Which is it?
An article today reports on research that the Antarctic iceshelf is expected to disappear relatively soon:
“Last summer sea ice in the North shrank to a record low, a change many attribute to global warming.
But while solar radiation and amounts of greenhouse gases in the atmosphere are similar at the poles, to date the regions have responded differently, with little change in the South, explained oceanographer James Overland of the National Oceanic and Atmospheric Administration.
What researchers have concluded was happening, was that in the North, global warming and natural variability of climate were reinforcing one another, sending the Arctic into a new state with much less sea ice than in the past.
‘And there is very little chance for the climate to return to the conditions of 20 years ago,’ he added.
On the other hand, Overland explained, the ozone hole in the Antarctic masked conditions there, keeping temperatures low in most of the continent other than the peninsula reaching toward South America.
‘So there is a scientific reason for why we’re not seeing large changes in the Antarctic like we’re seeing in the Arctic,’ he said.
But, Overland added, as the ozone hole recovers in coming years, global warming will begin to affect the South Pole also. “
And then there was an article in the BBC that reported that the climate forecast was for global cooling for the next few years (at least until 2015 or so)
“A new computer model developed by German researchers, reported in the journal Nature, suggests the cooling will counter greenhouse warming.
However, temperatures will again be rising quickly by about 2020, they say. Other climate scientists have welcomed the research, saying it may help societies plan better for the future.
The key to the new prediction is the natural cycle of ocean temperatures called the Atlantic Multidecadal Oscillation (AMO), which is closely related to the warm currents that bring heat from the tropics to the shores of Europe.
The cause of the oscillation is not well understood, but the cycle appears to come round about every 60 to 70 years.
It may partly explain why temperatures rose in the early years of the last century before beginning to cool in the 1940s.”
(NB: this effect would only slow the increase in global warming if the model that predicts if verifies.)
So which is it: global warming or global cooling?
The answer is that the system scientist are trying to understand is extraordinarily complex. And the interrelations in the system between various inputs is not yet well understood. It’s because of this difficulty that I’ve consistently tried to use the term “Climate Change” on this blog rather than global warming. If what we’re seeing happen continues, parts of the globe are going to get warmer, but some areas, like Arizona and northern Europe might well get cooler. That’s why Climate Change is really a better phrase.
The additional question that folks are trying to answer is how much of the change is happening on account of human activities and the changes they bring to the environment. The majority of scientists believe that a significant portion of the change is due to human causes. But not all scientists agree, and even the ones that do agree, don’t agree on the degree. (Of course if there’s any degree of contribution, assuming that the change is bad, stopping our contribution will at least slow the rate of the change. Which may not seem like such a big deal to people who can manage the change by turning up the level of air-conditioning another notch – but it is a big deal to folks who are losing their crops and being forced into chronic hunger as a result.