In the warm waters of the tropical Atlantic Ocean, things are starting to heat up. It’s almost the start of the hurricane season, and experts are predicting this year will be more active than usual.
There are six conditions that appear to govern when a hurricane will arise. First, the temperature for the top 50m of the water column has to be over 26 degrees Celsius. When the surface waters are this temperature, they make the air over the waters unstable enough to sustain convection and thunderstorms. Atmospheric conditions have to be correct as well, with the warm surface air rapidly getting colder as the altitude increases. This allows the release of the heat of condensation that powers the storm. High humidity is required, especially in the lower-to-mid troposphere; when there is a great deal of moisture in the atmosphere, conditions are more favorable for disturbances to develop. There also has to be low amounts of wind shear. Wind shear is the change in speed and direction of the wind over a short distance. High shear is disruptive to a storm’s circulation. Hurricanes generally need to form more than 550 km from the equator, allowing the Coriolis effect to deflect winds blowing towards the center and create a circulation. Last, a hurricane needs pre-existing disturbed weather. Only when all of these conditions are met is it possible for a hurricane to form.
In the average hurricane season, these conditions are met often enough to form 3-4 major storms. For this hurricane season, the National Oceanic and Atmospheric Administration (NOAA) is predicting anywhere from 8-14 major storms. The surface waters are even warmer than they were in the 2005 hurricane season, which spawned Katrina and Rita. In fact, the tropical surface waters are the warmest they have been since records started being kept in 1945. This year has the potential to be a very bad year if you live along the Gulf Coast or eastern seaboard of the United States, and the storms could even reach up into the Canadian Maritimes.
Interestingly enough, some scientists have predicted that 2010 may be the warmest year on record as well. It is starting to become clear that there is a causal link between global temperatures and hurricane activity.
Which brings us around to global climate change. Most scientists are in consensus that the Earth’s climate is changing, and that human activities are the source of the change. Global average temperatures are going up, but this heat is not distributed evenly. Only a small change here and there can have vast effects. The atmosphere is a chaotic system, which means small changes at the beginning can cause huge effects at the end. So it is not just the surface warming in the tropical waters that influences hurricane formation, but a wind that started a couple of thousand kilometers away along the coast of Morocco may be the disturbance that gives rise to a monster storm.
Climate and weather are very unpredictable. At best, we can recognize conditions that may give way to storms or other effects. We can never be certain. But as the Earth’s climate shifts around us, as more energy is added every year to the system, weather is bound to grow more unpredictable, and more dangerous. And the worst of it is that we now have the knowledge to realize that the destruction wreaked by a hurricane is, at least in part, our fault, largely through the burning of fossil fuels and the release of greenhouse gases.
Think about that the next time you start your car to drive to the convenience store.