Humans cause climate changing
At first, burning fossil fuels, such as coal, oil and natural gas, to generate energy has the greatest impact on the atmosphere. How much harmful things are on the atmosphere because of factories, vehicles and burning trash. All these things gather and hinder rain, snow and even sun. It changes climate. (1)
Second, deforestation is one of the biggest harm that people do to the nature. Forests help protect the planet by absorbing massive amounts of carbon dioxide (CO2), the most abundant type of pollution that causes climate change. However, people cut trees, too. So, it causes climate changing. What do human beings think about? (2)
Those are main problems that are lead to climate changing and that are caused by people. To conclude, it means humans influence climate changing.
There is no doubt the temperature of the earth is rising. The temperature figures prove this. However, what is more open to discussion, is whether the changing climate is due to human influence or if it some natural phenomenon. My opponent has based her case around the emissions of CO2 into the atmosphere. Again, while atmospheric CO2 levels are high, it is not a certainty that this is caused by humans.
In fact, the globe has, at periods in it's past, been hotter than it is now. In the Mesozoic era. better know as the reign of the dinosaurs, the climate was much hotter and dryer than it is now and there was certainly no industry back then to emit greenhouse gases. There was also little or no ice at the poles for extended periods of time. My point is, if there is proof that it happened once, then why can't the climate rise without human interference yet again. (http://www.enchantedlearning.com...)
My next point is in regards to my opponents link between deforestation and climate change. While it is a problem that deforestation has such a negative impact on the ecosystem and is threatening the lives of many species, it is not a climate change issue. Tree's are not actually the best organisms for removing C02 from the air. This title belongs to algae. A colony of algae has the ability to photosynthesise more carbon dioxide in a year than a tree will in it's entire life. Add to this the fact that algae can reproduce rapidly, take up less space, and are now being farmed for their sustainable properties and biomass promises and the loss of a few CO2 reducing trees does not have such a devastating affect on the atmosphere. (http://www.ecogreenglobe.com...) (http://allaboutalgae.com...)
Also, humans are not the only things emitting greenhouse gases. Methane a gas that has stronger greenhouse affect than CO2 has been rising off wetlands for ages. While humans do contribute to methane in the atmosphere, wetlands have long been responsible for methane emmisions due to methane producing bacteria. Termites, Hydrates, Wild Fires and Animals also all produce methane. My point here is that, while humans are producing chemicals like methane and CO2, so to is the environment, meaning that humans are not he only source and hence not the ultimate cause of the greenhouse affect. (http://www.epa.gov...)
24hrs is rather short time to research and formulate arguments to I'll leave it at that for now and await my opponents response.
Second, it is true that "humans are not the only things emitting greenhouse gases", while humans cause the biggest amount of gases. As the Intergovernmental Panel on Climate Change, a group of 1,300 independent scientific experts from countries all over the world claimed: "The industrial activities that our modern civilization depends upon have raised atmospheric carbon dioxide levels from 280 parts per million to 379 parts per million in the last 150 years. The panel also concluded there's a better than 90 percent probability that human-produced greenhouse gases such as carbon dioxide, methane and nitrous oxide have caused much of the observed increase in Earth's temperatures over the past 50 years." It proves that humans cause climate changing and they influences to it quickly than it can be naturally. To conclude, humans are the main creature that caused a big problems in climate changing and damage it during a short period of time.
In response to my contention that the planet does not need humans in order for the climate to change, my opponent has simply stated that, it was 248 Million years ago, implying, I assume, that this is not relevant to today's climate. The problem with this statement is twofold. First of all, the Mesozoic Era ended in the late Cretaceous, which was 65 Million years ago as opposed to 248. That's considerably closer to modern time. Also, in the period closer to us, there was no Ice at The poles. 
The second issue I have with this rebuttal is that the Mesozoic era is not the only example of pre-industrial age climate change. In fact, duing the last 2 billion years the earths climate has been fluctuating between a "hot house" and an "Ice House", clearly illustrated in the chart below:
Next we move on to my opponents next point, about humans actually having deliberately influenced the weather. While at first it may seem like this is an insurmountable argument for man-made climate change, it is actually rather irrelevant. You see, what my opponent has failed to take into account is the difference between climate and weather.
Climate is defined as: the composite or generally prevailing weather conditions of a region, as temperature, air pressure, humidity, precipitation, sunshine, cloudiness, and winds, throughout the year, averaged over a series of years. 
So humans deciding that they do not want it to rain tomorrow is not an example of climate change, it is an example of weather change. Even a nuclear explosion, which will change the weather for perhaps a few months, is still not climate change, as it has not had a sustained, long term affect on the climate.
The very article that Pro provides to substantiate his claim that CO2 emissions by humans are the leading cause of climate chanche clearly lists water vapour as the most common greenhouse gas found in the atmosphere. And how does water vapour get into the atmosphere? By evaporation powered by the sun, not by humans.
And while I will conceded that humans are the No.1 producer of CO2 in the world, as I said in my previous argument, methane, a common natural gas, is actually more effective at trapping head than Carbon Dioxide. A single volcano, such as Mount Eyjafjoell in Iceland, can produce around 300,000 tonnes of CO2 per day. This places the one volcano alone above countries such as Austria, Portugal and Ireland in terms of emmisions.
In conclusion I have clearly demonstrated how the earths climate can easily change, and has been changing, without any help from man, how many made weather is not climate change and how human CO2 emission is not such a big problem as we think it is. The resolution is negated.
Second, no matter whether it was 248 million years ago or 65 million years ago, the fact is that it was million years ago and climate changed during these long period of time. My opponent wrote "during the last 2 BILLION YEARS the climate in the Earth has been fluctuating between..." It shows that climate was changing not in short time such as 2000 years, it was changing during 2 BILLION YEARS, which is very long period. The fact is without humans affect, climate changes slowly, during billions of years. However, humans' affect changes the climate quickly. Look to the cite http://www.ncdc.noaa.gov... especially to the subtopic "Climate Model Indications and the Observed Climate". There is a chart where it is appeared how climate changes with and without humans affect. It proves that with humans affect climate changes quickly.
There are more evidences of quickly climate changing:
1. Global sea level rose about 17 centimeters (6.7 inches) in the last CENTURY. The rate in the last decade, however, is nearly double that of the last century. It is changing during 100 years not billions of years.
2. All three major global surface temperature reconstructions show that Earth has warmed since 1880. Most of this warming has occurred since the 1970s, with the 20 warmest years having occurred since 1981 and with all 10 of the warmest years occurring in the past 12 years. Even though the 2000s witnessed a solar output decline resulting in an unusually deep solar minimum in 2007-2009, surface temperatures continue to increase.
3. The oceans have absorbed much of this increased heat, with the top 700 meters (about 2,300 feet) of ocean showing warming of 0.302 degrees Fahrenheit since 1969.
4. The Greenland and Antarctic ice sheets have decreased in mass. Data from NASA's Gravity Recovery and Climate Experiment show Greenland lost 150 to 250 cubic kilometers (36 to 60 cubic miles) of ice per year between 2002 and 2006, while Antarctica lost about 152 cubic kilometers (36 cubic miles) of ice between 2002 and 2005.
5. Both the extent and thickness of Arctic sea ice has declined rapidly over the last several decades.
6. The number of record high temperature events in the United States has been increasing, while the number of record low temperature events has been decreasing, since 1950. The U.S. Has also witnessed increasing numbers of intense rainfall events.
7. Since the beginning of the Industrial Revolution, the acidity of surface ocean waters has increased by about 30 percent. This increase is the result of humans emitting more carbon dioxide into the atmosphere and hence more being absorbed into the oceans. The amount of carbon dioxide absorbed by the upper layer of the oceans is increasing by about 2 billion tons per year.
All these facts proves that during last century climate was changing a lot. The last century is about 100 years and it is really quickly. Before humans' industry climate was changing slowly during millions or even billions of year. That means people's affect is really big and dangerous. What will happen in the next centuries if such situation will continue?
Next, my opponent wrote that climate and weather are different, also he gave the definition of the climate. "Climate is defined as: the composite or generally prevailing weather conditions of a region, as temperature, air pressure, humidity, precipitation, sunshine, cloudiness, and winds, throughout the year, averaged over a series of years".
It means that WEATHER conditions in the certain period of time IS CLIMATE. It proves that humans' affect to the weather can change the climate, as weather influences to the climate and they are not so different. That means my argument in the second round about how people change the weather is RELEVANT to the topic. I wrote that China attacked to the bank of cloud to transform clear blue sky for the National Day parade, that has caused the big storm in the next days. It is not happened once, there are several other examples of it in America, too. I would like to say that all these transformations of the weather influenced to climate changing. Once weather was changed it affects to the weather in the next periods of time.
The last Con's argument is that there are other things such as volcano, which produce CO2 more than humans. So, as he claimed a big amount of CO2 is not humans' fault. My response is that in the nature everything was balanced before industry. The certain amount of the CO2, which produces by volcanoes or other things, was removed by trees and by algae. However, since the industry appeared, a lot of factories, manufactures and a lot of vehicles were invented and amount of CO2 increases. Moreover, trees and algae that removes the CO2 were destroyed, burned and cut by humans. That means human increases the amount of CO2 and decrease the trees that removes CO2, so humans damaged the natural balance, as a result an amount of CO2 increased and it influences to climate's changing. Look to the cite http://climate.nasa.gov... There is a chart, which proves that for 650,000 years, atmospheric CO2 has never been above the certain line until 1950 year. It shows that amount of CO2 was once small, then was big, but the fact is that it was in balance in the certain amount, while since humans start to use factories and vehicles, CO2's amount increased a lot. That proves that humans affect to climate changing.
In conclusion, I have clearly proved that attack to transform the weather can influence to the climate changing; that increasing of the amount of the CO2 during last years is a big problem that is caused by humans. Also, that the climate changing affected by humans is quicklier than the natural climate changing can be. So, humans are the main creature that influences to the climate and changes it. So, I am writing to everyone, think a bit about climate changing and its consequences. What will happen in the future if CO2 increase, sea level and global temperature rise, ocean acidification continues? Humans affects to these problems and, I believe, humans can stop them. Think about your future and the future of the next generation and stop damaging to the nature and to the climate. Thank you for attention.)) Also, thank you, my opponent. I had excellent experiences by debating with you. It was really interesting.
As this is the last round I will keep it exclusively for rebuttals:
"My opponent wrote "during the last 2 BILLION YEARS the climate in the Earth has been fluctuating between..." It shows that climate was changing not in short time such as 2000 years, it was changing during 2 BILLION YEARS, which is very long period."
The reason I said 2 Billion years was not because, over two billion years the climate has slowly gone from hot to cold, it was to demonstrate that the climate on earth is always changing. Over the past two billion years it has gone from cold to hot to cold to hot to cold to hot over and over again and as the chart I supplied last round demonstrates, it has been cooling for longer than it usually doe, Now it is warming up again and, being the self-centered, egotistic creatures that we are, we think that just because wea re around it has something to do with us.
"It means that WEATHER conditions in the certain period of time IS CLIMATE. It proves that humans' affect to the weather can change the climate, as weather influences to the climate and they are not so different. That means my argument in the second round about how people change the weather is RELEVANT to the topic."
What pro fails to realise is that the last part of the definition states: averaged over a series of years. So no, no matter how you put it, weather is not climate, weather is the day to day changes, whereas climate is the behaviour of the weather averaged over a series of years. If humans were to influence the weather over a long period of time that would be climate change. Changing one day of weather does not change the climate and hence is still not relevant to the debate.
Also, while I can not dispute the facts that my opponent has supplied in the last round (for they are facts, I checked) I can attack they're relevance. For instance, constant reference to polar ice melting is made. I have already demonstrated how this is natural. For much of earths history there has been no ice at the poles what so ever, so to have such a substantial amount now is a rarity that will not last. He makes reference to the amount of CO2 in the water increasing. Again, I find this rather irrelevant, if the topic of the debate was 'Humans cause changes to ocean composition" it would. Basically, more CO2 in the ocean is not an example weather or climate.
Pro also makes a lot of references to time frames, "Since 1950" or "for the last 100 years."
The fact is that the temperature could have been slowly rising for the last 1000 years and we wouldn't know it. While human have always been able to feel the temperature, they have only recently started to record it. There were no monks that wrote what the weather was like everyday of the tear for their entire lives 1000 years ago. Basically, in order to say the climate has changed we need to be able to compare recent climate to past climates and since we do not have data on the climate every year for the past 1000 or so years, only a rough average like the rest of earths unrecorded history, we can not say, with any certainty, that the changes in the last 50-100 years have been special.
Finally thank you to my opponent for an interesting and challenging debate! Let's hand it over to the voters...