A series of articles in this week's Nature shows one of the possible consequences of global warming: a tropical Arctic. Paleoclimate studies show that 55 million years ago, when the global climate was, on average, 6 degrees warmer than it is at present, the area that is now the ice-bound Arctic ocean basked in a balmy tropical climate similar to that of Florida. This is far greater warming than current climate models predict, and suggests that we're missing an important feedback mechanism which magnifies the effects of increased CO2 concentration. Needless to say, this isn't good news. The IPCC is currently predicting a midrange figure of three degrees of warming by 2100, which as VUW geologist Peter Barret recently pointed out, is quite dangerous enough. But if we've missed something, then we may be in for a far warmer world than expected, with devastating consequences for both people and the environment.
I presume that part of the reason for the Antarctic climate being so warm 55 million years ago was that the continent was not then in the vicinity of the south pole.
ReplyDeleteThe continents drift around the surface of the earth, slowly on a human timescale but it builds up over millions of years.
Having done a bit of research I see I am wrong. Antarctica was in about the same place 55 million years ago as it is today.
ReplyDeleteHowever I note that Australia had broken away from Antarctica and was moving rapidly northwards.
There seems to be a long term pattern of the world alternating between "cold house" conditions like today and "hot house" conditions like the age of the dinosaurs.
Gary: for a start, it would help if you were looing at the right end of the planet.
ReplyDeleteSecondly, yes, there are long-term fluctuations in the earth's climate, following various things like the Milankovitch cycles. There's general agreement among scientists (and I mean actual scientists, not the kooks and hacks in the denier camp) that that is not what is going on now. As the Barret article shows, the current warming is very much against the trend.
From what I understand, Australia joined to Antarctica meant that there was no circum-polar current circulating in the Southern Ocean; the current acts as an enormous refrigerator coil to the world's climate, hence affecting things in the Arctic (among other areas).
ReplyDeleteat 55 mya, Aussie was still joined to Antarctica by the Tasmanian isthmus?
Mea culpa. I have retired from the paleo-climatology business and I will take up reading what I am replying to.
ReplyDelete