Hurricane Irma recently hit Florida, rewriting history books as the most powerful Atlantic hurricane on record, with winds reaching velocities as high as 298km/h. But with hurricanes, it isn’t only wind that we should be worrying about – it’s water.
Since the 1960s, 88% of deaths in the United States during tropical storms and hurricanes have been caused by water, while only 8% of deaths can be directly attributed to wind. Of all casualties, almost half are caused by storm surges.
Physically, storm surges act just like a tsunami. They occur when winds emanating from the swirling arms of hurricanes blow water towards the shore. During Katrina, those waves reached 8.5 metres in height, even though Katrina itself only made landfall as a Category 3 storm.
Images we remember of Katrina’s aftermath in New Orleans aren’t of windswept homes and torn up trees; they’re of a city submerged in water.
In short bursts over four days this August, Harvey dropped an unprecedented 1.32 metres of rainfall outside Austin, Texas. In comparison, during one whole year at Trinity College, only 0.73m of rain precipitates. American cities are largely designed as concrete sprawls with few green spaces in sight, meaning that water has little chance to seep into the ground.
In addition, due to its flat geography, flood waters will be slow to leave Austin. Cities being hit by Harvey and Irma just aren’t geographically equipped to deal with the massive amounts of rainfall and storm surges flooding the area.
Communities as far north as Georgia and South Carolina, where towns situated close to the tide level have far less experience in dealing with natural disasters than those in Texas and Louisiana, have this week been issued evacuation warnings ahead of predicted storm surges.
Ultimately, our own human habits of consumption and fossil fuel reliance are fuelling rapid climate change. They may leave us too slow to adapt to the future scale of tropical storms. Due to human activity since the start of the Industrial Revolution, our Earth has already warmed over 1 degree Celsius.
This is irreversible, the effects of it are here to stay, and they are getting worse. 1 degree of warming has happened, despite one of the 2015 Paris Accord’s goals being to limit warming to 1.5 degrees.
Because of the thermal inertia of the ocean, when we emit carbon dioxide into the atmosphere its effects are not felt immediately. Like water in a pan over a burning flame, it will take time to boil.
Scientists tell us it will take about 40 years for today’s emissions to take their effect on our climate and weather systems, a phenomenon known as climate lag. Crucially, this means that even if we were to stop emitting carbon tonight, the Earth will still warm a further 0.6°C.
Human activity is already contributing to a catastrophically heightened risk of storm surges, where the increased release of greenhouse gases has transported melted ice sheets to the literal doorsteps of many a coastal condo.
According to the National Oceanic and Atmospheric Administration in the USA (NOAA), every area affected by Hurricane Harvey experienced more than eight inches of increased local sea levels between 1960 and 2015. Additionally, physics tells us that for every degree in temperature rise, the air can hold 7% more water.
This means that tropical storms are able to take up more of the ocean’s water than ever before, only to dump it back down once the storms reach land. Until we can adequately deal with storm surges and rainwater floods in all kinds of human habitats, and not just those where hurricanes have always hit, we must learn to accept that events like those of the past weeks are here to stay.
As global temperatures continue to rise, damage from the seas and skies will only become more severe. Events of the past weeks have broken both records and homes, but the Earth has only warmed 1 degree thus far. A further 0.6 degrees are already locked in, and with it the inevitable peril brought by more powerful storms.
If the United Nations wishes to make good on its goal to limit global warming to under 2°C, the time to act is now. In order to reach this target by 2035, 20 years after it was set, we must cut global emissions by 0.5% per month, starting now.
If this cut started in 1995, 20 years before it was set, it would only have required a 0.1% per month decrease. The longer we delay our independence from greenhouse gases, the greater the effort it will require when we finally act. The longer we wait, the more Harveys we will have, and the worse our Irmas we will get.