## Paris’ COP21: Great cheerleading from the diplomats, but … +ENSO is here

This target is, however, extremely demanding. Climate researchers have explored only a few scenarios that limit warming to 1.5 °C. They show that global emissions of greenhouse gases must be between 70% and 95% lower in 2050 than they were in 2010. In the second half of the century, net emissions must become negative, meaning that overall, carbon is removed from the atmosphere. It is still unclear whether this is feasible even in theory: we don’t yet know enough about the limits of negative-emission technologies with respect to, for example, the use of land and water (P. Smith et al. Nature Clim. Change http://doi.org/983; 2015).

The agreement would have been more credible if the ambitious temperature goal were matched by an equally ambitious plan for how to get there by reducing emissions. The stated aim is that global emissions should reach a peak “as soon as possible”, then decline rapidly, before achieving a “balance between anthropogenic emissions by sources and removals by sinks of greenhouse gases in the second half of this century”.

$\vdots$

The Paris agreement is informed by science. There would be no agreement, indeed no process at all, if all countries did not recognize the importance of scientific findings on the causes and consequences of climate change. But the agreement is unlikely to be fair and efficient. The poorest people, who contribute the least to the problem, will still face the worst consequences of climatic changes, with insufficient funding from richer countries to pay for climate adaptation or to deal with loss and damage. The emerging complex of different national, local and sectoral policies and initiatives is a far cry from the uniform price on emissions for which economists have called.

Current national pledges to cut emissions are too weak, and the ramping up too vague, for us to conclude decisively that the Paris agreement will help us to avoid dangerous interference with the climate system. The agreement probably ensures that we can avoid 4 °C of warming, but it is a long way from what we need to limit warming to less than 2 °C. For the Paris agreement to deliver, the pressure is on for countries to ramp up their ambition.

This is excerpted from an editorial in the journal Nature, by Steffen Kallbekken, research director and economist at CICERO, the Center for International Climate and Environmental Research in Oslo, Norway.

Postscript on the Extreme Warmth of November-December 2015

I’m adding this postscript here because popular, meteorological answers to questions regarding recent extreme warmth are somewhat missing the point, in my opinion, and deserve a response. Yet, they don’t deserve a post unto themselves.

El Niño or the positive phase of ENSO is a phenomenon unique to the large Pacific ocean, and it exists primarily because nowhere else on Earth is there such a large stretch of water on the Equator. Essentially, the coriolis forces at this local are zero, so oceanic motions and currents and associated coupling with atmosphere moves east and west. 90% of the excess heat forcing by atmospheric greenhouse gases goes into the ocean:

(Click on image to see larger figure, and use browser Back button to return to blog.)
La Niña, the flip or negative side of ENSO, extracts heat from atmosphere, storing it at depth:

(Click to see animation.)

In years when there is an La Niña, less energy remains in the atmosphere because it is being actively pumped into the ocean. In essence, this energy is getting “banked”. When there is an El Niño, not only is the energy that would be banked not banked, and, so, available in atmosphere, but some of the energy that was banked is now being released. Accordingly, things are warmer than if simply excess atmospheric warming from greenhouse radiative forcing were active, because a bunch of that forcing is now being released.

Accordingly, questions like “How much of this warming is due to El Niño and how much to climate change?” are poorly posed, in my opinion, and attempts to determine attributions by percent to each effect mislead, I think. It’s about energy and its conservation. La Niña may give us a pass from excess warming for a few years, but it builds, and, on the flip side, El Niño restores it. Sure, there’s always been an ENSO, with effects somewhat like the present. But our collective contribution to the atmospheric greenhouse has stored much more energy in oceans, which we are now seeing.

It’s going to get worse, unless we really act, as Dr Steffen Kallbekken indicates.

(Click on image to see larger figure, and use browser Back button to return to blog.)