Global warming may make tropical cyclones more intense

The predictions of scientists are also confirmed by computer models

The predictions of scientists are also confirmed by computer models

Tropical cyclones’ intensity should increase as the climate warms in response to human emissions of greenhouse gases. This is the outcome of a study conducted by scientists at Columbia University, NY and published in the journal Science, and even though this trend hasn’t become evident yet, it eventually will, they say. They examined a wide range of published analyses of tropical cyclone data and computer modeling and interpreted future and recent historical trends by using the theory of potential intensity which predicts the maximum intensity that tropical cyclones could reach in a given local environment.

Although there are various factors contributing to a tropical cyclone's intensity, the most basic is that as the climate warms, the tropical ocean surface heats up more than the atmosphere above it, increasing the temperature differential on which storms feed. Model simulations suggest that this difference should increase as the climate and sea surface temperatures warm, and that tropical storm strength should increase with it.

The role of aerosols

According to climate model simulations, it seems that the uncontrolled use of aerosols during the last century has cancelled out the effects of planet-warming greenhouse gas emissions when it came to tropical storm intensity. A product of the burning of fossil fuels and wood, these tiny particles cool the climate by absorbing and reflecting sunlight. But due to the ongoing fight against air pollution, levels of man-made aerosols in the atmosphere began to decline, while at the same time, greenhouse gas concentrations continued to rise. So, in the absence of strong reductions in greenhouse gas emissions, future greenhouse gas forcing of potential intensity will increasingly dominate over aerosol forcing, leading to substantially larger increases in tropical cyclone intensities. Computer models provide new calculations of the cancelling effects of aerosols and greenhouse gases on tropical cyclones worldwide.

"The fact that global warming's fingerprints don't yet jump out at us when we look at hurricanes isn't surprising – it’s what current science tells us we should expect," said lead author Adam Sobel, a professor at Columbia University’s Lamont-Doherty Earth Observatory and School of Engineering. "The same science tells us that those fingerprints will show up eventually in more ultra-powerful storms." 

Changes in potential intensity in the Northern and Southern Hemispheres as reflected in the CMIP5 computer model. Black is historical data, blue is the influence of aerosols only, red is the influence of greenhouse gases only, and green shows the difference between the historical data and the influence of aerosols. Chart: Sobel et al., 2016 

Source: The Earth Institute – Columbia News