Climate change fight affordable, cut emissions to zero by 2100: UN

Governments can keep climate change in check at manageable costs but will have to cut greenhouse gas emissions to zero by 2100 to limit fast-worsening risks, a U.N. report showed on Nov. 2.
   
The 40-page synthesis, summing up 5,000 pages of work by 800 scientists already published since September 2013, said global warming was now causing more heat extremes, downpours, acidifying the oceans and pushing up sea levels.
   
"There is still time, but very little time" to act at manageable costs, Rajendra Pachauri, chair of the Intergovernmental Panel on Climate Change (IPCC), told Reuters.
   
He was referring to a U.N. goal of limiting average surface temperature rises to 2 degrees Celsius (3.6F) above pre-industrial times. Temperatures are already up 0.85 C (1.4F).
   
To get a good chance of staying below 2C, the report says that world emissions would have to fall to "near zero or below in 2100." U.N. Secretary-General Ban Ki-moon will help present the report in Copenhagen on Sunday.
   
The study, given authority by the approval of officials from more than 120 governments in a week of editing, will be the main handbook for 200 nations which are due to agree a U.N. deal to combat global warming in Paris in late 2015.
    
Renewables, nuclear
   
The report points to options including energy efficiency, a shift from fossil fuels to wind or solar power, nuclear energy or coal-fired power plants where carbon dioxide is stripped from the exhaust fumes and buried underground.
   
But carbon capture and storage (CCS) technologies are little tested. In most scenarios, the report says "fossil fuel power generation without CCS is phased out almost entirely by 2100".
   
China, the United...