Svante Arrhenius's Prediction of Climate Change

It would be interesting to look into whether they had good reasons for thinking this at the time.

Henry's Law? Correct me if I'm wrong, but the oceans hold something like 98% of the CO2 in the biosphere, so it's easy to predict that in equilibrium they'll absorb something like 98% of the fossil carbon we add to the biosphere. It might not have been as easy to predict the transient behavior; IIRC the oceans are only absorbing CO2 at roughly a third of the rate at which we're now emitting it, just because the mixing processes are so slow.

It seems to me there is a difference between doing science (in particular, figuring out the ways in which the physical world works) and making far-future predictions.

When Newton described the law of gravity he did not make far-future predictions about objects falling. He just discovered a law of nature. In the same way, Arrhenius was trying to figure out how the link between atmospheric CO2 and global climate works. It's just normal science and as such doesn't offer evidence for or against far-future predictions.

Oh, and by the way, whether global warming has positive or negative net impact critically depends on its magnitude. Minor global warming (up to about 2 degrees C, I believe) is commonly considered beneficial.

I think that this case study should cause one to update away from predicting the far future being useful

This should be a pretty tiny update, though, since it's only one case study, and it's a mere surface impression.

I think that this case study gives evidence against attempting to predict the far future being useful

Isn't it evidence for a more narrow conclusion? Specifically, that attempting to precisely predict the far future isn't going to work well? Arrhenius was correct that climate change was going to happen, just wrong about several particulars. Or was he right for so many wrong reasons that it's not worth noting?

"People later thought that Arrhenius's prediction that atmospheric carbon would increase was wrong, because they thought that oceans would serve as great carbon sinks. It would be interesting to look into whether they had good reasons for thinking this at the time."

The oceans contain about 50× as much CO2 as the atmosphere, and they're estimated to be removing CO2 from the atmosphere about 1/4 as fast as mankind is adding it. (The terrestrial biosphere is also estimated to be removing CO2 from the atmosphere, through "greening," about 1/4 as fast as mankind is adding it, so if anthropogenic CO2 emissions fell by more than half then atmospheric CO2 levels would be falling, rather than rising.)

So, the principle was correct, it's just that those "negative feedbacks" are not keeping up with the high rate at which mankind is emitting CO2.

"Arrhenius predicted that global warming would have positive humanitarian impacts on balance, global warming now appears to have negative humanitarian impacts on balance. "

No, Arrhenius was right even about that.

The best evidence is that manmade climate change is benign, and CO2 emissions are very beneficial, for both mankind and natural ecosystems. I’m one of over 30,000 American scientists who’ve signed a “petition” attesting to that fact.

CO2 is “plant food.” Are you old enough to remember when terrible famines were often in the news, in places like Bangladesh? Throughout history, famine was one of the great scourges of humanity, the Third Horseman of the Apocalypse... until now.

Thankfully, famines are becoming rare, and one of the reasons is rising CO2 levels, which have increased worldwide agricultural productivity by about 20%.

http://tinyurl.com/1920sciamCO2

http://co2science.org/data/plant_growth/plantgrowth.php

If we lacked that additional productivity, mankind could approximately make up the difference by putting all of the world's rainforests under cultivation.

Those benefits are well-measured, by thousands of agricultural studies. The supposed major harms are all just hypothetical.

Rising CO2 levels not only make plants healthier and more productive, they also make them more water-efficient and drought-resistant. One of the consequences is that the Earth is "greening," especially in some arid regions, like the Sahel (southern Sahara), as reported in National Geographic:
https://www.sealevel.info/Owen2009_Sahara_Desert_Greening-atGeo30639457.html

EXCERPT:
“Images taken between 1982 and 2002 revealed extensive regreening throughout the Sahel, according to a new study in the journal Biogeosciences. / The study suggests huge increases in vegetation in areas including central Chad and western Sudan. ...
“’Before, there was not a single scorpion, not a single blade of grass,’ he said. “’Now you have people grazing their camels in areas which may not have been used for hundreds or even thousands of years. You see birds, ostriches, gazelles coming back, even sorts of amphibians coming back... The trend has continued for more than 20 years. It is indisputable.’”‍‍‍‍‍‍

We are currently enjoying what has traditionally been called a "climate optimum." It is generally acknowledged that the Earth has warmed, on average, about 1°C (±0.4°C) since the "pre-industrial" Little Ice Age, and it is also generally acknowledged that the warming has been beneficial. Yet activists claim that warming more than another 0.5 °C would be harmful, rather than beneficial. That claim is not based on scientific evidence, and is not credible.

The direct impacts of global warming are obviously minor. Except at high northern latitudes, where "Arctic amplification" makes the brutal winters there a bit milder, we’re on track for at most about one degree of additional warming by 2100 (and even that assumes no large-scale transition to nuclear energy). At temperate latitudes, that’s like moving only about 70 miles south, or planting only about one week later.

So folks promoting solar and wind boondoggles hype other supposed harms, like sea-level rise, or extreme weather, or polar bears' peril. But those problems aren’t actually happening.

CO2 has been rising steadily for 2/3 of a century, yet sea-level rise has not detectably accelerated:

https://sealevel.info/1612340_Honolulu_Wismar_Stockholm_vs_CO2_annot3.png

https://sealevel.info/MSL_global_thumbnails5.html

Hurricanes & typhoons are not worsening:

https://sealevel.info/frequency_12months_2018-09-30_with_trendlines.png

https://sealevel.info/global_running_ace_2018-06.png

Strong tornadoes have actually declined:

https://sealevel.info/EF3_to_EF5_tornadoes_historical_woodtv_dot_com_annot1_1006x759.png

And the polar bears are fine:

https://polarbearscience.files.wordpress.com/2015/05/crockford-unofficial-polar-bear-numbers-to-2015-sept-1-final1.jpg

Here's what Arrhenius wrote:

https://sealevel.info/Svante_Arrhenius_p63_excerpt_touting_the_good_news_of_global_warming3.png

Notice that he even predicted "polar amplification."

The best evidence indicates that he was exactly right.

Arrhenius predicted that global warming would have positive humanitarian impacts, for reasons that are retrospectively wrong, and instead global warming appears to have negative humanitarian impacts.

This seems like an oversimplification. It would seem more accurate that Arrhenius thought on balance it would have a net positive humanitarian impact and current consensus is that it is net negative.