Increasingly, headlines spotlight weather and climate events – most of which are bad news. In the last week of September, Hurricane Helene received her fair share of media attention. Hurricane Milton got his turn with TV and online coverage Oct. 1 – 10.
Now, a month into autumn, tropical cyclone season is on its downhill slide (hopefully), in both frequency and intensity. In recent years, hurricanes are becoming meaner and more common. Scientists increasingly believe that climate change creates the personalities that modern hurricanes appear to adopt. But one question remains: Why do hurricanes bring more rain in a warmer climate?
The Environmental Defense Fund answers that: “Evaporation intensifies as temperatures rise. So does the transfer of heat from oceans to air. As the storms travel across warm oceans, they pull in more water vapor and heat. That means stronger wind, heavier rainfall, more flooding when the storms hit land.”
Greenhouse gases (GHGs) are naturally present in Earth’s atmosphere. But human activity increases their accumulation. Thus, the GHGs in the atmosphere are boosted, altering Earth’s climate. Thus we observe shifts in precipitation patterns of both snow and rainfall, and rising temperatures, both for ocean surfaces and atmosphere. Thrown into that recipe are major heatwaves and floods. Here GHG emissions take center stage.
The greatest sources of GHGs are carbon dioxide (CO2) and methane. Potency of GHGs is largely determined by their ability to trap incoming solar radiation as well as how long they last in the atmosphere. Climate scientists generally agree that methane may last in the atmosphere for decades, while CO2 may last for centuries. Concentrate more on CO2.
According to the U.S. EPA, CO2 is the primary GHG emitted through human activities. In 2022, CO2 accounted for 80% of all GHG emissions from human activities in the nation. Atmospheric CO2 is part of Earth’s carbon cycle – the natural circulation of this element among the atmosphere, oceans, soil, plants and animals. Human activities alter carbon cycles by increasing atmospheric CO2 and by influencing the ability of natural “sinks” (like forests and soils) to remove and store CO2 from air.
A carbon sink is commonly defined as a forest, ocean or other natural environment viewed in terms of its ability to absorb atmospheric CO2.
While CO2 emissions come from many different natural sources, human-related emissions have been responsible for increases occurring in atmosphere since the Industrial Revolution. The UK was the world’s largest CO2 emitter in 1850. In 2022 (the year with the latest available data), China was the biggest CO2 emitter. However, the U.S. has the highest emission per person – about 13,000 metric tons, according to World Resources Institute.
Earth’s biosphere is commonly defined as being the top two feet of its crust and all the air above it. Unrefined petroleum is pumped to the surface, from as far as thousands of feet below. Most crude oil is refined into fuel – primarily diesel and gasoline. When those fuel sources mix with air and combust, end products are CO2 and water vapor, now situated in our atmosphere. The result: immeasurably large amounts of carbon (in the form of CO2) shunted into the gaseous layers blanketing our planet.
GHGs behave like greenhouse ceilings. They absorb the sun’s heat radiating from the earth’s surface. Such heat is trapped in the atmosphere, unable to escape into space. GHGs effectively keep Earth’s temperature warmer than it would otherwise be, indirectly supporting life on Earth. Which is a good thing.
But since 1850, humankind has been crafting too much of this good thing. Warmer than it would otherwise be is one way to define climate change. How does climate change strengthen hurricanes?
According to the National Oceanic and Atmospheric Administration (NOAA), increased sea surface temperatures can make storm surges – common in hurricanes – worse. Oceans respond to changes in temperature by expanding or contracting. Ocean surfaces absorb heat from air, causing surface water molecules to heat up and expand.
Averaged over all of the world’s oceans, sea level has risen at a rate of roughly 0.6 inch per decade since 1880. The rate of increase accelerated in recent years to more than one inch per decade.
Climatologists explain this scenario further: “Warmer oceans generate and sustain more intense hurricanes. Ongoing monitoring of sea surface temperature (SST) supplied evidence that the world’s oceans warmed 0.9º F between 1970 and 2005. Envision this monitoring by thinking of an oven meat thermometer measuring how done the turkey is. Because hurricanes rely on warm water to release heat into the upper atmosphere and create spiraling winds, any additional energy can result in increased intensity.”
More storm vaporized-sea water means more heat released into the upper atmosphere. That in turn lowers the pressure, which causes ocean’s surface winds to spiral inward, picking up speed – like the reverse of water going down a bathtub drain.
Until recently, few scientists believed that climate change and hurricane activity were correlated. They believed hurricanes were subject to a separate cycle of oceanic and atmospheric activity that shifted every 25 years or so. Now increased evidence strongly suggests that hurricane intensity is directly linked to rising global temperatures.
Since 1970, climatologists have noted gradual warming of the oceans. Most attribute this warming to increased atmospheric GHG concentration. Scientists have noted that the 0.9º rise in global SST between 1970 and 2005 resulted in a 4% increase in atmospheric water vapor. Increased water vapor helps produce more powerful hurricanes.
Leave A Comment