Unprecedented heat waves swept across the globe in 2017, leading to droughts, wildfires and even deaths. Australia started the year with temperatures near 50 degrees Celsius (122 Fahrenheit), the "Lucifer" heat wave brought the mercury above 40 degrees Celsius throughout Southern Europe in July and August and scorching heat hit India's most vulnerable people. Get ready for next summer...

Earlier this year, scientists realized that coral bleaching in Australia's Great Barrier Reef was worse than first thought. In some parts of the UNESCO World Heritage site, up to 70 percent of the coral has already been killed. By 2050, scientists have warned 90 percent of the reef could disappear. Rising sea temperatures and ocean acidification are the main culprits.

Armed conflicts are pushing millions of people to leave their homes or live in terribly precarious situations — and climate change is making it worse. A lack of natural resources increases the risk of conflict and makes life even harder for refugees. South Sudanese families, for instance, are escaping to neighboring countries like Uganda and Kenya — countries already suffering from drought.

From New Zealand to Spain, from California to even Greenland: the world has seen a nonstop year of wildfires. Global warming has been blamed for the increased fire risk, and in some countries that risk has turned into reality. Wildfires engulfed large areas of Europe's Iberian Peninsula, causing death and destruction, while firefighters in California have had no rest for more than six months.

Hurricanes Maria and Irma, which hit the Caribbean region in August and September, were two of the year's most damaging weather events. The list of deadly storms also included Ophelia in Ireland, Harvey and Nate in Central America and the US, and Xavier and Sebastian in Germany. Warming of the ocean surface has led to more evaporation, and that water may help fuel thunderstorms and hurricanes.

In July, one of the largest icebergs ever recorded separated from the Larsen C ice shelf — one of Antarctica's biggest — reducing its area by more than 12 percent. While calving icebergs in the Antarctic are part of a natural cycle, scientists have linked the retreat of several Antarctic ice shelves to global warming and are closely monitoring potential long-term effects.

Deteriorating air quality causes thousands of deaths around the world every year. India's capital, New Delhi, is one of the world's most polluted cities. In November, large parts of northern India and Pakistan were engulfed by a blanket of thick smog carrying harmful particulate matter. Schools were forced to close, and hospitals were full of people with respiratory problems.

The high levels of carbon dioxide in the atmosphere represent a major threat for our oceans, already in danger due to plastic pollution, overfishing and warming waters. Ocean acidification could make these waters — covering more than two-thirds of our planet's surface — a hostile environment for sea creatures. And without marine animals, entire ocean ecosystems are at risk.

Superstorms often trigger flash floods and mudslides. In late December, more than 230 people were killed when a storm hit the Philippines' second-largest island of Mindanao, a tragedy exacerbated by years of deforestation. In 2017, severe floods also hit countries such as Vietnam, Peru and Sierra Leone. European countries, including Greece and Germany, also felt the damaging effects of heavy rain.