Climate

In Washington D.C., Record-Breaking Floods Could Happen Every Year

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Though more than half the Republican Party still denies the reality of climate change, the evidence may soon be lapping at their feet. A report (PDF) from Climate Central says Washington, D.C. is going to face much more severe flooding in coming decades, submerging homes, roads, military facilities, and even the iconic National Mall on a regular basis.

The largest flood ever recorded in Washington, D.C. occurred during heavy rains in 1941. It reached 7.9 feet over the high tide line. But 2003’s Hurricane Isabel came close at 7.1 feet, flooding streets and parts of the Navy Yard, and necessitating the rescue of several people from cars. In the most dire scenario, floods of that size could be happening every year by 2100. In that same scenario, the report says, “at least one flood reaching above 10 feet would be close to certain this century.”

The report is combined with Climate Central’s Surging Seas risk finder tool. First launched in 2012, it allows people to find out how sea level rise will affect their towns and communities. It can show what flooding caused by anywhere from one to 10 feet of rise would look like, with overlays to show the population density, social vulnerability, and other factors in affected areas.

The Climate Central report looked at the National Oceanic and Atmospheric Administration’s slow, medium, and fast scenarios of sea level rise. That would mean either 1.6 feet, 3.9 feet, or 6.6 feet of rise from the starting point at 1992. The worst case includes the effects of accelerating, record ice loss occurring in the West Antarctic Ice Sheet, which is liable to increase sea level rise to rates upwards of 1 inch per year by 2100.

Sea level rise is one of the most obvious and direct effects of global warming, and it’s also likely to be economically catastrophic across the globe. It’s already making people relocate, and threatening hundreds of cultural heritage sites. Yet action to prepare for higher sea levels has been halting, and hampered by political opposition. Norfolk, Virginia is among the most vulnerable U.S. cities to flooding, but politicians there have struggled against climate change denial to take action.

Melting on both land and sea can cause precipitous feedback loops that affect regional warming and sea level rise. When reflective sea ice melts, it leaves behind darker ocean, which can absorb more heat that the ice did. This causes the ocean temperatures to rise, leading to more sea ice melting.

On land, the melting Arctic glacial ice flows into the ocean, which raises sea levels — it also, however, causes more ice to melt, at a faster and faster rate. A recent study in Greenland found that Greenland’s ice darker than it’s ever been recorded to be, which causes even more melting.

That complicated cycle makes it difficult to predict exactly how high sea levels will be in coming years. But what’s clear enough is that they will rise. And they will threaten coastal coastal communities.