Melting glaciers and ice sheets are causing sea level rise, causing coastal extreme weather events to become more severe while the ocean is warmer, more acidic, and less productive, according to a major new report by the United Nations.
The report, released Wednesday by the U.N.’s Intergovernmental Panel on Climate Change, focuses on global warming’s effects on the ocean and the cryosphere — the frozen parts of the planet — which are necessary for food and water, energy, trade, transportation, recreation, and tourism.
“The world’s ocean and cryosphere have been ‘taking the heat’ from climate change for decades, and consequences for nature and humanity are sweeping and severe,” said Ko Barrett, vice chairwoman of the IPCC. “The rapid changes to the ocean and the frozen parts of our planet are forcing people from coastal cities to remote Arctic communities to fundamentally alter their ways of life.”
Some major findings of the report, produced by more than 100 authors from 36 countries, include:
- Sea levels are currently rising more than twice as fast, 3.6 millimeters per year, as they did in the 20th century. Sea level rise could reach around 30 to 60 centimeters by 2100 even if greenhouse gas emissions are sharply reduced and global warming is limited to “well below” 2 degrees Celsius, the goal of the Paris agreement. This is happening due to the melting of ice sheets in Greenland and Antarctica, in addition to melting of glaciers and the expansion of warmer ocean water.
- The Greenland Ice Sheet has lost mass at an average rate of 278 billion tons per year between 2006 and 2015, while the Antarctica Ice Sheet during the same period has melted at a rate of about 155 billion tons annually.
- Oceans are becoming more acidic and losing oxygen, having absorbed between 20 to 30% of total CO2 emissions since the 1980s, affecting the distribution and abundance of marine life in coastal areas. Many regions have lost fish and shellfish stocks, leading to reduced fisheries catches.
- Marine heatwaves, which can cause large-scale deaths of corals and other ocean organisms, have doubled in frequency since 1982 and are increasing in intensity. Their frequency will be 20 times to 50 times higher, depending on how much the world warms. The world has already warmed 1 degrees Celsius above the pre-industrial level due to greenhouse gas emissions.
“If we reduce emissions sharply, consequences for people and their livelihoods will still be challenging, but potentially more manageable for those who are most vulnerable,” said Hoesung Lee, chairman of the IPCC.
The findings build on a larger report released by the same U.N. climate panel last year that concluded world energy use must undergo a “rapid and far-reaching” transition by 2030 to prevent a 1.5-degree rise in the global temperature, the threshold required to avoid the worst consequences of global warming. That report said the world must reach net-zero emissions by 2050, inspiring Democratic presidential candidates and members of Congress to offer pledges to reach that target.
The world’s largest emitters, including the United States and China, did not commit to significant additional policies to meet those goals at a U.N. Climate Summit this week.
A second report released by the IPCC in August found that food production, along with land and forest management, have contributed significantly to global climate change, requiring a change in behaviors, including recommending people eat less meat in favor of more balanced diets featuring plant-based foods.
