(CNN) — Keeping global warming down to a level people can live with means cutting carbon emissions to “near zero” by the end of the century, even in an increasingly industrialized world, the top U.N. experts on the issue concluded Sunday.
That may be doable, but it will take “substantial investments” in everything from planting more trees to replacing fossil fuels with low-carbon power sources like solar, wind and nuclear energy, the Intergovernmental Panel on Climate Change announced in its latest report. All that means replacing “business as usual” at a time when developing countries are trying to achieve the same living standards as the industrialized world, said Ottmar Edenhofer, a German economist and one of the lead authors of Sunday’s document.
“What this report clearly shows is that the challenges to resolve the global common problem are huge,” Edenhofer told reporters from Berlin, where the final document was approved over the weekend. “But also this report shows that there are some steps to resolve this issue. I would say in that sense the report also outlines the challenges, but it provides hope — modest hope.”
Edenhofer’s modest hope will require more than tripling the share of electricity produced by renewable sources or nuclear power, along with refining the still-evolving technology of capturing carbon emissions and storing them underground. And it will take a coordinated global effort, likely including taxes on emissions, he said.
No direct price tag was attached to that scenario, but Edenhofer said it would require “substantial investments,” and more delays just drive up the expected cost. The impact could amount to shaving the projected average growth of the global economy by six-tenths of a percentage point — from about 2% per year to 1.94% — over the coming century. The total global economy was about $72 trillion in 2012, according to World Bank figures.
“We are clearly arguing that achieving these goals is a huge technological and institutional challenge. We are not saying this is a free lunch,” Edenhofer said. “Climate policy is not a free lunch. But climate policy could be a lunch worthwhile to buy.”
Despite more than two decades of efforts to restrain carbon emissions, not only are emissions still going up, they’re going up faster than ever, Edenhofer said. Though there’s been an increased emphasis on generating power from renewable sources, the use of coal has gone up in the past 10 years, he said.
Limiting the projected increase in global average temperatures to 2 degrees Celsius (3.6 degrees F) over preindustrial times will require cutting emissions of carbon dioxide and other gases by 40% to 70% by 2050 “and to near zero by the end of this century,” the IPCC concluded.
Sunday’s report is the third part of a benchmark U.N. assessment that comes out every six years. The first, in September, reaffirmed the science behind the warming of the planet; the second, at the end of March, warned that chances to limit the increase in temperatures are slipping away, with the world’s poor expected to bear the worst of the effects.
The reports are aimed at guiding world leaders as the United Nations attempts to work out a new treaty to limit emissions in 2015. Previous rounds of talks have been strained by disputes among the biggest emitters — China, the United States and European countries — and poorer countries whose populations could see the worst impacts first.
About half of the carbon dioxide released into the atmosphere since the dawn of the industrial age has been produced since 1990, the scientists behind Sunday’s report concluded. On the current path, global average temperatures could go up anywhere from 3.7 to 4.8 degrees C (6.7 to 8.6 F) over preindustrial levels by 2100.
That would produce a world with higher sea levels, deeper droughts and more intense storms, along with oceans made more acidic by the absorption of carbon dioxide, with impacts on vital marine life that “we cannot estimate at this point in time,” IPCC Chairman Rajendra Pachauri said.
There’s “a broad set of technologies” that could be deployed to head off that future, Edenhofer said — many of which are listed in the report. And the document points to potential benefits of the effort, including cleaner air and healthier populations.
Leaders of some of the world’s biggest environmental groups called the report a positive one.
“The IPCC is clear that acting on climate change is possible, beneficial and affordable,” said Samantha Smith, the head of the World Wildlife Fund’s climate and energy program. “If we act now, costs will be only a very small fraction of global economies. Those who say it’s too hard and too expensive are wrong.” She said the report should convince investors “to pull your money out of dirty fossil fuels and put it into renewable energy and energy efficiency.”