ScienceMade Influence Blog
By Esha Mishra
Sea level rise is one of the most critical and dangerous consequences of climate change. When humans pollute the environment with greenhouse gases, such as carbon dioxide and methane, these gases prevent heat from escaping into the atmosphere due to their unique chemical structures and consequently increase temperatures on Earth. Therefore, seawater becomes less dense and expands through a process called thermal expansion, causing sea levels to rise.
From 1971 through the early 20th century, heat expansion and melting were reported to contribute approximately the same amount to sea level rise; however, in recent years, melting mountain glaciers and ice sheets have greatly accelerated this rate. According to a 2019 climate summary by the National oceanic and Atmospheric Administration (NOAA), Antarctica lost about 51 billion tons of ice per year between 1992 and 2001, and this quadrupled to 199 billion tons of ice per year from 2012 to 2016. Similarly, the Greenland Ice Sheet has lost significantly more ice between 2012 and 2016 compared to the late 20th century. This past decade, the NOAA found sea level rise nearly doubled due to thermal expansion, and as the Earth continues to warm, scientists predict that this melting will only increase.
In the twenty-first century, global sea levels are projected to rise between two to seven feet. The true increase depends on factors including the rate of future carbon dioxide emissions, global warming, as well as glacier and ice sheet melting. For example, sea level rise acceleration in the 1990s coincided with increased glacier and ice sheet melting. Yet, as human beings continue to pump greenhouse gases into the atmosphere, it’s uncertain whether that acceleration will continue or if internal glacier and ice sheet dynamics will lead to faster periods of melting interrupted by slower periods.
Understanding where and when this rise will take place will help scientists with coastal planning (planning for increased flooding and coastal damage). However, when studying coastal elevation, scientists found that many of the world’s coastlines were much lower than expected, meaning sea level rise could damage the homes of hundreds of millions of more people than previously anticipated.
Although sea level rise affects and will affect a majority of countries, countries in Asia, specifically China, Bangladesh, India, Vietnam, Indonesia, and Thailand, will feel the largest impact. According to a 2019 study, these six nations make up about 75 percent of the 300 million people on land who will be below average coastal flood levels by 2050. As sea levels continue to rise, a lot of land will be permanently lost to the ocean. Approximately 151 million people from those six countries live on land that will be gone by 2100.
Residents of small island states are posed to face devastating losses as well. A majority of people in the Marshall Islands and the Maldives live in high-tide areas which could be covered by water in the next eighty years. Yet even before their land is flooded, residents will face saltwater intrusion into their freshwater supplies and frequent flooding; beyond permanent loss of land, 360 million people around the world now live on land that will likely face annual flooding, bringing the number of people on highly vulnerable land to half a billion people.
Unfortunately, during this century, major flooding and dislocation due to sea level rise could disrupt economies and cause severe humanitarian crises around the world. A significant, immediate decrease to global emissions would reasonably reduce the threat posed by rising sea levels in this century. This decrease in global emissions would lessen the total number of people threatened by flooding and permanent inundation by 20 million. If governments hope to limit the future impact of sea level rise, they will protect high risk areas. It’s important to understand that sea level rise is not a faraway danger. It’s consequences are here and in order to protect ourselves and future generations, today’s governments and communities must take necessary measures against climate change.
Cover image is in the public domain.
In-text NASA Photo by Maria-José Viñas.