[Petrochemicals (OP)]

Now let's say global warming is because man is burning fossil fuels AND WHEN fossil fuels run out this increaced warming will also fall. If the earth should enter a cooling period this could be disastrous for crops. Global warming has not conclusively been proved to be co2. It has not been proved either that it is man made.

Anyway how long do we have to guard against failed harvests seen in the 1815 global cooling.

* On the whole we have about 65 years (66 actual, but for maths sake) worth of coal at current usage levels. Coal is the majority of fossil fuels left.

*Population and living standards are on the rise across the world, so the coal reserve is likely to last fewer years.

* Energy usage is doubling every 30 years, its pretty linear for nearly 80 years.

Estimating a 2% linear reduction in fossil fuel use per year we would need 50 years at half production, or 25 years at current usage levels. This would lea e us a nice buffer of 40 years to get ourselves organised.

But as usage doubles every 30 years, accounting for population and living standards this means in the year 2050 we will only have 5 years of reserves left. The maths being an average of  1.5  times current usage over the 30 years which is 45 years of current usage. This leaves 20 years at current levels or 10 years at 2050 levels. This is no where near enough, especially considering a slowdown would have to start from a higher echelon, or 1% reduction in 2050 levels to guard against crop failures.

[Kryptid]

If we stopped putting excess carbon dioxide into the atmosphere, why would we expect the Earth to cool below pre-industrial revolution levels? I see no particular reason that would be a threat to crops, given that we were doing agriculture for thousands of years before we started burning coal and petroleum.

[alancalverd]

Anthropogenic carbon dioxide is an irrelevance, but the global energy demand is significant for humans. 

We cannot sustain our current, inadequate agricultural output without artificial fertiliser. At a rough estimate, one third of your body weight is attributable to the Haber-Bosch process. Without fossil fuel we will have to resort to horse-drawn agriculture, which generally occupies about 50% of the population and cannot sustain present population levels in the "developed" (non-agrarian) world.

Meanwhile as we drift towards mass starvation, the rest of humanity sees the western standard of living as desirable and attainable. But it demands at least 5 kW of artificial power per capita, 3 times the current  world average.

If we act now to reduce the human population to a sustainable level, or great-grandchildren will live in plenty and thank us for our foresight. If we don't, they will live like starving rats.

[Bored chemist]

Anthropogenic carbon dioxide is an irrelevance

Practically all scientists disagree with that view.

Without fossil fuel we will have to resort to horse-drawn agriculture,

Or resort to other energy sources.

[Bored chemist]

At a rough estimate, one third of your body weight is attributable to the Haber-Bosch process.

At a rough estimate two thirds  of your body weight is water.
So Alan, do you think you are actually a solution of ammonia, or was your figure nonsense.

In any event the solution to the massive energetic cost of the H-B process is to grow more beans and less grain.

[evan_au]

Global warming has not conclusively been proved to be co2.

Of course. I hope no-one on this forum thinks that it is.
1. One is a rise in worldwide average temperature over a period of decades
2. The other is a molecule

They are definitely not the same.

It has not been proved either that it is man made.

Just in case a Petrochemicals supporter has trouble telling the difference, a majority of climate scientists and weather modelers are convinced that without the rapid rise in coal and Petrochemical usage since the start of the industrial revolution (and the resulting increase on CO₂ emissions), the observed global warming would not have occurred.

This is easy to test. Computer models of the weather/climate include the chemical composition of the atmosphere as an input.
-Take us back to a pre-Industrial atmospheric composition, and the observed global warming goes away.

As BC says, we need to move away from Petrochemicals to cleaner forms of energy.
- I am not just considering CO₂ as a pollutant, here...
- We have already cleaned up a lot of lethal smog from burning coal in cities (despite efforts by D.Trump to relax legislative protections in the USA)
- When I was a child, we had a kerosene heater in our home; sometimes (when it was badly adjusted) I would see a visible stream of soot. We now know this soot lodges deep in your lungs and gets into your bloodstream - it is not good for you! Efforts are now underway to introduce cleaner methods of cooking and lighting into the "two-thirds world", to reduce the burden of disease.
- Similar problems are observed with soot from diesel engines
- Emissions of mercury, lead, oxides of nitrogen and radioactive nuclei from fossil fueled power stations also impose a health burden on society

That's not to say that "green" power sources are perfect - toxic chemicals are used in their manufacture, and there are doubts about enforcement of environmental legislation in some of the countries where they are manufactured.

[Bored chemist]

Now let's say global warming is because man is burning fossil fuels AND WHEN fossil fuels run out this increaced warming will also fall.

That muddles two issues and, if Petrochemicals is typical of those spreading the message then it's a deliberate act.

Burning fossil fuel creates heat and that warms up the planet- to a tiny extent.
It also creates CO2 which warms the planet to a greater extent.

When we stop burning fossil fuel, the tiny effect will stop, but the much bigger effect will continue for a long time- indeed, if we have screwed things up badly enough, it will carry on forever.

. Global warming has not conclusively been proved to be co2. It has not been proved either that it is man made.

We know that CO2 causes warming. It's simple physics.
We know that it is man made because of two facts/.
The first is that we can effectively "carbon date" the atmospheric CO2 and show that the carbon added is "ancient".
The second is simpler; we know how much more CO2 there is in the air because we can measure it, and we know how much fossil fuel we have burned because we paid for it.

The two figures agree.

So, in reality, there is no question about mankind's responsibility for at least the great bulk of the extra CO2.

Saying otherwise is just repeating the lies of the fossil fuel industry.

Energy usage is doubling every 30 years, its pretty linear for nearly 80 years.

Which?
Is it linear, or has it been doubling every 30 years which would be exponential?


As far as I can tell, we can not sensibly hope to achieve sustainability through
(1) population control,
(2) reduction of per capita energy use, or
(3) a move to renewable sources.

But what we can hope to do is use a combination of those three.

So the second thing humanity needs to do is to stop saying that only one those factors will work.

The first thing humanity needs to do is stop pretending that there isn't a problem.

[Petrochemicals (OP)]

If we stopped putting excess carbon dioxide into the atmosphere, why would we expect the Earth to cool below pre-industrial revolution levels? I see no particular reason that would be a threat to crops, given that we were doing agriculture for thousands of years before we started burning coal and petroleum.

Please read the first paragraph. At a guess as to alternate water vapour is produced from initial combustion and cooling, evaporation etc. It is a far more abundant and therefore Influencial gas.

[Bored chemist]

Please read the first paragraph.

We did, and we even quoted bits of it.

It is a far more abundant and therefore Influencial gas.

Until it rains.

The first thing humanity needs to do is stop pretending that there isn't a problem.

[Kryptid]

Please read the first paragraph.

What makes you think I didn't?

At a guess as to alternate water vapour is produced from initial combustion and cooling, evaporation etc. It is a far more abundant and therefore Influencial gas.

Even if that was true, how does that disqualify what I've said? A return to a pre-industrial revolution atmosphere (whether speaking of carbon dioxide or water vapor) would still not cause crops to suddenly fail due to global cooling. Again, we have been growing crops for thousands of years.

[Petrochemicals (OP)]

Please read the first paragraph.

What makes you think I didn't?

At a guess as to alternate water vapour is produced from initial combustion and cooling, evaporation etc. It is a far more abundant and therefore Influencial gas.

Even if that was true, how does that disqualify what I've said? A return to a pre-industrial revolution atmosphere (whether speaking of carbon dioxide or water vapor) would still not cause crops to suddenly fail due to global cooling. Again, we have been growing crops for thousands of years.

As I said in the first paragraph, warming caused by fossil fuel combustion, co2 has not neceserrily been proven to be the cause.

A cooling event caused by the cessation of burning fossil fuels.

[Bored chemist]

As I said in the first paragraph

Yes, you said that.
We both pointed out that it is not true.
Saying it again does not make it any less wrong.

[Bored chemist]

A cooling event caused by the cessation of burning fossil fuels.

That isn't a sentence.
What did you hope it meant?

[Kryptid]

As I said in the first paragraph, warming caused by fossil fuel combustion, co2 has not neceserrily been proven to be the cause.

Of course not, because science isn't about proof. It's about evidence.

A cooling event caused by the cessation of burning fossil fuels.

And, once again, why would that cause the planet to cool below pre-industrial revolution levels?

[Petrochemicals (OP)]

As I said in the first paragraph, warming caused by fossil fuel combustion, co2 has not neceserrily been proven to be the cause.

Of course not, because science isn't about proof. It's about evidence.

Is this a send up? For example in court the burden of proof is proven by the use of evidence, incontrovertible evidence. That would be fact versus theory. You must be pulling my leg.

A cooling event caused by the cessation of burning fossil fuels.

And, once again, why would that cause the planet to cool below pre-industrial revolution levels?

Because we would not be burning the extra fuel anymore. This must be a send up.

[Bored chemist]

Because we would not be burning the extra fuel anymore. This must be a send up.

Which part of this do you not understand?

Burning fossil fuel creates heat and that warms up the planet- to a tiny extent.
It also creates CO2 which warms the planet to a greater extent.

[Kryptid]

What is a "send up"?

Science is not a court of law and should not be treated as such.

Also, the elimination of greenhouse gas production by humans could eventually result in temperatures lowering back to pre-industrial levels. What I want you to do is demonstrate a good reason why it should keep cooling beyond that to the point where it threatens crops.

[Bored chemist]

What is a "send up"?

A "send up" is a parody.

[Petrochemicals (OP)]

What is a "send up"?

Science is not a court of law and should not be treated as such.

Also, the elimination of greenhouse gas production by humans could eventually result in temperatures lowering back to pre-industrial levels. What I want you to do is demonstrate a good reason why it should keep cooling beyond that to the point where it threatens crops.

A wind up, pulling ones leg, having one on, to dupe someone into C
contemplating a  concept that is foreknown  to be false  . A good example of a send up is.

"Yes yes science is no place for logic proof and evidence. ”

That would be a send up as I would know before hand  that the consideration was a false errand.

Plus that's nice what you say about greenhouse gases.

[alancalverd]

The end of fossil fuels will certainly reduce crop yields and radically alter the whole business of farming and food distribution.

The "Haber Bosch" reference is an estimate by others who know far more than me about these things, of the importance of artificial fertilisers in human nutrition. The summary is that, globally, they increase food production by 33% over what can be achieved without them. Problem is that they are made, transported and to a large extent applied, by the use of fossil fuels. 

The effect of increased atmospheric carbon dioxide has also been to increase crop yields where all else is constant. A  number of commerical greenhouses maintain levels of CO2 that would be toxic to mammals.

Climate change aside, the world is going to be a very unpleasant place in 100 years if we do not reduce the human population to a level that can be sustained without fossil fuels.