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Live-blogging the climate science hearings

Filed under: — gavin @ 7 March 2011

I will be live-blogging the House Energy and Commerce committee hearings on climate science with Eli Kintisch. The details are available here, and there should be a live feed from the committee website from 10am.

Eli and I did this last year for the last Democrat-run hearings, and it went quite well – a little like a play-by-play from Eli and some background analysis/cites from me. People can ask questions and comment in real time and depending on how busy it gets, they might get a response.

As usual, this hearing will likely be long on political grandstanding and short on informed discussion, but there might be some gems. Of the witnesses, John Christy and Roger Pielke Sr. are the main witnesses for the majority side, while Richard Somerville, Francis Zwiers and Chris Field are the Dem invitees. There is newcomer to the roster (at least to me), in Knute Nadelhoffer, who presumably will discuss climate change impacts on biological systems (but I don’t really know). There is one out-of-left-field witness, Donald Roberts, who is a serially wrong DDT advocate who is probably there in order to dismiss environmental regulation in general, following the well-worn strategy described in Oreskes and Conway’s “Merchants of Doubt” (Chapter 7 on the revisionist attacks on Rachel Carson) (NB. DDT-related arguments are off topic for this blog, but for background of the specifics of the DDT ‘meme’ see this summary, and interested commenters are encouraged to go to Deltoid).

Anyway, for those who are aficionados of science as contact sport (TM, Steve Schneider), it might be fun.

Update: This was also live-blogged at ClimateCentral and twittered by UCS.

What we do not know in terms of adaptation

Filed under: — rasmus @ 7 March 2011

A recent paper by Oreskes et al. in the journal Philosophy of Science asserts that “there is a gap between the scale on which models produce consistent information and the scale on which humans act”. While the large scales, such as the global mean, provide the best indicators of the state of earth’s climate, it is on the local scales we feel a climate change, such as floods and extreme weather events. Extreme rainfall is usually local. So how is it possible then, as two new papers in Nature by Min et al. and Pall et al. (discussed here) have done, to attribute extreme precipitation and extreme UK floods to climate change?

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Glory (not to) be

Filed under: — gavin @ 4 March 2011

This morning one of the most important (and most delayed) satellite launches in ages took place. The mission was to launch the Glory satellite into a polar orbit, where three key instruments would have been looking at solar irradiance, aerosols and clouds. Unfortunately, one of the stages failed to separate and the satellite did not make orbit.

The irradiance measurements were to be an important continuation of the SORCE mission results, and are needed to stably continue the Total Solar Irradiance (TSI) timeseries. However the big new measurements were those associated with the Aerosol Polarimeter Sensor (APS). A similar instrument has flown in space twice before (the French-developed POLDER instrument), but unfortunately only for short periods. Its uniqueness lies in its ability to detect aerosols over bright surfaces (like land), and more importantly, to distinguish what kind of aerosols it is seeing. (Update: There is a third POLDER instrument, PARASOL, that is currently in orbit, see comments).

It may seem surprising, but despite many different attempts, almost all remote sensing of aerosols from space is only capable of detecting the total optical depth of all aerosols. MISR can provide some discrimination in special cases (picking out dust via a retrieval of non-spherical particles, or using the single scattering albedo to distinguish black carbon), but overall the estimates mix up sulphates, dust, black carbon, sea salt, nitrates and secondary organics. These originate from different processes, have different properties and different impacts on both radiation and clouds. Sea salt comes from sea spray over the oceans, dust from dry desert areas, black carbon from burning of forests and fossil fuels, sulphates derive from ocean plankton and burning coal, nitrates derive from fertiliser use, car exhausts and lightning, and secondary organics come from the stew of volatile organic compounds from industrial and natural sources alike. There are also pollen, and fat particles from outdoor cooking etc.

Because we can’t easily distinguish what’s what from space, we don’t have good global coverage of exactly how much of the aerosol is anthropogenic, and how much is natural. That uncertainty is a big player in the overall uncertainty in the human caused aerosol radiative forcing. Similarly, we have not been able to tell how much of the aerosol is capable of interacting with liquid or ice clouds (which depends on the different aerosols’ affinity for water), and that impacts our assessment of the aerosol indirect effect. These uncertainties are reflected in the model simulations of aerosol concentrations which all show similar total amounts, but have very different partitions among the different types.

The APS technology is a big step forward on these issues. It turns out that while the reflected SW from many different aerosols is similar, the polarisation of that reflected light depends quite strongly on what kind of aerosol it is. This varies depending on the angle at which the light is shining, So by scanning through the angles and measuring the polarisation, we can get a better constraint on the distribution of key aerosols. Scientists have already been working with aircraft mounted versions of the instrument, and this will continue.

The story of how this launch actually happened is very long and twisted, and needless to say, has taken far longer than anyone envisaged at the start (over a decade ago). With the failure to make orbit this morning, the wait will unfortunately go on.

This is of course a huge setback for the mission team (many of whom I know), and I can only imagine how frustrating this must be. The loss of OCO two years ago was due to a similar problem, though 3 launches since then have been successful (and the same system is being replicated as OCO-2). With the postponement of CLARREO in the proposed 2012 budget, there is a huge hole building in the US contribution to Earth and Sun observing systems.

Working from space is hard, expensive and risky. We cannot take it for granted, and yet we need that information more than ever.

Requiem for the Younger Dryas impact hypothesis?

Filed under: — gavin @ 1 March 2011

This is the strong conclusion of a new paper in the Earth Science Reviews by Pinter et al (via Scribd). From their abstract:

The Younger Dryas (YD) impact hypothesis is a recent theory that suggests that a cometary or meteoritic body or bodies hit and/or exploded over North America 12,900 years ago, causing the YD climate episode, extinction of Pleistocene megafauna, demise of the Clovis archaeological culture, and a range of other effects.

The physical evidence interpreted as signatures of an impact event can be separated into two groups. The first group consists of evidence that has been largely rejected by the scientific community and is no longer in widespread discussion…. The second group consists of evidence that has been active in recent research and discussions:…. Over time, however, these signatures have also seen contrary evidence rather than support.

In summary, none of the original YD impact signatures have been subsequently corroborated by independent tests. Of the 12 original lines of evidence, seven have so far proven to be non-reproducible. The remaining signatures instead seem to represent either (1) non-catastrophic mechanisms, and/or (2) terrestrial rather than extraterrestrial or impact-related sources.

The YD impact hypothesis made a big splash at AGU in 2007, and we’ve written about it a few times since. Our assessment was (in 2007), that this would need a lot of confirmatory evidence to get accepted, and even if it was, it did not provide much explanation for other, very similar, abrupt changes in the record. In 2009, we were still skeptical and noted that “the level of proof required for this extraordinary idea will need to be extraordinarily strong”. Unfortunately, as this paper makes clear, neither a lot of confirmatory evidence nor extraordinarily strong proofs have been forthcoming.

This paper is unlikely to the very last word on the subject, but it is likely to be the last time the mainstream paleo-climatologists are going to pay this much heed unless some really big new piece of evidence comes to light.

However, while the specifics of this particular hypothesis and its refutation are interesting in many ways…

The YD impact hypothesis provides a cautionary tale for researchers, the scientific community, the press, and the broader public.

Let’s be specific…
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Unforced variations: Mar 2011

Filed under: — group @ 1 March 2011

This month’s open thread for climate science discussions.


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