OSLO (Reuters) - An architect of the Paris climate agreement urged governments on Tuesday to halt oil exploration in the Arctic, saying drilling was not economical and warming threatened the environmentally fragile region.

FILE PHOTO: Former United Nations climate chief Christiana Figueres speaks to the media after Costa Rica's President Luis Guillermo Solis nominated her as a candidate for the post of Secretary-General of the United Nations at the National Theatre in San Jose, Costa Rica July 7, 2016. REUTERS/Juan Carlos Ulate

Christiana Figueres, formerly head of the U.N. Climate Change Secretariat when the Paris accord was reached by almost 200 nations in 2015, told Reuters by telephone “the Arctic has been rendered undrillable.”

The past three years have been the hottest since records began in the 19th century, and Figueres said the heat was a threat to everything from Australia’s Great Barrier Reef to ice in Antarctica.

The former Costa Rican diplomat who campaigns for a peak in global emissions by 2020 said it made no economic sense to explore in the Arctic, partly because it was likely to take years to develop any finds.

Capital investment would be better used developing renewable energies such as solar and wind to cut emissions, she said.

“The stakes are visibly higher than they were just a few years ago,” she said.

Figueres will give a speech in Oslo on Tuesday at the Business for Peace Foundation, which seeks to promote ethical business practices.

The Paris Agreement sets a goal of ending the fossil fuel era in the second half of this century. It has been weakened by a planned pullout by U.S. President Donald Trump, who doubts mainstream scientific findings that global warming is man-made.

Many governments and companies favor Arctic drilling.

Last month, Trump’s administration began environmental reviews for oil and gas drilling in a section of the Arctic national Wildlife Refuge.

In Norway, Statoil and other companies plan to keep up exploration in the Arctic Barents Sea, which is ice-free further north than other parts of the Arctic thanks to the warm Gulf Stream..

“This area is actually less challenging in terms of weather and waves than many other parts of Norway ... We have drilled more than 100 wells, and never had any significant accidents or discharges to sea,” Statoil spokesman Bård Glad Pedersen said.

Although Figueres said drilling in the Arctic did not make sense, Pedersen said the Johan Castberg field, due to start pumping in the early 2020s off north Norway, would have a break-even of $31 a barrel.

Global warming is also making the Arctic - shared by Nordic nations, Russia, Canada and the United States - more accessible to shipping and mineral exploration.