In coastal communities across the U.S., new data shows land that’s home to more than 260,000 Americans is at risk of increased flooding over the next 20 years. The number of people at risk worldwide is projected to grow five-fold by the end of the century if nations continue their current course of global greenhouse gas emissions, according to the Human Climate Horizons, a collaboration between the United Nations Development Programme and the Climate Impact Lab.

The new information shows increased coastal flooding this century will put over 70 million people around the globe in the path of expanding floodplains.

CBS News traveled to the world’s northernmost and fastest-warming community of Svalbard, Norway, because what scientists are learning there can help Americans understand the changes happening in the United States. As the Arctic warms, it adds to rising sea levels along our coasts and instability in the atmosphere that contributes to our extreme weather events.

“The effects of rising sea levels will put at risk decades of human development progress in densely populated coastal zones, which are home to one in seven people in the world,” said Pedro Conceição, director of UNDP’s Human Development Report Office.

The data finds the most extreme risks of lost land and critical infrastructure worldwide will be in Latin America, the Caribbean, the Pacific and small island states — including hundreds of highly populated cities like Rio de Janeiro, Brazil, and Sydney, Australia.

“These projections are not foregone conclusions; instead, they can be a catalyst for action,” said Hannah Hess, associate director at the Climate Impact Lab, a collaborative group of scientists and researchers who measures the real-world costs of climate change. “Swift and sustained action to reduce emissions will affect how quickly and how much coastal communities are impacted.”

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Areas of Focus: Climate Change
Climate Change
Climate change is an urgent global challenge. EPIC research is helping to assess its impacts, quantify its costs, and identify an efficient set of policies to reduce emissions and adapt...