What was 2017 weather summary?

People move through flooded streets in Havana after the passage of Hurricane Irma in September. The 2017 season had the highest number of major hurricanes since 2005. (Photo credit: Ramon Espinosa, Associated Press)

The National Oceanic and Atmospheric Administration has completed its scientific analysis and the globally averaged surface temperature for 2017 was the third-highest since record keeping began in 1880.

The warmest year is 2016, and 2015 is the second warmest. Since 1977 global temperatures have been at least nominally above the 20th century average. The six warmest years on record have occurred since 2010.

Everyone has his or her own personal stories of top 2017 weather events. Chances are many will remember the cold weather at the end of December.

Temperatures were mostly above normal in the first two-thirds of December, particularly the week before Christmas. Then Arctic air pushed south across the region and extended all the way to the Gulf of Mexico in the last week of the year, bringing cold temperatures to southern Wisconsin. The cold outbreak was enough to make average December temperature in southern Wisconsin below normal by 2 to 3 degrees. A lake-effect snowfall dumped 66 inches in Erie, Pennsylvania, at the end of December.

At the end of the year, southern Wisconsin was 20 inches below normal in total snowfall. Yet the average annual Northern Hemisphere snow cover extent during 2017 was above the 1981-2010 average, the largest since 1985 and the eighth-largest in the 1968-2017 record.

Recent trends in the decline of Arctic sea ice extent continued in 2017. The average annual sea ice extent in the Arctic was approximately 4.01 million square miles, the second-smallest annual average in the 1979-2017 record.

The 2017 hurricane season was one of only six seasons on record to feature multiple Category 5 hurricanes. This was the second season on record (after 2007) to feature two hurricanes making landfall at Category 5, Irma’s landfalls on multiple Caribbean islands and Maria’s landfall on Dominica. This season had the highest number of major hurricanes since 2005.

On a warmer note, the summer average temperature for Wisconsin was about average, with summer precipitation above average.

Category: Climate, Meteorology

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Is there snow and ice on other planets?

Becky Williams, science researcher with the Mars rover Curiosity project, examines imagery captured on the surface of the planet on a computer screen in the work office of her Waunakee home. The researcher was the lead author of an article in the journal Science regarding the team’s discovery of water evidence on the planet in 2013. (Photo credit: John Hart, State Journal Archives)

Like Earth, the north and south poles of Mars have ice caps that grow and shrink with Mars’ seasons.

Mars’ ice caps are made mainly of water ice, although Mars is cold enough to also have frozen carbon dioxide, or dry ice.

Carbon dioxide is in the Martian atmosphere and it freezes and falls to the surface of the planet as dry ice snow.

The Mars Reconnaissance Orbiter, or MRO, has observed pools of seemingly pure ice at the bottom of small meteorite craters. Radar observations of Mars have indicated that deposits of ice are buried below the surface.

Recently, the MRO has detected layers of ice in exposed cliffs poleward of 55 degrees north and south.

The banding structure in the cliffs suggests the deposits built up over many seasons and may provide clues to Mars’ past climate.

The Lunar Reconnaissance Orbiter has detected water ice in shadowy craters near the north and south poles of Earth’s moon. Enceladus, one of Saturn’s moons, has an icy surface and is the brightest moon in our solar system.

Below its icy surface is a heated ocean. Geysers shoot water from below out into space. The water freezes and falls back to the surface as snow.

Saturn’s smallest moon, Mimas, is a ball of almost pure water ice about 123 miles across.

Neptune’s largest moon, Triton, has geysers like Enceladus. These geysers are made up of nitrogen rather than water. This nitrogen freezes, covering Triton with ice made of frozen nitrogen.

Io, one of the many moons orbiting Jupiter, has “snowflakes” made out of sulfur.

Category: Meteorology, Uncategorized

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What is a ‘bomb cyclone’?

Vehicles move along a snow and ice covered Interstate 26, near Savannah, Ga., Wednesday, Jan. 3, 2018. A brutal winter storm dumped snow in Tallahassee, Fla., on Wednesday for the first time in nearly three decades before slogging up the Atlantic coast and smacking Southern cities such as Savannah and Charleston, South Carolina, with a rare blast of snow and ice. (Photo credit: Robert Ray, Associated Press)

The term “bomb cyclone” refers to the formation and rapid development of a mid-latitude cyclone. A mid-latitude cyclone is a large-scale, low-pressure system, characteristic of the middle latitudes, that has counter-clockwise flow around its center (in the Northern Hemisphere).

A primary measure of development in these storms is a drop in the atmospheric pressure at the center of the storm. Air near the ground is forced to move inward to the center of the circulation — this is known as convergence.

In the upper levels of the atmosphere above the center of a developing mid-latitude cyclone there is divergence, the opposite of convergence. If the divergence of air above is stronger than the convergence of air near the surface, the surface pressure will fall and the mid-latitude cyclone will intensify.

If the barometric pressure of a mid-latitude cyclone falls by at least 1 millibar per hour for 24 hours, the storm is referred to as a “bomb.” A millibar is a unit of pressure that measures the weight of the atmosphere above you. The average sea-level pressure is about 1,010 millibars, so in a bomb cyclone about 2.3 percent of the atmosphere above is removed and moved someplace else.

Meteorologists have used the term ‘bomb cyclone’ for at least 50 years.

They are not rare events, as on average there are about 40 events each year in the Northern Hemisphere. As with any weather event, the number of bomb cyclones varies from year to year.

The recent storm on the East Coast was a bomb cyclone. It is also referred to as a nor’easter – a mid-latitude cyclone that affects the northeastern United States and extreme eastern Canada.

Category: Phenomena, Seasons, Severe Weather

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Does this cold wave prove the globe is not warming?

What had been a warmer than normal December, with the first 22 days averaging nearly 4.8 degrees above normal, was transformed to slightly below normal by a dramatic cold wave to end the month.

Global Temperature Anomalies
(departures from normal )
on December 28, 2017.
Credit: Climate Reanalyzer

Over the last week of December we averaged about 11 degrees below normal. This sudden change, though not unprecedented, was foreseen in various medium-range forecasts made before Christmas. But it has captured the nation’s attention as 2017 draws to a close.

Unfortunately, some of that attention may contribute to misunderstanding — motivated by President Trump’s recent statement suggesting such a cold wave provides evidence that his administration’s denial of climate change has been vindicated. Defense of the reality of global warming is particularly challenged by the cherry-picking skeptic during winter, as any period of below-average temperatures, and every winter will have some, is construed as evidence to the contrary.

However, the facts are that December 2017 was the 15th-warmest of the past 70 Decembers and that the areal extent of Northern Hemispheric cold air poked barely above average for the first time all month just a couple of days ago. This is consistent with a systematic warming of the Northern Hemisphere winter over the past seven decades that is unequivocally a manifestation of increased CO² concentrations and the associated global warming.

Science extends our collective “senses” to provide evidence of the workings of the natural world. As leader of our great country, the president has an obligation to assess his skepticism in the face of empirical facts. To do less is to neglect the duties of his office.

Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on WHA radio (970 AM) at 11:45 a.m. the last Monday of each month.
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Did climate change kill the dinosaurs?

Landsat image of the Sudbury Basin in Ontario,
the remnants of an asteroid impact that
occurred ~1.8 billion years ago.  Credit: USGS.

Sixty-six million years ago, the age of the dinosaurs ended abruptly, coinciding with the extinction of about 75 percent of the total number of living species.

Evidence and climate modeling indicate that global wildfires resulted from a collision with a massive asteroid that could have lofted large amounts of soot into the atmosphere. The smoke would have plunged Earth into darkness for nearly two years, which would have shut down photosynthesis, drastically cooled the planet, and contributed to the mass extinctions as evidenced in the fossil record.

It is now an accepted scientific fact that objects from outer space can and do collide with planets. The collision of the Shoemaker-Levy comet with Jupiter in 1994 provided spectacular evidence that extraterrestrial objects can affect a planet’s atmosphere.

Depending on its exact location, a major asteroid impact on Earth and the debris ejected by the impact can cause extended darkness due to global fires, acid rain, ozone loss and even mile-high tsunamis.

In 1990, evidence was discovered of an impact with an asteroid that occurred about 66 million years ago near the Yucatán Peninsula. Named for a local village, the Chicxulub crater is a 112-mile-wide impact crater visible in gravity and magnetic field data. The crater size is consistent with a 6- to 12-mile-wide asteroid.

Remnants of the asteroid have been found in sediments worldwide, confirming its global influence. The Chicxulub impact was probably not a once-in-history event. There are indications in the fossil record of other extinction events that occur every 26 million years or so.

Scientists are coming to the realization that on very long time scales the history of Earth, including its climate, may be periodically upset by asteroid and comet impacts.

Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of Atmospheric and Oceanic Sciences, are guests on WHA radio (970 AM) at 11:45 a.m. the last Monday of each month.
Category: Climate, Phenomena

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