Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Climate change responsible for increased hurricanes

31.05.2006


Human induced climate change, rather than naturally occurring ocean cycles, may be responsible for the recent increases in frequency and strength of North Atlantic hurricanes, according to Penn State and Massachusetts Institute of Technology researchers.



"Anthropogenic factors are likely responsible for long-term trends in tropical Atlantic warmth and tropical cyclone activity," the researchers report in an upcoming issue of the American Geophysical Society’s EOS.

Michael E. Mann, associate professor of meteorology and geosciences, Penn State, and Kerry A. Emanuel, professor of atmospheric sciences, MIT, looked at the record of global sea surface temperatures, hurricane frequency, aerosol impacts and the so-called Atlantic Multidecadal Oscillation (AMO) Ð an ocean cycle similar, but weaker and less frequent than the El Nino/La Nina cycle. Although others have suggested that the AMO, a cycle of from 50 to 70 years, is the significant contributing factor to the increase in number and strength of hurricanes, their statistical analysis and modeling indicate that it is only the tropical Atlantic sea surface temperature that is responsible, tempered by the cooling effects of some lower atmospheric pollutants.


"We only have a good record of hurricanes and sea surface temperature for a little more than the last 100 years," says Mann, who is also director of Penn State’s Earth System Science Center. "This means we have only observed about one and a half to two cycles of the AMO. Peer-reviewed research does suggest that the signal exists, but it is difficult to estimate the period and magnitude of the oscillation directly from observations."

To determine the contributions of sea surface warming, the AMO and any other factors to increased hurricane activity, the researchers used a statistical method that allows them to subtract the effect of variables they know have influence to see what is left.

"There appears to be a strong historical relationship between variations in tropical Atlantic sea surface temperature and tropical cyclone activity extending back through the 19th century," say Mann and Emanuel.

The cause of increased tropical Atlantic sea surface temperatures is the real question. One contributor must be overall global sea surface temperature trends. The researchers looked at the sea surface temperature record in the tropical Atlantic and compared it to global sea surface temperatures. They found that the tropical temperatures did closely follow the global temperatures, but that global fluctuation did not account for everything. They first found what appeared, at least superficially, to be a significant influence from the AMO in the tropical Atlantic.

To test if the fluctuation was indeed due to the AMO, they looked only at data from before 1950. They found that the apparent AMO signal became indistinguishable from the statistical noise if the recent cooling trend between 1950 and the 1980s was not included.

"This pattern of late 20th century cooling has been attributed in past work to the anthropogenic production of tropospheric aerosol," note Mann and Emanuel in their paper. This human-caused cooling, they found, was masquerading as part of an apparent natural oscillation.

While some gases, such as carbon dioxide and methane in the upper atmosphere create the greenhouse effect associated with global warming, other pollutants, such as sulfur dioxide and nitrogen oxides in the lower atmosphere cool the Earth’s surface by reflecting sunlight.

Because of prevailing winds and air currents, pollutants from North American and Europe move into the area above the tropical Atlantic. The impact is greatest during the late summer when the reflection of sunlight by these pollutants is greatest, exactly at the time of highest hurricane activity.

When Mann and Emanuel use both global temperature trends and the enhanced regional cooling impact of the pollutants, they are able to explain the observed trends in both tropical Atlantic temperatures and hurricane numbers, without any need to invoke the role of a natural oscillation such as the AMO.

Without taking into account the mitigating effect of pollutants, the results were higher than what had actually occurred. This suggests that the cooling from pollutants in the atmosphere tempered the rise of sea surface temperatures and hurricane numbers.

However, the industrialized world is doing much better at controlling pollution. North America and Europe have both reduced the amounts of aerosols they put into the atmosphere. The cooling effect has been decreasing since the 1980s.

Absent the mitigating cooling trend, tropical sea surface temperatures are rising. If the AMO, a regional effect, is not contributing significantly to the increase, than the increase must come from general global warming, which most researchers attribute to human actions.

Vicki Fong | EurekAlert!
Further information:
http://www.psu.edu

More articles from Earth Sciences:

nachricht More than 100 years of flooding and erosion in 1 event
28.03.2017 | Geological Society of America

nachricht Satellites reveal bird habitat loss in California
28.03.2017 | Duke University

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A Challenging European Research Project to Develop New Tiny Microscopes

The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.

To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Transport of molecular motors into cilia

28.03.2017 | Life Sciences

A novel hybrid UAV that may change the way people operate drones

28.03.2017 | Information Technology

NASA spacecraft investigate clues in radiation belts

28.03.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>