June 28, 2018
Dear Family and Friends,
This is Segment 4 of the Climate Change Series. This segment focuses on points of agreement and disagreement on Climate Science. The format is for the Advocate Point excerpt(s) being first followed by a Skeptic Counterpoint excerpt(s) on the points of disagreement.
In the text below I narrowed the excerpts to three items of debate: (1) The Debate on Human Caused Factors, (2) The Debate on the Natural Cause Factors, and (3) The Debate on the Reliability of the General Circulation Models (GCMs). If you desire to expand the debate, additional information can be found in the PDF attachment referenced below. The advocacy point are excerpts from “A Global Warming Primer” by Jeffrey Bennett and the skeptics excerpts are from “Global Warming Alarmists, Skeptics and Deniers” by Dedrick Robinson and Gene Robinson.
Continuing with the same questions for these authors that were used in the introductory portions of Segments 2 & 3:
1. Is there a 20th century temperature rising trend acknowledged? Yes, by both the Advocates and Skeptics. Specifically, “since 1880, the global temperature has increased 1 to 1.5 degrees Fahrenheit.”
2. Is that trend attributed to fossil fuel emissions?
-- Yes, in the Advocacy excerpts
-- No, in the Skeptic excerpts
What is the evidence cited to support point 2 above?
-- The Advocates Point:
Fact 1: Carbon dioxide is a greenhouse gas, that traps heat radiating from the sun’s energy hitting the Earth’s surface thus acting as an insulation source which warms the Earth’s surface.
Fact 2: The burning of fossil fuels results in CO2 being released adding more heat trapping gas to Earth’s atmosphere.
Conclusion: Because more heat trapping gas is added to the atmosphere acting as an insulation source, the temperature of the atmosphere should also increase. The warming should continue to increase as more CO2 is added.
Further: If more CO2 raises the global temperature a little bit, the atmosphere can hold more water vapor which then traps more heat, making the temperature rise even more.
-- The Skeptics Point:
Ice records show that increased temperature drives increasing CO2 versus increasing CO2 driving increasing temperatures. Likewise, if temperature decreases so does the CO2 level. Net temperature is the driver not CO2. Advocates do not contest this point but contend that “small changes in climate are then amplified by feedback from CO2 and water vapor” causing temperature to rise even more. The skeptics assert this is an unproven theory. But if true it would lead to run away temperatures, because there is nothing to stop the continual reinforcing feedback process; and this is clearly not the case
4. Is the trend attributed to natural causes?
-- No, in the Advocates excerpts
-- Yes, in the Skeptics excerpts
5. What is the evidence cited to support point 4 above?
-- The Skeptics Point:
Point 1: The Medieval Warm Period (900 to 1300 A.D.) was a global effect, and the temperatures were equivalent or slightly greater than exist today, with lower CO2 levels.
Point 2: “Recent studies with improved instrumentation suggest the sun’s total irradiance is enough to account for a major portion of the warming since the end of the Little Ice Age.”
-- The Advocates Point:
There is no evidence to support a natural cause theory. The Medieval Warm Period had regional temperature increases but on a global basis temperatures were far less than those of today. The sun’s variation in energy output is a very small amount (less than 1%) and the amount of sunlight has moved in the opposite direction since 1880 as determined by solar irradiance.
6. Are there severe consequences predicated? This subject is addressed in segment 5
7. Is there any additional scientific information presented concerting the debate? Yes, on General Circulation Models (GCMs) and CO2.
The next Segment (5) will contain advocate points and skeptic counterpoints by individual topics on the global consequences of global warming, in a similar format as this segment. The excerpts will come from the same two books as those utilized in this segment.
Happy Learning,
Harley
Dear Family and Friends,
This is Segment 4 of the Climate Change Series. This segment focuses on points of agreement and disagreement on Climate Science. The format is for the Advocate Point excerpt(s) being first followed by a Skeptic Counterpoint excerpt(s) on the points of disagreement.
In the text below I narrowed the excerpts to three items of debate: (1) The Debate on Human Caused Factors, (2) The Debate on the Natural Cause Factors, and (3) The Debate on the Reliability of the General Circulation Models (GCMs). If you desire to expand the debate, additional information can be found in the PDF attachment referenced below. The advocacy point are excerpts from “A Global Warming Primer” by Jeffrey Bennett and the skeptics excerpts are from “Global Warming Alarmists, Skeptics and Deniers” by Dedrick Robinson and Gene Robinson.
Continuing with the same questions for these authors that were used in the introductory portions of Segments 2 & 3:
1. Is there a 20th century temperature rising trend acknowledged? Yes, by both the Advocates and Skeptics. Specifically, “since 1880, the global temperature has increased 1 to 1.5 degrees Fahrenheit.”
2. Is that trend attributed to fossil fuel emissions?
-- Yes, in the Advocacy excerpts
-- No, in the Skeptic excerpts
What is the evidence cited to support point 2 above?
-- The Advocates Point:
Fact 1: Carbon dioxide is a greenhouse gas, that traps heat radiating from the sun’s energy hitting the Earth’s surface thus acting as an insulation source which warms the Earth’s surface.
Fact 2: The burning of fossil fuels results in CO2 being released adding more heat trapping gas to Earth’s atmosphere.
Conclusion: Because more heat trapping gas is added to the atmosphere acting as an insulation source, the temperature of the atmosphere should also increase. The warming should continue to increase as more CO2 is added.
Further: If more CO2 raises the global temperature a little bit, the atmosphere can hold more water vapor which then traps more heat, making the temperature rise even more.
-- The Skeptics Point:
Ice records show that increased temperature drives increasing CO2 versus increasing CO2 driving increasing temperatures. Likewise, if temperature decreases so does the CO2 level. Net temperature is the driver not CO2. Advocates do not contest this point but contend that “small changes in climate are then amplified by feedback from CO2 and water vapor” causing temperature to rise even more. The skeptics assert this is an unproven theory. But if true it would lead to run away temperatures, because there is nothing to stop the continual reinforcing feedback process; and this is clearly not the case
4. Is the trend attributed to natural causes?
-- No, in the Advocates excerpts
-- Yes, in the Skeptics excerpts
5. What is the evidence cited to support point 4 above?
-- The Skeptics Point:
Point 1: The Medieval Warm Period (900 to 1300 A.D.) was a global effect, and the temperatures were equivalent or slightly greater than exist today, with lower CO2 levels.
Point 2: “Recent studies with improved instrumentation suggest the sun’s total irradiance is enough to account for a major portion of the warming since the end of the Little Ice Age.”
-- The Advocates Point:
There is no evidence to support a natural cause theory. The Medieval Warm Period had regional temperature increases but on a global basis temperatures were far less than those of today. The sun’s variation in energy output is a very small amount (less than 1%) and the amount of sunlight has moved in the opposite direction since 1880 as determined by solar irradiance.
6. Are there severe consequences predicated? This subject is addressed in segment 5
7. Is there any additional scientific information presented concerting the debate? Yes, on General Circulation Models (GCMs) and CO2.
The next Segment (5) will contain advocate points and skeptic counterpoints by individual topics on the global consequences of global warming, in a similar format as this segment. The excerpts will come from the same two books as those utilized in this segment.
Happy Learning,
Harley
CLIMATE CHANGE – Segment 4
POINT AND COUNTERPOINT - EXCERPTS
ADVOCATE POINT From: A Global Warming Primer by Jeffrey Bennett
COUNTERPOINT From: Global Warming by Dedrick Robinson and Gene Robinson
ADVOCATE POINT: The first skeptic claim we hear about global warming is Earth is not warming up the way that logic predicts. Direct measurements from which we can infer global temperature go back to about 1880. The data show an overall gain of at least about 1.5 degrees F over the past century – which confirms that our world is warming. There is no doubt that human activity is adding carbon dioxide and other greenhouse gases to the atmosphere. We know the CO2 is from human activity because the rate at which humans are releasing CO2 and because natural sources are too small to account for the observed increase.
SKEPTIC COUNTERPOINT: There are actually two parts to the global warming theory and only one is controversial.
The first maintains that starting at some point around 1880, the global temperature began to increase and during that century and a quarter, it had risen by 1 to 1.5 degrees F. This point of global warming theory is uncontroversial.
The widespread controversy comes from the second portion of the global warming theory, that people have caused, and causing, the warming through artificially increasing the greenhouse effect by burning wood, coal, and petroleum products.
THE DEBATE ON THE HUMAN CAUSED FACTORS
ADVOCATE POINTS: The basic science of global warming can be summarized in three simple statements
SKEPTIC COUNTERPOINTS: The idea that CO2 drives the earth’s climate is firmly embedded in the public’s collective mind. In support, reference is made to Antarctic ice core records that say when there’s more CO2 in the atmosphere, the temperature increases. The reality is the opposite. Temperature generally changes in detailed records hundreds of years, or thousands of years, before CO2 and methane. If there is a cause and effect relationship involved between CO2 and temperature, temperature drives CO2, not the reverse.
The fact that temperature changes before CO2 should have been sufficient to falsify the theory of global warming, but global warming is no ordinary scientific theory. Its many ardent supporters were not about to let it be vanquished so easily. Attempting to patch up the theory, they proposed that a positive feedback exists with water vapor. The proposed mechanism is that in the ice core records, orbital change nudged temperature in a certain direction, say warming. This cause more evaporation, releasing more water vapor and CO2 into the atmosphere, which cause still more warming and so on, a classic positive feedback process.
The central question is whether such a positive feedback process actually occurs. It has yet to be demonstrated for the earth’s climate system, and it is possible that more water vapor in the atmosphere actually produces a negative feedback by increasing the number of clouds, which both reflect and absorb solar energy, causing cooling. Beyond this difficulty, there are other indications that such a process, if it occurs is not important. Clear evidence from ice core records and the annual seasonal change in temperature shows that water vapor feedback does not lead to run away temperatures.
THE ADVOCATES RESPONSE: It is true that in some cases, temperature changes measured in the ice core record appear to have preceded a rise in CO2, but this does not in any way change our understanding of cause and effect. In fact, it’s completely consistent with the idea that small changes in climate that are then amplified by feedbacks with CO2 and water vapor. In other words, the feedback processes, both the temperature and the CO2 concentration will rise or fall together, and at any given moment of any given place on Earth, one of the other may change first.
THE DEBATE ON THE NATURAL CAUSE FACTORS
THE ADVOCATES POINT: A few skeptics – including some with scientific training – have suggested that the warming may be occurring for natural reasons, rather than as a result of human activity. Could the Sun be the cause of the observed global warming? The sun does indeed vary in its energy output from year to year, though by a very small amount (much less than 1%). We know that even relatively small changes in the amount of sunlight reaching Earth can affect the climate. But we can be confident that changes in sunlight are not the cause of recent global warming, because the data shows that for recent decades (staring in 1880), the amount of sunlight has moved in the opposite direction as determined by solar irradiance measurements. Still, Earth’s climate is very complex and affected by many factors, both human and natural, so it’s worth exploring whether there might be any other natural process that can explain the observed warming. The primary way that scientists investigate this possibility is by using what we call models of the climate. Model “Conclusion: Today’s climate models work extremely well and demonstrate that global warming is caused by human factors such as the rising CO2 concentration.”
Source: IPCC
THE SKEPTICS COUNTERPOINT: Climate alarmists say they do include the effects of solar variations in general circulations models, but the effects are too small to amount to much. Yet, skeptics point to a number of recent studies with improved instrumentation suggesting that variations in the sun’s total irradiance is enough to account for a major portion of the warming since the end of the Little Ice Age. An observational record of the eleven-year sunspot cycle goes back to the early 1600s, and has been extended back another few hundred years using a radioactive carbon proxy. A plot of this data shows it correlates better with global temperature than does CO2.
THE ADVOCATES POINT: What about the Medieval Warm Period, when Greenland was “green’? The more important question which is whether the Medieval Warm Period is relevant to current global warming. The answer is a strong and definitive “no.” The reason is simple: Even though there was a Medieval Warm Period, the amount of warming at that time pales by comparison to the warming going on today. Careful studies indicate that the Medieval Warm Period was a regional phenomenon that affected the northern Atlantic much more than other parts of the world; globally, there was little if any overall warming during this period. In other words, the Viking colonization of Greenland was made possible by regional not global climate changes. Today’s warming, in contrast, is truly global.
Wait – didn’t I hear that the hockey stick graph has been discredited? Well, you probably have heard this, but it is not true. The original version of the “hockey stick” was published by climate scientist Michael Mann in 1998 and he used only a single data set. Skeptics jumped on it, claiming all kinds of reasons why the data should be doubted. The skeptics were so adamant that they convinced Congress to ask the National Research Council (NRC) to investigate. The NRC report, published in 2006, concluded that the graph and the data were fully valid.
SKEPTICS COUNTERPOINT: The famed “hockey stick” temperature graph lacking a Medieval Warm Period and Little Ice Age and showing no warming for the past thousand years until the twentieth century is especially controversial. According to global warming skeptics, the statistical and programming procedures used to stitch together several types of proxy temperature data from several areas included mistakes and questionable data. Alarmists respond that the mistakes do not change the conclusion and that more recent studies have produced similar results. Accepting the conclusion requires throwing out the results of hundreds of studies showing these distinct climatic periods did occur. It would also require ignoring historical records as well as observations. The climate alarmist community greeted “the hockey stick” with open arms because it did away with that pesky Medieval Warm Period. Alarmists never had a good answer for that and tried to ignore it. They admitted CO2 was much lower at that time. If it was, how could the climate have been warmer than now? The obvious answer was that something else was at work, and if so, why couldn’t it be at work now.
THE DEBATE ON THE RELIABILITY OF GENERAL CIRCULATION MODELS (GCMs)
ADVOCATES POINT: The first thing that any scientist will tell you about models that it’s not easy. As the old saying goes, “Prediction is hard, especially about the future. But hard is not the same as impossible, and today’s sophisticated climate models do a good job of “predicting” the climate as it is today. We can therefore have some confidence that these models should be at least modestly reliable in predicting what will happen in the future. So, let’s look in more detail at the common skeptic claims about modeling and see why the vast majority of scientists find these claims unconvincing.
Maybe the models are missing an important mitigating factor. For example, aren’t there uncertainties about the effects of clouds? It’s true that clouds are very complex, and their effects are still not fully understood. This fact opens the way for a skeptic argument that basically goes like this: Global warming means the world starts getting warmer and this increases evaporation from the oceans, which in turn means more clouds, which in turn reflect more sunlight, thereby stopping further warming. In other words, the claim is that clouds represent a negative feedback that acts to prevent global warming from getting too bad. The problem with this argument is that it ignores other effects. The additional evaporation that leads to the additional clouds also means there is more water vapor in the atmosphere, and the water vapor tends to amplify the effects of changes in the CO2 concentration. While there is some legitimate debate over which effect – the extra heating from water vapor or the extra cooling from clouds – is stronger on relatively short time scales, there is little doubt about water vapor’s amplifying role. Moreover, even for short time scales (years), current understanding of cloud physics has led most scientists to conclude that the heating effects are stronger than the cooling mass.
SKEPTICS COUNTERPOINT: It’s hard to admit that climate models might not be as reliable as the IPCC and the media say. Modelers state that their projections are only scenarios not predictions. The IPCC features them as forecast in their publications, especially highlighting them in their slick reports intended for government leaders and policymakers. As a result, GCMs have become the best known and most powerful type of evidence used to support the global warming theory.
Dozens of physical parameters go into the construction of a GCM. Each and every one of them has some sort of error or uncertainty, and these are cumulative. For many of the physical processes that the climate models depend on, the uncertainty is far greater than is generally realized, as much as fifteen times the supposed amount of climate forcing attributed to human use of coal and petroleum. It is unscientific to claim “scenarios” showing future warming have any validity at all when the errors involved in the procedure are greater than the effect shown on their graphs. It smacks of IPCC advocacy or worse to misleadingly label such graphs with experimental precision while cloaking the high degree of physical uncertainty in obscure supplemental material.
We are not sure whether increasing evaporation from the oceans would be a positive or a negative effect. A negative feedback? How could that be? Remember a basic fact. Water vapor also forms clouds, as well as being a gas in the atmosphere. Clouds reflect a lot of the incoming solar right back into space before it ever has a chance to warm the surface, increasing the earth’s albedo. Clouds also absorb a substantial portion of the solar energy that isn’t reflected as it passes down toward the earth’s surface. These two effects account for cloudy days being cooler in the summer than clear days. On the other hand, clouds increase the greenhouse effect tending to retain more of the energy that does reach the surface. This is why the temperature doesn’t drop as much on cloudy nights in the winter as clear nights. Scientists still are not sure whether the net effect of more clouds is to warm or cool the earth, an ambiguity reflected in how GCMs deal with clouds. The possibility exists that more water vapor in the air is a negative feedback instead of a positive. If so, the main feedback used in GCMs is incorrect. The entire global warming theory would then crumble.
ADVOCATE POINT: Given the complexity of the climate and the uncertainties of the models, isn’t it reasonable to think that other feedbacks may mitigate the threat? It’s certainly conceivable that the models could still be missing other factors that might mitigate future warming. However, if any such mitigating factors exist, they would have to have some rather strange properties. In particular, because they would by definition be factors that are not considered by current models, they would have to be both unimportant enough that they haven’t caused major failures in the model results through the present times and important enough to make a major impact on the model results for the future. We cannot completely rule out the possibility that such factors exist, but the odd properties make it see rather unlikely. This is a major reason why the vast majority of scientists reject the skeptic claims and instead conclude that the threat of global warming is every bit as bad as the models suggest.
SKEPTICS COUNTERPOINT: A central fact of physics is that greenhouse gases such as CO2 only absorb infrared energy at certain wavelengths or bands. The effect is logarithmic. At first, adding a little CO2 greatly increases absorption, but as concentration of the gas increases, much greater amounts of CO2 are required to produce the same amount of absorption, until the maximum absorption potential is reached. After that, adding more CO2 has no effect. This can be illustrated with an analogy. Imagine walking along a white-sand beach on a bright sunny day. Putting on a pair of sunglasses helps to ease the glare. This works because the lens of the sunglasses absorbs a sizable portion of the light, so it’s possible to see now without squinting. Imagine next putting on a second pair of sunglasses. The view becomes darker still, but the difference is not as great as from the first pair of sunglasses. Adding more pairs of sunglasses continues diminishing the light return until finally, no light passes through. With all the light now absorbed, adding another pair of sunglasses has not effect. It is the same with any greenhouse gas. When an absorption band of a particular gas is saturated, adding more of that gas has zero effect. For CO2, this is the real inconvenient truth, the one that limits the effect of CO2 as a greenhouse gas.
Three of CO2’s absorption bands are already at maximum absorption and the fourth competes with water vapor. Taking this fact into account, simple arithmetic shows that doubling the current amount of CO2 in the atmosphere should produce less than 0.6 C of warming. Doubling it again would result in a far smaller increase in temperature. The IPCC, however, estimates much more warming that this from GCMs which are programmed using positive water vapor feedback to greatly amplify the warming coming from CO2.
The unabbreviated version of the above can be found in the pdf document below.
POINT AND COUNTERPOINT - EXCERPTS
ADVOCATE POINT From: A Global Warming Primer by Jeffrey Bennett
COUNTERPOINT From: Global Warming by Dedrick Robinson and Gene Robinson
ADVOCATE POINT: The first skeptic claim we hear about global warming is Earth is not warming up the way that logic predicts. Direct measurements from which we can infer global temperature go back to about 1880. The data show an overall gain of at least about 1.5 degrees F over the past century – which confirms that our world is warming. There is no doubt that human activity is adding carbon dioxide and other greenhouse gases to the atmosphere. We know the CO2 is from human activity because the rate at which humans are releasing CO2 and because natural sources are too small to account for the observed increase.
SKEPTIC COUNTERPOINT: There are actually two parts to the global warming theory and only one is controversial.
The first maintains that starting at some point around 1880, the global temperature began to increase and during that century and a quarter, it had risen by 1 to 1.5 degrees F. This point of global warming theory is uncontroversial.
The widespread controversy comes from the second portion of the global warming theory, that people have caused, and causing, the warming through artificially increasing the greenhouse effect by burning wood, coal, and petroleum products.
THE DEBATE ON THE HUMAN CAUSED FACTORS
ADVOCATE POINTS: The basic science of global warming can be summarized in three simple statements
- Fact: Carbon dioxide is a greenhouse gas, by which we mean a gas that traps heat and makes a planet (like Earth of Venus) warmer than it would be otherwise.
- Fact: Human activity, especially the use of fossil fuels – by which we mean coal, oil, and gas, all of which release CO2 when burned – is adding significantly more of his heat-trapping gas to Earth’s atmosphere. The ice core data tell us that for the 1,000-year period to 1750 the atmospheric CO2 stayed very close to 280 parts per million; the dramatic rise that has taken it past 400 parts million today began when the industrial revolution began, which is when humans first began to use large amounts of fossil fuels.
- Inevitable Conclusion: We should expect the rising CO2 concentration to warm our planet, with the warming becoming more severe as we add more CO2.
SKEPTIC COUNTERPOINTS: The idea that CO2 drives the earth’s climate is firmly embedded in the public’s collective mind. In support, reference is made to Antarctic ice core records that say when there’s more CO2 in the atmosphere, the temperature increases. The reality is the opposite. Temperature generally changes in detailed records hundreds of years, or thousands of years, before CO2 and methane. If there is a cause and effect relationship involved between CO2 and temperature, temperature drives CO2, not the reverse.
The fact that temperature changes before CO2 should have been sufficient to falsify the theory of global warming, but global warming is no ordinary scientific theory. Its many ardent supporters were not about to let it be vanquished so easily. Attempting to patch up the theory, they proposed that a positive feedback exists with water vapor. The proposed mechanism is that in the ice core records, orbital change nudged temperature in a certain direction, say warming. This cause more evaporation, releasing more water vapor and CO2 into the atmosphere, which cause still more warming and so on, a classic positive feedback process.
The central question is whether such a positive feedback process actually occurs. It has yet to be demonstrated for the earth’s climate system, and it is possible that more water vapor in the atmosphere actually produces a negative feedback by increasing the number of clouds, which both reflect and absorb solar energy, causing cooling. Beyond this difficulty, there are other indications that such a process, if it occurs is not important. Clear evidence from ice core records and the annual seasonal change in temperature shows that water vapor feedback does not lead to run away temperatures.
THE ADVOCATES RESPONSE: It is true that in some cases, temperature changes measured in the ice core record appear to have preceded a rise in CO2, but this does not in any way change our understanding of cause and effect. In fact, it’s completely consistent with the idea that small changes in climate that are then amplified by feedbacks with CO2 and water vapor. In other words, the feedback processes, both the temperature and the CO2 concentration will rise or fall together, and at any given moment of any given place on Earth, one of the other may change first.
THE DEBATE ON THE NATURAL CAUSE FACTORS
THE ADVOCATES POINT: A few skeptics – including some with scientific training – have suggested that the warming may be occurring for natural reasons, rather than as a result of human activity. Could the Sun be the cause of the observed global warming? The sun does indeed vary in its energy output from year to year, though by a very small amount (much less than 1%). We know that even relatively small changes in the amount of sunlight reaching Earth can affect the climate. But we can be confident that changes in sunlight are not the cause of recent global warming, because the data shows that for recent decades (staring in 1880), the amount of sunlight has moved in the opposite direction as determined by solar irradiance measurements. Still, Earth’s climate is very complex and affected by many factors, both human and natural, so it’s worth exploring whether there might be any other natural process that can explain the observed warming. The primary way that scientists investigate this possibility is by using what we call models of the climate. Model “Conclusion: Today’s climate models work extremely well and demonstrate that global warming is caused by human factors such as the rising CO2 concentration.”
Source: IPCC
THE SKEPTICS COUNTERPOINT: Climate alarmists say they do include the effects of solar variations in general circulations models, but the effects are too small to amount to much. Yet, skeptics point to a number of recent studies with improved instrumentation suggesting that variations in the sun’s total irradiance is enough to account for a major portion of the warming since the end of the Little Ice Age. An observational record of the eleven-year sunspot cycle goes back to the early 1600s, and has been extended back another few hundred years using a radioactive carbon proxy. A plot of this data shows it correlates better with global temperature than does CO2.
THE ADVOCATES POINT: What about the Medieval Warm Period, when Greenland was “green’? The more important question which is whether the Medieval Warm Period is relevant to current global warming. The answer is a strong and definitive “no.” The reason is simple: Even though there was a Medieval Warm Period, the amount of warming at that time pales by comparison to the warming going on today. Careful studies indicate that the Medieval Warm Period was a regional phenomenon that affected the northern Atlantic much more than other parts of the world; globally, there was little if any overall warming during this period. In other words, the Viking colonization of Greenland was made possible by regional not global climate changes. Today’s warming, in contrast, is truly global.
Wait – didn’t I hear that the hockey stick graph has been discredited? Well, you probably have heard this, but it is not true. The original version of the “hockey stick” was published by climate scientist Michael Mann in 1998 and he used only a single data set. Skeptics jumped on it, claiming all kinds of reasons why the data should be doubted. The skeptics were so adamant that they convinced Congress to ask the National Research Council (NRC) to investigate. The NRC report, published in 2006, concluded that the graph and the data were fully valid.
SKEPTICS COUNTERPOINT: The famed “hockey stick” temperature graph lacking a Medieval Warm Period and Little Ice Age and showing no warming for the past thousand years until the twentieth century is especially controversial. According to global warming skeptics, the statistical and programming procedures used to stitch together several types of proxy temperature data from several areas included mistakes and questionable data. Alarmists respond that the mistakes do not change the conclusion and that more recent studies have produced similar results. Accepting the conclusion requires throwing out the results of hundreds of studies showing these distinct climatic periods did occur. It would also require ignoring historical records as well as observations. The climate alarmist community greeted “the hockey stick” with open arms because it did away with that pesky Medieval Warm Period. Alarmists never had a good answer for that and tried to ignore it. They admitted CO2 was much lower at that time. If it was, how could the climate have been warmer than now? The obvious answer was that something else was at work, and if so, why couldn’t it be at work now.
THE DEBATE ON THE RELIABILITY OF GENERAL CIRCULATION MODELS (GCMs)
ADVOCATES POINT: The first thing that any scientist will tell you about models that it’s not easy. As the old saying goes, “Prediction is hard, especially about the future. But hard is not the same as impossible, and today’s sophisticated climate models do a good job of “predicting” the climate as it is today. We can therefore have some confidence that these models should be at least modestly reliable in predicting what will happen in the future. So, let’s look in more detail at the common skeptic claims about modeling and see why the vast majority of scientists find these claims unconvincing.
Maybe the models are missing an important mitigating factor. For example, aren’t there uncertainties about the effects of clouds? It’s true that clouds are very complex, and their effects are still not fully understood. This fact opens the way for a skeptic argument that basically goes like this: Global warming means the world starts getting warmer and this increases evaporation from the oceans, which in turn means more clouds, which in turn reflect more sunlight, thereby stopping further warming. In other words, the claim is that clouds represent a negative feedback that acts to prevent global warming from getting too bad. The problem with this argument is that it ignores other effects. The additional evaporation that leads to the additional clouds also means there is more water vapor in the atmosphere, and the water vapor tends to amplify the effects of changes in the CO2 concentration. While there is some legitimate debate over which effect – the extra heating from water vapor or the extra cooling from clouds – is stronger on relatively short time scales, there is little doubt about water vapor’s amplifying role. Moreover, even for short time scales (years), current understanding of cloud physics has led most scientists to conclude that the heating effects are stronger than the cooling mass.
SKEPTICS COUNTERPOINT: It’s hard to admit that climate models might not be as reliable as the IPCC and the media say. Modelers state that their projections are only scenarios not predictions. The IPCC features them as forecast in their publications, especially highlighting them in their slick reports intended for government leaders and policymakers. As a result, GCMs have become the best known and most powerful type of evidence used to support the global warming theory.
Dozens of physical parameters go into the construction of a GCM. Each and every one of them has some sort of error or uncertainty, and these are cumulative. For many of the physical processes that the climate models depend on, the uncertainty is far greater than is generally realized, as much as fifteen times the supposed amount of climate forcing attributed to human use of coal and petroleum. It is unscientific to claim “scenarios” showing future warming have any validity at all when the errors involved in the procedure are greater than the effect shown on their graphs. It smacks of IPCC advocacy or worse to misleadingly label such graphs with experimental precision while cloaking the high degree of physical uncertainty in obscure supplemental material.
We are not sure whether increasing evaporation from the oceans would be a positive or a negative effect. A negative feedback? How could that be? Remember a basic fact. Water vapor also forms clouds, as well as being a gas in the atmosphere. Clouds reflect a lot of the incoming solar right back into space before it ever has a chance to warm the surface, increasing the earth’s albedo. Clouds also absorb a substantial portion of the solar energy that isn’t reflected as it passes down toward the earth’s surface. These two effects account for cloudy days being cooler in the summer than clear days. On the other hand, clouds increase the greenhouse effect tending to retain more of the energy that does reach the surface. This is why the temperature doesn’t drop as much on cloudy nights in the winter as clear nights. Scientists still are not sure whether the net effect of more clouds is to warm or cool the earth, an ambiguity reflected in how GCMs deal with clouds. The possibility exists that more water vapor in the air is a negative feedback instead of a positive. If so, the main feedback used in GCMs is incorrect. The entire global warming theory would then crumble.
ADVOCATE POINT: Given the complexity of the climate and the uncertainties of the models, isn’t it reasonable to think that other feedbacks may mitigate the threat? It’s certainly conceivable that the models could still be missing other factors that might mitigate future warming. However, if any such mitigating factors exist, they would have to have some rather strange properties. In particular, because they would by definition be factors that are not considered by current models, they would have to be both unimportant enough that they haven’t caused major failures in the model results through the present times and important enough to make a major impact on the model results for the future. We cannot completely rule out the possibility that such factors exist, but the odd properties make it see rather unlikely. This is a major reason why the vast majority of scientists reject the skeptic claims and instead conclude that the threat of global warming is every bit as bad as the models suggest.
SKEPTICS COUNTERPOINT: A central fact of physics is that greenhouse gases such as CO2 only absorb infrared energy at certain wavelengths or bands. The effect is logarithmic. At first, adding a little CO2 greatly increases absorption, but as concentration of the gas increases, much greater amounts of CO2 are required to produce the same amount of absorption, until the maximum absorption potential is reached. After that, adding more CO2 has no effect. This can be illustrated with an analogy. Imagine walking along a white-sand beach on a bright sunny day. Putting on a pair of sunglasses helps to ease the glare. This works because the lens of the sunglasses absorbs a sizable portion of the light, so it’s possible to see now without squinting. Imagine next putting on a second pair of sunglasses. The view becomes darker still, but the difference is not as great as from the first pair of sunglasses. Adding more pairs of sunglasses continues diminishing the light return until finally, no light passes through. With all the light now absorbed, adding another pair of sunglasses has not effect. It is the same with any greenhouse gas. When an absorption band of a particular gas is saturated, adding more of that gas has zero effect. For CO2, this is the real inconvenient truth, the one that limits the effect of CO2 as a greenhouse gas.
Three of CO2’s absorption bands are already at maximum absorption and the fourth competes with water vapor. Taking this fact into account, simple arithmetic shows that doubling the current amount of CO2 in the atmosphere should produce less than 0.6 C of warming. Doubling it again would result in a far smaller increase in temperature. The IPCC, however, estimates much more warming that this from GCMs which are programmed using positive water vapor feedback to greatly amplify the warming coming from CO2.
The unabbreviated version of the above can be found in the pdf document below.
| 04_cc_long_climate_science_point_--_segment_4.pdf |