conversations.from: human
conversations.value: What could be a title for a story about Polar, Cambridge, Professor with the genre: Science & Math, Earth Sciences?
conversations.from: assistant
conversations.value: A title for this story could be 'A Farewell to Ice'
conversations.from: human
conversations.value: Give me the first four paragraphs for this story.
conversations.from: assistant
conversations.value: A Farewell to Ice
  Methane is exceptionally powerful as a greenhouse gas. As I said in Chapter 5, it is 23 or 100 (depending how you calculate it) times as powerful per molecule as CO2 in its warming potential. Arctic offshore emissions may well be the main cause for global atmospheric methane levels starting to rise again in 2008, after stabilizing about the year 2000 (the other likely candidate, leakage from fracking, did not begin until more recently). How much methane is waiting to be emitted in this way, and when will it emerge? What will this do to the climate? We expect that it will further speed up sea ice retreat, reduce the reflection of solar energy and hasten sea level rise as the Greenland ice sheet melt accelerates. But the ramifications of vanishing ice will also be felt far from the poles.
  With two colleagues, Gail Whiteman and Chris Hope, I have modelled what a 50 Gt methane release over ten years would do to climate, both in terms of temperature and cost. Let us remember that, although this is a huge and seemingly impossible quantity of gas to let loose on the world (our total annual release of CO2 is only 35 Gt), it is still less than 10 per cent of the total volume of methane believed to be locked into the East Siberian Sea sediments. To quantify the effects of a major Arctic methane pulse on the global economy, we used the PAGE09 integrated assessment model, which allows the extra emissions to be traced through to changes in sea level, regional temperatures, and regional and global impacts, such as flooding, health and extreme weather, taking account of uncertainty. PAGE09 calculates the amount by which the Net Present Value (NPV) of impacts, aggregated between now and 2200, increases if one more tonne of CO2 is emitted, or decreases if one less tonne is emitted – effectively, the social cost of CO2. PAGE09 is the most recent version of the PAGE model, developed by Chris Hope at the Judge Institute in Cambridge and used by the Government's Stern Review of the Economics of Climate Change to calculate the impacts of climate change. All results are based on 10,000 runs of the model, which allows a full picture of the risks to be built up in order to work out uncertainties.
  We tested two standard emissions scenarios. First was the 'business as usual' scenario, where it is assumed that the world carries on following its present course with increasing emissions of carbon dioxide and other greenhouse gases year on year without any mitigating actions. Secondly we ran a 'low emissions' case, with a 50 per cent chance of keeping the rise in global mean temperatures below 2°C (the '2016r5low' scenario from the UK Meteorological Office). In each case, we superposed a decade-long pulse of 50 Gt of methane released into the atmosphere between 2015 and 2025. We also explored the impacts of later, longer lasting or smaller pulses of methane.
  The extra temperature rise due to the methane by 2040 is 0.6°C, a substantial extra contribution (fig. 9.1). This would be a catastrophe for mankind, partly because it is so quick. It would speed up all the other global warming effects and there would be nothing that we could do to shut off the methane except for cooling the water column (i.e. bringing back the sea ice), which is exceedingly difficult to envisage. Such a methane pulse would bring forward by fifteen to thirty-five years the date at which the global mean temperature rise exceeds 2°C above pre-industrial levels – to 2035 for the 'business as usual' scenario or 2040 for the low emissions scenario. Note how rapidly the methane generates its climatic effect, because, although the peak of 0.6°C is reached twenty-five years after emissions begin, a rise of 0.3–0.4°C occurs within a very few years.
conversations.from: human
conversations.value: Give me five more paragraphs.
conversations.from: assistant
conversations.value: We know from passive microwave instruments on satellites that Antarctic sea ice is advancing overall. This is occurring despite the fact that at least one part of the Antarctic – the Antarctic Peninsula – is warming very fast, and that this led in 2002 to a spectacular event – the collapse of the Larsen B ice shelf on the east side of the Peninsula – in which an area of 3,250 km2 of ice shelf, 200 metres or more thick, broke up into an army of icebergs which then proceeded to drift away, leaving islands and coastline accessible to shipping for the first time in recorded history.
  Why, then, is Antarctic sea ice advancing in the face of a warming climate and the loss of ice shelf area? To answer that question we need to understand how Antarctic sea ice differs from Arctic ice. Of course, Antarctica differs from the Arctic in that the Arctic is made up of ocean surrounded by land, while the Antarctic is a huge land mass at the Pole surrounded by a vast ocean. (Interestingly, the size and shape of the Arctic Ocean and the Antarctic continent are very similar.) Wind patterns and ocean currents tend to isolate Antarctica from global weather patterns, so it can exhibit trends which are uncoupled from those of the Arctic.
  At greater distances inside the ice edge, and now acquiring some protection from waves because of wave energy loss at the edge, the pancakes begin to freeze together in groups; but during our winter experiment in 1986 the wave field was found to be powerful enough to prevent overall freezing until a penetration of some 270 km was reached. Here the pancakes coalesced to form first large floes, then finally a continuous sheet of first-year ice. At this point, with the open water surface cut off, the growth rate dropped to a very low level (estimated at 0.4 cm per day) and the ultimate thickness reached by first-year ice was only a few centimetres more than had been attained when the pancakes consolidated.
  The rafted bottom of consolidated pancake ice provides a large surface area per unit area of sea surface, providing an excellent substrate for algal growth and a refuge for krill. The thin ice permits plenty of light to penetrate, allowing phytoplankton to photosynthesize and live on the underside of the ice. The result is a fertile winter ice ecosystem, which is thought to contribute about 30 per cent of the total biological production of the Southern Ocean.
  Even after another thirty years not many ships have worked in the Antarctic pack ice in midwinter. The Alfred Wegener Institute ran a Winter Weddell Gyre Study in 1989, in which I participated, and there were more recent experiments in the Weddell Sea where the ship worked in conjunction with an ice camp – Ice Station Weddell-1 in 1992 and ISPOL (Ice Station POLarstern) in 2004–5. We do not yet have enough evidence to be sure of whether the frazil-pancake sequence of ice growth is followed around the entire periphery of the Antarctic, but, if it is, then the area occupied by Antarctic pancake ice in early winter could be as great as 6 million km2, making it an important yet seldom-seen component of the Earth's surface. It is quite extraordinary that this amazing landscape of heaving white pancakes should occupy such a vast area yet should be so little known. Probably fewer than a thousand people have seen it.
conversations.from: human
conversations.value: Give me the last paragraph.
conversations.from: assistant
conversations.value: Allen Lane is part of the Penguin Random House group of companies whose addresses can be found at global.penguinrandomhouse.com