Hurricanes Are Sweeping The Atlantic. What’s The Role Of Climate Change?



In this GOES-16 geocolor satellite image taken Thursday, the eye of Hurricane Irma (left) is just north of the island of Hispaniola, with Hurricane Jose (right) in the Atlantic Ocean.
NOAA/AP

 

Hurricane Irma is hovering somewhere between being the most- and second-most powerful hurricane recorded in the Atlantic. It follows Harvey, which dumped trillions of gallons of water on South Texas. And now, Hurricane Jose is falling into step behind Irma, and gathering strength.

Is this what climate change scientists predicted?

In a word, yes. Climate scientists such as Michael Mann at Penn State says, “The science is now fairly clear that climate change will make stronger storms stronger.” Or wetter.

Scientists are quick to point out that Harvey and Irma would have been big storms before the atmosphere and oceans started warming dramatically about 75 years ago. But now storms are apt to grow bigger. That’s because the oceans and atmosphere are, on average, warmer now than they used to be. And heat is the fuel that takes garden-variety storms and supercharges them.

The National Oceanic and Atmospheric Administration predicted that the Atlantic hurricane season this year would be big. It said the most likely scenario would be five to nine hurricanes and three to five major hurricanes, which is above the long-term average.

Some of its reasoning is based on climate change. The eastern tropical Atlantic Ocean is the fuel tank of hurricanes, if you will, and big parts of the sea surface have been between 0.5 and 1 degree Celsius warmer than average this summer. Now, the Atlantic goes through normal cycles of warming and cooling that have nothing to do with climate change, such as in response to the El Nino and La Nina weather cycles. But this year neither cycle is active.

And whether or not Irma was emboldened by climate change, what’s more telling are hurricane trends. Big hurricanes in the Pacific as well as the Atlantic appear to be happening more often and are packing more punch than normal.


This composite image shows Hurricane Irma’s path as it moved into the warm waters of the western Atlantic. Sea surface temperatures are high this year.
NASA/NOAA

Climate scientist Kevin Trenberth from the National Center for Atmospheric Research explains: “Previous very active (hurricane) years were 2005 and 2010,” he says, and along with 2017, they experienced warm Atlantic Ocean temperatures. “So this sets the stage. So the overall trend is global warming from human activities.”

It’s worth noting that there are other things that made Irma big that have no clear association with climate change. Vertical wind shear in the hurricane “nursery” region of the Atlantic are weak this year. Strong wind shear at the right altitude can in essence “behead” a hurricane as it forms, so Irma has free rein to build. There’s also a long-term cycle in the Atlantic — the Atlantic Multi-Decadel Oscillation — that affects hurricane-forming conditions. Since 1995, the AMO is in the “on” position for good hurricane conditions, and in fact the period since then has been quite active for storms and hurricanes.

So, as with Harvey, these superstorms have always happened due to natural causes, but the underlying conditions in the oceans and atmosphere have primed the pump. You don’t need much effort now to turn a trickle into a gusher.

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Sea Levels Will Rise Faster Than Ever


 

sea-level-rise

Scientific research indicates sea levels worldwide have been rising at a rate of 0.14 inches (3.5 millimeters) per year since the early 1990s. The trend, linked to global warming, puts thousands of coastal cities, like Venice, Italy, (seen here during a historic flood in 2008), and even whole islands at risk of being claimed by the ocean. Photograph by Andrea Pattero/AFP/Getty Images (National Geographic)

By Scott Waldman, ClimateWire on November 8, 2016

Source: Scientific American The Atlantic coast will be one of the hardest hit regions

Sea levels across the globe will rise faster than at any time throughout human history if the Earth’s warming continues beyond 2 degrees Celsius.

The Atlantic coast of North America will be one of the worst-hit areas as melting glaciers cause the sea level to rise over the next century, a new study published yesterday in the Proceedings of the National Academy of Sciences finds.

However, that rise is not expected to be uniform, as gravity and the movement of the ocean will play a role in how the water is distributed, and some areas will be hit worse than others. New York and other cities along the East Coast could see seas rise by more than 3 feet by the end of the century if the Earth warms by 4 or 5 degrees beyond pre-industrial levels.

If the rate of carbon emissions continues unabated, the authors said, the globe would warm by 2 degrees and cause significant sea-level rise by 2040. It would be worse along the East Coast of North America and Norway, which are expected to experience a sea-level rise of about a foot. The relative speed of the sea’s rise means many areas won’t have time to adapt, researchers found. And from there, warming would accelerate even faster.

“The coastal communities of rapidly expanding cities in the developing world and vulnerable tropical coastal ecosystems will have a very limited time to adapt to sea-level rises after the ‘2 degrees Celsius’ threshold is likely to be reached,” said Svetlana Jevrejeva, a researcher at the National Oceanography Centre in Liverpool, England, and lead author of the study.

The sea-level rise comes as the Earth’s record-breaking warmth is expected to become the “new normal,” according to another study published this week in the Bulletin of the American Meteorological Society. While 2015 was the hottest year on record, it could be the average within the next decade if carbon emissions continue to rise at their current rate, it found. And even if countries take action to limit carbon dioxide, humanity may have already locked in the increased warmth by 2040.

But limiting emissions now will mean some of the regions of the globe are not locked in for the new levels of warmth, and that they can still have significant variability.

“It gives us hope to know that if we act quickly to reduce greenhouse gases, seasonal extremes might never enter a new normal state in the 21st century at regional levels for the Southern Hemisphere summer and Northern Hemisphere winter,” said Sophie Lewis, a researcher at the Australian National University.

Millions of urban dwellers at risk

Nations that signed the Paris Agreement limiting warming to a maximum of 2 degrees are meeting this week in Morocco to put the accord into motion. Meanwhile, the United Nations has already cautioned that the emission targets countries voluntarily set may not be strict enough to meet the 2-degree goal.

Two degrees of warming is expected to cause an average global sea-level rise of 8 inches, but virtually all coastal areas will see more of a rise, Jevrejeva found. If warming exceeds 2 degrees by 2100, as some climate scientists worry it might, about 80 percent of the global coastline could experience a rise in sea levels of 6 feet. Such a rapid rise in sea levels is unprecedented since the dawn of the Bronze Age about 5,000 years ago, according to the study.

The research takes further the potential for sea-level rise posed by the Intergovernmental Panel on Climate Change, which argued that sea-level rise of 11 to 38 inches is possible by 2100. Many climate scientists have since claimed that estimate is too conservative.

Absent a concerted effort to limit warming, cities and island nations across the globe are at risk, researchers found.

“Coastal communities, notably rapidly expanding cities in the developing world; small island states; United Nations Educational, Scientific and Cultural Organization Cultural World Heritage sites; and vulnerable tropical coastal ecosystems will have a very limited time after mid-century to adapt to these rises,” they wrote.

The rise for New York is predicated on a warming of 5 degrees by 2100, which some researchers have contested may be too high. But at the upper scale of that level of warming, tens of millions of people around the world would be displaced. That includes “2.5 million living in low-lying areas of Miami; 2.1 million in Guangzhou [in China]; 1.8 million in Mumbai; and more than 1 million each in Osaka [in Japan], Tokyo, New Orleans, New York, and [Vietnam’s] Ho Chi Minh City,” researchers contended.

The study is part of a growing body of research that looks for possible scenarios that involve the potential for catastrophic sea-level rise, but more attention should be paid to the loss of land ice, as well, said Tad Pfeffer, a glaciologist at the University of Colorado, Boulder. While researchers typically focus on the loss of glaciers in Antarctica and Greenland, the loss of land ice in other spots across the globe is now contributing to sea-level rise at almost the same rate as the Arctic’s melting ice, he said. It’s the full scope of the current glacial loss that concerns political leaders and policymakers because it has already presented a pressing need to be addressed, he said.

“This near-term time scale is the time of greatest concern to decision makers,” he said. “Research that reaches out to 2100 and beyond is scientifically exciting, but really of secondary importance to the people who are trying to make sense of the science for decision-making.”

Reprinted from ClimateWire with permission from E&E News. E&E provides daily coverage of essential energy and environmental news at www.eenews.net.

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