Because it is not the integral, the derivative, or the acceleration that kills you, it is the jerk. (I will explain this line in a less cryptic way in a second)

Most life on this planet will find a way. But remember most life on this planet is not humans, nor is it mammals. Remember with life we also have bacterium, protozoa, chromista, plants, fungi and animals and we then have to subdivide animals into the various invertebrates such as insects, arachnids, molluscs, crustaceans, corals, and the others of the invertbrates class, and then the vertbrates fishes, amphibians, reptiles, birds, mammals

Lets ignore the plants, bacterium, and fungi for a moment and focus on the Animals.

19 out of 20 animal species on this planet are the invertebrates and they are far more susceptible to changes of PH, temperature, etc and less adaptable. Only about 60,000 animal species are the vertebrates. Remember there are a little more than 60,000 vertebrate species, stuff like mammals which is only about 5,000, birds which is about 10,000, reptiles 10,000, fish over 30,000, amphibians about 7,000. But invertebrate species are over 1.3 million species.

So lets go back to my math and physic joke that started my response to you LiterateDog. It is not the velocity you are going at in respect to time (aka the speed) nor is the acceleration of the velocity in respect to time (aka the 1st derivative of the velocity) that kills you. No the system shocks are caused via the 2nd derivative in respect to time, which is nicknamed in physics as the Jerk, but also known as the jolt, surge, or lurch. In Looney Tune parlance this is the sudden splat when your body hits the perpendicular surface, or the sudden instantaneous speed increase. You feel the g forces not with the velocity or the acceleration, but instead when the jerk hits you and the hangover occurs.

I have no doubt life will find a way, I have no doubt humans will find a way. But I think it is self obvious that 2nd the second derivative with respect to time, is often a source of pain and do we want to create more sudden jerks or to try to prevent jerks from occurring.

https://en.wikipedia.org/wiki/Jerk_(physics)

Maybe the jerk in the long term will turn out to be a good thing but we really do not know that until it happens, but we do know those jerks also have the possibility of killing us, or making our lives a little bit less fun and a little bit more miserable so why don't we plan things out and do a more gradual rate of change instead of a sudden lurch.

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Oh and it may not be global warming that is the biggest threat to the various species of life on this planet but instead the PH changes of acid vs basicity in the oceans. That is something we actually have influenced far more in the last 200 years than we influenced global temperatures. We increase the acidity of the ocean about 25 to 30% in the last 200 years. Now that is only a change of 0.1 on the PH scale so it does not seem significant but from an organic standpoint that is a vast change for it changes which catalyst enzymes work and which don't and it also changes the effectiveness and the efficiency of those catalyst enzymes. Aka stuff like can you make shells out of calcium is affected via acid ph of the sea

http://ocean.nationalgeographic.com/ocean/explore/pristine-seas/critical-issues-ocean-acidification/

https://en.wikipedia.org/wiki/Ocean_acidification

All of this is because we are turning normal water (salt water) into something more like carbonated (salt water) for we are literally doing the same thing with water...which is adding C O 2 to it the make carbonic acid, aka the fizz in Soda Pop like Coca Cola.

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It may in the long term be a good thing for the environment, but to borrow an 80 year old phrase from one of the Economic Theory great guys (and no Donald Trump did not coin this phrase)

The quote is from A Tract on Monetary Reform- by John_Maynard_Keynes. Note this was Milton Friedman favorite book on Keynes. Keynes at the time of A Tract on Monetary Reform where Keynes made the points of this book several years prior to the Great Depression, Keynes argues that prices are information and sudden changes in prices can lead to destabilized markets (for it leads to bad allocation of information and resources) and this is something Friedman agrees with Keynes on sudden Jerks in the information leads to non effective markets, aka non effective utilization of resource maximization via the collective and the individual.