08/28/2009
Truth and Other Enigmas, Harvard University Press 1978
This article gives a lengthy explication of McTaggart's argument for there being a contradiction in time. Author reconstructs the argument:
a) an event M is past, present or future
b) an event M is before, at the same time as, or after another event N
Crucial here is that the facts of kind a) cannot be reducible to facts of kind b). Apparently McTaggart's reasoning for this is that change is essential to time, but there is no change in the truth function of the fact 'M comes after N', or 'M came before N'. Such facts, if true, are eternally true and therefore don't involve change. (pg351) Now the problem is that an event M can be described using three mutually incompatible predicates (past, present, future). This leads to a contradiction in describing the event, thus time is an unreality.
Author considers a possible response: the predicates applying to event M isn't just 'past', 'present', 'future', but 'will be past', 'is present', and 'was future'-- building tenses into the predicate. But adding tense verbs into the predicates only pushes the further back, since now there are 9 different predicate combinations: 'was past', 'is past', 'will be past' and so on for 'present' and 'future'. In any case the contradiction can be generated again. (pg351-2)
A more sophisticated response employs 'token-reflexive' expressions (e.g. 'I', 'here', 'now'), which are like indexicals that change a sentence's truth conditions according to context. We then specify that token-reflexive expressions are essential to time-facts and resolve the apparent incompatibility (pg353). This response, author points out, trivializes McTaggart's argument since it could also be made for space or personhood, just as it was for time. Yet McTaggart doesn't make analogous arguments about space or personhood, so author thinks there is more to his argument.
The difference, author claims, between the argument about time and an analogous one about space is that token-reflexivity is essential to time but it isn't to space. (pg354) Author discusses how it is possible to have a description of objects in space that doesn't include the describer-- that has no 'spatially token-reflexive expressions in giving a description of the physical uinverse' (pg354)-- but the same is not possible for time. Author argues that any account of a sequence of events without token-reflexive expressions will leave the question 'but what is happening right now' unanswered, therefore the account will be incomplete. Another possibility is to think of an external observer seeing time as a fourth dimension that is static, similar to how a full spatial description of the world would be a static image in 3 dimensions. In a weird turn, author argues that what would be observed would be a 'model' of events, not the events themselves. (pg355)
The possible response to this essential aspect of time is to jettison the notion that there is one complete description of reality (pg356), but author admits he is partial to this. Instead, it appears the unreality of time is self-defeating, since our apprehension of the world is certainly temporal.
8/14/09
Farley, John - The Scientific Case for Modern Anthropogenic Global Warming
08/14/2009
Monthly Review, July-August 2008
This article tries to give some general scientific background for understanding the human causes of global warming, and rebut a series of arguments made by Alexander Cockburn that anthropogenic global warming is a myth.
The evidence for human-made global warming presented by author is fairly straightforward: when the sun's rays hit the earth, some is radiated back into the atmosphere, mostly as infrared light. This light gets trapped in the atmosphere by greenhouse gases, which are opaque to this light. The three gasses are water vapor, CO2, and methane. This undisputed greenhouse effect is already responsible for heating the planet from a surface temperature of -1F to 60F. The experimental data collected by Keeling in Hawaii since 1959 shows a steady increase in CO2 into the atmosphere, which is also undisputed. Further, it is possible to examine air bubbles in arctic ice that shows a rise in CO2 around the industrial revolution, after holding relatively steady for the last 10,000 years. Author claims the reason for the recent rise is the anthropogenic burning of fossil fuels and deforestation.
Author admits that water vapor is the largest contributor to the greenhouse effect, but CO2 represents from 9-26% depending on how the counting is done. Another aspect to consider is that adding to infrared opacity in the atmosphere might have no effect if the opacity is already 100%. Instead, increasing CO2 will affect the 'wings', the areas where opacity is lower. Author likens increasing CO2 in those areas to closing the windows in a hot house.
According to author, the major debate among scientists isn't whether 'climate forcing' by humans is happening (increasing the atmospheric temperature by 2.2-2.3F), but what the 'climate response' will be-- the feedback from the earth that may increase or decrease our forcing. Author presents evidence for the possibility of negative feedback (e.g. decreasing the temperature) and positive feedback (e.g. increasing the temperature). Author reports the general consensus to be for positive feedback, somewhere from 2.7 to 8.1F. Two effects might indicate positive feedback:
(P1)- Ice-albedo effect-- as the temperature rises, ice near the poles melts and exposes more earth, decreasing the earth's reflectance of ultraviolet and visible light, heating it.
(P2)- Increased water vapor-- warmer air can hold more water vapor than cool air can, increasing the opacity for infrared light and causing an additional greenhouse effect.
Then there is some evidence for possible negative feedback:
(N1)- If warmer temperatures create more clouds and clouds have a net cooling effect, this could reduce the anthropogenic effects of increasing CO2.
(N2)- Richard Lindzen's "adaptive iris" effect, which suggests that greater temperatures in the tropics will create fewer cirrus clouds that increase the "leakage" of infrared radiation, resulting in cooling.
The state of science makes it difficult to predict a priori whether there will be net positive or negative feedback, but author argues that if we can take the long-term historical evidence as accurate, the warming temperatures were higher than one would predict without positive feedback. So positive feedback is consistent with previous periods of non-anthropogenic global warming. Author gives evidence from the earth's past ice ages, which are 'almost unanimously' agreed to be because of changes in the earth's axis tilt (Milankovich cycle). Yet simple changes in sunlight doesn't result in the amount of cooling (or, later, warming) that took place-- suggesting positive feedback played a part in those cases. Author also discusses the modes temperatures changes that took place from 1600-1800.
Author then directly addresses Cockburn's 6 main arguments:
1- During the economic depression of the 1930s, burning of fossil fuels decreased 30%, but there was no decrease of CO2 in the atmosphere, thus the two are unrelated.
Response: If CO2 entering the atmosphere decreases by 30%, that means the rate of CO2 'flux' decreases 30%, not the CO2 'reservoir' that is already in the atmosphere. Cutting CO2 flux to zero would mean there would be an eventual lowering of the CO2 reservoir, but that didn't happen so we should not have expected it.
2- Water vapor is the biggest greenhouse gas and the effects from CO2 are negligible.
Response: Yes it is true that water vapor is a larger effect than CO2. But the CO2 effect is appreciable.
3- Earth's last ice age ended when the the earth tilted slightly on its axis, temperatures rose and then CO2 in the atmosphere rose. CO2 rises as a result of global temperature, not as a cause of it.
Response: That is a true account of 10,000 years ago. But there are many ways to increase temperatures in the climate, and in the last 200 years, CO2 rises preceded temperature rises.
4- The increase of CO2 comes naturally from the oceans, not the man-made burning of fossil fuels.
Response: Yes the ocean has lots of CO2 in it. But there are two kinds of CO2 molecules, since there are two carbon isotopes (heavy ones have one extra neutron)-- the heavy ones are about 1% of the total carbon atoms. In turns out that plants prefer the regular 12-weight-carbons when adding to their biomass (growing). Thus you'd expect to find fewer 13-weight-carbons in plants and their derivatives, fossil fuels; and that is what experiments have found. The CO2 in the atmosphere contains a lower concentration of 13C than the norm, suggesting that the CO2 in the atmosphere comes from lower 13C sources (e.g. fossil fuels). On ocean surfaces there is a higher concentration of 13C, and in the deep oceans a depleted amount of 13C. Moreover, evidence from the Maua Loa observatory in Hawaii shows an increase of 12C in the atmosphere.
5- Any addition of CO2 to the atmosphere by humans will be dissolved into the ocean within a year or two, making anthropogenic effects short-lived if at all.
Response: This is an old, persistent belief that CO2 will easily and quickly dissolve into ocean waters since it does so in pure water. Author argues that it isn't an issue of whether all the CO2 in the atmosphere can get into the oceans, it's an issue of how long it will take-- a 'transient' problem rather than a 'equilibrium' problem. Estimates from ocean chemists suggest it will take from 60 to 360 years for the biggest percentage of CO2 to dissolve into the oceans-- and that is talking about the reservoir-- not the flux!
6- Global warming forecasts are largely dependent on computer models, which are easily manipulated to show whatever scary but unrealistic outcome you want to get.
Response: Yes, computer models are suspect, but much of our evidence doesn't come from models but instead from historical observations and old-fashioned theory. Moreover, much of the controversy is about what kind of feedback there will be-- the climate response-- not the climate forcing evidence (that doesn't rely on computer models). If the climate response is a positive feedback like there was during ice-age transitions, this is more evidence for the IPCC's estimates that don't rely on computer models.
Monthly Review, July-August 2008
This article tries to give some general scientific background for understanding the human causes of global warming, and rebut a series of arguments made by Alexander Cockburn that anthropogenic global warming is a myth.
The evidence for human-made global warming presented by author is fairly straightforward: when the sun's rays hit the earth, some is radiated back into the atmosphere, mostly as infrared light. This light gets trapped in the atmosphere by greenhouse gases, which are opaque to this light. The three gasses are water vapor, CO2, and methane. This undisputed greenhouse effect is already responsible for heating the planet from a surface temperature of -1F to 60F. The experimental data collected by Keeling in Hawaii since 1959 shows a steady increase in CO2 into the atmosphere, which is also undisputed. Further, it is possible to examine air bubbles in arctic ice that shows a rise in CO2 around the industrial revolution, after holding relatively steady for the last 10,000 years. Author claims the reason for the recent rise is the anthropogenic burning of fossil fuels and deforestation.
Author admits that water vapor is the largest contributor to the greenhouse effect, but CO2 represents from 9-26% depending on how the counting is done. Another aspect to consider is that adding to infrared opacity in the atmosphere might have no effect if the opacity is already 100%. Instead, increasing CO2 will affect the 'wings', the areas where opacity is lower. Author likens increasing CO2 in those areas to closing the windows in a hot house.
According to author, the major debate among scientists isn't whether 'climate forcing' by humans is happening (increasing the atmospheric temperature by 2.2-2.3F), but what the 'climate response' will be-- the feedback from the earth that may increase or decrease our forcing. Author presents evidence for the possibility of negative feedback (e.g. decreasing the temperature) and positive feedback (e.g. increasing the temperature). Author reports the general consensus to be for positive feedback, somewhere from 2.7 to 8.1F. Two effects might indicate positive feedback:
(P1)- Ice-albedo effect-- as the temperature rises, ice near the poles melts and exposes more earth, decreasing the earth's reflectance of ultraviolet and visible light, heating it.
(P2)- Increased water vapor-- warmer air can hold more water vapor than cool air can, increasing the opacity for infrared light and causing an additional greenhouse effect.
Then there is some evidence for possible negative feedback:
(N1)- If warmer temperatures create more clouds and clouds have a net cooling effect, this could reduce the anthropogenic effects of increasing CO2.
(N2)- Richard Lindzen's "adaptive iris" effect, which suggests that greater temperatures in the tropics will create fewer cirrus clouds that increase the "leakage" of infrared radiation, resulting in cooling.
The state of science makes it difficult to predict a priori whether there will be net positive or negative feedback, but author argues that if we can take the long-term historical evidence as accurate, the warming temperatures were higher than one would predict without positive feedback. So positive feedback is consistent with previous periods of non-anthropogenic global warming. Author gives evidence from the earth's past ice ages, which are 'almost unanimously' agreed to be because of changes in the earth's axis tilt (Milankovich cycle). Yet simple changes in sunlight doesn't result in the amount of cooling (or, later, warming) that took place-- suggesting positive feedback played a part in those cases. Author also discusses the modes temperatures changes that took place from 1600-1800.
Author then directly addresses Cockburn's 6 main arguments:
1- During the economic depression of the 1930s, burning of fossil fuels decreased 30%, but there was no decrease of CO2 in the atmosphere, thus the two are unrelated.
Response: If CO2 entering the atmosphere decreases by 30%, that means the rate of CO2 'flux' decreases 30%, not the CO2 'reservoir' that is already in the atmosphere. Cutting CO2 flux to zero would mean there would be an eventual lowering of the CO2 reservoir, but that didn't happen so we should not have expected it.
2- Water vapor is the biggest greenhouse gas and the effects from CO2 are negligible.
Response: Yes it is true that water vapor is a larger effect than CO2. But the CO2 effect is appreciable.
3- Earth's last ice age ended when the the earth tilted slightly on its axis, temperatures rose and then CO2 in the atmosphere rose. CO2 rises as a result of global temperature, not as a cause of it.
Response: That is a true account of 10,000 years ago. But there are many ways to increase temperatures in the climate, and in the last 200 years, CO2 rises preceded temperature rises.
4- The increase of CO2 comes naturally from the oceans, not the man-made burning of fossil fuels.
Response: Yes the ocean has lots of CO2 in it. But there are two kinds of CO2 molecules, since there are two carbon isotopes (heavy ones have one extra neutron)-- the heavy ones are about 1% of the total carbon atoms. In turns out that plants prefer the regular 12-weight-carbons when adding to their biomass (growing). Thus you'd expect to find fewer 13-weight-carbons in plants and their derivatives, fossil fuels; and that is what experiments have found. The CO2 in the atmosphere contains a lower concentration of 13C than the norm, suggesting that the CO2 in the atmosphere comes from lower 13C sources (e.g. fossil fuels). On ocean surfaces there is a higher concentration of 13C, and in the deep oceans a depleted amount of 13C. Moreover, evidence from the Maua Loa observatory in Hawaii shows an increase of 12C in the atmosphere.
5- Any addition of CO2 to the atmosphere by humans will be dissolved into the ocean within a year or two, making anthropogenic effects short-lived if at all.
Response: This is an old, persistent belief that CO2 will easily and quickly dissolve into ocean waters since it does so in pure water. Author argues that it isn't an issue of whether all the CO2 in the atmosphere can get into the oceans, it's an issue of how long it will take-- a 'transient' problem rather than a 'equilibrium' problem. Estimates from ocean chemists suggest it will take from 60 to 360 years for the biggest percentage of CO2 to dissolve into the oceans-- and that is talking about the reservoir-- not the flux!
6- Global warming forecasts are largely dependent on computer models, which are easily manipulated to show whatever scary but unrealistic outcome you want to get.
Response: Yes, computer models are suspect, but much of our evidence doesn't come from models but instead from historical observations and old-fashioned theory. Moreover, much of the controversy is about what kind of feedback there will be-- the climate response-- not the climate forcing evidence (that doesn't rely on computer models). If the climate response is a positive feedback like there was during ice-age transitions, this is more evidence for the IPCC's estimates that don't rely on computer models.
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