Earth only supports human life during a very short window.
The Earth began as a planet with a poisonous atmosphere, bombarded with lethal radiation circling a far colder Sun. If that early Earth had an atmosphere like the one we have today, then it would have been frozen, with temperatures always far below the coldest temperature ever seen on Earth today. Instead, it had a CO2 atmosphere that warmed the Earth, but allowed in so much harmful radiation that life on the surface was not possible.
If humans arrived from space to visit Earth anytime outside the 5% of the time shown in green on the timeline shown here, they would need to wear spacesuits to survive.
Of the 4.5 billion years of the Earth so far, for the first 4.0 billion years, even as oxygen levels rose, there was still too much radiation for life on the surface. Then finally, around 0.4 billions years ago, life could exist on land. But now, there is only another 0.1 billion years before natural climate change turn the Earth into something like Venus, where conditions are too hot for live as we know it.
If there really was a ‘goldilocks zone‘, Earth would be leaving it about now.
Summary: The Sun vs CO2.
The bottom line is, these two main factors that have been determining the climate on all the rocky planets in our solar system, including Earth, ever since the planets were born:
- The Sun: turning up the heat, so far by over 80°C (144°F), from -93oC to -18oC.
- CO2: Our warming blanket to stop us freezing, but on Earth with a thermostat to stop us cooking as the sun gets warmer.
That is the complete overall picture. This page explores how these two factors are dominant in controlling climate, and that all other factors become just fine tuning. Given these two factors can each have such dramatic impact on temperature, the key becomes what has kept these force in balance to give such stable temperatures? Exploring these two dominating effects, their impact and how the balance is maintained, provides a basis for what determining what we know and what we don’t, in terms of future climate.
We now know that the heat arriving on Earth from the Sun has steadily increased since life began by over 80°C (144°F), and the reduction in CO2 over the billions of years has prevented us frying. In fact, we see from Venus and Mars, that changes in CO2 levels can change temperatures by over 100°C (a change of 180° F). No other factor has ever demonstrated this the ability to change average temperatures by even close to 10°C level, or within an order of magnitude of the impact the Sun or CO2 can have in changing temperature.
A problem is, that while further reductions in CO2 level are required going forward, almost all our CO2 has already been consumed. Fortunately the sun increases in temperature on a scale of millions of years, so the fact that the Earth has only around 0.1% of its time being able to support life remaining, still gives us plenty of time. What is scary, is that being so close to the end of the temperature system naturally breaking, suggest that even without human activity, we are now on a very fragile planet.
The Sun: Continually turning up the Heat.
The Life Of A Yellow Dwarf: 45% Hotter Since Life On Earth Began.
The Sun is a star. One of around 250 billion stars in our galaxy. As there are lots of similar stars to observe at all stages of their lifecycle, we have been able to learn about our star, and its lifecycle. The Sun is a g-class main sequence star, or yellow dwarf star, which is sort of surprising considering it is white (not yellow) and larger in size than 75% of all stars, making neither term ‘yellow’ or ‘dwarf’ particularly descriptive. About 10% of the other stars in our galaxy are also yellow dwarfs, which means around 25 billion similar stars. With so many of these stars to study, we have learnt a lot about them, and can be certain that during the “main cycle” as has been the case so far, the star starts dim, progressively gets hotter and hotter and eventually and explode or ‘nova’. In the case of stars the size of our sun, they become red giants once all the hydrogen has become helium.
Temperature at Earth’s Distance from the Sun: Initially -93° C and now -18° C.
As Earth formed in orbit around our young Sun around 4.5 Billion years ago, the Sun was only producing 70% of the energy the Sun does today. Another way of stating that is, that the Sun is now around 45% hotter than it was originally, since 70+ (45% of 70) = 101.5. The process of producing heat an light, changes the Sun, and the slightly changed Sun produces more light, and more heat. For its entire life, the Sun continually accelerates the process of turning matter into energy until it eventually explodes.
You would expect a planet orbiting a star outputting ever increasing hear like our Sun, to in turn get hotter and hotter. Over the around 5 billion years the Earth has been orbiting the Sun , heat output has increased strength by around 45%.
So why have we not burned to a crisp yet as a result of this increased heat?
Yet, the Earth was warm enough for liquid water to exist over 4 billion years ago, even despite there being so much less heat from the Sun. Clearly all else was not the same, or the planet would have been completely frozen.
What gives? Something else must be adding to the heat from the Sun. And there had to be a much larger effect billions of years ago. Answer: CO2
The paradox is this: with the young sun’s output at only 70 percent of its current output, early Earth would be expected to be completely frozen – but early Earth seems to have had liquid water and supported life.
The issue was raised by astronomers Carl Sagan and George Mullen in 1972. Proposed resolutions of this paradox have taken into account greenhouse effects, changes to planetary albedo, astrophysical influences, or combinations of these suggestions. It turned out that the greenhouse gas carbon dioxide contributed most.Wikipedia: Faint young Sun paradox
Far higher CO2 levels, resulting in a much higher greenhouse effect gave somewhat similar temperatures back then, to those we have on Earth today, despite the fainter Sun. As the Sun warmed to today’s levels, CO2 levels fell, compensating for the increase solar heat. While temperature has fluctuated over time, those fluctuations have only within a surprisingly narrow range. These two big drivers of temperature, have largely cancelled each other out. As result, we have what appears to be extremely rare: a planet that has supported life for over 4 billion years.
The initial Earth atmosphere had around 80% CO2, (see graph to the left), which is 800,000 parts per million, instead of the less than 500 parts per million now. However, that is 80% of a smaller total, before the nitrogen added another 3x as much gas to the atmosphere. If the Nitrogen was there at the beginning, it would have only been around 25% CO2 and 75% N2, as there was never even close to as much CO2, as there is nitrogen (N2) today. The total initial CO2 would be equivalent to around 25% of todays atmosphere, and it is the total CO2, not the percentage, that is relevant to the amount of greenhouse effect. As 25% is 250,000 parts per million, there was around 500x more CO2 in the early atmosphere.
So the Earths atmosphere originally contained just a little more CO2 than it now does O2. This also adds up because the O2 we have now was produced by photosynthesis converting the CO2 to O2. It took over a billions years of conversion because before there was free oxygen, because there were rocks which were not initially saturated with oxygen, and they absorbed oxygen production for over 1 billion years. Eventually, rocks became saturated, and there were enough plants to accelerate oxygen production, and create the great oxidation event. The emergence of oxygen resulted in the near extinction of all previous (anaerobic) life . It all adds up, that there would have been at least 1/4 more CO2 originally, than there now is O2, or oxygen.
It turns out, a ‘naked ‘ planet with no atmosphere or other heat source, at our distance from the Sun would now have an average surface temperature of -18°C (just below 0°Farenheit). We know this, apart from it being quoted in documentaries, because the moon is the same distance from the Sun and this is the average temperature on the moon. Temperatures on the Moon indicate temperatures of a ‘rock with no atmosphere’, as the Moon and Earth are, on average, at the same distance from the Sun.
So we have not ‘burnt to crisp’, as even now, heat from the Sun alone is insufficient to keep us warm enough to have our liquid oceans, and we still need some greenhouse effect to keep a little more heat.
How cold would it have been without CO2?
How cold it would have been without CO2 back when life began, and the Sun was only 70 percent of the current level? This can be calculated using Kelvin, the absolute temperature scale where zero (0) means no heat at all. The absolute scale temperature today, at Earth/moon distance from the Sun, is -18°C = 273.15 – 18 = 255.5 K. This means the simple calculation of the initial temperature, without a ‘CO2 blanket’, from the sun at 70% of current levels, would be 255.5K x 70% = 178.85K. Converted to more familiar scales this is -94.65°C or -138.7°F. Too cold for life.
How cold would it have been with today’s 500x less CO2?
Yet on Earth today, we have an average temperature of 14.9°C (58.62° F) , which is almost 33°C (over 58°F) warmer than the moon is now, despite Earth and the Moon being at the same distance from the Sun. This means our current atmosphere does add 33°C (which is also a change in K of 33), so temperatures with out current atmosphere would have been -61.65°C or -78.97°F. Average! Still too cold for life.
Even with the warmer Sun of today, we still need a little CO2. Without an atmosphere or some other heating system, we would, like the Moon, have average temperatures of -18°C, which would result in a mostly frozen Earth.
Life has depended on an ever changing, right amount of CO2.
So, when life began and the Sun was young, because in place of the -93°C surface temperature that would be expected from that faint young Sun, CO2 levels made it warm enough liquid water, and life to begin.
Things on Earth can never be constant, because we orbit a Sun that is not constant. It is the balance of CO2 and the Sun that allows life on Earth.
CO2 Levels: Adding our warming blanket with thermostat.
CO2 as the auxiliary heater for the Earth.
So, it turns out, the Earth has always had a warming blanket. Unlike the moon which has no atmosphere, the Earth has an atmosphere, which wraps around the Earth like a blanket, and can prevent heat escaping, just as a blanket does. This initially kept us warm when temperatures would otherwise have -94.65°C or -138.7, and today keep us warm instead of an average temperature of -18oC like the Moon.
Our temperature is now, on average of 14.9oC, and as a result, we have lots of liquid water. This ‘blanket’ effect of the atmosphere currently provides for that current average 33°C of additional heating.
The heating comes from greenhouse gasses as explained in this video.
For a quick text explanation, just like a blanket, greenhouse gasses have to keep heat from escaping. But unlike our bodies, which produce their own heat, the ground is heated by sunlight. So greenhouse gasses are those that let the sunlight through, but prevent heat (as infra-red radiation) escaping.
As explained in the video, the atmosphere is now almost entirely nitrogen and oxygen, which do not function as greenhouse gasses, leaving the small fraction of CO2 (less than 500 parts per million or 0.05%) to do the greenhouse work. This 33°C of additional heating from such a small fraction of the air, leaves it easy to imagine how past far larger concentrations of CO2, provided the extra warming back when life began, and the Sun was much cooler.
Ok, so CO2 fell as we needed less heat. In fact the CO2 seems to have fallen at just the rate we needed!
This leads to two questions:
- How have CO2 levels managed to fall?
- How has the fall in CO2 levels been so balanced against the Sun’s heat?
Plants eat the Blanket and turn down the heat: How CO2 levels fall.
The sun keep increasing in output, and the Earth’s keeps dropping CO2 levels to adjust.
There is a requirement that there is CO2 in the atmosphere available to be removed. Removal of CO2 means swapping the CO2 in the air for O2, and leaving the C out of the way either in living plants, or on the ground, or under the ground. CO2 is a greenhouse gas, and O2 is not.
The primary reactions is
water + CO2 + sunlight -> Sugar + O2
Sugar is the building block of carbohydrates, including oils, fats and starches. The sugar building block is easily converted to starches and fats, and almost the entire mass of and trees and wood, with other ingredients only present in relatively minute quantities.
So that’s the lesson: that a tree gets its mass from air and water. It “eats” air, chomps down on airborne carbon dioxide, then uses sunshine to pull the carbon dioxide apart, gets rid of the oxygen, which “it spits back into the air,” says Feynman, “leaving the carbon and water, the stuff to make the substance of the tree.”National Public Radio (npr.org) interview
Plants as a Thermostat: Balancing CO2 levels for Temperature Control.
The key to our continued survival, is that plant ensure our CO2 warming blanket applies just the right amount of warming. Too little CO2 warming blanket and the earth freezes, too much and we move to no ice, less land, and eventually to being another Venus. So how is the balance for the thermostat maintained by plants?
It is clear that plants do ‘eat’ CO2, but how have they managed to eat, neither too fast which would freeze the planet, nor too slowly which would see us become another Venus? How do we get ‘Goldilocks’ of ‘just right’?
Yes, there have been ‘wobbles’, but in the long term, the pace of removing CO2 from the blanket has been just what was needed. Magic? In fact here is a graph of CO2 levels vs heat from the Sun. The balance is much too good for coincidence!
Ok, so there is an underlying reason it balances. Here is the process:
- Cyanobacteria evolve on Earth, with that evolution enabled by the presence liquid water (i.e. when temperature is suitable)
- Cyanobacteria thrive, and all consume CO2 through photosynthesis.
- The Sun is getting hotter, but slowly, and it turns out as long as the Earth is warm enough, cyanobacteria can consume CO2 even faster than is needed to maintain a temperature balance
- the hotter the temperature, the more faster the cyanobacteria grown and the faster they consume CO2
- So once the Earth warms, cynaobacteria (and modern plants) consume CO2 quickly and the Earth cools down due to the fall in greenhouse gas, which in turn slows the growth of cyanobacteria
- When growth of cyanobacteria/plants is slow, less CO2 is consumed so the ever warming Sun warms the Earth….. until the heat makes the cyanobacteria/plants grow faster, and consume more CO2 more rapidly cooling it down again….
In fact, the whole system works like human engineered systems for cooling (e.g air conditioning and refrigeration). These systems use a thermostat:
- heat from the outside warms the environment, and when the environment gets warm enough, the motor switches on and starts cooling at a rate faster than the heating from outside
- when the environment gets cool enough the motor switches off again and allows things to warm
In fact, with the many modern cooling systems, rather than an on/off thermostat, there is a smarter control system, and the motor just speeds up and slows down, just like the cyanobacteria/plants slowing when the Earth cools.
So not only have plants reduced the ‘blanket’ warmth, plants have reduced the warmth in a controlled manner.
Clearly, greenhouse gasses, and specifically CO2, can drive drastic changes to climate far beyond that which the Earth has been know to experience, and even beyond the level that life can survive.
On Earth, there was initially as much CO2 in the atmosphere as there is now O2, since all our O2 is a result of photosynthesis:
water + CO2 + sunlight -> Sugar + O2
There is one molecule of O2 produced for molecule of CO2 at the outset. Since O2 reacts with almost everything, it believed at first O2 produced was absorbed by other reactions, so not all the O2 produced is still around. Therefore there must of been even more CO2 originally than there is O2 today.
Other Factors: Methane, Water Vapour, Ozone, Albedo, etc?
How Important are other factors?
Changes in the heat from the Sun or to the ‘warming blanket’ provided by greenhouse gases can make change temperatures by over 100°C (a change of 180° F), a level of magnitude greater than anything else.
Beyond the Sun, and greenhouse gases (CO2 and all other greenhouse gases), no other factor creates changes beyond around 10°C (a change of 18° F). All other factors have relatively minor, and short term, climate effect. Such effects can seeming significant at a time when all else is stable, but these effects from other than the Sun or CO2 are only ripples in the real, long term, climate story.
Methane, Water Vapour and other greenhouse gasses.
A ‘greenhouse’ gas is any gas transparent to visible light, but partially opaque to infra-red light. CO2 is not the only greenhouse gas. It is not even the most effective greenhouse gas, but it is the greenhouse gas with the greatest effect.
CO2 has the most effect because it is stable, so once CO2 is in the air, it stays unless something happens to remove the CO2 . If a source keeps producing CO2, then, year after year, CO2 levels increase. Every year the problem accrues. Year after year.
Other greenhouse gasses do not accrue, but instead, break down, dissipate or condense. Remove the supply and the problem just goes away. If there is a constant source of the gas, the level will stay constant and not become worse over time. This means whatever effect the gas causes, the full effect of the effect is the effect as seen today. The effect will only get worse if the rate of production of the gas increases, and the increased effect will again be immediate, and reversible.
Methane has less overall effect because it is not stable, and thus breaks down. If something is emitting methane, then it is increasing current greenhouse gas levels, but is not increasing the effect as time progresses. For example, wild antelopes produce methane, and have been producing methane for millions of years, but the level of methane from them is the same year after year. Humans breed cattle and sheep. The more cattle and sheep, the more methane, but the level of methane again remains constant for a given number of cattle and sheep. Maintaining the same number of livestock caps any effect at current levels.
With the same number of livestock, if the number of methane levels increase, but the levels do not accrue. So what ever level there is due to emission of methane, it will remain at that level. The effect does not accrue.
Water vapour is an extremely powerful greenhouse gas, but again, it does not accrue. The amount of water vapour in the air is determined be air temperature, and the presence of surface water. The hotter the air gets, the more water vapour in the air, but at the same temperature the water vapour reaches a peak can does not accure.
The real danger with water vapour is that it provides positive feedback. More heat, more water vapour, more water vapour, more heat. This magnifies any other factor decreasing or increasing air temperatures. So if sufficient CO2 is added to raise the temperature 3°C, the availability of water vapour could magnify that effect to 5°C. Further conditions can mean that over a certain temperature, the positive feedback will see temperatures rise until conditions become like those on Venus.
Ozone is different from greenhouse gases which are partially opaque to infra-red, as Ozone is partially opaque to ultra-violet and X-rays and gamma rays. Without Ozone, only the simplest organisms could exist unless living under the ocean. This is why, even after there had been Oxygen in the air, nothing lived on land for over 1 billion years even under the most optimistic theories. In some ways, Ozone is more critical to the ‘climate’ than CO2, but while it is critical we have sufficient, it is not critical we have some exact correct amount, as we don’t need any of the frequencies that are blocked, and it is not under the normal definition of ‘climate’.
The albedo of the Earth is how reflective is the Earth. The more reflective, the lower the temperature. Some gases, such as those produced by volcanos increase the Earths albedo as does surface ice on the earth, but changing the albedo itself does not have a cumulative affect. So volcanic winters only last a few years at most after the volcano, and things change instantly when the amount of ice changes. Ice however, does have a positive feedback effect, similar to with water vapour in the air.
The more ice, the colder it gets, the colder it gets, the more ice there will be. Conversely, as the temperature rises and ice caps melt, the Earth becomes less reflective, which further increase the temperature. This has resulted in the Earth having three stable states in recent times:
- Ice age, glacial period.
- Ice age, interglacial period. (like now)
- Green house periods outside of an ice age.
These alternative stable states remain stable due to the effect of ice on the Earths albedo. However, with too much ice, the ‘blanket eating plants’ will fail to keep up as the Sun warms, limiting the time of a glacial period, and during interglacial periods, plants can ‘eat’ too much CO2 and cool things down again. Cycling between these two states has been continuing for the past 33 million years. While ice-ages (or ice-house periods to differentiate from the shift by Hollywood to rename glacial periods as an ‘ice-age’), have been common since there has been life on land, but were rare special events previously.
Etc: Magnetic Field, Volcanoes, Asteroids.
These are all factors that influence the climate be changing the composition of the planet in ways that change the greenhouse, ultra-violet shielding or albedo affecting materials, so are not really other forms of altering climate, but more other ways of changing the presence of the factors that control climate.
A Tale of Three Planets, One Survivor: The Blanket is Fragile.
Looking Beyond Earth.
Can we observer these same factors elsewhere? It turns out we can. In the only two ‘remotely like Earth’ planets can closely observe, we have seen the exact same forces at work.
As we have learnt that it is not just the Sun that control heat on a planet, but also the contribution of the ‘blanket’. Through multiple probes sent to both Venus and Mars, we have learnt that there is compelling evidence that both Venus and Mars both had liquid water on their surface at one time, despite Venus now being too hot and Mars now too cold.
Venus From ‘Just Right’ (around 25°C) to over 500°C
When the first spacecraft was sent to Venus, it was prepared for a splash landing, because give the distance from the sun, liquid water seemed likely. In turns out Venus has huge atmospheric pressure, and is the hottest planet in the solar system, even hotter than closer-to-the-sun Mercury. Venus is the same size as the Earth, around the same composition, and back when life started on Earth with the sun only 70% of current strength, Venus at a distance 70% of distance the Earth is from the sun, is thought to have had similar temperatures to Earth today. In fact it seems likely that Venus at an early time, could have been even more suitable for life than Earth. Professor Brian Cox states in the planets documentary, that the temperatures on Venus were once like a spring day on Earth. It is believed Venus had rivers and oceans of water and should have been suitable for life.
Venus went from temperatures like a spring day on Earth, to temperatures now that can exceed 467°C ( 872°F) . Perhaps even 100°c of this change could be explained by the increased heat from the Sun, but this is a change of over 400°C . What about the other 300°c of increase? It seems most of that 430°C increase came not from the Sun, but from the ‘blanket’. Venus now has an incredibly thick atmosphere will a huge greenhouse effect that makes the planet hotter than the planet Mercury, despite the fact that Mercury far closer to the Sun, and thus would receive over 3 times more heat from the Sun.
If there were plants on Venus, then they were not able to keep up and ‘thin the blanket’ as heat from the Sun increased.
Between 4 billion years ago and now, green house gasses blanket added to heat increase. It is possible that for a time there was a ‘working thermostat’ that depleted CO2 as the heat from the Sun increased, as there is evidence Venus stayed hospitable for as much as 3 billion years. However, if there was a thermostat, it failed to keep pace, and at least 1 billion years ago the system went into reverse.
A recent NASA climate model suggested Venus could have been habitable in its early history and even had oceans of liquid water, though there’s no sign of those oceans today. “The loss of oceans may be recent geologically — perhaps only in the last billion years,” said David Grinspoon, an astrobiologist at the Planetary Science Institute, in an email. “This means that our solar system *might* have had two planets with surface oceans and life, sitting right next door to each other, for most of solar system history.”Gizmodo, on new probes being sent to Venus.
Once temperatures rises over around 50°C, an increasing percentage of water becomes water vapour, which is another green house gas, significantly increasing the ‘blanket’ and would completely destroy any ‘thermostat’ if one is present. The more greenhouse gas, the more the temperature rises, and the more the temperature rises the more water becomes gas……the ‘thermal runaway’ is a positive feedback loop that drives a rapid increase in temperatures to extreme levels.
In the end, once considering a case such as Venus, it becomes evident that once thermal runaway or ‘runaway greenhouse’ point is reached, more temperature increase can come from the greenhouse gasses, than from the increase in heat from the Sun.
On Venus, once temperature regulation failed thermal runaway, temperatures soared, resulting in an unliveable furnace with the highest temperatures in the Solar System, even beyond those found one Mercury, despite Mercury being approximately twice as close to the Sun.
We have another 25 million years if we do nothing to accelerate the process, which is at our rate of progress gives us a lot of time to find a solution, but in geological terms that is a very short time. Humans only just managed to evolve in time!
Mars From ‘Just Right’ (around 25°C) to to -63°C at the equator!
The CO2 blanker of Mars was destroyed by the ‘solar wind’. On planets like Venus, Earth and Mars, without a magnetosphere, the atmosphere providing the ‘blanket’ is protected by the planets magnetic shield.
At the outset, the core of the planet Mars was still a molten iron core like that of Earth. But that core cooled, the magnetosphere collapsed, allowing the solar wind to star blowing away the atmosphere. At the same time the Sun was becoming hotter, the CO2 was being blown away cooling the planet faster than the Sun was warming the planet. Being further from the Sun that Earth, Mars needed that blanket! In the end, the impact of losing the CO2 was even greater than that of the Sun becoming hotter, and Mars became cooler. In fact, cold. Just as adding more greenhouse gasses for Venus added even more heat than that of the increased solar energy.
During this same 4 billion year period of relatively stable temperatures on Earth were stable, surface temperatures on Mars have ranged from, once also supporting liquid water on the surface of Mars, to a current average of -63°C at the equator. Even though the Sun has warmed, Mars is now around 90°C colder, despite the warming Sun. This is due to Mars losing most of its CO2 from the atmosphere. Without the loss of CO2, Mars would have also gained heat, making the loss of temperature due to losing CO2 well over 100°C.
Earth the Survivor: A ‘Magic’ Thermostat for Stable ‘Just Right’ Temperature.
Despite a the increase in heat from the Sun being sufficient to produce a change in temperature of 93°C, average temperatures have remained well with 20°C.
Yet for both Mars and Venus, there have been temperature changes, with a greater contribution to the change arising from a change in greenhouse gasses the the 93°C change would could have expect on Earth due to the Sun. driven more in both cases mostly driving by the ‘blanket’ and not the Sun.
Look at temperatures on Earth and realise what we have is remarkably stable climate over billions of years. Then look at either of our nearest neighbours, Mars and Venus, and realise that is changes of climate.
The ‘warming blanket’ that regulates temperature, as we have on Earth is extremely precious, and without this life continuing for the billions of years it takes to evolve humans would not be possible.
The ‘Goldilocks Zone’: A dangerous fairy tale.
The zone is always on the move.
You may have heard of the ‘goldilocks zone’. The distance from a star that is ‘not too hot’ and ‘not too cold’ for liquid water, and thus life, to exist on a planet. Giant stars have very short life spans and build rapidly to a supernova, leaving only main sequence stars likely to have planets that can host life. Now consider, all main sequence stars, also build up more and more heat throughout their lifetime. This means, as per the diagrams here, any goldilocks zone move outward during the life of the star, from close to the star when the star is younger, to further out as the star ages.
Fairy tale? Why dangerous?
The ‘fairy tale’ is the idea that a planet at a fixed distance from any star could continue to be neither too hot, nor too cold for any length of time, without some mechanism to compensate for the changing heat from the star. The danger of the fairy tale is that it creates the impression that stars are static, and ‘goldilocks zone’ is a fixed distance from any given star rather, and distance from the star is the dominant factor in determining the temperature on a planet. The danger is that the very concept, is misleading.
The varied range of the ‘Goldilocks’ Or Habitable Zone: Allowance of Atmosphere.
Life as we know it requires liquid water. So it is expected that life in universe is most likely to must exist in areas where water can be liquid. The name ‘Goldilocks Zone’ comes from the ‘not too hot‘, as water becomes a gas if too hot, and ‘not too cold‘, as water becomes solid ice if too cold. The less frivolous name is the ‘habitable zone’.
It is not heat from a planets star alone that determines the temperature on a planet. Planets orbiting a star will typically have the star as their primary source of heat, but that head can be supplemented by secondary factors such as the planets atmosphere, amplifying or partially blocking the heat from the star.
This makes the Goldilocks zone not just the very narrow band where the exact right amount of heat from the star is present, but instead a wider band that begins at first the point where there is not too much heat from the star to be too hot even with some heat blocked, and ends at the point where no matter how effective the atmosphere at retaining heat, it seems impossible to have sufficient heat to prevent all water freezing.
Goldilocks Lessons From Our Solar System: We are now living on the edge.
The first diagrams I saw of the Goldilocks zone in our solar system stated Venus was too close to the Sun and that is why it is too hot, and Mars was too far from the Sun and that is why it was too cold. Those early diagrams place the Earth at the centre of the Goldilocks zone.
Since then, we have learnt that Venus, Earth and Mars all at one time had liquid water, so therefore all were in the Goldilocks zone. Since the Goldilocks zone moves outwards away from the Sun, it is possible that Venus is no longer in the zone even if it was in the past, but since Mars was had liquid water billions of years ago and the band moves outwards, Mars can only more in the zone than ever now, despite now being too cold.
One lesson is that Earth is now right on the edge of the Goldilocks zone, and within the next few million years as the Sun becomes a slightly hotter star, Earth will exit the Goldilocks zone.
Another lesson, this time from the example of Mars, is that a planet being within the Goldilocks zone, is not guarantee it will be neither too hot nor too cold. Mars lost its auxiliary heat from its greenhouse gas based atmosphere, and became colder even though the Sun became hotter.
Blanket Limitations and Fragility.
Balance Wobbles: The remaining small climate change
Temperature control systmes do survive disturbances. With a refrigerator, people disturb the balance by opening the door. The self regulating system means close the door, and the balance restores. Open the door too often and some food may spoil.
On Earth, the system gets disturbed by meteorite impacts, volcanos, fluctuations on the Suns path of continued rise in heat output, and other factors. Normally these happen, and the self regulating system means the balance quickly restores.
When the Yucatán meteorite hit around 66 million years ago, the Decan traps were already erupting, which is like the refrigerator door had already been left open, and the meteorite was then then putting something really hot in when the door has been left open. The non-avian dinosaurs got spoiled. But the system still restored.
In fact CO2 consumption gets ahead of itself sometimes, and we have even had ‘snowball Earth’ episodes, where we have to wait for the Sun to catch up on the heat increases.
Solar minimums and maxima, sunspots, volcanos, meteorites: all can cause disruptions to the long term pattern. But in every case there has been disruption, the mechanism of ‘drop CO2 levels to cool down when it gets warm’, and ‘pause or raise CO2 levels to warm up when it gets cool’, has seen the pattern return to trend. At least every time so far.
However it takes time to return to balance. The fact that it takes time demonstrates that our the feedback system of our ‘warming blanket’ can be overridden. The system is not all powerful, and if any of these past events had been continued long enough or been sufficient severe, temperatures could have drifted outside the working range of the system.
A ‘blanket’ temperature balance system with less than 0.6% remaining?
An quick check of the solar energy vs CO2 levels graph reveals the ‘blanket’ is almost exhausted of CO2. The graph for CO2 has almost reached the zero point. In fact, given levels have been as much as over 500 times higher in the past, the Earth has ‘stashed’ almost all C from the CO2 there ever was. There is almost none left. Further, plants as they are now, need at least 180 parts per million of CO2 in order to survive, and we are already close to that limit with life on Earth could get getting closer to the end of the line than many people realise. Unless plants suddenly evolve further than they have in the past 4 billion years, we are down to as little as 25 million years of CO2 reduction left available to us.
In Earth terms, 25million years is nothing, but for us humans, 25 million years not only seems like forever. Hopefully it swill be sufficient time to solve the problem.
For us, 25 million years feels like so long it is not fragile. But consider 25 million years relative to 4 billion years the system has been working, and over 99% of the system life has been passed.
With CO2 down to less than the last 1/500th of the original level for ‘the blanket’, keeping the temperature sufficiently low is now more delicate and fragile than it has even been in the Earth’s history.
When the meteor hit that ‘ended the dinosaurs’, CO2 levels were, 3 times the level of today, and they needed to be to keep the Earth sufficiently warm with the slightly cooler sun. So anything that released buried CO2 at that time as a result of the impact, or disrupted the greenhouse gasses, was making a difference to a far larger base of CO2. At todays levels reduced CO2 levels, something that disrupts by either increasing or decreasing our CO2 levels would be even more catastrophic. Disturbing the greater amount ever of ‘buried CO2‘ would also have a relatively bigger affect than ever.
Our biggest risk is not the 25 million years to run out of CO2, it is that the now very fragile blanket that has already had over 499 parts of 500 buried, can be very hard to keep as ‘thin’ as now required. Our blanket is down to less than 0.6% of its working life.
Anthropogenic Climate Change?
The suggestion is that humans are changing the Earths climate. Humans cannot really change the Sun. So for significant climate change, the path to change is the ‘blanket’ (which can be demonstrated to have a potential for even more impact than the Sun anyway) or find an entirely new way to impact climate. However the ‘blanket’ acts as thermostat, correcting things to keep temperature within a ‘target’ range. Is the system sufficiently fragile that our interference stops it working?
Humans are clearly creating CO2. We even measure the CO2 from car exhausts, There is no doubt that when be burn things we produce CO2, and there is no doubt we burn things, including ‘fossil fuels’. So there is no doubt we are making changes to ‘the blanket’. This leaves only one real question about human induced climate change, “can the planets eat faster and compensate for our interference’? To put it another way, can we mere humans actually change the environment?
It is generally agreed that humans were altering the fragile Ozone layer with CFCs, and humans took action, stopped using CFCs, and the ozone layer has been largely restored as a result. So yes, it is proven humans can change the environment. However, with CFCs there is no ‘Goldilocks’. Nothing to keep within range and not too hot, not too cold level like there is with climate. There is also no system regulating the level of CFCs to keep levels within a target range, as is the case with plants regulating CO2 and temperature. Thus CFC levels, with no regulation system to protect levels from going to high, are clearly ‘fragile’, or easily disturbed. How fragile are CO2 levels, given in this case, there is a regulation system courtesy of plants?
However, the recent history of CO2 presents quite compelling evidence that the regulation system has failed to cope since the 1950s, or perhaps going back just a little further.
The pattern prior to almost the 1950s matches exactly with what you would expect from a thermostat. Everything oscillates within a target range. Like a refrigerator that warms up enough for the motor to activate, and the motor continues until things cool to the lower limit target temperature, and the motor shuts off and the cycle repeats. The data available suggests temperature tracks CO2 levels as would be expected.
So what changed since the 1950s? In the period of the uncontrolled rise in CO2 levels:
- The human population had doubled.
- The human populations on mass started driving cars and and flying in planes.
- Fuels began to be used for cooling in addition to heating.
- There has been a huge deforestation globally.
It is logical these factors explain the huge rise in CO2 levels, and no natural phenomenon has been discovered which could provide an alternative explanation.
Clearly, the system of natural sequestration of CO2 in response to rising CO2 and/or temperature levels is too fragile to be able to maintain control under current conditions.
This expected pattern holds, with perhaps only the ‘down’ slope starting to lengthen, up until around 1950, or in fact just a little earlier. Each cycle, the CO2 level rising, perhaps with a little extra temperature as well, starts the ‘motor’ the plants growing faster and thus cooling things down until with less CO2 to consume and less heat, the cycle starts again. Up until just before 1950.
Since 1950, all indicators are that this time, the plants have been unable to respond sufficiently to stop CO2 rising for the first time in almost one million years. There can be no doubt CO2 levels have suddenly risen, and not doubt that rising CO2 levels will increase temperature. Something has proven the system fragile and all evidence points to human activity being the culprit.
Now it is unquestionable that humans are increasing CO2 levels, yet warnings of this from the same scientists that warned about CFCs, is this time seen as far more controversial. The evidence that CO2 levels impact climate is beyond dispute, yet unlike with CFCs, the suggestion we need to take action is extremely contentious.
Simply put, the entire history of climate on Earth, centres on three lessons:
- the Sun has always, and will continue, to get hotter and hotter
- higher CO2 levels from the past created a more effective ‘blanket’ and result in higher temperatures for any given temperature output from the Sun.
- photosynthesis has seen a continual reduction of CO2 over almost the entire life of the Earth, ensuring stable climate
Clearly, human activity generates CO2, reversing the control effects of plants and thus there is anthropogenic climate change. Further, deforestation reduces the total CO2 extracted from the air by photosynthesis.
Doubts and Counter Arguments: Is The Blanket suffering?
The doubts that are raised.
The doubts raised are:
- Is it actually getting hotter?
- If it is getting hotter, can we be assured this is due to us humans?
- Is it really that bad that it is getting hotter?
- It is after all, someone else’s problem
What the topics discussed here answer is topics 1 and 2. Topic 3, what is the full impact of the climate change, and topic 4, who and should address the problem are covered elsewhere.
What is covered in this are the point 1, is it getting hotter, and 2, CO2 levels are to blame. This does not prove it is humans changing CO2 levels.
Is it getting hotter?
Every time there is a warm day, climate advocates will claim “see climate change!”. Every cold snap, others will claim: “and they say there is global warming!”
Temperature measurements can be debated, fluctuate, and can be impacted by urban activity and other factors, creating ambiguities that can lead to more and more debate.
What the information on this page does confirm, is that CO2 level have risen sufficiently to add at least an extra 1/3 to the CO2 in ‘the blanket’, from 300 parts per million, to 400 parts per million. A blanket that clearly gives us 33°C additional warmth has that much additional strength now. What seems incredible is the idea that this will only produce 2 c of warming. And there is substantial suggestion that forecast may prove conservative.
So why the fluctuations in the above graph before the recent jump?
Note the correlation of the green graph (CO2) with right half (matching time period) of the Nasa data. Then note how the blue temperature graph tracks so well with the green CO2 graph. Certainly consistent with temperature slowly falling, causing a slowing of CO2 consumption, which then allows a rise in both CO2 and temperature. Clearly there are fluctuations, and high CO2 and temperature tends to start a cycle of reduction prior to 300 parts per million of CO2. At this happened previously every time during the previous 800,000 years. Just not this time.
What is certainly settled is that the CO2 level to drive increased heat has happened. So even if it has not become hotter already, it will unless something changes unbelievably quickly.
Can we be sure this is due to humans?
Not, 100% certain, all temperature rise is due to human, no. What is proven, is that CO2 levels have changed the Earths’ climate very significantly. It is also proven that CO2 levels have been rising at the same time humans are producing emissions. The only explanation we have is that this is humans. We know we are cutting down forests, and we know are putting CO2 into the air. We cannot measure exact amount of CO2 being added, only how fast CO2 is rising. With no other explanation, it just makes sense that CO2 added to air is from us. Since we are adding CO2, at the very least, some of it is us.
There are arguments that the rise in CO2 does not exactly track with the production of CO2 by mankind. There are also arguments that temperature rise is delayed compared with human CO2 production. However, none of these arguments provide alternative explanations, and ‘lags’ or delays between cause and effect in nature are actually more common that an instant response. In short. We have an answer. It all adds up, and we have not alternative explanation to consider.
Living on Earth, we can take, what is turns out is an amazingly stable climate, for granted. Studying the only other planets we can see in detail reveals how unusual it is to have stable climate, with an 80°C (144°F) change in temperature to be expected, given the changes within the Sun. The risk is that human induced climate has the potential to damage the mechanism of stable climate extremely quickly. Even without human induced climate change, the stable climate will reach its end far sooner than most of us realise, highlighting the fragility of stable climate. The natural state of any planet is natural climate change beyond a level life can tolerate, and there is a limit to how long life can delay the inevitable.
There is no doubt we are adding CO2 to this ‘blanket’ and thus temperatures will rise.
There is no doubt that increased CO2 increased the efficiency of the warming ‘blanket’ that the atmosphere provides.
How far will temperatures rise? What will the effect of the increased temperatures be on climate. What will be the cost? Those questions are not answered by this post alone. This post just gives further perspectives to the basics, the questions as to home much damage the ‘stable climate’ system can sustain requires further exploration.
- 2020 May 12: Updated introduction.