I. Identifying Links Between Climate Change and Tornadoes?
The outbreak of recent killer weather events including US tornadoes hitting Joplin, Missouri and Tuscaloosa, Alabama has everyone asking whether there is a link between tornadoes and human-induced climate change. In this writer’s experience when US TV or radio weathermen are asked about the cause of recent strong tornadoes, they most always ignore climate change as a potential cause and point to a cyclical ocean circulation event known as La Niña as the cause of recent tornadoes if they comment on causation at all.
Rarely is human-induced climate change mentioned as a cause or contributing factor in the recent outbreak of sever tornadoes although questions about causation are becoming more frequent on TV and newspapers in this writer’s experience.
This post argues that ethics requires acknowledging the links between tornadoes and climate change despite scientific uncertainties about increased frequency and intensity of tornadoes in a warming world. However, because there are also scientific reasons to doubt that tornado propagation and intensity will increase in a warming world, as we shall see, care is necessary about how we should discuss these risks.
As we shall see there are certain aspects of atmospheric conditions necessary to produce violent tornadoes that climate change is enhancing while there are other atmospheric conditions necessary to form tornadoes about which scientists are uncertain exactly how a warming world will affect them. To figure out whether climate change will cause more intense and frequent tornadoes requires asking lots of smaller questions about the atmospheric conditions necessary to produce tornadoes and to determine how climate change will affect each of these various atmospheric conditions that combine to propagate tornadoes.
Before discussing tornadoes, it is important to note that it is scientifically uncontroversial to conclude that climate change is causing more violent weather particularly in the form of: (a) more damaging thunder storms, (b) the kind of devastating flooding we have seen this year in Australia, Pakistan, Brazil, Columbia, Venezuela, along the Mississippi and the Tennessee valleys, and (c) more severe droughts such as those experienced this year in China, Brazil, and Texas. Similarly more intense hurricanes have been linked to climate change although it is still uncertain whether global warming will increase hurricane frequency. (Emanuel, 2005)
Most climate scientists agree that future weather will be characterized by far more chaotic weather causing greater damage to human life, health and ecological systems and so tornadoes are not the only intense weather events that could be enhanced by climate change and that will likely cause increased damage and suffering. .
It also can be said that in one way climate change is already changing all global weather including tornadoes. This is so because climate change has already caused changes to the global climate system such as raising ocean temperatures and increasing the amount of water in the atmosphere. Increased ocean temperatures and the water content of air have an effect on the amount and timing of precipitation that is being experienced in any one location. And so a strong claim can be made that climate change is now at least partially responsible for all global weather although the part played by climate change could be small for any individual climate event relative to other causes such as normal ocean circulation patterns. Yet, no tornado or hurricane experienced recently would likely be the same without some contribution from climate change. That is no tornado would appear at the same place, the same time, with the same wind speed without changes to the climate system that have been caused by human impacts on climate And so every tornado is very likely affected somewhat by climate change. That is although strong tornadoes have occurred before recent human-induced climate change, no recent tornado is likely to have happened in the same way at the same place in the absence of global warming.
This is not to say, however, that the intensity and frequency of tornadoes will surely increase in the years ahead.. Yet, although it is not clear that climate change will be responsible for more tornado caused damages, other kinds of storm damages are virtually certain to increase.
This post, however, looks at links between tornado intensity and frequency and climate change and what ethics requires when discussing these links. That is, this post does not examine other links between climate change and damaging weather.
II. The Scientific Links
A. The Earth Is Warming Because of Human Activities
We know with high levels of confidence that the Earth is warming and that most of the warming is attributable to human activities despite the natural variability of thee Earth’s climate. Earlier this month, the United States Academy of Science issued its most recent report on the science of climate change that once again concluded that human-induced climate change was a very serious threat to humans and ecological systems around the world and that the Earth is getting warmer as predicted by mainstream climate change science. . This Report was entitled “America’s Climate Choices 2011” (US Academy, 2011) Among other conclusions, this report found:
Climate change is occurring, is very likely caused primarily by the emission of greenhouse gases from human activities, and poses significant risks for a range of human and natural systems. Emissions continue to increase, which will result in further change and greater risks. In the judgment of this report’s authoring committee, the environmental, economic, and humanitarian risks posed by climate change indicate a pressing need for substantial action to limit the magnitude of climate change and to prepare for adapting to its impacts. (US Academy, 2011)
That the Earth is warming is based upon many robust lines of independent evidence including temperature measurements of many different types of land, ocean, and atmosphere, diminishing sea ice, retreating glaciers, the timing of the formation and melting of river ice, the timing and aerial extent of snow cover, and the migration of plants and animals among other things.
There are also multiple robust lines of evidence of human causation of this undeniable warming that the Earth is experiencing that include multiple attribution studies, fingerprint studies based upon how the Earth would warm if greenhouse gases are causing the warming compared to how it would warm is climate change is caused by the sun, volcanic activity or ocean cycles, carbon isotope analyses that have demonstrated that carbon compounds appearing the atmosphere can be traced to fossil fuel burning, and model results that achieve the best fit between prediction and observation when both natural climate forcing and greenhouse gas climate forcing are combined. (Forcing means changes in heat energy from a baseline year.)
B. There Will Be More Intense Droughts, Floods, and Destructive Storms As the Earth Warms.
As the Earth warms, more water continues to be transported into the atmosphere under the forces of evapotranspiration. The global water cycle is believed to be at least 4% wetter from recent warming. As a rule of thumb, every 1 degree F in temperature will result in 4% more water in the air.
Basic physics predicts that increased warming and atmospheric water content will lead to increased droughts, floods, and intense storms. More droughts will be experienced despite more water in the atmosphere because the atmosphere will become more turbulent creating a propensity to discharge the water in stronger storms. Also as the Earth warms it will also more quickly deplete soil moisture in some areas therefore further intensifying drought conditions. And so, some places will get wetter and some drier and some places may cycle between drought and floods. The precipitation increases due to more water in the atmosphere under some conditions will include both more snow and rain. As a result, recent heavy snows are predicted by climate change theory despite somewhat counter intuitive notions that snow should decrease in a warming world. Of course, as temperatures continue to arise eventually snow will decrease in some areas.
C. Atmospheric Winds and Global Temperatures Will Be Affected and Weather Will Become More Violent As Oceans Warm.
Winds are caused by uneven heat causing differences in high and low pressures and pressure differences are caused by differences in temperature. Cold air is denser and exerts more pressure than worm air. Therefore increased warming changes global wind patterns. As one observer sums this up in regard to ocean temperature:
Heat exchange between the ocean and atmosphere drive atmospheric circulation over the entire planet and modifies temperatures and atmospheric wind patterns. Ocean surface currents play an important role by redistributing some of the heat the ocean absorbs and affect local weather patterns around the world. Understanding this complex relationship between surface ocean currents and weather is important to understanding global climate patterns and the changes that they are undergoing due to global warming. . .. The ocean-atmosphere system is a delicate balance between incoming and outgoing energy. If this balance is upset, even slightly, global climate can undergo a series of complicated changes. (Missouri, 2011)
Both an increase in water vapor and a rise in temperature will boost a metric that meteorologists use to forecast severe thunderstorms, known as Convective Available Potential Energy, or “CAPE.” A higher CAPE value indicates that there is more potential energy in the atmosphere to fuel thunderstorm development, should some trigger come along and set them off.
D. Weather Is Becoming More Chaotic As Predicted.
Not only is more chaotic weather predicted by climate change, it is actually happening. There is strong scientific evidence that “indeed the weather has become more extreme, as expected, and that it is extremely likely that humans are a contributing cause.” (Romm, 2011)
We also know that oceans are warming due to human activities and that warmer oceans both lead to higher levels of moisture in the atmosphere and more energy in the climate system. (Romm, 2011) Romm, quoting Dr. Kevin Trenberth, Senior Scientists with the Climate Analysis Section of the National Center for Atmospheric Research describes the evidence of how recent temperatures rise in the oceans has affected storms.
The SSTs (Sea Surface Temperatures) in the Gulf have been running perhaps 2 deg F above pre 1970 values. Warm waters also extend across the tropical Atlantic north of the equator in the region favored for hurricanes, and hence the recent NOAA forecast for an above average hurricane season (although the La Nina is fading and will likely be over by August, so there may be more competition from the Pacific).
Of those 2 def F, 1 can be assigned to human influence. With 1F increase in SST there is 4% increase in water holding capacity over the oceans and hence in this case the plentiful supply of moisture means there is likely to have been 8% increase in moisture flowing in the southerlies into the warm sector, thereby acting as fuel for the thunderstorms, and thus increasing the likelihood they would become super cells, with the attendant risk of tornadoes. And of course heavy rains. In spring the westerly jet stream aloft and southerlies at the surface create a wind shear environment that is favorable for tornadoes as the wind shear can be turned into rotation. This part of the situation is largely in the realm of weather. The climate part is the warmth and moistness of the air flowing out of the Gulf and the resulting very unstable atmosphere. So while a big part of that is natural variability, a substantial part was anthropogenic global warming.
These changes are making the weather more violent . In fact a believed contributor to the recent severe weather is an unusually warm Gulf of Mexico, where sea surface temperatures are running 1 to 2.5 degrees Celsius above average. (Freedman, 2011) The Gulf is the main moisture source for storm systems as they move east from the Rockies, and the additional moisture is helping to fuel thunderstorm development.
E. Tornadoes are Caused By A Combination of A Certain Type of Atmospheric Instability and Wind Shear
Tornadoes are caused when certain atmospheric temperature conditions exist along with certain wind conditions.
Tornadoes form in unusually violent thunderstorms when there is sufficient (1) instability and (2) wind shear present in the lower atmosphere. Instability refers to unusually warm and humid conditions in the lower atmosphere, and possibly cooler than usual conditions in the upper atmosphere. Wind shear in this case refers to the wind direction changing, and the wind speed increasing, with height. An example would be a southerly wind of 15 mph at the surface, changing to a southwesterly or westerly wind of 50 mph at 5,000 feet altitude.
This kind of wind shear and instability usually exists only ahead of a cold front and low pressure system. The intense spinning of a tornado is partly the result of the updrafts and downdrafts in the thunderstorm (caused by the unstable air) interacting with the wind shear, causing a tilting of the wind shear to form an upright tornado vortex. Helping the process along, cyclonically flowing air around the cyclone, already slowly spinning in a counter-clockwise direction (in the Northern Hemisphere), converges inward toward the thunderstorm, causing it to spin faster. This is the same process that causes an ice skater to spin faster when she pulls her arms in toward her body.
(Weather Questions 2011)
And so tornadoes form when warm moist air collides with cold air that is moving at a different direction and speed under certain conditions. For this reason, the two main ingredients for tornado formation most often quoted are atmospheric instability and wind shear.
F. There Is A Likely Connection Between El Niño and La Niña and Tornadoes.
El Niño and La Niña are extreme phases of a naturally occurring ocean climate cycles referred to as El Niño/Southern Oscillation. Both terms refer to large-scale changes in sea-surface temperature across the eastern tropical Pacific. (Weather Almanac, 2011) Usually, sea-surface readings off South America’s west coast range from the 60s to 70s°F, while they exceed 80°F in the “warm pool” located in the central and western Pacific. Weather Almanac, 2011) This warm pool expands to cover the tropics during El Niño, but during La Niña, the easterly trade winds strengthen and cold upwelling along the equator and the west coast of South America intensifies. (Weather Almanac, 2011) Sea-surface temperatures along the equator can fall as low as 7°F below normal during La Niña. Both La Niña and El Niño impact global weather patterns. (Weather Almanac, 2011)
The scientific community has identified at least a weak correlation between El Niño and La Niña ocean circulation patterns and the frequency of tornadoes. As the US National Weather Service has recently concluded:
Since a strong jet stream is an important ingredient for severe weather, the position of the jet stream helps to determine the regions more likely to experience tornadoes. Contrasting El Niño and La Niña winters, the jet stream over the United States is considerably different. During El Niño the jet stream is oriented from west to east across the southern portion of the United States. Thus, this region becomes more susceptible to severe weather outbreaks during La Niña. During La Niña the jet stream and severe weather is likely to be farther north.
(Weather Almanac, 2011)
G. Evidence Exists That Climate Change Is Affecting the Intensity and Frequency of El Niño and La Niña Events.
Although the jury is still out over how climate change is affecting El Niño and La Niña events there is increasing evidence that climate change is already affecting the frequency and intensity of these ocean circulation cycles. According to Kevin Trenberth, a senior climate scientist with the National Centre for Atmospheric Research (NCAR):
There have been changes in the El Niño-La Niña cycle since the 1970s. It’s a complex cycle but the associated droughts, flooding and other manifestations have been stronger over the last 30 to 40 years……It would be surprising if there wasn’t an effect [between climate change and the strength of El Niño-La Niña cycles] .
(Leahy, 2011, quoting Trenberth)
Since climate change has fundamentally altered the global climate system, trapping more heat and about four percent more water vapor in the atmosphere, it is reasonable to conclude it is affecting the has affected the El Niño and La Niña cycle. For these reasons climate scientists believe a warming world may be increasing the intensity and frequency of these ocean cycles. If La Nina’s are increasing from climate change, it is reasonable to conclude tornado propagation will be affected.
III. Not All Atmospheric Conditions Required For Tornado Generation Will Necessarily Increase In A Warming World.
In order for tornadoes to form, several factors have to combine in just the right way. (Freedman, 2011) These ingredients include a warm and humid atmosphere, strong jet stream winds, and atmospheric wind shear (winds that vary with speed and/or direction with height), as well as a mechanism to ignite this volatile mixture of ingredients – such as a cold front. (Freedman, 2011). Neither trend data on tornado propagation nor our understanding of future atmospheric conditions as the Earth continues to warm allow strong predictions on the number and intensity of future tornadoes in a warming world. Some of the reasons for this uncertainty is as follows:
A. There is No Trend Data Supporting Greater Tornado Production Over A Long Enough Time To Draw Conclusions About Future Tornado.
There is no clear indication that severe thunderstorms and tornadoes have become more common due to climate change, in part because of major limitations in relying on the historical record of severe weather reports. (Freedman, 2011) While the number of tornadoes recorded in the U.S. has just about doubled during the past 50 years, the number of strong tornadoes (EF2 and above) has actually been decreasing. (Freedman, 2011) It may be the case that more tornadoes are being noticed today, given a network of trained storm spotters and a national Doppler radar network, both of which didn’t exist as recently as the early 1980s. (Freedman, 2011)
The Joplin tornado is the deadliest since modern record keeping began in 1950 and is ranked 8th among the deadliest tornadoes in U.S. history. (NOAA, 2011) Preliminary estimate is that there have been approximately 1,314 tornadoes so far this year. (NOAA, 2011). The previous yearly record number of tornadoes was set in 2004 with 1,817. (NOAA, 2011). The overall yearly average number of tornadoes for the past decade is 1,274. (NOAA, 2011) The preliminary estimated number of tornado fatalities so far this year is 512. (NOAA, 2011). There were 365 tornado fatalities before the Joplin event. There were 132 fatalities from the Joplin tornado. (NOAA, 2011) An additional 18 fatalities were reported for a tornado outbreak on May 24, 2011 (NOAA, 2011). 2011 is preliminarily ranked 7th among the deadliest tornado years in U.S. history. (NOAA, 2011)
And so trend data is inconclusive in regard to how climate change may be affecting tornado propagation. There appear to be more tornadoes recently but not necessarily stronger or more deadly tornadoes. Most likely it will be decades before sufficient trend data will emerge that allow scientists to what extent a warming world is affecting tornadoes in frequency and intensity. A warming world could increase frequency but not intensity or increase intensity but not frequency or have little affect on tornado propagation.
B. The Relative Strength Of Cold Fronts Could Be Reduced in A Warming World.
Because cold fronts colliding with warm moist air masses are optimal for tornado production, it is not clear what happens to tornado production as differences between artic and tropic temperatures decrease in a warming world. A warming world could actually reduce differences betweem Earth’s cold spots compared to warmest parts of our planet. Because tornadoes are propagated when warm moist air collides with cold air, future frequency of tornadoes are in question despite a warming world.
C. As the Planet Heats Up, Wind Shear May Not Increase.
Some modeling studies indicate that a warmer world may also have less wind shear, which is necessary in order to transform ordinary thundershowers into organized squall lines and supercells, capable of dropping large hailstones, producing damaging straight line winds, and spawning tornadoes. (Freedman, 2011) And so, if a warming world produces less wind sheer, tornado intensity and frequency may actually decrease as the world experiences other increased weather caused damages. It will take years if not decades before models can predict wind sheer. As one commentator has noted:
It will take years or even decades to build the scientific models that would allow us to actually attribute individual weather events to manmade global warming. This will be even tougher with tornadoes, where the historical records are less well understood than other extreme weather events. (Walsh, 2011)
And so it is possible that average frequency and intensity of tornadoes decrease in warming world. Only time will tell.
IV. The Ethical Obligation To Discuss Tornado/Climate Change Links Despite Scientific Uncertainty.
And so, as we have seen, there are scientifically sound reasons to conclude that as the world heats in response to human activities tornadoes will increase in intensity and/or frequency. That is there are both scientifically sound theoretical basis for linking increased warming with more frequent and intense tornadoes and empirical evidence supporting the theory. Yet there are some theoretical reasons for being doubtful that tornado activity will increase in frequency and intensity in a warming world and insufficient trend data to draw conclusions at this time. Yet, it is very likely that storm damage will increase in a warming world because of human activities but it is not clear that this increase in damages will be caused by increased tornado activity.
Because of the complexity of the climate system and the need to predict atmospheric conditions at specific locations to be able to predict future tornado activity, it is unlikely that strong proof about the causal connection will emerge in the near future. Compelling proof would require a much better understanding of how the timing and magnitude of local atmospheric conditions will change than our current modeling capability allows or decades of experience with tornado formation to be able to establish credible trend data.
And so, in summary, when it comes to tornadoes and climate change there is reason to believe that tornado caused destruction will increase due to human induced climate change and also reason for doubt.
Many commenting on the connection between climate change and destructive tornado equate the lack of proof with the lack of any scientific evidence. In so doing they are implicitly claiming only absolute proof counties as evidence. Yet, as we have seen, it would be untruthful to conclude there is no scientific basis for connecting climate change to more damaging tornadoes. Climate change will clearly enhance certain atmospheric conditions that should lead to more intense and frequent tornadoes while possibly diminishing others. Evidence of a connection exists despite lack of conclusive proof.
We also know, that any tornado that greatly harms people in a specific place and at a specific time would not likely have happened at that place and time without climate change because climate change has already changed aspects of the climate system so as to influence where and when tornadoes will form and with what intensity. That is although killer tornadoes may have formed in May of 2011 somewhere in the United States without climate change, the tornadoes experienced in Joplin and Tuscaloosa would not likely have formed at the same exact time and place in the absence of climate change because climate change has already transformed the initial conditions which trigger tornadoes. When and where a tornado is generated is dependent upon initial conditions and climate change has changed initial conditions around the world.
As Bill McKibben has stated there is now no place on Earth that is now unaffected by climate change and human activities. (McKibben, 1989). As a result all tornadoes have been affected somewhat by global climate change although tornado frequency and intensity need not have increased.
In a warming world it is possible that for some time periods tornado activity may increase while decreasing in other periods. Yet is not truthful to claim there is no connection between climate change and tornadoes because all weather events are being affected by climate change and some of the atmospheric conditions needed to propagate tornadoes have been enhanced by climate change . Yet it is not proven that tornadoes will in general increase in intensity and frequency.
It would appear that many weatherman and the media claim that there is no connection between climate change and tornadoes because of the absence of proof of increases in tornado frequency and intensity from climate change. Yet it is simply not true that there is no scientific basis for being concerned that tornado damage may increase as human activities warm the planet. And so it is untruthful to say that there is no evidence of a connection although truthful to claim there is no proof of increased intensity and frequency of tornadoes.. That is, it is truthful to claim that there is no absolute proof that climate change is causing more intense and frequent tornadoes. Yet it is not true to claim that there is no evidence of scientific links between climate change and tornado damage.
Given this, a strong case can be made that when talking about the connection between climate change and tornadoes there is a duty to warn people of the possible connection even in the absence of absolute proof once it is established scientifically that behavior causing climate change is increasing the risk of harm from tornadoes. This is particularly true in cases when waiting for the proof will make it too late to avoid the harm from risky behavior.
To fully understand this it is helpful to understand why climate change is essentially an ethical problem. Climate change is an ethical problem because: (a) Some people in some parts of the world are putting others at risk, (b) The harms to those at risk could be catastrophic, and (c) Most of the victims of climate change can do little to avoid harm, they must rely on a sense of justice will motivate those who are putting others at risk to reduce their climate changing causing behavior.
For this reason, since we now know that it is scientifically plausible that tornado frequency and intensity will increase as the world warms and climate change is already affecting timing, location, and intensity of tornadoes that will form, it is not ethically acceptable to assert there is no link because such a claim implies that there is no scientifically valid basis for concern or risk. To understand why this it is ethically problematic to deny evidence. it is necessary to review the ethics of dangerous behavior.
From a proposition that a problem like global warming creates a particular threat or risk, one cannot, however, deduce whether that threat is acceptable without first deciding on certain criteria for acceptability. The criteria of acceptability must be understood as an ethical rather than a scientific question. For instance, although science may conclude that a certain increased exposure to solar radiation may increase the risk of skin cancer by one new cancer in every hundred people, science cannot say whether this additional risk is acceptable because science describes facts and cannot generate prescriptive guidance by itself. The scientific understanding of the nature of the threat, of course, is not irrelevant to the ethical question of whether the risk is ethically acceptable, but science alone cannot tell society what it should do about various threats. In environmental controversies such as global warming where there is legitimate concern, important ethical questions arise when scientific uncertainty prevents unambiguous predictions of human health and environmental consequences. This is so because decision-makers or those engaged in risky behavior cannot duck ethical questions such as how conservative “should” scientific assumptions be in the face of uncertainty or who “should” bear the burden of proof about harm. To ignore these questions is to decide to expose human health and the environment to real risk before changing the risky behavior, that is, a decision to not act on a serious environmental threat has serious potential consequences. Science alone cannot tell us what assumptions or concerns should be considered in making a judgment about what to do about potentially dangerous behavior. This is an ethical question. And so from the standpoint of ethics, potential risks are relevant to what should be done.
For this reason, environmental decisions in the face of scientific uncertainty must be understood to raise a mixture of ethical and scientific questions. Yet, the scientific skeptics on global warming or those denying connections between tornadoes and climate change often speak as if it is irrational to talk about duties to reduce greenhouse gases until science is capable of proving with high levels of certainty what actual damages will be.
That only proven facts should count about dangerous behavior can be shown to be ethically problematic by looking at how societies often deal with other kinds of unsafe behavior. For instance, many societies make dangerous behavior criminal such as dangerous driving, irresponsible use of hazardous substances, and negligently setting fire to a forest. Many social norms about dangerous behavior can be found in various cultures that recognize that burdens of proof and quantity of proof should shift depending upon what is at stake, who has been harmed, whether society can wait until the uncertainties are resolved, whether those harmed by the decision have consented to be put at risk. In other words, when the burden of proof should shift to those proposing to do something dangerous or how much proof should satisfy the burden of proof are ethical questions that need to take into consideration many different factors. Because these are ethical questions, they cannot be answered by an algorithm or a “value-neutral” scientific calculation. That is, there is no escaping asking the question what is the right thing to do given the uncertainty about links between tornadoes and climate change.
Because scientists are expected to produce scientific knowledge that can be applied to public policy questions, they must be able to describe threats that are not fully proven. From the standpoint of public policy, therefore, scientists should not deny that climate change creates risks of increased damage from tornadoes. A claim that there is no link between climate change and tornadoes is misleading. If someone is concerned about whether to adopt policies reducing the threat of climate change they need to know whether climate change creates risks of damage from tornadoes even if there are open questions about what happens to tornado frequency and intensity in a warming world.
In other words, when science is applied to public policy where there is reasonable basis that some human activity is dangerous, science has an important role in communicating any scientifically plausible dangerous risks-not just proven facts.
As long as anyone is asking the question of whether there is a link between climate change and tornado damage because they want to know whether there is reason to limit greenhouse gas emissions, it is therefore ethically problematic to say there is no link
However, it is also ethically required to acknowledge that increased tornado damage and frequency are not yet proven. When talking about these risks it is important to acknowledge that there is also scientific basis for doubt about increased tornado and frequency in a warming world. However, if this said, it is also ethically important to acknowledge that increased damage from other kinds of storms is virtually certain as the planet warms. Furthermore, it is ethically important to acknowledge that tornadoes will appear in places that they would not likely occur in the absence of global warming even if tornado frequency and intensity decrease because a changing climate is already affecting tornado propagation.
Emanuel, K. 2005. Increasing Destructiveness Of Tropical Cyclones Over The Past 30 Years. Nature 436:686-688.
Freedman, Andrew, 2011, Are La Nina and Global Warming Behind the Extreme Tornado Activity?, Washington Post,
Leahy. Stephen, 2011, Climate Change Could Be Worsening Effects of El Niño, La Niña, http://stephenleahy.net/2011/01/12/climate-change-could-be-worsening-effects-of-el-nino-la-nina/
McKibben, Bill, 1989, The End Of Nature, Random House
Missouri Department Of Natural Resources, (Missouri) 2011, Global Climate Change: Oceans’ Effect on Climate, http://www.dnr.mo.gov/energy/cc/cc4.htm
NOAA. 2011, 2011 Tornado Information, http://www.noaanews.noaa.gov/2011_tornado_information.html
Romm, Joe, 2011 Joplin Disaster Spurs Media Whirlwind On Link Between Climate Change, Extreme Weather, And Tornadoes, Climate Progress, http://climateprogress.org/2011/05/24/joplin-media-link-between-climate-change-extreme-weather-and-tornadoes/
US National Weather Service, 2011. Frequently Asked Questions About El Niño and La Niña , http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuff/ensofaq.shtml#HURRICANES
US Academy of Sciences, 2011, America’s Climate Choices (2011), http://dels.nas.edu/Report/Americas-Climate-Choices/12781
Walsh, Bryan, 2011, Why the Argument Over Climate and Tornadoes Is Pointless, Time Magazine, http://ecocentric.blogs.time.com/2011/05/26/why-the-argument-over-climate-and-tornadoes-is-pointless/
Weather Almanac, 2011, El Niño & La Niña, http://www.weatherexplained.com/Vol-1/El-Ni-o-La-Ni-a.html
White, Robert, 1978, Oceans and Climate -Introduction, Oceanus, 21:2-3
Weather Questions, 2011, What Causes A Tornado, http://www.weatherquestions.com/What_causes_tornadoes.htm
Donald A. Brown
Associate Professor, Environmental Ethics, Science, and Law,
Penn State Univesity
Thank you for clarifying the obligation of scientists to issue warnings beyond the traditional constraints.
Ethics issues are raised by this post, but not of the type posited by the author, who seems to have staked out the following view: regardless of whether tornadoes increase or not, scientists have a “duty” to draw a linkage that fits the author’s world view. I could cite the published studies regarding why weather is not climate science; I also could cite literature regarding the duty of a scientist, but won’t in the interest of time. The scientific method, however, involves the establishment of a hypothesis, then the collection of data to test the hypothesis. I’d suggest that it is unethical — and misleading and dishonest in the worst kind of way — to suggest another approach. But I guess when one is convincced of one’s views, science be damned, ethics are to take a back seat, too.
Mowrey Meezan Coddington Cloud LLP
Thank you so much for putting voice to the connection of ethics and science.
When we accept human induced climate change, then we look for our causation role.
We are all culpable: when we emit CO2 directly, when we permit emissions, and finally by refusing to demand change or regulation. Public policy sets down our future, yet we are passive.
Our actions started this, perhaps without intention. But intentional lying, cultivated ignorance and colossal denial have pushed us deeper into our irrational blunder. But now our acts can mitigate. We may elect to feel no shame for our past, but we directly harm others with our future acts and inaction.
Climate models say the future will be painful and bleak. No longer is this a distant future, our children and grandchildren will suffer greatly – and with increasingly rapid change, we will suffer too.
Any further CO2 emissions become attacks on the future. In one sense it is the equivalent of child abuse. Do we stop the abuser? Do we shout out and point out the perpetrator? We don’t tolerate child beating, sexual abuse, slavery… yet we tolerate the infliction of a far worse fate. Few of our children will have a future as safe and secure as ours.
Just because we are to blame, does not give us an escape. As if the largest possible group – our generation – by inflicting harm on the largest possible human group – our entire species, that somehow we may be forgiven or ignored.
What is the ethical duty after realizing the scientific mechanisms? We ignore or discount this so that we can the continue to enjoy the benefits of carbon combustion. We think it is cheap and convenient. And we do not want to face the difficult change of giving it up.
Another dangerous psychological coping mechanism will be to deny that we can possibly mitigate. i.e. “we may have caused it, but we cannot cure it.”
The horror of this ethical mess is that we set down the ethical style of the future. With so much suffering ahead – predictable famines, climate refugees and flooding victims – the survivors will be well practiced at ignoring suffering and death. And in order to survive in a world of tornadic disruption, this kind of ethical tunnel-vision may be unsurprising.
Thank you for enabling these important discussions.
Thanks for the very thoughtful comment which I agree with completely.
Scientists need to be bound by the scientific method but also are needed to warn ab out risks that are not proven particularly when the risk is of great damage and the proof will not be available until the harm happens. This is a different role for scientists but an important one for society. The question about the link between tornadoes and climate change does what we know about turbulence in the atmosphere, increased sea surface temperatures, potentially increased La Ninas increase the risk of tornadoes even though we dont have proof.
A number of commentators have asked for a shorter version of this article; Here is a summary.
Question 1. Is human-induced climate change affecting aspects of the global climate system which increase the risks of tornadoes.
Answer. Yes, human-induced climate change is: (a) warming the Earth including the oceans, surface, and lower atmosphere, (b) increasing water content of the air, (c) increasing the instability of the atmosphere, (d) likely increasing the intensity and frequency of El Nino-La Nina ocean cycles, (e) in so doing affecting the atmospheric winds necessary to tornado formation, and (f) increasing storm intensity, droughts, and floods
Question 2. Do these changes mean that tornado intensity and frequency will increase in a warming world.
Answer, No to propagate tornadoes you need the right combination of warm moist air colliding with cooler air and also wind sheer caused by the right difference in wind speed between the colder air and warmer air masses. In a warming world is not clear that wind shear will increase, decrease, or remain the same. A warmer planet will also affect the relative temperature differences between warm and cols air masses. Furthermore tornado trend data does not establish a statistically valid collaboration between climate change and tornado propagation although the trend data base shows some increase in the number of tornadoes recently but a decrease in intensity.
Question 3. Is there any other basis for seeing connections between a warming world and tornadoes.
Answer. Yes, no tornado would likely be propagated in the same place, at the same time, and with the same intensity as it does now in the absence of climate change because climate change has already altered global temperatures including seas, water content, wind patterns, and El Nino/La Nina cycles. To claim that climate change has already affected tornadoes is not to claim that intensity and frequency have increased, only that tornadoes would be propagated differently in a world not already affected by climate change.
Question 4. Why is there a ethical need to identify the potential links despite the scientific uncertainties.
Answer. Climate change must be understood as an ethical problem because: (1) it is some people putting others at risk of great harm through their release of greenhouse gases, (2) the harms to the victims could be catastrophic, (3) many of those most vulnerable cant petition their government to stop climate change, they must hope that those who are causing climate change will respond to their duties, responsibilities, and obligations not to harm others. If climate change increases the risk of harm, evidence of greater risk should be communicated to all even in the absence of proof. This is particularly true in cases when waiting increases the risk, the longer one waits to respond to the problem makes the problem worse, and when those most vulnerable have not consented to be put at risk. All of this makes communication of the unproven but scientifically valid increased risk for increases in the destructive power of climate change a moral mandate. It is also important to understand that other harms to life, health, and ecological systems from climate change are even more certain than increased tornado damage. For these reasons, communicating the reasons for the increased risk is morally required although such communication must acknowledge the uncertainties about increased frequency and intensity of tornadoes that will happen in a warming world.
Dr. Brown, there is a host of evidence that neither tornadoes nor extreme weather events have increased despite the ~ 300 year long gradual warming of the earth. This is scientific evidence.
Now, you can make the claim that scientists should ignore the scientific evidence and sign on to your plan.
However, you can’t do that and still call yourself a scientist. That’s not what scientists do. Scientists follow the evidence.
You also say:
Climate scientists following this kind of advice is the reason why hardly anyone believes climate scientists any more. For many years they warned about risks that were “not proven particularly”, that islands would disappear and Bangladesh would go underwater and the like.
Unfortunately the reason the risks were “not proven particularly” appears to be that they weren’t real … so now when mainstream climate scientists issue warnings, people mostly just laugh and point.
You see, despite not being scientists themselves, most people can recognize another production of the famous musical, “The Boy Who Cried Wolf”. I understand you are auditioning for the lead role …
Stick to the science, and leave the doomsday warnings to others. It doesn’t fit your style at all. You’re not even a good alarmist, while in the scientific world there’s a chance you still might make it.
The fact that the planet is warming due to human influences is a strong conclusion of the US Academy of Sciences on May 13 and at least four other times. If the planet warms as concluded by the US Academ it increases t he risk of torando damage from increased instability, more water content in the air, modified regional ocean circulation patterns, modifications to atmospheric winds. I never claimed that this is proof of increased intensity or frequency of toranadoes, in fact I explained why this might not happen. But the changes happening to the climate system from human activities, If you believe the view of the US Academy of Sciences, does increase risk from more violent storms including some tornadoes. That is there is scientific reason for concern but only time will tell what happens or much better models. I have also said in the article when communicating the increased risk it is important to not claim the risks have been proven.
Donald, in your summary in question 2 you start by saying “No.”.. but the rest of your answer is “maybe” or even we do not know. But you are not really saying no. Are you?
My understanding is that we face general climate destabilization where much of our general mess is predictable, but little may be described as directly causative. (but that only is a deficiency in our science) There may be unstable weather and oceanographic events yet to come that we have never seen before.
For instance, isostatic rebound is a great explanation for geologic instability. We are just unable to predict how it will express. We may note that we have lost 100 cubic miles of ice in the polar regions – which is heavy enough to cause geologic destabilization with more quakes and volcanoes, but we can’t say it is a cause, only a maybe. But it is important that we cannot say that it is NOT the cause — and a more important statement for ethical arguments.
I think there is discussion about causation and correlation. And just because we cannot yet see the mechanical cause, does not mean we can dismiss something as a false correlation.
Thanks again for hosting this discussion.
I am trying to say that we dont know that tornado intensity and frequency will increase in a warming world but there is reason to believe that this could happen and some of the reasons are based upon very sound science such as as the oceans warm water vapor will increase and atmospheric winds will be affected by more energy in the atmosphere. Both of these lead to more unstable weather which could increase the frequency and intensity of some tornado events. We do not, however, know that intensity and frequency of tornadoes will increase for reasons I set out in the article. Yet there is a substantial risk that in a warming world we will affect tornado propagation. Moreover, we will surely affect strong storm propagation even if we dont increase tornado propagation and any existing tornado is being propagated in a system that has already been affected by climate change.
“…we will surely affect strong storm propagation …”
From IPCC 2007: “Magnitude of anthropogenic contributions not assessed. Attribution for these phenomena based on expert judgment rather than formal attribution studies.”
And the expert judgement was quite far from “surely”.
There is also an opinion that in a warming world extreme weather events will more likely be less frequent. Simply because temperatures and pressures will become more homogeneous, because colder regions warm faster than warmer regions.
I really wish you had put a voice to the connection between science and ethics. Being a good scientist requires a high standard of ethics. This equivocating blend of supposition, vague qualifiers, and stuttering logic doesn’t qualify as either scientific or ethical.
“And so it is possible that average frequency and intensity of tornadoes [will] decrease in [a] warming world……so, as we have seen, there are scientifically sound reasons to conclude that as the world heats in response to human activities tornadoes will increase in intensity and/or frequency.”
This quote nicely sums it up. Tornadoes may increase and may get stronger, or they may decrease in intensity and frequency. As far as I can see there is no prediction of any note to ethically require any warning whatsoever. Similar to ‘the sun may shine tomorrow, or it might be cloudy”, or ” an unknown asteroid may hit the earth tomorrow, or it may not”. That kind of prediction is useless because it does not convey any information. On the other hand, I can predict with absolute certainty that an asteroid or large meteor will hit the earth in the future and will cause widespread, catastrophic damage. The only uncertainty is when, and the ethical question is what do we start now to do about it?
“That is although killer tornadoes may have formed in May of 2011 somewhere in the United States without climate change, the tornadoes experienced in Joplin and Tuscaloosa would not likely have formed at the same exact time and place in the absence of climate change because climate change has already transformed the initial conditions which trigger tornadoes. When and where a tornado is generated is dependent upon initial conditions and climate change has changed initial conditions around the world. “.
A basic tenet of meteorology is that the weather in not predictable in detail. It is chaotic. Since it is not possible to predict where and when tornadoes will hit in the future is is nonsensical to say that somehow climate affected the Joplin tornado to make it hit Joplin. The initial conditions to form a tornado must be present but the initial conditions do not determine exactly where any tornado will hit, only the general area. The type of climate change you are speculating about doesn’t involve any change in the mechanisms of tornado formation so regardless of the change, tornadoes will still form randomly, with no chance of predicting a specific location. The only scientific observation that can be made is that a tornado is much more likely to form in the central/southeast USA than anyplace else on earth. Joplin is in the southcentral USA and therefore is a likely target for a future tornado, unfortunately as soon as the next major storm system comes through. Nothing can stop another tornado from forming and hitting Joplin just as hard as the last one.
“1) it is some people putting others at risk of great harm through their release of greenhouse gases,”
Not some, but every person on the planet is producing CO2 and benefiting from it. The use of fossil fuels and the consequent improvement in the world standard of living is one of the primary reasons the world’s population has tripled. It is also the primary reason to believe that world population growth rate will continue to decline and level off at some easily sustainable level in the future. Unless someone panics people into making very bad ethical decisions that curtail economic growth, technological innovation, and personal liberty.
“But the changes happening to the climate system from human activities, If you believe the view of the US Academy of Sciences, does increase risk from more violent storms including some tornadoes. ”
You put together a fatuous explanation as to why the same information could cause both and increase risk from more violent storms or cause fewer violent storms. I do not believe the US Academy of Sciences because their position papers do not represent an unbiased, scientific point of view. It reminds me very much of the Catholic Church’s vendetta against Galileo. Many scientists placate the global warming establishment but still say “and yet it moves”, as Galileo did.
The essential difference between prediction in the abstract and climate change is that we are on notice that if we continue doing what we are doing in emitting greenhouse gases we are putting others at risk, others who have not consented to be put on risk. We now know that emitting greenhouse gases are changing the concentrations of the atmosphere and that these changes will likely lead to more water in the atmosphere which will likely lead to more droughts and floods and heavier rain events. This is just basic physics once it is conceded that the atmosphere warms. And so to not act has potential consequences to others. If course if we could eliminate the uncertainty immediately, ethical issues that arise in the face of uncertainty would not arise. But we cant eliminate the uncertainty immediately Decision-making in the face of uncertainty raises ethical questions about who should have the burden of proof and what quantity of proof should satisfy the burden of proof once it is clear that behavior is creating risks to others.
Donald Brown makes a very important point in this article. If we know that certain human behaviours might potentially cause harm to others, then that is an ethical issue that needs to be urgently addressed.
Think of it this way:
let A represent human activities resulting in excessive carbon pollution; let B represent global climate change; let C represent increasing likelyhood of dangerous local weather events; let D represents harm being done by those events to people. We can then propose a causal chain of A=>B=>C=>D.
Dr Brown is pointing out that we know the causal link A=>B is well established and that we know that the link C=>D is highly likely. He also points out that we have no convincing evidence as yet about the causal link between B=>C but, on the other hand, that there are many logical reasons and some scientific evidence that this causal link is possible. This being the case, we are ethically bound to consider the implications of this entire causal chain. We should not wait until the causal link B=>C is scientifically proven before considering the ethical implications of A on D. Human decision making and policy development has to be based on ethical as well as scientific considerations.
We need to make ethical judgements about the potential harm that could be done through human-induced climate change and these judgements should influence our decision-making and poilcy setting. Our response to the challenge of climate change involves ethical issues as much as a scientific evidence and Donald Brown does us a much needed service in bringing this point to our attention. He is asking us to consider the link between the global and the local, to consider the ethics involved in the impact of our activities on the climate and on the weather events that cause so much human misery.
Just a question about your excellent and thorough post on ethics of mentioning climate change as one probable cause of our extreme weather: have you checked out statements like this one with Kevin Trenberth or James Hansen or other climatologist? I wonder what their take on it is, whether they also think the ALL global weather is responding at least somewhat to climate change?
you wrote: “And so a strong claim can be made that climate change is now at least partially responsible for all global weather although the part played by climate change could be small for any individual climate event relative to other causes such as normal ocean circulation patterns. Yet, no tornado or hurricane experienced recently would likely be the same without some contribution from climate change. That is no tornado would appear at the same place, the same time, with the same wind speed without changes to the climate system that have been caused by human impacts on climate And so every tornado is very likely affected somewhat by climate change. That is although strong tornadoes have occurred before recent human-induced climate change, no recent tornado is likely to have happened in the same way at the same place in the absence of global warming. ”
James Hansen has said, according to the NASA website,
… “Weather in a given region occurs in such a complex and unstable environment, driven by such a multitude of factors, that no single weather event can be pinned solely on climate change. In that sense, it’s correct to say that the Moscow heat wave was not caused by climate change.
However, if one frames the question slightly differently: “Would an event like the Moscow heat wave have occurred if carbon dioxide levels had remained at pre-industrial levels,” the answer, Hansen asserts, is clear: “Almost certainly not.”
The frequency of extreme warm anomalies increases disproportionately as global temperature rises. “Were global temperature not increasing, the chance of an extreme heat wave such as the one Moscow experienced, though not impossible, would be small,” Hansen says.
For GISS’ full analysis, please visit:
Thank you again.
Interesting question, thank you, we will look into this.
This ethical dilemma seems a little trivial compared to some others in the climate change debate.
I’ve heard some reporters say that it would be irresponsible to report dissent about climate change because only a minority of scientists disagree that global warming is human caused. There is a systematic effort (by the media and scientists who make money from promoting AGW) to marginalize those scientists who challenge the orthodoxy. While this neither proves or disproves anything scientifically, it discourages other scientists from speaking out, creating a spiral of silence and making the “consensus” appear greater than it actually is.
And while it’s pretty much impossible to regulate the earth’s temperature, is it ethical to spend trillions of dollars trying to do so? If carbon taxes cost jobs, as they likely will, and don’t stop global warming, as they likely won’t, then are those regulations ethical?
And who decides the ideal temperature? Wouldn’t some parts of the world benefit from a longer growing season. More carbon dioxide would produce more plantlife. As the population of the world increases is it ethical to reduce carbon dioxide and thus reduce crop production?
Those are legitimate ethical dilemmas that aren’t being adequately addressed.
Here are the people who believe in global warming.
1. Scientists who get paid by bolstering the anthropogenic global warming theory. Also scientists whose funding might be jeopardized by appearing out of the mainstream. Interesting how many of the scientists who thing AGW is crap are retired and therefore don’t have to worry about funding anymore.
2. The media, who always enjoy a good story about an impending apocalypse.
3. Environmentalists, who believe with religious zealotry that man will destroy the planet. First it was the population bomb, then global cooling, then the ozone hole, now its global warming. I guess we’ll have to wait 10 to 20 years to see what crisis they think of next. Of course a good crisis leads to good funding.
4. Politicians. Especially the kind pushing for a worldwide government. Regulating carbon gives them a vehicle to accomplish their objectives. But also, local politicians looking for something to distract from more pressing concerns, like the economy, stupid.
5. Corporations and dudes like Al Gore poised to make billions if a carbon trading scheme is implemented.
6. All the dupes that think those listed above have their best interest at heart. I apologize for not drinking the Kool-Aid.
We would agree that the ethical issue raised by some very inconclusive evidence about links between tornadoes and climate change are trivial compared to the ethical issues that arise because of potential connections between human activities and other severe impacts on human health and the environment.
Nonetheless, the tornado example raises the interesting ethical question of what should be done when there is valid question for concern about an harsh impact from human activities but the science is far from certain, yet, if you wait until the science is conclusive it is too late to do anything about it.
We do not agree that climate change is being pushed by biased ideologues, it is being articulated by the most prestigious scientific organizations in the world including the United States Academy of Sciences. .