Climate Change - Fact or Fiction?
By Ian W Rudge
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Many readers will be perplexed by the media arguments over whether measures to combat global warming - or as scientists now prefer to call it, climate change - are necessary to forestall a serious threat to the environment, or form part of a politically-motivated scam. What I want to do here is to take a look at the underlying facts.
Firstly, let's establish an important point. Al Gore made the famous statement that, 'There can be NO debate' over global warming. He was correct, but not in the sense he envisaged. Debate is the process by which politics proceeds. Science, however, is not politics. Science is not a process of debate. It is a process of making postulates which which fit the observed facts. If a postulate fits the facts, then the postulate is potentially valid. If it does not fit the facts, then it is not valid.
Thus we need to exclude all of the emotional propaganda from our minds, and satisfy ourselves as to whether or not the claims of climate scientists fit the observed facts.
The human-induced warming theory
First, the theory aspect: The basis of the global warming postulate is that carbon dioxide (CO2)is regarded a greenhouse gas, because it intercepts some of the infrared (thermal) radiation leaving the earth's surface. This, it is said, increases the surface temperature by trapping the sun's heat. It is then claimed that releases of carbon dioxide from human industry are raising carbon dioxide concentrations to the point where there is a risk of runaway temperature increases, with resultant catastrophic effects on the Earth's ecosystem.
Things we do know:
Let's look at these points in more detail. That the Earth is about 32 Celsius warmer than it would be without an atmosphere, is largely undisputed. The airless Moon offers proof of this. Greenhouse gases play a part in this, but exactly how large a part is uncertain.
The range of infrared wavelengths intercepted by carbon dioxide is relatively narrow. Thus, its effectiveness as a greenhouse gas is somewhat limited compared to that of, say, water vapour, which intercepts a very wide range of infrared wavelengths. Thus we can reasonably assume that carbon dioxide has the potential to make only a small change to temperature, much less than that which might be caused by other greenhouse gases such as water vapour or methane.
The logarithmic nature of the effect means that a 'law of diminishing returns' applies. That is, small amounts of carbon dioxide can have a noticeable effect on heat retention, but larger amounts will have proportionately less effect. An experiment performed by Koch as long ago as 1905 suggested that less than a tenth of present atmospheric carbon dioxide concentration is enough to push the relationship into saturation, that is into the region where further carbon dioxide increases have only a minimal effect on heat retention. Thus, even very large increases in carbon dioxide concentration above present levels cannot cause more than a small temperature rise.
All of the above is well-accepted science.
The logarithmic relationship effectively precluding any runaway temperature rise due solely to carbon dioxide, human-induced global warming advocates have had to come-up with a range of positive feedback mechanisms, or 'forcings' which could potentially amplify the small effect of further carbon dioxide increases into a catastrophic temperature rise. Suggested forcings are changes in cloud cover, the release of methane from polar seas due to relatively small amounts of warming, or the melting of ice caps changing the albedo (reflectiveness) of the planetary surface.
Unlike the well-established theory that having an atmosphere warms the planet, none of these positive feedback mechanisms have any solid basis in either classical theory, or in real-world observations. They are mainly the product of computer modelling of the climate.
The observations
A key feature of good science is that any theory should be backed-up by observations which fit the theory well. In particular, it is more important to examine contradictory findings in detail than to rely on findings that seem to prove it true. If contradictory evidence cannot be satisfactorily explained, then the theory is suspect.
Historical data sources
Reliable thermometer data is available from around 1880 onwards. Between 1800 and 1880 some temperature records were made, but their accuracy is poor. For periods before 1800 we have no direct temperature records. Therefore, all suppositions about early temperatures are based upon 'proxies' - that is, the examination of secondary effects of temperature on other processes. The main two proxies used by climate scientists are ice cores, and tree rings.
Ice core data covers a very wide timescale. It cannot tell us much about recent temperature changes, only about ancient ones. Indications from this data are that throughout the Earth's history, temperatures have varied in a cyclic manner. Furthermore, carbon dioxide levels have also varied in a similar pattern to temperatures. At first sight this would seem to offer direct proof that carbon dioxide influences temperature. This finding formed the cornerstone of early global warming publicity material, especially that of Al Gore's film, An Inconvenient Truth, in which an oversize graph of ice core data was displayed as campaign material.
However, closer inspection of ice core data reveals that ancient temperature changes preceded changes in carbon dioxide level by several hundred years. Thus, carbon dioxide cannot have driven these ancient temperature changes. If anything it is possible (though unproven) that the temperature changes may have caused the subsequent changes in carbon dioxide concentration.
Tree ring data was used to create the famous Mann 'Hockey Stick' graph, covering the last thousand or so years of climate. This graph was claimed to show that temperature rises in the latter half of the 20th Century were unprecedented in recent history. It has since been discovered that data used by Mann gives incorrect temperature values for recent periods with accurate thermometer records. Thus, the reliability of this particular tree ring data as an indicator if pre-industrial temperatures has been called into doubt. It is also strongly suspected that Mann was aware of this situation when constructing the hockey stick graph, and chose to ignore it.
Other information sources also cast doubt upon the notion that modern temperature changes are in some way unique. It is known that one of the main reasons for the change of European aristocratic building styles from castles to manor houses at the end of the mediaeval era was that of climate change, castles being unsuitable accommodation for the increasingly cold winters of that period. Painters of the 1500-1800 era produced many winter scenes showing extensive icing-over of rivers and lakes, far more than we see today. Whilst these indicators may not be definitive science, they point toward the mediaeval and renaissance eras as being subject to significant climate changes, changes which are notable by their absence from the Mann hockey stick.
Modern findings
Coming to recent times, increases in industrial carbon dioxide output do follow a close match to temperature changes between 1970 and 2000. This correlation forms the mainstay of carbon dioxide-induced global warming theory. As outlined, though, to be good science a theory's predictions must conform to all of the available data, not just to a selected range. When viewed over a longer timescale, the accurate fit disintegrates. Considering the era from 1880 to present, we see:
So, over a period of more than a century, only the data from one thirty-year slot actually fits the human-induced global warming theory. The rest does not. In this situation it is up to the proponents of the theory to explain the discrepancy. With the bulk of the data not fitting the theory, this is indeed an onerous task. Various possible explanations have been put forward, but none can be verified.
Summary
The atmospheric heat-retention effect is real and carbon dioxide is a greenhouse gas. Furthermore, human activities over the industrial era have added a considerable amount of carbon dioxide to the atmosphere. Temperatures have also risen - albeit interspersed with periods of decline - over that time. Classical theory suggests that carbon dioxide can only induce a limited amount of warming, therefore any predictions of large, dangerous future temperature increases rely on 'amplification effects' existing within the climate system.
Presently, carbon dioxide emissions are still on the increase, especially from major coal users such as China. Yet, according to the accepted climate arbiters such as Berkeley Earth Sciences and the Goddard Institute of Space Science, global temperatures are falling slightly.
As to whether human-produced carbon dioxide was responsible for the temperature rises of the twentieth century, that is a matter which I shall leave the reader to decide, given the above facts.
Firstly, let's establish an important point. Al Gore made the famous statement that, 'There can be NO debate' over global warming. He was correct, but not in the sense he envisaged. Debate is the process by which politics proceeds. Science, however, is not politics. Science is not a process of debate. It is a process of making postulates which which fit the observed facts. If a postulate fits the facts, then the postulate is potentially valid. If it does not fit the facts, then it is not valid.
Thus we need to exclude all of the emotional propaganda from our minds, and satisfy ourselves as to whether or not the claims of climate scientists fit the observed facts.
The human-induced warming theory
First, the theory aspect: The basis of the global warming postulate is that carbon dioxide (CO2)is regarded a greenhouse gas, because it intercepts some of the infrared (thermal) radiation leaving the earth's surface. This, it is said, increases the surface temperature by trapping the sun's heat. It is then claimed that releases of carbon dioxide from human industry are raising carbon dioxide concentrations to the point where there is a risk of runaway temperature increases, with resultant catastrophic effects on the Earth's ecosystem.
Things we do know:
- The greenhouse effect is real
- Carbon dioxide is a greenhouse gas
- Carbon dioxide intercepts only two small ranges of infrared wavelengths
- Thus, it is not a particularly effective greenhouse gas
- The relationship between carbon dioxide concentration and heat retention is logarithmic
Let's look at these points in more detail. That the Earth is about 32 Celsius warmer than it would be without an atmosphere, is largely undisputed. The airless Moon offers proof of this. Greenhouse gases play a part in this, but exactly how large a part is uncertain.
The range of infrared wavelengths intercepted by carbon dioxide is relatively narrow. Thus, its effectiveness as a greenhouse gas is somewhat limited compared to that of, say, water vapour, which intercepts a very wide range of infrared wavelengths. Thus we can reasonably assume that carbon dioxide has the potential to make only a small change to temperature, much less than that which might be caused by other greenhouse gases such as water vapour or methane.
The logarithmic nature of the effect means that a 'law of diminishing returns' applies. That is, small amounts of carbon dioxide can have a noticeable effect on heat retention, but larger amounts will have proportionately less effect. An experiment performed by Koch as long ago as 1905 suggested that less than a tenth of present atmospheric carbon dioxide concentration is enough to push the relationship into saturation, that is into the region where further carbon dioxide increases have only a minimal effect on heat retention. Thus, even very large increases in carbon dioxide concentration above present levels cannot cause more than a small temperature rise.
All of the above is well-accepted science.
The logarithmic relationship effectively precluding any runaway temperature rise due solely to carbon dioxide, human-induced global warming advocates have had to come-up with a range of positive feedback mechanisms, or 'forcings' which could potentially amplify the small effect of further carbon dioxide increases into a catastrophic temperature rise. Suggested forcings are changes in cloud cover, the release of methane from polar seas due to relatively small amounts of warming, or the melting of ice caps changing the albedo (reflectiveness) of the planetary surface.
Unlike the well-established theory that having an atmosphere warms the planet, none of these positive feedback mechanisms have any solid basis in either classical theory, or in real-world observations. They are mainly the product of computer modelling of the climate.
The observations
A key feature of good science is that any theory should be backed-up by observations which fit the theory well. In particular, it is more important to examine contradictory findings in detail than to rely on findings that seem to prove it true. If contradictory evidence cannot be satisfactorily explained, then the theory is suspect.
Historical data sources
Reliable thermometer data is available from around 1880 onwards. Between 1800 and 1880 some temperature records were made, but their accuracy is poor. For periods before 1800 we have no direct temperature records. Therefore, all suppositions about early temperatures are based upon 'proxies' - that is, the examination of secondary effects of temperature on other processes. The main two proxies used by climate scientists are ice cores, and tree rings.
Ice core data covers a very wide timescale. It cannot tell us much about recent temperature changes, only about ancient ones. Indications from this data are that throughout the Earth's history, temperatures have varied in a cyclic manner. Furthermore, carbon dioxide levels have also varied in a similar pattern to temperatures. At first sight this would seem to offer direct proof that carbon dioxide influences temperature. This finding formed the cornerstone of early global warming publicity material, especially that of Al Gore's film, An Inconvenient Truth, in which an oversize graph of ice core data was displayed as campaign material.
However, closer inspection of ice core data reveals that ancient temperature changes preceded changes in carbon dioxide level by several hundred years. Thus, carbon dioxide cannot have driven these ancient temperature changes. If anything it is possible (though unproven) that the temperature changes may have caused the subsequent changes in carbon dioxide concentration.
Tree ring data was used to create the famous Mann 'Hockey Stick' graph, covering the last thousand or so years of climate. This graph was claimed to show that temperature rises in the latter half of the 20th Century were unprecedented in recent history. It has since been discovered that data used by Mann gives incorrect temperature values for recent periods with accurate thermometer records. Thus, the reliability of this particular tree ring data as an indicator if pre-industrial temperatures has been called into doubt. It is also strongly suspected that Mann was aware of this situation when constructing the hockey stick graph, and chose to ignore it.
Other information sources also cast doubt upon the notion that modern temperature changes are in some way unique. It is known that one of the main reasons for the change of European aristocratic building styles from castles to manor houses at the end of the mediaeval era was that of climate change, castles being unsuitable accommodation for the increasingly cold winters of that period. Painters of the 1500-1800 era produced many winter scenes showing extensive icing-over of rivers and lakes, far more than we see today. Whilst these indicators may not be definitive science, they point toward the mediaeval and renaissance eras as being subject to significant climate changes, changes which are notable by their absence from the Mann hockey stick.
Modern findings
Coming to recent times, increases in industrial carbon dioxide output do follow a close match to temperature changes between 1970 and 2000. This correlation forms the mainstay of carbon dioxide-induced global warming theory. As outlined, though, to be good science a theory's predictions must conform to all of the available data, not just to a selected range. When viewed over a longer timescale, the accurate fit disintegrates. Considering the era from 1880 to present, we see:
- 1880-1940: A prolonged rise in temperature in spite of modest global carbon dioxide outputs
- 1940-1970: A decline in temperature, in spite of rising carbon dioxide levels
- 1970-2000: A rise in temperature which follows carbon dioxide levels
- 2009-2005: A levelling-out of the temperature rise
- 2005-2011: A slight decline in temperature, in spite of still-rising carbon dioxide levels
So, over a period of more than a century, only the data from one thirty-year slot actually fits the human-induced global warming theory. The rest does not. In this situation it is up to the proponents of the theory to explain the discrepancy. With the bulk of the data not fitting the theory, this is indeed an onerous task. Various possible explanations have been put forward, but none can be verified.
Summary
The atmospheric heat-retention effect is real and carbon dioxide is a greenhouse gas. Furthermore, human activities over the industrial era have added a considerable amount of carbon dioxide to the atmosphere. Temperatures have also risen - albeit interspersed with periods of decline - over that time. Classical theory suggests that carbon dioxide can only induce a limited amount of warming, therefore any predictions of large, dangerous future temperature increases rely on 'amplification effects' existing within the climate system.
Presently, carbon dioxide emissions are still on the increase, especially from major coal users such as China. Yet, according to the accepted climate arbiters such as Berkeley Earth Sciences and the Goddard Institute of Space Science, global temperatures are falling slightly.
As to whether human-produced carbon dioxide was responsible for the temperature rises of the twentieth century, that is a matter which I shall leave the reader to decide, given the above facts.
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