BERLIN — The countries of the world have dragged their feet so long on global warming that the situation is now critical, experts appointed by the United Nations reported Sunday, and only an intensive worldwide push over the next 15 years can stave off potentially disastrous climatic changes later in the century.
It remains technically possible to keep planetary warming to a tolerable level, the Intergovernmental Panel on Climate Change found, according to a report unveiled here. But even in parts of the world like Europe that have tried hardest, governments are still a long way from taking the steps that are sufficient to do the job, the experts found.
“We cannot afford to lose another decade,” said Ottmar Edenhofer, a German economist and co-chairman of the committee that wrote the report. “If we lose another decade, it becomes extremely costly to achieve climate stabilization.”
The report is likely to increase the pressure to secure an ambitious new global climate treaty that is supposed to be completed in late 2015 and take effect in 2020. But the divisions between wealthy countries and poorer countries that are making such a treaty difficult, and have long bedeviled international climate talks, were on display yet again in Berlin.
Some developing countries insisted on stripping charts from the report’s executive summary that could be read as requiring greater effort from them, while rich countries — including the United States — struck out language implying that they needed to write big checks to the developing countries. Both points survived in the full version of the report, but were deleted from a synopsis meant to inform the world’s top political leaders.
The report did find some reasons for cautious optimism. The costs of renewable energy like wind and solar power are now falling so fast that their deployment on a large scale is becoming practical, the report said. In fact, extensive use of renewable energy is already starting in countries such as Denmark and Germany, and to a lesser degree in some American states, including California, Iowa and Texas.
Moreover, since the intergovernmental panel issued its last major report in 2007, far more countries, states and cities have adopted ambitious climate plans, an indication that the political determination to tackle the problem is growing in many parts of the world. They include China and the United States, which are both doing more domestically than they have been willing to commit themselves to in international treaty negotiations.
Yet the report found that the emissions problem is still outrunning the will to tackle it, with global emissions rising almost twice as fast in the first decade of this century than in the last decades of the 20th century. That reflects a huge rush to coal-fired power plants in developing countries that are climbing up the income scale, especially in China, while rich countries are making only slow progress in cutting their emissions, the report said. The longer countries delay aggressive action, the more difficult it will be to limit global warming to the level that the international community has agreed to, namely a rise in the global average temperature of no more than 3.6 degrees Fahrenheit (2 degrees Celsius) above the preindustrial level.
Scientists fear that exceeding the target degrees could potentially produce drastic effects, such as the collapse of ice sheets, a rapid rise in sea levels, difficulty growing enough food, massive die-offs of forests and mass extinctions of plant and animal species.
The Intergovernmental Panel on Climate Change is a United Nations body that includes hundreds of scientists, economists and other experts. The group periodically reviews the science and economics of climate change and issues major reports every five to six years. Along with Al Gore, it won the Nobel Peace Prize in 2007 for calling attention to the climate problem.
The new report, dealing with ways to limit the growth of the emissions that are causing climate change, is the third in recent months. A report released in Stockholm in September found a certainty of 95 percent or greater that humans are the main cause of climate change, while a report released in Yokohama, Japan, two weeks ago found that profound effects are already being felt around the world, and are likely to get much worse.
The latest report found that if countries keep stalling on tougher climate rules, trillions of dollars will be invested in coming years in power plants, cars and buildings that use too much energy from fossil fuels. The result, the report said, would be an emissions path that would be almost impossible to alter in time to get to the very low carbon pollution levels that scientists think are necessary by 2050.
The widespread perception that a scarcity of fossil fuels will lead to the development of alternatives in time to salvage the climate is wrong, Dr. Edenhofer said. That is because higher prices and improved drilling technology are leading to an intensified hunt for new fossil energy, and it effectively means that policies have to be found that will leave much of the world’s coal, oil and gas reserves in the ground.
“The scarcity of fossil fuels will not solve our problem,” Dr. Edenhofer said. “We are in the middle of a fossil fuel renaissance.”
The new report does not prescribe the actions governments need to take. But it does make it clear that putting a price on emissions of carbon dioxide and other greenhouse gases, either through taxes or the sale of emission permits, is a fundamental approach that could help redirect investment toward climate-friendly technologies.
The report says that “nuclear energy could make an increasing contribution to low-carbon energy supply, but a variety of barriers and risks exist.” It cited “operational risks, and the associated concerns, uranium mining risks, financial and regulatory risks, unresolved waste management issues, nuclear weapon proliferation concerns, and adverse public opinion.”
If climate targets are to be met, the report said, annual investment in electrical power plants that use fossil fuels will need to decline by about 20 percent in the coming two decades, while investment in low-carbon energy supply will need to double from current levels.
The report warned that if greater efforts to cut emissions do not begin soon, future generations seeking to limit or reverse climate damage will have to depend on technologies that can permanently remove greenhouse gases from the air — in effect, they will be undoing the damage that will have been caused by the people of today.
But these technologies do not now exist on any appreciable scale, the report said, and there is no guarantee that they will be available in the future, much less that they will be affordable.
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