Hurricane Damage in Florence: Climate Change Worsened the Situation

The floodwaters finally start to get away from hurricane Florence, a storm that has spilled more than 35 inches of rain in places and more than 10 trillion gallons in North Carolina, South Carolina and Virginia. The 1,000-year storm damaged thousands of structures, including toxic animal waste containment sites, which sent bacteria and hazardous chemicals into the water. At least 50 people have died in Florence and the damage estimated could reach $ 22 billion.

As a result of extreme weather events such as Florence, it is increasingly urgent to understand how climate change has affected results. On the one hand, climate change will never cause a single event. But there is more and more compelling scientific evidence that global warming is fueling even stronger storms like Florence, which in turn can cause more damage and destruction on Earth.

This is why climate scientists, partly to answer journalists' questions about the role of climate change in extreme weather events, have begun to devote more time and resources to developing the link.

Several months after hurricane Harvey, the massive storm that flooded Houston in 2017, researchers attributed 38% of the storm's record rainfall to global warming. This year, with Hurricane Florence, we have seen scientists trying to understand the influence of climate change much faster, almost in real time. And what they found is this: human activity has dramatically increased the amount of rain produced by the storm and expanded the extent of its floods. Here's how.

Climate change reinforces the basic ingredients of the destruction of a hurricane

The first component of a hurricane is hot water. Hurricanes need sea surface temperatures of 27 degrees Celsius (82 degrees Fahrenheit) or more to get enough energy to drive the storm. Warmer water areas can also intensify existing hurricanes as they pass.

Climate change has already raised the temperature of the world's oceans and lengthened the seasons when the waters are warm enough to withstand a hurricane. Although this does not necessarily change the frequency of hurricanes, it means that the storms that form are likely to be more severe and last longer.

The humidity of the warm sea surface then enters the atmosphere. Warmer temperatures mean that the air can retain more moisture. Each temperature increase in degrees Celsius means a 7% increase in the amount of water the air can hold. This increases the likelihood and severity of extreme precipitation events, including those that occur during hurricanes.

Heat and moisture then combine to charge wind and precipitation from a cyclone. "Hurricanes live and die depending on how much rain they produce," George Huffman, a meteorologist at NASA Goddard Space Flight Center, said last year.

Finally, climate change is driving sea levels around the world. This is due to melting ice on land flowing into the ocean, as well as to the expansion of the seawater when it warms up. The sea level in a given region may also increase as the land subsides, whether through natural erosion, groundwater depletion or coastal development.

So, when a storm is heading towards a coast, storm surges rise in power and move further inland, throwing water onto more properties and endangering further lives.

Here's what we understood up to here about Hurricane Florence

Last week, Axios announced that one in five houses struck by Florence had suffered damage exacerbated by rising sea levels. The First Street Foundation, a group studying sea-level rise, examined historical records, tide and river gauges, and aerial imagery to conduct their analysis.

The group told Axios that the storm surge of Hurricane Florence had flooded over 51,000 properties. A flooded property is defined as a property whose water floods at least 25% of its area.

And since sea levels have risen since 1970, Hurricane Florence has "significantly affected" more than 11,000 additional homes that would have been flooded if the sea had remained at its previous level. The US Army Corps of Engineers predicts that sea level will rise more than one foot on the coasts of North Carolina and South Carolina. If a comparable Florence storm were to occur, the number of houses affected would be doubled.

Regarding rainfall in Florence, another group of researchers estimated that it had spilled 50% more rain due to climate change. Kevin Reed, professor of atmospheric science at Stony Brook University, who helped gather the estimates, said his team had used a methodology similar to that used by scientists to measure human influence during past storms.

Reed said the precipitation forecasts made when Florence hit the coast held up well. "Our preliminary analysis shows that the predictions were relatively conclusive where the storm caused rainfall," he said. This means that estimates of man's influence on storm precipitation also hold up well, as they were built on forecasts.

But Reed acknowledged that trying to determine how much humanity is to blame while a storm is still going on mainly concerns trying to demonstrate the link with an enchanted audience. "The jury has not yet determined their usefulness," he said. For those who are on the way to the storm, it is essential to know where it will go, but it does not really help the evacuation efforts to know how much climate change is to blame.

However, to help the public understand that climate change is not a distant event, but a phenomenon that currently has consequences could help develop better planning and risk mitigation strategies in storm-prone areas. North Carolina sadly passed a law in 2012 banning the use of sea level rise projections in coastal planning, which relies on climate change. Linking the points between more violent storms and climate change could help states to develop better policies, or at least to tackle the most serious ones.

And there is still much work to be done to determine to what extent the destruction of Florence can be attributed to human activity. The researchers are still analyzing more general weather conditions and trying to understand why the storm slowed down when she arrived on land, which allowed her to pour a massive amount of rain on a relatively small area. Reed said his team was working on a more detailed study on the climate attribution for Hurricane Florence that he would submit for publication in a few months.