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The warmer, greener Arctic and greenhouse gas

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About 15% of the Northern Hemisphere is covered by permafrost.  Permafrost is soil and sediment that has remained frozen for long periods of time, in some cases as much as 700,000 years.  It contains large amounts of dead biomass that has accumulated over millennia and hasn’t fully decomposed.  Therefore, permafrost is an immense carbon sink.

The Arctic is warming four times faster than the rest of the planet and, as a result, thawing permafrost is becoming a carbon source.  As warming continues, ice is melting, and vegetation is spreading.    A new study, published in Nature Climate Change, looked at the state of the Arctic and boreal north from the period 1990 until 2020.  The study found that although half of the Arctic region has been growing greener, only 12% of those green areas are actually taking up more carbon.  For one thing, the growth of forests means that there is more fuel for wildfires which are increasingly common.

A study of lakes in West Greenland found that thousands of crystal blue lakes have turned brown during record heat spells.  Runoff from melting permafrost made the lakes opaque killing off plankton that absorb carbon dioxide.  Meanwhile, plankton that release carbon dioxide multiplied.  So, these lakes went from being carbon sinks to being carbon sources.

As the northern latitudes warm, ice and permafrost are melting, vegetation is spreading, and the region is becoming a source of heat-trapping gas after having been a place where carbon has been locked away for thousands of years.  According to the Nature Climate Change study, roughly 40% of the Arctic is now a source of carbon dioxide.

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Warmer, Greener Arctic Becoming a Source of Heat-Trapping Gas

Photo, posted October 14, 2024, courtesy of Christoph Strässler via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Thawing permafrost in the Arctic

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Permafrost covers about a quarter of the landmass in the Northern Hemisphere.  It stores vast quantities of organic carbon in the form of dead plant matter.  As long as it stays frozen, it is no threat to the climate.  But as permafrost thaws, microorganisms start breaking down that plant matter and large amounts of carbon are released into the atmosphere in the form of carbon dioxide and methane.

Scientists estimate that there could be two and a half times as much carbon trapped in Arctic permafrost as there is in the atmosphere today.

Thawing permafrost poses various risks to the Arctic environment and the livelihoods of its people.  According to a new study led by researchers from the University of Vienna in Austria, Umeå University in Sweden, and the Technical University of Denmark, thawing permafrost threatens the way of life of up to three million people.

To identify these risks, the research team studied four Arctic regions in Norway, Greenland, Canada, and Russia between 2017 and 2023.  The research, which was recently published in the journal Communications Earth and Environment, identified five key hazards posed by the thawing permafrost: infrastructure failure, disruption of mobility and supply, decreased water quality, challenges for food security, and exposure to diseases and contaminants.

These are present developments – not future dangers.  Global scientific cooperation, policy interventions, and investment in research are critical to mitigate the impact of thawing permafrost and address the broader consequences it brings.

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A transdisciplinary, comparative analysis reveals key risks from Arctic permafrost thaw

Thawing permafrost threatens up to three million people in Arctic regions

Photo, posted February 9, 2017, courtesy of Benjamin Jones / USGS via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Cold spells and global warming

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January saw some major bouts of subfreezing temperatures across much of North America and significant snowfall in places like Pensacola, Florida and New Orleans.  This spate of frigid weather undoubtedly prompted many people to question whether global warming is really happening.  But such cold spells quite likely are not happening in spite of global warming, but actually as a result of it.

The polar jet stream is a slim band of westerly winds that circles the Arctic.  It is formed where cold air from the north meets warmer air to the south.  As the planet warms, the Arctic has been heating up nearly four times faster than the rest of the planet, which narrows the difference in temperature between the northern air and southern air.  The result is that the jet stream is weaker and more meandering, which allows frigid air to reach further south.

The polar vortex is a whirling mass of cold air that extends across the Arctic.  It is stronger in the winter when the Northern Hemisphere leans away from the sun.  The polar jet stream normally holds on to the vortex and keeps it far to the north.  But when the jet stream gets wobbly, this mass of cold air can break out and travel south, even to places like Florida, Louisiana, and Texas.

The planet as a whole is warming, and the Arctic is warming even faster.  But there will still be plenty of ice, snow, and frigid air in the Arctic winter for decades to come.  As the behavior of the polar jet stream gets increasingly erratic, there may well be more frequent episodes of plunging temperatures in areas unaccustomed to them.

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Severe Cold Spells May Persist Because of Warming, Not in Spite of It

Photo, posted January 5, 2025, courtesy of Dermot O’Halloran via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Shrinking polar ice

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Arctic sea ice has shrunk to near-historic lows during this Northern Hemisphere summer.  The minimum extent for the year occurred on September 11th.  Ice cover in the Arctic Ocean has been shrinking and thinning for more than 40 years.  The amount of frozen seawater in the Arctic goes up and down during the year as sea ice thaws and regrows between seasons.

This year, the minimal extent of sea ice shrank to 1.65 million square miles.  That’s about 750,000 square miles less than the average for late summer over the years between 1981 and 2010, representing a decrease of more than 30%.  The all-time low of 1.31 million square miles was actually set in 2012.  Sea ice coverage can fluctuate from year to year, but it has trended downward since it has started being tracked in the late 1970s.  The loss of sea ice has averaged about 30,000 square miles per year.

Sea ice extent has not only been shrinking; the ice has been getting younger and thinner.  Presently, the overwhelming majority of ice in the Arctic Ocean is first-year ice, which is thinner and less able to survive the warmer months.  There is far less ice that is three years or older.

Meanwhile, sea ice in the southern polar regions was also low this year.  In the sea around Antarctica, scientists are tracking near record-low sea ice at a time when it should have been growing extensively during the darkest and coldest months in the Southern Hemisphere.

Polar ice loss compounds polar ice loss.  The loss of sea ice increases heat in the polar regions, where temperatures have risen about four times more than the global average.

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Arctic Sea Ice Near Historic Low; Antarctic Ice Continues Decline

Photo, posted September 15, 2016, courtesy of Mario Hoppmann via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

And the heat goes on

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August 2024 was the hottest August in the 175-years for which there are global records.  The last full month of summer also wrapped up the Northern Hemisphere‘s warmest summer on record.

The average global surface temperature in August was 62.39 degrees Fahrenheit, which is 2.29 degrees above the 20th century August average.  Furthermore, August was the 15th consecutive month of record-high global temperatures, which is a record in and of itself.

Regionally, Europe and Oceana had their warmest August on record.  Asia had its second-warmest August, and Africa and North America had their third-warmest August.

The summer in the Northern Hemisphere was a record-breaker with a temperature 2.74 degrees Fahrenheit above average.  Thinking about climate goals, this is 1.52 degrees Celsius above average, which is a troubling amount.  Meanwhile, in the Southern Hemisphere, where it was winter in the June-to-August period, it was also the warmest ever with a temperature 1.73 degrees Fahrenheit above average.

Globally, this year to date ranks as the warmest ever recorded with a temperature 2.3 degrees above the 20th-century average.  With a few months to go, the prediction is that there is a 97% chance that 2024 will rank as the world’s warmest year on record.

Other aspects of the global climate system were consistent with these record-breaking temperatures.  The global ocean surface temperature for June through August was the warmest on record. 

These monthly climate reports have an unfortunate similarity:  the heat goes on.

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Earth had its hottest August in 175-year record

Photo, posted June 22, 2021, courtesy of Vicky Brock via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Thawing permafrost:  Is it a ticking timebomb?

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Permafrost covers about a quarter of the landmass in the Northern Hemisphere.  It stores vast quantities of organic carbon in the form of dead plant matter.  As long as it stays frozen, it is no threat to the climate.  But as it thaws, microorganisms start breaking down that plant matter and large amounts of carbon are released into the atmosphere in the form of carbon dioxide and methane.

This process has often been described as a ticking timebomb for the climate.  The theory is that once global warming reaches a certain level, the process will become self-amplifying setting off a catastrophic amount of warming.  If that level was reached, it would be a tipping point in the changing climate.

An international research team from the Alfred Wegener Institute in Germany has extensively researched this hypothesis.  Their conclusion is that within the permafrost, there are multiple geological, hydrological, and physical processes that are self-amplifying and, in some cases, irreversible.  However, these processes act only locally or regionally.  There is no evidence that some particular threshold in global warming could affect all permafrost and accelerate its thawing on a global level.

This research does not mean that Arctic permafrost is nothing to worry about.  In fact, there are ways in which it is more worrisome.  Because the permafrost is very heterogenous – meaning it is very different in different places – there will be numerous small, local tipping points that will be exceeded at different times and at different levels of warming.  All of this will proceed in step with global warming, contributing to the overall worsening situation.  There is no warming level below which permafrost thawing is not a problem.

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Thawing permafrost: Not a climate tipping element, but nevertheless far-reaching impacts

Photo, posted January 24, 2014, courtesy of Brandt Meixell / USGS via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Summers are getting hotter

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Climate scientists have warned for decades that a seemingly small change in the global average temperature can lead to large changes in extreme heat.  So far, the world has warmed by 1.2 degrees Celsius (or 2.2 degrees Fahrenheit) and that has been enough to cause big changes in summer heat.

This past summer was the hottest on record.  The heat fueled deadly wildfires across the Mediterranean.  Record highs caused Chinese cities to suspend outdoor work.  Weeks of triple-digit temperatures in the U.S. southwest led to heat-related hospitalizations and deaths.

But not every recent summer has been hotter everywhere.  Even this summer saw average or even colder than average temperatures in some places.  But the distribution of summer temperatures across the Northern Hemisphere has shifted dramatically in recent decades.

Less than 1% of summers in the middle of the 20th century were extremely hot for their location.  Over the past decade, more than a quarter of summers were extremely hot for their location.

Between 1950 and 1980, about a third of summers across the hemisphere were near average in temperature; a third were considered cold; a third were hot.  Only a few summers in a few places were either extremely cold or extremely hot.  Over the past decade, the vast majority of summers have either been hot or extremely hot.

We experience summer weather in the location where we spend our time, and it is entirely possible that our own experience may have been unremarkable.  We may even have had a cool, rainy summer.  But on a global scale, summers are getting hotter and hotter and making it harder to ignore what is happening to our planet.

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It’s Not Your Imagination. Summers Are Getting Hotter.

Photo, posted August 21, 2022, courtesy of Bonnie Moreland via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Triple La Niña | Earth Wise

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La Niña is an oceanic phenomenon consisting of cooler than normal sea-surface temperatures in the central and eastern tropic Pacific.  It is essentially the opposite of the better-known El Niño.   These sea-surface phenomena affect weather across the globe.  As one oceanographer put it:  when the Pacific speaks, the whole world listens.

There is currently a La Niña underway, and it is the third consecutive northern hemisphere winter that has had one.  This so-called triple-dip event is rather rare.  The only other times they have been recorded over the past 70 years were in 1954-56, 1973-76, and 1998-2001.

La Niñas appear when strong easterly trade winds increase the upwelling of cooler water from the depths of the eastern tropical Pacific Ocean near the equator.  This causes large-scale cooling of the ocean surface.  The cooler ocean surface modifies the moisture content of the atmosphere across the Pacific and can cause shifts in the path of jet streams that intensifies rainfall in some places and causes droughts in others.

These weather effects tend to include floods in northern Australia, Indonesia, and southeast Asia and, in contrast, drought in the American southwest.  In North America, cooler and stormier conditions often occur across the Pacific Northwest while the weather becomes warmer across the southern US and northern Mexico.

In the spring, the tropic Pacific essentially resets itself and starts building toward whatever condition will happen in the following winter, be it another La Niña or possibly an El Niño.   For the time being, forecasters expect the current La Niña to persist through February.

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La Niña Times Three

Photo, posted March 10, 2007, courtesy of Gail via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Climate Change And Hurricanes In The Northeast | Earth Wise

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According to a new study led by Yale University, more hurricanes are likely to hit Connecticut and the northeastern U.S. as global warming continues to increase temperatures in the region.

Hurricane Henri made landfall in August as a tropical storm on the Connecticut/Rhode Island border.  In September 2020, subtropical storm Alpha made landfall in Portugal, the first subtropical or tropical cyclone ever observed to make landfall in the mainland of that country.

Tropical cyclones, hurricanes, and typhoons are typically intense and destructive in the lower latitudes. 

The study concludes that violent storms could migrate northward in our hemisphere and southward in the southern hemisphere as a result of warming caused by greenhouse gas emissions.

The research predicts that tropical cyclones will likely occur over a wider range of latitudes than has been the case on Earth for the last 3 million years.

In Connecticut, Hurricane Henri was not the only tropical storm to affect the region in 2021.  The remnants of Hurricane Ida brought damaging winds and torrential rain that felled trees and flooded streets and basements.

The northern expansion of such violent storms is going on as water levels in the Atlantic Ocean and Long Island Sound keep rising.  Because of melting glaciers thousands of miles away, water levels in Long Island Sound could rise by as much as 20 inches by 2050, enough to submerge parts of Groton’s shore and cause regular flooding in roads and neighborhoods.

Future hurricane prediction is an inexact science, but the ongoing trends do not bode well for the region.

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More hurricanes likely to slam Connecticut and region due to climate change, says study

Photo, posted October 29, 2012, courtesy of Rachel via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Climate Change And The Winter Olympics | Earth Wise

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According to a new study led by researchers from the University of Waterloo in Canada, climate change will limit where the Winter Olympics can be held as winter changes across the Northern Hemisphere. 

The international research team found that by the end of the century only one of the 21 cities that have previously hosted the Winter Olympics would be able to reliably provide fair and safe conditions for winter sports if global greenhouse gas emissions are not dramatically reduced. 

However, if the emissions targets set forth in the Paris Climate Agreement can be reached, the number of climate-reliable host cities for the Winter Olympics would jump to eight.

In the study, which was recently published in the journal Current Issues in Tourism, the researchers reviewed historical climate data from the 1920s to today, as well as future climate change scenarios for the 2050s and 2080s.  The researchers also surveyed international athletes and coaches, and found that 89% of them felt that changing weather patterns are already affecting competition conditions. 

The average February daytime temperature of host cities has been steadily increasing.  At the winter games held between the 1920s and 1950s, the average temperature was 32.7°F.  It rose to 37.6°F at games between the 1960s and 1990s, and has spiked to 43.3°F in the games held in the twenty-first century.  The planet is projected to warm another 3.6°F to 7.9°F this century depending on our ability to mitigate greenhouse gas emissions.

Reducing global greenhouse gas emissions is critical to ensure that there remain places across the globe to host the Winter Olympics.

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Climate change threatens future Winter Olympics

Photo, posted February 21, 2010, courtesy of Michael via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

July Was A Scorcher | Earth Wise

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July 2021 has the unfortunate distinction as being the world’s hottest month ever recorded according to global data from the National Oceanic and Atmospheric Administration.   July is typically the warmest month of the year, but this July was the warmest month of any year on record.

The combined global land and ocean surface temperature was 62.07 degrees Fahrenheit, which is 1.67 degrees above the 20th century average.  This was the highest monthly average since records began 142 years ago.  It broke the previous record set in July 2016 and tied in 2019 and 2020.

The Northern Hemisphere was 2.77 degrees above average.  Asia had its hottest July on record.  Europe had its second hottest July on record.  Places like Africa, Australia, and New Zealand all had top-ten warmest Julys.

Other aspects of the changing climate included the observation that Arctic sea ice coverage for July was the fourth-smallest in the 43-year record.  Interestingly, Antarctic sea ice extent was actually above average in July.  Global tropic cyclone activity this year so far is above normal for the number of named storms.  In the Atlantic basin, the formation of the storm Elsa on July 1 was the earliest date for a 5th named storm.

It remains very likely that 2021 will rank among the 10 hottest years on record.  Extreme heat is a reflection on the long-term climate changes that were outlined recently in a major report released by the Intergovernmental Panel on Climate Change.  These latest global observations add to the disturbing and disruptive path that the changing climate has set for the world.

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It’s official: July was Earth’s hottest month on record

Photo, posted July 15, 2021, courtesy of Lori Iverson/National Interagency Fire Center via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

A Hot July | Earth Wise

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The numbers are in and, unsurprisingly, July was a hot month.  July 2020 tied for the second-hottest July on record for the planet, according to the National Oceanic and Atmospheric Administration.  In our own backyard, the Northern Hemisphere saw the hottest July ever, breaking the previous record set just last year.

The July 2020 global temperature was 62.06 Fahrenheit, which is 1.66 degrees above the 20th-century average.  The combined land and ocean surface average temperature for the Northern Hemisphere, the highest ever recorded for July, was 2.12 degrees F above average, breaking the previous record by 0.14 degrees.

Record-hot July temperatures were also recorded across parts of southeastern Asia, northern South America, across the west and northern Pacific Ocean, the northern Indian Ocean, and parts of the Caribbean Sea.

The year-to-date global land and ocean surface temperature was the second highest in the 141 years of record keeping at 58.79 degrees Fahrenheit, which is 1.89 degrees F above the 20th-century average. 

So far it is been the hottest year to date on record across a large portion of northern Asia, parts of Europe, China, Mexico, northern South America, as well as the Atlantic, northern Indian and Pacific oceans.

Meanwhile, the extent of sea ice in the Arctic for July 2020 was the smallest ever measured in the 42 years of record-keeping, over 23% below the 1981-2010 average.  July’s Arctic sea ice extent was smaller than the previous record (set last year) by 120,000 square miles, an area roughly the size of New Mexico.

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July 2020 was record hot for N. Hemisphere, 2nd hottest for planet

Photo, posted July 24, 2018, courtesy of Maria Eklund Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Side Effects Of Geoengineering | Earth Wise

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As the world struggles to reduce the greenhouse gas emissions that are warming the global climate, some researchers are exploring proposals to deliberately engineer climate changes to counteract the warming trend.  One of the most widely discussed approaches is to shade the Earth from a portion of the sun’s heat by injecting the stratosphere with reflective aerosol particles.  Proponents of this idea point out that volcanoes do essentially the same thing, although generally for only a limited amount of time.  Particularly large eruptions, such as the Krakatowa eruption of 1883, wreaked havoc with weather around the world for an entire year.

Schemes to launch reflective aerosols – using planes, balloons, and even blimps – appear to be quite feasible from the standpoint of physically accomplishing them. But this says nothing about the political, ethical, and societal issues involved.  The point is that such an approach could indeed lower global temperatures and thereby potentially offset the warming effects of greenhouse gases.

A study by scientists at MIT looked at what other effects such a solar geoengineering project might have on the climate.  Their modeling concluded that it would significantly change storm tracks in the middle and high latitudes.  These tracks give rise to cyclones, hurricanes, and many more ordinary weather phenomena.

According to the study, the northern hemisphere would have weakened storm tracks, leading to less powerful winter storms, but also stagnant conditions in summer and less wind to clear away air pollution.  In the southern hemisphere, there would be more powerful storm tracks.

Aside from turning the world’s weather patterns inside out, solar geoengineering would do nothing to address the serious issue of ocean acidification caused by increasing carbon dioxide levels.

As many have pointed out, playing the geoengineering game would have many unintended consequences.

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Study: Reflecting sunlight to cool the planet will cause other global changes

Photo courtesy of MIT.

Earth Wise is a production of WAMC Northeast Public Radio.

Saving The Arctic Permafrost | Earth Wise

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Permafrost is frozen ground – a combination of soil, rock, sand, and ice – that remains at or below freezing for at least two consecutive years.  Approximately 25% of the land in the Northern Hemisphere meets this criterion, the majority of which can be found in northern Russia, Canada, Alaska, Iceland, and Scandinavia.

But as a result of the changing climate, these permafrost soils in the Arctic are beginning to thaw.  As they thaw, large quantities of greenhouse gases could be released, further accelerating climate change.  

A new study recently published in the journal Scientific Reports explores an unconventional countermeasure: resettling massive herds of large herbivores.  According to researchers from the University of Hamburg in Germany, herds of horses, bison, and reindeer could be used to significantly slow the loss of permafrost soils. 

During Arctic winters, the air temperature is often much colder than the permafrost.  Thick layers of snow can insulate the ground from the frigid air, keeping the permafrost warm (relatively speaking). But when the snow cover is scattered and compressed by the hooves of grazing animals, the insulating effect is reduced, which intensifies the freezing of the permafrost.

If climate change continues unchecked, the research team expects permafrost temperatures to rise 3.8-degrees Celsius.  This would result in half of the world’s permafrost thawing by the year 2100.  But in contrast, researchers found that the permafrost would only warm by 2.1 degrees Celsius with the resettled animals.  This 44% reduction in permafrost temperature would preserve 80% of the existing permafrost by 2100.

Natural manipulations of ecosystems could have tremendous results. 

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How horses can save the permafrost

Photo, posted July 17, 2012, courtesy of Kitty Terwolbeck via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

The Arctic As A Carbon Source

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According to a new NASA-funded study, the Arctic may now be a source for carbon in the atmosphere rather than being the sink for it that is has been for tens of thousands of years.

The study, published in Nature Climate Change, warns that carbon dioxide loss from the world’s permafrost regions could increase by more than 40% over the next century if human-caused greenhouse gas emissions continue at their current pace.  Worse yet, carbon emitted from thawing permafrost has not even been included in most climate models.

Permafrost is the carbon-rich frozen soil and organic matter that covers nearly a quarter of Northern Hemisphere land area, mostly in Alaska, Canada, Siberia, and Greenland.  Permafrost holds more carbon than has ever been released by humans from fossil fuel burning, but it has been safely locked away by ice for tens of thousands of years.

As global temperatures rise, the permafrost is starting to thaw and release greenhouse gases into the atmosphere.

The recent findings indicate that the loss of carbon dioxide during the winter in the Arctic may already be offsetting carbon uptake during the growing season.  The researchers compiled on-the-ground observations of carbon dioxide emissions across many sites and combined these with remote sensing data and modeling.  They estimate that the permafrost region is now losing 1.7 billion metric tons of carbon during the winter season but taking up only 1 billion during the growing season.

The major concern is that as the Arctic continues to warm, more carbon will be released into the atmosphere from the permafrost region, which will further the warming.  Climate modeling teams across the globe are trying to incorporate these findings into their projections.

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Arctic Shifts to a Carbon Source due to Winter Soil Emissions

Photo, posted July 27, 2015, courtesy of Gary Bembridge via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

The Importance Of The Amazon Rainforest Fires

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The Amazon rainforest covers extensive parts of Brazil, Peru, Colombia, and small parts of six other countries.  It is the largest rainforest in the world and is instrumental in driving the weather and climate in South America.

The raging wildfires in the Amazon rainforest are a source of great concern.  The Amazon is always prone to wildfires during the dry season in South America, but the extent and number of fires this year cannot be attributed simply to drought.  The surge in fires has come from illegal deforestation by loggers and farmers, who are using the cleared-out land for cattle ranching.

Rainforests produce consistently high amounts of rainfall throughout the year by pulling water from the soil and then releasing it into the atmosphere.  The Amazon rainforest essentially makes it rain in South America. 

Over time, the forest plays a crucial role in cycling carbon out of the atmosphere by turning it into biomass.  The Amazon jungle sucks up as much as a quarter of the planet’s atmospheric carbon dioxide.

Pristine rainforest burns less frequently and less intensely than cleared and recovering forest.  As more and more of the Amazon rainforest is deforested, it becomes more likely to burn each year.

The major disruption of the water dynamics in South America has the potential to not only drive the weather in South American countries but even potentially influence natural resources like snow packs in the Northern Hemisphere.

The skies of Sāo Paulo, Brazil’s financial hub have been dark at midday because of the Amazon fires.  This is like having a fire in California and seeing the smoke in Boston.  The Amazon rainforest fires are a big problem for the whole world.

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The Amazon Rainforest has been burning for weeks. Here’s why that matters.

Photo, posted August 21, 2019, courtesy of NASA Goddard Space Flight Center via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Climate Change And Harsh Winters

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In recent years, there have been some unusually harsh winters in North America and Central Europe. This past January, the Midwestern US experienced extreme cold temperatures. We have all become familiar with the term ‘polar vortex’ and its role in sending cold air to middle latitudes and it is generally agreed that unusual behavior by the jet stream is the primary cause of the extreme winter weather.

For years, climate researchers around the world have been investigating the question as to whether the increasingly common wandering of the jet stream is a product of climate change or is a random phenomenon associated with natural variations in the climate system.

The jet stream is a powerful band of westerly winds over the middle latitudes that push major weather systems from west to east.  These days, the jet stream is increasingly faltering.  Instead of blowing along a straight course parallel to the equator, it sweeps across the Northern Hemisphere in massive waves, producing unusual intrusions of Arctic air into the middle latitudes.

Atmospheric researchers at the Alfred Wegener Institute in Germany have now developed a climate model that can accurately predict the frequently observed winding course of the jet stream.  The breakthrough combines their global climate model with a new machine learning algorithm on ozone chemistry.  Using their new combined model, they can now show that the jet stream’s wavelike course in winter and subsequent extreme weather outbreaks are the direct result of climate change.  The changes in the jet stream are to a great extent caused by the decline in Arctic sea ice, according to the results of the investigations.  The results are not surprising but there is now a detailed model to support the hypothesis.

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A warming Arctic produces weather extremes in our latitudes

Photo, posted January 11, 2011, courtesy of Carl Wycoff via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Examining Sea Level Rise

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It’s no secret that sea levels along the East Coast of the United States are rising.  But what’s less known is that the water isn’t rising at the same rate everywhere.  As the climate continues to change, some cities may remain dry while others struggle to keep water out. 

During the 20th century, sea levels rose about 18 inches near Cape Hatteras in North Carolina and along the Chesapeake Bay in Virginia.  During that same time period, New York City and Miami experienced a 12 inch sea level rise, while the waters near Portland, Maine only rose 6 inches.  According to a study recently published in the journal Nature, there’s an explanation for this. 

The variation is a result of a phenomenon called “post-glacial rebound.”  During the last ice age, huge sheets of ice once covered land areas in the Northern Hemisphere, including parts of the Northeast U.S.  The weight of the ice weighted down the land like a boulder on a trampoline.  At the same time, peripheral lands such as the U.S. mid-Atlantic coast rose up.  As the ice melted, the previously weighted-down regions rebounded while the peripheral lands began to sink.  While these ice sheets disappeared some 7,000 years ago, this see-sawing of post-glacial rebound continues to this day. 

Researchers combined data from GPS satellites, tide gauges, and fossils in sediment with complex geophysical models to produce this comprehensive view of sea level change since 1900.  While post-glacial rebound accounts for most of the sea level variation along the East Coast, researchers noted that when that factor is stripped away, “sea level trends increased steadily from Maine all the way down to Florida.”

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Why is sea level rising faster in some places along the US East Coast than others?

Photo, posted August 24, 2014, courtesy of Bill Dickinson via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Sahara Greening And Tropical Cyclones

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Global weather patterns are influenced by environmental conditions in places around the world.  One of the world’s major weather creators is the Sahara Desert.  The Sahara is the largest hot desert in the world.  The only larger deserts of any sort are in the polar extremes of the planet and are thus not hot deserts at all.

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