High Amplitude Jet Stream Pattern To Lead to Extremely Abnormal Temps for Central/Eastern US; “Blow Torch” Heat to Arctic.

The US will be a land of extremes as a high amplitude jet stream…the story of this winter continues to impact the US as very abnormally cold temperatures impact the Central US and (later) the Great Lakes region, with very abnormal heat spreading northward into the Eastern third of the country mid-week. Sunday, much of the Great Plains were experiencing temperatures 20-25 degrees F above normal (~10-12 degrees C). As the week progresses, the jet stream amplitude over North America will intensify and bring highs of 30 degrees F (15+ C) or greater above normal mid-week to the Ohio and Tennessee Valleys into the mid-Atlantic and New England states. This means mid-Spring highs on the East Coast and a resumption of well below freezing temps over the Central and Northern Plains.

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In addition to the abnormal temperatures, another major story will be potentially heavy rainfall across a wide swath of the Midwest and Deep South ahead of the accompanying cold front which will push eastward mid-week. Abundant moisture from the Gulf of Mexico will aid in the generation of rainfall, some of which will help short term drought conditions, but could also produce flash flooding.

Moderate risk of flash flooding over portion of Texas, Oklahoma, much of Arkansas and southern Missouri Tuesday.
Tuesday evening forecast surface map showing widespread moderate to heavy rainfall likely from Texas to Michigan.

The Arctic Ocean has been experiencing an extraordinarily warm winter with consistent high heat to the region (relative to regional norms). As a result, sea ice has been suffering severely as the combination of high amplitude high pressure ridging and ocean cyclones push heat, wave action and wind into the sea ice sheet, along with very abnormal sea surface temperature right up against the sea ice (9-18 degrees F/5-10 degrees C above normal). Sea ice extent is currently running at the lowest on record in the history of human civilization, rapid melting already in progress in the northern Bering Sea, and 2017 annual sea ice volume was the lowest on record. The current max extent this season occurred on February 6th. The current earliest maximum peak extent is February 25th in 2015. The current record year for record minimum peak extent is 2017…2018 is currently beating that record and has the 2nd lowest year-to-date volume as well.


The sea ice is showing some signs of refreezing after its early February peak. However, more extreme heat is to come as more storms from both the Bering Sea and the North Atlantic advance heat and moisture into the Arctic Ocean this week. One storm will move over far Eastern Siberia and into the Chukchi Sea on Tuesday. Wednesday, another, stronger storm will approach Greenland, moving over the Canadian Archipelago Thursday, slowly shifting toward the Beaufort Sea Friday.


Note the last two sea level pressure images for 2/23 and 2/24. Not only the strength of the cyclone (in blue) but the tightly packed lines of equal pressure (isobars) between the low pressure system and the strong high pressure system over the Barents Sea, north of Scandinavia. These tightly packed isobars represent a very strong pressure gradient which will result in very strong southerly wind gusts (near hurricane-force) and intense wave action striking the sea ice sheet of the Arctic Ocean mid to late week. This in combination with the very warm, moist air moving into the region will make for a “blow torch” of heat from the Atlantic, eroding the cold conditions of the Arctic, stunting the freeze season further. This will likely lead to further ceasing or recession of sea ice as well.

GFS forecast high temperature for Thursday, showing above freezing temperatures penetrating into the deep Arctic. This may continue into Friday. Today through Tuesday will feature near or above freezing temperatures moving out of the Bering Sea into the southern Chukchi Sea as well.

I’ve been tracking the Arctic all season and there has been a shocking level of persistent warmth in the region with 2-3 degrees C above normal temps (for the region) being quite common many more extreme day higher than that. The Arctic Ocean basin may experience, as a region, anomalous temperatures of an incredible 6-8 degrees C above normal Tuesday-Saturday. This is relative to the 1981-2010 average. However, as climate change is abruptly warming the Arctic region, leading to rapid sea ice loss compared to the past, relative to the late 19th and mid 18th centuries (in the early era of human generated climate change), the anomalies are likely 0.7 or 1  degree C higher than that, respectively.

GFS Anomalous temperature forecasts for the Arctic region valid 00 UTC Feb 23rd. Extreme heat by regional standards over the Arctic for much of the week.

The implications for the collapse of sea ice are quite serious. The sea ice sheet regulates the jet stream by making the Arctic region permanently cold across a wide area. As long it it remains permanent with only modest seasonal melt, it can behave much like a continental ice sheet would behave on the atmosphere (like in Antarctica). The jet stream exists because the Arctic atmosphere is cold throughout the vertical column. The strong temperature gradient with the mid-latitudes is what makes it exist. But with abrupt warming of the Arctic caused by the collapsing ice sheet (which feeds back on accelerating such a collapse), this weakens the jet stream and has been causing it to become wavier with increasingly more extreme and frequent high amplitude patterns (which feedback and melt the Arctic more). Such research has been conducted by scientists such as Dr. Jennifer Francis of Rutgers University and others, showing the jet stream slowing and becoming higher in amplitude since the 1960s. Such abrupt warming also leads events such as “sudden stratospheric warming” and “splitting” of the polar vortex, supporting Arctic blasts to the south and abundant heat transport to the Arctic.

If the ice sheet collapses completely (no more in summer, low to little meaningful extent in the polar night), you get even more abrupt warming of the sea surface from below and above through collapse of the ocean thermocline (persistently cold water “cap” atop somewhat warmer water) and air temperature inversion (warmer air atop cold surface air) as well as from the much reduced albedo (white, reflective surface). The warming atmospheric column with height further reduces the temperature gradient with the mid-latitudes, weakening the jet further and causing more extreme “wave action”, greater blocking patterns as you get these big waves and little eastward progression of systems and the polar jet actually retreats farther north. This can dramatically shift precipitation patterns northward could cause much hotter, drier conditions in the mid-latitudes. It’s been a major concern for a long time in in climate change science, but a process thought to be of concern in the “high emissions” scenarios of the mid to late 21st century as increasing aridity across the mid-latitudes would destroy forests and not allow crops to be grown where they are currently grown because of increasing extreme heat (or storms). So this would have impacts not only in the Arctic, but also in the mid-latitudes. Unfortunately, a recent phrase has been increasing use the past few years. “Faster than expected”. Some prominent researchers openly admit an ice-free Arctic may be possible before 2020. See also HERE.

I’ll have more on the situation in the Arctic this week as well as the heavy rainfall in the US. Also, keep an eye on Tropical Storm Gita approaching New Zealand to start the week!

–Meteorologist Nick Humphrey


Wild Ride – More Cold Intrusions into North America/Europe, Powerful Warm Storm Headed for Arctic Ocean Monday

This winter has been a fascinating one to say the least. Wild oscillations between very abnormally warm and very abnormally cold while other places are are just consistently very warm. Or perhaps just very dry. Much of this has been thanks to the current La Nina pattern in place over the Tropical Pacific. The atmospheric pattern leading to abnormally cooler waters over the eastern tropical region also lead to the promotion of strong high pressure systems over the Central North Pacific with unusually higher amplitude jet streams. This favors a polar jet aiming for the Pacific Northwest, northern tier and into the northeastern third of the country while the Southwest and Sunbelt see drier conditions.


Conditions of at least “Abnormally Dry” cover over 67% of the Continental US. It is the most coverage in abnormally dry conditions since February 5, 2013. It is, interestingly, the 49th greatest extent of at least Abnormally Dry conditions on record out of 944 recorded weekly updates (over 18 years now). Conditions of at least D1 “Moderate Drought” coverage over 38% of the Continental US. It is the most coverage in D1 conditions since April 22, 2014.

Of note with this pattern regime has been the, at times, extreme nature of the jet stream amplitudes. They have driven very warm temperatures into the Arctic with record low sea ice across the Arctic Ocean, the warmest December on record across the state of Alaska, and record high temperatures in portions of the Southwest US in January with the aforementioned persistent drying and intensifying drought concerns. 

Meanwhile, significant Arctic intrusions have been impacting the US, particularly in January and more appear likely in February as “teleconnections”…patterns in global circulation which give clues toward a general weather regime for a region of the world…show signs of further intense extreme jet stream amplitudes with very strong upper-level high pressure systems blocking storm tracks over the north Pacific and Bering Sea, which downstream will mean a cross polar flow in the upper atmosphere of very cold air upper troughs and surface Arctic fronts and high pressure systems over northern Plains/Midwest into the Northeast US. The Deep South should escape as warmer air from the subtropics attempts to advance north and may keep the Arctic air at bay. Europe looks to also have periods of similar cold (and interior Siberia of course! Check out the incredible cold they had last month).

Temperature Anomalies in the US (Sunday, Thursday) and in Europe (Monday). Widespread temps below freezing during the day in parts of central and Eastern US and central and eastern Europe during these cold periods. Very persistent warmth with highs in the 60-80s in the Southwest US.


Powerful Arctic Ocean Storm Sunday-Tuesday

While the mid-latitudes get hit with Arctic cold, the Arctic is being pounded by significant amounts of mid-latitude heat. And now the computer models are pointing towards a major North Atlantic storm developing early this weekend, moving over Greenland and then into the middle of the Arctic Ocean Sunday night-Monday. This storm will be very powerful…as strong as any classic North Atlantic ocean winter storm, and will bring significant amounts of high winds, battering waves and high “heat” to the Arctic. How warm? Perhaps as warm as 50-60 degrees F above normal temperatures over much of the Arctic Ocean. This will mean highs near or just above freezing up to the North Pole!

Temperature forecast by the Global Forecast System model for noon CST Monday showing near or above freezing temperature penetrating deep into the interior Arctic as a result of intense warm air advection.
A significant sector of the Arctic Ocean will have air temperatures over 40 degrees F above normal (or higher) during the day Monday.

This storm is forecast to initially form southwest of the tip of Greenland and east of Quebec Friday and will beginning moving over Greenland Saturday. Sunday, the system will begin to impact the Arctic, with warm and moisture transport from the North Atlantic (all the way from the Azores!) increasing abruptly late-Sunday. By Monday morning, models indicate waves moving up the Fram Strait toward the Arctic may be as high as 30 ft in strong south-southwesterly flow. Over the sea ice sheet, the low pressure system will be intense as it emerges from Greenland…possibly sub-960 millibars with widespread wind gusts of up to hurricane-force likely over much of the interior Arctic Ocean east and south of the low on the Atlantic side.

GFS depiction of the powerful low pressure system over the central Arctic Ocean on Monday. The European model has a similar strength low. Winds up to hurricane-force wind gusts and battering waves are likely conditions for the tenuous sea ice.
Forecast significant wave heights for early Monday with the worst of it in the Fram Strait.

Why this storm is so significant is because the Arctic sea ice is continuing to undergo collapse because of anthropogenic climate change. If the Arctic climate warms to the point that it simply cannot support sea ice in the warm season, with the Arctic Ocean warming as a result of very low albedo (reflectivity to visible light which would otherwise limit warming) compared to white ice (or latent heat of melting/freezing, instead of heat going into warming the ocean directly), this will have dramatic effects on not only regional climate but global climate (I can go into greater details in this in the comments or provide resources). Generally this was something expected much later in the future, but may occur earlier than expected, although it is difficult to predict when exactly this will occur as it would be nonlinear and abrupt. However, as mentioned, ice volume and extent for ice are running at record or near record lows across the Arctic Basin. Some of these effects on albedo and heating have already begun to be felt over the past several years on the marginal seas which are beginning to become increasingly ice free during the warm season (Chukchi Sea, Beaufort Sea, Eastern Siberian Sea), but it’s important to not have the interior Arctic Ocean lose significant ice. Particularly in the winter, but it has been struggling just to freeze this winter! For more on recent sea ice developments see these videos by Paul Beckwith (M.Sc, PhD candidate; HERE and HERE).

In the meantime, while we have year to year variability…various teleconnection patterns, anthropogenic forcing (CO2, other gasses) is the most dominant regime on our climate and so even while I must emphasize weather is not climate…I must also emphasize that climate is a statistical distribution of weather events; and so extreme weather events which are increasing in frequency and magnitude are a sign of our climate shifting to more extreme conditions and in sensitive places (particularly cold climates like the Arctic), those shifts are incredibly noticeable.

–Meteorologist Nick Humphrey

Major Pattern Change for North America and Arctic Next Week.

A major weather pattern shift will be occur next week for North America into the Arctic as the jet stream…which already has been largely higher in amplitude and experiencing some blocking with little eastward progression of long-waves in the upper-atmosphere, will becoming extremely amplified (north-south) next week bringing very warm air up into Alaska, Yukon and the Arctic Ocean and a modified Arctic air mass from Nunavut and the Northwest Territories of Canada into the central US. Let’s take a look at things.

The current pattern dominating North America has been strong ridge of high pressure over the Western US or Eastern Pacific with a prominent trough over the eastern US with some fluctuation in the wave pattern east or west, but not much significant change, except in the center of the country which has seen more significant swings between these two states. The east, including even the Southeast saw significant snow. The west has seen abnormal warmth with record fires in California. Currently the ridge of upper-atmosphere ridge is forecast by US and European models to build to an extremely high amplitude the end of next week north over portions of Alaska and Yukon and into the margins of the Arctic Ocean. This as a very intense trough is forced south over the US.

European model forecast for the wave pattern of the mid-level atmosphere valid 6 pm CST 12/23.
This extreme amplification will drive an Arctic surface air high pressure system out of the Northwest Territories with very cold air this week, with this air mass advancing into the US beginning Thursday into this weekend. Meanwhile stormier conditions will moving from the Bering Sea into the Chukchi Sea driving up temperatures in the far north. And California with all the fires? Remains abnormally warm and dry.

Temperatures the afternoon of Christmas Eve (European Model forecast).

Greatest signal for low to no precipitation the next 10 days is south-central to southern CA into much of AZ and NV.
The Arctic:

As I spoke about in a previous post, the Arctic is having its second warmest year on record and lowest annual sea ice volume on record as climate change continues to abnormally warm the Arctic. The highly amplified wave pattern is much a product of the current weak La Nina pattern. However, the intensity of the amplification and resulting amplified warming of the Arctic is also a function of the long-term global warming regime dominating the polar region and causing record warmth and reductions in sea ice. I noticed this amplified wave pattern will have interesting impacts on the Arctic weather pattern and possibly the tenuous sea ice beginning next week.

Right now, a prominent surface high pressure region…associated with the Beaufort Gyre…is over the Arctic Ocean north of Alaska and eastern Siberia. By the middle of next week, this gyre will weaken as strong low pressure systems approach the Arctic from both the Bering Sea and the far North Atlantic.

Prominent high pressure of the Beaufort Gyre over the sea ice of the Arctic Ocean.

European Model depiction of low pressure system advancing into the Arctic Ocean from the Bering Sea on Christmas Eve. This may be the strongest in a series of lows (2-3) beginning late week. Stormy conditions will also impact areas near Svalbard (islands just east of northeast Greenland) late-week and weekend.
The Gyre is vulnerable because of the areas of open water and tenuous sea ice which remains over the Chukchi Sea…record low extent for this time of year. The ice being cold creates the surface high pressure system and clockwise circulation. But last year, this gyre collapsed because of slow sea ice growth allowing for storms with warm, moist air to move into the Arctic and further slowed sea ice growth. It appears this may be forecast to happen again during the tail end of this month.

European Model forecast surface temperatures showing well above normal temps shifting northward late week into Christmas Eve over the Arctic Ocean north Svalbard and the Chukchi Sea. While exact values will change, general pattern appears likely.
Depending on the strength of the low pressure systems, not only will the tenuous sea ice in the Arctic…widespread areas 1.5 meters or less in thickness (less than a meter in the Chukchi Sea)…deal with more warm air temperatures limiting sea ice growth, but also wave action which may destroy the ice, particularly from the Pacific side as cyclones are expected to move across the Arctic from the Pacific. We’ll see how much impact those storms have and how intense they are. If the upper-level wave pattern is as amplified as forecast by models 5-8 days out (no reason to think otherwise as he reach the point of good reliability for the upper-atmosphere), it’s a good set up for strong low pressure systems to develop in both the North Pacific and North Atlantic. And with the highly amplified blocking high over the Eastern Pacific, storms will be forced to track into Alaska and into the Chukchi and Beaufort Seas and deep Arctic Ocean.

–Meteorologist Nick Humphrey

Very above normal temperatures dominating US to end November

Much above normal temperatures are dominating much of the United States right now. This is largely a product of a zonal or progressive jet stream moving along the northern tier states and southern Canada locking colder air over interior Canada and the Arctic (although, I note, the Arctic is seeing much above normal temperatures relative to what they should be seeing as well!).

My area…Eastern Nebraska…has been seeing many days of 60s and even mid-70s, including today. The average temperatures this time of year should be in the low to mid-40s for highs and near 20 for lows. Instead it’s been feeling like it’s around birthday time for me. My birthday is in May.

Global Forecast System model analysis of surface air temperature anomalies for November 27th. The GFS tends to have a minor warm bias from reality, but it is accurate is showing significant above normal temps over the western and central sections of the United States. The baseline normal period is 1979-2000, prior to the significant amplification of climatic warming in the Arctic (occurring because of anthropogenic global warming).
Global Forecast System model forecast depiction of upper-air wave pattern at 250 millibars (~10,200 meters/33,500 ft) valid Wednesday morning. The jet stream will remain largely over the northern tier and southern Canada this week with above normal temps of varying departures over the US.

As we move into the first week of December, trends point to some dip in the jet stream over the Western US early next week causing below normal temperatures. However, this will also amplify the jet stream over the eastern two-thirds, producing significantly above normal temperatures yet again.

One additional thing of note. Snow cover is virtually non-existent in the contiguous US today (Nov. 27th). Only 4% of the CONUS has snow cover today. Going back to 2003, this is lowest snow cover extent for this particular date. The second and third lowest for Nov. 27th were 8.7% (2009) and 10.2% (2011). The snow cover area extents on Nov. 27th in 2010, 2012-2015 were in the range of 20-35%. 2016 was fairly low at 15.4%. The data is available HERE.

Snow depth analysis map for the US and southern Canada for November 27, 2017.

I don’t know date prior to 2003, however it is known that climate change is reducing snow cover extent and depth in the US and the Northern Hemisphere beyond natural variability. The aforementioned trough in the West should increase that extent somewhat next week.

The Realities of Progress on Climate Change Discussed at COP23

I found this discussion forum posted on YouTube with Dr. James Hansen and felt the need to share. Hansen is known as the “father of global warming awareness” since his testimony on the problem before Congress in the late 1980s and frequent contributions in both peer-reviewed literature and as a science communicator to the general public. This talk was posted just today from the latest international climate talks (Conference Of the Parties-23 or “COP-23” in Bonn, Germany) dealing with getting down details behind the Paris Climate Agreement signed the world’s nations in 2015 to try to limit global warming below 2 degrees C (3.6 degrees F) relative to 1750 and preferably below 1.5 C (2.7 F).

Here is the video (by user Nick Breeze who reports on Climate Change issues and interviews scientists…check out his YouTube Channel, good stuff)…audio isn’t the greatest but it is still highly recommended if you care about this important issue.

In this discussion, Hansen pretty much lays out a major problem. With all the talks over the years, nothing significant has been done to significantly reduce emissions of greenhouse gasses into Earth’s atmosphere. He points out something which other notable climate scientists have pointed out: We have run out of time as far as waiting on attempting to prevent “catastrophic warming” as far as impacts (those impacts really pick up intensity past 1.5 degrees C…we are currently around 1.1-1.2 C over the past few years) and while there are efforts to create alternative energy solutions and research carbon dioxide removal from the atmosphere, the only viable way he sees to get nations off of carbon is for govts to force the cost of fossil fuels to reflect the harm it causes to ecological and human health (pollution, climate change, etc). He’s spoken about how this could be done to put much of the money back in the pockets of Americans in the American political context (where the greatest monetary loss would likely be to the rich with a huge carbon footprint). But having the true ecological and human cost of fossil fuels…and not just the benefit in terms of driving the common economic drivers…be added to the cost would allow much greater competitiveness in the energy industry vs. now where fossil fuels are still by far the cheapest energy available for a variety of reasons (relative ease to extract, transport, existing technology vs. building new). And with oil companies influencing govts around the world, it makes it very hard to see realistic change outside of the pledges or changes which seem significant but in the end do little good on a global scale.

Example…current Paris Agreement pledges would cause the global warming to reach at least 3-4 degrees C (5.4-7.2 F) by the last decades of this century. And there are risks of unpredictable “positive feedbacks” (some known, some unknown) such as, severe chronic Arctic sea ice loss in the summer months, mass diebacks of tropical and boreal forests or methane release from (shallow) submerged continental shelf permafrost in the Arctic Ocean which would accelerate global warming even more. Methane…a short-lived but extremely powerful greenhouse gas…has already been observed releasing at increasing rates in the East Siberian Arctic Ocean and Laptev Sea because of increasing ocean warming. There is also simply the possibility that Earth overall is more sensitive to carbon dioxide than originally thought (actual scientific paper HERE).

I made this blog partly for informing people about the realities of climate change as it is ultimately we who must make sound decisions and force our governments to do the same. These conferences and agreements are great (and obviously I disagree with President Trump’s position on the issue), but optics cannot be the only thing which comes out of all these COPs. We must have an evolutionary change in how we conduct business on our only habitable planet. There are means to turn the tide…but the political will (and money) have to be invested in actually doing it.

–Meteorologist Nick Humphrey

Biggest WxClimo Story of 2017…Wildfires.

Fires have been raging across the world this year with unprecedented scope. Major wildfire outbreaks have been notable from tropical rainforests in Africa and South America to the taiga of Canada and Russia. Even Greenland has seen an unusual amount of fire activity on the edge of the ice sheet. This year, Western North America, and the Iberian Peninsula of Europe have been particularly hard hit with life-threatening fires (see HERE, HERE, and HERE). Although fires occur every year with variable impacts, a significant upward trend can be tied to climate change allowing both natural and human activity to ignite and expand the destructive intensity of wildfires.

This video by Climate Central summarizes the impacts of these fires so far this year and their connection of climate change. This recent article by The Observer also summarizes fires around the world and the impacts of climate change.


(The featured satellite image above is from October 9, 2017 courtesy of the European Space Agency).

Global Climate Change and its Potential Connection to Hurricane Activity (cited research)

Because of recent North Atlantic Hurricane Season activity…many people have questioned whether hurricanes are becoming stronger and more numerous because of climate change. In the social media universe, I’ve seen many opinionated debates within the general public, as well as meteorologists and perhaps a few sprinkling of climatologist opinions here and there. Not to mention, interesting statements from non-climate scientists. What I have not seen much, however, is any discussion of peer-reviewed research on the topic. There’s so much knowledge being gathered every year by scientists trying to answer important questions about our past, present and future. How climate change will impact regional weather and climates is one of the most important questions because of potential impacts to people, agriculture and natural resources.

I decided to do a (very brief) search of literature on science’s current understanding of climate change as it relates to tropical cyclones. I looked into both the potential connection of global warming to these events in the current climate (attribution), as well as projections for these events based on the “business-as-usual” scenario for carbon dioxide emissions, which is a high emissions scenario and steady increase in CO2 concentration. Research cited are just a sampling of what’s out there and what I looked over. Here are some themes I found interesting (takeaway statements at the end):

Climate models* appear to show a signal toward more intense (Category 4-5 Saffir-Simpson) tropical cyclones overall in the world by the latter half of the 21st century. However, there is also a potential for a downward trend in cyclone numbers in many basins (see #1-4).

The decrease in overall cyclone numbers by the second half of the century is thought to be a product of increasing vertical wind shear over tropical oceans limiting weaker storms. However, many researchers expect there to be a significant upward trend in more intense storms (Category 4-5) as the oceans continue to warm and tropical cyclone formation and track density moves poleward. So formerly less favorable sub-regions of basins may see an overall increase in cyclone activity (with more storms which will be stronger than before in those regions) and in the increasingly less hospitable regions (over the long term), storms which do form when conditions are favorable on short time scales may see cyclones which are also more intense than in years past.

As for historical conditions leading to the present…there does not appear to be a conclusive signature by global warming on tropical cyclone intensity outside of natural variability on a global scale (3-4). However, some regional signals related to frequency changes are being actively studied. 

There is some suggestion (4) based on modeling past climate change to the present time that warming (which would enhance the potential intensity for hurricanes) has been muted by the industrial production of aerosols (particulates like sulfates and nitrates), which actually reflect sunlight from reaching Earth’s surface. However, as warming continues into mid-century, its effect of trapping heat will begin to significantly exceed aerosol cooling effects leading to the more pronounced impacts on cyclone intensity stated earlier (unless CO2 emissions are significantly reduced soon). So while global warming is happening in the background, hurricane potential intensity as we currently witness it is likely still being dominated by natural cycles. (For more on climate change research into tropical cyclones, you can also see this webinar done by climate change researcher Dr. Kerry Emanuel for Climate Central).

With that said, some researchers see signs of a global warming signature associated with recent increased tropical cyclone *frequency* in sub-regions of basins. These include the far eastern portion of the North Atlantic Basin (4), close to the East Asian Coast (5), and a portion of the North-Central Pacific Basin (6). Research is still ongoing on global warming’s past and future influence on activity in individual tropical cyclone basins.

Meanwhile, there is evidence of other impacts related to tropical cyclones (and other significant weather phenomena) and climate change. These include higher rainfall rates (7) and higher storm surge related to sea-level rise from the melting polar ice sheets and thermal expansion of the oceans (8). In addition, there is some scientific evidence that tropical cyclones in recent decades have begun to intensify more rapidly because of increased ocean warming (9). And while not completely clear yet whether it is fully tied to climate change, it is known that the observed North Atlantic Power Dissipation Index (PDI) has increased significantly since the mid-1970s (10; positively correlated to sea surface temperatures) and globally, the strongest tropical cyclones in respective basins have grown stronger since 1981 (Elsner et al, 2008…not included here). Note that scientific critics point out the use of observational data with differences in quality – satellite intensity estimates and reconnaissance flights (or lack of them) – over recent decades could put some uncertainty in these results.

My thoughts? Although inconclusive, possible intensity signals may be a hint of the projected effects of climate change as PDI and high-end cyclone intensity are highly correlated to sea surface temperatures. SSTs are increasing from global warming and this would connect with what climate models suggest of future tropical cyclone activity, if these historical trends are, in fact partially related to climate change.

The Takeaways:

  1. Tropical cyclone intensity at the highest end of the scale appears likely to increase through the 21st century because of climate change, especially if human civilization does not significantly reduce greenhouse gas emissions soon.
  2. While a current climate change signal to intensity is difficult to detect and still a matter of debate, storms in recent decades appear to be intensifying faster, are capable of producing more extreme precipitation events and higher storm surges because of rising sea levels caused by ice sheet melting and thermal ocean expansion. There also appears to be some detectable changes in frequency of storms within individual basins which may locally enhance risk.
  3. Regardless of the exact changes in frequency and intensity of tropical cyclones, the risks to individuals and society because of climate change will increase into the coming decades. It will be important for people and governments to make decisions (beyond greenhouse gas emissions) related to property, coastal land use and emergency management policy to mitigate increasing tropical cyclone hazards, particularly from water (storm surge/inland flooding).

Note: It is of EXTREME importance that those with a desire to communicate climate change issues try to inform our fellow citizens to the best of our ability. Climate change is one of the important issues facing our world (the impact on the global food supply and human health may be actually of greatest importance, but rarely discussed as those aren’t “sexy” topics…). People have their thoughts on the issue based on experiences, politics, religious/spiritual beliefs, etc. However, at the end of the day, we must inform and connect what we know to people’s concerns and allow people to decide as they may. Without censorship (“We can’t discuss climate change right now!”) or nonsensical exaggerations (“So many hurricanes, it’s a new era of superstorms!”). Stay informed (give informed opinions) and tell people why they should care as it relates to their lives. Like everything else we should communicate to the concerns of people. Considering most Americans are now, in fact, concerned about climate change, there’s really NO excuse not to discuss the issue in a serious, informed manner if we have the interest to discuss it at all.

Additional Note: *-Climate models are not weather forecast models. They do not forecast the atmosphere using initial conditions, but take a climate state (for example, our current climate) and adjust “forcings” on the climate system (carbon dioxide emissions for example). The effect of these changes to “boundary conditions” over time are interpreted for land, sea, the cryosphere and (for Earth System models), the biosphere. Global climate is based on thermodynamic and hydrologic balances which will look for equilibrium when changes to a part of the system are applied. (For more on climate models you can see this webinar by Research Meteorologist Keith Dixon of NOAA’s Geophysical Fluid Dynamics Laboratory for Climate Central).

References (links are PDFs):

#1 – Bell et al. (2013)

#2 – Murakami et al. (2011)

#3 – Wang and Wu. (2013)

#4 –  Sobel et al. (2016)

#5 – Cheng-lin et al. (2016)

#6 – Murakami et al. (2015)

#7 – Knutson et al. (2013)

#8 – Jevrejeva et al. (2016)

#9 – Kishtawal et al. (2012)

#10 – Emanual (2005)

—Meteorologist Nick Humphrey