As climate science continues to mature, scenarios also improve. Recently, efforts have been made to fold current and expected future conditions into climate models, making them more useful as forecasting tools, extending their original purpose to answer hypothetical questions such as, over hundreds of years, the likely impact of elevated atmospheric GHGs such as CO2 and methane.
These latest efforts seek to determine likely decadal changes, to assist with short term planning.
When the forecasts indicate potential cooling based on these conditions which are completely independent of GHG levels, the concern is that such a forecast will fool the uneducated into believing that AGW is either over or over-stated.
Of course, the forecasts indicate no such thing. They simply indicate that short term variability can and does mask long term change. We have seen this many times before. Refer to any graph of long term temperature variation and you will find multiple occurrences of short term cooling, lasting 5 years or longer. The short term trend is always absorbed into thelonger term trend, which is a warming trend.
Here we are again: forecasters believe that N.A. and Europe may see periods of cooling over the next decade as PDO sorts itself out. This says nothing about the overall trend of the planet, which may still warm overall during this period. It is also only a forecast, and it remains to be seen how well the PDO "competes" with AGW.
What is clear is this: the concerns are well founded. Denialism has already lept at the perceived opportunity to dent public awareness of the reality that short term variability tells us nothing about long term trends, and that natural processes do continue to unfold, even in a warming world.
We still had winter, for example. Some people don't understand how we can have AGW and also have winter. They experience variable weather and begin to question what they've been led to believe.
Of course, part of the problem is that some people have taken the information presented and drawn the conclusion that AGW should reveal itself in an easily identifiable and predictable way. AGW doesn't care what we want. AGW unfolds according to its own reality, which is that there will be tremendous disruption of the world climate system, and while the overall temperature of the planet must rise due to the radiative imbalance, nature will find ways to deal with this warming, some of which may lead to periods of cooling in certain regions.
The relentless increase in GHGs must eventually prevail, even over such occurrences as el nino and PDO. Those who cling to the belief that periods of cooling somehow contradict AGW, are hiding from scientific probability.