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Global CO2 Concentration Passes Threshold of 400 ppm -- and That's Bad for the Climate (time.com)
The average concentration of CO2 in the atmosphere hit the symbolic level of 400 parts per million (ppm) for the first time in 2015 and has continued to surge in 2016, according to the World Meteorological Organization. From a report on Time:Scientists say humans may need to take some carbon dioxide out of the atmosphere to stop global warming. The carbon dioxide concentration is unlikely to dip below the 400 ppm mark for at least several decades, even with aggressive efforts to reduce global carbon emissions, according to the WMO report, which confirms similar findings reported last month. Carbon dioxide can last in the atmosphere for thousands of years without efforts to remove it. "The year 2015 ushered in a new era of optimism and climate action," said WMO Secretary-General Petteri Taalas, referring to the landmark Paris Agreement to address climate change. "The real elephant in the room is carbon dioxide, which remains in the atmosphere for thousands of years and in the oceans for even longer."
Just going to note that here's what this means in terms of how the global average temperatures have been changing, and how rapidly so compared to the past:
http://xkcd.com/1732/
Preserving rain-forests doesn't help as much as hippies would like you to think since they are mostly carbon neutral.
See? That's one of those misconceptions floating around. Yes, rain-forests are mostly carbon neutral. But your conclusion is wrong nevertheless. Because while rain-forests are mostly carbon neutral, cutting them down isn't. Each piece of organic matter that is destroyed adds to the carbon foot print, as long as it is not replaced by a piece of organic matter of the same size.
Some people think it is going to be gradual but there are people who think it could be sudden for a few reasons.
Antartic ice sheets are melting at this time, but it is currently trapped by the ice there.
Most people don't think these sorts of things happen regularly, but glacial floods have been seen in the earth's history (as long as you believe the earth older than 6000 years).
Also, the reason that ocean sea level rise has not been seen everywhere up to this point is because the Arctic ice was over water, which meant that no water was added to the ocean. Antarctica and Greenland's ice are not currently a part of the ocean, so when this makes it to the ocean, things are going to go bad around the world.
Aside from the climate change aspect the more immediate problem is acidifcation and warming of the sea which has already killed off a quarter of the barrier reef and is having serious effects elsewhere with plankton.
And this is the other point, we have no idea what effects we are having on plankton populations. But then again, why do we need plankton, it isn't like we need to breathe.