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On Mid-latitude Storms

Filed under: — rasmus @ 29 December 2006

Statements often appear in the media about suggesting that more extreme mid-latitude storms will result from global warming. For instance, western Norway was recently battered by an unusually strong storm which triggered many such speculations. But scientific papers on how global warming may affect the mid-latitude storms give a more mixed picture. In a recent paper by Bengtsson & Hodges (2006), simulations with the ECHAM5 Global Climate Model (GCM) were analysed, but they found no increase in the number of mid-latitude storms world-wide. Another study by Leckebusch et al. (2006) showed that the projection of storm characteristics was model-dependent. (Note that the dynamics of tropical and mid-latitude (often called ‘extra-tropical’) storms involve different processes, and tropical storms have been discussed in previous posts here on RC: here, here, here, and here).

The factors that control this are often confounding and so make this a tricky prediction. Simple arguments based on the expected ‘polar amplification‘ and the fact that the surface temperature gradient between the tropics and the poles will likely decrease would reduce the scope for ‘baroclinic instability’ (the main generator of mid-latitudes storms). However, there are also increases in the upper troposphere/lower stratospheric gradients (due to the stratosphere cooling and the troposphere warming) and that has been shown to lead to increases in wind speeds at the surface. And finally, although latent heat release (from condensing water vapour) is not a fundamental driver of mid-latitude storms, it does play a role and that is likely to increase the intensity of the storms since there is generally more water vapour available in warmer world. It should also be clear that for any one locality, a shift in the storm tracks (associated with phenomena like the NAO or the sea ice edge) will often be more of an issue than the overall change in storm statistics.
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2006 Year in review

Filed under: — group @ 27 December 2006 - (Français)

A lighthearted look at the climate science goings-on over the last year:

Best highlight of the gap between the ‘two cultures’:
Justice Scalia: ‘Troposphere, whatever. I told you before I’m not a scientist. That’s why I don’t want to have to deal with global warming’ .

Least effective muzzling of government climate scientist by a junior public affairs political appointee:
George Deutsch met his match in Jim Hansen.

Most puzzling finding that has yet to be replicated:
Methane from plants

Worst reported story and least effectual follow-up press release:
Methane from plants

Best (err… only) climate science documentary on public release:
An Inconvenient Truth.

Most worn out contrarian cliche:
Medieval English vineyards.

Previously prominent contrarian cliche curiously not being used any more:
“The satellites show cooling”

Most bizarre new contrarian claim:
“Global warming stopped in 1998″.
By the same logic, it also stopped in 1973, 1983, and 1990 (only it didn’t).

Most ironic complaint about ‘un-balanced’ climate coverage on CNN:
Pat Michaels (the most interviewed commentator by a factor of two) complaining that he doesn’t get enough exposure.

Most dizzying turn-around of a climate skeptic:
Fred Singer “global warming is not happening” (1998,2000, 2002, 2005) to global warming is “unstoppable” (2006)

Best popular book on the climate change:
Elizabeth Kolbert’s “Field Notes from a Catastrophe

Least unexpected observations:
(Joint winners) 2006 near-record minima in Arctic sea ice extent, near-record maxima in Northern Hemisphere temperatures, resumed increase in ocean heat content, record increases in CO2 emissions

Best resource for future climate model analyses:
PCMDI database of IPCC AR4 simulations. The gift that will keep on giving.

Best actual good news:
Methane concentrations appear to have stabilised. Maybe they can even be coaxed downward….

Biggest increase in uncertainty as a function of more research:
Anything to do with aerosols.

Least apologetic excuse for getting a climate story wrong:
Newsweek explains its 1975 ‘The Cooling World’ story.

Most promising newcomer on the contrarian comedy circuit:
Viscount Monckton of Brenchley

Least accurate attempted insinuation about RealClimate by a congressional staffer:
‘There’s so much money’: Marc Morano (Senate EPW outgoing majority committee staff, 5:30 into the mp3 file)

Boldest impractical policy idea:
Geo-engineering

Boldest practical policy idea:
Creation of a National Climate Service, which could more effecitvely provide useful climate information to policymakers.

Most revealing insight into the disinformation industry (fiction):
Thank you for smoking

Most revealing insight into the disinformation industry (non-fiction) and year’s best self-parody:
‘CO2 is life’

Feel free to suggest your own categories and winners…

AGU Hangover

Filed under: — gavin @ 24 December 2006

It turns out that there were almost 14,000 attendees at AGU last week, which apparently makes it the largest Earth Science meeting ever held. To be sure, not all of that is climate related – there was lots of seismology, planetary and more theoretical/small-scale stuff, but a lot of it was. At most times there were at least half a dozen sessions that I would have been interested to attend – and they were often discussing overlapping themes.

It used to be that one could go to a meeting like this and get a wide overview of the work being done much more efficiently (and speedily) than reading the journals. However, that is clearly no longer true. And of course, we can’t keep up with all the relevant journal articies in the wider field either, and so how do scientists manage?
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Not just ice albedo

Filed under: — rasmus @ 22 December 2006 - (Français)

A recent paper by Francis & Hunter provides an interesting discussion about reasons for the recent decline in the Arctic sea-ice extent, based on new satellite observations. One common proposition about sea ice is that it involves a positive feed-back because the ice affects the planetary albedo (how the planet reflects the sunlight back to space before the energy enters the ‘climate system’). Yet, there is more to the story, as the ice acts more-or-less like an insulating lid on top of the sea. There are subtle effects such as the planet losing more heat from the open sea than from ice-covered region (some of this heat is absorbed by the atmosphere, but climates over ice-covered regions are of more continental winter character: dry and cold). The oceanic heat loss depends of course on the sea surface temperature (SST). Open water also is a source of humidity, as opposed to sea-ice (because its cold, not because its dry), but the atmospheric humidity is also influenced by the moisture transport associated with the wind (moisture advection). Francis & Hunter found a positive correlation between lack of ice and the downward long-wave radiation, something they attributed primarily to cloudiness. Hence, clouds play a role, both in terms of influencing the albedo as well as trapping out-going heat. Francis & Hunter suggest that the changes in the long-wave radiation is stronger than the clouds’ modulation of the direct sunlight.
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Fall AGU

Filed under: — gavin @ 9 December 2006

The Fall AGU meeting in San Francisco is always an exhilarating/exhausting (take your pick) fixture of the Earth Science calendar. This year will be no different, and since about half of us will be there, RealClimate will probably be a little quiet next week. Hopefully, we should be able to report on any highlights when we get back.

N.B. If any readers will be attending and want to say hi, I will be giving a talk on ‘Science blogging: RealClimate.org and the Global Warming debate‘ on Friday (PA53A, 13:40, MCS 309).

Update: AGU went well – lot’s of good stuff. The actual RealClimate presentation is available here – it’s pretty basic though (only 15 minutes worth)).


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