My favorite chart, End-April volume, not even remarkable. A simple continuation of what looks like a linear trend, past a "plateau" that may have been random variability in hindsight.
This is good, however, it must also be suggested that the 2013 & 2014 'recovery' years were black swan events and are pushing the trend anomalously higher (straighter). If these years effects did not occur and the volume gain during those years was removed then the trend would fall well below the long-term linear trend.
I believe for several reasons that these years events were a statistical outlier over 4 sig.
"Black Swan" seems a bit too extreme. The paleontological evidence seems to indicate a bit of stuttering before the actual climate switch. This is also consistent with how natural systems generally tend to undergo a change of state in General Systems Theory. Most of the time the system tends to choke a few times before flipping to a new state. If you think about it, that is what happens with things like computer networks which are in the process of crashing -- they stutter and then fail.
Jim
what you are saying is true to an extent, however we are not operating within a black box environment. The 1976 and 2014 Gulf of Alaska blocking pattern has a distinct profile that is largely a result of varying upper troposphere aerosol loading. I have been looking at this for a number of years now and the key indicator is that the Global Circulation Models (GCMs) used to model geoengineering (global dimming) show a strong and persistent blocking ridge in this region.
Therefore, while state-change activities are definitely happening, the drivers of specific systemic changes always have physical drivers. It appears that the 2013/2014 cooler summers (and warmer winters in Alaska, drought in California and record snow levels on the east coast) are driven by regional shifts in high-temp process emissions of aerosols (as happened in 1975 when Europe rapidly reduced their emissions but U.S. and Asia emissions were continued).
The 2013 event was similarly produced by reductions in U.S. emissions post 2007 crash but shifting this manufacturing to China who engaged in a command economy overproduction surge in 2013.
Without this knowledge this could appear to be a strengthening of natural variability under a shifting climate regime, but this is a black box analysis of a black swan event.
This video has excellent analysis from people who were not aware of this aerosol driver.