London and Berlin - The world needed to triple the energy it got from renewables, nuclear reactors and power plants that used emissions-capture technology to avoid dangerous levels of global warming, UN scientists said.

Investments needed to keep climate change within safe limits would shave a fraction of a percent off annual global growth, the UN said yesterday in the third part of its most comprehensive study on warming. A delay in stemming rising greenhouse gases would cut chances to limit the global temperature rise, add to costs and lead to increasing reliance on unproven technologies.

“The longer we wait to implement climate policy, the more risky the options we’ll have to take,” said Ottmar Edenhofer, a co-chair of the 235 scientists who drafted the report, in Berlin.

“We need to depart from business as usual, and this departure is a huge technological and institutional challenge.”

The UN said governments must accelerate efforts to build wind farms and solar parks and provide incentives to develop carbon capture and storage technology for fossil-fuel plants by making it more costly to emit carbon. The study aims to guide envoys from 194 nations next year as they devise a new deal to slash greenhouse gases.

The researchers said emissions growth accelerated to an average of 2.2 percent a year between 2000 and 2010 from an annual 1.3 percent the preceding three decades. That puts in jeopardy the target agreed by climate treaty negotiators to stabilise warming since pre-industrial times to below 2ºC.

In 2100 “either you’ll have some fossil-fuel power generation with carbon capture and storage, or a complete switchover to renewables and smart energy storage”, said Jonathan Grant at consultancy PwC in London. “The problem with some of those scenarios is the transition takes too long.”

Without extra effort to cut greenhouse gases, their concentration may triple, pushing warming since 1750 from 3.7ºC to 4.8ºC, according to the report.

The assessment by the UN Intergovernmental Panel on Climate Change is intended as a reference for officials around the world as they devise emissions-curbing policies. Hundreds of scientists and government officials have spent the past week in Berlin editing a draft line by line to put it into clearer wording that’s understandable to policymakers.

The researchers said measures to reduce emissions might cost as much as 4 percent of global consumption in 2030 and 11 percent in 2100.

Some countries, including the US and UK, said the cost numbers risked skewing the data and lending support to those sceptical of spending money to tackle climate change. To allay those concerns, the researchers explained the costs were the cumulative effect of shaving about 0.06 percentage points off annual consumption growth projected to be 1.6 to 3 percent.

To meet the 2ºC goal, annual spending on fossil fuel plants must drop by $30 billion (R314bn) a year by 2030, the panel said. Annual expenditure on renewables, nuclear, and carbon capture and storage must rise by $147bn, and spending on energy efficiency measures for transport, buildings and industry must increase by $336bn. – Bloomberg