Scientists suggest penalties on carbon emitters of $50 per tonne from 2020, rising to $400 by 2050

* Plan slashes emissions by 2050 by issuing heft fines

* Authors think it will help achieve Paris climate pledges

* Currently EU charges 5 euro per tonne of carbon emissions

By Alister Doyle

OSLO, March 23 (Reuters) - Scientists proposed on Thursday a legislative and economic framework to halve the world's carbon dioxide emissions every decade from 2020 and combat climate change, by issuing hefty penalties on carbon emitters.

The proposal, published in the journal Science, outlines a "carbon law" policy, seeking to accelerate a global shift already under way towards clean energies such as solar and wind power.

Its concept is similar to a carbon tax, which charged on businesses and households for every tonne of carbon emitted.

The policy is envisaged by its authors as a mechanism for countries to enforce the 2015 Paris agreement. Almost 200 governments agreed to phase out net greenhouse gas emissions in the second half of the century by shifting from fossil fuels.

But since signing the agreement, signatories have done little to work out what this means in practice.

As a result, an international team of scientists suggested the Paris goals could be reached by 2050 if carbon emissions were halved every decade from 2020, falling to 20 billion tonnes by 2030 from 40 in 2020. The driver of change would be a charge of $50 per tonne from 2020. By 2050, the price would rise to $400.

Currently, the European Union charges 5 euros ($5.39) for each tonne of carbon emissions.

Such wrenching economic shifts would be needed "to make a zero-emissions future an inevitability rather than wishful thinking," they wrote in the journal.

Lead author Johan Rockstrom, director of the Stockholm Resilience Center at Stockholm University, said countries led by China and the European Union were likely to push ahead with ever greener technologies.

He also said that would come irrespective of U.S. President Donald Trump and his denial of man-made climate change.

"We should not be too concerned with the risks of the negative impact of the Trump administration," he told Reuters, adding that a shift from fossil fuels would have a variety of benefits ranging from improving public health to boosting businesses' profits.

Trump has sometimes dismissed man-made climate change - which can bring increased droughts, floods and heat waves - as a hoax. He has threatened to pull the United States out of the Paris Agreement, saying he wants to bolster the U.S. fossil fuel industry.

The carbon law is inspired by "Moore's Law", an observation that predicted the steady advances in computing power. Under the reversed scenario, coal use would end in the energy sector around 2030-35 and oil in 2040-45.

"I don't think it's wishful thinking. I think it's visionary thinking," Christiana Figueres, who was the U.N.'s climate chief and helped broker the Paris Agreement, told Reuters.

Figueres, who was not involved in the study, noted that energy-related carbon emissions stayed flat for the third year in a row in 2016, for instance, breaking years of growth. Solar power prices have plunged in recent years.

($1 = 0.9272 euros)

(Reporting by Alister Doyle; Editing by Vin Shahrestani)

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