A ‘PERFECT STORM’: EXTREME WINTER WEATHER, BITTER COLD, IRRITATING HOT AND CLIMATE CHANGE

January 13, 2018 0

The Impact of Climate Change on Natural Disasters
Climate change may not be responsible for the recent skyrocketing cost of natural disasters, but it is very likely that it will impact future catastrophes. Climate models provide a glimpse of the future, and while they do not agree on all of the details, most models predict a few general trends. First, according to the Intergovernmental Panel on Climate Change, an increase of greenhouse gases in the atmosphere will probably boost temperatures over most land surfaces, though the exact change will vary regionally. More uncertain—but possible—outcomes of an increase in global temperatures include increased risk of drought and increased intensity of storms, including tropical cyclones with higher wind speeds, a wetter Asian monsoon, and, possibly, more intense mid-latitude storms.

Changes in climate not only affect average temperatures, but also extreme temperatures, increasing the likelihood of weather-related natural disasters. If global climate change causes the global average temperature to rise (top), there will be less cold weather, and a greater probability of hot and record hot weather. An increase in temperature variability will extend the extremes of temperature, both cold and hot. An increase in average temperature combined with increased variance will have little effect on cold weather, but hot weather will be more common and record hot weather will increase greatly. 
Global warming could affect storm formation by decreasing the temperature difference between the poles and the equator. That temperature difference fuels the mid-latitude storms affect the Earth’s most populated regions. Warmer temperatures could increase the amount of water vapor that enters the atmosphere. The result is a hotter, more humid environment. At the equator, where conditions are already hot and humid, the change isn’t expected to be large. At the poles, however, the air is cold and dry; a little extra heat and water vapor could raise temperatures greatly. As a result, global warming may cause the temperature difference between the poles and the equator to decrease. and as the difference decreases, so should the number of storms, says George Tselioudis, a research scientist at NASA Goddard Institute for Space Studies (GISS) and Columbia University.

But even as a warming climate might decrease the overall number of storms that form, it could increase the number of intense storms. As temperatures continue to rise, more and more water vapor could evaporate into the atmosphere, and water vapor is the fuel for storms. “If we are creating an atmosphere more loaded with humidity, any storm that does develop has greater potential to develop into an intense storm,” says Tselioudis.

The combined result of increased temperatures over land, decreased equator-versus-pole temperature differences, and increased humidity could be increasingly intense cycles of droughts and floods as more of a region’s precipitation falls in a single large storm rather than a series of small ones. A warmer, wetter atmosphere could also affect tropical storms (hurricanes), but changes to tropical storms are harder to predict and track. Some scientists have speculated that a warmer climate that allows more intense storms to develop would also spawn more hurricanes. Warmer temperatures may also heat ocean waters farther from the Equator, expanding the reach of large tropical storms. But there is little evidence to support the either of these theories, says Kerry Emanuel, a professor of tropical meteorology and climate in the Massachusetts Institute of Technology’s Program in Atmospheres, Oceans, and Climate.

The one way in which global warming could impact hurricanes is by making them more intense. More heat and water in the atmosphere and warmer sea surface temperatures could provide more fuel to increase the wind speeds of tropical storms. Warming that has already occurred since 1980 has increased sea surface temperatures 0.3 degrees Celsius, which should increase the maximum potential wind speed of hurricanes by 1 knot, according to hurricane intensity models. But increases that small could not have been observed yet. “At present, hurricane intensity is measured only to an accuracy of plus or minus five knots, so it is not possible to discern any change that might have occurred owing to warming that has already taken place,” says Emanuel.

Even if tropical storms don’t change significantly, other environmental changes brought on by global warming could make the storms more deadly. Melting glaciers and ice caps will likely cause sea levels to rise, which would make coastal flooding more severe when a storm comes ashore. In their 2001 report, the Intergovernmental Panel on Climate Change stated that global warming should cause sea levels to rise 0.11 to 0.77 meters (0.36 to 2.5 feet) by 2100.

World-renowned climate scientist Dr. Michael Mann explains why the bitter cold and snowy conditions gripping the US are “an example of precisely the sort of extreme winter weather we expect because of climate change.”

The US East Coast is experiencing an “old-fashioned” winter, with plenty of cold weather and some heavy snowfall in certain places. Listening to climate contrarians like President Donald Trump, you might think this constitutes the death knell for concern over human-caused climate change.

Yet, what we were witnessing play out is in fact very much consistent with our expectations of the response of weather dynamics to human-caused climate change.

Let’s start with the record five-plus feet of snowfall accumulation in Erie, Pennsylvania, in late December. Does this disprove global warming? “Exactly the opposite,” explains my colleague, Dr. Katharine Hayhoe of Texas Tech University.

Global warming is leading to later freeze-up of the Great Lakes and warmer lake temperatures. It is the collision of cold Arctic air with relatively warm unfrozen lake water in early winter that causes lake effect snows in the first place. The warmer those lake temperatures, the more moisture in the air, and the greater potential for lake effect snows. Not surprisingly, we see a long-term increase in lake effect snowfalls as temperatures have warmed during the last century.
How about those frigid low temperatures back east this winter? Surely that extreme cold must disprove global warming?
Once again, the claim is misguided. While we have seen some daily all-time lows for a smattering of locations in the US, these pale in comparison with the number of all-time highs we’ve seen over the past year. In fact, the record highs have outpaced the record lows 61 to seven, i.e. nine times more often (see table below), consistent with what we expect to see as the globe continues to warm.


Moreover, while we’ve seen some cold weather in the eastern half of the North America (see the pattern for New Year’s Day below), the western half of North America has been unusually warm. Indeed, most of the Northern Hemisphere, and the globe overall, have been unusually warm. That’s why we call it global warming, folks.

(Image obtained using Climate Reanalyzer, Climate Change Institute, University of Maine, USA)

But what about this pattern of cold in the eastern US and warm in the western US? This so-called “dipole” pattern has become more common in recent winters, and recent research suggests that climate change may be favoring this contrast in temperature by causing the jet stream to meander in a particular pattern, with an upward meander or “ridge” in the west bringing warm air up from the south and a downward meander or “trough” in the east, bringing cold air down from the north. Some scientists think that the dramatic loss of sea ice in the Arctic may be favoring this jet stream pattern.

Finally, the news is abuzz today with an impending “massive Nor’easter,” a “bomb cyclone” that is “set to explode” in the days ahead (see plot below). This isn’t just hype. The National Weather Service has warned that “this rapidly intensifying East Coast storm will produce strong, damaging winds — possibly resulting in downed trees, power outages, and coastal flooding.”

With a central pressure forecast to drop very low (see plot below), the storm will threaten the record set by unprecedented 2012 Superstorm Sandy as the lowest surface pressure ever measured in the North Atlantic north of Cape Hatteras (the central surface pressure of a storm is one measure of its strength).

(© 2018 ECMWF cc by nc nd 4.0)

Surely such a massive winter storm, with its promise of bitter cold winds and potentially heavy coastal snowfalls, must be evidence against the climate crisis?

Once again, rather the opposite is true. East Coast winter storms, known as “nor’easters” because of the unusual northeasterly direction of the winds as the storm spirals in from the south, are unusual in that they derive their energy not just from large contrasts in temperature that drive most extratropical storm systems, but also from the energy released when water evaporates from the (relatively warm) ocean surface into the atmosphere.

This is a characteristic that these storms share with tropical storms and hurricanes. The warmer the ocean surface, the more energy that is available to intensify these storms. And the warmer the ocean surface, the more moisture there is in the atmosphere – moisture that is available to form precipitation. As the winds wrap around in a counter-clockwise manner, they bring all of that moisture northwest, where it is chilled and ultimately falls not as rain but snow. Lots of snow.

As the oceans continue to warm, cold Arctic air masses collide with increasingly warm Atlantic Ocean waters. That means larger temperature contrasts and potentially stronger storms. But those warmer oceans also mean more moisture in the atmosphere, even more energy to strengthen the storm, and the potential for larger snowfalls.  We might, if you’ll forgive the pun, call this a “perfect storm” of factors for intensification.

Indeed, climate model simulations indicate that we can expect more intense nor’easters as human-caused climate change continues to warm the oceans.

(Image obtained using Climate Reanalyzer, Climate Change Institute, University of Maine, USA)
This leads us back to the current strengthening storm. The entire North Atlantic is unusually warm right now (+0.6 degrees Celsius) relative to the already-globally-warmed late twentieth century (1971-2000) average, and there are large patches of ocean water off the US East Coast that are 2-4 degrees Celsius above that average. The storm will be encountering that exceptional ocean heat as it travels northward along the US coastline, and that is part of why it has a very good chance of becoming the most intense nor’easter we’ve yet observed.

So, to the climate change doubters and deniers out there, the unusual weather we’re seeing this winter is in no way evidence against climate change. It is an example of precisely the sort of extreme winter weather we expect because of climate change.

EXTREME HEAT


One of Australia’s most major highways, the Hume Freeway linking Melbourne to Sydney, has seen some interesting traffic patterns as of late. It’s all thanks to the tar in the road literally melting under sustained 100-plus degree temperatures of a heat wave.


 A good six-odd mile of the Hume outside of Melbourne in the southeast was melting a few days ago, as declared in this very matter-of-fact traffic advisory:

It’s not really that the whole road is melting, just the tar. (That’s the tar in tarmac.) Basically, the tar holds the solids of the road together, it gets hot and gooey, and the once-solid-looking road starts to melt.

Sustained temperatures cresting 100 and 110 degrees Fahrenheit are to blame, as NPR noted. It gave a further explanation of why the road itself would melt from an earlier report from the BBC when something similar happened in a 2013 heatwave in the United Kingdom:

“Asphalt is like chocolate — it melts and softens when it’s hot, and goes hard and brittle when it’s cold — it doesn’t maintain the same strength all year round,” an expert in road surface treatments told the British broadcaster.

The area has stayed sweltering hot over the weekend, as evidenced by this kangaroo taking a dip in someone’s backyard pool.
SAN DIEGO COUNTY HEAT IS GETTING IRRITABLE

Dense fog hung over parts of San Diego County Friday morning, but the patchy areas of fog and low clouds are expected to give way to clear skies and above-average temperatures later in the day.

A warming trend that began Thursday will continue Friday and throughout the weekend thanks to a high-pressure system, according to the National Weather Service.

Winds in the foothills, mountains and deserts are expected to pick up with gusty winds up to 40 miles per hour possible on Saturday.

The coastal areas will enjoy temperatures in the 60s and 70s to end the week. Inland areas will see temperatures in the 70s, topping off in the mid 80s on Sunday.


The mountain region will reach temperatures in the mid 60s; and the desert temps will bounce around the 70s.

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