It’s probably not impossible that the Earth could end up like Venus but there is fairly well accepted evidence that CO2 concentrations were much higher in the past (10 to 20 times higher than today) without Venus like temperatures.
While these measurements give much less precise estimates of carbon dioxide concentration than ice cores, there is evidence for very high CO2 volume concentrations between 200 and 150 Ma of over 3,000 ppm and between 600 and 400 Ma of over 6,000 ppm.
Ok, and how was life like at those times? There are parts of Australia today that are so hot that it is impossible for any human to survive there yet you will find plants and insects and maybe some animals there.
AFAIK temperatures above 90°F(33°C) may already be deadly for humans in poor health conditions.
There was abundant plant and animal life under those conditions: 200 to 150 Ma is pretty much the Jurassic period and 400 to 600 Ma would have encompassed the Cambrian explosion. According to Wikipedia mean temperatures during the Jurassic period were about 3C and during the Cambrian about 7C above today’s. Certainly nothing like Venus where surface temperatures are around 480C. Almost no known life could survive those temperatures, except perhaps some of the lifeforms found around black smokers.
It’s not obvious to me that global warming will shrink the total human-habitable area of the globe. As someone living in Moscow, I’d like some warming right now! Sick of those six-month-long winters already. Also check out Siberia, Canada, etc.
I read an argument to the effect of: More people die annually of cold than of heat, global warming good.
On the other hand, there is that bit about ice melting and destroying the jet stream leading to massive global cooling. I don’t know how good that science is though.
You can’t be serious. Sure, I get your point in regard to the cold winters and I know others who argue the same way, but the thing is, no one has an exact idea of what will change in the world once the temperature rises a few degrees. More melting of ice will change the salinitiy of the sea and cause a change in sea currents which might precipitate a new ice age, this is one possibility in which Moscow will become much colder.
There already were some extreme heat waves in Europe during summer that killed thousands of people.
Our biosphere is a complex system and how goes the saying? “Never change a running system.”
It’s true that climate is too complex to predict well. Still, I haven’t heard many global warming worriers warn about the threat of a new ice age. It’s all about the world actually becoming warmer.
Given that, the real problem seems to be the speed. If it took 1000 years to raise 5 degrees, that might not be so bad. If it’s 50 years, the necessary adjustments (to both humans and non-humans) might only happen with massive die-off.
But leaving aside the speed, it’s not insane to notice that there is vastly more biodiversity in the tropics, than in the arctic. If you were designing a planet for humans to live on, a little warmer is a whole lot better than a little colder.
This doesn’t mean that global warming is “good”. But you shouldn’t dismiss the positive changes out of hand, when evaluating the future pros and cons.
But leaving aside the speed, it’s not insane to notice that there is vastly more biodiversity in the tropics, than in the arctic. If you were designing a planet for humans to live on, a little warmer is a whole lot better than a little colder.
You are operating under the assumption that warmer implies more tropics. I categorize this as wishful thinking.
Right. And the problem is not only the concerns we have but those we don’t have. The unknown unknowns. The climate system is so complex that no one can predict the outcome of further warming. What we know is scary enough to be worried.
It’s probably not impossible that the Earth could end up like Venus but there is fairly well accepted evidence that CO2 concentrations were much higher in the past (10 to 20 times higher than today) without Venus like temperatures.
(levels today are around 380 ppm)
Ok, and how was life like at those times? There are parts of Australia today that are so hot that it is impossible for any human to survive there yet you will find plants and insects and maybe some animals there.
AFAIK temperatures above 90°F(33°C) may already be deadly for humans in poor health conditions.
There was abundant plant and animal life under those conditions: 200 to 150 Ma is pretty much the Jurassic period and 400 to 600 Ma would have encompassed the Cambrian explosion. According to Wikipedia mean temperatures during the Jurassic period were about 3C and during the Cambrian about 7C above today’s. Certainly nothing like Venus where surface temperatures are around 480C. Almost no known life could survive those temperatures, except perhaps some of the lifeforms found around black smokers.
It’s not obvious to me that global warming will shrink the total human-habitable area of the globe. As someone living in Moscow, I’d like some warming right now! Sick of those six-month-long winters already. Also check out Siberia, Canada, etc.
I read an argument to the effect of: More people die annually of cold than of heat, global warming good.
On the other hand, there is that bit about ice melting and destroying the jet stream leading to massive global cooling. I don’t know how good that science is though.
You can’t be serious. Sure, I get your point in regard to the cold winters and I know others who argue the same way, but the thing is, no one has an exact idea of what will change in the world once the temperature rises a few degrees. More melting of ice will change the salinitiy of the sea and cause a change in sea currents which might precipitate a new ice age, this is one possibility in which Moscow will become much colder.
There already were some extreme heat waves in Europe during summer that killed thousands of people.
Our biosphere is a complex system and how goes the saying? “Never change a running system.”
It’s true that climate is too complex to predict well. Still, I haven’t heard many global warming worriers warn about the threat of a new ice age. It’s all about the world actually becoming warmer.
Given that, the real problem seems to be the speed. If it took 1000 years to raise 5 degrees, that might not be so bad. If it’s 50 years, the necessary adjustments (to both humans and non-humans) might only happen with massive die-off.
But leaving aside the speed, it’s not insane to notice that there is vastly more biodiversity in the tropics, than in the arctic. If you were designing a planet for humans to live on, a little warmer is a whole lot better than a little colder.
This doesn’t mean that global warming is “good”. But you shouldn’t dismiss the positive changes out of hand, when evaluating the future pros and cons.
You are operating under the assumption that warmer implies more tropics. I categorize this as wishful thinking.
Then you aren’t listening enough, I’m afraid. This is a routine concern.
Right. And the problem is not only the concerns we have but those we don’t have. The unknown unknowns. The climate system is so complex that no one can predict the outcome of further warming. What we know is scary enough to be worried.
Huh? The Earth once was significantly warmer than now with no runaway consequences.