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Preventing an extra degree of heat could make a difference in life and death over the next few decades for a multitude of people and ecosystems on this fast-warming planet, an international group of scientists reported Sunday. But they offer little hope to the world to rise to the challenge. The Intergovernmental Panel on Climate Change, winner of a Nobel Prize, released its gloomy report at a meeting in Incheon, South Korea. In a 728-page document, the UN organization explained how the weather, health and ecosystems of the Earth would be healthier if world leaders could limit future human-caused warming to only 0.9 degrees Fahrenheit (half a degree Celsius). of the globally agreed target of 1.8 degrees F (1 degree C). Among other things: – Half less people would suffer from a lack of water. – There would be fewer deaths and illnesses from heat, smog and infectious diseases. – The seas would rise nearly 4 inches (0.1 meter) less. – Half as many animals with backs and plants would lose the majority of their habitats. – There would be a lot less heat waves, showers and droughts. – The Western Antarctic Ice Sheet is not likely to irreversibly melt. – And that may be enough to save most of the coral reefs of the world from death. "For some people, it is undoubtedly a life-and-death situation," said Natalie Mahowald, a scientist in climatology at Cornell University, lead author of the report. Limiting warming to 0.9 degrees from now means that the world can maintain a "semblance" of ecosystems. The addition of 0.9 degrees more, the vaguer global goal, essentially means a different and more difficult Earth for humans and species, said another of the report's lead authors, Ove Hoegh-Guldberg, director of the Global Change Institute of the University of Queensland, Australia. However, to achieve the more ambitious goal of slightly less warming, one should immediately and drastically reduce emissions of heat-trapping gases and bring about radical changes in the energy field. Although, technically, the American group of experts stated that it was possible, the necessary adjustments were unlikely. In 2010, international negotiators adopted the goal of limiting warming to 2 ° C (3.6 ° F) since the pre-industrial era. This is called the 2 degree goal. In 2015, when the countries of the world approved the historic Paris agreement on climate, they set themselves a double objective: 2 ° C and a more demanding goal of 1.5 ° C compared to the previous year. pre-industrial era. The 1.5 was at the request of vulnerable countries that called the death penalty at 2 degrees. The world has already warmed by 1 degree C since the pre-industrial era, so it really does matter the difference of a half-degree C or 0.9 ° F from now. "There is no definitive way to limit the rise in global temperature to a level above 1.5 from pre-industrial levels," says the report requested by the United States. More than 90 scientists have written this report, which is based on more than 6,000 peer reviews. "Global warming is expected to reach 1.5 ° C between 2030 and 2052 it's continuing to increase at the current rate," the report says. At the bottom of the report, scientists say that less than 2% of the 529 of their possible future calculated scenarios kept warming below the target of 1.5, without the temperature exceeding that level and going back down. somehow in the future. The commitments made by countries in the Paris agreement in 2015 are "clearly insufficient to limit warming to 1.5%," said one of the study's lead authors, Joerj Roeglj from Imperial College London. "I just do not see the possibility of doing a quarter and a half" and even two degrees seem improbable, said Gregg Marland, environmental scientist of the University of Appalachia, does not belong to the panel of the But having tracked global emissions for decades. the US Department of Energy. He compared the report to an academic exercise wondering what would happen if a frog had wings. Yet the report's authors said they remain optimistic. Limiting bottom-up warming is "not impossible, but will require unprecedented changes," said the head of the American expert group, Hoesung Lee, at a conference during which scientists repeatedly refused to say how achievable this goal was. They said that it was up to governments to decide whether these unprecedented changes were being implemented. "We have a monumental task ahead of us, but it's not impossible," Mahowald said earlier. "This is our chance to decide what the world will look like. "To limit global warming for the purpose of reducing temperatures, the world needs" rapid and deep "changes in energy systems, land use, urban and industrial design, transportation and transportation. The annual levels of carbon dioxide pollution, which continue to increase now, are expected to fall by about half by 2030, then to be close to zero. " here 2050. Emissions of other greenhouse gases, such as methane, will also have to decrease.Streaming away rapidly fossil fuels such as coal, oil and gas could be more expensive than the Less ambitious goal, but that would eliminate the air of other pollutants.This would have the advantage of avoiding more than 100 million premature deaths during this century, indicated the report. "Climate risks p health, livelihoods, food security, water supply, human security and economic growth are expected to increase with global warming, "the report says, adding that the world's poor affected. Michael Oppenheimer, a scientist in climatology at Princeton University, said extreme weather conditions, especially heat waves, would be more lethal if the lower goal was exceeded. Achieving the goal more difficult to achieve "could reduce by about 420 million the number of people exposed frequently to extreme heat waves, and to about 65 million the number of people exposed to exceptional heat waves" , says the report. The deadly heatwaves that hit India and Pakistan in 2015 will virtually become annual events if the world achieves the hottest of the two goals, the report said. Coral and other ecosystems are also under threat. The report says that coral reefs "hot water will largely disappear". The result will determine if "my grandchildren will be able to see beautiful coral reefs," said Oppenheimer of Princeton. German biologist Hans-Otto Portner said the report would prompt scientists and citizens to act with speed and energy, said one of the leaders of the group of experts. "If no action is taken, the planet will face an unprecedented climatic future." ___ Follow Seth Borenstein on Twitter: @borenbears. His work can be found here. ___ The Science & Science Department of the Associated Press receives support from the Howard Hughes Medical Institute's Department of Science Education. The AP is solely responsible for all content. ___ This story has been corrected with respect to the cost of emissions more stringent than a less ambitious goal. It's more expensive, but not three to four times more expensive.