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Most of the commonly mentioned effects of the ongoing and predicted climate change are negative: more extreme weather effects, more destructive weather, more diseases, rapid extinctions, etc.

Why is this so?

It is clear that any rapid change brings many negative effects. We humans, as well as the biosphere, are adapted to the current conditions. Any sudden deviation from these conditions will take painful re-adaptation.

But my impression is that several of the commonly mentioned negative effects go beyond than what can be explained by just change. Is this really so? If yes, would a cooling climate (beyond restoring pre-industrial conditions) bring more positive effects?

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    $\begingroup$ This is, unfortunately, a highly politically charged topic which makes it hard to find reliable information on the web. A typical web search results mostly in articles that are emotionally charged, politically motivated, simple opinion from a random person with no qualifications, or just too dumbed down. My question is an honest one, and I hope it will get a reasonable answer here. $\endgroup$ – Moose Jan 6 at 13:47
  • $\begingroup$ A added the word "predicted" to clarify that I am referring to the one in the present time, not any other one during the history of the Earth. Feel free to phrase it better and edit. $\endgroup$ – Moose Jan 6 at 13:57
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    $\begingroup$ What effects do you think don't fall in to the "change" category. $\endgroup$ – John Jan 6 at 20:03
  • $\begingroup$ @John For example, more extreme weather events. $\endgroup$ – Moose Jan 7 at 9:16
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    $\begingroup$ Most of the commonly mentioned effects -> because in the media, negative things are usually considered more newsworthy. And that could be justified because it has larger consequences. $\endgroup$ – Jan Doggen Jan 10 at 16:25
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I would say that the reason is because human civilisation, and particularly agricultural practices, evolved and are adapted to the pre-industrial climate. This means that any substantial change in the climate will require changes in our civilisation and agriculture, which inevitably has a cost. So the reason that most of the changes are negative is not to do with the science, but to do with us.

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  • $\begingroup$ Partly true, IMO. A fundamental change in subsistence would help, let go of the doctrine of constant growth and switch to an economy without stashing money. The concept of "cost" is an artificial one, introduced with the way our economy works. The main "negativity" though is that we destroy our base of living, that on a timescale of 400-3000 years the earth may not be a place for animals like humans any more if we continue like this. $\endgroup$ – ebv Jan 15 at 10:15
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    $\begingroup$ Not just human society (broader than just civilisation). AGW induced climate change is already seriously impacting many, many other species, and even entire ecosystems. The reasons are the same that you have given - evolution is a matter of adaptation to prevailing conditions. Conditions change => evolutionary fitness to prevailing conditions decreases more often than not (e.g. it can be beneficial for some species in some situations, but the average impact will be negative). All human societies rely on non-human ecosystems to some extent too, so there are flow-on effects back to us. $\endgroup$ – naught101 Jan 15 at 23:48
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I don't think there are any effects of climate change, which can be said to be particularly positive.

The level of CO2 in the atmosphere we're currently experiencing has not been seen on earth for about 800,000 years IPCC AR5 and the consequences of this change in radiative forcing are massive. Particularly as we've engineered this change in the last 150 years or so (ridiculously fast as far as natural systems are concerned). The change is extremely large in magnitude and speed - and this is going to have a huge impact - so I think you're right in that pretty much any change is bad change. My best shot at some positive human results are

1) an ice-free northwest passage round the top of Canada and

2) a marginal improvement in the UK for agriculture

These are of course completely outweighed by the other costs - in both human and natural systems.

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    $\begingroup$ It is an anthropocentric point of view. Thermophile organisms might have a different opinion! (just kidding) $\endgroup$ – Jean-Marie Prival Jan 7 at 18:48
  • $\begingroup$ Fair point! I guess it's possible that some form of algae or bacteria will do very well out of it - and rats and mosquitoes seem to like everything we do. I'd argue that this is outweighed by the catastrophic damage to other organisms though... $\endgroup$ – Will Jan 8 at 8:45
  • $\begingroup$ Positive effects? In UK thousands of old folk are speeded on their way to the promised land by hard winters, so milder winters will save thousands of lives. Another beneficial effect is that the N.W and NE Passages will be opened up to shipping, enabling them to take short cuts to their destinations, use less fuel and thus cut CO2 emissions. Another benefit, provided the heating doesn't go too far, is that warm climates have greater biodiversity than cold climates. Of course, that means cold-loving species like Gyrfalcons and Ptarmigan will be pushed further north or onto higher ground. $\endgroup$ – Michael Walsby Jan 8 at 10:36
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    $\begingroup$ @MichaelWalsby Please post answers as answers, not as comments. $\endgroup$ – gerrit Jan 10 at 10:53
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    $\begingroup$ I can think of a lot of locally-positive effects, and lots of locally-negative effects. All else being equal I imagine that the negative would outweigh the positive, simply because there's more land at low latitude (hot places) than there is at high latitudes (cold places that might benefit). Not sure how valid that rather simplistic analysis is ;-) The net effect is modulated by the speed, and hence that it isn't pain free (to say the least) for populations to move. And of course things like ocean acidification are global negatives. $\endgroup$ – Semidiurnal Simon Jan 10 at 11:48
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If you consider what climate is -- the typical range of temperatures, precipitation, and other meteorological conditions that a region experiences -- and the fact that both nature and human society and civilization have adapted to the regional climates across the globe, then you can see that any substantial and relatively rapid change is likely to have what we would perceive as negative effects.

This is just a broad illustration, but for example, there's a vast swath of the north hemisphere suitable for growing wheat because of a combination of soil quality, available precipitation, and growing degree days (crop heat units). Farms, cities, roads, and other infrastructure have been built around this cropland for generations to take optimal advantage of existing conditions and reduce costs for delivering the wheat to market. More crop heat units can make a region more productive, but daily temperatures above 82 degrees will start stressing and killing the plants. Even if land closer to the poles becomes more farmable -- no guarantee -- simply changing what can be brown at a given latitude can reduce a nation's ability to feed itself.

There are other ways in which human civilization has adapted to current regional conditions: Communities rely on air conditioning in the summer and/or heating in the winter to make regions tolerable. Harbors and coastal communities are built to suit current sea levels. In general, increased temperatures will make warmer regions less tolerable and more expensive to live in (through cooling and similar costs) and more prone to deadly heat waves, while potentially making colder regions more tolerable and less expensive (through reduced heating costs). Similarly, dramatic cooling would also affect where everything grows, reduce growing degree days for growing plants, and making colder regions less tolerable and more costly.

While attempting to quantify the "Country-level social cost of carbon," a 2018 study in Nature Climate Change by Kate Ricke, et. al. assessed the net economic impact on individual countries and concluded that the costs are "unevenly distributed": "Countries that incur large fractions of the global cost consistently include India, China, Saudi Arabia and the United States."

Northern countries such as Russia, Canada, Norway, Sweden, the United Kingdom, France, Germany, and Poland actually receive a slight direct benefit from climate change through factors such as reduced heating costs.

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Much has been said about the negative effects, but there are positive effects as well. In UK thousands of old folk are speeded on their way to the promised land by hard winters, so milder winters will save thousands of lives. Excessively hot summers can also cost lives, but in UK those killed by cold weather greatly outnumber those killed by heat waves. Another beneficial effect is that the NW and NE Passages will be opened up to shipping, enabling ships to take short cuts to their destinations, use less fuel and thus cut CO2 emissions. Another benefit, provided the heating doesn't go too far, is that warm climates have greater biodiversity than cold climates. Of course, that means that cold-loving species like Gyrfalcons and Ptarmigan will be pushed further north or onto higher ground (Gyrs have never bred in Britain,Ptarmigan do,and Snowy Owls occasionally). A number of new species including Little Egrets and Cattle Egrets are already colonising the south of UK.

A cooler climate would also have both positive and negative effects, but we are not likely to get that for some considerable time.

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    $\begingroup$ England has no hard winters, the low averages are not even below 0. $\endgroup$ – ebv Jan 10 at 15:19
  • $\begingroup$ I live in England , so I should know, and I've lived here for a very long while. It.s not the averages that kill people, but the below average temperatures. In Shropshire, 1982, the temperature was -26C. $\endgroup$ – Michael Walsby Jan 10 at 15:50
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    $\begingroup$ Yeah, you can celebrate that :-) Warm climates greater biodiversity than cold ones ? nature.com/articles/s41467-018-07880-w $\endgroup$ – ebv Jan 10 at 16:07
  • $\begingroup$ Th4ere are more species in a square mile of tropical rainforest than on the entire Antarctic continent. $\endgroup$ – Michael Walsby Jan 10 at 17:21
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    $\begingroup$ "warm climates have greater biodiversity than cold climates" is not strictly true. Biodiversity is highly dependent on water and nutrient availability. See figure 3 of researchgate.net/publication/… for example. Deserts in the tropics have low biodiversity. Also, biodiversity will not necessarily increase in temperate zones with warming - many locally adapted species will die off, and only some species from warmer regions will invade. Speciation is not likely to have major impacts in the short term. $\endgroup$ – naught101 Jan 15 at 23:55

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