The following came up after my presentation, "What is global warming?" to 5th and 6th graders at the Stanley Clark School, South Bend, IN. Thanks to the students for being so attentive and for their great follow-up questions!
A bunch of students asked this question, and it's a great one--and scary too. I don't think that global warming will destroy the planet. If you look back 2.5 (or more) million years ago, for example, you can find an atmosphere and a climate that is similar to the one that we creating today. So the planet will go on and some plants and animals that can adjust to the climate change will go on too. But that's not to say that climate change is not a big deal--it really is. We are creating an atmosphere unlike the one that has dominated for 800,000 or more years! And the threat of climate change is not to the planet but to us. It will likely cause many of the plants and animals that we use and enjoy to decline or go extinct (maybe 10-30% of them!). If we have a large amount of climate change--the amount that we are likely to get if we don't stop releasing greenhouse gases in the next 10 or 20 years--if will be difficult to feed all of the world's people and millions of people will loose their homes to rising seas. The question about global warming is: do we want to make it difficult for people around the world to feed themselves, to be happy and to be healthy?
~15% of the greenhouse gases emitted that are causing global warming come from deforestation and forest degradation.
The ozone layer is a really helpful part of the upper atmosphere where ozone tends to concentrate, and it helps to filter ultraviolet radiation that is harmful to living organisms in large doses. Some chemicals made by people, called CFCs, made their way into the upper atmosphere and broke down the ozone layer, creating the ozone hole. The ozone hole lets more UV reach the surface of the earth. Because many governments around the world passed laws outlawing CFCs, the growth in the ozone hole has slowed down. The ozone hole is a different problem than global warming, but the fact that we could stop growth in the ozone hole gives us some hope that we could also solve the problem of global warming. If society could just decide to take action through laws or other mechanisms, we can slow and stop the emission of greenhouse gases.
Acid raid is caused by the release sulfur and nitrogen-based compounds from power plants and other things that burn fossil fuels. These compounds get in to the air and combine with water droplets to make the water acidic. So when those droplets fall from the air, they are "acid rain." The sources that make acid rain also release greenhouse gases, but these are different environmental problems. Learn more about acid raid at this EPA website: http://www.epa.gov/acidrain/what/index.html
If some--or better yet many!--of us were to stop releasing greenhouse gases, we would slow down climate change. The more that the world emits, the more and the faster the climate changes. Eventually stopping emissions is the ultimate goal to stop the process of global warming.
Of the big three greenhouse gases, nitrous oxide is the most potent. Each molecule has ~300 times the heat trapping capacity of one molecule of carbon dioxide. Each of the greenhouse gases, however, stays in the atmosphere a different length of time, so when thinking about the effect of each gas we have to think about how much we emit, how potent each molecule is, and how long it stays in the atmosphere. CO2 is the most important greenhouse gas because we emit so much of us and it stays in the atmosphere for a very long time.
In the early Eocene, about 50 million years ago, the Arctic was about 8 degrees C (or 14.5 degrees F) warmer than it is was before the humans started enhancing the greenhouse effect. At that time, northern parts of Canada had turtles, alligators, primates, and tapirs. Climate models tell us that if we keep on releasing more and more greenhouse gases to the atmosphere, like we have been doing the last 100 years, the Arctic could be that warm again by the end of this century.
Yes, if when we say "global warming" we mean the influence of people on the climate, we can stop that. All we need to do is stop adding carbon dioxide, nitrous oxide, methane, and other greenhouse gases to the atmosphere. To do that, we will need much greater energy efficiency than we have today--turn off those light bulbs when you don't need them and use energy-efficient appliances!--and we will need alternative energy sources that do not pollute the atmosphere, like solar and wind power.
If we could stop emitting more greenhouse gases to the atmosphere and take back the ones that we have already emitted, we could bring the earth back to the atmosphere that it would naturally have. It is going to be a lot easier to stop putting more greenhouse gases into the atmosphere, however, than it will be to remove the ones that we already put in. So we likely will have to live with some climate change from the gases that we have already emitted.
I'm afraid that this is one is hard to answer, and particularly hard for a scientist to answer. I think that people must have information about problems in order to want to do something about them, and I see that as my role--to help inform the public about an important problem. But there seem to be factors other than information that are holding politicians back. Some people are working hard to make sure that the government doesn't do anything because they benefit from the industries that release greenhouse gases. The way our political system works, it is also hard for politicians to make decisions that affect people today for the benefit of people in the future. Politicians are often more worried about getting reelected in 2 or 6 years than they are worried about what the climate will be like in 50 years. The only people who can get them to change their mind about that are citizens like you!
Global warming will cause the ocean to rise. First, the ocean will warm as it takes up some of the extra heat in the atmosphere and this will cause it to expand. Second, ice at the poles that is on land seems to be melting at a rapid rate under global warming, and this water will flow into the ocean. More water in the ocean means higher seas.
The largest amount of warming under global warming will take place at the poles and over land away from large bodies of water. The oceans will warm too, but we expect the average temperature over land to increase--at least within this century--more than the air over the ocean. You can see the patterns of warming on this map: http://www.ipcc.ch/publications_and_data/ar4/syr/en/figure-spm-6.html.
No, this is not true. We can stop global warming if we want to by stop releasing greenhouse gases to the atmosphere. If we keep releasing greenhouse gases, we continue to make global warming stronger and more severe. Some scientists are working on ways of taking out of the air some of the greenhouse gases that we already released. These technologies are probably a long way away, but they are important things to study.