Linber Anej lives in the Marshall Islands, a tiny nation in the Pacific Ocean that's slowly but surely being swallowed by the sea. Every day, Anej joins a group of men and boys who wade into the water at low tide and gather chunks of concrete and metal scraps to rebuild a seawall in front of his home.
It's a losing battle. The temporary barrier is no match for the rising tides that regularly flood the shacks and muddy streets with salt water and raw sewage.
"It's insane, I know," says Anej, 30, who lives with his family of 13 in a four-room house. "But it's the only option we've got."
Standing near his house, he says, "I feel like we're living underwater."
Thanks to climate change, it may not be long before the Marshall Islands are literally underwater, most scientists agree. That's because the rise in Earth's temperature causes a host of side effects, including flooding from rising seas, severe drought, and more destructive weather in general.
With low-lying nations like the Marshall Islands already feeling the effects of climate change on a daily basis, the world has started to take action after many years of delays. In December, the U.S. and 194 other nations agreed to a landmark accord (see box, p. 17) that commits them to lowering the greenhouse gas emissions that scientists say are heating up the planet. The goal is to try to prevent the worst effects of climate change from happening.
Those effects are already evident around the world (see map, p. 16), according to scientists. In Bangladesh, rising sea levels have forced millions to leave coastal villages along the Bay of Bengal. In Mali, an impoverished African country, drought is making farming increasingly difficult. And in the northwestern U.S., the Pacific Ocean is encroaching upon lands the Quinault Indian Nation has lived on for thousands of years.
In January, weather researchers confirmed that 2015 was the hottest year worldwide since record keeping began in the 19th century, eclipsing 2014, which previously held the record. The vast majority of scientists say human activities are to blame.
Despite accumulating evidence, however, there's still widespread skepticism in the U.S. about whether climate change is real. About a third of Americans say it isn't a serious threat, and many Republican lawmakers are skeptical.
'Evidence Is Overwhelming'
But 97 percent of climate scientists say the problem is urgent, according to a 2014 report by the world's largest scientific organization, which warned that the world was running out of time to deal with climate change.
"The evidence is overwhelming: Levels of greenhouse gases in the atmo sphere are rising," said the report, by the American Association for the Advancement of Science. "Temperatures are going up. Springs are arriving earlier. Ice sheets are melting. Sea level is rising. The patterns of rainfall and drought are changing. Heat waves are getting worse."
How did we get into this situation? Scientists say the burning of fossil fuels like oil and coal--mostly from cars and power plants--has caused a buildup of carbon dioxide and other gases that trap heat in the atmosphere. There are other sources too: Cows raised for meat or dairy production, for example, emit methane gas during digestion.
These invisible gases let sunlight through but prevent some of the resulting heat from radiating back out to space. Because they behave like the panes in a greenhouse, they're called greenhouse gases, and their influence on Earth's temperature is called the greenhouse effect. The higher the concentration of greenhouse gases, the warmer the planet gets.
The level of carbon dioxide, the main greenhouse gas, is up 41 percent since the Industrial Revolution in the early 19th century. If current trends continue, it could double in a few decades. Already, the planet has warmed 1.4 degrees Fahrenheit since the 1800s.
That may not sound like much, but many scientists see links between warmer global temperatures and more severe weather. For example, they say the prolonged drought in California has been intensified by climate change. And one of the most worrisome effects may be the melting of much of the Earth's ice in the polar regions, which is likely to raise sea levels and flood coastal regions.
Ironically, some of the countries that have contributed the least to the planet's warming---because they're poor and have fewer cars and power plants--are among those suffering most from the effects.
In Mali, climate change has raised temperatures and sharply reduced rainfall. With more than 80 percent of the population dependent on agriculture for survival, the lack of rain seriously threatens food supplies.
"In Mali, we are facing droughts and a coming desertification; we have a rainy season which went from a six-month duration to a month and a half in just a few years," says Mai'ga Sina Damba, a former government minister. "So climate change is a daily life issue for us."
With an annual per capita income of $660 last year and more than 43 percent of its population living in poverty, Malians don't have the tools to adapt to their changing environment.
"I saw with my own eyes the River Niger vanish into the sands, as the months went by," says Mali's president, Ibrahim Boubacar Keita. The Niger River is the third longest in Africa, and it supports 112 million people in...