The danger bell for a rapid increase in extreme phenomena during this winter, due to the “El Niño” phenomenon, is sounded by the NASA.

The analysis by NASA’s environmental team calls for flooding in coastal areas and cities due to a sharp rise in sea levels, which will be amplified by the effects of El Niño.

According to NASA, if a strong is developed El Niño this winter, cities along America’s west coast could see an increase in the frequency of high-tide flooding, leaving roads submerged and underground and single-story buildings at serious risk.

El Niño is a periodic climate phenomenon characterized by higher than normal sea levels and warmer than average ocean temperatures along the equatorial Pacific. These conditions can spread poleward along its western coasts America. El Niño, which is still developing this year, may bring more rain than usual to the US Southwest and drought to western Pacific countries such as Indonesia. These effects usually occur from January to March.

NASA’s analysis finds that a strong El Niño could lead to as many as five instances of a type of flood called a 10-year flood event this winter in cities like Seattle and San Diego. Places like La Libertad and Baltra in Ecuador could experience up to three of these ten-year floods this winter. This type of flooding does not usually occur along the west coast of America except during El Niño years. The researchers note that by the 2030s, rising seas and climate change could result in these cities experiencing similar numbers of 10-year floods annually, without El Niño’s input.

“I’m a little surprised that the analysis found that these 10-year events could become commonplace so quickly,” said Phil Thompson, an oceanographer at the University of Hawaii and a member of NASA’s Sea Level Change Science Team, who conducted the analysis. “I would think maybe until 2040s or 2050s“, he added.

Decadal floods are those that have a one in 10 chance of occurring in any given year. They are a measure of how high local sea levels are becoming: The extent of flooding in a particular city or community depends on several factors, including an area’s topography and the location of homes and infrastructure in relation to the ocean. Decade flooding can result in what the National Oceanic and Atmospheric Administration classifies as moderate flooding, with flooding of roads and buildings and the potential need to evacuate people or move items to higher ground.

NASA’s analysis of coastal flooding finds that by the 2030s, during strong El Niño years, cities on America’s West Coast could see as many as 10 of these 10-year flood events. By the 2050s, strong El Niños may lead to up to 40 instances of these events in a given year.

How is sea level rise progressing?

Water expands as it warms, so sea levels tend to be higher in places with warmer water. Researchers and meteorologists monitor ocean temperatures as well as water levels to track the formation and development of an El Niño.

“Climate change is already shifting sea level baselines along coastlines around the world,” said Ben Hamlington, a sea level researcher at NASA’s Jet Propulsion Laboratory in Southern California and head of the agency’s sea level change science team.

Sea levels are rising in response to planetary warming, as Earth’s atmosphere and oceans warm and ice sheets and shelves melt. This has already increased the number of high tide or flood nuisance days that coastal cities experience throughout the year. Events such as El Niño and storms, which temporarily raise sea levels, exacerbate these effects.

“As climate change accelerates, some cities will see floods five to ten times more often. SWOT will monitor these changes to ensure that coastal communities are not caught off guard,” said Nadya Vinogradova Shiffer, SWOT program scientist and director of the ocean physics program at NASA Headquarters in Washington.