Mankind Is the Main Cause of Global Warming
Debate Rounds (4)
You asked to accept this.
I will be arguing that mankind is the main cause of global warming. We will not be debating whether global warming exists or not. It will be assumed that it does.
BoP is shared.
Mankind: "The human race; human beings collectively without reference to sex; humankind."
Main: "Chief in size, extent, or importance; principal; leading;"
Cause: "A person or thing that acts, happens, or exists in such a way that some specific thing happens as a result; the producer of an effect."
Global Warming: The rise in the average temperature of Earth's atmosphere and oceans since the late 19th century, and its projected continuation.
1. A forfeit or concession is not allowed.
2. No semantics or trolling.
3. All arguments must be visible inside this debate, and character limits must not be broken. Sources may be posted in an outside link.
4. Debate resolution, definitions, rules, and structure cannot be changed without asking in the comments before you post your round 1 argument. Debate resolution, definitions, rules, and structure cannot be changed in the middle of the debate.
Voters, in the case of the breaking of any of these rules by either debater, all seven points in voting should be given to the other person.
Round 1: Acceptance
Round 2: Presenting all arguments (no rebuttals by con)
Round 3: Refutation of opponent's arguments
Round 4: Defending your arguments and conclusions (no new arguments)
I would like to thank beforeifall for accepting this debate.
CO2's Effect on Temperature
First, correlation. The climate data over the last 700,000 years or so show that temperature and CO2 track very close to each other. "...there is a close correlation between Antarctic temperature and atmospheric concentrations of CO2. The extension of the Vostok CO2 record shows that the main trends of CO2 are similar for each glacial cycle. Major transitions from the lowest to the highest values are associated with glacial-interglacial transitions. During these transitions, the atmospheric concentrations of CO2 rises from 180 to 280-300 ppmv. The extension of the Vostok CO2 record shows the present-day levels of CO2 are unprecedented during the past 420 kyr."
This graph shows the CO2-temperature correlation over the last 650,000 years:
CO2 can be the dominant forcing for the climate. Consider the Cenozoic era (the last 65 million years). Overall, solar activity increased 0.4% over this period. "Because Earth absorbs about 240 W/m^2 of solar energy, that brightness increase is a forcing of about 1 W/m^2. This small linear increase of forcing, by itself, would have caused a modest global warming through the Cenozoic Era." The CO2 levels caused a much higher forcing. "In contrast, atmospheric CO2 during the Cenozoic changed from at least 1000 ppm in the early Cenozoic to as small as 170 ppm during recent ice ages. The resulting climate forcing, as can be computed accurately for this CO2 range... exceeds 10 W/m^2. It is clear that CO2 was the dominant climate forcing in the Cenozoic."
But then, there's also the matter of causation. CO2's effect on temperature can be explained by appealing to the carbon cycle. The Earth receives all of its energy from the sun. Some of this is reflected by the Earth's surface and by clouds and other particles present in the atmosphere. In addition, some of the built up energy in the Earth's surface can be emitted back into the atmosphere. Greenhouse gases like CO2, methane, and nitrous oxide trap some of this emitted heat by reflecting the radiation back to the surface. However, greater concentrations of greenhouse gases cause more of the energy that is being emitted from the surface to be reflected back to the surface. This causes more heat to build up, warming the planet.
Now consider climate sensitivity. Climate sensitivity is the amount the temperature would rise if the CO2 concentration were doubled. Obviously, if there's a large climate sensitivity, then increases in CO2 have large effect. It is known that the climate sensitivity is around 1 degree C. However, this can be amplified through feedbacks. Positive ones amplify the sensitivity, while negative ones diminish the sensitivity. The evidence overwhelmingly comes down on the former, that positive feedbacks are happening. Increases in CO2 cause temperature increases, which are amplified by water vapor and the effect on clouds.
"Since the radiative effects associated with the buildup of water vapor to near-saturation levels and the subsequent condensation into clouds are far stronger than the equilibrium level of radiative forcing by the non-condensing GHGs, this results in large local fluctuations in temperature about the global equilibrium value."
This can be shown in the below graph:
Now back to the carbon cycle. Global warming can result in the death of vegetation (due to droughts) and the warming of the ocean. Both of these further reduce the maximum absorption of the Earths carbon cycle, thus resulting in even more CO2 being released into the atmosphere. And with this, CO2 increases even more. In other words, CO2-caused temperature increases are amplified by positive feedbacks and the mechanics of the carbon cycle.
So, the positive feedback amplifies the climate sensitivity. How much it is amplified can be determined through study. Using a Bayesian statistical approach, which is “the dominant [method] in the literature”, these findings support the notion of climate sensitivity as maximum 4 degrees C, a mean of 3 degrees C, and likely not lower than 3 degrees.
The graph below gives a statistical analysis:
The mean is around 3 degrees C.
The CO2 that humans emit thus has an effect of 3 degrees C per doubling of CO2. This can be shown by the fact that CO2 concentrations have increased from around 275 ppm to around 400 ppm. This is an increase of around 40%. This should manifest itself with a temperature increase of a little less than 1.5 degrees C. Indeed, temperatures have increased around this amount over the last 150 years. The anthropogenic-forcing climate models thus match observations.
In other words, in addition to the direct evidence of how the Earth is warming, the climate models based on a greenhouse gas cause to global warming explain almost perfectly the recent global warming. This is a lot of evidence for a human case to the recent global warming.
Humans' Emission of CO2
It would be rather coincidental if the recent rise in global warming happened to start just around the time that humans started to emit large quantities of greenhouse gases. However, there is direct evidence as well, in addition to the already established correlation between temperature and CO2.
Now, it is known that CO2 levels are increasing. "In pre-industrial times over the last 10,000 years, CO2 was relatively stable at around 275 to 285 parts per million. Over the last 250 years, atmospheric CO2 levels have increased by about 100 parts per million." CO2 levels are increasing at a level not seen in at least 500,000 years, if not longer.
Here is a graph showing CO2 concentrations over the last 10000 years:
The evidence that this excess CO2 is the cause of the recent global warming is voluminous. One of the biggest indicators is the fact that less heat is escaping into space. Satellites measure less heat escaping out into space, particularly at the specific wavelengths that CO2 absorbs. In other words, the Earth is retaining a greater percentage of the heat that it receives from the sun than it did before. This excess heat manifests itself through global temperature increases. "If less heat is escaping to space, where is it going? Back to the Earth's surface. Surface measurements confirm this, observing more downward infrared radiation. A closer look at the downward radiation finds more heat returning at CO2 wavelengths, leading to the conclusion that '...this experimental data should effectively end the argument by skeptics that no experimental evidence exists for the connection between greenhouse gas increases in the atmosphere and global warming.'"
Another piece of evidence is a comparison of warming in the troposphere and stratosphere. Because the CO2 is in the upper troposphere, the troposphere temperature would increase, while the stratospheric temperature would decrease, because there would be less heat reaching the stratosphere. "Computer model estimates of the ‘human influence’ fingerprint are broadly similar to the observed pattern. In sharp contrast, model simulations of internal and total natural variability cannot produce the same sustained, large-scale warming of the troposphere and cooling of the stratosphere."
This graph shows this:
Related to this is the fact that the tropopause, the boundary between the troposphere and stratosphere, is rising. This is because the temperature gradient between the top of the troposphere and the bottom of the stratosphere is greater, as just described above. This causes the warmer air from the troposphere to rise, pushing the troposphere up. "Observations indicate that the height of the tropopause - the boundary between the stratosphere and troposphere - has increased by several hundred meters since 1979."
Another related piece of evidence to this is the cooling of the ionosphere. The ionosphere is the layer of the Earth's atmosphere where ionization takes place. It comprises the upper mesosphere, thermosphere, and lower exosphere. More precisely, it extends from 60 km to 1000 km above the surface. Studies indicate, "...moderate negative trends of about 2 to 3 K per decade at heights of 50 to 70 km... slightly larger cooling trends at heights of 70 to 80 km in the low and middle latitudes... essentially zero temperature trends between 80 and 100 km... at heights near 350 km, a negative trend of about –17 K per decade."
Yet another piece of evidence is the frequency of cold days and nights. Because the sun only shines in the day time, if the sun was causing global warming, the days would warm faster than the nights, while if greenhouse gases were causing global warming, this wouldn't be observed. It is the latter's prediction that is observed. "What we observe is a decrease in cold nights greater than the decrease in cold days, and an increase in warm nights greater than the increase in warm days."
This can be shown in the below graph:
Overall, the evidence shows that human-emitted greenhouse gases are the main cause of global warming. CO2, in addition to other greenhouse gases like methane and nitrous oxide are being emitted by humans in very large amounts, and this is manifesting itself in an increase in the average global temperature.
Greenhouse gases cause global warming because of their heat trapping abilities. Humans have been emitting vast amounts of greenhouse gases over the last 150 years, and this shows itself on the CO2 measurements. The atmospheric warming pattern and greater heating at night are evidence that the recent global warming is caused by those human emitted greenhouse gases. These increases are amplified through the water vapor and cloud positive feedbacks and the positive feedback that arises through the climate cycle. The climate sensitivity ends up being around 3 degrees C. Finally, the CO2-temperature record shows that the two correlate with remarkable correlation.
Sources in comments.
Numerous alternate causes to global warming prove that humans are not the primary source. Adopt a mindset of innocent until proven guilty, the affirmative must prove beyond correlation and doubt that human cause warming. The Pro must win that mankind is the "principal [and] leading" meaning that if I win that there is an alternative cause that is more responsible for warming than humans, or at least humans are not a major cause, then I win the debate. (First Pro speech)
As the Con, I may contradict myself as my sole purpose is to disprove the Pro's statement. The Pro must remain consistent to prove their position.
First, 1,500 year climate cycles. Fred Singer, an atmospheric and space physicist with a PhD from Princeton who founded the the Science and Environmental Policy Project (SEPP) and Nongovernmental International Panel on Climate Change (NIPCC), and Dennis Avery, a agricultural analyst who was awarded the National Intelligence Medal of Achievement, agree that there is substantial evidence around the world that climate cycles easily explain the warming we currently see. There is already a scientific consensus that cooling cycles (Ice Ages) exist, so it already not unreasonable to assume that warming cycles also exist. From 1300 to 1850, the Little Ice Age caused the earth to be about 2.5 degrees Celsius cooler than average. The Modern Warming portion of the cycle began in 1850, and "warming will continue for some time in the future, perhaps 200 years or more, regardless of human activity." Thus, today's warming can be explained by these climate cycles. These scientists gathered data from North America to Asia, and they use the ice caps in Greenland to further prove that by the way the ice formed, there must have been 1,500 year warming cycles. Sea sediment core in Ireland also shows the 1,500 year cycle. Fossilized pollen, boreholes, tree rings, and mountain tree lines all provide evidence to this theory because scientists can find how they were created or observe differing distances of tree rings to find the amount of warming that these objects underwent while being created. It's important to realize that completely dismissing 1,500 year cycles dismisses "human histories from the past 2,000 years...and a variety of physical evidence found by a huge body of serious researchers." (1) The Vostok ice sample that the rise and fall of CO2 correlate with natural cycles. Temperatures correlate with Ice Age minimus and maximus. There is a 420,000 thousand year cycle of carbon emissions. Given that humans release very little of the total carbon ouput, the correlation is between the carbon cycle and temperature cycle. (5)
Secondly, human emissions of carbon dioxide are specifically not to blame. Patrick Moore, a former member of Greenpeace and an ecologist said the following while testifying in front of Congress: "There is no scientific proof that human emissions of carbon dioxide (CO2) are the dominant cause of the minor warming of the Earth's atmosphere over the past 100 years." In fact, carbon dioxide levels were 10x higher during the Ice Ages than they are now. This was also true 500 million years ago before evolution had created humans. Not only does this empiric disprove that humans are a major cause of increased carbon dioxide, but it also disproves that CO2 causing warming. Regardless of the theoretical examples the Pro provides, empirics trump.
Third, the industrial revolution began in 1750, yet only from 1910 to 1940, there was an increase in .5 degrees Celsius of the global temperature. There was more than enough time for factories to produce enough carbon dioxide to have resulted in warming before those 200 years. This delay in increase prove that humans are not the main cause and is evidence of the climate cycles. (2)
During this time, temperatures were much higher than today, but CO2 levels were lower. This places doubt in the significance of anthropogenic CO2 release. (7)
Fourth, the climate rapidly changes to different stimuli. Anthony Lupo, assistant professor of atmospheric science at the University of Missouri at Columbia and an expert reviewer for the UN's Intergovernmental Panel on Climate Chang, discusses the fact that regional climates tend to experience much more change than globally. However, climates change rapidly, so if human emissions of CO2 really are responsible for warming, then 1) there should already be a much larger change in global temperature given the huge increase of CO2 emissions and 2) even when there were smaller amounts of CO2, this should have been enough to trigger an environmental change (3).
Fifth, climate models fail. There was an increase in global temperature of 0.57C during the 30-year period from 1970 to 2000. Since then there has been no increase, perhaps a slight decrease, in average global temperature. This clearly disproves the numerous computer models that the Pro cites as CO2 had increased after 2000 (2). Many believe that there will be an increase of anywhere from 2-11 degrees Fahrenheit due to info from computer models. Misinterpretation of results and models lacking the complexities of the fundamental global processes mean that these cannot be trusted. Consistently, politicians like Al Gore have predicted that the world would have literally ended by now. Prefer direct facts and empirical examples rather than theoretical results of greenhouse gases. Thus, do not automatically trust that greenhouse gases cause warming without direct evidence from changes in temperature â€" the facts don't support this conclusion. (3) Though the Earth is warming, it's cooler than expected. There should have already been a two degree Celsius increase 100,000 years ago. (5) [Insert pie graph from this source]
Sixth, fossil fuels do not cause an increase in CO2 levels according to the most accurate NASA data. From 1940 to 1950, CO2 levels flatlined. The only change was roughly .8 ppm downwards. World War II caused a massive increase in fossil fuel levels, yet this did not change CO2 levels. Prefer empirics. (4) Also, the Vostok ice core sample proves. CO2 increases did not increase temperature for 800 years. This sample also explains why a fall in temperature and a fall in CO2 correlate — cold water can hold more CO2 than warm water. Even more, temperature falls around 800-1,000 years before CO2 levels rise or fall giving water time to absorb the CO2. (5)
Seventh, even if humans do increase CO2 levels, they're only responsible for a 3% increase. Even that released CO2 is not all directly released into the atmosphere given that the oceans absorb so much of it. Limestone, chalk, and other rocks have 100x as much CO2 as the atmosphere. This 3% is responsible for .27% of the greenhouse effect. "If we were to cease all transport and industry right now, it is very unrealistic to assume that it would have any impact on global warming." (5)
Eighth, solar radiation is the single largest cause of warming. NASA repeatedly releases articles explaining the importance of the sun and sun cycles on the Earth. The near infrared and visible light waves are absorbed by the lower atmosphere, the oceans, and the land. Thus, these areas heat resulting in a higher global average temperature. Even more, absorption of UV rays heats the stratosphere. There's a general scientific consensus that this increases temperatures in the troposphere. Additionally, sun spots serve to reduce or increase warming. These can sway warming either way considering that these are 11 year cycles. This can explain why times of higher CO2 did not increase temperature. Scientists believe that the sun is responsible for at least half of all the climate change seen in the past 110 years. Even the IPCC, an organization devoted to creating response to globa warming, agrees. (6)
The 100,000 year cycle of radiation resulting from the elliptical orbit of the Earth is at a peak and will be for the next several thousand years. This radiation is consistent with spikes in CO2 methane. The melting of ice caps has happened with each of these cycles. The huge volume of these gases is too high to be anthropogenic but is consistent with previous cycles. Mars is also increasing in temperature due to the recent increase in solar radiation. Dr. H. Abdussamatov, head of the St. Petersburg Pulkova Astronomical Observatory, believes that the Earth has hit a temperature ceiling and will enter a cooling period despite fossil fuel use. This explanation accounts for the lack of increased greenhouse gas emissions since 1988. (7) [Insert Figure III]
Solar radiation, solar cycles, and multiple terrestrial temperature cycles are greater and more probable causes of warming. Humans produce very little emissions given the oceans' absorption and solar radiation cycles. The Earth has consistently changed temperatures before humans populated the planet. Even more, multiple empirics and evidence from around the world disprove the importance of humans on warming. 3% is a ridiculously small number when compared to multiple other emittors. CO2 levels were higher in the Ice Age when the Earth was substantially cooler. By placing some amount of doubt in the significance of mankind's importance on warming while promoting several other causes, humans are at least not the main factor of warming.
**I'm going to advertise my surveillance debate here: comment on that page if interested! :)
I would like to thank beforeifall for presenting his argument.
The 1500-year cycles are not global. Most of the data that scientists have found on this has come from the northern hemisphere. However, in the southern hemisphere, the exact opposite trend happens. In other words, whenever the northern hemisphere is warming, the southern hemisphere is cooling, and vice versa. "Whereas Antarctic and Greenland climate records do exhibit approximate anti-phase behavior around 50% of the time, they are generally in phase during cooling. A phase lead of Southern Hemisphere climate of 1000-1600 years is statistically indistinguishable from a lag of 400-800 years, whether for Dansgaard-Oeschger [1500-year cycles], Heinrich, or longer-duration events. The "seesaw" or "Southern lead" appearance of the data arises from the fundamentally different characeristics of the climate series, most importantly the absence of rapid warming events in Antarctica comparable to those in Greenland".
However, in the current case, we see that both the northern and southern hemispheres are warming, meaning that it cannot be due to the 1500-year cycles.
Human Emissions of Carbon Dioxide
The claim that CO2 levels were higher during certain ice ages is based off of old, faulty data. A recent study found that the levels during the Ordovician era (the era most climate skeptics focus on when making arguments like this) were eight times below pre-Industrial levels. This is indeed still a little high, but it's also important bearing in mind that the sun was dimmer then. During the Ordovician era, the sun was 4% dimmer. This meant that higher CO2 levels would have been necessary for Earth to have not been frozen over. This is based on established nuclear models of main sequence stars. Considering all of this, "...over the long term, there is indeed a correlation between CO2 and paleotemperature".
Apparent Mismatch Between CO2 and Temperature Increases
It is true that the vast majority of the warming happened over the 20th century. However, it is also true that the vast majority of the CO2 emitted into the atmosphere was emitted over the 20th century. See the graph below:
It is easy to see that only a small fraction of the emitted CO2 was emitted before 1900, and this correlates with the fact that only a small fraction of the temperature increases occurred before 1900.
Amount of CO2 Emissions
Any CO2 emitted into the atmosphere would have an adverse effect on the climate. As I said in the last round, there was a study that said, using a Bayesian statistical approach, the climate sensitivity as maximum 4 degrees C, a mean of 3 degrees C, and likely value of not lower than 3 degrees. This means that the CO2 that humans emit thus has an effect of 3 degrees C per doubling of CO2. This can be shown by the fact that CO2 concentrations have increased from around 275 ppm to around 400 ppm. This is an increase of around 40%. This should manifest itself with a temperature increase of a little less than 1.5 degrees C. This is indeed around the amount of global warming we have seen so far. It should not be more than this.
If less CO2 had been added into the atmosphere, then the planet would have warmed less, but it still would have warmed. This would be true for any non-zero amount of CO2 emission.
This point is irrelevant. The climate is much more complicated than just a correlation between CO2 and temperature (even though it still exists). Climate models have to be extraordinarily complicated, and even so, they might leave out very important climate forcings. Even if they didn't, there might still be glitches in the models that would make the model give an invalid result. The ability for climate models to accurately predict the climate is completely independent of the whether or not CO2 levels are related to temperature levels
It is worth falsifying the notion, however, that there has been no warming since 2000. This idea is based on satellite measurements of atmospheric temperature. However, there are two problems with this. One, while the atmosphere accounts for only less than 3% of increased heat content, the oceans account for the vast majority, and they show no such trend. The graph below shows this:
And two, there have been a lot of negative short term forcings over the last 20 years. Removing the short term trends of the extremely powerful El Nino in 1998, volcanic activity, and solar activity, the atmospheric temperature plot looks more smooth:
(You can faintly see what the plot looked like before the negative forcings were removed; the variability after 1998 makes any analysis before a statistical reanalysis suspect).
Correlation Between CO2 Emissions and CO2 Levels
Many studies have shown that the "airborne fraction", or the fraction of human CO2 emissions that stay in the atmopshere, is around 43%. The fact that the CO2 levels flatlined during WWII is actually rather complicated. While military activity spiked, other industrial activity plummeted and millions of people died, decreasing the need for non-military CO2 emission even lower. In addition, CO2 levels are not known with the precision necessary to unravel this mystery before 1960, due to improper measuring techniques. There are simply too many factors too consider to make a sound conclusion here.
As for the apparent 800-year lag in CO2 levels after temperature increases, this is indeed true. However, this is because there was no non-natural (i.e. human) forcing of CO2. Instead, another forcing initiates the warming trend, and CO2 amplifies it. "When the Earth comes out of an ice age, the warming is not initiated by CO2 but by changes in the Earth's orbit. The warming causes the oceans to release CO2. The CO2 amplifies the warming and mixes through the atmosphere, spreading warming throughout the planet. So CO2 causes warming and rising temperature causes CO2 rise. Overall, about 90% of the global warming occurs after the CO2 increase."
Human Versus Natural CO2 Emission
Natural CO2 emissions are typically stable, meaning that there is rarely any long term climate change that results from natural emissions of CO2. However, humans have emitted a lot of CO2, above and beyond what is naturally emitted, and this unbalances the climate stability. "Although our output of 29 gigatons of CO2 is tiny compared to the 750 gigatons moving through the carbon cycle each year, it adds up because the land and ocean cannot absorb all of the extra CO2. About 40% of this additional CO2 is absorbed. The rest remains in the atmosphere."
The most important of the natural climate forcings is indeed the sun. It is the source of the Earth's energy. This energy comes from the radiation emitted as a result of fusion reactions at the core of the sun. This radiation is known as the Total Solar Irradiance (TSI). Any change in the TSI causes energy imbalances on the Earth. This energy imbalance can be calculated using the formula below:
Delta means change, so Delta(F) means the change in energy (i.e. energy imbalance) and Delta(TSI) means the change in solar irradiance. The 0.7 factor comes from the fact that the Earth reflects about 30% of the solar radiation it receives, and the 1/4 factor comes from spherical geometry.
Changes in temperature are proportional to the energy imbalance. This can be expressed in the formula below:
Lambda is the constant of proportionality, representing the climate sensitivity (discussed in my first argument) in this case.
The only thing that's left is to actually determine the values. First, the change in TSI (in this case, between 1900 and 1950). "...we'll estimate the change in TSI at 0.5 to 2 W-m-2." This corresponds to an energy imbalance of around 0.1-0.35 W-m-2. Next, the lambda factor. I explained in the last article that the statistically most probable value for the climate sensitivity was around 3 degrees C. But, there was a lot of variation. "Studies have given a possible range of values of 2 to 4.5°C warming for a doubling of CO2, which corresponds to a range of 0.54 to 1.2°C/(W-m-2) for λ." This gives range of values from 0.05 to 0.4 degrees C, with a most probable value of 0.15 degrees C (corresponding to the statistically most likely climate sensitivity). In other words, solar activity from 1900 to 1950 raised the temperature of the Earth 0.15 degrees C. Looking at the effect of CO2 emissions over that same period, humans increased the concentration of CO2 in the atmosphere by about 20 parts per million, giving a range of values of 0.14-0.32 degrees C for the effect of that emission on the climate, with the most probable being 0.22 degrees C.
This corresponds to CO2 amounting for 60% of the warming from 1900-1950. After that, it gets higher. CO2 emissions rise exponentally, and changes in the TSI start getting less positive, and eventually become negative after 1975. "Over the past century, this increase in TSI is responsible for about 15-20% of global warming. But since TSI hasn't increased in at least the past 32 years (and more like 60 years, based on reconstructions), the Sun is not directly responsible for the warming over that period." Solar activity cannot account for the warming after 1975, and even before that was a smaller factor than CO2.
This can be shown in the image below:
Therefore, we see CO2 correlates with recent temperature increases better than solar activity, especially after 1975.
Long Term Forcings and Mars
The cycle of radiation is so long that it would not be having the sudden, enormous effect we've seen over the last 150 years. As for Mars, the studies concluded that it was a change in the surface dust, not solar activity, that caused the warming. Surface dust has a massive effect on Mars's climate. The supposed warming trend went from before the surface dust change to after it. Therefore, Mars did not warm because of solar activity.
Sources in comments.
beforeifall forfeited this round.
It seems to be difficult to get someone to debate me on this topic. Hopefully my opponent will at least respond to my original arguments.
beforeifall forfeited this round.
1 votes has been placed for this debate.
Vote Placed by Udel 10 months ago
|Who won the debate:||-|
Reasons for voting decision: Pro shows correlation between Co2 and temp. His graphs show how Co2 impacts things and he explains global warming killing vegetation. The pics show how humans specifically lead to emissions of Co2 which impacts greenhouse gases. He explains Greenhouse gases cause global warming because of their heat trapping abilities. Humans have been emitting GG over the last 150 years, and this shows in the Co2 measurements. Con says the temp change is due to climate cycles, and no proof of human carbon emissions being problematic. Basically he argues humans produce very little emissions given the oceans' absorption and solar radiation cycles. Pro challenges Con's data in the next round. He explains what has been observed in the northern part of the globe isn't true for the south. Pro negated Con's point about the temp mostly being from the sun. And then Con forfeited. Maybe if Con responded and discredited Pro's rebuttal and model he would have won, but Pro's arguments had to stand.
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