Even if countries significantly curbed their emissions, the planet is marching toward sea level rise of a meter, and most of the East and West coasts in the U.S. will experience flooding that would normally take place once a century every year, scientists warn.
The U.N. Intergovernmental Panel on Climate Change (IPCC) reviewed the state of the world’s oceans and ice, ranging from ice sheets in the Arctic to mountaintop glaciers, and found many effects of climate change can no longer be avoided.
The report stressed the need for urgent action to reduce greenhouse gas emissions in order to address the effects that can still be managed.
“This report highlights the urgency of timely, ambitious, coordinated, and enduring action. What's at stake is the health of ecosystems, wildlife, and importantly the world we leave our children,” said Ko Barrett, vice chair of the IPCC and deputy assistant administrator for research at the National Oceanic and Atmospheric Administration.
“It’s the complete picture that’s surprising and frankly concerning about changes we’re already seeing from highest mountains to the bottom of the ocean and how these are kind of consistently being affected by human-caused warming,” she said.
The damage to the interconnected systems could lead to a future of serious sea level rise, as warming temperatures melt ice and promote more frequent and intense storms. On land, decreasing snowfall threatens to diminish the freshwater supply to the American West, drying the landscape and limiting the capacity of hydroelectric power — an important source of renewable energy in the region.
“Snow is good, yet we’ve got less snow. Snow arrives later, melts earlier and covers less ground,” said Heidi Steltzer, one of the lead authors of the report and a professor at Fort Lewis College in Colorado.
The report also warned about the repercussions of warming ocean temperatures. The world’s oceans have largely served as a buffer against global warming, absorbing carbon emissions and excess heat — but that capacity may be diminishing.
Since 1993, the rate of ocean warming has more than doubled, destabilizing massive ice sheets near Greenland and in the Antarctic.
“For decades the ocean has been acting like a sponge, absorbing carbon dioxide and heat to regulate the global temperature, but it can't keep up,” Barrett said.
The new report predicts 1 meter of sea level rise by 2300, but accelerated melting has the potential to lead to sea level rise of several meters within a few centuries. The changes already seen in Greenland and in the Antarctic “may be the onset of an irreversible ice sheet instability.”
“Sea level rise has accelerated and will accelerate further with of course major implications,” said Regine Hock, one of the study authors.
The combination of sea level rise and warming ocean temperatures will also lead to more severe and frequent storms.
“Indications are that with any degree of additional warming, events that occurred once per century in the past will occur every year by mid-century in many regions, increasing risks for many low-lying coastal cities and small islands," the report said.
Scientists are also worried about the high levels of carbon absorbed by the ocean.
Since the 1980s, the ocean has sucked in between 20 percent to 30 percent of human-caused carbon dioxide emissions. That absorption has lead to ocean acidification, harming coral reefs and ocean wildlife.
Paired with excess heat, the effects will be worse.
The ocean to date has taken up more than 90 percent of the excess heat globally. Scientists warned that if global emissions are not curbed, the ocean could take in five to seven times more heat. That heat burden could have consequences for marine life, as water’s temperature affects its ability to hold oxygen.