NEW YORK (TheStreet) -- A new study may shed some light on one of the most controversial aspects of the current global warming debate. The problem is frequently framed in headlines as a question, "Has Global Warming Stopped?"
The short answer is and always has been "no," it hasn't stopped. It hasn't even slowed down. Sea levels continue to rise inexorably. Arctic Sea ice and Antarctic glacier cover continue their shrinking trends. Weather patterns continue to change dramatically.
But let's back up.
Global surface temperatures have been rising more or less since the outset of the Industrial Revolution. Presumably this rise in temperatures is linked to the correlating rise in CO2 and other heat-trapping gasses in the troposphere, the layer of atmosphere closest to the earth.
However, for reasons scientists haven't been able to fully explain, those surface atmosphere temperatures have flattened out in recent years, beginning about 2001. Skeptics of global warming science love this: It seems to undercut the findings of the scientific mainstream and throw the whole question of long-term global warming into the trash heap. If CO2 emissions were causing global warming, then surface temperatures should continue to rise. Since they haven't, global warming can't be real.
Skeptics have termed this a "pause" or a "hiatus" in global warming. As recently as Feb. 3, in Forbes, this anomaly in the data was being touted as evidence that climate scientists have "oversold" the risks of climate change. Those denialist arguments ignore the larger trend, as I have pointed out in earlier articles. But even while the anomaly in the data may pose no threat to global warming models generally, it's cause remained a mystery.
Recently, in a study published in the most recent issue of Nature Climate Change, a scientific peer-review journal, a team of scientists led by Australian Matt England found that warmer surface water in the Pacific is being pushed westward by equatorial trade winds that are much stronger than expected. As the warmed surface water hits the western continental shelf it is driven downward into the lower depths. The action of the trade winds effectively cools the observable surface temperature by mixing the heat into the deep water.
"The oceans have this amazing capacity to suck up heat," England said in a phone interview from his home in Australia Wednesday (very early Thursday morning according to his clock). "The ocean absorbs 90% of the heat of the climate system, so if you're looking for global warming that's where you have to look."
While overall global warming predictions are panning out accurately, "I think we've discovered that the models are coming up short in terms of decadal variability," England said.
According to the study, surface temperatures could remain flat as long as the anomalous trade winds last, but that once they cease, the rise in surface temperatures will resume. Moreover, the heat currently submerged in Pacific waters will bubble to the surface and accelerate that trend.
"If the winds go back to normal the warming rise can be very rapid," England said. "The projections catch up as if the 'hiatus' never occurred."
The magnitude of the strengthening of trade winds was not considered in earlier climate change models. Plugging that data into existing models, the team of researchers found the current lull in recorded surface temperatures over the last decade suddenly appeared in line with expectations.
In good science, every answer opens the door to new questions. In this case, the next stages of research will address the mystery of what's causing that strengthening in the trade winds.
"The winds are twice as strong as what we would expect," England said.
That difference could easily be driven in part by global warming, he said, but the research isn't there yet to say for certain.
"Bottom line: Half natural and half driven by other changes, possibly climate change," he said.
Scientists aren't entirely sure when the additional strength of the trade winds will weaken, allowing the heat beneath the surface to escape and warm the atmosphere.
"It's virtually impossible to say," England said, while adding that the increase is "definitely temporary."
"Looking in the climate record over the last hundred years, [the trade winds tendency is to] flip every 20 to 25 years," he said. Using that as an estimate puts the timeframe to within about seven years from today.
-- Written by Carlton Wilkinson in New York City