Re: What is YOUR view?

RonO wrote:

On 4/7/2024 5:55 PM, William Hyde wrote:

RonO wrote:
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We are putting out a lot of carbon dioxide into the atmosphere.  Some people worry about methane, but the effect is likely negligible because methane doesn't last very long in the atmosphere.

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They are right to worry.  The effect of CH4 is about .5 Watts per square meter as compared to pre-industrial times.  Crudely speaking, this accounts for about a quarter of a degree of warming.
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Why is it so?  Well, the mean lifetime of CH4 in the atmosphere is not that short, being about 11 years.  As it is far more effective at absorbing IR than CO2 it can add a lot of heat before it is gone.
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When it does break down, some of it becomes stratospheric water vapour, which is an excellent greenhouse gas itself.  And this effect lasts.
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The effect of a unit of methane put into the atmosphere, over a century, is still larger than that of a unit of CO2, though the CH4 will be long gone at the end of that period.
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It's short lifetime hasn't stopped us from increasing the amount in the atmosphere. CO2 levels have not yet doubled from pre-industrial times, but CH4 is up 160%.
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Finally, the bio-geochemistry of CH4 works against us.  As the world warms, microbes more actively devour our stock of sequestered organic carbon, producing more CH4 and CO2.  Arctic soils, in particular, hold vast amounts of frozen organic matter - far more  than tropical soils. Field experiments have shown that the rate at which arctic areas are giving off greenhouse gases is increasing. This positive feedback could grow very nasty indeed.
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  We likely did

accelerate global warming with our increased output of carbon dioxide, but we did it at a time when global temperatures had already been increasing for thousands of years.

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Time scales matter.
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The earth has warmed about 4C since the last glacial maximum about 20k years ago, most of that in the first 10k.  We have now warmed the earth one degree C in less than two centuries.  And eight billion of us depend on the ecosystems which were well adjusted to that earlier climate.
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It appears that already forests in parts of the world are no longer stable ecosystems.  Many will be replaced by more fire-resistant (and less useful) trees, or by grass or scrub.   And that's just the beginning.
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We need to better define what the crisis is.
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We probably should be nearing the end of the current warming period. For the last million years we have had the 100,000 year ice age cycles. The earth has been cooling for the last 3 million years, but for the last million we went to a cycle of around a hundred thousand years of cold interspersed with 20 to 30 thousand years of warmer climate.  The temperatures of the cycles seem to have become more extreme in the last 500,000 years.  The last warm period got warmer than it is now, and more ice melted and sea levels were 20 meters higher than they are now.

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Eemian warmth was different.  At this time the orbital eccentricity was more than double the current value.  With perihelion occurring in summer,  this led to strong increases in summer temperatures, decreases in winter.  The obliquity was also larger, meaning more heat in higher latitudes.
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The problem is that our temperature proxies are mostly summer ones - winter does not leave us a lot of records. Tropical records can also be difficult to work with, so there is a bias towards temperate and polar records.   Eemian warmth is mainly summer warmth, and not directly comparable to our little experiment which will be year-round warmth, with a bias towards winter and higher latitudes.
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And, once more, the Eemian world did not have to support eight billion
people.
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   We

have not reached that point, yet in this cycle, so things are not yet as bad as they got without human industrial interference.
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There was an article put up on TO, maybe a decade ago, that claimed that the current carbon dioxide levels could prevent a recession into another ice age.

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As one of the authors of such a paper, I have to disagree with your interpretation.
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   We might delay the next ice age.  This really doesn't seem to

be that bad.

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Nor would it be good.  Ice ages begin very slowly in human terms.  If we still are an industrial society when the next one comes along - some time in the next twenty thousand years - we will be able to deal with it.
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Worrying about a future ice age at this point is equivalent to Julius Caesar worrying about world war II.
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  We got a taste of what things would be like when

temperatures fell for the mini ice age that started in the 1300's and didn't end until the start of the industrial revolution that is supposed to be responsible for our current global warming.

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The little ice age ended well before CO2 from industry became a significant factor in climate.  It has been shown that stratospheric aerosols caused by increased volcanism account for about 60% of the little ice age cooling.  Given the noisy data, that's about as good as can expect, though solar, GHG and land-use effects were also accounted for.
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   The earth has seen

warmer climates that had more ice melting and sea levels rising to the levels that they claim may occur this time, but they obviously happened before.  So the regions that will be flooded will just be a repeat of what happened last time a hundred thousand years ago.

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You are drawing parallels where there are no parallels.  See above.
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William Hyde
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 It looks like you didn't comment relevantly on that topic, just denied it with no discussion.

Really?  You started with the claim that methane is not an important greenhouse gas, and I went into some detail to show that it in fact is.
Then you went on to speculate that global warming might save us from an oncoming ice age, and I reminded you that while an ice age is coming soon in geological time, it is very far away in human time, while damage from global warming is not.
I did not mention ocean acidification, another consequence of our atmospheric pollution.   I gather from biologists that this is also rather important.
  The paper that was put up on TO did predict that

we might skip the next ice age.

Actually this is not a new idea.  I first saw reference to in in an Asimov essay in the 1960s, discussing Milankovitch theory.  It also appears in a book I've recommended here many times, "Ice Ages - solving the Mystery", by Imbrie and Imbrie, published some time in the mid 70s.
Indeed,there was an SF novel circa 1990 which had a new ice age caused by people following those crazy environmentalists.  Another SF writer, George Turner, had the same idea, but played it more subtly (the novel titles are "Fallen Angels" and "The Sea and the Summer"  - also titled "The Drowning Towers".)
   I recall the paper was published a

couple years before the Top Six were put out so that would be around 2015.

Our paper was:
"Transient nature of late Pleistocene climate variability", Thomas J. Crowley & William T. Hyde
Nature volume 456, pages 226–230 (2008)
It was mentioned in this group a few years later.
The next ice age wasn't the real point of the paper, which talked about a larger and more significant change which might occur in the next 50,000 years.
   I haven't heard much about it since.  You may have written

something similar, but didn't come to the same conclusion.

Of course we did.  And we knew it would be abused by the denialist community, as it immediately was.
I've been involved in three papers which had as their point that some of the worst case scenarios for GW might not happen, and in each case some in the denialist community claimed that we had "proven" that climate change was not a problem at all. Those who deal with creationists will not be surprised.
Putting off the next ice age is about as urgent as dealing with the flu season in 6629.  Climate change is a problem now, not thousands of years in the future.
If we achieve a stable climate, and the natural progression of the ice ages kicks in, we will be easily able to deal with it.  Assuming we are at at least the current level of technical ability, that is.
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likely that before that paper was published, no group had made a similar prediction, since I did not recall any such previous prediction.
 If just as much ice melts as melted last time, why wouldn't sea levels reach the same depths?  Sea level was 20 meters higher than it is now,

That is off by a factor of two or three, probably due to an imperial to metric switch.  But it doesn't matter.

or were you claiming that not as much ice was going to melt this time?

If we carry on sea level will rise far higher than in the Eemian.
West Antarctica and Greenland are vulnerable to melting and even partial collapse, and together could contribute about twelve meters of sea level rise.   Most of the ice is in East Antarctica, which is dynamically stable at the moment, but still melting.
The total contribution of all three ice sheets is over sixty meters, and while it's hard to imagine what we could be that stupid, if we are the thermal expansion of sea water would kick in an extra ten meters or so.   That would take millennia, though.  The melting could be done in a few centuries if we are crazy enough.
We simply cannot state with any precision what amount of melting we would get with a given temperature rise.  But it seems unlikely that we will stop short of 2.5C, and it is difficult to imagine that this won't eliminate most of our smaller ice sheets, for a rise of at least six meters, plus whatever happens to East Antarctica.
Note also that sea level rise will not be uniform.
William Hyde