Top 5 Issues at the Copenhagen Climate Conference

For the next two weeks, until December 18, officials from more than 190 countries will be gathering in Copenhagen to write a new treaty on climate change. For much of the year, there have been questions about whether the conference would come together and, if so, what it could accomplish at a time when much of the world is preoccupied with the global recession. In recent weeks, however, many of the world's economic powerhouses and biggest polluters, including the United States and China, have said they're serious about hashing out an agreement. Of course, with so many countries attending, "success" can mean different things to different people: Some want a political agreement; others want a legally binding treaty. Here are five things that could determine the outcome:

[See a slide show of the Top 5 Issues at Copenhagen.]

1. Developed Nations Vs. Developing Nations

Pretty much all the countries attending the talks agree that greenhouse gas emissions are contributing to climate change. But few want to slash their emissions without first ensuring that competing countries will do the same. Developing countries want the United States and other developed nations to cut emissions the most, since historically it's the industrialized world that's responsible for most of the carbon pollution in the atmosphere. But China, India, Brazil, and many others are growing rapidly, so the United States and other developed countries argue that the developing world must get a handle on its emissions, too.

2. Targets for Cutting Emissions

In Copenhagen, this tension will most likely play out in a numbers game. The scientific community says industrialized countries need to cut their emissions 25 percent to 40 percent by 2020 to avoid the worst of climate change. The European Union seems OK with that idea, but the United States has been resistant. President Obama recently announced that he'd call for cutting U.S. greenhouse emissions by about 17 percent. It has gotten a mixed response, with many nations saying the United States needs to be much more aggressive. Meanwhile, a few weeks ago, China announced that it will curb the "intensity" of its emissions (relative to GDP) by 40 percent to 45 percent by 2020. That was hailed as a sign that China is getting serious about climate change, but it has also left some questions. Watch for countries in Copenhagen to press China to be more specific about what its emissions goals mean.

[See photos from the Copenhagen climate conference.]

3. Assistance to Poor Countries

Many of the countries that will be hardest hit by climate change are poor. Some are island nations. Some are prone to drought. Others have big coastlines and are already seeing the impact of changing ocean chemistry and rising sea levels. To respond to climate change, they say, they'll need Western help. A lot of it. And that means money. But it's unclear right now just how much rich countries will be willing to give poor countries (especially when government treasuries aren't doing so well) in terms of cash and new technology. The World Bank estimates that poor countries will need up to $100 billion a year to respond to climate change. So far, Obama and Western countries have pledged $10 billion by 2012. Clearly, a lot of work remains to be done.

4. Carbon Trading

There's a general agreement—internationally, anyway—that the best way to tackle emissions is by putting a price on carbon. That means a future involving a busy, lucrative global carbon market, in which people buy and sell permits to emit carbon. These global markets, not surprisingly, are complicated, and there are a lot of tough issues to be worked out when it comes to making sure that markets are honest and transparent. No one wants a repeat of the current financial crisis. But many countries also don't want an international regulatory body telling them how to run their economy.

5. Pollution Offsets

One way for countries to cut emissions is to switch to cleaner forms of energy or to make their power plants more energy efficient. But there are other options. For example, a power company, rather than trimming its own emissions on site, might find it cheaper to pay a forest owner to plant a bunch of carbon-trapping trees. In other words, the power company is "offsetting" its pollution by paying someone else. As part of the Copenhagen talks, officials will be considering which types of offset programs work and can actually be enforced. (There's a big potential for fraud here.) Countries like Brazil and Indonesia, for example, are pushing hard for a forest program that would handsomely reward them for not cutting down their trees.

• Read 10 Things You Didn't Know About Copenhagen.
• See 10 Animals Threatened by Global Warming.
• See more coverage of the Copenhagen conference.