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

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My view of the August 21, 2017 Total Eclipse.

 

What an amazing event! The moon’s shadow gave a big show across America today and at 1:02 pm CDT it rushed over Lincoln, NE at over 1500 mph. Day turned to night, the temperature dropped and a 360 degree twilight ruled the midday.

First…my video!

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Screen capture from video during totality in Lincoln, NE. Shows the “eclipse twilight” surrounding the city. Photo by me (Nick Humphrey).

The temperature in Lincoln dropped from 81 degrees around noon to 77 degrees after 1 pm and totality. Many locations along the eclipse path experienced temperature falls of 3-5 degrees as a result of the passage of the Moon’s shadow. Meteorologists also observed (both on the ground and with satellite imagery) the collapse of convective cumulus clouds dependent upon surface heating to “bubble”, which was lost during the advanced partial and total eclipses.

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Cumulus cloud field impacted by the eclipse. Cloud field (12:42 pm CDT) dissipates by 2:32 pm CDT as totality approaches. Photo courtesy of AccuWeather Meteorologist Becky DePodwin. Lowering of temperature weakens upward convection currents likely limiting maintenance of cumulus clouds and leading to their dissipation in the absence of other lifting mechanisms.

You can watch the progression of the Moon’s shadow across North America below (video is only four seconds long so you’ll have to replay to see it more than once at a time):

All I can say is that this was one of most spectacular events of nature I’ve ever witnessed. I’ve witnessed multiple total lunar eclipses and while they are spooky (especially in the middle of the night), nothing can beat the powerful changes which a total solar eclipse can bring to the landscape.

The clouds, which were the most problematic for eclipse viewing in Nebraska ended up breaking enough to see totality itself, but also provided a canvas for the incredible glow of midday twilight. It was quite magical.

The next total solar eclipse in the Lower 48 is April 8, 2024. Totality in parts of Texas (which will include Austin and Dallas/Fort Worth Metro) could last nearly 4 1/2 min compared to the 2 min 40 sec max with today’s eclipse. If time and finances align, I definitely want travel for that one if I don’t live near it by then.

Anyone have any eclipse experiences they want to share? I’ll be checking out WordPress posts too! 🙂

PS-A view from a Omaha news station of the twilight colors with clouds HERE (video) within totality near Beatrice, NE, south of Lincoln.

Category 1 Hurricane Franklin making landfall on the East Coast of Mexico

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Hurricane Franklin is making landfall on the East Coast of Mexico Wednesday night/early Thursday morning (~midnight CDT Thursday) with maximum sustained winds of 85 mph with gusts likely over 100 mph. Besides damaging wind gusts, very heavy rain – up to a foot or more – will be possible in the mountainous terrain once the system moves inland and weakens during the day Thursday.  Life threatening flash flooding and mudslides will be the greatest threats to any populated mountain areas (storm surge will be the hazard for coastal areas in the hurricane warning area tonight).


NOAA Raises North Atlantic Tropical Activity Forecast

The National Oceanographic and Atmospheric Administration raised its confidence today that the North Atlantic Basin would have an “very active” season. They called for 14-19 named storms, 5-9 hurricanes, 2-5 major hurricanes. A normal season averages 11 named storms, 6 hurricanes, 2 major hurricanes.

The reasoning for this activity forecast include 1) No El-Nino in the Eastern Pacific which would otherwise produce unfavorable vertical wind shear and cooler sea surface temperatures in the North Atlantic 2) Above normal sea surface temperatures across the Caribbean, Gulf of Mexico and Main Development Region (open tropical Atlantic) 3) The continuation of the Atlantic Multidecadal Oscillation favoring above normal oceanic heat content.

So far, we are at 6 named storms, 1 hurricane, 0 major hurricanes (assuming no surprise intensification of Franklin prior to landfall).

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

Hello Weather & Climate News readers! This post will be the first 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 (Causes)

This article will deal with an introductory explanation of Global Climate Change as we currently understand it and the causes of it, specifically relating to human activity. Part 2 (in the next week) will discuss the known (and unknown) impacts on humanity and wildlife based on impacts on regional climates. Part 3 (in a couple weeks) will discuss mitigation efforts.

  1. Natural Climate Variability vs. Recent Global Climate Change

Earth’s climate has been evolving since the planet was born 4.6 billion years ago. These changes in Earth’s atmosphere have been largely the result of things such as biological modification of the atmosphere, volcanic eruptions, changes in ocean currents, movement of continents over tens of millions of years, variations in Earth’s orbit and other various phenomena. The most recent history of climate has featured periods of glaciation over much of the landmasses known as the Ice Ages.

Earth’s global climate has been in a “interglacial” period with a climate which warmed enough to end major continental glaciation around 11,000 yrs ago.

However, what scientists have seen in the recent climate records is a rate of change -both the climate conditions themselves and the atmospheric gases which can change the climate – at a rate accelerated and in some cases unprecedented in previous times.

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Carbon Dioxide (CO2) levels going back 450,000 yrs. There have been multiple periods of glaciation and interglacial periods as part of natural change (high/low CO2 = warm/cold), but CO2 has not exceeded much above 300 parts per million until the 20th century. (NASA)

What scientists in the second half of the 20th century discovered is that for the first time in the history of human civilization we are acting as a force influencing the climate. Human-induced climate change is real.

This has been found after accounting for the natural variability in climate cycles and from our understanding of how carbon dioxide works in the atmosphere. This extremely rapid change in global temperatures, a top signal of climate change, has been driven by CO2 pollution, beginning after 1850 and the during the Second Industrial Revolution.

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Graph showing the correlation between global temperatures (anomaly relative to the 1881-1910 average) and CO2 concentration 1880-2016. CO2 is known physically to be capable of “trapping” heat in higher concentration. (Climate Central)

One of the first questions which many non-scientists have about global climate change is “Well hasn’t the climate always been changing?” The answer is yes, but with a caveat…it has NOT changed this rapidly in the history of humanity on Earth (Homo sapiens sapiens have been around ~200,000 yrs). Since Earth began the process out of the last glaciation 22,000 yrs ago, global temperatures have varied up to a 4 degrees C. But this process of variability has occurred over the course of centuries to a couple of millennia because of the long cycling of natural processes. Human activity in the form of burning fossil fuels since the latter 19th century has caused around 1 degree C of warming within a 100-150 yr period. This comic comparing the average temperature of Earth to the end of the Ice Age and achievements of human civilization across millennia strongly illustrate the climate stability we’ve come to flourish under. (zoom in at the top and scroll down…it’s long, but worth the read and look!). Humans have essentially acted as a continuously spewing ‘volcano’ of carbon products. And as a result, we have compressed warming which would take nature nearly a millennia to do in recent geologic time and accomplished it within a century.

We are transforming our world before our eyes.

2. How does the greenhouse effect work?

The greenhouse effect is a simple concept, but one with major implications for us all in this major environmental issue. In Earth’s atmosphere exists gases which are chemically capable of “trapping” heat in the lower atmosphere, heating the surface. The three most significant “greenhouse gases” are carbon dioxide, water vapor, and methane. These gases in higher concentrations are most effective in reflecting infrared (heat) radiation originally emitted by Earth’s surface back to the surface as opposed to allowing it to be lost to space. If it wasn’t for this greenhouse effect, Earth would be literally completely glaciated over and very cold.

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Example graphic showing the “radiation budget” and how the greenhouse effect impacts how much radiation is retained by Earth’s atmosphere. (By Wikipedia user ZooFari)

Methane is very potent, but short-lived without constant replacement as direct sunlight breaks the molecules apart. Water vapor varies seasonally with some balance because of the water cycle. Therefore carbon dioxide or CO2 ends up being the most important changing variable for warming/cooling the climate. Such changes, along with other variable cycles, have influenced previous periods of ice ages. But human “eruption” of CO2 since the 2nd half of the 19th century has led to clear changes in Earth’s atmosphere and climate.

This YouTube video shows 131 yrs of global warming (1880-2011). The “anomalous temperature” is relative to the average planetary temperature of 1880-1910. The average temperature of Earth has continued to warm above this average to record levels since 2011. The planet is known to have warmed by ~1 degree C (nearly 2 F) since the late 19th century. The most dramatic warming (as can be seen in the video) began to ramp up significantly since 1980. Depending on the scenario, human-induced warming of Earth may reach 1.5-2 degrees C (2.7-3.6 F) above pre-industrial levels by 2050 and (depending on human efforts to decrease CO2 pollution) the warming may hit 2-4+ degrees C (3.6-7.2+ F) by 2100.

3. The importance the rate of warming

Such rapid rates of warming are what alarms climatologists and those who understand the importance of climate stability for life and society on Earth. Remember the last time you saw a wholly mammoth, saber-toothed cat, wholly rhino, or an indigenous North American horse? Never because they all went extinct from the “rapid” climate change of the final end of the ice age glaciation 11,000 yrs ago. What’s “rapid”? Temperatures warmed more than 2.5 degrees C over the course of 1500 years. We may accomplish that in 150-200 yrs! Incredible. But yet the “rapid” natural changes were not non-consequential. Many more species than listed which couldn’t adapt died out over hundreds to a couple thousand years. And minor variations in global climate by 0.5 degrees C or less – or even significant regional variations which barely showed up on the global signature – have led to major losses in agriculture and economics producing stresses on some nations (poverty, famines, wars) and in some cases, isolated civilizations simply died out. Having such rapid, unprecedented warming is a cause for concern because too many species (and many socio-economic or geographically vulnerable peoples) may face significant harm in the face of an inability to adapt to transforming climate regimes.

In Part 2, later this week, I’ll discuss the effect climate change has on regional climates and likely impacts being faced by humans and wildlife as the climate continues to heat up extremely quickly.

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Is it a Heat Wave or a BBQ Pit? Fires Add Smoke to the Misery

It was VERY smoky in the Northwest Wednesday unfortunately because of major fires in the Interior US and Canada.

Satellite image of Washington State showing abundant smoke over much of Puget Sound and the Strait of Juan de Fuca Wednesday.
Photo from Seattle’s Lake Washington of the sunset view Wednesday evening through the thick smoke haze produced from Canadian fires. (Photo by NWS Seattle on Twitter)

BELOW were the highs Wednesday for select cities. Southwest WA and Western OR are being particularly hit hard by this heat wave. Interior Western WA and Puget Sound were actually sparred some of the worst of the heat today by the smoke; it was thick enough to act as a cloud to dampen the radiation and limit warming in places such as Seattle. It remains to be seen if that will be the case Thursday. If not, the hottest day if the heat may very well be Thursday for Western WA (and about the same for Western OR). This, along with an Air Quality Alert in effect for much of Western WA/OR means those in the area will need to not only be careful with strenuous activity to avoid heat-related illnesses, but also avoid breathing problems, if sensitive to such smoke particulates.

(record highs in red)

WASHINGTON

Seattle (National Weather Service Office): 88

Seattle (International Airport): 91 – Old Record 89 (2009). Special Note: Seattle also shattered its daily record for warmest minimum temperature with a morning low of 69 (old record was 61 set back in 2015) and it ranks as the 2nd warmest daily minimum temperature on record.

Olympia: 91

Hoquiam: 89 – Old Record 81 (1993)

Vancouver: 102

Quillayute (North WA Coast): 98 – Old Record 89 (1993). Special Note: This was likely caused by easterly downslope winds; easterly surface winds flowing along the higher hilly terrain descends down the slopes resulting in “adiabatic heating” (compression heating from increasing pressure on the air molecules as the flow drops in elevation). This hot air blows into town and shoots the temperature up fast. This process occurs throughout the region and is the reason why it is typically a “dry heat” in Western WA/OR during heat waves. The heated air becomes dry, with little moisture added to it.

OREGON

Astoria: 93 – Old Record 88 (1939)

Portland (International Airport): 103 – Old Record 96 (1986)

Troutdale (East Portland Metro): 105 – Old Record 99 (1995)

Hillsboro: 105 – Old Record 99 (1939)

Salem: 107 – Old Record 102 (1939)

Eugene: 102 – Old Record 99 (1939)

Medford: 112 – Old Record 105 (1993)

Klamath Falls: 99 – Old Record 94 (1977)

As you see, for Oregon, there was a major theme in the records for Wednesday’s climate stations. It was the hottest day many of these locations had seen on this date since 1939.

Please be safe if you live in this region the next couple of days. Drink PLENTY of water, take breaks from the heat as necessary, use fans if you don’t have air conditioning (common problem in this region, I lived there without air conditioning and the summers statistically are generally getting warmer because of anthropogenic climate change…), and again, like me, I have asthma; if you don’t need to do anything strenuous outside DON’T! Just drive instead of walk or just stay inside, cool and relax. The slightly cooler weather (still above normal, however) starts Friday.

Hilary and Irwin making plans for a Fujiwhara waltz over the open ocean

Let’s learn something cool about the tropics!

The past couple of weeks, the Eastern Pacific Basin has been quite active with multiple active tropical cyclones churning, dying and new ones forming. All while the North Atlantic Basin has been largely silent. We’ll get into the pattern set up for tropical activity between the two basins in the coming few weeks in a moment. But first, let’s discuss two interest systems in process in the EPac – Hilary and Irwin.

(Intensities are as of 4 pm CDT Thurs)

Hurricane Hilary is currently a Category 1 with max winds of 75 mph moving to the west-northwest. Meanwhile, ~480 nautical miles southwest of Hilary is Tropical Storm Irwin. It has max winds of 60 mph and drifting westward. Neither system is a threat to populated land masses and both are quickly heading for cooler waters north of the subtropical Pacific, where much drier air also exists in the mid-levels of the atmosphere. Both will lead to rapid deterioration of the cyclones this weekend.

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Visible satellite image showing Tropical Storm Irwin and Hurricane Hilary in close proximity at 4 pm CDT July 27, 2017. Cooler waters are noted to the north producing stable air mass near the sea surface, including deep marine stratus clouds and “closed cell” cumulus cloud deck. Stable air mass is non-conducive for thunderstorms hurricanes need to sustain themselves.
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Same image at same time as above in the “water vapor” infrared channel, where mid-level water vapor is detected. The circled area is a fairly dry area where air is experiencing sinking motions, coinciding with the cooler surface waters and the lack of thunderstorm activity for deep atmospheric moisture. Deep dry air can disrupt thunderstorm activity in tropical cyclones and weaken them.

Later Sunday and into Monday, an amazing phenomenon is expected to occur. Because of the very close proximity of Hilary and Irwin – only several hundred miles apart – the two cyclones are expected to undergo a Fujiwhara Interaction. This describes when two vortices in close proximity begin to rotate around a common center or one around another if one is more dominant. It is named after the Japanese meteorologist Sakuhei Fujiwhara who first described the interaction scientifically in a 1921 paper.

It does not happen very often, but it is typically more common in the Western Pacific basin where a very large surface area of favorable tropical development and maintenance exists and many cyclones can develop simultaneously and sometimes in close proximity.

Numerical models have shown the possible interaction for days.

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The slideshow above displays the Hurricane Weather Research & Forecasting Model forecast initialized at 11 pm PDT Wednesday with the forecast valid 5 pm PDT Sunday – 11 am PDT Monday. This model is “nested” on Hilary to show its evolution (the colors are surface temperatures in degrees C and wind barbs are in knots). However, you can see Irwin orbiting around it on its south and east sides Sunday evening – Monday morning. Irwin will likely weaken and die (along with Hilary, not long after), or will become absorbed by Hilary.

Nature never ceases to amazes in what it can do with the laws of physics!