Anthropogenic Climate Change Exists
I thank my opposition for accepting this debate.
This discussion is about Climate Change Anomalies from the years 1900 to 2200 (see comments section), and whether they are anthropogenic. Anomalies are deviations from "schedule" weather cycles, and can include both hot and cold extremes, making "global warming" only half of this discussion.
So, right off the bat, temperature anomalies began rising just after the year 1900 .
As shown in the following chart , this corresponds closely with a recent rise in CO2 emissions. This chart shows that CO2 levels have always travelled in cycles, but broke their most recent scheduled downward cycle to reach their highest level in over 400,000 years. In a sense, one might say nature did half the work on CO2 and the human race took it from there.
Correllation is obviously not causation, but the mechanics that link CO2 to temperature have been well documented.
Atmospheric Greenhouse Effects: A Review 
CO2 does not deflect visible light, which is what originally makes it to the earth's surface. Upon reaching the earth's surface, visible light is partially absorbed by the earth or water, and partially reflected. The reflection process lowers its energy level, turning it into infrared light. CO2 deflects infrared light. So CO2's reflective properties for the earth are one-directional. Visible light pass downward unperturbed, but upward infrared is deflected downwards / sideways. This effectually increases the amount of light striking the surface of the planet, which at current greenhouse levels protects life from the freezing cold of space, and at future levels threatens to roast life - not to death, but to ecological disequilibrium.
Oceanic Greenhouse Effects: A Review
The oceans currently absorb atmospheric CO2 and are undergoing a resulting drop in pH. They are also currently absorbing most of the extra heat from the sun, and therefore are experiencing a rise in temperature. Once they heat to a certain point, the oceans are expected to start releasing CO2 back into the atmosphere, which may include massive reserves that have been down there for millions of years.
However, before the oceans can truly begin warming, the ice caps have to melt.
And as we can see here , though the ice caps have shown about a half-century lag behind the thinner, more responsive atmosphere, they are roughly 1 million square kilometers smaller than they ought to be, as of 2014.
It appears that climate anomalies are closely associated with CO2 levels, that CO2 levels are primarily anthropogenic and will continue to be so until the next 'natural' CO2 spike roughly one hundred thousand years from now (chart 1), and that the greenhouse mechanisms behind all this are straightforward and established.
Correlation plus a theory is not proof CO2 dominates climate
Over geological time, clearly climate has been dominated by factors other than CO2. On the geological time scale, we are currently in an unusual period of low temperatures and low CO2. It a very complicated picture, proving that climate is far more than just CO2.
Pro shows the CO2 data for the past 650,000 years.Temperature follows the same pattern, only CO2 follows temperature. The graphs are here [2. http://www.geocraft.com...] If the graphs are time aligned, the result is not that CO2 causes warming. Quite the opposite, CO2 rises about 800 years after temperature rises. Warming causes CO2 because warmer oceans cannot dissolve as much CO2.
In 2013 the prestigious journal Nature published an up to date scientific reconstruction of climate for the past 2050 years. [3. http://www.nature.com...] It shows that over the period climate varied by about as much as the present warming, with both the Roman Period and the Medieval Warm Period warmer. It remains possible that CO2 is contributing significantly to current warming, but the natural variations are so large that CO2 might be inconsequential. Current climate science has no explanation for the major climate variations of the past 2000 years. That's why the discredited global warming hockey stick attempted to prove there were no past variations. Pro has the burden to prove CO2 dominates. I say it's unlikely CO2 dominates, but no one really knows.
“The Antarctic surge is so big that overall, although Arctic ice has decreased, the frozen area around both poles is one million square kilometres more than the long-term average.” [5. http://www.dailymail.co.uk...]
To accurately predict future climate, computer models must be proved to be reliable. We know the models did not predict ice formation in the Antarctic nor pre-1900 climate variations. In addition, global warming has essentially ceased since 1997, [6. http://wattsupwiththat.com...] so a check on the accuracy of climate models is how well this pause is predicted. Sscientists predicting CO2 crisis use many variations of computer models. The collections are called CMIP3 and CMIP5, with CMIP5 the very latest.
... Climate models cannot simulate past surface temperatures, precipitation or sea ice area. Those are basic components of Earth’s climate. … The concern about the latest slowdown in warming was addressed by a recent scientific study by Von Storch, et al. (2013) “ Can Climate Models Explain the Recent Stagnation in Global Warming? ” The one-word answer to the title question of their paper is, “No”. They stated: However, for the 15-year trend interval corresponding to the latest observation period 1998-2012, only 2% of the 62 CMIP5 and less than 1% of the 189 CMIP3 trend computations are as low as or lower than the observed trend. Applying the standard 5% statistical critical value, we conclude that the model projections are inconsistent with the recent observed global warming over the period 1998- 2012.
[7. Tisdale, Bob (2013-09-23). Climate Models Fail (Kindle Locations 276-291)] The Von Storch paper is available free in draft format [8. http://www.mpimet.mpg.de...]
My opponent claims that the "climate competitors" of CO2 account for an unknown portion of temperature anomaly. We actually have a comprehensive understanding of both chemical and physical factors of climate change.
He is correct that if we compared a chart of barbecue emissions with a chart of atmospheric heating, it would be absurd to assume barbecuing causes global warming.
However, if we measured the effects of shortwave radiation, longwave radiation, the manner in which each passes through clouds, the effects of vegetation, the net greenhouse effects of the oceans, and emissions of non-barbecuing greenhouse gases, we would be in a much better position to say whether barbecue emissions cause global warming.
Con correctly argues that the barbecue theory would be defeated by showing that the volume of charcoal is insufficient. So back to the discussion, what's the volume of CO2 output? The United States alone has a crude oil energy output of 19,420,000,000,000,000 British Thermal Units . Is this comparable to backyard barbecues?
The fifth report by the International Panel of Climate Change  claims that "Human influence on the climate system is clear. This is evident from the increasing greenhouse gas concentrations in the atmosphere, positive radiative forcing, observed warming, and understanding of the climate system." It presents evidence that the CO2 output of fossil fuels and anthropogenic land usage together total are nearly three times higher than the CO2 output of rock weathering, volcanic activity, total respiration of life forms, forest fires and freshwater outgassing combined.
Con offers a reconstruction of the last 650,000,000 years, but this is a discussion about the years 1900 to 2200. Geological time is slow enough to be irrelevant in the 3-century blip we are discussing. In this context, hundreds of millions of years is simply beyond a defensible scale. CO2 levels are not higher than what they were 100,000,000 years ago before the existence of humans, but they are higher than they have been in 400,000 years.
"Current climate science has no explanation for the major climate variations of the past 2,000 years." I have BOP for my claims about modern climate observations, but Con needs to provide a source for this claim.
"That's why the discredited global warming hockey stick attempted to prove there were no past variations." Source and specifics would be appreciated.
Con claims that CO2 follows temperature rather than causing temperature, claiming the graphs are in a link. I would appreciate if Con could import these graphs into DBO and reference them as individual images, as I am unable to find an image that matches this description in the link provided.
The Nature article quoted by Con demonstrates that solar insulation changed the Earth's climate more in 2,000 years than the human race has in 250 years. It does not suggest that the factors it discusses could compete with the human race during industrial and post-industrial ages. Again, this is a discussion about a 300 year timespan.
"Historically, Arctic ice melts when Antarctic ice increases in a cycle of 40 to 60 years called the Pacific Decadal Oscillation (PDO)." The Pacific Decadal Oscillation has no relation to the absorption of energy by the oceans from the years 1970 to 2010, which have shown a strong increase in net energy both in the liquid oceans and in the polar ice caps.
“The Antarctic surge is so big that overall, although Arctic ice has decreased, the frozen area around both poles is one million square kilometres more than the long-term average.” Both Arctic and Antarctic temperatures are supposed to be far below freezing, and neither will commence a serious level of shrinking until they reach the melting temperature of water. As the top of the ice caps melt, the water runs down and is cooled by the ice below, slightly reducing or maintaining the total mass of the ice while possibly increasing the total area. However, it also increases the average temperatures of the Antarctic and Arctic.
Since 2000, CO2 has risen by 54% with no increase in global temperatures.
The IPCC cannot explain why a 54% increase in CO2 produced no increase in temperature. As described in , Von Storch systematically ran all the IPCC computer models of the climate, and found that the actual temperatures for the last 17 years fell outside the model predictions. That's after the models had been tweaked using knowledge of the lack of global warming. The models still could not describe the past, so clearly they cannot be counted on to predict the future.
Pro only offers at base the fallacious logic that correlation means causation. But when CO2 increases by 54% in the past 17 years, and there is no increase in global temperature, then even the correlation claim fails.
Solar activity correlates well with global temperature for the past 17 years, for the entire 20the century and for as long as records of sunspot activity have been kept, which is back through the Middle Ages. Solar activity is discounted by CO2 theorists on the grounds that the measured irradiance of the sun, i.e.. the heat output, has not changed enough in recent decades to account for the temperature changes. However, solar activity produces changes in cosmic ray levels, and there is a theory that cosmic rays have an effect that changes cloud cover. The solar cosmic ray theory is also one of correlation, and cannot be considered causation until the mechanism is proved. However, unlike CO2 theory, the correlation actually holds over long and short periods.
There is a close correlation of solar sunspot activity and global temperature for the past century. [10. http://www.tmgnow.com...]
The past 17 years has been at the leveling off and start of a downward trend in sunspots after a period of increase during the 1980s and 1990s. [11. http://notrickszone.com...]
Historical reconstruction shows CO2 does not dominate climate
I pointed to reconstructions of climate for the distant past and the for the past 2000 years to show that climate has varied more than in recent years, and without any apparent relation to atmospheric CO2 levels. Pro argues that past climate doesn't count because we are only discussing the past century and the next century. Past climate counts because the laws of physics do not change at all over time. Consequently, if factors other than CO2 have always dominated climate, then it's unreasonable to suppose that a new CO2-only physics began recently. Pro's principle argument is that correlation proves causation. If there was no such correlation in the past, that is not sustained. Since the chance correlation only applies for a short time, it's important to Pro's case that we not look at the hundreds, thousands, and millions of years when there was no such correlation.
Global warming hockey stick discredited
The global warming hockey stick was presented in the 2000 IPCC report. It purported to show that the Medieval Warm Period and the Little Ice Age were local to Europe and that climate had not changed substantially in the past 1000 years, until the warming from 1983-1997. The statistical error used in the calculation yielding the hockey stick was discovered by McKitrick. [12. "The Mann et al Northern Hemisphere 'Hockey Stick': A Tale of Due Diligence." published in "Shattered Consensus" edited by Patrick Michaels]. A good summary by a scientist who believes in human-caused global warming is from the MIT magazine Technology Review. [13. http://www.technologyreview.com...] The Wikipedia article, heavily biased towards CO2 theory claims that the hockey stick has since been proved because a recent analysis shows that recent temperatures were higher than the Medieval Warm Period [14. http://en.wikipedia.org...] However, the accompanying graph shows that the MWP and the Little Ice Age existed as worldwide climate change, which is what the hockey stick was mainly supposed to disprove. The most recent reconstruction  clearly disproves the hockey stick.
CO2 follows temperature increase
That CO2 lags temperature in past climate is well known, but I apologize for giving the wrong link in the previous round. A journal article published in 2012 gives the result:
“Our analyses of ice cores from the ice sheet in Antarctica shows that the concentration of CO2 in the atmosphere follows the rise in Antarctic temperatures very closely and is staggered by a few hundred years at most,” - Sune Olander Rasmussen
[15. Watt provides graphs and links the Rasmussen paper http://wattsupwiththat.com...]
Another set of graphs showing the lag is given at [16. http://joannenova.com.au...]
Future CO2 levels are unknown
I noted that even if CO2 dominates climate, there is no confident prediction of future CO2 levels. Nearly everyone agrees that the world is running out of fossil fuels, so there is an aggressive search for alternatives. A technological breakthrough, or a simple substantial rise in the price of oil could substantially lower the rate of CO2 increase. Pro did not respond.
"Since 2000, CO2 has risen by 54% with no increase in global temperatures"?
Putting aside that ten years is only three percent of our three-century discussion, the decade from 2000-2010 actually experienced the highest average temperature anomaly of any decade since before 1900.
This is why the fifth IPCC report's "Summary for Policy Makers" boldly stated that "each of the last three decades has been successively warmer at the Earth’s surface than any preceding decade since 1850," and could also be why CON provides no source for his claim that the years 2000 through 2010 have "experienced no increase in global temperatures."
Hans Von Storch told the House of Representatives in 2006 that "Based on the scientific evidence, I am convinced that we are facing anthropogenic climate change brought about by the emission of greenhouse gases into the atmosphere."
CON has attempted to represent Hans Van Storch as follows:
"As described in , Von Storch systematically ran all the IPCC computer models of the climate, and found that the actual temperatures for the last 17 years fell outside the model predictions."
Von Storch is not an author of CON's eighth source. The source has fifteen authors, but none are named Von Storch.
These fifteen authors summarize their own work as follows: "We demonstrate that considerable ambiguity exists in the choice of parameters, and present and compare three alternatively tuned, yet plausible configurations of the climate model. The impacts of parameter tuning on climate sensitivity was less than anticipated."
At no point do they imply that "the actual temperatures for the last seventeen years fell outside model predictions."
Sunspot activity should affect climate, and if we examine the blue shades of the following "climate change anomalies" chart , we see sunspots match the evidence provided by CON in relation to both sunspots and Pacific Decadal Oscillation, with the dip in temperatures at or near the center of the 20th century.
The blue shading represents models that only account for "natural forcings" such as Solar Sunspot Activity and Pacific Decadal Oscillation. The pink shading represents models that account for "both natural and anthropogenic forcings." This chart demonstrates the sharp contrast in these competing models, showing that sunspots and other natural forcings should provide a near-flat average global temperature (with curves similar to CON's first round 3 image in North America, Europe, and Africa) while anthropogenic forcings should show a sharp rise. Observations are given by the black lines, and appear to agree more with the "anthropogenic & natural" models than with the "natural" models alone. It appears that anthropogenic forcings have sharper relevance than sunspots.
Con narrates his round 2 and my round 3 as follows:
"I pointed to reconstructions of climate for the distant past and the for the past 2000 years to show that climate has varied more than in recent years, and without any apparent relation to atmospheric CO2 levels. Pro argues that past climate doesn't count because we are only discussing the past century and the next century."
It would be a drastic mistake to argue that "past climate doesn't count," and I thank CON for bringing this potential misunderstanding to my attention.
I argued that "The Nature article quoted by Con demonstrates that solar insulation changed the Earth's climate more in 2,000 years than the human race has in 250 years." That is to say, the rate at which solar insulation changed the Earth's climate was more than (250 / 2000 = 0.125 ) 12.5% of our current rate of Climate change. Consistent change matters more to larger time frames, rate of change matters more to smaller time frames. This is not because the laws of physics change, in fact this is demonstrable in physics and mathematics.
Because force = mass * acceleration, a constant net force of one Newton can accelerate a 1,000 kilogram car to 299,792,458 meters per second (speed of light) in 83 hours, 12 minutes [299,792,458 ms^2 / (1,000 kg * 60 s * 60 min) = 83.2 hr], but in the first hour will only bring the speed of the car to 3.6 meters per second [(60 s * 60 m) / 1,000 kg), or just over eight miles an hour.
The longer the time measurement, the more relevant the "rate of change" or the "rate of rate of change" or the "value of the exponent," while the shorter the timespan, the more relevant the "application of force" or the "constant" or the "variable" or the "coefficient." The laws of physics and mathematics all but guarantee that the dominant force of climate change in a 300 year timespan is different from the dominant force of climate change in a 100,000,000 year timespan.
The last 50 years of climate anomalies demonstrate that the next 200 years of climate anomalies will be dominantly anthropogenic,
while CON's arguments are founded on a combination of 1) the last 600 million years of climate change and 2) the specific decade of 2000-2010. Does he somehow mean that solar, volcanic, botanic, and other natural factors will accelerate their rate of influence by 100,000 times over for the first time in over 600,000,000 years?
CO2 follows temperature increase in ice sheets with a lag of a few hundred years when assessing a timespan of 20,000 years, which is why CON's fifteenth source numbers its X-axis in units of 1000 years before 1950.
The CO2 level of an ice sheet is measured by the CO2 level, while the temperature of the ice sheet is measured by the deuterium level. Scientists aren't sure exactly how long it takes for deuterium differences to show up in ice caps, which is why CON's fifteenth source states "Our analyses of ice cores from the ice sheet in Antarctica shows that the concentration of CO2 in the atmosphere follows the rise in Antarctic temperatures very closely and is staggered by a few hundred years at most," rather than asserting that they have reversed the Greenhouse Effect. Their overall point is that the two measurements correllate.
The 2013 IPCC report states that "Climate change models have improved since the AR4. Models reproduce observed continental-scale surface temperature patterns and trends over many decades, including the more rapid warming since the mid-20th century and the cooling immediately following large volcanic eruptions (very high confidence)." I think we can all agree that Michael Mann was wrong ten years ago, and that the graph of climate anomalies is not shaped like a hockey stick, especially since that's not the topic of the debate I instigated, of the points I have argued, or of the sources I have cited.
"Total Sea Ice is at a High"?
Which is more relevant to "total sea ice" - area, or volume? CON made an argument about area, I made arguments about 1) volume and 2) temperature. Melting the ice caps reduces the volume, but the ice flows down and refreezes, which both warms the temperature and expands the area. Temperature is more closely linked to this debate than volume OR area. It has nothing to do with Al Gore, and the PDO is a mere blip on climate anomaly grids.
"Future CO2 levels are unknown"?
"Once they heat to a certain point, the oceans are expected to start releasing CO2 back into the atmosphere, which may include massive reserves that have been down there for millions of years." - Me, round 1, CON has yet to respond.
A technological breakthrough will not allow sunspots to catch up with Anthropogenic Climate Change before 2200. It will take them tens of thousands or even millions of years.
"Most aspects of climate change will persist for many centuries even if emissions of CO2 are stopped. This represents a substantial multi-century climate change commitment created by past, present and future emissions of CO2." 
CO2 has increased by 54% in past 17 years with no global warming, and CO2 theory cannot explain why
My primary reference for the claim that that IPCC models cannot explain the 17 year lack of global warming is Tinsdale's book “Climate Models Fail” . Tinsdale provides a book length comparison of IPCC model results showing that what actually happened in climate was outside of the error band of model predictions.
Tinsdale also referenced the Mauritsen paper, which I linked in . Like Von Storch, it shows that no reasonable tweak in the IPCC models can bring then into agreement with what actually happened.
If CO2 dominated climate in the 20th century, then temperature should have risen monotonically through the century. If fact, there was a sharp decline at the beginning of the century and long gradual decline from about the 40s through the 60s. The general trend is upwards, but a general upward trend is what we would expect if sunspots dominated climate. I presented the sunspot graph previously, but here is a nicer rendition [18. http://www.paulmacrae.com...]
Temperature is closely following sunspot activity, but not CO2, through 2000 The continuation, below, shows the pause in global warming post-2000 is consistent with the sunspot cycle having peaked. [19. http://wattsupwiththat.com...]
The 17 year pause in global warming is causing great consternation among scientists who previously believed CO2 predominated. A news report by Voosen summarizes the widespread recognition among scientists that the models are not working, and that some major factors are missing, although among CO2 advocates, there is no agreement among CO2 theorists as to what is wrong. [20. http://www.eenews.net...]
Pro's  shows that natural forcing of climate is only a minor part of the model predictions. However, Pro's figure shows is that the model predictions are completely wrong. Temperature was supposed to rise sharply after 2000, as the figure shows, but it did not. Models proved wrong cannot be relied upon for future predictions.
As Voosen documents, in the IPCC models, sunspots are only modeled as having a direct irradiance effect, and that effect is negligible for the 20th century through the present. Something else is happening that gives sunspots a much greater influence on climate.
Total sea ice is at a high
Pro's initial contention was that vanishing Arctic sea ice proves that CO2 dominates climate. That's wrong on two counts. Correlation does not prove causation. Also, global warming is global, so it cannot be that Arctic ice measures warming but Antarctic ice does not. In the last round, Pro changed his position and argued that total ice is important and not sea ice. But total ice has been decreasing since the early 1800s, well before any claim of anthropogenic warming. [21. http://www.davidarchibald.info...] Total ice shrinking doesn't say anything about the cause.
Pro claimed that melting land ice in Antarctica caused the increase in sea ice. That's impossible, because 99.9% of Antarctica has never gotten warm enough for ice to melt. There is a tiny peninsula that goes far enough north to occasionally have some melting, but that's negligible.
Future CO2 levels are unknown
Pro speculates that once there is any warming from anthropogenic CO2 it will take 10,000 years or even millions of years to correct. Pro agrees that warming causes the release of CO2 from the oceans. That does not address the issue of what future CO2 levels will be. It only says that if there is warming from some cause, that the CO2 levels in the atmosphere would be higher, after some delay, than if CO2 were not released from the ocean. We know it is not the case that warming causes a runaway of temperature due to the release of CO2 causing further warming. The data by Rasmussen  shows that CO2 goes up and down following temperature with a lag of a few hundred years, and that is true when either temperatures or CO2 levels are higher than present. It cannot matter whether there was one degree of warming due to sunspots or due to anthropogenic CO2, if any warming were to cause a CO2 induced runaway of temperature, it would have shown up in the temperature and CO2 variation of the past 250,000 years, and it has not happened.
All of the IPCC models assume that CO2 levels in the atmosphere are dominated by a continuing exponential rise in anthropogenic CO2. But fossils fuels are unquestionable being exhausted, so it is impossible for CO2 levels from burning fossil fuels to continue to rise exponentially. The only question is when anthropogenic CO2 will fall below the assumed exponential increase. Prof. David Archibald, an expert on fossil fuel reserves claims, “At best, we might get to about 600 ppm ...” [21. p.91] As fossil fuels become scarce the price will rise, which will lead to the use of alternatives like nuclear power, which is present only marginally more expensive than fossil fuels. But let's suppose that the 600 ppm level is reached at the end of the century. That's a 56% increase in CO2. But the 54% increase in CO2 in the past 17 years produced no net increase in global temperature. Because scientists agree CO2 warming is logarithmic, the same percentage increase should produce the same amount of warming. The CO2 warming of the past 17 years was canceled by natural phenomena not in the climate models, so Pro's claim that the climate problem is solved is false.
Is 600 ppm total CO2 is the correct number? I don't, and no one knows for sure. The upper limits and the future rates of CO2 production are major unknowns that make it impossible for Pro to meet his burden of proof.
The real world evidence says the opposite. In late 2007, Dr. Roy Spencer of the University of Alabama published a paper analyzing data from the Aqua satellite. Based on the response of tropical clouds, Dr. Spencer demonstrated that the feedback is negative. He calculates a 0.5°C warming for a doubling of the pre-industrial carbon dioxide level. Global warming, as caused by carbon dioxide, is real but it is also minuscule, and will be lost in the noise of the climate system.
"NASA data, which I cited in , shows there has been no global warming for 17 years."
So how do we have two competing sources for what should be the same information?
PRO  - IPCC
CON  - NASA?
If we look closely, CON's  doesn't actually reference NASA, it references wattsupwiththat.com. The wattsupwiththat article uses RSS data, not NASA data.
RSS, or Remote Sensing Systems, does not measure temperatures using a thermometer, it takes readings of microwaves, as explained on its homepage http://www.remss.com...;
The data demonstrates that microwaves are not "net heating" the earth, but CON and the wattsupwiththat article argue that the earth itself is not being warmed. When measured by thermometers throughout the globe, IPCC and NASA sources have shown that the earth clearly is being warmed.
CON's  is a particularly ironic source in the context of this debate, during which CON has advocated sunspots as an alternative temperature explanation to CO2.
CON argues that "decadal average" means that the meaning of "anomaly" is reset every decade. The IPCC actually addressed this concern by setting every decadal average relative to the same constant (in this case, "Anomalies are relative to the mean of 1961−1990.").
"My primary reference for the claim that that IPCC models cannot explain the 17 year lack of global warming is Tinsdale's book “Climate Models Fail” ." - CON
The existence of a book title is not an argued debate point. If CON has read Tisdale's book, he should be able to explain and present what he learned in this debate. Otherwise, I should be having this debate with Bob Tisdale.
"Tinsdale provides a book length comparison of IPCC model results showing that what actually happened in climate was outside of the error band of model predictions." - CON
Which model predictions do CON and Tisdale speak of? Because when the IPCC compared model predictions to observations, the temperature observations were outside the 'natural forcings' band of model predictions, and well withing the 'natural and anthropogenic forcings' band of model predictions. This was part of what I presented in round 4.
"Tinsdale also referenced the Mauritsen paper, which I linked in " - CON
CON  references Tinsdale, not Mauritsen.
"Temperature was supposed to rise sharply after 2000, as the figure shows, but it did not. Models proved wrong cannot be relied upon for future predictions."
Perhaps CON missed this: the blue shading is the natural, absence-of-man prediction; the pink shading is the natural + anthropogenic predictions; and the black line is the reading taken by the thermometers. The black line is consistent with the blue shading for the antarctic region, seems indecisive for the Southern Ocean, and correllates with the pink shading for the Arctic, North America, Europe, Asia, the North Pacific, the North Atlantic, Africa, the South Pacific, South America, the South Atlantic, the Indian Ocean, Australia, and Antarctica.
"Pro's initial contention was that vanishing Arctic sea ice proves that CO2 dominates climate." - CON
PRO's initial contention was actually that temperature anomalies correspond to a rise in CO2 as predicted by the greenhouse effect, and demonstrated by sea ice temperature, sea ice mass, climate temperature, ocean temperature, and ocean PH.
"Correlation does not prove causation." - CON
20th century physics consisted of bombarding particles into each other and measuring the deviation of their paths. This was well-tested far beyond being a correlation argument, to the point that physicists predict photonic behavior with laser precision (literally). It is by this mechanism that greenhouse theory exists. It's not a correlation argument, it mathematically calculates that visible photons have no trouble passing through the earth's atmosphere to warm the surface, but upon bouncing back upwards and losing energy (increasing wavelength), are prone to be deflected back at the earth by greenhouse gases. This re-warms the earth.
"Global warming is global, so it cannot be that Arctic ice measures warming but Antarctic ice does not." - CON
They both measure warming, but remember - it's global, so we cannot use Antarctic ice to ignore temperature observations from the Arctic, North America, Europe, Asia, the North Pacific, the North Atlantic, Africa, the South Pacific, South America, the South Atlantic, the Indian Ocean, Australia, and - yes - even the temperature readings of the Antarctic (as I pointed out in round 3, ice and temperature cannot have a linear relationship except at temperatures near freezing point - this is why 'absorption of energy' is more relevant than short term temperature).
"In the last round, Pro changed his position and argued that total ice is important and not sea ice" - CON
I argued that deuterium levels from the last ten thousand years were less relevant than energy readings from the last century. CON's narrative of my position is unrecognizable to me, so my most objective route at this point is to request of voters that they actually find the "PRO" arguments that correlate with the "CON" narrative before either agreeing or disagreeing with it - and vice versa.
"total ice has been decreasing since the early 1800s, well before any claim of anthropogenic warming." - CON
Deforestation has actually increased net CO2 emissions since before 1750 ,
but in negotiating this debate, CON chose "temperature anomalies from 1900 to 2200 are / will be predominantly anthropogenic" from a number of other possible Anthropogenic Climate Change Exists subtopics, so we'll have to save that discussion for another day. As I have explained at least three times in this debate, ice represents two out of seven continents to measure, and as CON has explained, this is a discussion about global temperature.
"Pro claimed that melting land ice in Antarctica caused the increase in sea ice." - CON
I discussed three measurements - temperature, volume, and area. These were ALL in regards to land ice in Antarctica.
PRO Round 3:
Both Arctic and Antarctic temperatures are supposed to be far below freezing, and neither will commence a serious level of shrinking until they reach the melting temperature of water. As the top of the ice caps melt, the water runs down and is cooled by the ice below, slightly reducing or maintaining the total mass of the ice while possibly increasing the total area. However, it also increases the average temperatures of the Antarctic and Arctic.
"Future CO2 levels are unknown" - CON
Solar, volcanic, botanic, and other alleged hidden variables in century-measured climate change would have to accelerate hundreds of times over in the next two centuries if anthropogenic CO2 is to become a 'secondary' driver of climate anomalies. This can even be deduced from CON's use of geological data, which covers up to 600 million years at a time.
Current physical predictions indicate that anthropogenic global warming will be steady and lingering for several centuries, and statistically comprehensive climate data corresponds to this theory.
There has been no global warming for 17 years, despite a 54% increase in CO2
Pro now argues there is something wrong with NASA's Remote Sensing Satellite (RSS) data  because it does not measure temperature with a thermometer. No scientist, to my knowledge, has ever questioned the ability of RSS to measure temperature. Satellite measurements are far superior to the spotty coverage of weather stations subject to urban heat island effects.
Satellites provide global coverage at much higher densities than attainable with in situ observations. In situ observations also suffer from non-uniform temporal coverage and undocumented changes in the instrumentation used that can lead to local biases and increased uncertainty. … Satellites can measure the temperature of the atmosphere by evaluating thermal emission from gases in the atmosphere. ... By choosing the different measurement frequencies, and thus different values of absorptivity, the emission from different layers of the atmosphere can be measured. RSS studies the measurements made by 3 series of satellite-borne microwave sounders in order to construct long-term, climate-quality atmospheric temperature datasets for use by the scientific community. [24. http://www.remss.com...]
If temperature continued to climb in the past 17 years, we would expect advocates of the theory of CO2 dominated climate to trumpet the success of climate models. But those advocates recognize the fact that the models have failed, the Voosen article I cited makes it clear that CO2 advocates are struggling for an explanation of why the models have failed.
I explained in detail why there is no inconsistency with having no temperature increase in 17 years and having the 2001-2010 decade averaging warmer than the 90s. Pro ignored my explanation and claimed that there is a conflict. Pro said I claimed that the temperature anomaly was reset for each decade. That's nonsense, I made no such claim, and if it were reset every decade then the temperature anomalies would be a string of zeros. The anomaly is an arbitrary offset to prevent graphs from having to be scaled with the average global temperature of around 59 degrees F or 287 degrees Kelvin. Pro's graph shows global warming to have stopped since 2000.
In additional to providing the actual data and the opinions of scientists who advocate CO2-dominated climate, I provided the work of Von Storch and separately of Mauritsen who showed that CO2 models could not explain the pause.  Pro claims I misrepresented Von Storch because in 2006 Von Storch said he believed CO2 dominates climate, but in 2012 Von Storch admitted the CO2 models failed. I quoted Von Storch as saying “we find that the continued stagnation in global warming, from 1998 to 2012, is inconsistent with model predictions, even at the 2% confidence level.”  That's not a misrepresentation. Scientists become convinced by unrelenting contrary data. The same is true of other CO2 advocates, quoted by Voosen , who finally have given up trying to defend the models.
I cited Tinsdale's book  for it's extensive comparisons showing the CO2 models fail. Pro argues that I needed to have shown and argued every piece of evidence in the book. No, all I needed to do was to make a claim and cite the evidence. To refute Tinsdale, Pro might have cited some contrary compendium showing all the models were on target, but there is no such evidence to be cited.
Some of the CO2 advocates claim the lack of global warming is due to something other than cosmic ray clouds seeding. Hansen supposes it might be reflective soot from coal burning in China. For the present debate, it suffices to say that CO2 is not dominating climate, and so until the science is resolved future predictions cannot be made reliability under the assumption that CO2 dominates. Cosmic ray effects, or something else associated with sunspots, are clearly the most likely factor because the sunspot trend since the early 1800s has been generally in favor of warming, but sunspots activity also tracks the Medieval Warm Period, the Little Ice Age, the global warming pause from the 40s through the 70s, the 70s sharp cooling, and the current 17 year lack of global warming. All this was shown clearly in the data presented in the debate.
Pro's graphs of temperature with and without CO2 are purely math model predictions. He says that they include sunspot and ocean oscillation effects, but they unquestionably do not. That's apparent because the real temperatures post 2000 did not rise as the graphs show, and also because the projections go out into the future. Voosen  specifically referenced these elements missing from the models. The “natural forcings” in the model projections are defective because they do not include the cosmic ray and magnetic effects of sunspots, rather only the inconsequential changes in irradiance.
Pro began by arguing that that we should not look at temperatures before 1900, because that's when anthropogenic global warming began. However, the physics of climate do not change, and temperature reconstructions on scales of millions of years, hundreds of thousands of years, and the past 2000 years show that CO2 has never dominated climate, no matter what the source of CO2. CO2 levels have been many times current levels. In the past, CO2 increase was a product of warming, not a cause. CO2 may increase warming slightly, but it's never prevented natural forcings from driving temperatures down. To show that CO2 now dominates climate, advocates must show that no other natural factors are significant, but current lack of warming shows that the models are dead wrong.
In this round Pro introduced the argument that CO2-induced warming began in the 1800s. But then what caused the preceding Medieval Warm Period and Little Age? It's far more likely that whatever caused those major climate changes ended, producing the subsequent warming. Those major climate events were tightly correlated with sunspot activity. To argue it was CO2, a switch must have been flipped around 1825 causing sunspots to no longer have an effect and CO2 to start dominating.
Polar sea ice has increased to a current high, contrary to CO2 theory
We are seeing the real world destroy the theory of CO2 dominating climate. The CO2 math models cannot be tuned to explain how a 54% increase in CO2 has failed to produce and increase in global temperatures. For a while, the notion was that the failure was some transient glitch that would quickly disappear. After 17 years, it's clear that there is a fundamental lack of understanding reflected in climate models. CO2 theorists have been fervent in clinging to their theory, but they are nonetheless still scientists and ultimately obliged to yield their theory to the contrary data. I'm sure that science will ultimately succeed in getting climate models that match reality, and that the models will include some effect of CO2. But it should not be a surprise that the sun dominates climate, even though we are still figuring out exactly how.
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