“We must act quickly and decisively if we want to avoid increasingly disruptive outcomes,” UN Secretary-General Ban Ki- moon told reporters in Copenhagen. “If we continue business-as- usual, our opportunity to keep temperature rises below” the internationally agreed target of 2 degrees Celsius, “will slip away within the next decades,” he said.

The report is designed to guide policy makers around the world in writing laws and regulations that will curb greenhouse gases and protect nations most at risk from climate change. It will also feed into talks among 195 nations working on an international agreement to rein in emissions that envoys aim to reach in Paris in December 2015.

“We need to get to zero emissions by the end of this century” to keep global warming below dangerous levels, Ottmar Edenhofer, chief economist at the Potsdam Institute for Climate Impact Research Institute, outside Berlin, and a co-author of the report, said in a telephone interview. “This requires a huge transformation, but it doesn’t mean we have to sacrifice economic growth.”

Nobel Prize

The report is the culmination of five years of unpaid work by thousands of scientists, who sifted through research into all areas of global warming and condensed the conclusions into a single document that summarizes the most relevant findings. The panel, which has won a Nobel prize for its work, last carried out the exercise in 2007 and has become more certain about the threat since.

“Continued emission of greenhouse gases will cause further warming and long-lasting changes in all components of the climate system, increasing the likelihood of severe, pervasive and irreversible impacts for people and ecosystems,” according to the report. “Limiting climate change would require substantial and sustained reductions in greenhouse-gas emissions which, together with adaptation, can limit climate change risks.”

Narrative Sought

Delegates from about 120 nations spent the past week combing through the report line-by-line to ensure dense scientific findings were put into words understandable to a policy maker. Countries had submitted more than 2,000 comments about an earlier draft of the text, with U.S. envoys pushing for a “threading narrative,” and European Union officials saying the storyline “looks fragmented.”

Today’s study sought to link three earlier reports by the panel. Those detailed the observed physical impacts of climate change, the resulting damage and the tools governments have at their disposal to curtail emissions.

“It is technically feasible to transition to a low-carbon economy,” said Youba Sokona, another report co-author. “But what is lacking are appropriate policies and institutions. The longer we wait to take action, the more it will cost to adapt and mitigate climate change.”

Exxon Mobil

Companies including Exxon Mobil Corp and Royal Dutch Shell Plc have said they don’t see a danger of their assets becoming “stranded” as a result of climate-change regulation.

Ambitious emissions-reduction measures would shave just 0.06 percentage points off annualized economic growth this century compared to a business-as-usual scenario, the UN panel said. That doesn’t factor in the benefits of reduced climate change linked to human health, livelihoods and development, it said.

Other key findings highlighted by the panel include:

• Manmade greenhouse gas emissions have pushed atmospheric concentrations of carbon dioxide, methane and nitrous oxide to levels “unprecedented” in the past 800,000 years.
• Giving the world a two-in-three chance or more to cap the level of warming since the 1800s at 2 degrees Celsius (3.6 degrees Fahrenheit) requires total emissions since 1870 to be limited to about 2,900 billion tons of carbon dioxide, two thirds of which had already been emitted by 2011. Policies to cut emissions may devalue fossil-fuel assets and reduce revenues for fossil-fuel exporters.

Sea Level

• The global average sea level has risen by about 19 centimeters (7.5 inches) since 1901 and is likely to rise by 26 centimeters to 82 centimeters this century.
• The global average temperature has risen by 0.85 of a degree Celsius since 1880, and the panel predicts a gain of 0.3 degrees to 4.8 degrees for this century.

Economic damage resulting from climate change accelerates with increasing temperature. An increase of 2.5 degrees above pre-industrial temperatures would cut economic output by as much as 2 percent. The panel said there were “limitations” in this analysis.

Future scenarios that limit the global temperature rise to 2 degrees, an internationally agreed target, involve almost quadrupling the share of zero-carbon technologies in energy supply. These include wind and solar power, nuclear reactors and fossil fuels equipped with carbon capture and storage equipment.

Cost reductions and performance improvements in renewables enable governments to decarbonize their economies at a price that’s lower than ever, according to Samantha Smith, who leads the climate program at environmental group WWF.

U.S. Secretary of State John Kerry said the report sends a strong message around the world.

“The longer we are stuck in a debate over ideology and politics, the more the costs of inaction grow,” Kerry said today in an e-mailed statement. “Those who choose to ignore or dispute the science so clearly laid out in this report do so at great risk for all of us and for our kids and grandkids.”

Copyright 2014 Bloomberg

Lead image: Climate change sign via Shutterstock