Yeru
It's the same thing with hurricanes. We have a year in which hurricane strength and numbers is at decades-old lows, and weather != climate. But one big hurricane happens to hit a major city, and all of a sudden "It's all because of global warming!" Hurricane Sandy was the worst example of this, because those who attributed it to AGW seem to have completely forgotten that this is not the first time a hurricane hit New York, nor was it the strongest to do so.
Before I answer the first part let me deal with this.
Hurricanes and typhoons are not just driven by the level of ocean heat but also by wind patterns and moisture content.
Also a hurricane is measured not just by wind velocity but by size and rain intensity.
They are complex beasts but additional ocean surface heat will move a cat 4 to a cat 5 etc.
So there may not be more storms, but there may be more of the more intense types.....and that includes rain intensity.
The most obvious influence on Sandy was not the hurricane itself - New York has had hurricanes before but that the blocking high....related to what is happening with the jetstream currently, steered Sandy inland instead of the normal track out to sea.
In addition the warmer ocean surface kept Sandy growing larger, longer.
All these add up to increased risk for coastal cities and when you add in sea level rise that has sped up in the last decades then if you take the long view as insurance companies must - then you have costly long term risk. No one event is attributable, more frequent or more frequent intense events are a mark of more energy and more moisture in the atmosphere.
So climate drives regional weather.
This extreme cold snap is weather but it is influenced by a warmer Arctic destabilizing the weather patterns.
http://www.noaa.gov/features/02_monitoring/warmarctic.html
This was an occasional phenomena and now has increased in frequency.
When looking a cold snap like this....it's not a trend....it's weather.
WHen looking at entire year of record warmth as Australia has just undergone....then you have a much longer baseline to look at...and they have good records back to 1890s.
One year can be an anomaly as 1998 was....El Nno year ....but when you start stringing along decades of increases including highest temps, highest night time temps ( very significant ) changes in migration times, blooming times, species ranges.....there is an endless list of evidence
and combine that with the rather simple atmospheric physics underlying AGW and the incontrovertible fact that we have boosted C02 from 280 ppm to over 400....the change of theory and evidence is overwhelming.
Now you add in the likes of Exxon head acknowledging climate risk and you should be able to easily get by any doubts about the reality of AGW.
What is really hard to discern is the best path to deal with it, how fast will be the onset, and what will it mean for any given region.
Observation is building up a picture and one prediction was more extreme weather driven by a less stable and warmer atmosphere .....and sure enough that is what we are seeing.
To reassure yourself on the underlying science just follow the links in my signature.
Ask questions here as well and read the science for yourself.
Once past that comfort level then join in looking at the consequences that are in progress and the larger consequences of BAU.
