Re: What is YOUR view?

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

RonO wrote:
 

>
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.

  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.
 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.
 When it does break down, some of it becomes stratospheric water vapour, which is an excellent greenhouse gas itself.  And this effect lasts.
 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.
 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%.
 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.
   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.

 Time scales matter.
 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.
 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.

  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.
 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.
 And, once more, the Eemian world did not have to support eight billion
people.
     We

have not reached that point, yet in this cycle, so things are not yet as bad as they got without human industrial interference.
>
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.

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

be that bad.

  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.
 Worrying about a future ice age at this point is equivalent to Julius Caesar worrying about world war II.
    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.

  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.
      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.

 You are drawing parallels where there are no parallels.  See above.
  William Hyde
 

It looks like you didn't comment relevantly on that topic, just denied it with no discussion.  The paper that was put up on TO did predict that we might skip the next ice age.  I recall the paper was published a couple years before the Top Six were put out so that would be around 2015.  I haven't heard much about it since.  You may have written something similar, but didn't come to the same conclusion.  It was 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, or were you claiming that not as much ice was going to melt this time?
Ron Okimoto