BRUSSELS, Belgium — The international conference designed to save the world from the potentially catastrophic effects of global warming finally became reality on Monday.
Over the next two weeks, the talks are scheduled to grow in intensity until world leaders — now set to include U.S. President Barack Obama — gather in the Danish capital to finalize a global deal to cut greenhouse gas emissions.
The issues are complex and controversial. Here’s a look at some of them.
The vast majority of scientists believe that carbon dioxide and other “greenhouse” gases pumped out of cars, planes, factories, power plants and homes concentrate in the atmosphere, accentuating the natural warming affect of the sun and causing the Earth to heat up.
If we continue to pump out greenhouse gases unabated, temperatures are likely to increase by an average of up to 6.4 degrees Celsius by the end of the century, according to the panel of scientists set up by the United Nations to investigate the problem.
The results could be catastrophic, with melting icecaps, rising sea levels, widespread flooding of lowland areas, devastating droughts, storms, fires and spreading tropical diseases.
Vocal climate change deniers ranging from American conservatives, Australian liberals, Saudi oil traders and a scattering of maverick scientists and politicians claim either that global warming does not exist or is not caused by human activity.
The Copenhagen summit, which is supposed to gather 15,000 delegates and the leaders of more than 100 nations, is the latest in a string of world climate change conferences since governments started taking the scientists’ warnings seriously in the early 1990s.
The most important of those gatherings was Kyoto in 1997, which set binding greenhouse gas reduction targets for 37 industrialized nations running up to 2012. The United States — then the world’s biggest greenhouse gas emitter — refused to ratify the Kyoto Protocol, arguing it was too harmful to the economy since developing nations such as China were not included.
Copenhagen is due to replace Kyoto with new commitments to slash harmful emissions post-2012. This time China, India and other developing nations will be included.
The climate change talks are a tangled mass of numbers and calculations.
One key figure is the target of limiting the global temperature rise to 2 degrees Celsius above pre-industrial levels. To do that, the U.N. scientists say increases in greenhouse gases emissions need to be halted by 2020 at the latest and reduced by at least 50 percent of 2000 levels by 2050.
The European Union says that means developed countries should cut their emissions by at least 80 percent by 2050. Pledges have been coming in during the run-up to Copenhagen.
The EU has committed to cut emissions by at least 20 percent by 2020. Obama says the U.S. will reduce its emissions by 17 percent by the same date. Japan as made an offer of up to 25 percent.
With its economy still developing, China — the world's biggest polluter — hasn’t set an overall reduction target but says it will cut its “carbon intensity” by more than 40 percent by 2020 — that is the amount of CO2 emitted per unit of economic growth. India has offered to reduce its carbon intensity by 24 percent.
Amid the often tortuous jargon of climate change, three buzz words dominate at Copenhagen: mitigation, adaptation and finance.
Mitigation means reducing global warming, mostly by cutting emissions but also through other means such planting forests to absorb carbon.
Adaptation is about minimizing the impact of climate change through such means as stronger sea defenses, changing farming practices and ultimately even moving populations to higher ground.
Finance in the Copenhagen context refers to transfers of aid from rich to poor nations to help them mitigate and adapt to global warming.
The European Union estimates developing nations will need 100 billion euros a year by 2020 to help them with mitigation and adaptation.
Meanwhile the International Energy Agency estimates that investment in renewable energies of $10.5 trillion will be needed to keep the global temperature increase to 2 degrees Celsius. It is a huge sum, but with the renewable energy sector already enjoying an annual turnover of 45 billion euros in Europe alone, there is money to be made in going green.
Governments on both sides of the Atlantic think investments in clean technology will bring a much needed boost to the economy. And once the wind turbines, solar panels, geothermal bore holes and the rest are in place, they will produce energy that is much cheaper than imported oil and gas.
Trees absorb CO2 and tropical deforestation is blamed for 20 percent of the increase in carbon emissions. Campaigners want Copenhagen to halve tropical deforestation by 2020 and halt it altogether by 2030. Developing nations are seeking funding to help them aim for such targets.
The original plan was for Copenhagen to produce a treaty that would commit nations to legally binding emissions targets.
Many in the United States, China, Russia and other countries regard a binding treaty as a threat to national sovereignty.
The failure of the U.S. Senate to pass climate change legislation in time for Copenhagen means that the most that can come from the meeting by Dec. 18 is a political agreement that will need to be turned into a legal document some time next year.