PUBLISHED October 7, 2018

Brazil is one of several key countries where deforestation must be limited in order to stave off global warming, a new international report says. Photograph by John Stanmeyer, National Geographic Creative

The impacts and costs of 2.7 degrees Fahrenheit (1.5 degrees Celsius) of global warming will be far greater than expected, according to a comprehensive assessment by the Intergovernmental Panel on Climate Change (IPCC) released Sunday in Incheon, South Korea.

The IPCC also reported that 2.7 degrees Fahrenheit could be reached in as little as 11 years—and almost certainly within 20 years without major cuts in carbon dioxide (CO2) emissions. Even if such cuts were to begin immediately it would only delay, not prevent, 2.7 degrees Fahrenheit of global warming.

“Substantial Consequences”

While a 0.9 degrees Fahrenheit (0.5 degrees Celsius) increase in room temperature is unnoticeable, permanently heating the whole planet that much will have “substantial” consequences, the report warns. The impacts will be felt across ecosystems and human communities and economies.

close Canoes are vital for transportation on the rain forest rivers of the Republic of the Congo. The Congo Basin’s 500 million acres of tropical forest, second-largest in the world after the Amazon, are known for an incredible array of wildlife including great apes, forest elephants, and some 700 species of river fish. But people have also lived here for over 50,000 years. The Congo Basin currently provides water and food to about 75 million Africans. Photograph by Michael Nichols, National Geographic close A scarlet macaw is caught munching a snack in Brazil's Amazon rain forest. These birds are best known for their loud cackles, four-toed feet, and brilliant plumage. Photograph by Annie Griffiths Belt, National Geographic close Limited space in dense rain forests results in many unique plants, like this fig tree in the Philippines, which produces fruit on runners that come from its trunk instead of on its branches. Photograph by Timothy G. Laman, National Geographic close A lizard suns itself on a leaf in the El Yunque National Forest in Puerto Rico. El Yunque is the only tropical rain forest in the U.S. National Forest system, which protects the 28,000 acres (11,331 hectares) in the Luquillo Mountains Photograph by Brian Stinga, Your Shot close A monkey from the Malaysian rain forest digs into a coconut snack. Malaysia is still heavily forested, about 60 percent of the nation is tree-covered, but deforestation has proceeded rapidly during the nation’s recent economic development. rain forests harbor tremendous biodiversity and those covering Peninsular Malaysia’s highlands also give rise to the rivers which supply 90 percent of the nation’s freshwater needs. Photograph by Nader Alhareedi, Your Shot close Streams on Costa Rica’s remote Osa Peninsula flow through one of the world’s outstanding examples of lowland tropical rain forest, protected here by Corcovado National Park. Costa Rica’s signature park boasts an array of colorful flora and fungi and an amazing variety of larger animals, from estuary-dwelling crocodiles to secretive jaguars. Photograph by Alexander Ross, Your Shot close A species of mushroom called Amanita muscaria or Fly agaric dots the floor of a temperate coastal rain forest in the Canadian province of British Columbia. Identified by the white patches on its cap, this species of fungus can grow up to a foot hight with a top as big as a dinner plate in some regions. It is referred to as the fly agaric because people have been known to use pieces of the mushroom to attract and kill flies. Photograph by Ian McAllister, Getty Images close Moss drapes a stand of Sitka spruce in the Hoh River Valley, a U.S. temperate rain forest in Washington State. Trees here often host plants that grow on other plants, such as moss. Photograph by Sarah Leen, National Geographic close The cassowary has an intimidating stare and the bulk to back it up. These Australian rain forest-dwellers are the second-largest birds in the world, reaching 5.5 feet (1.7 meters) and 155 pounds (70 kilograms) and looking up only to the ostrich. Cassowaries tend to avoid humans but can use their powerful legs and dagger-like nails to deliver punishing blows to any aggressors. Though they run, jump, and swim well, cassowaries cannot fly. Photograph by Heshan de Mel, Your Shot close Baby white-faced capuchin monkeys play in a Costa Rican rain forest. Unlike these familiar faces, the majority of rain forest species are yet to be named, formally described, or analyzed. Photograph by Wolfgang Kaehler, Alamy close The rhinoceros hornbill is named for its characteristic “casque,” the strange structure situated on top of the bird’s bill. The uses of this “horn” aren’t fully understood but casques may play a role in attracting mates or amplifying bird calls. Rhinoceros hornbills feed mainly on fruit found in rain forest trees. They typically live in pairs and are known for an amazing nesting strategy during which the male seals up the female inside a hollow tree, leaving only a tiny beak hole through which to feed her and their young. Photograph by Timothy G. Laman, National Geographic close The red-eyed tree frog is an icon of the Central American rain forest. When asleep, it's green color provides effective camouflage. When threatened, the red of suddenly-exposed eyes or legs may startle predators and enable an escape. Female frogs lay eggs on leaves overhanging water so that their tadpoles will fall into ponds. The tadpoles feed on insects in the water until they develop into frogs and take to the trees. Photograph by Roy Niswanger, Your Shot close Sunny rays penetrate the canopy of an Indonesian rain forest on Nias Island. Rain forests are among the Earth’s most biologically diverse habitats. Their fauna and flora are precious for their own sake but can also aid humans. Rain forest plants, for example, produce chemicals to combat insects and disease that have led to the development of many beneficial drugs. But rain forests around the world are being deforested at alarming rates—even as many of their species and secrets remain unknown to humans. Photograph by Fakhrurrazi Fakhrurrazi, Your Shot close Climbers John "Razor Sharp" Benson weaves through skin-ripping pinnacles. In Malagasy, the formations are called tsingy, meaning "where one cannot walk barefoot." The terrain resists intrusions from hunters, hungry cattle, and wildfires. See more pictures from the November 2009 feature story "Living on a Razor's Edge." Photograph by Stephen Alvarez, National Geographic close Moss-draped trees, shrubs, and ferns adorn the Hoh River Valley, a temperate rain forest in Washington State's Olympic National Park. Its trees include big leaf maples, western hemlock, and Sitka spruce. Photograph by Sarah Leen close Moss-draped conifers and ferns populate Quinault, a Pacific rain forest in Washington State's Olympic National Park. The Park is a UNESCO World Heritage site. Photograph by Ryan McVay/Getty Images close Foul-smelling skunk cabbage bloom along the Quinault River in Washington's Hoh River Valley temperate rain forest. The Park is a UNESCO World Heritage site. Photograph by Sam Abell close Fog crowns towering conifers, such as Douglas fir and yellow cedar, in the Pacific temperate rain forests of Vancouver, British Columbia. Temperate rain forests get much of their water from moisture-laden ocean winds. Photograph by Taylor S. Kennedy close A U.S. temperate rain forest, the Hoh River Valley is part of Washington State's Olympic National Park. Its trees include big leaf maples, western hemlock, and Sitka spruce. Photograph by Sam Abell close Tap images for captions

“Limiting global warming to 1.5°C compared with 2°C would reduce challenging impacts on ecosystems, human health, and well-being,” said Priyardarshi Shukla, Chair of the Global Centre for Environment and Energy at Ahmedabad University in India and co-author of the Special Report, in a statement. Such impacts include stronger storms, more erratic weather, dangerous heat waves, rising seas, and largescale disruption to infrastructure and migration patterns.

The scientific findings in the main report are summarized in a 34-page “Summary for Policy Makers,”which was approved by all representatives from 195 nations, including the U.S.

Under the 2015 Paris Agreement, every country in the world agreed to keep global temperatures well below 3.6 degrees Fahrenheit (2 degrees Celsius), while low-lying island states and others lobbied for substantially less. Current pledges to cut CO2 emissions will push global warming to at least 5.4 degrees Fahrenheit (3 degrees Celsius) by 2100, risking natural tipping points such as thawing of large areas of permafrost—which could drive global temperatures uncontrollably higher. The Trump administration has said they will pull the U.S. out of the Paris Agreement.

Global warming is like being in a mine field that gets progressively more dangerous, says Michael Mann, a climatologist and director of the Earth System Science Center at Penn State. “The further we go the more explosions we are likely to set off: 1.5C is safer than 2C, 2C is safer than 2.5C, 2.5C is safer than 3C, and so on,” said Mann, who was not directly involved in this latest IPCC report.

“Stabilizing global warming at 1.5C will be extremely difficult if not impossible at this point,” Mann said via email.

Big Solutions Sought

The IPCC’s Special Report lays out various pathways to stabilize global warming at 2.7 degrees Fahrenheit (1.5 degrees Celsius). These solutions all require unprecedented efforts to cut fossil-fuel use in half in less than 15 years and eliminate their use almost entirely in 30 years. This means no home, business, or industry heated by gas or oil; no vehicles powered by diesel or gasoline; all coal and gas power plants shuttered; the petrochemical industry converted wholesale to green chemistry; and heavy industry like steel and aluminum production either using carbon-free energy sources or employing technology to capture CO2 emissions and permanently store it.

In addition, depending on how fast emissions are cut, between 0.4 and 2.7 million square miles (1-7 million square kilometers) of land may have to be converted to growing bioenergy crops and up to 3.86 million square miles (10 million square kilometers) of forests added by 2050. And still that won’t be enough, the report warns. Every pound of CO2 emitted in the last hundred years will continue to trap heat in the atmosphere for hundreds of years to come. By 2045 or 2050 there will still be too much CO2 in the atmosphere. More forests or some form of direct capture that takes CO2 out of the atmosphere will be essential to stabilize global temperatures at 2.7 degrees Fahrenheit (1.5 degrees Celsius), the report says.

The Special Report is like getting a troubling diagnosis from your doctor, said Katharine Hayhoe, a climate scientist at Texas Tech University. “Every possible test has been done and the news is not good,” Hayhoe said in an interview. “The doctor, the IPCC in this case, then explains possible treatment options to ensure our future health. We (the public) decide which option to follow.”

The challenge to stay below 3.6 degrees Fahrenheit (2 degrees Celsius) is immense, requiring fossil fuel infrastructure to be phased out, non-fossil energy sources phased in, and large-scale removal of carbon from the atmosphere, says Glen Peters, Research Director at Norway’s Center for International Climate Research. “To stay below 1.5 C simply requires the transformation be faster and deeper than for 2C,” Peters said.

Currently, we are going in the wrong direction with global emissions increasing 1.5 percent in 2017 and a likely increase this year, he said. “Without the full involvement and alignment of our technical, social, and political dimensions, 1.5 C and even 2C won’t be possible.”

That means 2.7 degrees Fahrenheit is a big departure from where we are headed now, agrees Kelly Levin, a senior associate with World Resources Institute’s Global Climate Program. That said, the models used to develop the IPCC’s pathways to 2.7 degrees Fahrenheit don’t include all the ways emissions could be reduced and they prioritize the cheapest methods, Levin said in an interview.

Climate 101: Causes and Effects

For example, a widespread dietary shift to eating less meat and reduced material consumption would significantly lower emissions. The models are also conservative when it comes to the roll out of new technology and have underestimated the success of solar panels and electric vehicles, Levin said. Tesla’s Model 3 electric car was the 4th best selling car in the United States in September, despite being more than twice as expensive than comparable gasoline-powered cars (and often requiring long waiting lists).

The Critical Role of Forests

Forests could also play a much bigger role in cutting emissions, says Deborah Lawrence, a forest expert at the University of Virginia. “Forests provide a super-important service to humanity by currently removing about 25 percent of our CO2,” Lawrence said in an interview.

Reforestation and improving forest management together could remove CO2 from the atmosphere, said Lawrence, amounting to 18 percent of the reductions needed by 2030. Brazil, China, India, Mexico, Australia, the U.S., Russia, and the European Union could also substantially increase their forests economically and without impacting food production—while potentially removing billions of tonnes of CO2 from the atmosphere, a forthcoming study will show, Lawrence said. Protecting and increasing tropical forests is especially important since they cool the air and are key in creating regional rainfall for growing food.

When the wood from mature forests is converted into furniture or buildings CO2 can be stored for the long term, she said. That’s one reason a 12-story building made of wood will be completed in Portland in 2019, and a 24-story wooden building is being built in Vienna, Austria.

Existing forests must be protected to avoid dangerous climate change, warn a coalition of forest scientists in a statement. The world’s forests contain more carbon than exploitable oil, gas, and coal deposits, they note.