Tag: Antarctica

Antarctic science review: greening and melting

The first comprehensive scientific review of our understanding of Antarctic climate and the way that it’s changing was published in the UK earlier this week [ScienceDaily]. The Antarctic Climate Change and the Environment report (a free download), prepared by the Scientific Committee on Antarctic Research (SCAR), points to ten key findings [PDF]:

  • For the last 30 years, the ozone hole has shielded the bulk of the Antarctic from the effects of “global warming”
  • The Southern Ocean is warming – the ecosystem will change
  • There has been a rapid expansion of plant communities across the Antarctic Peninsula
  • Parts of the Antarctic are losing ice at a rapid rate
  • Sea ice has increased in extent over the last 30 years as a result of the ozone hole
  • Paleoclimate studies in Antarctica show that the current shock to global climate is unusual
  • Marine ecosystem components, such as krill and penguins, linked to the sea ice show a clear response to climate change
  • Assuming a doubling of greenhouse gas concentrations over the next century, Antarctica is expected to warm by around 3ºC
  • West Antarctica could make a major contribution to sea level rise over the next century
  • Improved representation of polar processes is needed in models to produce better predictions

The full report weighs in at 526 pages [20MB PDF] and is a superb overview of the state of our knowledge. It’s not an easy read, but in the manner of the IPCC reports is comprehensive and carefully referenced, with lots of illustrations of what’s going on. Recommended. The BBC has good coverage of the sea level implications, Stuff picks up on the “greening” aspect, and the Guardian notes that warming will accelerate as the ozone hole heals.

Marvellous distempered: the Copenhagen diagnosis

The Copenhagen climate conference (COP15) opens its doors in a little under two weeks. To update participants on the science of climate a new assessment report, The Copenhagen Diagnosis, was released yesterday, and it makes grim reading. Designed to inform “a target readership of policy-makers, stakeholders, the media and the broader public” about the evidence that’s emerged since the 2005 cut-off for the IPCC’s Fourth Report, it is especially strong on the accumulating signs of climate change as it happens.

Evidence of melting of the Greenland and Antarctic ice sheets supports a revision of the expected sea level rise by the end of the century: it “may well exceed” a metre. The rapid sea ice loss in the Arctic in recent years highlights the risks of methane releases from permafrost, but the most direct message is that with global carbon emissions surging up to and beyond the highest of the IPCC’s scenarios, and with pretty strict limits on the amount of carbon we can add to the atmosphere and stay under a 2ºC rise, we need to start cutting emissions soon.

Here’s what the emissions growth looks like:

CopCO2emissions.jpg

And here’s what we need to do to stay under 2ºC:

CopDiagtargets.jpg

It’s a simple enough message. The longer we leave it before starting to cut emissions, the steeper the cuts will need to be. And there’s an obvious corollary: steep cuts will be more expensive. Inaction now means more cost in the future. Where does that leave any government promising to “balance the economy and the environment”?

Below the fold: the full executive summary.

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Deep time, deep water

The last time CO2 hit a sustained level of 400 ppm 15-20 million years ago global average temperatures were 3 – 6ºC warmer than now, and sea level was 25 to 40 m higher, according to research released last week. That’s bad news, because the target for current international negotiations to find a successor to Kyoto is 450 ppm. The finding also provides support for James Hansen’s view that 350 ppm is the maximum “safe level” for CO2 if we want to inhabit a planet with ice at both poles.

Meanwhile, analysis of the Andrill core has discovered a “remarkably warm” period in Antarctica that occurred abruptly 15.7 million years ago, when the McMurdo Sound region could have had January air temperatures of 10ºC and sea temps up to 11.5ºC, according to a new paper in Geology.

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More than a metre

Sea level will rise by more than a metre by 2100 according to the authors of the third chapter in the World Wide Fund for Nature’s new Arctic report, introduced by Gareth a few days ago. Eric Rignot, one of the two authors of the chapter, is principal scientist for the Radar Science and Engineering Section at NASA’s Jet Propulsion Laboratory, Pasadena, Calif.  The other author, Anny Cazenave, is an internationally renowned research scientist from France’s national centre for space studies.

The value of the chapter is that it draws together, authoritatively and coherently, the evidence that points to considerably more sea-level rise over this century than projected in the 2007 IPCC Fourth Report (AR4). Happily politicians are taking IPCC reports much more seriously than in the past, but they should not rest on them.  Their responsibility is to be up to date with what the science is saying now. The WWF report assesses the most recent science, and finds that the impacts of warming will be more severe than indicated by the IPCC.

What follows is a summary of the main points made by the chapter.

Continue reading “More than a metre”

The PIG is flying

PIGmap.gif The Pine Island Glacier in West Antarctica is thinning four times faster than 10 years ago, a new study(*) of satellite measurements shows. Since 1994, the central portion of the glacier has thinned by as much as 90 metres, and the ice surface is currently lowering by 16 metres a year. At this rate of thinning, the glacier could disappear in 100 years, instead of the 600 years earlier estimates had suggested. The BBC report includes an excellent video, and focuses on the implications for sea level rise:

One of the authors, Professor Andrew Shepherd of Leeds University, said that the melting from the centre of the glacier would add about 3cm to global sea level.
“But the ice trapped behind it is about 20-30cm of sea level rise and as soon as we destabilise or remove the middle of the glacier we don’t know really know what’s going to happen to the ice behind it,” he told BBC News. “This is unprecedented in this area of Antarctica. We’ve known that it’s been out of balance for some time, but nothing in the natural world is lost at an accelerating exponential rate like this glacier.”

Unlike Greenland, where surface melting adds to losses caused by warming oceans, in West Antarctica it’s thought that warm ocean currents (specifically the Upper Circumpolar Deep Water, which is 3ºC warmer than surface water in the region) are being channelled in under the PIG ice shelf, helped by the large trough the glacier carved in the sea floor during previous glacial maxima. Given concerns about the stability of the West Antarctic ice sheet as the world warms and sea level rises, the words “exponential rate” sound particularly ominous…


(*) Wingham, D.J., D.W. Wallis, and A. Shepherd (2009), Spatial and temporal evolution of Pine Island Glacier thinning, 1995-2006, Geophys. Res. Lett., doi:10.1029/2009GL039126, in press.