Tag Archives: meteorology

To What Degree is Extreme Weather Linked to Climate Change?

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As flood waters continue to inundate Thailand and drought parches Texas, the Intergovernmental Panel on Climate Change and Goddard Institute for Space Studies Director James Hansen have both released new statements about the connection between extreme weather and climate change. Although linking extreme weather to climate change has generated controversy in the past, both of the new reports point plainly to a connection.The IPCC, an international organizational that represents the scientific consensus of hundreds of leading climatologists, put it this way in the executive summary of its new report.

It is very likely that there has been an overall decrease in the number of cold days and nights, and an overall increase in the number of warm days and nights, on the global scale, i.e., for most land areas with sufficient data. It is likely that these changes have also occurred at the continental scale in North America, Europe, and Australia.There have been statistically significant trends in the number of heavy precipitation events in some regions. It is likely that more of these regions have experienced increases than decreases, although there are strong regional and subregional variations in these trends.

There is medium confidence that some regions of the world have experienced more intense and longer droughts, in particular in southern Europe and West Africa, but in some regions droughts have become less frequent, less intense, or shorter, e.g., in central North America and northwestern Australia.There is evidence that some extremes have changed as a result of anthropogenic influences, including increases in atmospheric concentrations of greenhouse gases. It is likely that anthropogenic influences have led to warming of extreme daily minimum and maximum temperatures on the global scale. There is medium confidence that anthropogenic influences have contributed to intensification of extreme precipitation on the global scale.

There is limited to medium evidence available to assess climate-driven observed changes in the magnitude and frequency of floods at regional scales because the available instrumental records of floods at gauge stations are limited in space and time, and because of confounding effects of changes in land use and engineering. Furthermore, there is low agreement in this evidence, and thus overall low confidence at the global scale regarding even the sign of these changes.


Meanwhile, Hansen has released the draft of a new paper (pdf) that also tackles the topic of extreme weather and climate. He’s somewhat less equivocal in his summary of the state of the science:

The “climate dice” describing the chance of an unusually warm or cool season, relative to the climatology of 1951-1980, have progressively become more “loaded” during the past 30 years, coincident with increased global warming. The most dramatic and important change of the climate dice is the appearance of a new category of extreme climate outliers. These extremes were practically absent in the period of climatology, covering much less than 1% of Earth’s surface. Now summertime extremely hot outliers, more than three standard deviations (σ) warmer than climatology, typically cover about 10% of the land area. Thus there is no need to equivocate about the summer heat waves in Texas in 2011 and Moscow in 2010, which exceeded 3σ – it is nearly certain that they would not have occurred in the absence of global warming. If global warming is not slowed from its current pace, by mid-century 3σ events will be the new norm and 5σ events will be common.

Text by Adam Voiland. Lead image of flooding in Ayutthaya published originally by NASA’s Earth Observatory. Extreme weather curves published originally by the IPCC. Land trends over land published originally on James Hansen’s Columbia University website. 

Snowpocalypse Revisited

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Though the summer heat and humidity makes it seem like a lifetime ago, the record-breaking snows in the eastern U.S. last winter are not something we will soon forget. Several feet of powder fell on most of the Mid-Atlantic region during February 2010, and this week a study from Columbia University’s Lamont-Doherty Earth Observatory gives us new insight into what caused the freaky weather.

A rare combination of weather — not climate — patterns seems to be the culprit. El Niño produced abnormally wet conditions in the southeastern U.S.; a negative North Atlantic Oscillation pushed frigid Arctic air down from the North. This collision of moisture with abnormally cold air led to more than six feet of snow over the region between December 2009 and February 2010.

The visualization above, derived from the Goddard Earth Observing System Model Version 5 (GEOS-5) and created by NASA Goddard’s Scientific Visualization Studio, shows the first wave of the February snowstorms hitting the East Coast about four seconds into the animation. The second wave forms off the west coast of Mexico’s Yucatan peninsula — about twelve seconds in — and then pummels the East Coast.

— Michelle Williams, NASA’s Goddard Space Flight Center

Soaring for Science

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NASA's Global Hawk autonomous plane

The newest bird in NASA’s flock — the unmanned Global Hawk — took off at 7 a.m. Pacific time today (April 2) from Dryden Flight Research Center at Edwards Air Force Base in California. The flight is the first airborne checkout of the plane since it was loaded with 11 science instruments for the Global Hawk Pacific (GloPac) mission.

Pilots are also streamlining processes to coordinate the workload while the nearly autonomous plane is flying at altitudes above 60,000 feet (almost twice as high as a commercial airliner). Operators and mission researchers are using the day to make sure all instruments are operating properly while in flight — particularly at the cold temperatures of high altitude — and communicating clearly with the plane and ground controllers. Mission participants expect to begin collecting data when actual GloPac science flights begin over the Pacific Ocean later this month.

GloPac is the Global Hawk’s first scientific mission. Instruments will sample the chemical composition of air in Earth’s two lowest atmospheric layers — the stratosphere and troposphere — and profile the dynamics and meteorology of both. They also will observe the distribution of clouds and aerosol particles. The instruments are operated by scientists and technicians from seven science institutions and are funded by NASA and the National Oceanic and Atmospheric Administration (NOAA).

Paul Newman, the co-mission scientist for GloPac, has been blogging about the mission on Earth Observatory’s “Notes from the Field” site. Here are a few excerpts to whet your appetite…

…There is an old Latin quote: “Maxima omnium virtutum est patientia.” Or “patience is the greatest virtue.” When it comes to mounting science instruments on an aircraft, you need to continually return to that quote…

…During the integration this week, we’ve had to cut holes into the aircraft. I told Chris Naftel, the Global Hawk project manager, that we had to cut some holes into the plane for the Meteorological Measurement System. Chris replied: “I don’t want to hear anything about the holes. It pains me!” In spite of Chris’ pain, the little holes are critical for measuring winds. You’re now asking, what? Little holes? For winds? It’s actually a very slick little measurement that relies on the work of Daniel Bernoulli, a Dutch mathematician who lived in the 1700s…

Read more here …

Flying high with NASA's Joanne Simpson

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Joanne Simpson, the first woman to earn a PhD in meteorology, didn’t just break into a field where women weren’t welcome. She broke the door down and accumulated a list of scientific achievements that’s rare for any scientist, regardless of gender.

Early in her career, she made the key insight that narrow cumulonimbus clouds–she called them “hot towers” — are the engines that drive tropical circulation and help sustain the eyes of hurricanes. Later, she became one of the first scientists to develop a cloud model, an advance that ultimately sparked a whole new branch of meteorology. She spent decades with NASA, helping to lead the Tropical Rainfall Measurement Mission, a satellite that’s led to key insights about how hurricanes start and how dust affects precipitation. And she was a key proponent for the upcoming Global Precipitation Measurement (GPM), the follow up satellite to TRMM.

No stranger to controversy, she stirred up a scientific furor when she sought to test the validity of her cloud model by experimenting with cloud seeding. Even well into her eighties, Simpson didn’t shy from vigorous debate about the scientific basis of global warming.

In March, at the age of 86, Simpson passed away in Washington, D.C. In a recent interview with the Discovery Channel, a producer asked her what was the most fascinating thing about studying the atmosphere. “In my case, it’s the clouds,” she said without hesitation. “There are some beautiful ones out there right now,” she said while gesturing toward the window.

In tribute to Simpson’s efforts to understand clouds, we’ve chosen four of our favorite cloud images from a series of images that Simpson donated to the NOAA Photo Library and likely took. The photographs were taken from NASA’s DC-8 during the TOGA-COARE project in the 1990s.

Joanne Simpson Portrait Information: Illustration by Martin Mueller of NRC and NASA GSFC via NASA’s Earth Observatory.


Puffy fair weather cumulus clouds and hints of reefs are visible below the right wing of NASA’s DC-8. Credit: NOAA Photo Library/Dr. Joanne Simpson Collection


A towering example of a showering anvil cloud roils over the Pacific Ocean. Credit: NOAA Photo Library/Dr. Joanne Simpson Collection


Dusk falls over the Pacific Ocean with a large cumulonimbus cloud in the distance. Credit: NOAA Photo Library/Dr. Joanne Simpson Collection

— Adam Voiland, NASA’s Earth Science News Team