Antarctic ice levels - no controversy!

You may have seen the Daily Mail’s seemingly gleeful reporting of record ice levels across Antarctica, with implications about climate change.   

NASA’s Earth Observatory does indeed show a new largest extent of ice across the southern polar region, as the austral winter starts to fade. You’ll be expecting me to say that this is not contrary to expectations of climate change, and you’re right. The reasons are fascinating, and underline how it’s important to try to understand things properly, instead of jumping to conclusions (which might leave you stranded like Milo in Norton Juster’s classic children’s storyThe Phantom Tollbooth). 

The fundamental difference between the Arctic and Antarctic weather systems were brilliantly explained by Dr Colin Summerhayes of the Scott Polar Research Institute at our Climate Change: Biodiversity and People at the Front Line conference last year, and summarised in the meeting’s report.

The Arctic is heating up because it is open to incoming warmth from surrounding areas. This includes both warm water brought in from the Atlantic through the Fram Strait between Svalbard and Greenland, and from the Pacific through the Bering Strait; and warm air coming in from all directions.

Antarctica in contrast, is protected from warm air intrusion from lower latitudes by circumpolar winds. These have been strengthened by the increased pole-to-equator pressure gradient, which has steepened due to global warming. In addition, the ozone hole has strengthened surface winds by a further 15% in the autumn. As a result, East Antarctica is cooling, and sea ice is increasing by 1% per decade. The changing patterns of air pressure have deepened the low pressure cell in the Amundsen Sea, allowing warm air to be drawn in from the north along the Antarctic Peninsula, causing the temperature to increase there by 0.53°C per decade since the 1950s. Winter temperatures on the western side of the Peninsula have increased by 1.03°C per decade, and annual fluctuations correlate with the loss of around one-third of the sea ice over the last 50 years, when sea temperatures have increased between 0.5°C and 1°C. There is growing evidence of polar amplification in Antarctica as well as in the north.

This difference is also clearly reflected in the IPCC’s projections of climate change. You can see that for the next couple of decades at least, Antarctica has little expected warming, as low as any other land area.  Projections for the Arctic in contrast, are at the top end of the scale.

One of my favourite quotes is from Charles Elton ‘unfortunately, nature cannot be understood by pretending that it is simple’.  Finding out how things really work can be difficult, but is always interesting. And it's essential to avoid the dangers of the ‘obvious’ answer or conclusion, likely to lead us down the wrong path – along which I hope the Mail has not set its readers.