The Climate Trap

The Climate Trap

People are suckers for a horror story

The Wall Street Journal 5 June 2018 included a short article on climate change, and how interest in that subject has faded. This fluctuating attitude toward climate change is a classic illustration of the ‘Issue Attention Cycle’ written by political scientist Anthony Downs in 1972, which characterizes the rise and fall of hysteria about things of this sort.

Climate change followed the exact same trajectory as those other made-up or grossly exaggerated tragedies. People said in deadly earnest that the earth would be a frozen snowball before the turn of the 21st-century.  And then, abruptly, we were all going to fry instead as the CO2 – or was it water vapor? No, no, it was the lack of argon in the atmosphere – that spelled doom for all inhabitants of our incredibly fragile planet.

It isn’t that we don’t care.  It isn’t that climate won’t change – it most certainly will, that’s what climates do.  It is that the usual suspects screaming the usual incitements to panic were doing their usual damage to our national psyche by raising alarm for an issue over which we had no control, as they’ve been doing for decades over any issues ready to hand no matter how trivial or far-fetched.

And at the same time, the usual malefactors were beating a path to the bank with the money they had grabbed from all those whose care went as deep as their pocketbooks. That is what this hysteria has become, as all the previous ones also did: a gigantic money grab.

It’s a principle tried-and-true. Some obscure Greek philosopher probably wrote about it, and if we were to unearth his writings, they would probably say “Watch out for that man among you who yells loudest about [insert clichéd concern] for he is full of garbanzo bean curd.  And grab your wallet.”

Al Gore is a high priest of that temple; Henry David Thoreau and Theodore Roosevelt are historic members still held in high esteem. The reputations that these people had, themselves, overshadow the more pedestrian efforts of many of their acolytes. John Muir was instrumental in getting the land which was designated Yosemite National Park, but Barack Obama abused the powers of his office to designate millions of acres of Utah and Nevadaas national forests, a ploy to keep petroleum exploration off the land.

From Wikipedia:

Global cooling was a conjecture during the 1970s of imminent cooling of the Earth’s surface and atmosphere culminating in a period of extensive glaciation…

As this writer remembers it, during the 1970s there was vast concern about the trend since the 1940s of temperatures on earth dropping precipitously. The big concern was that we all would freeze to death and starve along the way as global vegetation died out from the eternal winners forecast. Add to that the Arab Oil Embargo of 1973 and 1978 and there was mounting hysteria across the US.

These articles appeared in publications of the day:

“U.S. Scientist Sees New Ice Age Coming”  Washington Post, July 9, 1971

“Another Ice Age?”  Time magazine,  June 24, 1974

“Scientists Ask Why World Climate Is Changing:  Major Cooling May Be Ahead.”  New York Times, May 21, 1975

“Climate experts believe the next ice age is on its way.” – Leonard Nimoy, 1978

Well, Mr. Spock said so: we can take that to the bank and get our future in Federation Credits.

And there was a movie on a totally unrelated subject with a similar result.  As the New York Times gushed:

“The Day After,” ABC’s much-discussed vision of nuclear Armageddon, is no longer only a television film, of course; it has become an event, a rally and a controversy, much of it orchestrated.

… Much of it orchestrated! In the heart of the furor, at the time of the absolute maximum level of hype, the New York Times of all entities saw through all of the blather and called into question the origins of the national fascination with a ‘nuclear winter.’

The Grey Lady was a different paper then. The ownership was the Sulzberger family, represented by “Punch” Sulzberger who was a solid news man and ran a tight ship.

Things have changed. Arthur Sulzberger has now taken the helm, and the Times is now a mere opinion rag whose editorial policy runs to the far left, automatically giving short shrift to anything Republican or conservative.

So, the Times was a harbinger of all the hoopla about climate change, and along with its editorial change came a sea-change in the national mood. In approximately eight years all of the dread surrounding global cooling dissipated. The mind boggles to consider how easily the misconceptions that had been held since World War II were replaced by new misconceptions of a totally opposite nature.  Perhaps there was simply more opportunity for bilking the public when they think of a steamy sweaty future then of one where a heavier coat is all you need?

We try to illustrate our articles if possible, but in searching for meaningful photographs of global warming, we obtained precisely 0. The content that we did find from CBS News was laughably inappropriate to a world supposedly getting warmer, where the seas would rise and plant life would grow lush. It seems that in the midst of this humid tropical nightmare, there would be pathetic looking children starving, trees bursting into flames – all that rain must make them prone to fire, and the receding shorelines of lakes and the oceans leaving expensive houses high and dry.  Weren’t the oceans supposed to rise? It makes us long for the days of Mr. “Fake but Accurate” Dan Rather.

With a new fear came a new set of demons: Evil Oil, Nuclear Armageddon, Choking Coal. Burning fuels was at the root of the problem. Fuel= Heat. Simple equation, simple solution – get rid of the fuel, get rid of the heat.

The left has been on the warpath about fossil fuels for decades. Coal is nasty and smelly, heating oil is too. Nuclear plants produce nuclear waste which can only be stored away in that mountain that Harry Reid won’t let us use in Nevada. Nuclear plants do something to the environment, don’t they? Or they’re just dangerous. Look at 3 Mile Island!

Yes, let’s look at 3 Mile Island. From the Nuclear Regulatory Commission’s report entitled “Backgrounder on the 3 Mile Island Accident”:

The Three Mile Island Unit 2 (TMI-2) reactor, near Middletown, Pa., partially melted down on March 28, 1979. This was the most serious accident in U.S. commercial nuclear power plant operating history, although its small radioactive releases had no detectable health effects on plant workers or the public. Its aftermath brought about sweeping changes involving emergency response planning, reactor operator training, human factors engineering, radiation protection, and many other areas of nuclear power plant operations. It also caused the NRC to tighten and heighten its regulatory oversight. All of these changes significantly enhanced U.S. reactor safety. [emphasis added]

In other words, nothing happened. There was an accident, and in theory it could have been serious, but safeguards put into place at the Three Mile Island Plant worked in spite of all the worst efforts of the incompetent management of the plant. The result was simply the deactivation of the plant and the removal of its nuclear fuel.

The NRC report took over a decade to produce. It was a fiasco of major proportion, leading to hysterical fright of nuclear power that is still in existence today.

Japan, where there really have been nuclear disasters – Hiroshima, Nagasaki, and more recently, Fukushima – routinely handles the potential problems of nuclear plants with detached aplomb. They have learned to live with it and not be obsessed.

The left has a penchant for seizing upon some characteristic of an offending but otherwise beneficent technology and making that into the greatest evil since Beelzebub rose from hell. The mischaracterization of Three Mile Island as a study in everything that is wrong with nuclear power has been successfully marketed and maintained as the definitive study of nuclear evils.

In the world of reality, where we need energy sources aplenty, there have been, recently, people wondering out loud the verboten topic, “What’s wrong with nuclear power?” What, exactly, is wrong with nuclear power? Japan, France and many other European countries produce their share, but the largest nuclear producer is the US.

We only hear about nuclear energy when there’s a problem, and there usually are not problems. Nuclear plants do not fit into the narrative of the left that makes fossil fueled energy the demon. So, they make up other things about it and use an ‘almost accident’ nearly 40 years ago to spark opposition to a technology that others around the world are using successfully.


Is the globe warming? Maybe. Is it dangerous to our future? Maybe. Is it warming because we burn fossil fuels? Maybe. Will switching to solar energy completely solve our problem? No. How about wind energy? No. How about solar and wind? No.

The amount of solar, wind, and hydroelectric (all-renewables) energy in use right now in the United States is about 18% as of early in 2018, this according to Forbes magazine. That 18% number is growing, quickly, but it has a long way to go before it supplants our traditional sources. And the percentage of energy available from those two sources on a cloudy, still day is7% – the hydroelectric component – and always will be unless more dams are built.  Because of this, the productivity numbers used for aged solar and wind facilities are at best optimistic and at worst utter lies.

As we contend with Global Wa – oops – Climate Change, we must remain cognizant of the fact: that if the oceans rise to a point where only the tip of Liberty’s torch remains dry as Al Gore tried to warn us, we will experience the horrors of vast fertile plains populated with the proverbial fruit in quantities that would make a Florida grove owner blanche with envy.  Of course the Democrats would figure out a new way to tax our emerging excesses.

This, however, is a future that we do not control, filtered by people whose imaginations are uncontrollable. Doomsayers will see a time of gloom, and the rest of us will go about our daily lives, coping as we must with the change as it comes. We do have time: after all, Al Gore’s sea rise would take centuries or at least a century if they ever come to pass. Lady Liberty can be moved to safe ground if that is necessary, and the swelling oceans will render great increases in property values along certain coasts.

The Left decided with the help of the mainstream media that, since Global Warming had become a joke, its name had to be changed. After all, the way something is retained in the mind is by its name and, if a name becomes embarrassing, use the Soviet method and change it!

So they did. There was no reason to draw attention to the fact that weather is always changing; every TV and radio station tells us that hourly.  But it is still all about the money – even the Communists are in it for the money.

It doesn’t matter what you call it.  Global Cooling, Nuclear Winter, Global Warming – all these buzzwords are merely the strident mantras of the left that call to mind all those things that they need us to give up – namely, the energy that drives modern society and provides the maximum individual freedom to the ordinary person ever seen in the history of the world.

Instead, the warmist left is running into the old theme that dates back to the days of Aesop’s story, “The Boy Who Cried Wolf.” It isn’t that people don’t care, just that they’ve heard enough and are sick of it.

Chances are that, like Three Mile Island, it’s all Shakespearean: Much Ado About Nothing.  Humanity can handle whatever changes come, as we’ve handled the Ice Age, the Black Plague, and Britney Spears: suffering for a time, but bigger, better, and stronger afterwards.  If we don’t lose our nerve.

The Sea Is Rising

The Sea Is Rising, but Not Because of Climate Change

There is nothing we can do about it, except to build dikes and sea walls a little bit higher.

Ice crevasses near the coast of West Antarctica.
Ice crevasses near the coast of West Antarctica. PHOTO: MARIO TAMA/GETTY IMAGES

Of all known and imagined consequences of climate change, many people fear sea-level rise most. But efforts to determine what causes seas to rise are marred by poor data and disagreements about methodology. The noted oceanographer Walter Munk referred to sea-level rise as an “enigma”; it has also been called a riddle and a puzzle.

It is generally thought that sea-level rise accelerates mainly by thermal expansion of sea water, the so-called steric component. But by studying a very short time interval, it is possible to sidestep most of the complications, like “isostatic adjustment” of the shoreline (as continents rise after the overlying ice has melted) and “subsidence” of the shoreline (as ground water and minerals are extracted).

I chose to assess the sea-level trend from 1915-45, when a genuine, independently confirmed warming of approximately 0.5 degree Celsius occurred. I note particularly that sea-level rise is not affected by the warming; it continues at the same rate, 1.8 millimeters a year, according to a 1990 review by Andrew S. Trupin and John Wahr. I therefore conclude—contrary to the general wisdom—that the temperature of sea water has no direct effect on sea-level rise. That means neither does the atmospheric content of carbon dioxide.

This conclusion is worth highlighting: It shows that sea-level rise does not depend on the use of fossil fuels. The evidence should allay fear that the release of additional CO2 will increase sea-level rise.

But there is also good data showing sea levels are in fact rising at an accelerating rate. The trend has been measured by a network of tidal gauges, many of which have been collecting data for over a century.

The cause of the trend is a puzzle. Physics demands that water expand as its temperature increases. But to keep the rate of rise constant, as observed, expansion of sea water evidently must be offset by something else. What could that be? I conclude that it must be ice accumulation, through evaporation of ocean water, and subsequent precipitation turning into ice. Evidence suggests that accumulation of ice on the Antarctic continent has been offsetting the steric effect for at least several centuries.

It is difficult to explain why evaporation of seawater produces approximately 100% cancellation of expansion. My method of analysis considers two related physical phenomena: thermal expansion of water and evaporation of water molecules. But if evaporation offsets thermal expansion, the net effect is of course close to zero. What then is the real cause of sea-level rise of 1 to 2 millimeters a year?

Melting of glaciers and ice sheets adds water to the ocean and causes sea levels to rise. (Recall though that the melting of floating sea ice adds no water to the oceans, and hence does not affect the sea level.) After the rapid melting away of northern ice sheets, the slow melting of Antarctic ice at the periphery of the continent may be the main cause of current sea-level rise.

All this, because it is much warmer now than 12,000 years ago, at the end of the most recent glaciation. Yet there is little heat available in the Antarctic to support melting.

We can see melting happening right now at the Ross Ice Shelf of the West Antarctic Ice Sheet. Geologists have tracked Ross’s slow disappearance, and glaciologist Robert Bindschadler predicts the ice shelf will melt completely within about 7,000 years, gradually raising the sea level as it goes.

Of course, a lot can happen in 7,000 years. The onset of a new glaciation could cause the sea level to stop rising. It could even fall 400 feet, to the level at the last glaciation maximum 18,000 years ago.

Currently, sea-level rise does not seem to depend on ocean temperature, and certainly not on CO2. We can expect the sea to continue rising at about the present rate for the foreseeable future. By 2100 the seas will rise another 6 inches or so—a far cry from Al Gore’s alarming numbers. There is nothing we can do about rising sea levels in the meantime. We’d better build dikes and sea walls a little bit higher.

Mr. Singer is a professor emeritus of environmental science at the University of Virginia. He founded the Science and Environmental Policy Project and the Nongovernmental International Panel on Climate Change.

Appeared in the May 16, 2018, print edition.


Scott Rasmussen’s Number of the Day


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By Scott Rasmussen

August 21, 2017: Twenty-eight percent (28%) of Americans think that climate scientists understand the causes of global climate change “very well.” A Pew Research study found that only 19% believe that the climate scientists have a very good understanding of the best ways to address the issue.[1]

In general, the study found that Americans trust climate scientists more than politicians on the topic. Two-thirds (67%) believe scientists should play a major role in addressing policy issues on the matter. Most (56%) also believe that energy industry leaders (56%) and the general public (56%) should have a major say in such policy topics.

The Pew study, however, also found that people believe there are differences of opinion among the climate scientists. Only 27% believe that there is a consensus on the issue and that just about all climate scientists believe human behavior is mostly responsible for global climate change. Another 35% think more than half hold this view.

The survey also explored the degree of trust and confidence in those researching climate science. Thirty-six percent (36%) believe that, most of the time, scientists’ research findings are motivated by a desire to advance their own careers. Only 32% say that they mostly rely on the best scientific evidence. Twenty-seven percent (27%) believe that political views of the scientists generally influence their work.

Liberal Democrats tend to express high levels of confidence in the climate scientists and their motives. Conservative Republicans are often quite skeptical. Most other Americans have mixed views.

Research findings influenced by… Percentage responding “most of the time”
Desire to advance their own career 36%
Best available scientific evidence 32%
Personal political leanings 27%
Desire to help the industries they work with or for 26%
Concern for best interests of the public 23%

Most Americans (55%) believe that new technology will probably solve most of the problems from climate change.

Al Gore’s Climate Sequel

Al Gore’s Climate Sequel Misses a Few Inconvenient Facts

Eleven years after his first climate-change film, he’s still trying to scare you into saving the world.

Al Gore in Washington, July 20.
Al Gore in Washington, July 20. PHOTO: GETTY IMAGES

They say the sequel is always worse than the original, but Al Gore’s first film set the bar pretty low. Eleven years ago, “An Inconvenient Truth” hyped global warming by relying more on scare tactics than science. This weekend Mr. Gore is back with “An Inconvenient Sequel: Truth to Power.” If the trailer is any indication, it promises to be more of the same.

The former vice president has a poor record. Over the past 11 years Mr. Gore has suggested that global warming had caused an increase in tornadoes, that Mount Kilimanjaro’s glacier would disappear by 2016, and that the Arctic summers could be ice-free as soon as 2014. These predictions and claims all proved wrong.

“An Inconvenient Truth” promoted the frightening narrative that higher temperatures mean more extreme weather, especially hurricanes. The movie poster showed a hurricane emerging from a smokestack. Mr. Gore appears to double down on this by declaring in the new film’s trailer: “Storms get stronger and more destructive. Watch the water splash off the city. This is global warming.”

This is misleading. The Intergovernmental Panel on Climate Change—in its Fifth Assessment Report, published in 2013—found “low confidence” of increased hurricane activity to date because of global warming. Storms are causing more damage, but primarily because more wealthy people choose to live on the coast, not because of rising temperatures.

Even if tropical storms strengthen by 2100, their relative cost likely will decrease. In a 2012 article for the journal Nature Climate Change, researchers showed that hurricane damage now costs 0.04% of global gross domestic product. If climate change makes hurricanes stronger, absolute costs will double by 2100. But the world will also be much wealthier and less vulnerable, so the total damage is estimated at only 0.02% of global GDP.

In the trailer, Mr. Gore addresses “the most criticized scene” of his previous documentary, which suggested that “the combination of sea-level rise and storm surge would flood the 9/11 Memorial site.” Then viewers are shown footage of Manhattan taking on water in 2012 after superstorm Sandy, apparently vindicating Mr. Gore’s claims. Never mind that what he actually predicted was flooding caused by melting ice in Greenland.

More important is that Mr. Gore’s prescriptions—for New York and the globe—won’t work. He claims the answer to warming lies in agreements to cut carbon that would cost trillions of dollars. That would not have stopped Sandy. What New York really needs is better infrastructure: sea walls, storm doors for the subway, porous pavement. These fixes could cost around $100 million a year, a bargain compared with the price of international climate treaties.

Mr. Gore helped negotiate the first major global agreement on climate, the Kyoto Protocol. It did nothing to reduce emissions (and therefore to rein in temperatures), according to a March 2017 article in the Journal of Environmental Economics and Management. Undaunted, Mr. Gore still endorses the same solution, and the new documentary depicts him roaming the halls of the Paris climate conference.

By 2030 the Paris climate accord will cost the world up to $2 trillion a year, mostly in lost economic growth, according to the best peer-reviewed energy-economic models. It will remain that expensive for the rest of the century. This would make it the most expensive treaty in history.

And for what? Just ahead of the Paris conference, the United Nations Framework Convention on Climate Change estimated that if every country fulfills every promised Paris carbon cut between 2016 and 2030, carbon dioxide emissions will drop by only 60 gigatons over that time frame. To keep the temperature rise below 2 degrees Celsius, the world must reduce such emissions nearly 6,000 gigatons over this century, according to the IPCC. A “successful” Paris agreement wouldn’t even come close to solving the problem.

Mr. Gore argues that the Paris approach pushes nations and businesses toward green energy. Perhaps, but the global economy is far from ready to replace fossil fuels with solar and wind. The International Energy Agency, in its 2016 World Energy Outlook, found that 0.6% of the world’s energy is supplied by solar and wind. Even with the Paris accord fully implemented, that number would rise only to 3% in a quarter-century.

In part because of activists like Mr. Gore, the world remains focused on subsidizing inefficient, unreliable technology, rather than investing in research to push down the price of green energy. Real progress in Paris could be found on the sidelines, where philanthropist Bill Gates and others, including political leaders, agreed to increase spending on research and development. This is an important start, but much more funding is needed.

Mr. Gore declares in his new film that “it is right to save humanity.” No argument here. But is using scare tactics really the best way to go about it?

Mr. Lomborg is the president of the Copenhagen Consensus Center and the author of “The Skeptical Environmentalist” and “Cool It.”

Wrong predictions

An Earth Day Education

An Earth Day Education

Somehow life keeps getting better.

A man walks past a mural on Friday in Philadelphia.

A man walks past a mural on Friday in Philadelphia. PHOTO: MATT ROURKE/ASSOCIATED PRESS

Just in time for Saturday’s Earth Day forecasts of environmental apocalypse, economist Mark Perry provides a helpful reminder of the accuracy of previous eco-prophecies. Specifically, he notes “18 spectacularly wrong predictions” made around the time of the first Earth Day in 1970.

Inconvenient Weather Fact for Earth Day: US is in the longest strong hurricane drought (11+ years) in history 

Photo published for 18 spectacularly wrong predictions made around the time of first Earth Day in 1970, expect more...

18 spectacularly wrong predictions made around the time of first Earth Day in 1970, expect more…

In the May 2000 issue of Reason Magazine, award-winning science correspondent Ronald Bailey wrote an excellent article titled “Earth Day, Then and Now” to

Perhaps because earlier predictions of catastrophe were off target, it’s clear that in 2017 many of Earth’s inhabitants are still not persuaded that their planet is doomed. But Earth Day Network President Kathleen Rogers may have a solution for this. She writes for CNN today about her organization’s “campaign to bring climate and environmental literacy to the world.”

Ms. Brown explains: “Climate literacy is now recognized universally as the engine for driving individual behavioral change, building consumer support for a green economy, creating green technologies and jobs, and promoting policy reforms at all levels of government. Recognizing the importance of an educated global population, the authors of the Paris Climate Agreement put climate education at its heart, calling on national governments to cooperate in taking measures to enhance climate education, training and access to information.”

This column would like to do its part by sharing a valuable history lesson, thanks to Mr. Perry and also to my onetime colleague Ronald Bailey, who in a 2000 piece for Reason magazine looked back at the first Earth Day. Here’s what Mr. Bailey wrote on the 30th anniversary of that landmark eco-happening:

Imminent global famine caused by the explosion of the “population bomb” was the big issue on Earth Day 1970. Then–and now–the most prominent prophet of population doom was Stanford University biologist Paul Ehrlich. Dubbed “ecology’s angry lobbyist” by Life magazine, the gloomy Ehrlich was quoted everywhere. “Population will inevitably and completely outstrip whatever small increases in food supplies we make,” he confidently declared in an interview with then-radical journalist Peter Collier in the April 1970 Mademoiselle. “The death rate will increase until at least 100-200 million people per year will be starving to death during the next ten years.”

“Most of the people who are going to die in the greatest cataclysm in the history of man have already been born,” wrote Ehrlich in an essay titled “Eco-Catastrophe!,” which ran in the special Earth Day issue of the radical magazine Ramparts. “By…[1975] some experts feel that food shortages will have escalated the present level of world hunger and starvation into famines of unbelievable proportions. Other experts, more optimistic, think the ultimate food-population collision will not occur until the decade of the 1980s.” Ehrlich sketched out his most alarmist scenario for the Earth Day issue of The Progressive, assuring readers that between 1980 and 1989, some 4 billion people, including 65 million Americans, would perish in the “Great Die-Off.”

Readers old enough to remember the 1980s should be forgiven if they can’t quite seem to recall a famine wiping out most of the world’s population. As Mr. Bailey noted in assessing the accuracy of Mr. Ehrlich’s predictions:

Time has not been gentle with these prophecies. It’s absolutely true that far too many people remain poor and hungry in the world–800 million people are still malnourished and nearly 1.2 billion live on less than a dollar a day–but we have not seen mass starvation around the world in the past three decades. Where we have seen famines, such as in Somalia and Ethiopia, they are invariably the result of war and political instability. Indeed, far from turning brown, the Green Revolution has never been so verdant. Food production has handily outpaced population growth and food today is cheaper and more abundant than ever before. Since 1970, the amount of food per person globally has increased by 26 percent, and as the International Food Policy Research Institute reported in October 1999, “World market prices for wheat, maize, and rice, adjusted for inflation, are the lowest they have been in the last century.”

Since Mr. Bailey wrote those words in 2000, anyone still waiting for the Great Die-Off to begin has been continually disappointed. In fact, the fifteen years after 2000 could reasonably be called the “Great Live-On.” According to the World Health Organization, “Global average life expectancy increased by 5 years between 2000 and 2015, the fastest increase since the 1960s.” Increases in life expectancy were greatest in Africa, adds the WHO, thanks in large part to “expanded access to antiretrovirals for treatment of HIV.” In other words, the products of advanced industrialized societies were not destroying life, but saving it.

Back in 2000, Mr. Bailey did make a few predictions of his own regarding the celebration of Earth Day in 2030. He predicted better diets and longer lives for people world-wide, as well as another interesting forecast: “There will be a disproportionately influential group of doomsters predicting that the future–and the present–never looked so bleak.”


Milankovitch Cycles and Glaciation

The episodic nature of the Earth’s glacial and interglacial periods within the present Ice Age (the last couple of million years) have been caused primarily by cyclical changes in the Earth’s circumnavigation of the Sun. Variations in the Earth’s eccentricity, axial tilt, and precession comprise the three dominant cycles, collectively known as the Milankovitch Cycles for Milutin Milankovitch, the Serbian astronomer and mathematician who is generally credited with calculating their magnitude. Taken in unison, variations in these three cycles creates alterations in the seasonality of solar radiation reaching the Earth’s surface. These times of increased or decreased solar radiation directly influence the Earth’s climate system, thus impacting the advance and retreat of Earth’s glaciers.

It is of primary importance to explain that climate change, and subsequent periods of glaciation, resulting from the following three variables is not due to the total amount of solar energy reaching Earth. The three Milankovitch Cycles impact the seasonality and location of solar energy around the Earth, thus impacting contrasts between the seasons.


The first of the three Milankovitch Cycles is the Earth’s eccentricity. Eccentricity is, simply, the shape of the Earth’s orbit around the Sun. This constantly fluctuating, orbital shape ranges between more and less elliptical (0 to 5% ellipticity) on a cycle of about 100,000 years. These oscillations, from more elliptic to less elliptic, are of prime importance to glaciation in that it alters the distance from the Earth to the Sun, thus changing the distance the Sun’s short wave radiation must travel to reach Earth, subsequently reducing or increasing the amount of radiation received at the Earth’s surface in different seasons.

Today a difference of only about 3 percent occurs between aphelion (farthest point) and perihelion (closest point). This 3 percent difference in distance means that Earth experiences a 6 percent increase in received solar energy in January than in July. This 6 percent range of variability is not always the case, however. When the Earth’s orbit is most elliptical the amount of solar energy received at the perihelion would be in the range of 20 to 30 percent more than at aphelion. Most certainly these continually altering amounts of received solar energy around the globe result in prominent changes in the Earth’s climate and glacial regimes. At present the orbital eccentricity is nearly at the minimum of its cycle.

Axial Tilt

Axial tilt, the second of the three Milankovitch Cycles, is the inclination of the Earth’s axis in relation to its plane of orbit around the Sun. Oscillations in the degree of Earth’s axial tilt occur on a periodicity of 41,000 years from 21.5 to 24.5 degrees.

Today the Earth’s axial tilt is about 23.5 degrees, which largely accounts for our seasons. Because of the periodic variations of this angle the severity of the Earth’s seasons changes. With less axial tilt the Sun’s solar radiation is more evenly distributed between winter and summer. However, less tilt also increases the difference in radiation receipts between the equatorial and polar regions.

One hypothesis for Earth’s reaction to a smaller degree of axial tilt is that it would promote the growth of ice sheets. This response would be due to a warmer winter, in which warmer air would be able to hold more moisture, and subsequently produce a greater amount of snowfall. In addition, summer temperatures would be cooler, resulting in less melting of the winter’s accumulation. At present, axial tilt is in the middle of its range.


The third and final of the Milankovitch Cycles is Earth’s precession. Precession is the Earth’s slow wobble as it spins on axis. This wobbling of the Earth on its axis can be likened to a top running down, and beginning to wobble back and forth on its axis. The precession of Earth wobbles from pointing at Polaris (North Star) to pointing at the star Vega. When this shift to the axis pointing at Vega occurs, Vega would then be considered the North Star. This top-like wobble, or precession, has a periodicity of 23,000 years.

Due to this wobble a climatically significant alteration must take place. When the axis is tilted towards Vega the positions of the Northern Hemisphere winter and summer solstices will coincide with the aphelion and perihelion, respectively. This means that the Northern Hemisphere will experience winter when the Earth is furthest from the Sun and summer when the Earth is closest to the Sun. This coincidence will result in greater seasonal contrasts. At present, the Earth is at perihelion very close to the winter solstice.