Significant climate change may not be inevitable if governments take swift and decisive action now to reduce greenhouse gases, according to a report released Tuesday that rolls back some of the bleaker and more pessimistic assessments of recent climate negotiations.

The report, prepared for the United Nations by experts from leading research institutes from 15 countries, challenges the idea that the world can’t avoid breaching a 2 degrees Celsius rise in global average temperature — many climate scientists have warned that an increase of 3 to 4 C is now inevitable.

Moreover, they suggest defeatism on the 2 C limit target would contribute to dithering by heavily industrialized countries most responsible for climate change — the United States, China, India, major European economies and rising economic powers like Brazil and South Africa.

“We do not subscribe to the view held by some that the 2 C limit is impossible to achieve and that it should be weakened or dropped altogether,” the authors of the report from the Deep Decarbonization Pathways Project (DDPP) wrote.

Since the start of the industrial revolution two hundred years ago, the Earth’s atmosphere has seen a dramatic spike in carbon dioxide released by burning coal, oil and methane. As the gases trap solar radiation, the planet has already warmed about a degree over the last century, and scientists say the effects are already being felt and can be seen in melting glaciers, rising sea levels and droughts — problems which are forecast to become far worse if nothing is done to reduce carbon output.

The task is massive, since a great deal of the world’s economic and social activity demands energy that is currently primarily produced by burning fossil fuels.

But the authors of the report believe the world might be up to the challenge, despite gloomy assessments elsewhere.

The project, a collaboration of experts across the world working under the U.N.’s Sustainable Development Solutions Network, presented its study of climate change solutions Tuesday to U.N. Secretary General Ban Ki-moon, ahead of a September U.N. climate conference in New York and next year’s global summit in Paris.

Jeffrey Sachs, development economist and director of the Earth Institute at Columbia University, helped lead the project and criticized previous attempts to come to a meaningful agreement on climate change.

Past negotiations put “lawyers out front and left the technologists out of the room, and the result is that we have had 21 years of lawyering and no success in application of the international framework,” Sachs said, according to the Guardian.

The report said the concept of inevitable climate change above 2 degrees Celsius is potentially toxic to the success of global negotiations, which faltered at the last major global summit, the COP15 in Copenhagen in 2009.

If countries act as though nothing can be done, they might be unwilling to take the kind of ambitious action necessary to reduce emissions to 2 C, above which there will be “grave and irreversible harm” done to humans and our planet. Or, worse, the worst polluters could attempt to reach consensus on a target deemed easier to reach, the report said.

“The political risks of jettisoning the 2 C limit are also significant,” the report stated. “If the world fails to mobilize in support of the 2 C limit or if countries try to weaken it there will be no realistic prospect for the international community to agree to another quantitative target.”

While more optimistic than recent grim reports from the U.N.’s Intergovernmental Panel on Climate Change, which foresee a planet and human civilization mutilated by climate change, the scientists behind the DDPP stressed the urgency of action.

“The issue is to convince the world that the future is as important as the present. Paris 2015 may well be our last hope,” said Fatih Birol, the International Energy Agency’s top economist.

The report says carbon polluters must make strides to increase energy efficiency, invest significantly in renewable energy in electricity production and carbon capturing, and, finally, promote forms of transportation and heating that don’t release the same volume of greenhouse gases into our atmosphere.

The report found that some of the technologies necessary to stem rising carbon levels do not exist yet or need further development.

“Countries and the international community as a whole must undertake a major research, development, demonstration, and diffusion (RDD&D) effort to develop low-carbon technologies and ensure their widespread availability and their affordability,” the report stated.