BERLIN — Delivering the latest stark news about climate change on Sunday, a United Nations panel warned that governments are not doing enough to avert profound risks in coming decades. But the experts found a silver lining: Not only is there still time to head off the worst, but the political will to do so seems to be rising around the world.
In a report unveiled here, the Intergovernmental Panel on Climate Change found that decades of foot-dragging by political leaders had propelled humanity into a critical situation, with greenhouse emissions rising faster than ever. Though it remains technically possible to keep planetary warming to a tolerable level, only an intensive push over the next 15 years to bring those emissions under control can achieve the goal, the committee 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 good news is that ambitious action is becoming more affordable, the committee found. It is increasingly clear that measures like tougher building codes and efficiency standards for cars and trucks can save energy and reduce emissions without harming people’s quality of life, the panel found. And the costs of renewable energy like wind and solar power are falling so fast that its deployment on a large scale is becoming practical, the report said.
Moreover, since the intergovernmental panel issued its last major report in 2007, far more countries, states and cities have adopted climate plans, a measure of the growing political interest in tackling the problem. They include China and the United States, which are doing more domestically than they have been willing to commit to in international treaty negotiations.
Yet the report found that the emissions problem is still outrunning the determination to tackle it, with atmospheric carbon dioxide levels rising almost twice as fast in the first decade of this century as they did in the last decades of the 20th century. That reflects a huge rush to use coal-fired power plants in developing countries that are climbing up the income scale, especially China, while rich countries are making only slow progress in cutting their high emissions, the report said.
Some developing countries insisted on stripping charts from the report’s executive summary that could have been read as requiring greater effort from them, while rich countries — including the United States — struck out language that might have been seen as 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 new report does not prescribe the actions that governments need to take. But it does make 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.
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 will need to double from current levels.
The report warns that if greater efforts to cut emissions are not implemented soon, future generations seeking to limit or reverse climate damage will have to depend on technologies that permanently remove greenhouse gases from the air; in effect, they will be trying to undo the damage caused by the people of today.
But these technologies do not 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.
The intergovernmental panel warned that the longer countries delayed aggressive action, the more difficult it would 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 that level could produce drastic effects, such as the collapse of ice sheets, a rapid rise in sea levels, difficulty growing enough food, huge die-offs of forests, and mass extinctions of plant and animal species.
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 were the main cause of global warming, and a report released in Yokohama, Japan, two weeks ago said profound effects were already being felt around the world, and were 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 authors found that tackling the problem in a serious way would carry large costs, shaving a few hundredths of a percentage point off global economic growth each year. By the end of the century, societies would most likely be far richer than today, but almost 5 percent poorer than they would have been had they not spent the money to protect the climate, according to the study.
“Climate policy is not a free lunch,” Dr. Edenhofer said at a news conference Sunday in Berlin.
Against those costs, the economic benefits of acting are essentially impossible to calculate, the report found. The biggest reason is that scientists do not know how likely it is that unchecked global warming could cause some sort of wildly expensive calamity, such as a rapid melting of ice sheets that would drown the world’s major coastal cities. This and other disasters are distinctly possible, the authors found.
In essence, the committee described money spent fighting climate change as a form of insurance against the most severe potential consequences. “It is up to the public and up to decision makers to decide if it is affordable or not,” Dr. Edenhofer said.
The report was quickly welcomed in Washington, where President Obama is trying to adopt aggressive climate policies despite congressional opposition. His science adviser, John P. Holdren, said the report showed that “the longer society waits to implement strong measures to cut greenhouse gas emissions, the more costly and difficult it will become to limit climate change to less than catastrophic levels.”