* China, German nuclear suspension, Japan crisis to up CO2
* Means more reliance on coal, natural gas
* Renewables very unlikely to cover shortfall in capacity
By Daniel Fineren and Nina Chestney
LONDON, March 16 (Reuters) - Global warming will intensify if leading carbon emitter China drops the world&${esc.hash}39;s most ambitious nuclear power building programme and Germany shuts down its nuclear plants amid panic over Japan&${esc.hash}39;s atomic energy crisis.
Wednesday&${esc.hash}39;s decision by the world&${esc.hash}39;s biggest coal burner and largest climate-warming carbon emitter to suspend approvals for new nuclear plants follows a decision by Europe&${esc.hash}39;s biggest carbon emitter Germany to shut seven nuclear plants.
Japan, already the world&${esc.hash}39;s fifth biggest carbon emitter before Friday&${esc.hash}39;s tsunami shut several of its nuclear plants, has little choice but to burn more gas and coal to make up for the loss of its low-carbon reactors.
Reacting to the crisis caused by a earthquake and tsunami in Japan, China&${esc.hash}39;s decision to freeze plant approvals threatens to increase carbon emissions. A similar response in land-locked Switzerland and major earthquake-free Germany may also mean much more is emitted by the European energy sector.
"This will definitely increase emissions as it will affect the long-term demand for gas," Isabelle Curien, analyst at Deutsche Bank, said.
"If we want to have a low-carbon economy by 2050, not using nuclear would require huge access to renewable energy and I am not sure that can be done in such proportions."
As well as being the leading cause of man-made climate change, burning coal is also a leading cause of smog, acid rain, bronchitis, aggravated asthma and premature death, according to the Union of Concerned Scientists.
China, which U.S. climate envoy Todd Stern estimates could be emitting 60 percent more carbon than the United States by the end of the decade, had been banking on nuclear power to cut its dependence on coal over the next decade, with a target to start building 40 gigawatts of new capacity by 2015. It seems unlikely Beijing will abandon those plans and it has not yet ordered its existing ones to shut. But the freeze could delay their construction while coal-fired power plant building continues unabated.
Germany&${esc.hash}39;s decision to shut seven of its oldest reactors at least until June will also likely lead to more pollution being billowed into the atmosphere.
"I would expect plants that burn coal to be the most likely replacement for those reactors. Which means you will have between 8 and 11 million additional tonnes of CO2 in the coming months," said Matteo Mazzoni, a carbon analyst at Italy&${esc.hash}39;s Nomisma Energia.
Should Germany go a step further and shut all of its exiting reactors down, replacing them with fossil fuels could boost its emissions by at least 400-435 million tonnes between now and 2020, analysts estimate.
The head of Greenpeace International&${esc.hash}39;s renewable division said the closure of the nuclear plants would have no carbon impact because Germany&${esc.hash}39;s coal plants already run flat out most of the time.
"They are usually running 24/7 anyway so an increase in output is almost impossible," Sven Teske said.
"We do have a lot of surplus wind power we could add which are usually switched off," he said, adding that more energy efficiency and a little more gas-fired production could fill in the gap.
GLOBAL IMPACT
The global impact of Japan&${esc.hash}39;s nuclear problems on climate change is impossible to judge with the plant&${esc.hash}39;s operators still trying to avert a major nuclear disaster.
The International Energy Agency, which advises the world&${esc.hash}39;s biggest industrial member countries of the OECD, warned against a knee-jerk reaction against nuclear and said it was impossible to slash carbon emissions without atomic energy.
But as the global panic around Japan&${esc.hash}39;s nuclear problems grew, Europe&${esc.hash}39;s energy chief raised the prospect of a nuclear-free future, which environmental groups say could and should be greener but others say will likely be gassier.
"The Japanese tragedy could lead to a setback for the world&${esc.hash}39;s nuclear renaissance (except perhaps in China)," analysts at French bank Societe Generale said, adding that gas will likely become the fuel of "no choice" in OECD countries where voters may decide against nuclear power.
SocGen estimates that if all 34 countries in the OECD, which does not include China, were to shut their nuclear power plants and replace them with gas plants before technology to capture their carbon emissions is developed, OECD carbon emissions could rise by nearly one billion tonnes of CO2 a year.
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