You may recall the previous post where Basil Copeland and I looked at correlations between HadCRUT global temperature anomaly and sunspot numbers. This is similar, but looks at the Pacific Decadal Oscillation (PDO) and uses the same Hodrick-Prescott (HPT) filter as before on the HadCRUT global temperature anomaly data and the PDO Index.
click for a larger image –
NOTE: the purple line is a monthly warming rate, to get decadal values, multiply by 120
This graphic provides some context to what may be happening with the PDO. In the upper panel we’ve plotted the PDO (in red), a smoothed PDO (in light blue), and our analysis of the bidecadal variation in warming rates.
From the PDO data itself, it is just too soon to be able to tell whether the current cool phase is just one of the shorter cycles, or whether it is the beginning of a longer term cycle like we saw back in the 1950’s and 1960’s. It is tempting, when looking at the warming rate cycles, to believe that we’ve just come out of a 60-66 year “Kerr” climate cycle, and are on the cusp of a cool phase like we see for the 1950’s and 1960’s.
But if you look closely at the end of the purple curve for our warming rate cycle, it seems to be about ready to turn back up. Now we do not want to put too much stock in the end values of a series that has been smoothed with HP filtering. So it could still be on a downward trend.
Then, to make it all the more interesting, we have solar cycle 23 lingering on. Considering that also, confidence is higher that we will continue to see a relative respite in the rate of warming and that we’re not likely to see our warming rate cycle jump back to where it was during solar cycles 22-23. But whether we see a full blown interlude between two strong warming trends, like we saw during the 1950’s and 1960’s, remains to be seen.
In other words, as we saw with Easterbrook’s analysis, we can be reasonably confident in projecting at least no further warming for a while. For that to happen, the purple warming rate curve must not only turn back upwards, it must rise into the region of positive values, and continue to rise for several years. If solar cycle 24 turns out to be a weak solar cycle, and there are historical precedents for cycle length suggesting it is likely to be weak, that probably isn’t happening.
I’ll have more on solar cycles 23 and 24 coming up in the next day or so.
So, in summary; probably no net warming for awhile, and maybe a period of extended cooling as in the mid 20th century. It all depends on whether this current PDO shift is a short term or longer term event such as we saw in the mid 20th century.
This is inline with the article in today’s UK Telegraph, saying:
“Global warming will stop until at least 2015 because of natural variations in the climate, scientists have said. Researchers studying long-term changes in sea temperatures said they now expect a “lull” for up to a decade while natural variations in climate cancel out the increases caused by man-made greenhouse gas emissions.
The average temperature of the sea around Europe and North America is expected to cool slightly over the decade while the tropical Pacific remains unchanged. This would mean that the 0.3°C global average temperature rise which has been predicted for the next decade by the UN’s Intergovernmental Panel on Climate Change may not happen, according to the paper published in the scientific journal Nature.”
There’s a similar article in Yahoo News.
The paper by Keenlyside et al entitled “Advancing decadal-scale climate prediction in the North Atlantic sector” from the Nature website