4 would contain additional and new information to update the older report. He said, “It will address some specific cross-cutting themes, which cover, in addition to other issues, scientific and technical aspects of Article 2 of the Convention.”
The Fourth Assessment Report
The accompanying text box contains the press release from the IPCC announcing the release of the Fourth Assessment Report (AR4). The AR4 consists of four distinct sections: The Physical Science Basis; Impacts, Adaptation and Vulnerability; Mitigation of Climate Change and The Synthesis Report (SYR). Each of the first three sections has its own set of experts, called a Working Group. The three Working Group report sections were released by early May, 2007.
The most concise statement of the IPCC's findings is found in the Summary for Policy Makers (SPM). Unfortunately, the language found in all the IPCC reports is anything but clear and understandable. A strange brew of scientific jargon and bureaucratic doublespeak, the SPM is intended for use by non-scientists and is the most accessible of the lot.
What does the IPCC say about Earth's temperature? It's going up, of course; that conclusion was not really in doubt. What is questionable are the IPCC's presentation of historic data, methodology and estimated severity of temperature increase.
Illustration 3, taken directly from the IPCC report, contains two graphs. The upper graph shows average temperatures for the past 140 years. The lower graph extends the temperature readings to cover the past 1000 years. The reason for splitting the data up this way is that only temperatures for the past 140 years are based on direct measurements (e.g. thermometer readings). All the older temperatures shown are inferred from other measurements, called proxies. An interesting feature of the lower graph in Illustration 3 is the dramatic upswing, shown at the far right of the graph.
This graph is known as the “hockey stick,” because of its shape. The long, almost straight portion is the shaft and the up-swing at the end is the blade. For reasons we will discuss later, this graph has become infamous among those who question the IPCC's methods and conclusions.
The sharp up-tick right around the year 2000 is not part of the heavily drawn line that meanders across the rest of the graph. This is because the heavy line represents a moving average, a way to mathematically smooth out choppy data like Earth's yearly temperature. There are not enough data points in the steepest portion of the graph to smooth out the peaks. The lack of smoothing helps make the final up-tick all the more dramatic.
Illustration 3 Temperature change for the past 140 and 1,000 years. Source IPCC Fourth Assessment Report.
Note the wide, dark gray swath that encloses the temperature curve up until 1900. This band represents the uncertainty in the proxy temperatures used to create the graph. This means that even though the averaged temperature curve is shown consistently below the straight line, representing the average temperature for 1960-1990, some proxy data indicated that the temperatures were above that line. The IPCC takes uncertainty very seriously—to the point where they have published a number of guidelines on exactly what the terms used in their reports mean. These include: Uncertainties in Guidance Papers on the Cross Cutting Issues of the Third Assessment Report of the IPCC,33 published in 2000; IPCC Workshop on Describing Scientific Uncertainties in Climate Change to Support Analysis of Risk and of Options: Workshop report,34 published in 2003; and the IPCC Uncertainty Guidance Note,35 published in 2005. In the introductory letter to the guidance note, use of the terms “confidence” and “likelihood” as alternative ways of expressing uncertainty are given “particular attention.”36
Multiple scales are provided to allow IPCC authors to confidently identify their level of uncertainty. Table 2 defines the meanings of phrases used when expressing levels of confidence, while Table 3 defines phrases used when talking about likelihood. It is not uncommon for scientists to use statistics and probabilities when they are unsure of their conclusions. This might seem confusing, but at least it is well defined confusion.
Table 2: Quantitatively calibrated levels of confidence
When the terms “high confidence” or “about as likely as not” appear in an IPCC report they have specific meanings. “High confidence” means that there is an eight in ten, or 80%, chance of being correct. “About as likely as not” means there is between a one in three and two in three (33%-66%) chance of being correct. All the conclusions presented in the IPCC reports, especially those in the Summary for Policymakers, must be viewed through this haze of statistical uncertainty. As Mark Twain said, “There are three kinds of lies: lies, damn lies, and statistics.”
Table 3: IPCC Likelihood Scale.
An example of how these definitions are used to interpret figures and statements in the IPCC reports is shown in Illustration 4. Warmer days and nights are rated a 99% sure bet. More warm spells and heavy rain come in at 90% while drought, more hurricanes, and rising sea levels are a two in three chance at 66%.
Illustration 4: Likelihood of Climate Effects.
But even these tentative predictions are conditional, based on the total amount of actual temperature rise. According to the IPCC, “The categories defined in this table should be considered as having 'fuzzy' boundaries.”37 Fuzzy indeed. With these definitions in mind, we will examine the effects of global warming as predicted by the IPCC's latest report.
Predicted Effects of Global Warming
IPCC Working Group II (WGII) is responsible for accessing the impact of global warming. Their section of the AR4 document contains “current scientific understanding of impacts of climate change on natural, managed and human systems, the capacity of these systems to adapt and their vulnerability.”38 This report claims that global warming will cause significant change in many physical and biological systems. As an example of the actual text in the report, we quote from the summary report.
With regard to changes in snow, ice and frozen ground (including permafrost), there is high confidence that natural systems are affected. Examples are:
enlargement and increased numbers of glacial lakes [1.3]39 ;
increasing ground instability in permafrost regions, and rock avalanches in mountain regions [1.3];
changes in some Arctic and Antarctic ecosystems, including those in sea-ice biomes, and also predators high in the food chain [1.3, 4.4, 15.4].
Based on growing evidence, there is high confidence that the following effects on hydrological systems are occurring:
increased run-off and earlier spring peak discharge in many glacier- and snow-fed rivers [1.3];
warming of lakes and rivers in many regions, with effects on thermal structure and water quality [1.3]...
There is very high confidence, based on more evidence from a wider range of species, that recent warming is strongly affecting terrestrial biological systems, including such changes as:
earlier timing of spring events, such as leaf-unfolding, bird migration and egg-laying [1.3];
poleward and upwa
rd shifts in ranges in plant and animal species [1.3, 8.2, 14.2].
To save space, here is a summary of the other major outcomes and predictions from subsequent sections:
There could be more fish farther north, more algae growing in lakes, and fish runs will start earlier in the year.
Spring will come earlier. Warmer higher latitudes will mean animals and plants will be found in places that were previously too cold for them.
Crops might be affected, also, there might be more forest fires and pests. People may experience a worse hay fever season.
The hot summer weather might be dangerous to some. Also, snow sports and winter hunting might be diminished.
Warmer days and nights are rated a 99% certainty.
More warm spells and heavy rain are rated 90%.
Drought, more frequent and severe hurricanes, and rising sea levels receive 66%.
The report also cautions that warming might cause floods from glacier melt-water. Some places will experience drier conditions, which could affect agriculture. Water released from melting glaciers could make sea-levels higher and flood low-lying areas. It is noted, however, that these effects have not “become established trends.”
The Resilient Earth: Science, Global Warming and the Fate of Humanity Page 3