By now pretty much everybody understands the "greenhouse effect." Greenhouse gases, primarily CO2 and methane, released into the atmosphere trap solar energy just like a greenhouse and the Earth gets hotter.
There are other components to global warming. The loss of Arctic sea ice is the most obvious. The white reflective ice and snow melts exposing the dark ocean waters beneath. Dark water absorbs more solar energy than ice. The Arctic Ocean then warms which warms the atmosphere immediately above it.
Now scientists warn that another heating component is about to come into the mix, the IPO. That's the acronym for Inter-decadal Pacific Oscillation. We don't tend to think of the vast Pacific Ocean as a heat repository yet that's what it is.
For a decade or two, the Pacific may absorb atmospheric heat and, due to winds and currents, it takes that heat into the ocean depths. The first law of thermodynamics provides that energy remains a constant and, while it can be changed from one form to another, energy can neither be created nor destroyed. In other words, atmospheric heat has been absorbed to become oceanic heat, but that heat energy remains and, in this case, it remains in the Pacific depths.
Like El Nino, the IPO goes through phases - negative, neutral, positive, neutral, negative, and so on. The negative phase is when heat is trapped in the depths. The positive phase is when that stored heat rises to the surface and is returned to the atmosphere and that's what seems to be in our immediate future.
[A] paper by Melbourne University researchers, published this week in Geophysical Research Letters, argues the preceding negative phase - lasting from 2000-2014 - may have provided a "temporary buffer" for surface temperature increases and "cushioned the impacts of global warming on extreme events, such as heatwaves".
"A turnaround of the IPO to its positive phase could initiate a period of accelerated warming over the next one or two decades," Ben Henley and Andrew King state. "This would likely lead to the Paris target of 1.5 degrees (warming since pre-industrial times) being surpassed within the next decade."
And so, while the Arctic continues to warm, releasing as it does ever more methane and CO2 into the atmosphere; and as the greenhouse gas concentrations continue to grow from our consumption of fossil fuels; we're also going to be hit by the release of heat stored in the depths of the Pacific Ocean.