Why is the 2 degrees temperature heating key to stopping climate change?

This is complete fiction. The very fact that it is a round number should be a clue that this is not a scientific assessment, it is political.

For some reason the "powers that be" have fallen for the Catastrophic Anthropogenic Global Warming (CAGW) story. Quite apart from the fact that this theory has no proof - see my answers to other questions - it is pure arrogance to think that mankind can do anything to affect the enormous, billions-of-years-old natural forces that control the climate.

The 2 degrees refers to the average temperature of the Earth. To begin with - what exactly is that and how do you measure it? Bringing that more to home - what is the average temperature of a room at a point in time? How many measurements do you take and where within the room? Multiply this to encompass the enormity of the Earth - its valleys, mountains, oceans (surface to deep), ice caps, lakes, tundra, forest, cities, top of the atmosphere... it's a meaningless number.

And is it not the case that the ecology of the Earth adapts to much more than a 2 degree variation all the time - even in temperate climates that's less than the difference between day and night temperatures, and when you consider deserts and seasons - 2 degrees is totally unnoticeable.

And in any case, who says that 2 degrees warmer is a bad thing? Would we rather be plunged into a deathly ice age?

Climate will change whatever mankind does.

Rather than try and fight futilely against natural forces, at enormous cost, wouldn't it be better to accept that climate will change - one way or the other - and make plans for ADAPTATION.

New York will NOT be inundated by sea-level rise in any time scale that prevents adaptation. The same goes for any other manifestation of climate change. Man has always adapted to previous climate changes. For example - the Greenland Ice Sheet is melting. The receding ice is uncovering FARMS, dated to the 10th/12th centuries. So it was warmer then than now. Vikings moved in and started farming. It got cold (nobody knows why). The farmers moved away. Not overnight, but gradually as it became nore and more difficult to raise crops. It's now getting warmer (nobody knows why). Maybe it will get warm enough for farming to recommence there. I hope so - rather that than a global freeze.

Forget the 2 degree nonsense. Plan for adaptation.