Extreme Weather and Climate Change
Polar Vortex Observation from NASA JPL AIRS
NASA reconstructed map of Earth’s surface temperature from 1884 to 2012
Australia Climate Commission interview talking about Australia’s heat wave
Any global citizen will note the dramatic increase in major extreme weather events taking place around the world in the last few years.
- 2014 – Unprecedented floods in UK
- 2014 – Ice storm in Eastern United States and Canada
- 2013 – 2014 Australia Extreme Heat Wave
- 2013 – Largest Typhoon in history hits Phillipines
- 2013 – unprecedented floods caused by a cyclone in Sardinia
- 2012 – 2013 – unprecedented rains that caused the Pakistan floods in August 2013 and last year
- 2013 – Extreme drought in California and Western US
New and old research correlate the extreme weather events now common place (and about to become even more common) with climate change. The basic reason explaining the extreme weather is actually quite simple; human beings are pumping extraordinary amounts of energy into our environment and this enormous increase of energy in our environment manifests as more extreme, energetic weather. Denialists continuing claiming that Climate change does not “cause” extreme weather because no scientist will claim a direct causal relationship. However, it does cause it indirectly because it has essentially increased the amount of energy in the atmosphere, making any extreme weather event much more likely.
The great California drought is something entirely predicted by scientists as early as 2004. That year, Lisa Sloan, professor of Earth sciences at UC Santa Cruz, and her graduate student Jacob Sewall published an article in Geophysical Research Letters: Disappearing Arctic sea ice reduces available water in the American west. The researchers used powerful computers running a global climate model developed by the National Center for Atmospheric Research (NCAR) to simulate the effects of reduced Arctic sea ice. Using a fully coupled earth system model, the abstract of their research study claimed “Our results indicate that future reductions in Arctic sea ice cover could significantly reduce available water in the American west ”
The computer model predicts one major result of declining levels of Arctic sea ice – creation of high pressure blocking cell in the atmosphere off the West Coast of United States. This is exactly what meteorologists are now observing, a decade later. The pressure cell is four miles high and 2,000 miles long and has remained in place for months. It’s stubbornness has earned it the name Ridiculously Resilient Ridge.
In 2004, Sewall described the projected effects in New Scientist magazine:
Towers of warm air form above areas where sea ice has been lost, and that disturbs the flow of air in the atmosphere around them, “like the supports under a bridge alter the flow of water in a river.”
In their model Sewall and Cirbus Sloan found that such towers formed between Norway and Greenland, deflecting winter storms that would otherwise have passed over the west coast of the US towards northern British Columbia and southern Alaska.
These areas received six per cent more rain, while southern British Columbia down to southern California suffered a 30 per cent drop. The researchers will publish their results in a future issue of Geophysical Research Letters. “Given that water resources in this region are currently stretched close to their limit, a 30 per cent drop would have a serious impact,” says Sewall.
Water levels in reservoirs would probably drop, making water rationing a necessity. Meanwhile agriculture would suffer from a lack of water for irrigation and famous national parks, such as Yosemite in California, could change completely as natural ecosystems adapted to a drier climate.
Ten years later, in 2014, this is exactly what meteoroligist observe. The high pressure ridge has been acting like a brick wall and forcing the jet stream to divert around it along a much more northerly track, blocking Pacific winter storms from arriving on the West Coast of California and instead, deflecting up into Alaska and British Columbia…just as predicted 10 years earlier.
Figure 1a: Differences in DJF [winter] averaged atmospheric quantities due to an imposed reduction in Arctic sea ice cover. The 500-millibar geopotential height (meters) increases by up to 70 m off the west coast of North America. Increased geopotential height deflects storms away from the dry locus and north into the wet locus(Jacob Sewall 2005)
Exactly how much more energy are we talking about? Mike Sandiford is the director of the Melbourne Energy Institute at the University of Melbourne and he uses a new measure that is being increasingly used, the “Hiro”. One Hiro is equal to the energy released by detonating one Hiroshima “Little Boy” bomb every second. One Hiro equals 60 trillion watts. In these terms:
- Global warming has pumped 5 Hiros into the oceans over the last few decades – the energy equivalent of detonating more than a 150 million Hiroshima bombs in our oceans each year
- The radiative forcing of the CO2 we have already put in the atmosphere in the last century is a staggering 13 Hiros – the equivalent of almost half a billion Hiroshima bombs into the atmosphere each year
The movie shows a tongue of cold air moving out of Canada and southward to cover much of the eastern United States during early January 2014. This extreme weather event was covered extensively in the media, and introduced the term ‘polar vortex’ to a broader audience. This is not a global phenomenon and primarily affects the eastern half of the United States. The AIRS global observations allows us a global perspective by piecing together such local variations in climate as the Polar Vortex. While this was happening, Alaska and northern Eurasia were warm during this period of unusual cold over the eastern United States.
NASA’s observations are helping to piece together the complex and local response to the increased energy in our climate system.
An Arctic Wild Card in the Weather
Everyone thinks of Arctic climate change as this remote phenomenon that has little effect on our everyday lives but what goes on in the Arctic remotely forces our weather patterns in other parts of the world. The dramatic melt-off of Arctic sea ice due to climate change is therefore something that concerns every single person on the planet. While it is far away from civilization, major degradation of Arctic sea ice is triggering a domino effect leading to increased odds of severe weather outbreaks in the Northern Hemisphere’s middle latitudes such as the “Snowmageddon” storm that shutdown Washington, D.C., during February 2010, the record-breaking heatwave across the US in 2012 and Hurricane Sandy in Oct 2012.
Cornell’s Charles H. Greene, professor of earth and atmospheric sciences, and Bruce C. Monger, senior research associate in the same department at Cornell University, are disentangling the mechanics of how the Arctic climate system affects the entire global climate system in the paper An Arctic Wild Card in the Weather published in the June 2012 issue of the journal Oceanography.
Figure 1: Negative Arctic Oscillation conditions are associated with higher pressure in the Arctic and a weakened polar vortex (yellow arrows). A weakened jet stream (black arrows) is characterized by larger-amplitude meanders in its trajectory and a reduction in the wave speed of those meanders.
The Arctic region is colder than the mid-latitude temperate zones. This difference in temperature propels the west-to-east river of fast-moving air known as the Jet Stream. This atmospheric feature separates warm air to its south from cold air to the north, and tends to follow a wavy path as it flows around the Northern Hemisphere between about 30 degrees N and 60 degrees N. The Jet Stream usually resides near the altitude where jets fly, hence its name. As high latitudes warm more than mid-latitudes, however, this north-south temperature difference weakens, which has two impacts on the jet stream.
Cold air is normally trapped in the Arctic in winter by strong Polar Vortex winds, which circle the North Pole from west to east and the strong pressure field that is shown in purple/blue colors in Figure 1a, below left. This pattern broke down in December 2009, and in February 2010, (below middle and right). North-south winds increased, allowing cold Arctic air to spill southwards.
Figure 2. Arctic Atmospheric Pressure: normal 850 mb geopotential height values which were observed for December from 1968-1996 (left) and unusual 850 geopotential height values that were observed for December 2009 (middle) and for February 2010 (right). Figures from NOAA/ESRL Physical Sciences Division.
Warm Arctic – Cold Continents
The cold air that descends into the lower part of the continents creates the Warm Arctic-Cold Continent Pattern, shown below for December 2009 and 2010:
- Red colors indicate areas where the Arctic was 9°F or 5°C warmer than normal
- Purple colors indicate areas where the continents were 9°F or 5°C cooler than normal
Warmer than normal Arctic temperatures were seen especially in regions that were sea-ice-free in summer: north of Alaska and in the Barents Sea. The cold continents are seen where Arctic air penetrated southward. Some warm air penetrates northward near Bering Strait and east Greenland.
Figure 3. Warm Arctic (red) – Cold Continents (purple) pattern in (a) December 2009 and (b) December 2010. Shown are anomalies or deviations from the normal 1000 mb air temperature values which were observed from 1968-1996. Data are from the NCEP-NCAR Reanalysis through the NOAA/ESRL Physical Sciences Division.
The Polar Vortex was weak in other years as well. In late autumn and early winter 2005, 2008, 2010, but especially 2009, a weak Polar Vortex and associated increase in southward flowing winds coming out of the Arctic brought record cold and snow conditions to northern Europe, eastern Asia and eastern North America. In autumn 2009, Northern Eurasia (north of 50° latitude to the Arctic coast) and North America (south of 55° latitude) were particularly cold, 3 -18° F cooler than the normal monthly average, and Arctic regions were more than 7°F warmer than average.
The North Atlantic Oscillation (NAO) climate index had it’s lowest value in 145 years for Winter 2009/2010
One indicator of a weak Polar Vortex is the North Atlantic Oscillation (NAO) index. Winter 2009/2010, which saw two major winter cold continent events, had the lowest NAO value in 145 years of historical record. In other years, Winter 2005-2006 had a primary influence in Eurasia and December 2008 had a more local influence in northeastern Canada.
Influences on sub-Arctic weather
Meteorological attribution to these sub-Arctic events is difficult. The last five years have been the warmest recorded period in the Arctic and climate conditions over the Arctic cannot be ruled out as influencing weather in some sub-Arctic regions, making it relative colder for part of the winter.
Arctic Amplification causes two major effects
Arctic amplification describes the tendency for high Northern latitudes to experience enhanced warming or cooling relative to the rest of the Northern Hemisphere. This heightened sensitivity is linked to the presence of snow and sea ice, and the feedback loops that they trigger.
1. Slow the west-to-east speed of the jet stream to make weather appear stuck and last a long time
This phenomenon already appears to be occurring:
- Upper-level winds around the Northern Hemisphere have slowed during autumn, from October to December, which is exactly when sea ice loss exerts its strongest effect on the north-south temperature gradient
- Some regions exhibit even larger drops in wind speed, such as over North America and the North Atlantic, where winds have slowed by about 14 percent since 1980
- A decrease in the west-east flow tends to slow the eastward progression of waves in the jet stream
- Because these waves control the formation and movement of storms, slower wave progression means that weather conditions last longer and appear “stuck”
- This effect appears to play an important role mainly in autumn, because as sea ice reforms in winter, the north-south temperature difference gradually returns to more normal values
2. Increases the Waviness (north /south amplitude) of the Jet Stream, bringing extreme weather
- A warmer Earth increases the melting of sea ice during summer, exposing more dark ocean water to incoming sunlight
- This causes increased absorption of solar radiation and excess summertime heating of the ocean — further accelerating the ice melt
- The ocean then releases this excess heat to the atmosphere, especially during the autumn, decreasing the temperature and atmospheric pressure gradients between the Arctic and middle latitudes
- A diminished latitudinal pressure gradient is linked to a weakening of the winds associated with the polar vortex and jet stream
- Since the polar vortex normally acts like a retaining wall to keep the cold Arctic air masses up above the Arctic Circle, the weakening allows the cold air which contains elevated moisture to escape the Arctic circle and descend into lower latitudes
- The Jet Stream oscillates between an upper and lower lattitude. The northern peaks of waves, called ridges, will experience more warming than the southward dips, called troughs
- This causes the ridges to stretch northward, which will increase the size of the waves
- Larger swings in the jet stream allow frigid air from the Arctic to plunge farther south, as well as warm, moist tropical air to penetrate northward
- These wavy flows often lead to record-breaking temperatures
- Meteorologists have also known for a long time that larger jet-stream waves progress eastward more slowly, as will the weather systems associated with them. Hence, wave speed is decreased and causes weather conditions to linger – in other words, extreme weather events last longer
The recent observations present a new twist to the Arctic Oscillation (AO) — a natural pattern of climate variability in the Northern Hemisphere. Before humans began warming the planet, the Arctic’s climate system naturally oscillated between conditions favorable and those unfavorable for invasions of cold Arctic air.
In the winter of 2011-2012, an extended cold snap descended on central and eastern Europe in mid-January, with temperatures approaching -22 Fahrenheit and snowdrifts reaching rooftops
There were also record snowstorms in several eastern U.S. cities, such as Washington, New York and Philadelphia, as well as many other parts of the Eastern Seaboard during the previous two years
Yet in 2011, the eastern US experienced the warmest winter on record.
In any particular region, many factors can have an influence, including the El Nino/La Nina cycle. In the winter of 2011, La Nina in the Pacific shifted undulations in the jet stream so that while many parts of the Northern Hemisphere were hit by the severe winter weather patterns expected during a bout of negative AO conditions, much of the eastern United States basked in the warm tropical air that swung north with the jet stream
So while the eastern U.S. missed out on the cold and snow this winter, and experienced record-breaking warmth during March, many other parts of the Northern Hemisphere were not so fortunate
Europe and Alaska experienced record-breaking winter storms, and the global average temperature during March 2012 was cooler than any other March since 1999. Weather it’s extreme cold or hot depends on a lot of factors
The Arctic wildcard stacks the deck in favor of more severe winter outbreaks in the future.
Greene writes: “Winter weather surprises, running both cold and warm, have captured headlines in the United States and Europe during the past three years. Remarkably, remote climate forcing from the Arctic appears to have played a prominent role in the dynamics of both. The dynamical teleconnections linking recent changes in Arctic climate to middle-latitude weather are gradually being disentangled from the background noise in Earth’s climate system.”
(Source: NOAA, Cornell University)
Feb 9, 2014 – Recent Intensification of wind-driven circulation in the Pacific and the ongoing warming hiatus
Global warming has not stopped. People should understand that the planet is a closed system. As we increase our emissions of greenhouse gases, the fundamental thermal dynamics tells us we have added heat into the system. Once it’s trapped, it can go to a myriad of places – land surface, oceans, ice shelves, ice sheets, glaciers for example.
- Professor Mathew England, University of New South Wales
Figure 4: Climate Haiku from Greg Johnson NOAA / PMEL
Scientists have been mystified about the pause in the rise of the Surface Air Temperature (SAT) since 1998. Now, a paper by a team lead by Professor Mathew England of the University of New South Wales may have solved the riddle. Climate scientists see no contradiction in the multi-decade pause but climate denialists have seized the opportunity to use it as a misleading explanation that global warming is not real. As all climate scientists know, global warming spreads its heat energy into many different places and the air actually constitutes a very small heat sink – only accounting for absorption of 2.3% of total anthropogenically produced heat. The ocean is by far the biggest heat sink, sucking up over 90% of all excess energy. In his paper, Recent Intensification of wind-driven circulation in the Pacific and the ongoing warming hiatus , England and his team offers a scientifically sound explanation of how the Pacific Trade Winds have helped the Tropical Pacific Ocean to absorb vast amounts of heat into the thermocline – the area in the ocean that is roughly between 100 metres and 300 metres deep.
The study shows that there have been unusually strong trade winds beginning near 2000 and expected to continue until the end of this decade. These winds have stored the heat energy in the thermocline in an oceanic area off the east coast of Australia called the West Pacific Warm Pool. The trade winds are expected to return to normal within a few years rather than decades, and this will cause the averaged surface temperatures to rise sharply again.
Figure 5: Schematic of the trends in temperature and ocean–atmosphere circulation in the Pacific over the past two decades. Colour shading shows observed temperature trends (°C per decade) during 1992–2011 at the sea surface (Northern Hemisphere only), zonally averaged in the latitude-depth sense and along the equatorial Pacific. (Source: Nature Climate Change)
Figure 6: Corrections to IPCC Climate Projections (Source: Nature Climate Change)
Potential for a Giant El Nino in 2014
A recent reversal in the direction of the Pacific trade winds appears to have started a warming trend in Feb / Mar 2014. That was enough to prompt US government forecasters to issue an El Niño watch last month. Forecasters are increasingly confident in a particularly big El Niño this time around because, deep below the Pacific Ocean’s surface, off-the-charts warm water is lurking a giant warm body of water.
Figure 7: Monthly time series showing movement of large volume of warm water in Pacific Ocean (Source: Australian Bureau of Meteorology)
The time/depth/latitude series graph shows how this huge mass of warm water (equivalent in volume to the entire United States and 100 meter deep) is beginning to surface as it spreads eastward. Once it hits the surface, it will interact with the atmosphere and begin to influence the global weather pattern.
Figure 8: Sea level height (Source: NASA Earth Observatory)
Images from the Ocean Surface Topography Mission/Jason 2 satellite shows the height above sea level is higher,caused by warmer water and thermal expansion.