[MarkPawelek (OP)]

Optimum = the most favourable situation or level for growth, reproduction, or success.
"the plant grows within a range of 68 and 78°F, the optimum being 74°"

Note: 74°F = 23.3C
Note 2: Mean surface temperature of Earth is about 15°C.

• These scientists found the optimal temperature for photosynthesis was above 20C.
  
• "Mean surface temperature about 5°C higher than on Earth"
  Scientists declare the optimal temperature for life is a planet with an average surface temperature of 20C.
• The UK government recommended home temperature = 21°C
• Cold kills 7 times more people in Pune city, India than heat does. Despite Pune being a risk area for 'heat waves'
• Cold kills far more people than heat does, in England and Wales, Recent ONS Report Finds.
  In summary, the less harsh winters in England and Wales saved about half a million lives over the 20-year period.
• A 2015 multi-country study of temperature-related mortality found that cold kills 17 times more people than heat. Even in tropical countries where there are no severe cold spells: cold still kills more people
  
• I was going to add links to the "The Holocene Climate Optimum" (HCO) and "Early Eocene Climatic Optimum" (EECO). Guess why climatologists call these periods climate optimums?  I'll let the reader find those links.

I conclude that the optimal temperature of earth is at least 20C, a good 5C above our current average surface temperature. Anyone up for a geoengineering project to raise the average surface temperature by the necessary 5C to improve life on earth?

Related post: "Re: Why is Global Warming a threat?"

[alancalverd]

And as temperatures rise, so the activity of coldblooded creatures increases. And all those little critters chomp up vegetation (or other critters) and release carbon dioxide, as you can see from the ripples on the Keeling curve.
'Twas ever thus.

[Origin]

I conclude that the optimal temperature of earth is at least 20C, a good 5C above our current average surface temperature. Anyone up for a geoengineering project to raise the average surface temperature by the necessary 5C to improve life on earth?

I was waiting for this to be a new trend with global warming deniers.  They will no longer say global warming is a hoax, since the temperatures are obviously increasing, instead they will say global warming is good.
I wonder if they will also start saying that ingesting micro plastics is a health benefit.

[alancalverd]

Not a good idea to tar thinkers as "deniers". Far from it. Some of us are sufficiently aware of scientific matters to realise that climate change is inevitable. The important question is how to mitigate its adverse effects on our descendants.

[evan_au]

Mean surface temperature of Earth is about 15°C

Mean black-body surface temperature of Earth is about -15°C, which is obviously a bit cold for water-based life.
- That's why we need an atmosphere and greenhouse gases.

(What's) the optimal temperature for life?

ok, let's define the scope a bit, here...
- We are talking about the surface of the Earth, not some exoplanet, or the interior of some exomoon
- We are ignoring extremophiles which grow best at temperatures over 80C,
- We are ignoring polar marine ecosystems which grow well at temperatures below 10C

What we are saying is that:
-  in a frozen arctic tundra, more plant life will grow if the temperature rises.
- in a sterile desert, more life will grow if the temperature falls.
- If your goal is to grow more life, you need to heat the polar regions (greenhouse gas emissions are succeeding very well here), but also to cool the deserts (for which greenhouse gases are going in the wrong direction).
- So saying "greenhouse gases are globally good" is a nonsense statement, because they have global impact, when what you would prefer is local solutions.
- This statement seems to be saying "Who cares about biodiversity in the Amazon or Congo, because biodiversity will increase in Siberia!"

In fact, life grows best in the temperature range to which it is adapted, and if the average temperature increases, plants and animals will migrate towards the poles and/or up mountains (mountains are a dead end, and fragmented ecosystems are also a dead end; that just leaves adaptation or extinction)

So it seems that the greening of the tundra is more important to you than survival of rainforests - and this post doesn't seem to recognize the damage that is caused by air pollution (in addition to the actual Carbon Dioxide).

[SeanB]

Problem with that is assuming the temperature is even, but you instead have a hot band around the equator, and a cold band around the poles. In the middle you have a termperate zone, and as temperatures increase this tends to migrate towards the poles, and retreat from the equatorial regions. Unfortunately most of the land mass is concentrated either at the equator, or in the current temperate zones, so this results in less land being available, plus a warming ocean disrupts the existing currents, that otherwise distribute heat around, so that the massive temperate land that is most of Eurasia would become either colder, or have worse weather.

The existing tropics would also tend to die out, which will cause massive disruption, as they are a major source of both oxygen, and also a large part of the biomass of the planet. Deserts both on land, and in the oceans, as the hot water there is less amicable for life, and thus will isolate the planet into 2 halves, with it being difficult to survive the crossing as a species, and also leading to the tropics becoming a massive desert region, devoid of most life.

[alancalverd]

In the short term, life will almost certainly get unpleasant: killing things is a lot easier than repopulating arid land, and humans are too stupid to limit their numbers to what can be sustained on the land they occupy.

But the long term could be interesting. https://www.theguardian.com/culture/2021/jan/28/east-anglian-beetles-shed-light-on-uk-climate-4000-years-ago suggests that this dry, chilly bit of England was a warm mediterranean forest in the Bronze Age*, and there is evidence that the Sahara was once forested and therefore reasonably wet. So a simple guess would be that the equatorial rain forests will expand or move north and south and the temperate zones will indeed become more temperate.

When the Arctic ice sheet melts, the water will have to go somewhere. The edges will certainly decrease (due to local cooling below 4C) then increase sea levels, but the puddles in the middle will turn into clouds so the northeast wind will become wet rather than dry and the steppes of central Asia will bloom .

Pity that there won't be any civilised humans to see it.

*There's plenty of other evidence, like hippo bones from an earlier era. And presumably the woolly mammoths ate something like grass or shrubs before getting covered in Siberian ice....

[Bored chemist]

This is all very interesting, but it's not actually hot weather or cold weather that kills people.
People die due to changes in weather- particularly fast changes. People died form cold in Pune, but in ambient temperatures that people survive with no difficulty in Glasgow.

People die from cold in the UK, but typically due to changes in other circumstances- like poverty.

There are two major drivers of the changes in temperature.
The seasons.
The weather.
We can't change the Earth's orbit or axis of rotation, so there's nothing we can do about the seasons.

But ew are currently changing the weather.
What we call "weather" is effectively a heat engine driven by the Sun.
The more of the Sun's energy we couple into that engine, the more severe the weather becomes.

And the more CO2 we add to the atmosphere, the better we couple that energy into the weather.

[MarkPawelek (OP)]

global warming deniers … will no longer say global warming is a hoax

I can't read minds, like some people here, so I don't even know what global warming deniers will say. I say human global warming is mostly fraud. The premise for global warming is a greenhouse gas effect, GHGE, warming the surface of earth +33C (or is it +60C ?) above what it'd be without its atmosphere. This GHG warming is mostly due to the action of radiatively active gases such as CO2, and H2O(g) - the so-called greenhouse gases, GHG. So we're told. "Back-radiation" emitted by more CO2 and H2O(g) - due to humans (directly or indirectly) - causes extra surface warming - which is, ultimately, responsible for the global warming, causing the "climate emergency". So the narrative goes.

Q: But, where are empirical measurements of this extra "back-radiation"?
A: Nowhere to be found it seems!

Q: Has anyone here so much as read an empirical study of back-radiation?
A: If so, please cite your strongest study.

Q: What kind of "scientist" "believes in" "climate crisis" and "climate emergency" without having read and discussed empirical studies of the back-radiation supposedly causing the climate emergency ?
A: A pseudo-scientist.

Earth's surface is warmer than calculated (by climate alarmists) because their calculations are faulty, and they do not account for adiabatic warming. For current purposes adiabatic warming simply means that the denser an atmosphere is the warmer it will be. Atmospheres of planets and moons are densest closest to the centre of gravity. In the case of rocky planets this is normally at the surface. James Clerk Maxwell explained adiabatic atmospheric warming over a hundred years ago and published it in later editions of his "Theory of Heat" book. Adiabatic compression causes the (dry) Lapse Rate. All planets with atmospheres show adiabatic compression. The Lapse Rate is an effect, beginning with pressures above 0.11 bar. As seen below:

[MarkPawelek (OP)]

in a sterile desert, more life will grow if the temperature falls

No. In a sterile desert more life will grow if there is more water available at the surface. Of course - more water available at the surface will also cause surface temperatures to fall, due to increased evaporative cooling. Temperature is an issue in many hot arid areas - such as the Sahara - due to lack of water. The equator gets more sunlight above it, but also has more clouds, and more water (at the surface) to cool it. So water is the issue in arid areas - not temperature.

BTW: In some arid regions of China day-time, growing season, temperatures fell by over 6C when mass irrigation was introduced. See: Yang/Huang/Tang, 2019

[alancalverd]

People die due to changes in weather- particularly fast changes.

A few people die from rapid temperature change, but you would be among the first to call that weather, not climate. To kill lots of people, the just and merciful god alters the climate so it doesn't rain for several years in hot places, or rthe sun doesn't shine for a couple of years in cold places. Those are my concerns. 

[Bored chemist]

Climate kills people too.
But the people dying of cold in Pune (or even the UK) aren't victims of a cold climate.
They are victims of extreme weather, and more CO2 in that air also drives that problem.

[alancalverd]

The suggestion that we have had extreme cold weather in the UK at any time in the last 30 years is difficult to sustain. What we have had is exceptional poverty, leading to a rash of hypothermia during successively mild winters without snow, and the usual crop of hill walkers who set off in tee shirt and sandals over what has been known for ever as dangerous terrain.

Anyway it's interesting to learn that CO2 makes Britain colder, regardless of the facts. 

[evan_au]

Q: But, where are empirical measurements of this extra "back-radiation"?
A: Nowhere to be found it seems!

Extreme Weather Event Attribution studies use supercomputers to model the Earth's atmosphere under two different assumptions:
1. Carbon dioxide continues at pre-industrial revolution levels
2. Carbon dioxide follows the observed trend with steady increases due to the increasing consumption of first coal, then other fossil fuels

These studies take into account the structure and composition of the Earth's atmosphere, and its effect on clouds, rainfall, temperature, pressure variations and winds.
See https://en.wikipedia.org/wiki/Extreme_event_attribution

[Bored chemist]

Anyway it's interesting to learn that CO2 makes Britain colder, regardless of the facts. 

It will if it disrupts the gulf stream.
But that's only a fact.

[alancalverd]

Has it done so yet? You implied earlier that people had died in the UK as a result of extreme cold caused by increased CO2, when all the data suggests that we have experienced very few low-temperature excursions, and none that might be classed as extreme, in the last 40 years.

I'm sure your argument is entirely logical and based on recorded facts as always, but both the logic and the data elude me.

[Bored chemist]

all the data suggests that we have experienced very few low-temperature excursions, and none that might be classed as extreme, in the last 40 years.

So... you say the cold weather which killed people wasn't extreme.

[alancalverd]

Not me. The meteorological office.  https://www.metoffice.gov.uk/research/climate/maps-and-data/uk-climate-extremes

You can't have your cake and eat it. Either the winter minimum has increased (which I have observed) or recent trends in climate change are a myth. 

Fact is that being old increases your vulnerability to hypothermia, and the population is ageing. Government policy to increase fuel prices, decrease the real value of pensions and benefits, and persuade people to eat "healthily", exposes the poor to an increasing risk of being unable to maintain body temperature even in a mild winter. So if you are old and poor, you don't need a temperature extreme to finish you off: just a few days with your home below 5°C will do the trick.

[MarkPawelek (OP)]

Anyway it's interesting to learn that CO2 makes Britain colder, regardless of the facts.

It will if it disrupts the gulf stream.
But that's only a fact.

More like a lie than a 'fact'. Atmospheric CO2 does not disrupt the Gulf Stream. I'm only stating the null hypothesis here. Someone, somewhere, may have written a model explaining how it can be done. But models don't describe the real world. Even if every single equation in a model has been validated, the way these equations are combined together hasn't been. Non-validated science is fake science when it refuses both the challenge of validation and it refuses to talk to its critics.

[Bored chemist]

But models don't describe the real world.

Yes they do.
That's the point.

Atmospheric CO2 does not disrupt the Gulf Stream.

Nobody actually said it did, did they?
What I said was "It will if it disrupts the gulf stream.".

Do you not understand the word "if", or were you just too busy ranting to read.

Calling people liars for no reason doesn't help you make your case, does it?

Non-validated science is fake science when it refuses both the challenge of validation and it refuses to talk to its critics.

I talk, but you don't read what I say.
Then you falsely accuse me of lying
Which of is faking doing science?