"Abrupt Climate Change" is a relative term.

The United States faces the potential for abrupt climate change in the 21st century that could pose clear risks to society in terms of our ability to adapt.

These changes in climate and related environmental systems can occur over decades or less, persist for decades more, and cause substantial disruptions to human and natural systems.

A 2008 report from the U.S. Global Change Research Program (USGCRP) / Climate Change Science Program (CCSP), Abrupt Climate Change, drew the following conclusions about the prospects for abrupt changes over the next century:

Climate model simulations and observations suggest that rapid and sustained September arctic sea ice loss is likely in the 21st century.

The southwestern United States may be beginning an abrupt period of increased drought.

It is very likely that the northward flow of warm water in the upper layers of the Atlantic Ocean, which has an important impact on the global climate system, will decrease by approximately 25–30 percent. However, it is very unlikely that this circulation will collapse or that the weakening will occur abruptly during the 21st century and beyond.

An abrupt change in sea level is possible, but predictions are highly uncertain due to shortcomings in existing climate models.

There is unlikely to be an abrupt release of methane, a powerful greenhouse gas, to the atmosphere from deposits in the earth. However, it is very likely that the pace of methane emissions will increase.

A 2009 report from the USGCRP/CCSP titled Thresholds of Climate Change in Ecosystems examined abrupt changes in biological systems. One example cited in the report in which a biological threshold has already been crossed is the relatively sudden outbreak of spruce bark beetles that has occurred across parts of the western United States. This has been caused in part by the increase in winter temperatures above a threshold that has greatly enhanced the over-winter survival of the beetles. Another example of an ecosystem threshold is the coral bleaching that occurs above certain levels of ocean acidity and temperature.

According to this report, in order to better understand and prepare for ecological threshold crossings and their consequences, it is essential to increase the resilience of ecosystems and thus to slow or prevent the crossing of thresholds; to identify early warning signals of impending threshold changes; and to employ adaptive management strategies to deal with new conditions and new combinations of species.

The above is taken from the website of the 

The point that I would like to make here is the relative nature of the phrase "abrupt climate change."  Some of us take that term to mean, "in one month."  That's not abrupt, not in climate terms, no, its Instantaneous. If a large change in climate happens in a hundred years, that's still abrupt in climate terms. It usually takes thousands of years for large climate changes to occur.

We don't seem to get that as humans. We think, gee, World War II happened before I was born, so we don't have to worry about World Wars anymore. We think, gee, those millions of people who died in the flu pandemic of 1918, that happened before my Dad was born, so we will never see that again.

Here's the way it works. My wife and I will have a nice little life in climate terms, no problems there. We may have problems from economic messes like the one we are in right now, but we are going to die of old age before climate change really kicks in. Our two daughters? Some problems, but not too bad. Their children? Some pretty serious problems. Their children? We are getting into a bad place. Their children? A little bit worse. Eventually we may get to a generation in which climate change becomes such a big problem that a lot of people wish that they had never been born.

The thing about climate change is that it is cumulative. Once a planetary system is tipped in one direction, it will continue until a countervailing force occurs. We are pouring billions of tons of carbon dioxide into the sky yearly, and we as a species currently have no workable plan to reverse that. We have the goofy idea to use nuclear weapons to open up massive volcanoes to spew dust into the sky to exercise a "global cooling" force to counteract the heat trapping force of the carbon dioxide that has nearly doubled in our atmosphere? That notion has its own possible areas of unintended consequences obviously. We also have the logical idea to replace our burning of fossil fuels with renewable energy, but that idea does involve costs and so far the nations of the world, especially the USA, are paying lip service to that idea while proceeding full speed ahead with business as usual. Yes, we are still building coal fired power plants, despite the fact that coal is basically carbon and there is no workable way to store that carbon post-combustion and, let's say, inject it back into the ground.

Dan E, here on gather, will tell you that climate change is a scam to achieve full employment in the area of research science. I suppose that heart disease is a conspiracy to keep doctors happy? I suppose that when a problem looks intractable, and requires serious sacrifices to deal with, there is a temptation to duck it. That's what we did with the Nazi empire, in fact, until Pearl Harbor woke us up to the fact that oceans are not that wide. I am not going to waste my time hanging around Dan's threads arguing with folks who are not interested in science. So I content myself with telling the truth as I see it (which also, it needs to be mentioned, is the way that the world scientific community sees it).