Tag: sea ice

Tipping and other points

During the Copenhagen kerfuffle a lot of interesting stuff hit the web: here’s something that deserves a bit more air – a Proceedings of the National Academy of Science (PNAS) special issue on tipping elements in the earth system, edited by John Schellnhuber, the director of the Potsdam Institute for Climate Impact Research in Germany.

Tipping elements (or points, as Malcolm Gladwell would have them) are changes that once started take on a life of their own, and can’t easily be returned to their original state. In the climate system that might be the rapid loss of an ice sheet in a few decades or hundreds of years, while regrowing it might take many thousands. The PNAS special issue deals with nine: dust production in the Bodélé Depression in Chad, ENSO, Arctic sea ice and ice sheets, the Atlantic Meridional Overturning Circulation, deep ocean hydrates (not shallow sea bed, Siberian methane) — David Archer dubs them a “slow tipping point”, the Amazon rainforest (no “Amazongate” here, just a confirmation that concern is justified), monsoons, oceans, and policy responses to the climate challenge. And the best thing is that all the articles are available online, free (click on the link above). Schellnhuber contributes an introduction, and the Potsdam press release also provides a good overview. For some introductory thoughts, check out Tim Lenton’s discussion here.

Another recent example of a real tipping point is the Pine Island Glacier in West Antarctica. Recent modelling suggests that the glacier’s grounding line retreated beyond a ridge in 1996, and is now free to retreat by several hundred kilometres inland. This could happen in a hundred years and result in the loss of half of the ice in the glacier — enough to raise sea level by 24cm. New Scientist reports:

Observations already show that the model severely underestimates the rate at which PIG’s grounding line is retreating, says Katz. “Ours is a simple model of an ice sheet that neglects some important physics,” says Katz. “The take-home message is that we should be concerned about tipping points in West Antarctica and we should do a lot more work to investigate,” he says.

Amen to that.

Oops, he did it again

It pays to beware of leaving hostages to fortune: saying or doing something that might cause you some embarrassment in the future. There’s a very fine example in this recent blog post by Ian Wishart, titled “Top 10 global warming myths exposed“. It takes the form of a piece Wishart has submitted to the Coromandel Chronicle, taking exception to a column by Thomas Everth [PDF]. He begins:

In a blatant effort to mislead and scare your readers, Green blogger Thomas Everth makes more errors in the first 200 words of his recent global warming diatribe than I have made in my last three books totalling around 400,000 words.

As hostages go, that’s pretty impressive. Wishart proceeds to find fault with ten of Everth’s opening points, but does he make a few mistakes of his own in the process? I’m going to take a long, hard look: is that hostage feeling lucky?

Continue reading “Oops, he did it again”

More than a number

[youtube]DLViKhITbrA[/youtube]

If you want to know what’s happening on a stockmarket, the first place to look is at the relevant index — the Footsie (FTSE) for the London Stock Exchange, or the Dow Jones for Wall Street. Those indices aggregate all the price movements over a day into one handy number, to give a quick overview of how the market’s behaving. Now a group of scientists working for the International Geosphere-Biosphere Programme (IGBP) have compiled a Climate Change Index (CCI) to provide the same service for the evidence of climate change. The CCI was launched in Copenhagen yesterday. The video above describes the approach they’ve used, and the “ladder” graphic below shows how the CCI has moved over the last 30 years:

CCI_steps_bigger.jpg

The CCI tracks changes in global temperature, atmospheric CO2, Arctic sea ice, and sea level. An increase in the CCI shows a move away from a stable climate. Over the last 30 years the cumulative shift has been 574 points — in the wrong direction. The IGBP team point out that the CCI responds to global cooling events such as the Pinatubo and El Chichon eruptions, but they are also looking at adding other indicators to the index including land-use, fisheries exploitation, population, fire and extreme events. They are planning to update the index every year, and to backdate it to periods before 1980.

[The Drifters]

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.

Continue reading “Marvellous distempered: the Copenhagen diagnosis”