Thomas Fire in Southern CA becomes 5th largest in state history; 230,000 acres and growing

The Thomas Fire of Ventura and Santa Barbara Counties in Southern California has now become (as of Sunday Night) the 5th largest fire in California State history. And based on trends and fire weather expected, it may go for the state record (273,246 acres).  After winds decreased somewhat Friday afternoon-Saturday, they picked up again on Sunday, causing extreme fire growth to an incredible 50,000 acres and reducing the containment from 15% to 10%.

Growth of Thomas Fire since last Tuesday’s ignition.
Since the fire developed last early-morning Tuesday, it has exhibited extreme fire behavior in intense Santa Ana winds with gusts of 45-80 mph, fanning flames and, more importantly, embers far downwind of the actual fire. Currently, 790 structures have been destroyed with the evacuation of over 88,000 people. A 70 year old woman died after being overtaken by the fire following suffering severe injuries in a car crash. In San Diego County, another woman was badly burned over 50% of her body in the Lilac Fire while helping horses escape from a thoroughbred training facility.  And speaking of horses…46 horses were confirmed killed at San Luis Rey Downs where the trainer was badly injured. The death toll will likely rise among the horses as 450 horses were there when the fire rapidly struck. Many burned to death refusing to leave their stables or running back into them, while others died from shock even after initially safely away from the fire’s path. Meanwhile, another 29 horses suffered a similar fate at a ranch in Los Angeles County’s Creek Fire.

Dry or low precipitation conditions expected in mid-range computer models (this forecast depiction by the Global Forecast System; GFS) for much the Southwest US and Great Plains through December 20th.

Forecast upper-atmospheric wave pattern valid noon CST Monday by the GFS. Powerful ridge of high pressure over the West will continue dry, very abnormally mild conditions while colder weather remains over the eastern US.
Unfortunately, high fire danger will continue through Monday with gusts over 45 mph allowing the Thomas Fire and any other fires which develop to easily spread and do so rapidly. Conditions should relax Monday night before possible re-intensification on Tuesday. As mentioned, the Thomas Fire may reach record territory tomorrow based on trends. And as of now, NO significant measurable rainfall is expected in California (or much of the Southwest US and Great Plains) the next 10 days. A blocking upper-atmospheric high pressure pattern over the Eastern Pacific will certainly allow for intensification of drought conditions and continued dryness and moderate to high fire danger for days to come. I should also note, fire danger will also be elevated on parts of the High Plains. Much of Eastern Colorado into Western Kansas are under red flag warnings for Monday because of expected elevated breezy conditions and low humidity with dry fuels.

—Meteorologist Nick Humphrey


First Game of World Series Tonight…Weather Headline: HOT

The World Series begins tonight in Los Angeles between the LA Dodgers and the Houston Astros. And it begins with record heat in Southern California. Today, in fact, downtown LA is setting a record high for the day and it is the warmest temperature on record for so late in the year. This was after a record high of 102 was set for downtown LA yesterday. So far it has reached 103 downtown and the official high may be higher before the day is done.

First pitch for the World Series is at 5 pm PDT this evening. While temperatures will decrease somewhat by that time, game time temperatures will be in record territory for a World Series Game (95-100 degrees F). The hottest World Series first pitch on record was from a game (cannot remember which) in 2001 in Phoenix when the NY Yankees played on the road against the Arizona Diamondbacks in a starting game temperature of 94 degrees.

In addition to heat, fire danger remains VERY high across Southern California as Santa Ana winds intensified today and will continue into tomorrow. RED FLAG WARNINGS are in effect for parts of SoCal. Gusts of 50-60 mph have caused problems for firefighters as they dealt with brush fires in Granada Hills this morning and Rancho Cucamonga this afternoon (LA Times). 

(Map of Rancho CucamongaMap of Granada Hills)

Game 2 of the World Series (First Pitch at 5 pm PDT Wed) should be slightly “cooler”, but still quite hot…expecting temperatures to start the game in the mid-90s (92-97 degrees F). If you’re going to these games or doing any outdoor activity at all in Southern California…lots of water and be careful with anything that sparks or burns!

US Global Forecast System forecast temperatures at 5 pm PDT Tuesday.

Enjoy the game! Go American League and go Astros!

–Meteorologist Nick Humphrey

WxClimoEd Series, Post #1, Part 2: Understanding Global Climate Change Indicators

Hello Weather & Climate News readers! This post will be the first (Part II) in what will be my ongoing education article series WxClimoEd. I hope to write educational posts on various topics related to weather and climate to help enhance your understanding of various phenomena and their impact on the environment, individuals and society. These posts will present key ideas and concepts and provide occasional linked sources to further, more detailed information.

Understanding Global Climate Change (Indicators)

In Part 2 of this article series on Global Climate Change, I’ll discuss the indicators of climate change in progress on  Earth. Even without the global measurements of temperature, there are plenty of signs in the climate system that change toward a warmer world is in progress.


Earth Undergoing Abrupt Climate Change

While global warming is considered to be detectable since the First Industrial Revolution (after 1750), since the latter half of the 20th century, the environment has begun to exhibit what could be considered “abrupt” changes. Among scientists who study natural abrupt change in the paleoclimate records have had some common thought on what “abrupt” means: 1) Changes in climate which can be witnessed within a human lifetime and 2) the change is very nonlinear; it far exceeds the mechanism which initiated the change in the first place (See this video presentation by Dr. White at the American Geophysical Union Annual Meeting discussing past abrupt climate change in the paleoclimate record). In the past, abrupt change usually occurred as a result of the advance or recession of ice sheets, leading to rapid change in local temperature or regional circulations (or even global distributions of precipitation or temperature patterns). Today, abrupt change is being increasingly witnessed as a result of an already unnaturally fast mechanism (rapid rise in carbon dioxide concentration, resulting in rapid rise in global temperatures relative to natural variability…multi-decadal to centennial  scales vs. multi-millennial).

Here are just some of  the abrupt changes resulting from the changing climate happening now:

  1. Decline in sea ice over the Arctic Ocean

Arctic Sea Ice Volume since 1979. Note gradual and accelerating collapse of sea ice volume. Arctic may fall below 1,000 cubic kilometers at some point in the month of September in as early as several years to a decade or so. This will begin the process toward widespread open ocean in the Arctic for a time in September.
2. Rapid increase in air temperature of the Arctic.

The Arctic (64-90N) has warmed around 3-4 degrees C since the 1881-1910 period (based on NASA data). 2-3 degrees C of warming has occurred just since the 1951-1980 period with notable warming since the year 2000. This has led to not only the rapid decline in Arctic sea ice, but the beginning the melting of land permafrost.

Average air temperatures (over land and ocean) in the Arctic region, relative to 1951-1980 average. Shown is 1984 (year I was born) to 2016. Red box show rapid warming of Arctic since 2000 compared to previous decades. “315” = +3.15 degrees C anomaly. (NASA GISS)
Addendum: The rise in the average temperature of Earth as a whole can count as abrupt, as seen in the earlier graph (farther back up). Most warming has occurred since the 1970s. The top ten warmest years on record going back to 1880 have occurred since 1998 (with 1998 now the last year in the top ten from the 20th century). 2017 is expected to be the 2nd warmest year on record just slightly behind 2016.

3. Increase in Sea Surface Temperatures and Oceanic Heat Content of Global Ocean.

The average sea-surface temperature of the global ocean from 60S-60N has risen around one degree C since the 1881-1910 period. 0.5 degrees C warming has occurred since 1980. Like the global air temperature, SSTs have been most of their record warm years since the turn of the 21st century, with an accelerated pace of warming since 2000 (1.62 degrees C/century currently, compared to 1 degree C/century 1950-2000). 2017 sea surface temperatures are currently running the 2nd warmest on record (NOAA data).

Sea surface temperature anomalies 1880-2016 for various sectors of global ocean. Values on graph are in degrees F. Oceans have warmed roughly 2 degrees F/1 degree C.
As far as oceanic heat content, the oceans have accumulated over 100 zetajoules (1 x 10^23 joules) of heat energy in the upper 700 meters of the global ocean since 1993. An incredible amount of energy, with increasingly accelerated warming in the deep ocean below 700 meters since 1993.

4. Acidification of the Global Ocean.

Earth’s seawater is slightly basic (basic is ph > 7). The global average ph of the oceans has decreased from 8.25 to 8.069 since the 1750s (ph was 8.104 in the 1990s). This is caused by the oceans dissolving carbon dioxide (30-40% of carbon dioxide released by humans dissolves in the oceans). This interaction forms carbonic acid, with further chemical reactions leading to increasing concentrations of the hydronium ion (H+). This leads to a lowering of the ph. The rate of acidifcation is faster than at anytime in the past 300 million years! The rapid acidification has been more pronounced in the Arctic Ocean because of very cold water (colder water can absorb more dissolved gases). When ph falls under 8 in the coming decades (assuming no mitigation), marine life which depend on carbonate structures (shellfish, sea snails, corals, some types of plankton, etc) begin to suffer from the corrosive effects of less basic waters.

5. Sea Level Rise


Sea levels are rising as a result of meltwater from land and thermal expansion as oceans warm. As the atmosphere and oceans continue to warm and weaken the Arctic and Antarctic Ice Sheets, sea levels will continue to rise, with possible nonlinear positive feedbacks accelerating it. It has already accelerated since the end of the 20th century. “King Tides” have become an increasing problem because of sea level rise in the 21st century.

6. Increase in Extreme Weather and Climate Events

The end of the 20th century into the early 21st century has featured a statistical increase in extreme weather events. Climatologists usually classify “extreme” as being 4-5+ standard deviations from the mean of all events. Such increase in extreme events over the course of years means that natural variability is being dominated by global warming, and causing a continuously shifting climate pattern.

The shift in the range of meteorological variables across the bell curve because of climate change. The curve represents the normal distribution of events with natural variability (climate teleconnections and seasonal). The small shift of the mean by climate change causes a significant increase in less common events at one tail as well as an increase in truly extreme events not previously observed in the reference climate regime. (Presentation slide by Erick Fernandes, 2015).
Extreme events include heat, flooding, rainfall rates, drought, and wildfires. All of these occurrences have been increasing the frequency and severity around the world because of climate change. In addition, there is evidence that because of the high rate of warming of the Arctic, the mid-latitude jet stream has become weaker with increased amplitude extremes, leading to short-term and longer-term patterns favorable for extreme conditions at the surface. For example, high amplitude ridges of high pressure which do not move much or reform constantly can lead to extended periods of drought and extreme heat (while other areas downstream may receive cooler temps but heavy rainfall and flooding. This is actually something that is observable on meteorological timescales. Dr. Stefan Rahmstorf discusses the increases in extreme events from climate change in a lecture HERE.

One thing I must emphasize with understanding the impacts of global climate change is that it is impacting the environments of our world now and continue to accelerate in the coming years and decades (assuming no major changes are done). Global warming…the primary force of climate change, caused by our immense release of greenhouse gasses from fossil fuels…is the dominate force behind the rate of change in climate behavior. According to the Intergovernmental Panel on Climate Change in their 5th assessment, the world should actually be experiencing anomalous COOLING right now, but instead we have warmed Earth above and beyond natural long term global temperature variability. So when people ask “Did global warming cause (insert extreme weather event)?”, it is the wrong question. Climate looks at a collection of events for a trend. What is clear is that global warming is NOW causing a statistically significant increase in extreme events and will continue to do so. There is no “new normal” but only a continuous “ramping up” of the Earth’s natural variability toward greater extremes relative to the beginning of the Industrial Revolution, with greater impacts as humanity leaves the stable global climate in existence since the beginning of civilization.

This may be something many do not appreciate, but it is factual. Human civilization has changed Earth’s climate system to the point that we as humans are turning up the “thermostat” and started a multi-centennial experiment in geoengineering. Heat, drought, flooding, rainfall rates, wildfire events, and jet stream amplitudes, as a result, have all increased significantly in just the past 30 yrs.

If the climate were a piece of music…think of Earth’s relatively short-term natural cycles as the melody and global warming as the dominating background harmony from which the melody plays over. If the harmony changes keys, the melody will respond and shift accordingly.

In Part 3, I’ll discuss the projected future impacts of climate change being actively researched (and some already happening) such as food security, human health and living space.

Surreal view…a major hurricane near Western Europe.

Incredible views today…

Hurricane Ophelia set two records: 1) The highest latitude major hurricane on record in the North Atlantic Basin, set beginning at 35.9 N and 2) the most easterly major hurricane on record in the basin, set beginning at 26.6W. It will likely weaken below major hurricane force by Sunday morning as it begins to undergo transition into a frontal cyclone from its interaction with the jet stream and further reduction of sea surface temperatures below 72 degrees F/22 degrees C. However, it will be one for the record books.

Fortunately, Ireland and the United Kingdom will not need to worry about a major hurricane hitting them. They will need to worry about a likely damaging windstorm from a post-tropical hybrid cyclone. The post-tropical incarnation will develop frontal characteristics as it initially weakens, but its strong inner warm-core will continue to release some heat into the system, re-intensifying it as it becomes fully embedded in the mid-latitude westerlies and races into Ireland and the UK Monday afternoon and evening. My updated forecast for Ireland is below. Still expecting winds capable of downing trees and causing major power disruptions. The forecast for intense winds is high in confidence as computer models hone in on the center of the storm either coming ashore the southern tip of Ireland or just grazing the western shore. This is favorable for a “big blow” over the entire island. Residents need to be prepared to stay indoors and stay safe during the day Monday.

Ireland Forecast for Post-Tropical Cyclone Ophelia:


Forecast zones (North and South) used for my forecast.


Monday Morning (After 7 am local time): For the southern half of the island, wind gusts of 40-50 mph (64-80 km/h) will develop during the morning, increasing to 60-85 mph (97-137 km/h) by mid to late morning from the coast, northward. The strongest gusts will be along the coastal areas, especially the south shores where isolated gusts may approach 100 mph (161 km/h). For the northern half of the island, wind gusts to 40 mph will develop mid morning , increasing to 50-60 mph late morning, from south to north.

Monday Afternoon (After noon): For the south, wind gusts of 60-85 mph (97-137 km/h) early afternoon with isolated to 100 mph/161 km/h along the south/southeast shores). For the north, wind gusts of 50-60 mph (80-97 km/h) early afternoon will increase to 60-85 mph by mid afternoon with isolated gusts to 100 mph along the northeast shores, spreading from south to north into the late afternoon.

Monday Night (after 5 pm local time): For the south, wind gusts will gradually decrease to 40-55 mph (64-89 km/h) during the early evening from south to north. For the north, wind gusts will gradually decrease to 40-55 mph during the mid to late evening (after 7 pm) from south to north.

Sea conditions will be hazardous all around Ireland with wind gusts in excess of 100 mph (161 km/h) likely in the south coastal waters and in the Irish Sea.

High-resolution Swiss model showing the tightly-packed circulation of then Post-Tropical Cyclone Ophelia reaching coastal Ireland midday Monday. Damaging winds will be spreading throughout the Irish Republic and Northern Ireland by this time. Shown for illustration of the overall forecast scenario.

Quick update on Northern California Wildfires (plus weather forecast)

As of now (5:30 pm PDT), the death toll in the California Wildfires is up to 35 and is expected to go up further. 18 in  Sonoma County, 9 in Mendocino County, 4 in Yuba County and 4 in Napa County. 5700 structures have been destroyed and 221,000 acres have been burned. Treating the conglomeration of fires as a single event (as all the Northern CA ones initiated Sunday Night), this is by far the most destructive fire event in state history and one of the deadliest. Simply horrifying and very sad.

Firefighters have begun to have some containment success the past 48 hrs with slower winds and at least some periods of slightly improved humidity. However, tonight-Sunday morning will feature an intensification of extreme fire danger. This is because a strong surface high pressure system will advance toward the central Intermountain West this weekend, intensifying downsloping Diablo winds from the hilly and foothill mountainous terrain of Northern California. North-northeast winds may gust as high as 45-60 mph Saturday, inducing very low humidity values, drying out fuels and potentially promoting extreme fire behavior (high forward speed, rapid growth) in existing fires as well as any new fires. Red Flag Warnings have been issued by the National Weather Service to cover this forecast potential.

Strong high pressure moving over OR, ID and NV Saturday will promote strong Diablo winds over Northern California. (NWS forecast surface map valid 11 am PDT Saturday).

There are no thunderstorms forecast, so any new fires would be likely started by human activity. So folks in these areas need to very much be careful with anything which can potentially start fire and really…just avoid starting any outdoor fire or using  anything which sparks.

Some good news…mid-range computer model forecasts suggest a pattern shift toward precipitation and cooler weather by the end of next week. Just have to get through the next week of fire activity before some meaningful hydrologic relief to aid the firefighting efforts.

The Global Forecast System Model forecast accumulated total precipitation valid 8 pm PDT Friday. This is one forecast scenario, but all global models point toward a wetter pattern, beginning the second half of next week into next weekend.

–Meteorologist Nick Humphrey

California Fire Crisis (Wed Updates)

Update at 11:15 pm PDT Wed:

The Wine Country Fires in Northern California have now destroyed over 3500 structures, making it the most destructive fire event in state history. And with 23 deaths now reported, it is quickly approaching the record for the deadliest. There are still areas burned where police have yet to search for potential victims because the primary operations are focused on evacuations and maintaining safety in the current fluid situation. Unfortunately, given that the missing persons are over 280, even with many being found safe, the death toll is still likely to go up as some are found.

Amazing the disturbing level of destruction of this fire event. I was only 7 yrs old in 1991, but I remember the Oakland Hills Firestorm, as it was plastered all over the news as much as this event. I didn’t think I could imagine such a disastrous fire worse than that.


Update at 5:30 pm PDT Wed: Update on the Meteorological Conditions in the Bay Area/Napa Valley Region.

Numerous fires continue to largely out of control over the Napa Valley/North Bay region. Heavy Smoke (with particulate matter >2.5 micrometers) is spreading southward over the Greater Bay Area reducing visibility and causing air quality to be considered very unhealthy for all individuals in the region with VERY UNHEALTHY conditions in the hilly terrain east of Santa Rosa and Oakland. If you can stay indoors, do so, especially for the young, elderly, and those with chronic breathing problems.


Particulate smoke (<2.5 micrometers) being produced by the fires and spread southward from northerly winds. This is causing very poor air quality across the state of CA. (

A RED FLAG WARNING REMAINS IN EFFECT FOR MUCH OF N. AND C. CALIFORNIA FROM NOW UNTIL TOMORROW AFTERNOON. As high pressure builds across Oregon into NE. Nevada, easterly downsloping winds will intensify the foothills across the interior of Northern CA, increasing the threat for any fires which develop to spread quickly and existing fires to expand acreage quickly. These winds will help maintain very conditions longer into the night, slowing humidity recovery and allowing fires to potentially exhibit extreme behavior (heat, forward speed, self-maintenance). Winds may gust up to 45-50 mph in some areas.

High-Resolution Rapid Refresh (HRRR) Model forecast for around 10 pm PDT showing the intensifying pressure gradient and pressure ridging over the hills and mountains of northern CA. This will lead to development and intensification of dry Diablo winds overnight.
The HRRR forecast valid for 1 am PDT showing widespread dew point temperatures in the mid-20s. With temps in the mid/upper-50s, this means humidity values in the 25-35% range, keeping fuels relatively dry for spreading fire in the face of 40-50 mph wind gusts near the foothills.

These fires have largely been a result of 1) the 5 yr extreme drought weakening trees 2) the very wet winter producing abundant brush growth 3) extreme hot, dry summer drying out all fuels.

New evacuation orders have already come out for some areas, including the City of Calistoga (northeast of Santa Rosa) where the entire town of over 5,000 are being told to leave. See the Impact Statement at the bottom of this post…but folks need to be ready to evacuate if necessary at a moment’s notice.

–Meteorologist Nick Humphrey


CalFire has updated news at 11:30 am PDT and now say 21 people have been confirmed killed and 172,000 acres have now burned across the entire state. The most destructive fires are in North-Central California north of the Bay Area, but the Canyon 2 Fire continues to menace Anaheim in Southern California.

A RED FLAG WARNING is in effect for much of the interior valleys and foothill terrain of California.

This is for extreme fire danger today – Thursday. As high pressure builds this evening and tonight over Nevada and east of the Sierra Nevada Mountains, a NE-SW pressure gradient will intensify, leading to strong downslope winds known as Diablo winds or Santa Ana Winds (the former in Northern CA, the latter in Southern CA). These winds will gust potentially 40-45 mph+. In addition, because they are downsloping, the air undergoes adiabatic warming…warming caused by the air compressing as it flows down toward higher vertical pressure at lower elevations. The air not only warms, but also dries out, turning winds blasting out of canyons into a hot blow dryer…drying out fuels and allowing a fire to turn into a firestorm.


I CANNOT STRESS ENOUGH…if you live in areas under the red flag warning or if you know anyone who lives in these areas, especially near the urban-wildland interface…please have a plan of what to do if a mandatory evacuation is ordered for your area and have a way to get warnings. ESPECIALLY AT NIGHT. Stay in contact with friends/relatives, have someone stay up to watch tv or listen to radio, keep your phone on and charged, have a weather radio. Most importantly, make sure those smoke detectors are working as they may be a final warning of danger impacting your home at night. These fires may intensify or new ones may start Wed night-Thurs morning because of strengthening winds and the humidity…which normally increases at night…may not do so because of the very dry nature of the winds. This will allow for potentially explosive fire behavior. And please, be smart with anything related to flammable materials and clear any brush away from your home if possible, to give you more time if a fire does approach.

I really hope the situation does not worsen significantly. Fires are scary events and incredibly destructive. Please be safe and be ready if you are in these areas.

I’ll have updates on this page throughout today and tonight.

–Meteorologist Nick Humphrey


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