Antarctic sea ice: The end of the trend?

west antarctic sea iceUnusual things are happening to Antarctic sea ice extent. We are about a month away from the traditional time of maximum extent (around 20 September), and each year for the last six years, total sea ice extent around the Antarctic has been above normal. The last three years have been record-breaking, with 2014 seeing the 20 million square kilometre threshold exceeded for the first time since satellite records began in 1979 (Figure 1). But this year, sea ice growth stalled in early August and is currently going nowhere. For the first winter since 2008, total Antarctic sea ice extent is below normal (Figure 2).

ASIExtentanom201409 Figure 1: September Antarctic sea ice extent, percent difference from the 1981-2010 normal.

Antarcticseaice20150819 Figure 2: Antarctic sea ice extent in 2015 (blue line). The dashed line shows 2014 extent, the gray line the 1981-2010 average extent and the shading represents the two standard deviation spread about the average.

What’s more, the pattern of sea ice change this winter is the opposite of the trend pattern we’ve seen over the past few decades towards more ice around the Ross Sea and less ice near the Antarctic Peninsula ((Turner, J., J. C. Comiso, G. J. Marshall, T. A. Lachlan-Cope, T. Bracegirdle, T. Maksym, M. P. Meredith, Z. Wang, and A. Orr, 2009: Non-annular atmospheric circulation change induced by stratospheric ozone depletion and its role in the recent increase of Antarctic sea ice extent. Geophys. Res. Lett., 36, L08502, doi:08510.01029/02009GL037524.)). This year, near the Antarctic Peninsula, we have more ice than normal, and less than normal north of the Ross Sea and across parts of the Indian Ocean (Figure 3). A real turn-around.

ASI20150816extentmap Figure3: Antarctic sea ice coverage for 16 August 2015 (white). The thin solid line shows the 1981-2010 average sea ice edge for this date.

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Coal, climate change, and the New Zealand economy: winners, losers, and long-term users

Cross-posted from Coal Action Network Aotearoa

As the country reeled with the news last week that Solid Energy had gone into administration with a $300m debt, another event was happening in the Pacific that puts the debate in a context that it too seldom receives in New Zealand.

Sign on Kiribati's island of Tarawa. Photo: flickr
Sign on Kiribati’s island of Tarawa. Photo: flickr

On Thursday, Kiribati Prime Minister Anote Tong wrote to world leaders calling for a moratorium on new coalmines.

“Kiribati, as a nation faced with a very uncertain future, is calling for a global moratorium on new coal mines. lt would be one positive step towards our collective global action against climate change and it is my sincere hope that you and your people would add your positive support in this endeavour,” he wrote.

“The construction of each new coal mine undermines the spirit and intent of any agreement we may reach, particularly in the upcoming COP 21 in Paris, whilst stopping new coal mine constructions NOW will make any agreement reached in Paris truly historical.”

UK Economist Sir Nicholas Stern agreed: “The use of coal is simply bad economics, unless one refuses to count as a cost the damages and deaths now and in the future from air pollution and climate change,” he told Reuters (Stern’s full statement here).

In June, Pope Francis said in his encyclical that the use of “highly polluting fossil fuels needs to be progressively replaced without delay.”

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What’s Beef? (The Rap Guide To Climate Chaos)


A little something for the weekend courtesy of Baba Brinkman — the Canadian “rap artist, writer, actor, and tree planter” — from his Edinburgh Festival show The Rap Guide To Climate Chaos. Familiar themes, I think you’ll find, over a blistering beat (as the young folks may say). See also Brinkman’s Rap Guide to Evolution, and in particular the marvellous Darwin Day.

Postcards from La La Land: the Cnut conundrum

New Zealand’s merry little band of climate deniers are turning out to be a right bunch of Cnuts. Sea level rise and its implications for Christchurch and the wider world have been making news in recent weeks — as have new projections of rapid sea level rise over the remainder of this century. So what does a good climate denier do? To stay faithful to their core belief — that climate change isn’t happening, or isn’t going to be bad — they have to argue against policies designed to deal with its impacts, as well as those intended to cut carbon emissions. Sea level rise? Like Cnut, they line themselves up against the waves.

I’ve blogged many times on the challenge sea level rise poses for post-quake Christchurch. The 2011 quakes caused large parts of the city to drop by up to half a metre — effectively delivering decades of sea level rise in a matter of minutes. For some areas of the city tidal and run-off flooding are now commonplace.

The current debate on sea level issues has been prompted by the city council’s long term planning process — which recommends ((Based on a revised report (pdf) developed from consultants Tonkin & Taylor’s 2014 work.)) that development should be restricted in areas where future sea level rise is expected to cause problems. Not surprisingly, this has some owners of coastal properties concerned that they will lose out. The council has also looked at the idea of building a tidal barrier across the Avon-Heathcote estuary to protect the city.

Local politics and property owner self-interest is bumping into the harsh realities of climate change, leading to a wide variety of responses — including “it isn’t happening”.

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A tale of two hemispheres

Jim RenwickAt the end of June, Professor Jim Renwick of Victoria University gave his inaugural lecture. As you might expect of a climate scientist, it concerns what we know about the climate system and where we’re heading. He pulls no punches. Jim has been kind enough to put together a text version of the lecture for Hot Topic: it follows. You can watch the full lecture, with accompanying slides, on the video embedded at the end of the post.

We live in a golden age of earth observation. With a few clicks of a mouse on a web browser, any of us can see the state of the global ocean surface, the current condition of the Greenland ice sheet, how much rain is falling in the tropics today, and on and on. Plus, the International Space Station (ISS), and a series of satellites such as MODIS give us wonderful images of our home planet. The climate science community can tell, with unprecedented coverage and timeliness, just what is going on in the climate system. It is a great time to be a climate researcher, but also a worrying time, in both cases because we can see exactly what is changing.

One thing the ISS pictures emphasise is just how thin the atmosphere is, a thin blue layer between the solid earth and the blackness of space. Not only is this life-supporting envelope very thin, some of the key gases in the atmosphere are there in only trace amounts, so we can change the properties of the atmosphere easily, by targeting the right gases. The discovery of the ozone hole 30 years ago brought this home with a bang. And we’ve found that build-up of carbon dioxide (CO2) in the atmosphere can have a profound effect on the climate system, right down to the bottom of the oceans.

Carbon dioxide is important because it’s a crucial control on the surface temperature of the earth. It is very good at absorbing heat (infrared radiation) welling up from the earth, then re-radiating both up and down, in the process warming the earth’s surface. The effect is very like a blanket put on a bed – what’s under the blanket warms up. More CO2 is like putting another blanket on the bed and less is like taking away a blanket. No CO2 and the earth freezes – temperatures like we had in the South Island in late June would be the norm everywhere, all the time. While there are several other “greenhouse gases”, carbon dioxide is the most important since it stays in the atmosphere so long, hundreds to thousands of years.
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