Global Warming - Conclusion

Those who are on the climate change bandwagon and the deniers accuse each other of being bought off.  The deniers or skeptics must be paid shills or hacks for the oil industry. Maybe some are, but the brightest are not.  Also, some who are loudest about a climate change catastrophe also have a dog in the fight. And many of the brightest scientists are not vocal.  Both sides are guilty of selective use and interpretation of data and both vehemently deny it.   Missing is a thoughtful and knowledgeable discussion about how to manage all our resources and minimize the negative impacts of all kinds on civilization. Included in that discussion should be: population growth, food shortages, and the lack of fresh water for crops and to drink. Haven’t heard it yet. But these crises will precede significant temperate increases by a hundred years.  You will begin to hear about them.  I can hear them coming.


I think the evidence of increasing temperature in recent centuries is real but that many of the forecasts are exaggerated and over generalized.  The predictions of an unstable atmosphere with temperatures exceeding those used in cremation are crazy, but ice will melt.  Nature seeks an equilibrium temperature, and that equilibrium will be warmer than it is now.   Bottom line:


Will warming continue?  - yes

Are people responsible? Is it at least in part anthropogenic activity? – yes

Can we fix it? – yes

Will we fix it? -- no

Is it a catastrophe as portrayed? – no

Will nature fix it to its satisfaction? – yes 

Can we survive the warming? – yes

Are there real catastrophes that need to be addressed now? – yes

Are they being addressed? – no

What is the problem? – POLITICS, $$, and sadly, our own human nature.


Keep in mind the carbon we are putting in the atmosphere, actually was there, we are just returning it after it was in storage for a few hundred million years. And when we run out of it, it will be a catastrophe.


There is also an indication that we are in the midst of an increase in extreme events.  Oddly, it was only in the 1970s that Florida had such a freeze that it killed all the orange trees except in the very south of Florida. The southeast has actually has been cooling.  So maybe the use of “global” should be used more carefully.


It is likely that in 200 years mangos can grow in Tallahassee and our climate might more resemble that of Orlando.  I have already planted my two mango trees, just in case. It is likely that we will loose some coastline and we will gain some elsewhere. The drying aquifers in California and Texas are releasing pressure on the earth’s crust and the land is already rising. Regionally that will more than compensate for any sea level rising.  The earth is and has always been a dynamic system with natural wild swings in just about everything.  We do contribute to changes in the atmosphere, and are we adding to that for the first time in the history of the earth. Our increased numbers allow us to do that.





Possible break here for part 2.






What will happen to the average global temperature?  It will get warmer.  We will also run short of potable water; we will run out of energy; we will have hundreds of times more mouths to feed, drug resistant bacteria will kill us, and we will have insufficient water to drink or to use on crops, even though we have run out of room to plant them.  


The problems we face are far bigger than just burning oil. What we do or don’t do in all areas: climate, population growth, alternative energy sources, conservation of water, etc., will dictate the outcome of climate change and more importantly the quality of life if not life itself.   In the mean time, 1) none of us (currently living) will be around during the “worst of times”, and 2) no one will be worried about climate change in 100 years – no more than the ozone hole, nuclear winter , el Nino, etc. It will be the beginning of “survival time”. Don’t say we can use reverse osmosis, etc, because everything takes energy and we need a lot of fresh water.  And forget about the oysters in Apalachicola Bay.


By then, the real problems, the ones that are hard to push off to the future, the ones that will truly divide us, the ones that REALLY matter will be in our face.  The reality is: people will dream of protesting a rather small rise in sea-water level.   They will because the earth is crowded.  The population doubles every 40 years. In 100 years there will be 100 times as may people living on the earth.  All will suffer the lack of food and water.  Many will die and wars will be over resources. 


There will be change -- there always is.  The earth and climate has always been in a state of change.  We will adapt.  Ultimately all the fossil fuels will be used up in a few hundred years.  And then we will have to contend with that very real problem.  In the mean time, we will fight over food and water and more will die of starvation than from heat, even though the atmospheric temperature will reach a new normal. And the increase in carbon dioxide will come from human breath.


We need to conserve!  Do we want some foreign country to have all the remaining oil?  NO, we want the last drops of oil!  We must conserve that natural resource.  We need to diversify our sources of energy and how to store energy.  We need as many ways as possible, as soon as possible, while we address the really tough issues we are avoiding.


Yet there is no serious consideration to these potentially catastrophic problems that are just over the horizon.  Remember that Mark Twain famously observed, “Whisky’s  fer drinkin’ and Water’s fer fightin’ over”.

Got that right! Amazing.



Star of Bethlehem

This season, the Nativity story of the birth of Christ will be retold in churches everywhere in words and in pageants. It is a story of a stressful journey to comply with a census decree and one of humble beginnings and an accommodating and sympathetic innkeeper.  It is the most significant birth in all of Christendom.  It was a humble birth, attended to by shepherds and three Magi (or Wise men) who came following an unusual guiding star – the star of Bethlehem.


The guiding star story is found only in the book of Mathew. It is also true that the study of astronomy was very earnest and learned even then.  Any unusual astronomical event was certain to be noted and very likely ascribed to some unusual event. Although the Roman Historian Josephus was born shortly after Christ was crucified, he seems to have been well aware of the life and impact of Christ, and his accounts represent one of the earliest account of history in general, and the life of Christ in particular.


From all scholarly research, Christ was probably born between 6 and 4 BC. Christmas was not declared to be Dec. 25 until 529 AD by Emperor Justinian and further ratified by the Council of Tours in 567 AD, which also made Advent, the period of fasting preparation for Epiphany (the 12 days of Christmas). This would co-opt the pagan celebration (Saturnalia) of the Winter Solstice. Some of our Christmas traditions are reminiscent of those and other pagan traditions and celebrations. The actual birth month is more likely to be in the spring or fall due to the seasonal reference in the nativity narrative.  Christ was crucified,  probably on April 7, 30 AD or possibly April 3, 33 AD, although other days  and years can be argued due to inconsistent textural references.  Biblical and references made by Josephus to the reign of Herod and Tiberius argue for a birth date of about 4 BC making Christ about 33 years old when he was Crucified.


What can science add to this?  We again turn to what was observed and referenced, particularly the star of Bethlehem.  Ancient learned men (Wise Men) were well acquainted with the night sky and would note any irregularities.   The Chinese also kept detailed records to any changes observed in the heavens and are another data source. There are several explanations given and dates ascribed to them. They are, in particular: A supernova (death of a giant start), conjunction of planets or a star, and a comet.  The case against these is their implausibility at any time near the birth of Jesus. Specifically:



·      Supernova – couldn’t be because we would still be able to see the remnants and there are none and the Chinese would have recorded it and no one noticed it.

·      Conjunction of planets – various paring have been proposed but none fit well with the biblical narrative.

·      Conjunction of planets with star (Regulus) – Not close to the correct year and the positioning  would have been to the west, not the east

·      Comet (Halley’s) passes in 12 BC, several years before Jesus’ birth. The Chinese observed a comet in 5 BC which still doesn’t fit the chronology of Jesus’s life.

But even given all that, how could a star guide anyone to a particular address?  Further, the Chinese who also meticulously recorded all strange happening in the heavens report nothing unusual in the night sky around the possible dates.


Mica prophesied in about 720 BC that the Messiah would be born in Bethlehem. Isaiah predicted that the Messiah would be born to a virgin.  There are something like 30 or more Messianic prophecies which are fulfilled by Christ as reported in the scriptures including a reference to a star. There seemed to be a need in the early Christian church to report all the ancient prophecies of a coming Messiah were fulfilled, including the star prophecy.


So, with that, hold on and cherish your faith, whatever it is.  And humbly remember what St. Augustine of Hippo said:  “There are many wolves within and many sheep without”.   And as St. Augustine further observed: “Miracles are not contrary to nature, but only contrary to what we know about nature.”


Whatever your faith tradition is or isn’t, I wish you a wonderful holiday season, happiness and prosperous New Year.  Merry Christmas.


The Case of the Climate Change Skeptics

The climate change skeptics fall into two groups: those who think the earth is not warming significantly at all, and those who feel the consequences are not proportional to the more modest warming that may take place.  I have combined these into those who are skeptical that the catastrophic warming that is predicted by the climate warming protagonists. Those for whom “warming” is a understatement. For it those who advocate for major changes in policy.


Humans DO make an impact. Driving you car to the grocery store makes an impact.  A cow making an impolite contribution to the atmosphere does too. The position of the skeptics is: How much and to what effect?  The question may not be that the temperature goes up, but even if it does, “so what”?  Is it the end of life as we know it, or is it an inconvenience?  Few would suggest that it is the end of life for humans or cockroaches, but it may reduce the population of, for example, polar bears.


Nature can seemingly be rather cruel.  Many species have come and gone. No doubt that will continue.  Humans now have the ability, and in fact have, superseded natural events changes.  And now, with record populations, human are poised to make significant impacts on many systems and alter what would be the natural evolution. 


To skeptics, the term, “catastrophic” isn’t clear enough.  Catastrophic to whom or what?  That is the significant question to them.  Although some may be skeptical that it is happening at all, even more are skeptical of the catastrophe that climate change is portrayed to be.  Although the majority of scientists claim the earth/atmosphere is becoming untenably hot in time unless we greatly reduce or dependence on fossil fuels, not all scientists agree.  Principally their arguments focus on the value of a short undeniably noisy climate record to make conclusion or predictions and the well known inaccuracy of forecast models.


There are bright scientists on both sides of the argument.   And many of the rest of the brightest scientists remain silent. Neither side can lay claim to the best and the brightest.


I would add a disturbing fact.  Many academics and labs are getting a lot of money to study this phenomenon and a looming disaster. Oil companies may also be supporting the “deniers”.  Many of the most vocal climate scientists on both sides have, or would like to have, an economic or other interest in their climate position.   Sounds a little like politics.



















Case Supporting Dramatic Climate Change

The case for a dramatic increase in temperature and all the attendant effects relies on extrapolating temperature data recorded over a long time at different places around the globe, indirect evidence from ice cores, tree rings, etc., and climate models which include the impact of an increase in the amount of infrared absorbing gasses in the atmosphere. 


Although the earth has undergone many temperature cycles, the contention is that the present changes are not part of the natural evolution of the earth and atmosphere, but rather due to the direct actions of humans, principally the use of hydrocarbon fuels and the attendant increase of carbon dioxide in the atmosphere.  The data shows that for the places records are kept that over the last 100 years there has been about two degrees Fahrenheit in temperature increase.  But it has not been steady.  Until 1920 there was little increase and form 1942 until 1978 there was again almost no increase.  However, since 1980 there has been a steady increase, even though there is a year-to-year variation of about plus or minus about half a degree F. Arguably there have been episodes of basically a decade of cooling surrounded by years of greater warming.  The net effect over the last 200 years is net warming.


Presumably the root cause is anthropogenic and because of an ever-increasing demand for the energy content of fossil fuels. And although not exclusively, much of the increases is focused on the CO2 increase in the atmosphere from the burning of fossil fuels.


Many climate computer models capture the trend of increasing temperature, but not the year-to-year or decade-to-decade variations. Although the physics employed in the models are fairly well known, the details and the interactions are much less known. The future is, from the models, increasingly worse, and some models show it goes from just and increase in warming to a “catastrophic” warming – a nonlinear increase in temperature.  Part of the variation in prediction is due to not knowing if the use of fossil fuels will decrease or increase.  And part is just inadequate knowledge of the interactions of a problem that has many more variables than just Carbon dioxide.  Some of unknown variables are social.


For example, the primary source of methane is feed lots and bovine flatulence.  As 3rd world countries become more prosperous, their desire for meat increases.  Alas.  But also there may be a reduction in meat as it become increasingly expensive.  And a very important greenhouse gas is water vapor.  As the atmosphere and oceans warms the amount of water vapor in the atmosphere increases as the saturation vapor pressure increases. The melting ice will locally change the salinity of the oceans and ocean currents may be altered. There is likely to be a cascading of effects both big and small in many details.  Almost everything will feel some effect, from agriculture, aquaculture, habitat, etc. Most importantly the weather patterns will be certainly be affected, but in ways that are hard to predict – More/less storms, more/less rainfall, different storm paths, sea level rise and relocation of beaches inland from their present location, etc.  Weather patterns will be altered and some areas will experience warmer temperatures and more or less rain while others cooler and/or  less rain.


As the polar ice melts, the sea level will rise and habitat for animals from polar bears to seals will change.  As the oceans acidify, the habitat in the oceans will change and coral will struggle to survive.  Some low-lying islands will get smaller and perhaps go underwater.  The forecast effects will certainly make a different would.   But it will NOT turn into “Water World”.










Climate Change Advocates

We all want the climate to not change.  But it will, and it always has. It is important to clearly understand what is meant by climate. Climate is the average weather over an extended period of time.  Climate change can be for almost any length of time.  Often in Meteorology it is 30 years, but for this discussion, climate is defined to be hundreds to a thousand years. 


All the yearly and decadal variations go on top of the climate trend. And these higher frequency variations can be as large or larger than the climate trend, necessitating many years of data to get an accurate estimate of the  long term change in the weather. Climate can also be regional or global.


There are two key elements used in assessing climate change.  The first is to look at the (global) change in weather over many, many years, and  perhaps extrapolating any trend into the future.  The second is a climate model that would calculate the future climate much as weather forecasters uses a model to forecast the weather for the upcoming week.  So, data and models are the back-bone of climate research and prediction.  Data may be in the form of long term records of data from cities scattered around the globe. It can be tree rings, or ice cores where the deuterium to hydrogen ratio can be measured to obtain temperature.


There have always been large changes in global climate. The extremes in temperature in the earth’s history have been absolutely huge, ranging form a mile thick ice covering everywhere, to no ice at all. This is all before humans existed.  Many of warming periods were associated with an increase in carbon dioxide.  Decreasing amounts of carbon dioxide accompanied periods of cooling. The carbon dioxide concentration is highly correlated with the temperature. But a high correlation does not imply causality or the lack thereof.   Other extremes in temperature are related to earth’s periodic orbital changes.


It is useful to remember a demonstration used  in a blog some time ago, where the level of water in a tank was a proxy for temperature.  A hose at the top poured in water and represented the energy coming from sunlight in the visible part of the spectrum.  A spigot at the bottom represents the energy escaping to space in the invisible infra red (IR) portion of the spectrum.  When the amount leaving equals the amount coming in the water level (temperature) stays the same.  At night there is no sunlight coming in so the spigot drains out water and the water level (temperature) drops.  That is why it is colder at night.  During the day, the effect is reversed.  The same is true for the atmosphere.  If the spigot gets clogged, it corresponds to an increase in absorbing trace gasses, and less of the energy the earth radiates to space can get out, just as the same energy is trapped inside a car on sunny summer day. 


When we talk about greenhouse gasses, the preponderance of the conversation centers on carbon dioxide, and the carbon dioxide that is a by-product of combustion of fossil fuels: natural gas, coal or oil.  Yet there are many other radiative active trace gasses.  Some of the most active and their concentrations in the atmosphere are: carbon dioxide (CO2) 0.04%, water (H2O) up to 4%,  Methane (CH4) 0.0002%, Ozone (O3) 0.001%.  We want more Ozone to protect us from UV radiation, yet the more Ozone there is the greater the greenhouse warming will be.  We want more water to produce fresh water, but the more water in the atmosphere to create rain, the hotter the temperature. 


There was a time in the last 2000 years of recorded history that we had very cold periods and very warm period.  There was no anthropogenic cause because there simply enough people to make a difference and also it wasn’t until the industrial age that the wide spread use fossil fuels began to increase the concentrations of carbon dioxide.  Now, for the first time in earth’s history, we can change the natural course of events.  And that is what the Global Warming debate is all about.


Next time we will examine what the data shows for global warming.












Climate Change Discussion

What does climate change portend for hurricanes?  Perhaps a lot, but maybe not as much as it would appear.  Let’s look at the facts.  This is the first part of a discussion of what we know and don’t know about the facts surrounding climate change and what the effects might be for life on earth.  And more broadly, we will go beyond climate change to other changes that will greatly affect life on earth.  In the final analysis, you will exercise your own critical thinking skills to make up your mind and not just adopt what others say.  I hope you will be better informed to do so. 


One observation I have made is that people like things the way they are – at least climate-wise. So minimizing change seems to be one goal.  Hot where it is hot and cold where it is cold.  We want to preserve artic ice, have no sea level rise, and that Florida be the most hospitable state in the winter months and that oranges don’t freeze.   That is, climate change should be zero from several decades ago.


We will start with the arguments supporting that there is climate change and that the results of which will be detrimental if not catastrophic to life as we know it. Then I will present the case of the so-called “deniers” (by the pro-climate change enthusiasts).  These two represent the two extremes of a complex problem.  I think every reasonable scientist on both sides of the a very polarizing argument will agree it is a complex problem with parts well known and parts not well known.  It is also clear that most, perhaps 85%, of the climate scientist agree that the mean global temperature is increasing. 


It is further clear that very often both sides have a “dog in the fight”.  That is to say, they either are or hope to profit financially or increase their standing by the position they espouse. That does not make their arguments incorrect or disqualify them, but it adds at least an apparent conflict of interest.  In addition, the scientific community, societies and board have uniformly come down on the side of a catastrophic looming climate change.  To not embrace that view tends puts one as an ill informed, obstructionist. 


The argument has taken on a distinctly political tone, with Republicans more generally identified with the “deniers” and Democrats aligned with those warning of catastrophic climate change.  Unfortunately, it has become as polarizing as all the other issues of national discourse.  It really is first, a question of science, and second, a question of what if any should the social response be.


Strangely, those whose level of technology doesn’t extend beyond their smart phone, have advocated one position or the other.  Perhaps less strangely, politicians have taken stands as if they had an inkling of the facts,  and their positions seem to align well with those of their electorate. Few could support their arguments well. 


The beauty of this issue is that it will not be conclusively resolved for a century and no one will be held accountable.  That, you will see, is both a blessing and a curse.


What I will attempt to do as concisely as I am able, is present some of the relevant facts, on all sides.  I will also present some facts that are conveniently ignored by both sides.  And in the end you can decide where you come down on this important but complex issue.  For most of us, we will realize it truly is not black or white.


How Unique is our Weather

e have examination our solar system for the key ingredients required in the formation of that one-eyed monster, a hurricane,  and the clouds that produce tornadoes and found these important ingredient are only found on earth.  This is in no small part due to one of the incredibly important atmospheric constituents that only exists in any kind of abundance on earth – water.  Water that can coexist simultaneously in all three phases: gas, liquid, and ice -- and that too is unique.  One of its remarkable properties of water is its huge latent heat of vaporization and condensation. This allows for the redistribution of an enormous amount of energy.  According to a NOAA analysis,  healthy hurricane can redistribute an amount of energy equivalent to 200 times the world-wide electrical generating capacity.  Which partially explains the difficulty in any attempt to modify hurricanes and even thunderstorms.    Our atmosphere is only 1to 4  percent water vapor, which is still far more than any other planet  in our solar system.


Because of the difference in heating between a planet’s equator and poles, meridional (north-south) circulations develop.   This differential heating, the planet’s rotation rate (hours is a day), the planet’s size and depth and composition of the atmosphere determine how many cell exist.  For example, the earth has 3 cells and Venus only one.  The giant gas plants like Jupiter have symmetric instabilities that result in many cells that encircle the planet.


For the earth, all this, coupled with the Coriolis effect cause zonal (east-west) winds to come from the east near the poles and equator.  In mid-latitudes (the United States and Europe) winds tend to blow from the west.   There are many consequences from all this, but the point here is it only exists on earth. And while there is rough weather (winds can exceed 2,000 miles per hour on some planets), there is nothing that resembles our storms and weather.


It is also worth noting again, we owe the atmosphere we have to the distance we are from the sun (how much heat we receive) and the planet’s size (the gravitational acceleration).

Most of the water in our atmosphere came from within our planet, not from being bombarded by comets as is popularly believed by some.  Much of the oxygen was and is generated by plants.


But what about other suns and planets.  There are 1011  (that is 1 with 11 zeros after it) stars in our Galaxy and it is estimated there are1011 galaxies in the universe or 1022 stars in the universe.  If only a small percentage of stars have a planet about earth’s size and about the same distance, these would be the “Goldilocks planets”. There certainly are planets of other stars that have are the same size and distance from their sun, and they probably also have water.  So, they probably do have tornadoes and hurricanes!   In fact, in our galaxy alone, it probably is common.


But even more, all the chemical ingredients of our atmosphere are very likely to  exist for producing an atmosphere that we would be familiar with on some planets.  And,  maybe some molecules would combine by chance as in a chemistry lab, to form a organism that could sustain itself and replicate – life.  Personally, when you consider the distances, I think we will never know, but it is something to contemplate. In any event, whatever exists would not be human, as we know ourselves.  Our own individual probability of existance is less than all the stars in the universe.  Each of us is literally more rare (unique) than all the stars in the universe and that is a statistical fact.  You are truly special.



Why do we have Hurricanes and Tornadoes? Part 1


Are hurricanes and tornadoes, just to name a few extreme events, unique to our planet? And if so – why? Would similar kinds of weather events occur on other planets?   Why do we have these events on our planet?  What is it about the Earth that makes these possible and do they exist elsewhere?  Or is each plant’s weather unique?  I started our making a table that is a listing of just how varied the atmospheres of planets are and just how special Earth’s weather is; but a table misses the point.  So, a description seems better.


The Ancient Greeks preached “Meden Agan”, and the golden mean.  And in all my research I inevitable seek mathematical optimizations of competing multivariate solutions. But every time I contemplate this topic, I am drawn to the children’s story about Goldilocks and the Three Bears.  In this children’s lesson, Goldilocks seeks the best between extreme choices.  So it is with our planet’s composition. 


The planets in order of their distance from the Sun are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and sometimes Pluto. Lets examine our solar system and the weather of each planet and the kind of storms they might have.


·      Temperature – You might expect that the further away from the sun the colder the plant would be.  And indeed that is the case.  The average temperature in degrees Fahrenheit in parentheses for each planet is as follows:   Mercury (333 F), Venus (867 F), Earth (56 F), Mars (-84 F), Jupiter (-166 F), Saturn (-230 F), Uranus (-320 F), Neptune ( - 330 F) and Pluto (-375 F)

·      Surface Pressure – Surface pressure is the atomic mass of all the gass molecules above a point at the surfaces times the planet’s gravitational force.  Here we are comparing each plant’s surface pressure to that of the Earth’s.   Mercury (0), Venus (91), Earth (1), Mars (0.01 or equivalent to 40 miles above the earth’s surface ), Jupiter (unknown), Saturn (unknown), Uranus (unknown), Neptune (unknown) and Pluto (0)

·      Gravity – Again expressed as a fraction of that of the earths: Mercury (0.38), Venus (2.8), Earth (1), Mars (0.38), Jupiter (2.4), Saturn (0.9), Uranus (0.9), Neptune (1.1) and Pluto (0.06)

·      Diameter – Units are in miles:  Mercury (3,032), Venus (75,521), Earth (7926), Mars (4,221), Jupiter (88,845), Saturn (74,897), Uranus (31,763), Neptune (31,775) and Pluto (1,485)

·      Atmospheric gasses -  Listed with the percentage of each gas in parentheses:  ALL planets -- including the Earth -- have trace gasses, many of which are greenhouse gasses and very important.

o   Mercury (trace),

o   Venus  CO2 (96 %), N2 (3.5 %), H2SO4 (clouds)

o   Earth N2 (78 %), O2 (21 %)

o   Mars (0.38), CO2 (95 %), N2 (3%)

o   Jupiter NH3 , H2 O , CH4 and many trace gasses

o   Saturn H (75%) and He (25%)

o   Uranus H (75%) and He (25%)

o   Neptune H (80%) and He (19%)

o   Pluto (trace)


It is interesting that the four inner planets have a solid surface of similar composition, and the outer five are much larger and are all atmosphere with little or no solid core. The solid part of the inner planets is very similar to the earth.  The giant gas planets (Jupiter, Saturn, Uranus and Neptune) are mainly liquid and gas, lacking a solid surface and mainly hydrogen and helium.


If Jupiter were 75 times bigger it would become a star.  Still it looses about 2 cm of size each year due to outgoing radiation.  When Jupiter was first formed, it was twice its presence size.  The temperature of the planet and the force of gravity of a planet largely determine what gasses will comprise its atmosphere.  It takes a large gravitational field to hold light gasses such as helium and hydrogen.  Planets with weaker gravitational fields can hold only CO2 and other heavy gasses.  The value of gravity is determined by the size of the planet and its composition. The inner planets (and some moons) have solid  ground and their history resembles that of the earth with volcanoes and even water over a least a portion of their history. 


Winds in some of the planets exceed 2,200 miles per hour.  That would be equivalent to at Category 220 hurricane. Only the earth has much Oxygen and Nitrogen.  The wind pattern in each planet’s atmosphere is largely governed by the speed of rotation, depth of the atmosphere, and the temperature at their equator vs the poles.  I remember my first scientific publication while I was a first year graduate student.  I collaborated with some scientists and Peter Stone from Harvard and we wrote a paper on the wind structure of Jupiter and Saturn as the result of symmetric baroclinic instabilities.


Next we will look at what determines what kind of weather planets have and if any have weather we would be familiar with. And what gives us the kinds of storms we have.  From there we will go to what effects climate change will have.




Hurricanes and Tornadoes and Florida

Are Hurricanes and Typhoons Less of a Threat?It should be clear by now that there is a lot of year-to-year variability in the number, location, and strength of Hurricanes and Typhoons.  Typhoons are hurricanes that are west of dateline.  There are the hurricanes in the Atlantic Basin and Caribbean and also

off the west coast of mainly Mexico which typically move NNW.  Typhoons form in the more western Pacific.  The Pacific Hurricanes have their own names, different from that form East of Central America extending to the Eastern Atlantic.  Since these generally move out to the Pacific and die, they most often directly impact the Baja and not the United States directly.  And Typhoons use yet another pool of names.  Actually there are six separate basins, each with their own set of names.  So if you want something named after you, your odds go up.


The damage potential of a hurricane or typhoon is proportional to the square or cube of the wind field.  Minor hurricanes, although more numerous, do not do nearly as much damage as a major hurricane is capable of doing.  Keep in mind that a building does not have to be totally destroyed to be “totaled”.   If something like 50% of the building is destroyed, it is a total loss.


Two different measures (maybe more) are used to describe the damage potential or strength of a hurricane (or typhoon).   One is the Hurricane Severity Index (HSI) and another is the Accumulated Cyclone Energy (ACE).  And no doubt there could be more.


The HSI defines the strength and destructive potential of a storm.  This index, in the aggregate, includes all storms, not just hurricanes.   The principal feature of this storm is that the size of the storm may be as important as its peak wind speed. Points are given (1-25) for the size and another set form (1-25) for intensity.  So a storm is categorized as a score between 1 and 50.  This includes all storms from tropical storms through hurricanes and typhoons.


A better know and more widely quoted index is the ACE index. It is used by NOAA.  It is computed by taking the wind speed for all tropical storms and hurricanes and summing the square the maximum speed (in knots) and doing this every six hours.  That addresses the maximum wind speed and duration.  For convenience the result is divided by 10,000. The units are then 104 kn2 .  The contribution of storms in the Atlantic Basin to the Global total of is shown in the accompanying figure in light grey, where as the global total is shown in dark grey. You can see the Atlantic Basin is a little lower that it has been for much of the past several decades, but it is normal when compared to all years.  Yet the Global ACE value  is lower that normal.  The trends do not support some of the scenarios put forth by Global Warming enthusiasts.


Both of these indexes show great annual variability.  ACE values ranging from near zero to 250 the focus of HSI is on characterizing individual storms, rather than climatology. 


In recent years, pacific activity has picked up.  Even so, there has been an overall apparent decrease in the numbers of global storms particularly in the Atlantic basin. 


Hurricane wind speeds (2)




Some Civil Engineers think they can tell the wind speed by the damage, and to a certain degree that is possible, but it is not precise.  Officially, the most credible measurement comes from NWS towers.   There are  also many deployable towers that collect all kinds of in situ data, including wind speed. In addition, Doppler Radar can measure wind speed, but only the component toward or away from the radar.  With towers it is possible to get an accurate reading. But for the maximum wind, the towers must be in the right place, and that is not always easy to anticipate.   Maximum wind speed is not an easy measurement to make over land, but it is even more difficult over water.


Over water there are instrumented buoys, but again they have to be in just the right spot to measure the maximum one-minute average wind.  Aircraft can measure flight level winds but these are high above the ground.  NOAA operates two P-3 Orion turbo prop airplanes,  and the Air Force a  WC – 130J.  Both workhorses. The NOAA planes have X band Doppler radars on them and they produce in flight real time plots of the winds. In addition they deploy dropsondes that are instruments that measure and telemetry all kinds of data, including the wind speed.  So as it descends near 10 m off the surface it gives the wind speed. But that is the winds where the sonde is, not necessarily the storm maximum.


Another way is that by analysis, it is found that the near surface winds are about 80% of the flight level winds. This give an approximate value..  Of course, one problem with an aircraft is that is must move.  Thus it is measuring wind along it’s track, and the track my not be over where the winds are the greatest.


For several years, the maximum one minute average winds are largely determined by a nadir pointing microwave radiometer that uses 6 channels in the microwave portion of the spectrum (where the wavelengths are of the order of centimeters in wavelength.  (Your microwave oven uses wavelengths in the x-band or about 3 cm in wavelength (a little over an inch from peak-to-peak of the EM wave).   I these instruments measure the strength of the upward radiation from the  sea.  Everything emits radiation, just as the sun does.  The colder the object, the less it radiates and the longer is the wavelength where the intensity is the greatest. The strength of the radiation that is measured is called the brightness and it is related to a temperature, the brightness temperature. Not all object radiate equally well.  A so-called black body both absorbs and radiates the maximum possible. 


The stronger the wind, the most disturbed the sea and the greater the amount of sea foam.  Sea foam radiates really well and is nearly a perfect black body, so more is radiated. Thus the stronger the intensity, the more disturbed the sea and the stronger the wind.  Now the temperature of the water is a factor and the intensity of the rain is a factor.  It turns out that as for the temperatures involve, the error is small (a fraction of a degree and a few m/s).  The rain rate can be deduced from two different frequencies and that can be accounted for.  Of course there are other problems such as RFI (radio frequency interference, etc. ) but they can also be minimized. 


What remains is a reasonable estimate of boundary layer winds along the airplane’s flight path.  It still is not guaranteed to be the maximum winds anywhere, but it is an estimate and not just a point measurement as is the

dropwindsondes.  It tends to over estimate the winds in the eye, because, while the winds are near zero, the sea has not adjusted to that low wind speed so it over estimates the winds. And it probably underestimates the maximum wind, but it does a pretty good job.


Keep in mind, the maximum sustained winds (msw) is the average over one minute and gusts can and will be 30% higher and lower than that average. It is an average and not the maximum wind. Given all the uncertainties, it is appropriate to view the numbers as qualitative important with an uncertainty of least 5 to 10 mph.





Global Warming and Hurricanes



We really have not addressed Global Warming yet, but let us suppose for now that Global Warming is real.  What will it mean for hurricanes? We know that sea surface temperatures (SST) are an important ingredient in the formation and maintenance of hurricanes. Nominally SST must be at least 79 F degrees to form a hurricane.   We know that El Nino increases the wind speed as you go up in the atmosphere, and that is called vertical wind shear.

And that vertical wind shear is not conductive to hurricane formation, particularly weak hurricanes – the tops keep getting blown off.  Of course all the effects are interrelated with each other and many others.  We have already noticed that in El Nino years there is a proclivity for fewer, but stronger storms.  This is a clue.


Hurricane frequency and intensity vary a lot from one year to the next.  The very first article I wrote this year (which can be found at decried the inaccuracy of annual hurricane forecast as a prelude to this years forecast, one of the worst seasonal forecast.  (Although this years over-forecast averages out the under-forecast of 2005 in some perverse sense of the average accuracy).  Thus, how can anyone accurately forecast hurricane activity 100, 200, even 300 years hence when each year’s prognostication is of little value? It is difficult.


This highlights the tremendous year-to-year variability and even decadal highs and lows, even if there is a trend.  It means the climatological trend can be determined only over many decades. Remember how active the season was from 1995 through the record breaking 2005 season.  Many “professionals” claimed this was proof of Global Warming and a harbinger of imminent and even worse years.  Then came 2006 though this year so far.  Happily for many, very quiet Atlantic seasons, punctuated with exceptions such as Sandy. 


But what does the data and theory suggest?  We can look at the seminal and landmark paper published on hurricanes by Kerry Emmanuel of MIT who looked at the thermodynamics and suggested an upper limit to hurricane strength.  Others have suggested a 3 % - 5% increase in hurricane strength for every 2 F degrees of increase in global temperature.  All the observational inferences are based on incomplete data records, and are speculative (although frequently not presented that way). 


What the data does suggest that does make some thermodynamic and dynamic sense is that the Hadley circulation will increase, that the vertical wind shear will increase, and that the jet stream will increase and this will produce  on the average 1) about the same number of global hurricanes and typhoons, with a tilt toward 2) more stronger hurricanes and fewer weaker ones, and 3) an infrequently met  upper limit of hurricane wind speeds of about 200 mph.  That’s in several hundred years -- although there some weak evidence in this direction in the last few decades.  There will always be much larger annual variations than any trend increase. 

Global Warming

The accompanying figure is the logical extension to last week’s illustration of water flowing in, and then out of a tank.  Depending on the flow rates, the water level will reach an equilibrium because the higher the water is in the tank the more pressure at the bottom and the greater the flow rate out of the tank. 


Thus so it is for the radiant energy from the sun (in the visible part of the spectrum) at the top of the tank and the outbound radiant energy leaving at the bottom in the IR (infrared) part of the spectrum.  Just as the height of the water reflects the equilibrium water level, the temperature reflects the relative balance of radiant energy coming into and out of the atmosphere.


The illustration here shows why the daily and seasonal temperatures vary, and explains why the highest temperature during the day is in late afternoon when the sun is most directly overhead at noon, and also why the hurricane maximum and the highest temperature during the year is in mid September (close to the autumnal Equinox, the beginning of the Autumn season) instead of June 22 (the summer solstice when the sun is most directly overhead during the whole year).


The sun shines on each spot on the earth only about 12 hours a day (more or less depending on the latitude). The rest of the time, the earth’s rotation is presenting a different face to the sun and it is dark.  But the earth radiates energy out to space 24 hours a day, sunlight or not.  This is because everything radiates energy just because it has a temperature above absolute zero.  The amount of energy radiated and the wavelengths where it is radiated depend on the temperature.  This is analogous to what comes out the bottom spigot.


So as the earth radiates in the darkness, the earth cools.  This is true every night and also in the fall and winter months. Then when the sun shines more, the earth begins to warm and the temperature rises starting at sunrise, and also during the spring and summer.  At 12 noon/or and on June 22 the sun is highest in the sky and the heating is at a maximum, and more than the earth can radiate away -- so the temperature rises. It will continue to rise as long as the amount of energy coming in from the sun exceeds that being radiated away.  It isn’t until late in the day or in the Fall that the energy coming in is as low as the energy being radiated away.  At that point the earth stops heating and begins to cool.    It is that point during the day that it is the hottest, and it is at that point during the year where it is also the hottest.  As long as the heat coming in is greater than the energy going out, the temperature will continue to rise.


Hurricanes thrive on warm ocean temperatures and warm air.  This is at its peak in mid September – hence the peak of the hurricane season.  This year, these conditions are conducive for tropical storm development in the Pacific than in the Atlantic.  The storms what we haven’t had in the Atlantic have occurred in the Pacific basin.  The Atlantic has suffered from mild El Nino conditions and dry air intrusion into potential storms.  Much of the same adverse conditions as characterized the last several years.  A harbinger of things to come?





Global Warming - the basic principles


This is a big, important and timely subject.  Sea levels, melting ice, severe storms, hurricanes, crop, temperatures, and rainfall are some of the weather phenomena that are tied to the prospect of global warming. And like all predictions, the truth  (verification) isn’t certain until the future. It seems to have become politicalized. One of the problems in this debate is that both sides of the polarization have picked and chosen the data to support their conclusions. We see the truth only dimly now.

First, it is important to know what is meant by climate.  Here, it is simply a long-term change in the average weather.  Weather, the daily environment we are aware of (hot, cold, rain, etc.) is notoriously variable on a day-to-day basis.  But there are predictable changes, such as hotter in the summer than the winter, and dryer in the deserts than the tropics.  Those are climate variables.  When we speak of Global Climate Change we mean that everywhere on earth the average temperature for all seasons will be getting warmer with all the attendant changes that accompany weather.  But it does not necessarily mean that it will be uniformly warmer.   

Crucial to the understanding, I will have to lay some groundwork of how and why we experience temperature.  In the interests of clarity and simplicity, I will do some violence to some fascinating (to me) details. 

Before going any further, lets consider an analog of how the earth is warmed with the accompanying illustration.

Hurricane activity is distributed about nearly the Autumnal Equinox, not when the sun is highest in the sky. This can also explain why it is hotter at 5pm than when the sun is directly overhead at noon, as well as why hurricanes are at a maximum at the Autumnal Equinox  and not when the sun is highest in the sky at the Summer Solstice. 

At the top of the can of water is a hose that represents sunlight.  The water comes in and starts to fill up the tank.  But there is a spigot at the bottom that lets the water out.  The deeper the water in the tank the greater the pressure at the bottom and the more the water is forced out the bottom of the tank.  Eventually the water in the tank will reach an equilibrium level where the water leaving the tank equals the  water coming in. 

The water coming in represents the sunlight and the water leaving represents out going radiation and the level of the water in the tank represents the temperature. Lets first look at it for a single day.

The hose at the top start to input water at sunrise and the temperature (depth of water) rises.  At noon, the water flowing in is at its fastest rate.  After noon until dusk it is slowly shutting down.  Mean time, the water flowing out of the spigot at the bottom (representing the earth radiating out to space), is open 24 hours a day.  It actually radiates the most when the water level, representing the temperature, is the highest. As long as the water coming in is greater than the water leaving level will increase.  Incoming and out coming are equal in the mid-to-late afternoon, which explains why the temperature is the hottest in mid-to-late afternoon. After late in the afternoon not much sunlight is coming in and yet the outgoing radiation keep cooling and that continues until day break.  The water level (temperature) continues to drop all night long as the earth continues to radiate out to space. Seasons follow much the same logic, for as you go toward the poles the flow of water (sunlight) is not as strong and is “on” for a shorter and shorter time depending on the day of the year so the temperature is cooler.

Next – how this relates to global warming and hurricanes.





Extraterrestrial Life ? Part 2

We have discussed the importance of the size of a planet and also its distance from the sun. These two relationships govern the atmospheric composition and the temperature of the planet. They are critical for life on earth and any other planet.


It sounds like we are very very special and unique.  Well, not really, I think.  However, I also think we may never find out, so this may be just an interesting speculation for which no one can prove any position of belief they might have.  But we can speculate on the possibilities and even the probabilities.


We know that many and probably just about all stars have orbiting planets.  More and more are being found all the time.  There are 1022  (that is 1 with 22 zeros after it, or 10,000,000,000,000,000,000,000) stars in our Milky-Way galaxy.  That is a lot of stars and a lot of solar systems.  Astronomers think that as many as 1/3 of them have a planet about earth’s size about the same distance from their sun.  But lets assume that only one in a thousand have a planet that has conditions much like earth (same temperature and gravity and could have the same atmosphere) That lowers the number to 1019  Earth-like planets.  But we are not finished.  There are thought to be 1022  galaxies in the universe.  That means the number of total “Earths” is now 1041 !  That is too long a number to write out.  Now, how does life form?  That is a scientific and for some a theological question.  If given exactly the same conditions as Earth in which life formed, and if the chances of life forming were one in a million, then we would still have “life” on 1035  Earth-like planets with life of some kind. We are not alone.  Make the numbers as pessimistic as you want and, unless you say ab initio that life can only exist on Earth  no matter what, you must conclude life could exist elsewhere and that we could live there.   We must also recognize that the Periodic Table of all the elements is the same everywhere in the universe. All planets everywhere are made basically of the same stuff. There are no new elements, different physics, or different chemistry anywhere in the universe.


What would life be like?  Our DNA and all life from bacteria to plants to animals is a combination of the four bases that can be formed on a particular sugar backbone. That is simple organic chemistry.   The devil (or his opposite) is in the details.  But it is certainly possible that our, or some other chemical composition could form and create life.  The odds for this to happen are overwhelmingly good.  But it not at all clear that life anywhere else would resemble that on earth.  It could be much more “intelligent” or very rudimentary, or something in between.  SETI has been searching in vain for signs of intelligence for years.  Personally, I doubt we will ever discover any and even if we do, the distances are so enormous that I doubt there would ever be any form of communication.  Do I think there is life “out there”?  Yes.  Do I think we will ever benefit or be harmed by it?  NO.   I think we have our hands full here on Earth. 







Extraterrestrial Life ? Part 1

Ever since people understood that we are living on a planet that is part of a larger solar system, and then galaxy, and then universe, some have wondered if we were “alone”, as in unique, or if there might be intelligent life on some other planet, (assuming we have intelligent life on Earth).  Intelligence is relative.   More modestly, some wonder simply if there is “life” on some other planet.   It may be depressing, but for our solar system, we are the most intelligent life form, and with the possible exception, of Mars, the only place where it seems life can or is likely to exist.  And we will know relatively soon if life in any form ever existed on Mars.  My childhood dream of an alien civilization living along grand canals is just not the case.


First, what do we mean by life? Here I define life as something (and organism) that is self-sustaining and can replicate.  I don’t mean human or even intelligent life, or animal life, or any form of life such as exists on earth.  Just life.  That covers a wide range of existence. Life started on earth a long time ago, relatively soon after its formation.  How it started is not a known and subject to debate on many levels.


What makes a planet capable of sustaining or creating life?  What makes earth so special?  This is going to sound like Goldilocks and the three Bears.  First, it has to be the right distance from the sun, because any closer to the sun and it his too hot, and any further from the sun, it is too cold.  It has to be just the right size (as is Earth) to have an atmosphere that is neither carbon dioxide (as in a smaller planet) nor hydrogen (as in a larger planet).  Gravity (the size of the planet) is what holds the atmosphere and is key in determining what gasses will form and exist the atmosphere.  And the temperature (distance from the sun) makes it possible to have liquid water, which is a very useful ingredient in life.  We are looking for some place that if we were to go there that we could survive and adapt and even prosper.  And someplace where some form of life would be there to “greet” us.  Next article we will consider whether that is even possible or probable.

Lightning Protection

Briefly, the best protection is a Faraday cage, which is like being inside a metal bird cage or a metal trash can.  The best property protection, the gold standard, the lightening rod, was invented by Ben Franklin.  Lightening rods come in many forms.  There is the copper (or other good conductor) rod, the gulf club, umbrella, or even you will do in a pinch.  In the high country of Colorado, above the tree line, YOU are just what that highly charged cloud is looking for, and people die up there every year.  If you even think such a storm may be brewing, the best thing to do is RUN as fast as you can to be below the tree line. These storms can develop in 10 min or so and not even look impressive.  It is deceptive – for they are not innocent showers but efficient killers. 


A lightening rod’s range of protection extends outward about as far as it is tall. Different designs seek to increase that range with an array of various art-form pointy protuberances. They probably make some minor improvement in protection.   A thick copper wire connected to the lightning rods goes from the roof down the side of the house and into the ground (often about 4-6 feet) where the charge is dissipated within a few feet. 


A home thus properly protected does not draw potential lightning strikes from a neighbor’s house and thus your neighbors get no protection from your system. It does not significantly increase the potential of your house being hit, it just influences where it will be hit and do the least damage.


If you are in area where there are trees, you do not want to be next to a tall tree, or the lightning might decide it has had enough cellulose and wants some meat, and jump to you.  If you are too far away, then you become the lightening rod.  My personal belief is to be about  2/3 the distance away from the tree as the tree is tall. Even better, don’t be outside.  Inside a car is relatively safe, although scary.  It is not the tires that protect you -- it is the metal frame and body.  Some golf courses have metal shelters on  the course to provided protection for stranded golfers. If you can hear the thunder and particularly if it is less than a mile away, you are at risk.  The probabilities are still generally small, but that is little comfort to the 100 people who die from lightning strikes every year.


The Empire State building’s top is ringed with lightning rods, yet roughly 1/3 of the strikes hit the sides of the building.  Lighting is not always cooperative.   The tortured paths of some lightning stokes are unexplainable. 


Planes get hit by lightning all the time.  Since they are not electrically grounded and all sensitive components are protected by a version of a Faraday cage, the charge is normally just bled off the aircraft by wires that you often see on the wings.  For the electricity for flow through you, you must be grounded.  That is why birds and squirrels can perch and climb on a power line.  They are smart enough not to touch another wire, or they would have no progeny.  


Boat masts are obviously an attractive target.  A lightening rod with a large cable extending down the mast to an overboard metal plate below the water line offers the best protection to those on the boat in the open water. 


Your home appliances, including refrigerators, thermostats, ovens, lighting,  television, and of course computers are very vulnerable to power surges from lightning strikes.  It is unlikely that your house will be directly hit, but it does happen.  It is much more likely that a utility line will be hit, even at considerable distance from you home.  The electrical surge can enter your home.  It is quite possible that many of your appliances will not be protected and even the little strips that you plug your computer into may not be sufficient.  However, many utilities either rent or sell a much more effective surge protector that can go on your meter or in your circuit box.  According to our utility department, Tallahassee residents do not have that option of better protection.  Bottom line - how you respond to the threat of lightning is another example of risk analysis and cost/benefit assessment.


Specifically :

·      Avoid open areas where you are the tallest thing around

·      Do not be near poles (trees) and especially metal poles

·      Get away from open water.  If in a boat, have it grounded.

·      Generally get away from tall objects

·      Don’t go fly a kite.

·      Don’t  carry and  umbrella, golf club, metal bat, or flag pole.

·      Get into a car if possible

·      If in an open field and not a car, get in a ditch. Do not lie flat or be on your hands and knees, but crouch.  Hiding in a metal culvert is good.


If you say an oath that something is true -- and it is a lie, well, you are toast, or so I have been told.

More lightning facts

Thunder rumbles because the sound is bouncing off of trees building and hills and, with different paths and different lengths of time for the sound to reach you, it rumbles.  Thunder associate with a close lightning strike is a very loud single crack, seemingly simultaneous with the light.


A lightning channel has many branches that can also kill, or at least hurt you.  But if the main channel hits you, there is no survival. A fraction of a single amp can kill you, and it doesn’t take many volts either.  The current largely travels trough your blood vessels, as the salty blood is the path of least resistance.  It travels faster than nerve impulses can get to the brain, so you do not feel the pain.


If lighten is about to strike you, you will have advanced warning.  Every hair on you body will stand up. It is a weird feeling.  You have the time to say a (quick) prayer, and dive for some place safe (preferably at the same time as the prayer).  A Faraday cage is like a bird cage, or any metal enclosure, A Faraday cage, or inside any metal enclosure, offers protection.  But the best situation is not to be caught in that situation. 


The exception to the branched appearance of lightning is triggered lightning. This is man-made and usually accomplished by firing a rocket into the cloud just before lighting is going to strike. This rocket has a spool of wire attached to it and the wire unspools as the rocket ascends toward the cloud.  As soon as the rocket gets close to the highly electrified cloud, there is a bright flash that is perfectly straight, right down the wire, striking whatever the wire is attached to.  The prototype to this technique was made by Ben Franklin  in his famous kite experiment. Fortunately, he did NOT get struck by a full lightning discharge, but merely a week shock.  Had it been a lightening strike he certainly would have been the first innocent person who was deliberately  electrocuted. Many other scientists who set about to duplicate Franklin’s results had less fortunate outcomes. 


As a consequence of his, and subsequent fatal incarnations of this experiment, this particular experiment was removed from the list of approved 8th grade science fair projects. 


History might have been different.  If Franklin had died, he would not been able to charm the French court and help bring the aid of the French, which was important in our winning our War of Independence. We also would have missed his later inventions of bifocals, the glass armonica (or glass harmonica), a claw to reach distinct objects, the odometer, and the urinary catheter.  (Next week, more comments on lightning protection – promise)


Lightning Facts

You can build a static charge in low humidity conditions by rubbing a balloon against your hair, or dragging your feet across a motel carpet, etc. Materials with weakly bound electrons will transfer them to a material of tightly bound electrons when they are rubbed together.  But the spark you typically feel is only 1% of what it would take to kill you.  The most you can get is 30% of a lethal jolt, which will not kill you  -- but I promise you it will leave a lasting memory. 


Lightening occurs in Florida mostly in the summer months.  All of Florida has a lot of lightening, but the peninsula has the most lightening and also the most rainfall.


Ice in a thunderstorm exists in two forms. In one form, super cooled liquid cloud droplets freeze on contact with ice, forming a conglomerate of really tiny balls of ice.  This is called riming.   As riming continues, and the piece of ice gets bigger, it is called graupel. (Bigger still, the same frozen ball is called a hail stone). 


In the other process, water vapor molecules in the air move to, and attach themselves to a particular vacant space on a hexagonal crystal of ice. These hexagons fit together very nicely and make bigger and bigger ice crystals. As this continues, the ice crystal grows and can take the form of a rod, a plate or the familiar, ubiquitous, and beautiful snowflake.


No one knows the details of how lightening forms in thunderstorms, but it clearly has to do with the difference in the surface electro-chemistry between these two forms of ice.  When these two different forms of ice collide, there is a flow of electrons from the graupel (frozen drops) to the ice crystal as long as the temperature is warmer than -20 deg. C. At temperatures    below -20 deg. C (the reversal temperature), the electrons flow the other way so that the heavier graupel accumulates negative charge and the ice crystals become positively charged.  The lighter crystals rise in the updraft and the heaver graupel falls, separating the charge. So the thunderstorm starts out being negatively charged at the top and then as it grows, it becomes positively charged at the top and the negative charge accumulates near the bottom.  


In a practical sense, only the electrons move so that when something is positively charged, it has lost electrons.  Even though the earth has a net negative charge (thanks to all the lightening strikes) the earth below the thunderstorm becomes positively charged since, by induction, the negative charges on the earth leave beneath the storm as the negatively charged storm base repels the negative charges on the ground. 


Thanks to Ben Franklin, current flow is defined as the direction a positive test charged would move.  So it is in the opposite direction of the flow of electrons. Backwards.


As the potential difference grows, eventually it reaches the breakdown potential, and, just like when you get a static discharge, you get a lightening bolt.  It is complicated, as the spark goes in a series of steps, looking for the shortest electrical path, which isn’t necessarily the shortest geometric path. It does this in a succession of steps until it finds the perfect path close to the ground and then “hooks up”. The electrons flow in spurts down the ionized channel at 60,000 miles per second or 1/3 the speed of light, and eventually the illumination move from the ground up, much as a line of cars react to a stop-light turning green.  This is quickly repeated as the region of the discharge expands throughout the cloud. The lightning bolt may contain a current load is as high as 230,000 amps and have over a billion volts. No wonder lightening kills.


We hear the thunder from the powerful lightening bolts between cloud and ground. But 90% of the lightening is going on within the cloud with path lengths from centimeters (or less) to meters and everything in-between. These can only be detected by special equipment.


Next – how to protect yourself and things from lightning.