Milutin Milanković was a Serbian climatologist who back in the 1920s put forward theories concerning how variations in the Earth’s orbit and axial tilt might affect the amount of solar radiation impinging on the Earth (now known as the Milanković cycles) so causing periodic variations in the Earth’s climate (eg, ice ages).
He wasn’t the first but by his time it was possible to measure these variations and geology was sufficiently advanced to verify his conclusions on the ground.
Milutin Milanković, 1879-1958
The Variations
Eccentricity. The orbit of the Earth is not circular but an ellipse. The ellipse is not constant as it is affected by the gravity of Saturn and Jupiter. The long axis of the ellipse also moves around in a 112,000 year cycle.
Velocity. The speed of the Earth is not constant, due to the elliptical orbit. This affects the length of the seasons. For example, if the Earth is moving slower during Winter, Winter will be longer.
These two combined repeat every 100,000 years.
Tilt. The Earth’s axis is tilted with respect to the orbital plane. This too varies between 22 and 24.5 degrees, Another cycle repeating every 41,000 years.
Precession (Wobble). The Earth wobbles like a top slowing down. Each wobble lasts 25,771 years. (Now isn’t that an exact figure!) This is caused by the sun and moon.
Orbital tilt. Relative to the average for the rest of the solar system. This is about 1.5 degrees but varies over a 70,000 year or 100,000 year period depending on how measured.
All of these factors have a tiny effect on the amount of solar radiation falling on the Earth. However, at regular intervals, all of the maxima coincide and we get an exceptionally warm or cold period. Milankovic reckoned the complete combined cycle lasted 45.000 years.
However, there was a problem; geological/glacier evidence pointed to a 100,000 year cycle. In fact, it turned out to be even more complex. A few million years ago we did have a 45,000 year cycle only more recently have we got a 100,000 year cycle. The reasons are unclear but all agreed we were heading for an ice age in a few thousand years. For example, John Imbrie, a more recent sage (1980s), reckoned that a long term cooling cycle that began 6,000 years ago would continue for the next 23,000 years.
But Err…we are actually warming, fast, by climatological standards. Clearly something was overriding the reduction in solar radiation we are having as we were heading for the next ice age. There have been glitches in the past caused by massive volcanic eruptions. Interestingly, these have made things cooler by reason of volcanic ash thrown high in the atmosphere reflecting the sun’s rays. The latest glitch was the 1991 eruption of Mt Pinatubo, which lowered the global temperature by 0.5 to 0.6°C for a couple of years.
Greenhouse Gases
Simultaneous research had been going on into “greenhouse gases,” which slow down heat losses from our planet. The main ones are water vapour, carbon dioxide and methane. Four billion years ago, the Earth’s atmosphere was nitrogen and carbon dioxide. There was a massive greenhouse effect. Fortunately the Earth was further away and the sun not so bright at that time.
Only because the Earth has a benign climate was plant life able to evolve and turn the carbon dioxide into oxygen and carbon. Some of the carbon got locked away in the ground, fortunately for us. Some of the carbon dioxide got locked way as limestone (sea shells) as marine life evolved. The chances of the above happening were vanishingly small, but here we all are. Without the greenhouse gases in the atmosphere creating a warming effect, we would never exist.
The system is in a fine balance; little disruption is needed to upset things. This is because of runaway or “positive feedback” effects. All positive feedback systems are inherently unstable. So, a slight warming effect sets off other events that add to the effect. For example, we now have a situation where arctic permafrost bogs are melting and releasing methane (a strong greenhouse gas). As ice and snow disappear, the surface of the Earth becomes less reflective (albedo) of solar radiation. As the sea warms, frozen undersea methane is released from huge reserves of methane hydrate on the ocean floors. Soot from industrial pollution lands on glaciers, so making them less reflective of the sunlight and thus melt faster. Natural gas exploration also releases methane gas (especially fracking).
Once these emissions are initiated, they are impossible to stop and they will get worse. This is why it’s imperative to reduce emissions of CO2. As the atmosphere warms, it holds more water vapour, again boosting the greenhouse effect. But then, there might be more clouds which would reflect solar radiation. There are lots of unknowns and unquantifiables. However, doing nothing is not an option; the consequences would be massive disruption to the eco-system, the world economy and all our lives.
I hear the sceptical say, “How can even a degree of global warming make that much difference?” Well, our weather systems are driven by temperature differences not absolute temperature. A four-degree difference can drive a lethal storm, if it were five degrees it would be far worse. Anyone born around the middle of the last century has witnessed global warming. When I was a child, non-white Christmases were rare. Snow-free Winters were unknown. Every child had a sledge. Most of them these days don’t even know what one is. Once uncommon weather events are becoming the new norm. Australia has gone from desiccation to extreme rain overnight. Locally, we have had four separate flood events in as many weeks.
We now seem to have a culture of telling people what they want to hear as opposed to truth (started by politicians). We have got to the stage where they just don’t listen to bad news. Lots of them don’t want their comfortable existence disturbed but it will happen. There will be economic consequences arising from the effects of climate change for everyone. Well, ignoring it won’t make it go away. As an example there must be thousands now ruing the day they ignored advice about buying houses liable to flooding. The recent flooding severely affected food production and this will get worse, resulting in shortages and price hikes.
Furthermore, we ain’t seen nuthin’ yet, we all need to be preparing.
Dangerous man-made climate change is a human issue and humans are so emotional. They are also gullible.
Having read so much science on the causes of climate change, of whether CO2 is a demon molecule, and of the imminent catastrophe of global warming, it was necessary, eventually, to take stock.
My conclusion was that the scientists, that is the real scientists, don’t know. They can hypothesize, make their models, and draw their conclusions, but they do not know.
Then we return to the humanities and remember what we are, emotional animals prone to belief, tribalism, commitment, greed, fear, aggrandizement and a whole host of other traits. In the end those traits get in the way of common sense and logic.
Of course the humanities are not science, and never will be, but that is where we find ourselves grovelling around for some firm ground.
When someone lies to you it then becomes very hard for you to believe anything they say unless it can be proven. The theory of AGW cannot be proven, if it could we would be told, but the telling of lies can.
97% consensus was a lie.
The Hockey stick graph was a lie.
Polar bears dying was a lie.
Superbug proliferation caused by global warming is a lie.
The oceans are becoming acidic is a lie.
Droughts and the rise of extreme weather conditions is a lie.
The list is long.
We are told that CO2 is bad for the planet, another lie.
As well as lying, perpetrators of the AGW panic story also attempt to close down debate. They name call those who question. They smear those who dare to challenge.
Is this rational behaviour? Is this scientific behaviour? No it is very unscientific behaviour.
The passion and well-meaning of the young has been corrupted. Money is involved, big money. Who will pay? The poor the struggling and the developing will pay.
Facts! What the hell do facts mean any more when one can manipulate truth.
“If you tell a big enough lie and tell it frequently enough, it will be believed.” Adolf Hitler 1889 – 1945
Patrick Moore. PHD. Canadian founder of Greenpeace. Scientist, ecologist, very interesting to hear and v sceptical.
Indeed. There are many in power who would do well to watch this:
https://www.youtube.com/watch?v=UWahKIG4BE4
But there is zero chance.
Harold thank you for describing the theories of Milanković in such clear simple language. History suggests that the hidden hand of Milanković can be seen in each of the preceding warm periods the Earth has enjoyed in the past, the Minoan 3300 years ago, Roman 2100 YA, Medieval 1000 YA because evidence suggests that each was warmer than the one that followed.
Of course it is too early to tell if our current warm period has peaked but it seems most unlikely that we’ll be seeing temperatures that would allow grapes to be grown in Northern Britain the way the Romans did or current inhabitants of Greenland being able to bury their dead without using jack hammers in the metres deep permafrost where the Vikings once buried theirs any time soon.
With regards runaway global warming fears of a ‘climate emergency’ it is helpful to understand that the Earth has a temperature governing mechanism.
Every afternoon, when the surface of the tropical oceans reach roughly 28 deg. C thunderstorms spontaneously begin to form.
These giant heat engines remove heat from the seawater (the latent heat of evaporation) and because humid air is less dense that dry air, loft it heavenwards. When it reaches to the top of the troposphere where it is cold, the water vapour condenses/freezes) releasing its heat.
Much of this heat then finds it’s way into space. (This is the principle on which the heat engine works, I’m sure the detail is more complicated). Clearly the bigger the area where the sea surface is 28 degrees the bigger the area where tropical thunderstorms form.
So, we’re in safe hands. The Pacific Ocean is taking care of us!
This is a good thing, because if this wasn’t the case and we really were facing a ‘climate emergency’ we’d have to begin threatening communist China with all-out nuclear war unless they stopped building coal-fired power stations hand-over-fist immediately!
That’s because right now they are the by far the most responsible, in term of volume and rate of increase, for human-caused atmospheric carbon dioxide.
Secondly, ITS also A GOOD THING BECAUSE the recent increase in carbon dioxide in the atmosphere is greening the planet. (PLANTS LOVE CARBON DIOXIDE, they eat it for breakfast, lunch and dinner!)
So, perhaps we should be thanking China. (As the old saying goes, ah so, clever the Chinese!)
What would seem to be agreed as certain is that the Earth’s climate changes due to effects that have nothing whatsoever to do with the human population. What is less certain is the additional effect of the human population.
If the human population is having an effect to the extent that it makes life on earth unacceptable for humans, then humans should be acting to make life on Earth acceptable. This could be achieved by reducing the affect per human: more humans the greater the reduction per human.
It seems to me extremely unlikely that humanity will ever move to a situation of evening up the effect. Even if all high effect Americans reduced their affect it seems to very unlikely that those currently having low effect and aspiring to a better life would be content to stop at the mean, given all the benefits they are seeing enjoyed by others and, by self sacrifice, to be denied to themselves.
There is an old adage: if you are stuck in a hole then stop digging. World population growth seems to be an issue absent from the climate change debate.
The surface area of the Earth is limited, most of which is uninhabitable, though many die trying to prove the opposite.
What lifestyle do you aspire to?
There is more flooding nowadays because more rivers are overflowing their banks. Why are they overflowing their banks in recent times ? Because the EU’s Water Framework Directive has banned EU member states from dredging their rivers like they used to, they say that dredging threatens endangered wetland wildlife species. So for nearly 20 years rivers in England have not been properly dredged. So more and more rivers are going to break their banks and overflow in England. As has happened in the Somerset Levels and round Carlisle in the Lake District and elsewhere. The UK Rivers Authority has cracked down on dredging. Thanks to that EU Directive the Green Party is in dreamland.
Current AGW theory says that the polar regions will warm faster than the equator. The energy of weather comes from the difference in temperature between polar and tropical air masses. Less difference, fewer storms. Warming is running at half the ‘projected’ rate. Only one of the dozens of models is approximating the real data, INMCM4 (5 is I believe the latest version). which uses a climate sensitivity half the generally accepted figure.
It’s warming. Its not warming at a dangerous rate
My bet (backed up by the lack of the tropical hot-spot) is that water vapour feedback is minor. Why? Dunno,. Maybe more cloud because of extra water cancels out WV warming.
Climate ‘science has made nothing but trivial predictions Until it produces a real, accurate prediction (not projection) it is not worth a bent brass farthing.
JF
I entirely agree with Michae Keal and Kim. Water vapour rising from tropical oceans takes latent heat to the top of the troposphere where part of it radiates to space and part of it rains out from the equator to about 2000 miles north and south of it. From there further cycles carrying the water to the top of troposphere again radiate to space and further carry the heat towards the poles. Without these cycles and latent heat extraction by water it would be +90 degrees at the equator and -90 degrees at the poles. This proves that water vapour is NEGATIVE feedback, not positive as presumed and written in to all the global circulation models.
As Kim has pointed out, the warmers just continue to lie and put forward anecdotal evidence and pseudo science. I do not believe any of the graphs now produced by the scientific agencies because they have all been drawn to the ‘dark side’ and will do anything to perpetuate their program of trying to control the worlds energy. The effects of the drive to carbon zero will have a devastating effect on Western economies and will do absolutely nothing to affect the climate. As Michael stated, if burning coal and emitting CO2 was going to destroy the planet for human habitation we would be at war with China. Because we are not proves it is just a new Western religion.
Not accurate enough
You say the system is in fine balance but offer no information on sensitivity. You suggest positive feedback but such feedback is not observed. You say reduce CO2 emissions but do not say; from the reasons offered; why. You note that there are lots of unknowns and unquantifiables and you are right about that.
Try to get hold of this book. Excellent.
https://en.wikipedia.org/wiki/Rare_Earth_(book)
He was a cleaver chap that Mr Milankovic ! – I remember learning how Sun and Moon drove the tides on Earth, but Saturn and Jupiter having an effect upon Earth’s ‘flight path’ round the Sun, is rather new to me. – Both are huge planets, yet so far away from the Sun and us. ….. As all the planets circle the Sun in an ellipse path, has it been plotted as to distance of these giants, from the Sun and us, year by year ?
I have always held to the view upon Global Warming, and past Ice Ages, that ‘nature’ is well out of the scope of mankind to make much difference, but I have held to a belief that if we, at least, clean up our use of planet Earth, it would not go amiss !
https://en.wikipedia.org/wiki/Milankovitch_cycles#Orbital_eccentricity