Articles tagged as: climate
Increased warming from changing ocean currents has accelerated over the past 100 years and could ultimately affect climate patterns over much of the world, according to research by two Texas A&M University oceanographers.
Ping Chang and Benjamin Giese, professors in the Department of Oceanography at Texas A&M, are part of a team that analyzed ocean temperature and current data since 1900. Their work is part of a multinational team that included researchers from the Ocean University of China, NOAA, the University of Hawaii, the University of Colorado, the Woods Hole Oceanographic Institution, the University of Tokyo, the Ocean University of China and scientists in Germany and Australia. Results of the team’s study have been published in the journal Nature Climate Science.
The Texas A&M research team found that parts of the world’s oceans are warming at an accelerated rate, showing a global warming “signature” in the ocean. The warming trend in some parts of the oceans is twice as large as the global average, the researchers have discovered.
“Certain parts of the oceans are getting warmer much faster than others,” Giese explains, “and it shows that there are significant regional differences in warming. The difference is from 0.5 to more than 1.5 degrees, and while that may seem small, it is a large change compared with the historical data over the past 100 years.”
Chang says the rising temperatures are possibly attributed to ocean circulation changes, which are likely caused by changes in atmospheric circulation, especially in the winds over the oceans.
“If this trend continues,” he says, “it could have a potential impact on the occurrence of extreme climate events, such as winter storms, in these regions because the atmospheric circulation is affected by sea-surface temperatures. These changes in ocean circulation could also have an impact on marine ecosystems.”
They say that the most severely affected areas of rising ocean temperatures are off the coast of Australia, near the Philippines, the Gulf Stream from Florida to New England, the Brazil current and the Kuroshio current, which is similar to the Gulf Stream but located in the Pacific Ocean near Japan.
The two Texas A&M researchers say the rising temperatures would probably not affect conditions of an El Niño or La Niña event.
“It is difficult to determine how these changes will affect global weather patterns,” Chang explains, “and it is more likely that regional climate extremes will be affected by these rising temperatures.”
The warming trend could pose problems for sensitive marine areas, Giese notes.
“People in Australia are worried about it because it could have an impact on its Great Barrier Reef,” he notes. “Any rise in temperature might damage the sensitive ecosystems of the reef.” At 1,800 miles long, the Great Barrier Reef is so large it can be seen from space.
The team’s work was funded by the China National Key Basic Research Project, the Australian Climate Change Science Program, the Southeast Australia Climate Initiative, the Japanese Ministry of Education, Culture, Sports, Science and Technology, NOAA (National Oceanic and Atmospheric Administration) and the National Science Foundation.
About research at Texas A&M University: As one of the world’s leading research institutions, Texas A&M is in the vanguard in making significant contributions to the storehouse of knowledge, including that of science and technology. Research conducted at Texas A&M represents an annual investment of more than $630 million, which ranks third nationally for universities without a medical school, and underwrites approximately 3,500 sponsored projects. That research creates new knowledge that provides basic, fundamental and applied contributions resulting in many cases in economic benefits to the state, nation and world.
Tiny ocean organisms found off the Florida coast could provide huge clues about Earth’s past and climate change, according to research by a Texas A&M University oceanographer.
Matthew Schmidt, assistant professor of oceanography who specializes in ocean geochemistry, has conducted a study that provides evidence for the trigger of abrupt climate change in Earth’s recent past. His article, published recently in Paleoceanography, details how foraminifera – tiny single-celled organisms about the size of the head of a pen – that lived near the surface and on the bottom of the ocean give us clues about how the climate has changed since the end of the last ice age.
Schmidt collaborated with Jean Lynch-Stieglitz of the Georgia Institute of Technology to study foraminifera gathered from a sediment core recovered from the Florida Straits. Lynch-Stieglitz studied the benthic foraminifera, or those on the bottom of the ocean, that lived on the margins of the Florida Straits as a means to reconstruct past changes in ocean circulation.
Schmidt then analyzed the foraminifera that lived near the surface of the ocean to help determine past atmospheric circulation changes.
“The idea behind the study was to resolve the timing of atmospheric and oceanic circulation changes that occurred during an era known as the Younger Dryas, an abrupt cooling that occurred right as the world was coming out of the last ice age about 13,000 years ago,” Schmidt explained.
“The Younger Dryas is the period when the wooly mammoth and the saber tooth tiger go extinct. It’s a unique event because many of the Pleistocene megafauna that had made it through multiple ice ages in the past suddenly get wiped out. The question is what was different about the Younger Dryas?”
The foraminifera help Schmidt because they are surrounded by calcium carbonate shells, similar to seashells found on the beach, that lock in the clues as to the temperature and salinity of their surroundings. The foraminifera living close to the surface of the water give clues about the atmosphere, while those living on the bottom of the ocean reflect changes in ocean circulation.
“Key to our study is that both records come from the same core, so there’s no uncertainty as to the relative timing of when one changed relative to the other,” Schmidt said. “Most records of past climate variability will only tell you something about the atmosphere or the ocean, but not both.”
Scientists have long thought that the ocean’s conveyor belt circulation that cycles warm water through the Tropical Atlantic and the Florida Straits and then into the northern Atlantic Ocean was the driver for abrupt climate change during the last ice age. Schmidt and Lynch-Stieglitz’s findings seem to confirm that the North Atlantic’s conveyor belt circulation dramatically decreased at the start of the Younger Dryas, which means that the trigger for the event resided in the ocean. Atmospheric circulation changes followed close behind.
However, it reveals a bit of mystery about the end of the Younger Dryas. Schmidt said it appears that the atmosphere started to recover before the ocean’s conveyor belt restarted, suggesting that the tropics play an important role in bringing an end to cold intervals.
“Something was going on in the tropics that was causing the tropics to rebound or recover, and possibly that was what triggered the ocean’s conveyor belt to come on to really bring us back to the warmer conditions,” Schmidt said. “A lot of people would be shocked by that. They think that when the conveyor is strong, it’s warm; and when it’s weak, it’s cold. This study calls that into question.”
Schmidt said it’s clear from this study that the climate state has distinct equilibrium modes, which lead to abrupt transitions. “One thing this type of study tells us is that we should be cautious about what we’re doing to the climate state,” he said.
“You might be going along and there might not be much change, but that doesn’t mean you’re not getting close to a threshold where there’s going to be a rapid change,” Schmidt said. “It’s kind of like pulling a rubber band. You can pull it, and pull it, and pull it, and not much happens, but suddenly it snaps.”
Q: You hear a lot about sandstorms lately. What causes sandstorms?
A. Sandstorms are caused by strong winds that occur in desert or semi-arid regions, and they carry thick clouds of dust and sand, often reducing visibility to near zero in many cases, says
John Nielsen-Gammon of Texas A&M University. In many parts of the world, such as the deserts of the Southwest U.S. or in Africa or the Middle East, sandstorms can create havoc with man and machine. “A sandstorm can last for several hours to a full day,” says Nielsen-Gammon. “Most of the time, sandstorms affect only the air from about 1-3 miles high, so airplanes flying above that range are okay. But on the ground, sand moving at about 50 miles an hour can be a real nightmare. It can clog up just about anything that is mechanical, from a soldier’s rifle to a car or an army tank. Once the sandstorm has passed, a thorough cleaning of just about anything is required.”
Q: What types of sandstorms can occur?
A: There are two types of sandstorms, says Nielsen-Gammon. “The first kind is the result of a severe thunderstorm that creates strong winds. This kind is called a ‘haboob,’ which is an Arabic word for blowing dust. The second type is the one most Americans are familiar with. It’s caused by a curving of the jet stream which brings strong winds to the surface. Sandstorms tend to be worse during the daytime because the ground is heated up by the sun and the dust can be carried greater distances. That’s why breathing can become a real problem, and some type of mask is often required. Probably the worst sandstorms occur in China and Mongolia. The sand blows so hard that there is a ‘yellow rain’ effect. So much sand is in the air that it changes the color of raindrops, and there appears to be a yellow rain falling from the sky.”
Weather Whys is a service of Texas A&M University’s Department of Atmospheric Sciences.
COLLEGE STATION, Sept. 6, 2011 — Clouds only amplify climate change, says a Texas A&M University professor in a study that rebuts recent claims that clouds are actually the root cause of climate change.
Andrew Dessler, a Texas A&M atmospheric sciences professor considered one of the nation’s experts on climate variations, says decades of data support the mainstream and long-held view that clouds are primarily acting as a so-called “feedback” that amplifies warming from human activity. His work is published today in the American Geophysical Union’s peer-reviewed journal Geophysical Research Letters.
Dessler studied El Niño and La Niña cycles over the past 10 years and calculated the Earth’s “energy budget” over this time. El Nino and La Nina are cyclical events, roughly every five years, when waters in the central Pacific Ocean tend to get warmer or colder. These changes have a huge impact on much of the world’s weather systems for months or even years.
Dessler found that clouds played a very small role in initiating these climate variations — in agreement, he says, with mainstream climate science and in direct opposition to some previous claims.
“The bottom line is that clouds have not replaced humans as the cause of the recent warming the Earth is experiencing,” Dessler says.
Texas is currently in one of the worst droughts in the state’s history, and most scientists believe it is a direct result of La Niña conditions that have lingered in the Pacific Ocean for many months.
Dessler adds, “Over a century, however, clouds can indeed play an important role amplifying climate change.”
“I hope my analysis puts an end to this claim that clouds are causing climate change,” he adds.
For more information about Dessler’s research, go to http://goo.gl/zFJmt
About Research at Texas A&M University: As one of the world’s leading research institutions, Texas A&M is in the vanguard in making significant contributions to the storehouse of knowledge, including that of science and technology. Research conducted at Texas A&M represents an annual investment of more than $630 million, which ranks third nationally for universities without a medical school, and underwrites approximately 3,500 sponsored projects. That research creates new knowledge that provides basic, fundamental and applied contributions resulting in many cases in economic benefits to the state, nation and world.