I do not ascribe every warm day or tornado to the effects of global climate change. I do not look at each heavy rainfall and announce, "That happened because of global climate change." I do not consider myself an expert on climatology. It annoys me when someone says they looked in the rain gauge chart and discovered rainfall was normal, or that they looked at a temperature chart and discovered that there were several low temperatures during a hot spell and therefore the scientists who study global climate change are wrong. This is equivalent to going to a doctor's office and looking at x-rays of cancer and saying, nope, that doctor is wrong, there is no cancer, because I feel fine.
But I do look at each natural event and judge whether it could be influenced by global warming. Many events seem to be influenced by global climate change, while others are indirectly influenced. For example, Hurricane Sandy came very far north for a tropical storm while still maintaining hurricane-force winds. The increased warmth of the Atlantic Ocean may have influenced this northern thrust.
The height of the storm surge was affected by the sea level rising at New York City by 12 inches during the last century and the land there subsiding 3-4 inches during that time. The subsidence is caused by the melting of glaciers after the last Ice Age. The land that used to be covered by ice is now rising slowly, relieved of the massive weight. The land around NYC was not covered by ice, so it is sinking, like the other side of a seesaw from the rising ground to the north.
The National Oceanic and Atmospheric Administration (NOAA) states that, while Global Warming may not have caused Hurricane Sandy, it did cause the flooding in Manhattan and nearby coastal areas.
In many places around the world, like Miami, Florida, and Hampton Roads, Virginia, subsidence is a severe problem that makes the incremental increases in ocean level much more damaging to the local infrastructure.
We can't be certain, in many cases, how much an event is affected by global warming. In the case of the recently discovered sinkhole-like holes in Siberia, however, we can be fairly certain they were caused by global warming.
In the first place, the phenomenon of holes in permafrost is unprecedented in the historical record. This phenomenon is something new, just as global climate change is new. In the second place, global climate change theory has predicted the melting of permafrost. We didn't know how it would happen until now. We supposed that the permafrost layer, which consists of undecayed vegetation that has been frozen by perpetual frost, would slowly melt and gradually release its carbon dioxide to the atmosphere. Now it appears that another, much more disturbing process may be underway.
The Siberian holes appear to have been caused by eruptions of methane gas bubbles, although an unknown amount of carbon dioxide was also released. Pound for pound, the effect of methane on global warming is 20 times as much as carbon dioxide. It appears that melting permafrost will release large amounts of carbon dioxide and methane. An estimated amount of 300 billion tons of carbon will be released by melting permafrost, about 2/3 of all the carbon released into the atmosphere since the beginning of the industrial revolution.
That sounds dangerous, though it could be spread out over the next 200 years. The effects of methane alone are impossible to predict because we don't know how much methane is trapped in the permafrost layers. What we do know is that huge bubbles of methane--the hole in Siberia is 200 feet in diameter--can burst into the atmosphere. According to this article at realclimate.org, the potential for temperature rise from methane is catastrophically large.
I have been called a global warming alarmist. This latest news is the most alarming yet.