The Disappearing Hiatus

This has been known behind the scenes for a while, but the publication is useful. It again demonstrates that the scientific literature is performing a very unusual function in the climate policy arena. The very clear accessible presentation of the work in this video is enormously helpful as well.

I think another thing to consider is this. This demonstrates is how very un-robust the “slowdown” is. It did not take much of a correction to eliminate the trend.

Indeed, the conclusions allude to this:

While short term trends are generally treated with a suitable level of caution by specialists in the field, they feature significantly in the public discourse on climate change.

There’s another aspect to this, though, and it may be a bigger deal than might at first be apparent. It adds up to a pretty scary situation.

That’s because the “slowdown” or “hiatus” has also had a number of alternative explanations. Decreased solar activity. Increased volcanic activity. A prevalence of cool-phase El Nino oscillations. Increase in aerosol loading from rapid and dirty Chinese industrial expansion. Heat export to deeper ocean layers.

To be sure, we are somewhat at risk of post hoc reasoning here. If there had been no sign of a “hiatus”, it is likely that less effort would have gone into explaining it! But all of these explanations appear individually to be sound, and with the possible exception of the last, likely to be reversed at any time. What that would mean is that in reality the underlying rate of warming is still accelerating. Ouch.

Figure 8(b) on the Right

Screen shot 2013-09-29 at 1.21.09 PM

I’ve just had my first look over the first and most important piece of IPCC AR5. I think an exposition for the previously inattentive is in order, but that will take some time. At Planet3.0, we mostly leave the fast news to others.

As someone who was fairly well steeped in the community a decade ago, the image which most struck me as novel was the right half of figure 8(b), which shows increased detail of the prognosed precipitation anomaly in the 2081-2100 period under a high emissions scenario.

It’s a nice, high-information figure.

The orange colors indicate drying, and the blues and greens, moistening (in percentage change in annual precipitation, ranging in 10% bands from over -30% to over +50%. (That is (-30%, … -20%), (-20%, … -10%), … (+50%, … +60%] )

The stripes indicate where the change is small compared to variability and/or the sign is disputed among models used. The dots (“stipples”) indicate where the change is not small and 90% of the model runs agree. The extreme wetting outside the equatorial convergence zone occurs in a couple of very dry places and may just be a sort of noise. In any case those areas are sparsely settled.

The most salient feature over populated areas is the extraordinary drying out of the Mediterranean.