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Climate Science

HadCRUT4 data now available

16 Apr 2012 by Gavin

Just a quick note to point out that the HadCRUT4 data are now fully available for download. Feel free to discuss (or point to) any analyses you’d like to see done in the comments, and perhaps we’ll update this post with the more interesting ones.

Filed Under: Climate Science, Instrumental Record

Arctic Sea Ice Volume: PIOMAS, Prediction, and the Perils of Extrapolation

11 Apr 2012 by group

Guest Commentary by Axel Schweiger, Ron Lindsay, and Cecilia Bitz

We have just passed the annual maximum in Arctic sea ice extent which always occurs sometime in March. Within a month we will reach the annual maximum in Arctic sea ice volume. After that, the sea ice will begin its course towards its annual minimum of both extent and volume in mid-September. This marks the beginning of the ritual of the annual sea ice watch that includes predictions of the extent and rank of this year’s sea ice minimum, as well as discussion about the timing of its eventual demise. One of the inputs into that discussion is the “PIOMAS” ice-ocean model output of ice volume – and in particular, some high-profile extrapolations. This is worth looking at in some detail.

[Read more…] about Arctic Sea Ice Volume: PIOMAS, Prediction, and the Perils of Extrapolation

Filed Under: Arctic and Antarctic, Climate modelling, Climate Science

Evaluating a 1981 temperature projection

2 Apr 2012 by group

Guest commentary from Geert Jan van Oldenborgh and Rein Haarsma, KNMI

Sometimes it helps to take a step back from the everyday pressures of research (falling ill helps). It was in this way we stumbled across Hansen et al (1981) (pdf). In 1981 the first author of this post was in his first year at university and the other just entered the KNMI after finishing his masters. Global warming was not yet an issue at the KNMI where the focus was much more on climate variability, which explains why the article of Hansen et al. was unnoticed at that time by the second author. It turns out to be a very interesting read.
[Read more…] about Evaluating a 1981 temperature projection

References

  1. J. Hansen, D. Johnson, A. Lacis, S. Lebedeff, P. Lee, D. Rind, and G. Russell, "Climate Impact of Increasing Atmospheric Carbon Dioxide", Science, vol. 213, pp. 957-966, 1981. http://dx.doi.org/10.1126/science.213.4511.957

Filed Under: Climate modelling, Climate Science, Greenhouse gases, Instrumental Record

Unforced variations: April 2012

2 Apr 2012 by group

This month’s open thread – a day late for obvious reasons… Have at it.

Filed Under: Climate Science, Open thread

‘Wrong sign paradox’ finally resolved?

1 Apr 2012 by Stefan

A group of colleagues has all but solved one of the greatest remaining puzzles in climate science. But the story is not one of scientific triumph – rather, it is so embarrassing that we had controversial discussions in our group whether to break this to a wider public at all.

The puzzle is known amongst climatologists as the “wrong sign paradox” – our regular readers will probably have heard about it. Put simply, it is about the fact that a whole number of things in climate science would fit very nicely together, if only the sign were reversed. If only plus were minus. [Read more…] about ‘Wrong sign paradox’ finally resolved?

Filed Under: Climate Science

The IPCC SREX: the report is finally out.

29 Mar 2012 by rasmus

Some of us have been waiting quite a while now, especially since the ‘road tour’ meant to present the Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation starting in Oslo on January 24th this year. The summary for policymakers (SPM) was released already in 18 November 2011 (Kampala) and now the report is finally available (link).

[Read more…] about The IPCC SREX: the report is finally out.

Filed Under: Climate Science, RC Forum, Reporting on climate, Reviews, statistics

Extremely hot

26 Mar 2012 by Stefan

By Stefan Rahmstorf and Dim Coumou

One claim frequently heard regarding extreme heat waves goes something like this: ”Since this heat wave broke the previous record by 5 °C, global warming can’t have much to do with it since that has been only 1 °C over the 20th century”. Here we explain why we find this logic doubly flawed.

One can ask two different questions about the influence of global warming on heat waves (Otto et al. 2012), and we take them in turn.

1. How much hotter did global warming make this heat wave?
[Read more…] about Extremely hot

Filed Under: Climate Science

Data presentation: A trend lesson

23 Mar 2012 by rasmus

I just came across an interesting way to eliminate the impression of a global warming. A trick used to argue that the global warming had stopped, and the simple recipe is as follows:

  • Cut off parts of the measurements and only keep the last 17 years.
  • Plot all the months of these 17 years to get plenty of data points.
  • A good idea is to show a streched plot with longer time axis.
  • [Read more…] about Data presentation: A trend lesson

    Filed Under: Climate Science, Communicating Climate, Instrumental Record, Scientific practice, skeptics

    Updating the CRU and HadCRUT temperature data

    20 Mar 2012 by Gavin

    The latest incarnation of the CRUTEM land surface temperatures and the HadCRUT global temperatures are out this week. This is the 4th version of these products, which have undergone a number of significant changes over that time and so this is a good opportunity to discuss how and why data products evolve and what that means in the bigger scheme of things.

    [Read more…] about Updating the CRU and HadCRUT temperature data

    Filed Under: Climate Science, Instrumental Record

    Sherwood Rowland, CFCs, ozone depletion and the public role of scientists

    13 Mar 2012 by group

    Many of you will have read the obituaries of the Nobel Prize-winning chemist Sherwood Rowland (Nature, BBC) who sadly died over the weekend. DotEarth has a good collection of links to papers, videos and tributes.
    [Read more…] about Sherwood Rowland, CFCs, ozone depletion and the public role of scientists

    Filed Under: Climate Science, Greenhouse gases

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