Check out the screen capture below which shows that today Friday 16-02-2018 an area of our planet hit 500 ppm CO2. The New York region. The lowest levels I found were 395 ppm and only in a few very remote places. So the global range is now 395 to 500 ppm. This is locked in and will not change for a long time even if we stopped all emissions today and so all we have to do is look back to the last time the planet’s atmosphere had these levels to determine what will, without any doubt, be the result. You have to keep in mind the system is like a big heavy railway carriage a worker is trying to move using a lever, getting the carriage moving will take a lot of effort and the initial movement will be slow but very quickly it will gather speed and start moving down the tracks with little extra input from the worker. The only way to safely stop it would be to stand aside and let it run out of kinetic energy. In a similar way the atmosphere is slow to react to changes in its chemistry but once change starts and it has quiet dramatically, it will flip to another state of balance but, because emissions continue there is no possibility of a next state of balance until the source of greenhouse gases is eliminated (civilization). It so to speak will just keep flipping.
Data source: earth null school.
What is now locked in for sure at this present range is the mid Pliocene climate of about 3.6 million years ago when the Arctic was ice free as was the west Antarctic (see picture below) and sea levels were 25 METRES (82 Feet) higher than today. If you live in a coastal town or city and its very likely you do, go down to the sea edge at high tide and imagine where the beach will be in the not too distant future. Rate of melt is still subject to difference of opinion but some such as James Hansen have found it will be much faster than first estimated.
If money matters – the cost of global ‘natural’ disasters in 2017 was 306 billion US dollars according to insurance company Swiss Re who do the maths ever six months. That is about double the 188 billion of 2016.