Hurricanes and Global Warming, are they connected?

Hurricanes and Global Warming, are they connected?

 By: Vineeta Tawney

What is Hurricanes

A hurricane is a type of storm called a tropical cyclone, which forms over tropical or subtropical waters.

A tropical cyclone is a rotating low-pressure weather system that has organized thunderstorms but no fronts (a boundary separating two air masses of different densities). Tropical cyclones with maximum sustained surface winds of less than 39 miles per hour (mph) are called tropical depressions.

What is Global Warming?

Global warming is the slow increase in the average temperature of the earth’s atmosphere because an increased amount of the energy (heat) striking the earth from the sun is being trapped in the atmosphere and not radiated out into space.

The earth’s atmosphere has always acted like a greenhouse to capture the sun’s heat, ensuring that the earth has enjoyed temperatures that permitted the emergence of life forms as we know them, including humans.

Without our atmospheric greenhouse the earth would be very cold. Global warming, however, is the equivalent of a greenhouse with high efficiency reflective glass installed the wrong way around.

Two massive volcanic eruptions, one year after another placed so much black dust into the upper atmosphere that little sunlight could penetrate. Temperatures plummeted. Crops failed. People died of starvation and the Black Death started its march. As the dust slowly fell to earth, the sun was again able to warn the world and life returned to normal.

Hurricanes and Global Warming, are they connected?

Fig. 1

Global warming is adding more moisture to the atmosphere, providing more fuel for big storms like hurricanes. But tropical cyclones are extremely complicated. How much can we really link them to human-induced climate change? It depends on the link.

The key connection is that between sea surface temperatures and the power of hurricanes. Without going into technical details about the dynamics and thermodynamics involved in tropical storms and hurricanes the basic connection between the two is actually fairly simple: warm water, and the instability in the lower atmosphere that is created by it, is the energy source of hurricanes. This is why they only arise in the tropics and during the season when SSTs are highest.

SST is not the only influence on hurricane formation. Strong shear in atmospheric winds (that is, changes in wind strength and direction with height in the atmosphere above the surface), for example, inhibits development of the highly organized structure that is required for a hurricane to form. In the case of Atlantic hurricanes, the El Nino/Southern Oscillation tends to influence the vertical wind shear, and thus, in turn, the number of hurricanes that tend to form in a given year. Many other features of the process of hurricane development and strengthening, however, are closely linked to SST.

Model-based climate change detection/attribution studies have linked increasing tropical Atlantic SSTs to increasing greenhouse gases, but proposed links between increasing greenhouse gases and hurricane PDI or frequency has been based on statistical correlations. The statistical linkage of Atlantic hurricane PDI to Atlantic SST suggests at least the possibility of a large anthropogenic influence on Atlantic hurricanes. If this statistical relation between tropical Atlantic SSTs and hurricane activity is used to infer future changes in Atlantic hurricane activity, the implications are sobering: the large increases in tropical Atlantic SSTs projected for the late 21st century would imply very substantial increases in hurricane destructive potential–roughly a 300% increase in the PDI by 2100.

On the other hand, Swanson (2008) and others noted that Atlantic hurricane power dissipation is also well-correlated with other SST indices besides tropical Atlantic SST alone, and in particular with indices of Atlantic SST relative to tropical mean SST.

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>